A new blunt-snouted dyrosaurid, Anthracosuchus balrogus gen. et sp. nov. (Crocodylomorpha,Mesoeucrocodylia), from the Palaeocene of Colombia

Alexander K. Hastingsa,b*, Jonathan I. Blocha and Carlos A. Jaramilloc

aFlorida Museum of Natural History, University of Florida, Gainesville, FL, USA; bGeiseltalmuseum, ZentralmagazinNaturwissenschaftlicher Sammlungen, Martin Luther Universitat Halle-Wittenberg, Halle (Saale), Germany; cSmithsonian TropicalResearch Institute, Balboa-Ancon, Panama

(Received 23 March 2014; accepted 24 April 2014)

A new exceptionally brevirostrine dyrosaurid is described from the middle Palaeocene (58–60 million years ago) CerrejonFormation, northeastern Colombia, based on four partial skulls and associated postcrania. This taxon is unique amongdyrosaurids not only in skull shape, but also in having orbital tuberosities, and osteoderms that are dorsoventrally thick andunpitted, a trait otherwise unknown in Crocodylomorpha. Results from a cladistic analysis of Dyrosauridae suggest that thenew taxon, together with Cretaceous–Palaeocene Chenanisuchus lateroculi from Africa and Cerrejonisuchus improcerusalso from the Cerrejon Formation, are the most basal members of the family. Results from a biogeographic analysis indicateat least three independent dispersals of dyrosaurids from Africa to the New World occurred in the Late Cretaceous or earlyPalaeocene. Widely set orbits in the new taxon indicate a deviation from surface-based predation, characteristic of otherdyrosaurids, to sub-surface predation, as in modern Gavialis. Tooth impressions found on turtle shells recovered from thesame locality match well with teeth of the new taxon indicating possible predation.

http://www.zoobank.org/urn:lsid:zoobank.org:pub:AB2B24A5-27CC-4D3F-B580-F11F17851CE6

Keywords: Dyrosauridae; Crocodylomorpha; Palaeocene; Colombia; Cerrejon; biogeography

Introduction

Crocodylomorpha has long been considered a ‘living fossil’

group (McGregor 2005).This largely stems from the fact that

they have displayed conservative morphology in maintain-

ing at least some members within the same body plan as

extant crocodylians since shortly after the group arose (Ross

1989). However, numerous instances of incredibly varied

morphology have evolved time and again within the

crocodylomorph lineage. Forms have varied from slender

terrestrial ancestors (e.g. Sphenosuchus; Walker 1990), to

heavily armoured forms (Armadillosuchus; Marinho and

Carvalho 2009) to fully marine with paddled feet and short

powerful jaws skulls (Dakosaurus; Gasparini et al. 2006).

Most dyrosaurids are thought to have been relatively limited

in ecological diversity, characterised as large near-shore

marine longirostrine piscivores with some variation

associated with juveniles possibly inhabiting freshwater

environments (Jouve, Bardet, et al. 2008). Freshwater

deposits (Jaramillo et al. 2007; Figure 1) of the middle

Palaeocene-aged (58–60 million years ago) Cerrejon

Formation in northeastern Colombia have yielded not only

plant fossils documenting the earliest evidence of a

neotropical rainforest (Wing et al. 2009), but also vertebrate

fossils including side-necked turtles (Cadena et al. 2010;

Cadena, Bloch, et al. 2012; Cadena, Ksepka, et al. 2012), a

giant boid snake (Head et al. 2009a, 2009b) and a diversity of

dyrosaurids that expand our understanding of the ecological

diversity of the group, with a previously published dwarf

species (Cerrejonisuchus improcerus; Hastings et al. 2010)

residing in freshwater habitats in adulthood, and a large-

bodied longirostrine taxon (Acherontisuchus guajiraensis;

Hastings et al. 2011) also in freshwater sediments deposited

in a large river system that drained into what is now the

Caribbean Sea.

Dyrosauridae originated and diversified during the late

Cretaceous, somehow survived the K–P extinction event

that wiped out other large-bodied marine reptiles (Benson

et al. 2010) and ultimately becamemore diverse in the early

Cenozoic (Jouve, Bardet, et al. 2008). The ability of

dyrosaurids to inhabit both marine and fresh water may

have contributed to their preferential survival (Jouve,

Bardet, et al. 2008). Isotopic values for carbon and oxygen

may provide empirical evidence for a freshwater habitat,

supporting this hypothesis (Wheatley 2010). Described

here is a new genus and species of Dyrosauridae with a very

different skull shape relative to other dyrosaurids, likely

reflecting a unique ecology associated with the invasion of

the freshwater ecosystem in tropical South America.

The first skull of this new dyrosaurid (referred

specimen UF/IGM 69) was discovered in 2005, but the

skull was missing its anterior end. Preservation of the

posterior external nares indicated that the individual likely

q 2014 Taylor & Francis

*Corresponding author. Email: alexander.hastings@zns.uni-halle.de

Historical Biology, 2014

http://dx.doi.org/10.1080/08912963.2014.918968

Dow

nloa

ded

by [

Uni

vers

ity o

f Fl

orid

a] a

t 08:

16 2

6 M

ay 2

014

had a short snout. A second skull with the anterior snout

preserved was discovered in early 2007, and indeed this

skull exhibited a very short snout while maintaining other

diagnostic characters of Dyrosauridae. Two more skulls

were discovered later in 2007 bringing the minimum

number of individuals discovered thus far to 4.

All specimens of the new taxon are deposited at the

Museo Geologico Jose Royo y Gomez, Colombian

Geological Survey, Bogota, Colombia. Each specimen

has been assigned a unique number using the abbreviation

UF/IGM. Casts of these specimens are also deposited at

the collections of the Florida Museum of Natural History

(UF).

Institutional abbreviations

IGM, Colombian Geological Survey, Bogota, Colombia;

NJSM, New Jersey State Museum, Trenton, NJ, USA; UF,

University of Florida, Florida Museum of Natural History,

Vertebrate Palaeontology Collection, Gainesville, FL,

USA; USGS SAP, US Geological Survey – Saudi Arabian

collection.

Terminology and anatomical abbreviations

Teeth and alveoli will be referred to by number with 1

being the most anterior. Premaxillary teeth and alveoli will

have the initial ‘pm’, maxillary teeth and alveoli will use

‘m’, and dentary teeth and alveoli will use ‘d’. For

example, the first tooth or alveolus of the premaxilla will

be referred to as ‘pm1’ and the second tooth or alveolus of

the maxilla will be referred to as ‘m2’. These follow the

abbreviations of Hastings et al. (2010).

Systematic palaeontology

Crocodylomorpha Walker, 1970

Crocodyliformes Hay, 1930

Mesoeucrocodylia Whetstone and Whybrow, 1983

Dyrosauridae de Stefano, 1903

Anthracosuchus balrogus gen. et sp. nov.

Etymology. Anthraco-, meaning coal, referring to the coal

mine in which the type locality is located; -suchus,

meaning crocodile. The specific term, balrogus, is named

from a literary beast discovered within a deep mine,

originally written by Tolkien (1954).

Diagnosis. Possesses the following apomorphies: (1) a

snout that is 44–53% of overall skull length; (2) rugose

orbital tuberosities anterior to medial margin of orbits; (3)

osteoderms that are dorsoventrally thick, unpitted and not

imbricated; (4) premaxillae that are wider than long and

(5) external nares that are wider than long.

Further differs from all other dyrosaurids in the

following unique combination of characters: (1) posterior

parietal margin straight; (2) interfenestral bar wide,

contributes to.10% of the skull table width, as measured

at anteroposterior midpoint of supratemporal fenestrae; (3)

8–10 maxillary teeth, of which 5–7 are antorbital; (4)

strong constriction at the premaxilla–maxilla suture; (5)

nasal–prefrontal and nasal–lacrimal sutures subequal in

Figure 1. (Colour online) Locality map and stratigraphiccolumn for locality where all known Anthracosuchus balrogusgen. et sp. nov. fossils are found. (A) Northern South Americawith star indicating Cerrejon fossil locality in northeasternColombia. (B) Stratigraphic column of Cerrejon Formation (fromJaramillo et al. 2007). Fossil locality of Anthracosuchus isunderclay below Coal Seam 90, indicated with arrow above.

2 A. K. Hastings et al.

Dow

nloa

ded

by [

Uni

vers

ity o

f Fl

orid

a] a

t 08:

16 2

6 M

ay 2

014

length; (6) orbits laterally placed and (7) teeth that are

robust, round and weakly striated.

Holotype. UF/IGM 67, nearly complete skull from

premaxilla to occipital condyle (missing medial portion of

pterygoids and ventral braincase), nine ribs, seven

vertebrae and unidentifiable bone.

Paratype. UF/IGM 68, skull from partial premaxilla to

occipital condyle (missing pterygoids and ventral brain-

case), right articular, five osteoderms, five vertebrae, eight

ribs, distal pubis, distal ischium, haemal arch, three

isolated teeth, proximal phalanx, sacral rib and unidentifi-

able bone.

Referred specimens. UF/IGM 69, skull from peri-

orbital snout to posterior parietal (missing all but a

fragment of the pterygoids and the ventral braincase). UF/

IGM 70, skull from premaxilla to quadratic condyles

(missing pterygoids and ventral braincase).

Type locality and horizon. The holotype and all

known specimens of Anthracosuchus balrogus were

recovered from a single stratigraphic layer, broadly

exposed within the Cerrejon coal mine, Guajira Depart-

ment, northeastern Colombia. The fossils were discovered

in the underlying clay layer below Coal Seam 90

(Figure 1). The geologic setting is of fine-grained, grey

clay and mud with fragmented lignite interspersed

throughout (Jaramillo et al. 2007). The geologic setting

is indicative of a large fluvial floodplain, likely supporting

abundant large plant life. The age of the layer is middle-

late Palaeocene, 58–60 million years old (Jaramillo et al.

2007).

Comparative description

General. The rostrum is very stout and short in all

specimens of Anthracosuchus, representing between 44%

and 53% of the total skull length (Table 1). The rostrum of

Anthracosuchus is much shorter than that of any other

known dyrosaurid (Table 1). Cerrejonisuchus and

Chenanisuchus have much more longirostrine skulls

(Jouve, Bouya, et al. 2005; Hastings et al. 2010). The

anterior rostrum of Anthracosuchus is much wider than

that of the other short-snouted dyrosaurids, even in the

case of UF/IGM 68 that has a snout only 2.5% shorter than

Cerrejonisuchus (Hastings et al. 2010). The premaxilla

and external nares of Anthracosuchus are both wider than

long (Figures 2 and 3), a very atypical character for

Dyrosauridae. Even the relatively short-snouted forms of

Cerrejonisuchus and Chenanisuchus have anteroposter-

iorly elongate premaxillae and external nares (Jouve,

Bouya, et al. 2005; Hastings et al. 2010).

The overall shape of the skull is more square than

triangular, which is most apparent in the holotype

(Figure 2) and the paratype (Figure 3). The holotype

skull has experienced dorsoventral compression, but the

overall shape is similar in the uncompressed paratype,

indicating that compression did not significantly alter

these features. The skull table is flat and broad, comprising

most of the posterior half of the skull in dorsal view.

Again, this general feature does not appear to have been

significantly altered by compression due to its presence in

the uncompressed paratype (Figure 3). The wide, large and

flat skull table of Anthracosuchus (Figure 2) is similar to

that of Phosphatosaurus (Buffetaut 1978a), Sokotosuchus

Table 1. Snout proportions of all members of Dyrosauridae with material complete enough for skull length estimation.

DL (cm) PreoL (cm) R (PreoL/DL) £ 100 TBL (m)

Anthracosuchus balrogus (UF/IGM 67) 62 27.5 44.35 4.58Anthracosuchus balrogus (UF/IGM 68) 68 35.5 52.21 5.05Cerrejonisuchus improcerus (UF/IGM 31)a 31.4 17.2 54.78 1.72–2.22Cerrejonisuchus improcerus (UF/IGM 29)a 25.8 15.3 59.30 1.22–1.79Chenanisuchus lateroculib 57.6 36.5 63.37 3.57–4.24Acherontisuchus guajiraensis (UF/IGM 35)c 77.5–86.3 43.2/52.1 55.74–60.37 5.04–6.46Acherontisuchus guajiraensis (UF/IGM 34)c 72.4–78.7 41.9/50.8 57.87–64.52 4.66–5.87Congosaurus bequaerti d 63 41 65.08 3.97–4.66Guarinisuchus munizi e 47.1 30.8 65.41 2.79–3.43H. rogersiib 42.9 28.2 65.73 2.48–3.11Sokotosuchus ianwilsonib 60.1 39.7 66.06 3.75–4.44P. gavialoidesb 107 72 67.29 7.22–8.05Arambourgisuchus khouribgaensisf 100 71.5 71.50 6.71–7.51Dyrosaurus phosphaticusb 104 75 72.12 7.00–7.82Dyrosaurus maghribensisg 89–97 – 73.00 5.89–7.28R. keiniensisb 73.1 53.4 73.05 4.72–5.44Atlantosuchus coupatezih 104.5 83 79.43 7.04–7.86

Notes: DL, dorsal skull length; PreoL, preorbital skull length; R, ratio of preorbital skull length to dorsal skull length; TBL, estimated total body lengthusing method by Sereno et al. (2001). Citations are marked by superscript alphabets: a, Hastings et al. (2010); b, Jouve, Bouya, et al. (2005); c, Hastingset al. (2011); d, an estimation from Jouve and Schwarz (2004); e, an estimation from Figure 2 in Barbosa et al. (2008); f, Jouve, Iarochene, et al. (2005);g, Jouve et al. (2006); h, Jouve, Bouya, et al. (2008).

Historical Biology 3

Dow

nloa

ded

by [

Uni

vers

ity o

f Fl

orid

a] a

t 08:

16 2

6 M

ay 2

014

(Buffetaut 1979), Chenanisuchus (Jouve, Bouya, et al.

2005) and Cerrejonisuchus as opposed to the elongate and

narrow skull table present in Hyposaurinae. The posterior

margin of the skull table in dorsal view is transversally

straight in Anthracosuchus (Figure 2), but highly indented

anteriorly in Rhabdognathus keiniensis (Jouve 2007),

Hyposaurus rogersii (Troxell 1925) and Atlantosuchus

coupatezi (Jouve, Bouya, et al. 2008).

Each of the skulls of Anthracosuchus possesses wide

and rugose tuberosities immediately anterior to the orbits.

These orbital tuberosities are most pronounced in

dorsolateral view in UF/IGM 69 (Figure 4) and appear to

be variable as to whether they are fully on the prefrontal,

lacrimal or split between the two (Figures 2 and 3). The

orbital tuberosities are dorsoventrally short and roughly

conform to the contour of the skull (Figure 4). The rugose

tuberosities near the anteromedial margins of the orbits,

visible in dorsal view (Figure 4), are unusual for

crocodyliforms. The only other known instance of

preorbital tuberosities within Crocodylomorpha is that of

Caryonosuchus pricei from the Late Cretaceous of Brazil,

but these are more akin to small horns (Kellner et al. 2011).

Alligatorids have highly rugose anteromedial orbital

margins, roughly where the palpebral attaches, but this is

not accompanied by surrounding unpitted surfaces as in

Anthracosuchus. These may have been keratinised, but

likely did not support large structures.

Cranial openings. The external nares are wider than

long in dorsal view and completely surrounded by the

premaxillae with lateral margins that are ventral to both

the anterior and posterior margins (Figures 2 and 3). The

external nares of all other dyrosaurids are anteroposter-

iorly elongate in dorsal view. No portion of the incisive

foramen is preserved on any specimen. The orbits of

Anthracosuchus are widely placed from the midline, in a

lateral position (Figures 2–4) like only one other

dyrosaurid, Chenanisuchus lateroculi from the Palaeocene

of Morocco (Jouve, Bouya, et al. 2005). All other

dyrosaurids have much more medially positioned orbits.

The supratemporal fenestrae of Anthracosuchus are very

large, much larger than the orbits and anteroposteriorly

elongate (Figures 2–4). The supratemporal fenestrae are

generally wider in dorsal view (Figures 2 and 4) than in

hyposaurine dyrosaurids, which have much more elongate

fenestrae. The infratemporal fenestrae of Anthracosuchus

are laterally placed, with minimal dorsal exposure and are

bound anteroventrally by the jugals and posterodorsally by

the quadratojugals (Figures 2–4). The infratemporal

Figure 2. (Colour online) Holotype (UF/IGM 67) of Anthracosuchus balrogus gen. et sp. nov. from Cerrejon locality in northeasternColombia, middle-late Palaeocene: (A, B) in dorsal view, (C, D) inventral view and (C) insert displays an in situ tooth in lingual and anteriorviews; scale bar: 1 cm. bf, bone fragment; bo, basioccipital; bsp, basisphenoid; en, external nares; eo, exoccipital; ep, ectopterygoid; f,frontal; j, jugal; l, lacrimal; max,maxilla; m1, 4, 5 and 8,maxillary teeth/alveoli; n, nasal; or t, orbital tuberosity; ost, osteoderm (displaced);o t, occipital tuberosities; p, parietal; pal, palatine; pm2–4, premaxillary teeth/alveoli; pmx, premaxilla; po, postorbital; prf, prefrontal; pt,pterygoid; q, quadrate; qj, quadratojugal; sq, squamosal; stf, supratemporal fenestra; vert, vertebra (displaced). Scale bar: 10 cm.

4 A. K. Hastings et al.

Dow

nloa

ded

by [

Uni

vers

ity o

f Fl

orid

a] a

t 08:

16 2

6 M

ay 2

014

fenestrae are large in hyposaurine dyrosaurids, but more

transversally compressed and laterally placed in Anthra-

cosuchus, which is apparent in the uncompressed UF/IGM

68 (visible in dorsal view, Figure 3). The suborbital

fenestrae of Anthracosuchus are bordered by the palatines

and maxillae and are anteriorly concave in ventral view

(Figures 2–4).

Premaxilla. The premaxillae are wider than long and

completely surround the external nares, excluding the

nasal from contact with the external nares (Figures 2 and

3). All dyrosaurids except Anthracosuchus possess

premaxillae that are longer than wide. Anthracosuchus

instead has wide and stout premaxillae and a constriction

at the premaxilla–maxilla suture that is very pronounced

in both dorsal and ventral views (Figures 2 and 3), as in

Phosphatosaurus (Buffetaut 1978a), and very different

from the gentle curvature seen in hyposaurines such as

Dyrosaurus (Jouve 2005). The premaxilla of Anthraco-

suchus possesses four alveoli, although they are not well

preserved in any specimen (see ventral views of Figures 2

and 3). The third premaxillary tooth is by far the largest,

and the fourth premaxillary tooth appears to be severely

reduced. There is a strong indentation of the lateral margin

at the premaxilla–maxilla suture, noticeable in dorsal and

ventral views (Figures 2 and 3).

Maxilla. The maxilla makes broad contact with the

premaxilla, nasal and lacrimal in Anthracosuchus along its

dorsal snout (Figures 2–4). The maxilla broadly contacts

the palatine on the palatal surface in ventral view

(Figures 2–4). The maxilla of Anthracosuchus comprises

a similar proportion of the snout to other dyrosaurids, even

if its overall shape is very different. Eight maxillary alveoli

are preserved in ventral view of UF/IGM 67 and 68

(Figures 2 and 3). Aventral portion of the posterior maxilla

may be missing in all of the specimens, so a complete

count is not certain (Figures 2–4). The first and third

maxillary alveoli appear to be the largest (Table 2).

The fifth to seventh alveoli are smaller, but the eighth

alveolus appears to be more robust. Even the posteromost

alveoli appear uncompressed and retain the rounded shape

of the anterior alveoli. The tooth count is smaller than

most dyrosaurids. The tooth count of typical dyrosaurids

such as Dyrosaurus maghribensis is 19–21 (Jouve et al.

2006), as opposed to 8 in Anthracosuchus and 11 in

Cerrejonisuchus (Hastings et al. 2010). Most dyrosaurids

have approximately homodont teeth, but the maxilla of

Figure 3. (Colour online) Paratype (UF/IGM 68) of Anthracosuchus balrogus gen. et sp. nov. from Cerrejon locality in northeasternColombia, middle-late Palaeocene: (A, B) skull in dorsal view, (C) associated tooth in lingual view, (D) associated tooth in posterior viewand (E, F) skull in ventral view. bo, basioccipital; en, external nares; eo, exoccipital; eo a, articulation for exoccipital; ep, ectopterygoid; f,frontal; j, jugal; l, lacrimal; max, maxilla; m1–8, maxillary teeth/alveoli; n, nasal; orb, orbit; or t, orbital tuberosity; ot, occipitaltuberosities; p, parietal; pal, palatine; pm2–4, premaxillary teeth/alveoli; pmx, premaxilla; po, postorbital; prf, prefrontal; pt, pterygoid;q, quadrate; qj, quadratojugal; qc, quadratic condyle; sq, squamosal; stf, supratemporal fenestra. Scale bar for A–B and E–F equals10 cm. Scale bar for C–D equals 1 cm.

Historical Biology 5

Dow

nloa

ded

by [

Uni

vers

ity o

f Fl

orid

a] a

t 08:

16 2

6 M

ay 2

014

Anthracosuchus, Cerrejonisuchus and Phosphatosaurus

(Buffetaut 1978a; Hastings et al. 2010) has notably

enlarged third maxillary teeth. In Anthracosuchus, the

maxillary margin is modestly sinuous (nonlinear) in dorsal

view (Figures 2 and 3). The maxilla of Anthracosuchus is

somewhat intermediate in terms of degree to which the

lateral margin undulates, or is ‘festooned’, in dorsal view

(Figures 2 and 3). In hyposaurines, the margin is linear, but

in phosphatosaurines, it is much more sinuous (Buffetaut

1979). Anthracosuchus instead has only a slight expansion

posterior to the premaxilla–maxilla suture.

Nasal. The nasal is variably fused in Anthracosuchus

in dorsal view. The nasals are unfused in UF/IGM 67

and 68 (Figures 2 and 3), but fully fused in UF/IGM 69

(Figure 4). The nasal is fused in most dyrosaurids,

including Dyrosaurus (Jouve 2005), Congosaurus (Jouve

and Schwarz 2004) and adult specimens of Cerrejoni-

suchus. However, Atlantosuchus coupatezi (Jouve,

Bouya, et al. 2008), Rhabdognathus aslerensis (Jouve

2007) and Sokotosuchus ianwilsoni (Buffetaut 1979) all

have unfused nasals. The largest two specimens of

Anthracosuchus have unfused nasals (UF/IGM 67 and

68; Figures 2 and 3), while the smaller UF/IGM 69 has

fully fused nasals (Figure 4), visible in dorsal view. The

bone is broad and medially placed in Anthracosuchus,

expanding from a narrow tip within the premaxilla and

extending posteriorly into a rather straight margin with

the frontal. The nasal does not reach the external nares

in dorsal view.

Lacrimal. The lacrimal forms much of the anterior

margin of the orbit in dorsal view and is anteroposteriorly

thin (Figures 2–4). The lacrimal–prefrontal contact

appears to be greater than the lacrimal–nasal contact.

The length of contact is similar between the prefrontal–

nasal and the lacrimal–nasal sutures. The prefrontal–

nasal suture is longer than the lacrimal–nasal suture in

Figure 4. (Colour online) Referred skull (UF/IGM 69) of Anthracosuchus balrogus gen. et sp. nov. fromCerrejon locality in northeasternColombia, middle-late Palaeocene: (A, B) skull in dorsal view, (C,D) skull in ventral view and (E, F) oblique view of right orbital tuberosity.f, frontal; j, jugal; l, lacrimal; max, maxilla; m2, 5 and 6, maxillary teeth/alveoli; n, nasal; orb, orbit; or t, orbital tuberosity; p, parietal;pal, palatine; pm2 and 3, premaxillary teeth/alveoli; pmx, premaxilla; po, postorbital; prf, prefrontal; sq, squamosal. Scale bar: 10 cm.

6 A. K. Hastings et al.

Dow

nloa

ded

by [

Uni

vers

ity o

f Fl

orid

a] a

t 08:

16 2

6 M

ay 2

014

Dyrosaurus (Jouve et al. 2006), but the reverse is true of

Congosaurus (Jouve and Schwarz 2004). Anthracosuchus

appears to have an intermediate condition with roughly

equal proportions of contact to the nasal, in dorsal view

(Figures 2 and 3).

Prefrontal. The prefrontal contributes largely to the

medial margin of the orbit in dorsal view as well as to the

overall interorbital width in Anthracosuchus (Figures 2–

4). The prefrontal–frontal contact on the dorsal surface is

extensive and penetrates broadly into the frontal, rather

than being slender and reduced. The prefrontal–frontal

contact of Anthracosuchus in dorsal view is much longer

and extensive than the reduced state of most dyrosaurids

such as Congosaurus (Jouve and Schwarz 2004) and

Dyrosaurus (Jouve 2005), and most similar to Chenani-

suchus lateroculi (Jouve, Bouya, et al. 2005). Anthraco-

suchus is also most similar to Chenanisuchus lateroculi in

prefrontal contribution to interorbital width, which is

broad in both taxa.

Jugal. The jugal makes up the lateral margin of

the orbit, visible in dorsal view (Figures 2 and 3). The

postorbital bar is missing or obscured in each of the

specimens. The jugal extends posteriorly to its contact

with the quadratojugal in the posterolateral corner of the

infratemporal fenestra, visible in dorsal view (Figures 2

and 3). The jugal of Anthracosuchus is thicker and more

robust than that of all hyposaurine dyrosaurids (Troxell

1925; Jouve and Schwarz 2004; Jouve 2005, 2007; Jouve,

Iarochene, et al. 2005; Jouve et al. 2006; Jouve, Bouya,

et al. 2008; Barbosa et al. 2008).

Table 2. Measurements of alveoli for Anthracosuchus balrogus gen. et sp. nov.

Left Right

SpecimenAlveolarposition

Anteroposteriorlength

Medeolateralwidth

Alveolarposition

Anteroposteriorlength

Medeolateralwidth

UF/IGM 67 pm1 – – pm1 – –pm2 17.98 18.27 pm2 17.52 18.65pm3 25.92 27.01 pm3 27.58 25.04pm4 – – pm4 – –m1 29.47 32.55 m1 – –m2 – – m2 – –m3 – – m3 – –m4 16.70 26.92 m4 – –m5 – – m5 11.71 11.69m6 – – m6 – –m7 – – m7 – –m8 18.43 – m8 15.41 14.63

UF/IGM 68 pm1 – – pm1 – –pm2 – – pm2 – –pm3 14.49 22.83 pm3 – –pm4 – – pm4 – –m1 – – m1 20.21 19.26m2 – – m2 – –m3 26.19 21.76 m3 – –m4 14.04 12.61 m4 12.88 12.52m5 16.43 15.38 m5 – –m6 – – m6 21.49 20.56m7 – – m7 – –m8 – – m8 – –

UF/IGM 69 pm1 – – pm1 – –pm2 – 13.34 pm2 – –pm3 16.95 25.41 pm3 15.71 17.75pm4 – – pm4 – –m1 – – m1 – –m2 – – m2 – –m3 – – m3 – –m4 – – m4 – –m5 – – m5 – –m6 – – m6 – –m7 – – m7 – –m8 – – m8 – –

Notes: Alveolar walls that were either not preserved at all or not preserved well enough for measurement are denoted with a ‘–’. All measurements are inmillimetres. Abbreviations for the alveoli follow those of Hastings et al. (2010).

Historical Biology 7

Dow

nloa

ded

by [

Uni

vers

ity o

f Fl

orid

a] a

t 08:

16 2

6 M

ay 2

014

Frontal. The frontal is roughly cruciform in dorsal

view, with an anterior projection penetrated by the paired

nasals in UF/IGM 67, slightly penetrated in UF/IGM 68

and with a fairly linear anterior connection to the nasals in

UF/IGM 69 (Figures 2–4). The frontal in most dyrosaurids

comes to a point anteriorly, bifurcating the nasals, which

can be found in Dyrosaurus maghribensis (Jouve et al.

2006) and Congosaurus bequaerti (Jouve and Schwarz

2004). However, Anthracosuchus has nasals that instead

slightly bifurcate the frontal, in dorsal view, at least in the

holotype (Figures 2). Alternatively, in Cerrejonisuchus

improcerus, the nasal terminates along a relatively straight

suture with the frontal, as in UF/IGM 69 (Figure 4). The

frontal contributes to the posteromedial margin of the orbit

and has a broad contact with the prefrontal. The left orbit

of UF/IGM 67 has been slightly modified by compression,

making the prefrontal appear to exclude the frontal from

the orbit (Figure 2), but the better preserved right orbit

shows the same relationship as the other two skulls, and

seems to more accurately reflect the character in

Anthracosuchus. The frontal is slightly ornamented and

forms a broad bar on the lateral side where it joins with the

postorbital on the posterior margin of the orbit. The frontal

contributes to about one-quarter of the overall dorsal

length of the interfenestral bar in UF/IGM 67 (Figure 2)

and closer to one-half in UF/IGM 69 (Figure 4).

Palatine. The palatine extends anteriorly on the palate

in ventral view to the level of the m3 in the holotype (UF/

IGM 67; Figure 2) but only to the m6 in UF/IGM 68

(Figure 3). The suture of UF/IGM 69 appears to reach as

far forward as m2, but the suture is difficult to identify in

this specimen (Figure 4). The palatine forms the wide bar

extending posteriorly from the palate towards the brain-

case and also forms the medial margin of the suborbital

fenestra in ventral view (Figures 2 and 3). The maxilla–

palatine suture occurs at the anteromedial corner of the

suborbital fenestra, with the palatine contributing very

minimally to the anterior margin. The palatine of

Dyrosaurus (Jouve et al. 2006) and Rhabdognathus

(Jouve 2007) meets the maxilla slightly more laterally

than in Anthracosuchus, coming to the anterior point of the

suborbital fenestra. No part of the choanal opening is

preserved in any of the described skulls.

Parietal. The parietal forms the largest contribution to

the skull table in dorsal view, which is ornamented with a

shallow divot on the triangular section between the

supratemporal fenestrae, posterior to the interfenestral bar

(Figures 2 and 3). The parietal contributes between half

and three-quarters to the dorsal length of the interfenestral

bar. The interfenestral bar is square in cross section, with a

slight overhang. The interfenestral bar of dyrosaurids is

typically T shaped and thin, as inDyrosaurus phosphaticus

(Jouve 2005) and Arambourgisuchus khouribgaensis

(Jouve, Iarochene, et al. 2005) or forms a thin sagittal

crest as in R. aslerensis (Jouve 2007). In Anthracosuchus,

Cerrejonisuchus improcerus and Chenanisuchus latero-

culi, the interfenestral bar is much more square shaped and

robust, but still with a bit of an overhanging lip onto the

supratemporal fenestra (Jouve, Bouya, et al. 2005). The

straight posterior parietal margin of Anthracosuchus in

dorsal view (Figures 2–4) is most similar to that of other

dyrosaurids such as Dyrosaurus (Jouve et al. 2006) and

Phosphatosaurus (Buffetaut 1978a), and differs from the

anteriorly indented margins of R. keiniensis (Jouve 2007)

and H. rogersii (Troxell 1925).

Postorbital. The postorbital forms the anterolateral

portion of the supratemporal fenestrae and does not appear

to contact the parietal on the dorsal surface in any of the

specimens (Figures 2–4). The anterolateral process is well

developed in UF/IGM 68 (Figure 3) and UF/IGM 69

(Figure 4), and modest in UF/IGM 67 (Figure 2).

Dyrosaurids typically have well-developed anterolateral

postorbital processes, as in Dyrosaurus phosphaticus

(Jouve 2005) but are reduced in Phosphatosaurus

gavialoides (Buffetaut 1978a) and practically non-existent

in Chenanisuchus lateroculi (Jouve, Bouya, et al. 2005).

The ventral portion of the postorbital is not preserved well

enough in any Anthracosuchus specimen to determine

whether it contacted the infratemporal fenestra anteriorly.

Squamosal. The squamosal forms the posterolateral

portion of the supratemporal fenestrae in dorsal view

(Figures 2–4). The squamosal and postorbital appear to

contribute roughly equally to the lateral bridges of the

skull table. The posterodorsal prong of the squamosal is

most pronounced in UF/IGM 68 and extends posteriorly to

the level of the posterior end of the occipital tuberosities

(Figure 3). However, the other two specimens have much

more reduced posterodorsal squamosal projections

(Figures 2 and 4). The degree of posterior projection of

the squamosals in Anthracosuchus (Figures 2–4) is most

similar to those of Dyrosaurus (Jouve et al. 2006), and not

nearly as pronounced and elongate as R. aslerensis

(Brochu et al. 2002; Jouve 2007).

Pterygoid. The pterygoid is flattened onto the brain-

case of UF/IGM 67, but clearly shows in ventral view a

well-developed wing extending laterally from the midline

(Figure 2). The pterygoidian wing of UF/IGM 67 is broad

and flat (Figure 2), and its relative thickness may be similar

to that of Dyrosaurus maghribensis (Jouve et al. 2006), but

preservation makes it difficult to discern. A fragment of

this wing is also preserved on the ventral surface of UF/

IGM 68 (Figure 3). The suture with the ectopterygoid

forms a distinct, posteriorly directed angle (Figure 2).

Ectopterygoid. The ectopterygoid is firmly sutured to

the pterygoid on the ventral surface and connects this bone

to the maxilla and jugal (Figure 2). The bone forms the

posterolateral portion of the suborbital fenestra in ventral

view. The ectopterygoid of UF/IGM 69 (Figure 4) does not

appear twisted as in Dyrosaurus maghribensis (Jouve et al.

2006) but is instead thick and linear.

8 A. K. Hastings et al.

Dow

nloa

ded

by [

Uni

vers

ity o

f Fl

orid

a] a

t 08:

16 2

6 M

ay 2

014

Exoccipital. The exoccipital has wide lateral expansion

and constitutes much of the posterior surface of the

braincase. Due to oblique deformation of this part of the

skull, it is visible on the dorsal surface of UF/IGM 68

(Figure 3) and to a lesser degree on the ventral surface of

UF/IGM 67 (Figure 2). The exoccipital has a large

contribution of roughly one-third from each side to the

occipital condyle, which can be observed in dorsal view in

UF/IGM 68 (Figure 3). The occipital condyle of UF/IGM

67 is largely obscured in dorsal view and difficult to

discern exoccipital contribution (Figure 2). The exoccipi-

tals of all dyrosaurids contribute largely to the occipital

condyle (Jouve et al. 2006) and that of Anthracosuchus is

no exception. Well-developed, wide and flat occipital

tuberosities extend from the occipital surface, just ventral

to the skull table (Figures 2–4). The occipital tuberosities

are developed to varying degrees within Dyrosauridae.

Anthracosuchus is similar to Chenanisuchus and Sokoto-

suchus in having wide and flat tuberosities (Figure 2), but

differs from Rhabdognathus and Hyposaurus that have

elongate and narrow tuberosities (Jouve, Bouya, et al.

2005).

Basioccipital. The basioccipital forms most of the

wide occipital condyle, as seen in both dorsal and ventral

views (Figures 2–4). It has an oblong, smooth and rounded

surface with a strong ventral lip where the surface recurves

dorsally, best seen in ventral view. The basioccipital of

Anthracosuchus differs from that of Cerrejonisuchus in

being less arched dorsally and lacking the wide flat

anteroventrally directed tuberosity on the ventral surface

(Figure 2). No portion of the basioccipital tubera is

preserved in any specimen.

Basisphenoid. A small portion of the basisphenoid is

preserved in UF/IGM 67, but lacks any part of the

eustachian foramen in ventral view (Figure 2). It is situated

between the pterygoid and the exoccipitals and makes at

least some contact with the basioccipital. The basi-

sphenoid is not well preserved in Anthracosuchus, but does

appear to be mediolaterally narrow in ventral view

(Figure 2) as that of Dyrosaurus maghribensis (Jouve et al.

2006).

Quadratojugal. The quadratojugal reaches the postero-

most portion of the skull in dorsal and ventral views and

contributes at least one-quarter to the craniomandibular

joint (Figures 2 and 3), a similar capacity as Dyrosaurus

maghribensis (Jouve et al. 2006). This bone forms the

posteromedial margin of the infratemporal fenestra, in

dorsal view, and extends anteriorly to the postorbital,

ventral to the skull table (Figures 2 and 3).

Quadrate. The quadrate forms approximately three-

quarters of the craniomandibular condyle as well as much

of the braincase, seen in both dorsal and ventral views of

UF/IGM 67 and 68 (Figures 2 and 3). The quadrate

extends dorsally to at least the squamosal, but possibly the

postorbital in dorsal view (Figures 2 and 3). Quadratic

crests on the ventral surface are understated in

Anthracosuchus, if present at all (Figure 2), much like

that of Cerrejonisuchus improcerus, but differing from the

prominent crest in Arambourgisuchus khouribgaensis

(Jouve, Iarochene, et al. 2005), R. aslerensis (Brochu

et al. 2002) and R. keiniensis (Jouve 2007).

Dentition. The in situ teeth of UF/IGM 67 are wide,

blunt and at least one tooth has a well-preserved carina that

defines the labial and lingual surfaces (Figure 2). The

associated, yet unattached teeth preserved with UF/IGM

68 also have striations and well-developed carinae

(Figure 3). All associated teeth are blunt and low crowned.

The teeth vary in size, but all are roughly circular with

minimal labiolingual compression towards the posterior

alveoli (Figures 2 and 3). The dentition of Anthracosuchus

(Figures 2 and 3) is most similar to that described for

Phosphatosaurus (Buffetaut 1978a) in being round and

blunt, and differs from the elongate recurved teeth typical

of Hyposaurus (Denton et al. 1997), Dyrosaurus (Jouve

et al. 2006) and the anterior dentition of Acherontisuchus.

The teeth of Anthracosuchus are more low crowned and

not spade shaped as in the posterior dentition of

Cerrejonisuchus.

Articular. An isolated articular (but no other portion of

the mandible) was recovered with UF/IGM 68 (Figure 5).

The articular surface where it would fuse with the

surangular is preserved well, but much of the retroarticular

process is missing. Although the surangular is missing, due

to the location of articular–surangular suture marks along

the lateral margin of the articular, the surangular likely did

contribute to the articular surface. The lateral shelf of the

retroarticular process is well developed in dorsal view and

the glenoid fossa is smooth and deeply curved. The lateral

shelf of the retroarticular process forms an L shape in

dyrosaurids (Jouve, Bouya, et al. 2005) and is well

represented in UF/IGM 68 (Figure 5). The anteromedial

wing described for Dyrosaurus maghribensis (Jouve et al.

2006) and Congosaurus bequaerti (Jouve and Schwarz

2004) is also present in Anthracosuchus, although much

more rounded and robust (Figure 5).

Dorsal vertebrae. A total of seven dorsal vertebrae

were preserved with UF/IGM 67 (Figure 6). These appear

to be more or less from a continuous series from dorsal 4 to

dorsal 9, as well as a more posterior vertebra from around

the position of dorsal 16. Even the anteromost of these

vertebrae have fully fused neurocentral sutures, indicating

maturity (sensu Brochu 1996). The neurocentral sutures of

Anthracosuchus were likely straight prior to compression,

as in Hyposaurinae (Schwarz et al. 2006).

The hypapophysis of the dorsal 4 is robust, short and

the vertebra lacks a parapophysis, indicating a transition to

the rib cage (Figure 6). Dorsals 6–9 show clear attachment

points for ribs on the transverse processes, indicating

bifurcated attachment surfaces. The dorsal 4 vertebra of

Anthracosuchus bears a hypapophysis that is roughly half

Historical Biology 9

Dow

nloa

ded

by [

Uni

vers

ity o

f Fl

orid

a] a

t 08:

16 2

6 M

ay 2

014

as high as the vertebral body, as described for

Hyposaurinae (Schwarz et al. 2006). Dorsals 6–9 may

have possessed the ventral keel on the centrum described

for Congosaurus (Schwarz et al. 2006), but preservation

makes this difficult to discern. The transverse processes of

Anthracosuchus dorsals 4 and 6–9 have faintly apparent

parapophyses and diapophyses, making this taxon more

similar to Dyrosaurus, Hyposaurus and Congosaurus than

to cf. Rhabdognathus, which has divergent parapophyses

and diapophyses until dorsal 5 (Schwarz et al. 2006). The

dorsal 16 vertebra shows no articular surface for ribs and

likely represents the lumbar region of the vertebral

column, posterior to the rib cage (Figure 6).

These vertebrae are all wider, larger and more robust

(Figure 6) than any described thus far for Dyrosauridae

(Schwarz et al. 2006). Vertebral series are best known for

Dyrosaurus, but have also been described for Rhabdog-

nathus (Langston 1995) and Congosaurus (Jouve and

Schwarz 2004). The neural spines are more mediolaterally

thick and anteroposteriorly wide than those of other

dyrosaurids, but not nearly as expanded as those of

Sarcosuchus (Sereno et al. 2001). Compression has made

it difficult to tell whether the transverse processes widen

posteriorly as in Hyposaurinae, but they do appear to

lengthen laterally (Schwarz et al. 2006). From what can be

determined from incomplete specimens, the neural spines

do appear to be of similar length, as in Hyposaurinae

(Schwarz et al. 2006).

Caudal vertebrae. Three caudal vertebrae were found

in association with UF/IGM 68 (Figure 6) and represent

positions between Caudal 28 and 32. One of these

specimens has the entire neural spine preserved, which is

very long and anteroposteriorly narrow in lateral view

(Figure 6). The distal tip of the neural spine does not

appear swollen or enlarged relative to the rest of the shaft.

The caudal vertebrae from this section of the tail typically

have a swelling at the distal tip in Dyrosaurus and

Congosaurus, while UF/IGM 68 does not (Figure 6). The

anterior and posterior centra of the caudal vertebrae are

quadrangular in cross section as well as their articular

facets (Figure 6) and appear very similar to those described

for Dyrosaurus and Congosaurus (Schwarz et al. 2006).

Cervical ribs. Two cervical ribs were discovered with

UF/IGM 68 (Figure 7) and represent positions around

articulation with cervicals 4–6. Although compressed, the

widely divergent tuberculum and capitulum, best seen in

medial view (Figure 7), indicate a relatively vertical

position of the cervical ribs in this portion of the neck. The

lateral surface is smooth, with an anterior surface that

likely imbricated with the adjacent anterior cervical rib.

The internal surface of the cervical ribs forms a concave

trough in Anthracosuchus (Figure 6) and in all hyposaurine

dyrosaurids (Schwarz et al. 2006).

Dorsal ribs.Most ribs associated with UF/IGM 67 and

68 are poorly preserved and only represent partial shafts

Figure 5. (Colour online) Associated articular bone of UF/IGM68: (A, B) in medial view, (C, D) in lateral view and (E, F) indorsal view. as sa, articular–surangular surface of articulation;gf, glenoid fossa; lsrap, lateral shelf of retroarticular process; rap,retroarticular process. Scale bar equals 10 cm.

10 A. K. Hastings et al.

Dow

nloa

ded

by [

Uni

vers

ity o

f Fl

orid

a] a

t 08:

16 2

6 M

ay 2

014

with little to no discernible morphology. Two large dorsal

ribs were well preserved with UF/IGM 67 though and are

shown in Figure 7. These are large and robust, much like

the dorsal vertebrae, with thick dorsoventral shafts. These

have clearly distinct tubercula and capitula, indicating

positions around dorsals 7 and 8. The dorsal ribs of

Anthracosuchus (Figure 7) appear more thick and robust

than those figured for either Dyrosaurus or Congosaurus

(Schwarz et al. 2006). Anthracosuchus has dorsoventrally

tall ribs, as in all other described Dyrosauridae, and

both Congosaurus and Anthracosuchus have thickened

distal tips.

Haemal arch. The single-preserved haemal arch

associated with a skull (UF/IGM 68) is from the mid-

caudal section, with a likely position between the 11th and

15th caudal vertebrae (Figure 7). The vertebral attachment

points are split between anterior (13.6mm long) and

posterior facets (9.1mm long), indicating its position in

the tail section. The bone is 73.7mm long, is constricted in

lateral view ventral to the haemal canal (10.5mm wide)

and flares ventrally forming a spatulate shape (max ventral

width of 16.7mm). The haemal arch does not appear to

articulate with any of the three preserved caudal vertebrae.

The left and right articular surfaces do not appear as fully

fused in Anthracosuchus (Figure 7) as in Congosaurus

bequaerti (Jouve and Schwarz 2004) and seem most

similar to the unfused condition described for Rhabdog-

nathus sp. (Langston 1995).

Sacral rib. The second right sacral rib is preserved with

UF/IGM 68 (Figure 8). The iliac surface flares poster-

olaterally and appears to receive an anteroposteriorly

oriented ridge towards the posterior end of the pelvis. UF/

IGM 68 exhibits the roughly hourglass shape in ventral

view (Figure 8) typical of Dyrosauridae (Schwarz et al.

2006). As in Rhabdognathus sp. (USGS SAP 37-CR-1),

the medial surface articulates with the sacral vertebra, but

does not participate in the centrum (Langston 1995).

Ischium. The left distal ischium is preserved with UF/

IGM 68 (Figure 8). The anterior and posterior margins are

well preserved and do not indicate flaring in either

direction, but instead a relatively narrow termination. The

bone is also very dorsoventrally straight, with little to no

curvature laterally. A modest, laterally deflected crest

extends from the anterior distal edge, which is slightly

Figure 6. (Colour online) Vertebrae associated with skulls of Anthracosuchus balrogus gen. et sp. nov. (A, B) Three articulated dorsalvertebrae associated with the skull of UF/IGM 67, likely positions 6 to 8. (C, D) Dorsal vertebra associated with the skull of UF/IGM 67,likely position 16. (E, F) Dorsal vertebra associated with the skull of UF/IGM 67, likely position 4. (G, H) Anterior view of caudalvertebra associated with the skull of UF/IGM 68, likely position 28. (I) Same as (G), but in lateral view. (J) Lateral view of caudal vertebraassociated with the skull of UF/IGM 68, likely position 30. cen, centrum; hyp, hypopophysis; it, isolated tooth; nc, neural canal; ncs,traces of neurocentral suture; ns, neural spine; przy, prezygapophyses; pozy, postzygapophyses; tp, transverse process. Scale bar for A–F:10 cm; scale bar for G–J: 5 cm.

Historical Biology 11

Dow

nloa

ded

by [

Uni

vers

ity o

f Fl

orid

a] a

t 08:

16 2

6 M

ay 2

014

laterally offset from the anterior margin, but then curves

slightly medially to form the anterior edge. The well-

preserved narrow distal end of the ischium of UF/IGM 68

(Figure 8) is consistent with the preserved partial ischium

of Acherontisuchus (Hastings et al. 2011) and interpret-

ations of H. rogersii (Troxell 1925), and less consistent

with Dyrosaurus (Jouve et al. 2006). While known ischia

of Acherontisuchus and Hyposaurus are incomplete, the

distal portion of the ischium of Anthracosuchus is

complete, possessing a more narrow and pointed distal

extremity than the anteroposteriorly long ventral margin of

Dyrosaurus maghribensis (Jouve et al. 2006).

Pubis. The right distal pubis was preserved with UF/

IGM 68 (Figure 8). The entire symphyseal surface that

would have joined the other pubis is preserved and reflects

an angle between the pubes at around 408, narrower thanthat seen in H. rogersii of North America (,508; Troxell1925). However, the overall distal pubic shape is still much

more similar between Anthracosuchus and Cretaceous

Hyposaurus of New Jersey than either is to Palaeocene–

Eocene Dyrosaurus or cf. Rhabdognathus of Africa

(Langston 1995). The pubis of Anthracosuchus is

remarkably flat, with very little arching.

Phalanx. A proximal phalanx was preserved with UF/

IGM 68 (Figure 9), likely pertaining to the pes, due to its

elongate form. The dorsal surface is tubular with a slightly

flattened lateral surface. The ventral (plantar) side has a

wide longitudinal groove along the bone’s centreline. The

articular facet is roughly ovular, with a width of 24.8mm

and height of 15.7mm. The proximal articular surface of

the phalanx of Anthracosuchus (Figure 9) appears more

ovular than does the triangular shape described for

hyposaurine dyrosaurids (Schwarz et al. 2006). The

preserved portion is 57.1mm long and lacks any part of the

distal condyle.

Osteoderms. Five osteoderms were found associated

with the skull of UF/IGM 68. The osteoderms of UF/IGM

68 are very thick and completely unpitted (Figure 10).

Both dorsal and ventral surfaces are smooth, with faint

grooves radiating from the centre, particularly evident

around the edges. The osteoderms swell to the thickest at

the middle and are not curved upward, but are either flat

ventrally or swell ventrally as well as dorsally. None of the

preserved osteoderms have any indication of an imbricat-

ing surface. These osteoderms are very different from any

other published dyrosaurid osteoderms (see Schwarz et al.

2006).

Dyrosaurids typically have thin, slightly dorsally

curved osteoderms with wide shallow pitting. Pitting is

consistent on dorsal, accessory and gastral osteoderms.

Pitting is unlikely to have been lost in Anthracosuchus due

to taphonomic weathering as more subtle features such as

cranial ornamentation were preserved with the same

specimen. Moreover, smaller Cerrejonisuchus osteoderms

from the same locality have been preserved with pitting

intact as well as a more typically dyrosaurid thin cross

section (Hastings et al. 2010). Hyposaurus rogersii is very

typical for a dyrosaurid in this respect and a representative

osteoderm is shown in Figure 10. Osteoderms may be a

little thicker in Congosaurus than other dyrosaurids (Jouve

and Schwarz 2004; Schwarz et al. 2006) but cross-

sectional diagrams of these in Schwarz-Wings et al. (2009)

still appear much thinner than those of Anthracosuchus.

Many dyrosaurid osteoderms are imbricated and have a

Figure 7. (Colour online) Ribs and haemal arch associated withskulls of Anthracosuchus balrogus gen. et sp. nov. (A) Lateralview of dorsal ribs associated with UF/IGM 67, likely positions 7and 8. (B) Medial view of cervical rib associated with UF/IGM68, likely between positions 4 and 6. (C) Same as in (B), in lateralview. (D) Posterior view of haemal arch associated with UF/IGM68, likely positions between 11 and 15. (E) Same as in (D), inlateral view. capm, capitulum; hc, haemal canal; inc ct, incisuracapitulotubercularis (capitulotubercular incision); p art f,posterior articular facet; tubm, tuberculum.

12 A. K. Hastings et al.

Dow

nloa

ded

by [

Uni

vers

ity o

f Fl

orid

a] a

t 08:

16 2

6 M

ay 2

014

thick articular band where one osteoderm overlaps the

next-most posterior one.

The osteoderms of Anthracosuchus are not only

atypical for Dyrosauridae, but they are highly unusual for

Crocodylomorpha, or any armoured vertebrate. Osteo-

derms from all parts of the body are known in most

crocodyliform groups, but none resemble the unpitted and

thickened form seen in Anthracosuchus. Even outside of

Crocodylomorpha, osteoderms are well known in testu-

dines, but are not as square, inflated and untextured as

these (AKH). Osteoderms in sauropods are much more

conical or shaped like a thickened disc, and not rectangular

(Dodson et al. 1998). Somewhat similar forms are seen in

dorsal osteoderms of ankylosaurs (Burns 2008), but not

nearly as square as in UF/IGM 68. Osteoderms in

xenarthrans such as armadillos and glyptodonts have

surface patterns and also have very different overall shapes

(Hill 2006).

Phylogenetic analysis

Relationship to other dyrosaurids

The morphologic data generated by Hastings et al. (2010,

2011) were combined with new data for Anthracosuchus to

better understand the relationships of the Cerrejon taxa

within Dyrosauridae (Table 3). A cladistic analysis was

conducted using branch and bound searches with the

program PAUP version 4.0b10 (Swofford 2003). The data-

set was small enough that branch and bound searches were

practical, while exhaustive searches (which are more

comprehensive) were far too computationally intensive.

The cladistics analysis was rooted with Sarcosuchus

imperator, Elosuchus cherifiensis and Terminonaris

Figure 8. (Colour online) Portions of the pelvis of Anthracosuchus balrogus gen. et sp. nov., UF/IGM 68. (A) Distal left ischium inlateral view. (B) Distal left ischium in posterior view. (C) Distal right pubis in ventral view. (D) Distal right pubis in medial (articular)view. (E) Diagram showing appropriate position of ischium and pubis in ventral view with muscle attachments overlaid, outline indicatesposition in the body. (F) Second right sacral rib in ventral view. (G) Same as (F), in lateral view. ant, anterior; art pub, articular surface forattachment to other pubis bone; f sym il, facies symphysialis ilii (articular surface of the sacral rib with the ilium); gas, gastralia; is,ischium; isc, ischiocaudalis muscle; isp, ischiopubis muscle; ist, ischiotruncus muscle; pub, pubis; pub car, pubic cartilage; r ab, rectusabdominis muscle. Scale bar for A–D and E equals 10 cm; scale bar for F–G equals 5 cm.

Figure 9. (Colour online) Proximal phalanx of Anthracosuchusbalrogus gen. et sp. nov. UF/IGM 68. (A) Dorsal view, (B)plantar view and (C) proximal view. Scale bar for A–B equals5 cm; scale bar for C equals 1 cm.

Historical Biology 13

Dow

nloa

ded

by [

Uni

vers

ity o

f Fl

orid

a] a

t 08:

16 2

6 M

ay 2

014

robusta treated as outgroup taxa. The characters were

ordered as in Hastings et al. (2010, 2011) and multistate

codings were treated as uncertain. For the initial analysis,

we included all 14 ingroup taxa, as in Hastings et al.

(2011), with the addition of the new taxon described in this

study (Table 3).

With all taxa included, the initial results are presented

in a strict consensus cladogram of 44 trees (Figure 11).

This topology is not well resolved, with a large polytomy

including all 15 dyrosaurid species, i.e. the ingroup. Some

resolution was recovered with a monophyletic Rhabdog-

nathus and Dyrosaurus, and a pairing of Sokotosuchus

ianwilsoni and P. gavialoides, but no other relationships

were retained.

The initial results revealed two wildcard taxa,

Congosaurus and Acherontisuchus. These two taxa

were recovered as wildcard taxa in the analysis of

Hastings et al. (2011) as well. An Adams consensus

cladogram placed Acherontisuchus at an unresolved

polytomy at the base of Dyrosauridae with Chenani-

suchus and a monophyletic group including the 13 other

species of Dyrosauridae. Congosaurus placed as sister to

a clade uniting a monophyletic Rhabdognathus and

Atlantosuchus þ Guarinisuchus. The reason for the

unresolved status of these two taxa is that each has

characters that are both derived and primitive and that

there are not enough coded characters to discern which

is more prevalent in the taxon. Acherontisuchus coded

primitively for characters: 1 (snout ,68% of dorsal skull

length), 72 (minimal occlusal pits) and 74 (symphysis

wider than high). This taxon also possessed the derived

state for characters: 23 (linear maxillary margin), 25

(alveolar walls level with maxillary surface) and 71

(mandibular symphysis ends posterior to anterior 3/4

alveoli). This character conflict, combined with only

18.3% of the characters coded for the taxon, resulted in

poor resolution within Dyrosauridae. Acherontisuchus is

known from fragmentary cranial remains and mandibles

(Hastings et al. 2011), and Congosaurus is known only

from the snout section of the skull and not from the

braincase (Jouve and Schwarz 2004). Despite the lack of

material, an approximation of the snout-to-skull length

ratio of Congosaurus was determined from what cranial

material was preserved (Jouve and Schwarz 2004) and

from two nearly complete mandibles of Acherontisuchus

(Hastings et al. 2011) (see values in Table 1).

Congosaurus too possessed primitive and derived

characters. The primitive states were characters: 1

Figure 10. (Colour online) Dyrosaurid osteoderms. (A, C) Dorsal osteoderm, UF/IGM 68, in dorsal view; (B, D) same specimen as (A, C)in ventral view; (E) another dorsal osteoderm, UF/IGM 68, in dorsal view; (F) same specimen as (E), in ventral view; (G) lateral osteoderm,UF/IGM68, in dorsal view; (H) same specimen as G, in ventral view; (I) dorsal osteoderm,UF/IGM68 in dorsal view; (J) same specimen as(I), in ventral view; (K) same specimen as (I), in cross-sectional view at fracture point visible in (I) and (J); (L) osteoderm of H. rogersii,NJSM 12293, in dorsal view; (M) same specimen as (L), in ventral view; (N) Same specimen as (L), in lateral view. Scale bar equals 5 cm.

14 A. K. Hastings et al.

Dow

nloa

ded

by [

Uni

vers

ity o

f Fl

orid

a] a

t 08:

16 2

6 M

ay 2

014

(snout ,68% of dorsal skull length), 3 (thick anterior

margin of external nares) and 14 (absence of lateral

expansion of premaxilla). Congosaurus possessed more

derived characters: 4 (medially positioned orbits), 13

(posterodorsal premaxillary process proximal/anterior to

second alveolus), 22 (premaxilla nearly three times

longer than wide), 23 (linear maxillary margin), 33

(nasal ceases posterior to first maxillary tooth) and 81

(alveoli more widely spaced in posterior versus anterior

snout).

When the two wildcard taxa are removed from the

analysis, the result is a single-most parsimonious

cladogram (Figure 11). This topology shows Chenanisu-

chus lateroculi from Africa as the most primitive

dyrosaurid. The next most basal dyrosaurids are

Anthracosuchus balrogus and Cerrejonisuchus impro-

cerus, respectively. The next most basal clade includes H.

rogersii as the sister taxon to Sokotosuchus ianwilsoni and

P. gavialoides. Arambourgisuchus khouribgaensis is the

sister taxon to a clade that includes a monophyletic

Dyrosaurus, and another nested clade that includes

Atlantosuchus coupatezi þ Guarinisuchus munizi and a

monophyletic Rhabdognathus. For Figure 11, the wildcard

taxa have been given tentative positions based on the

analysis from Hastings et al. (2011), from a 50% majority

rule consensus cladogram where they were placed within

a polytomy with the clade including Atlantosuchus þGuarinisuchus and a monophyletic Rhabdognathus, a

clade also recovered in the current study. As Hyposaurus

was recovered as more primitive than the analysis of

Hastings et al. (2011), it is not presented as part of this

polytomy. Instead, the monophyletic Dyrosaurus is

retained in its position as sister to the clade including

Atlantosuchus þ Guarinisuchus and a monophyletic

Rhabdognathus. The positions of Acherontisuchus and

Congosaurus are denoted with a dashed line to indicate

that they were not part of this particular analysis, but are

included to provide an approximation of where they likely

fit within Dyrosauridae.

Three characters unambiguously support the clade

including all dyrosaurids except the shortest-snouted

genera Chenanisuchus, Anthracosuchus and Cerrejonisu-

chus (characters 7, 8 and 71; see snout proportions in

Table 1). These characters are a narrow interfenestral bar,

an unornamented interfenestral bar and a mandibular

symphysis that ends posterior to the anterior three-quarters

of the alveoli. The pairing of Hyposaurus with

Sokotosuchus and Phosphatosaurus has not been recov-

ered in previous phylogenetic analyses. In this analysis,

the only unambiguous synapomorphy supporting this

clade is character 45, a reversal to state 0, which is the

presence of deep pits on the dorsal surface of the

parietal. Character 47, a pronounced anterolateral

process of the postorbital, unites all dyrosaurids except

Chenanisuchus.Table

3.

Morphologic

characterstates

ofAnthracosuchusbalrogusgen.et

sp.nov.followingthecharactermatrixofHastingset

al.(2010).

Anthracosuchus

balrogusgen.

etsp.nov.

00

00

00

00

01

11

11

11

11

12

22

22

22

22

23

33

33

33

33

34

23

33

33

33

33

34

12

34

56

78

90

12

34

56

78

90

12

34

56

78

90

12

34

56

78

90

90

12

34

56

78

90

11

01

01

00

10

0?

11

??

?1

?1

10

10

0A

11

BB

00

1?

?0

00

10

BB

00

1?

?0

00

10

Anthracosuchus

balrogusgen.

etsp.nov.

44

44

44

44

45

55

55

55

55

56

66

66

66

66

67

77

77

77

77

78

88

12

34

56

78

90

12

34

56

78

90

12

34

56

78

90

12

34

56

78

90

12

?0

1?

20

10

??

?1

2?

??

0?

?1

??

??

??

??

??

??

??

??

?1

?0

??

Notes:Multistate

characters

aretreatedas

uncertain.Fornexusfile,seeElectronic

Supplement.A¼

1/2;B¼

0/1.

Historical Biology 15

Dow

nloa

ded

by [

Uni

vers

ity o

f Fl

orid

a] a

t 08:

16 2

6 M

ay 2

014

Relationship of Dyrosauridae to other crocodyliforms

In many phylogenetic studies of crocodyliforms, long-

irostrine taxa group together despite instances of clear

convergence (Clark 1994). Characters largely tied to

longirostry most often yield a close phylogenetic

relationship (Jouve et al. 2006). A long-standing problem

has been the largely Jurassic-aged thalattosuchians pairing

with the Cretaceous pholidosaurids and Cretaceous–

Eocene dyrosaurids (Jouve et al. 2006; Pol and Gasparini

2009; de Andrade et al. 2011).

The most primitive dyrosaurids in the analysis above

were also the shortest snouted. We carried out an

additional phylogenetic analysis to test the hypothesis

that longirostrine thalattosuchians are much more

primitive within Crocodyliformes than other analyses

suggest and that inclusion of the new brevirostrine

dyrosaurids will result in a more disparate relationship

between Dyrosauridae and Thalattosuchia. This crocodyli-

form analysis utilised a cladistic data-set that included

representatives from all major lineages of Crocodyli-

formes (Jouve et al. 2006) and added to it the new short-

snouted Anthracosuchus balrogus and Cerrejonisuchus

improcerus. The morphological matrix of Jouve et al.

(2006) was chosen because 234 characters were coded

across a large sampling of Crocodyliformes (n ¼ 47) that

included the dyrosaurids Dyrosaurus and Chenanisuchus.

Although more recent studies have also investigated this

problem thoroughly (e.g. Pol and Gasparini 2009; de

Adrade et al. 2011), these studies included only long-

irostrine dyrosaurids, excluding the short-snouted Chena-

nisuchus.

The two Cerrejon dyrosaurids were coded and added to

the matrix (Table 4) that was then run with a heuristic

search with 10,000 repetitions and the random seed

function in PAUP version 4.0b10 (Swofford 2003). The

Figure 11. Cladograms resulting from a phylogenetic analysis of Dyrosauridae. Left cladogram is a strict consensus with all namedspecies known from more than dentary fragments. Right cladogram represents a single cladogram resulting from analysis with the twowildcard taxa removed (Acherontisuchus guajiraensis and Congosaurus bequaerti). In the right cladogram, dotted lines for the wildcardtaxa represent approximate placement based on cladistic analysis of Hastings et al. (2011). The right cladogram is placed in stratigraphicand geographic context. Dates were obtained from Gradstein et al. (2004). CI, consistency index; RI, retention index; RC, rescaledconsistency index; HI, homplasy index.

16 A. K. Hastings et al.

Dow

nloa

ded

by [

Uni

vers

ity o

f Fl

orid

a] a

t 08:

16 2

6 M

ay 2

014

Table

4.

CladisticdataforAnthracosuchusbalrogusgen.et

sp.nov.andCerrejonisuchusimprocerususedin

theanalysisbyJouveet

al.(2006).

11

11

11

11

11

22

22

22

22

22

31

23

45

67

89

01

23

45

67

89

01

23

45

67

89

0Anthracosuchusbalrogus

10

?0

2/3

00

11

30

10

??

??

??

??

??

?1

10

11

3Cerrejonisuchusimprocerus

10

?0

20

01

13

01

10

11

??

??

??

?0

11

01

13

33

33

33

33

34

44

44

44

44

45

55

55

55

55

56

12

34

56

78

90

12

34

56

78

90

12

34

56

78

90

Anthracosuchusbalrogus

01

00

02

00

?0

00

00

12

01

10

11

??

0?

?1

??

Cerrejonisuchusimprocerus

01

00

02

00

?0

00

00

12

01

10

11

??

0?

?1

??

66

66

66

66

67

77

77

77

77

78

88

88

88

88

89

12

34

56

78

90

12

34

56

78

90

12

34

56

78

90

Anthracosuchusbalrogus

?1

10

2?

–0

1?

0?

?0

??

??

0?

??

01

01

01

00

Cerrejonisuchusimprocerus

?1

10

2?

–0

1?

01

?0

??

00

01

0?

01

01

11

00

11

11

11

11

11

11

11

11

11

11

19

99

99

99

99

00

00

00

00

00

11

11

11

11

11

21

23

45

67

89

01

23

45

67

89

01

23

45

67

89

0Anthracosuchusbalrogus

01

?1

1?

?0

?1

0?

?1

??

?1

12

2?

00

00

??

0?

Cerrejonisuchusimprocerus

01

11

10

10

01

0?

?1

0?

?1

11

20

00

00

??

??

11

11

11

11

11

11

11

11

11

11

11

11

11

11

11

22

22

22

22

23

33

33

33

33

34

44

44

44

44

45

12

34

56

78

90

12

34

56

78

90

12

34

56

78

90

Anthracosuchusbalrogus

01

1?

00

10

0?

1?

??

??

??

0?

00

11

??

?1

??

Cerrejonisuchusimprocerus

??

??

??

??

0?

11

??

?2

10

00

00

1?

??

??

?1

11

11

11

11

11

11

11

11

11

11

11

11

11

11

11

55

55

55

55

56

66

66

66

66

67

77

77

77

77

78

12

34

56

78

90

12

34

56

78

90

12

34

56

78

90

Anthracosuchusbalrogus

??

0?

1?

00

??

??

??

??

??

??

??

??

??

??

??

Cerrejonisuchusimprocerus

01

01

1?

??

??

1?

01

??

??

??

?2

??

??

??

??

11

11

11

11

11

11

11

11

11

12

22

22

22

22

22

88

88

88

88

89

99

99

99

99

90

00

00

00

00

01

12

34

56

78

90

12

34

56

78

90

12

34

56

78

90

Anthracosuchusbalrogus

?1

1?

00

0/1

00

10

00

00

00

??

1?

??

??

??

??

1Cerrejonisuchusimprocerus

?1

00

00

10

10

00

00

00

0?

11

??

??

??

??

?1

22

22

22

22

22

22

22

22

22

22

22

22

11

11

11

11

12

22

22

22

22

23

33

33

12

34

56

78

90

12

34

56

78

90

12

34

Anthracosuchusbalrogus

??

??

??

??

??

??

0?

?1

0?

??

1?

??

Cerrejonisuchusimprocerus

??

??

00

??

??

??

0?

?1

1?

??

1?

??

Note:A

totalof234characters

werecoded

andtheother

47taxausedin

thepreviousanalysisremained

unchanged

inthecurrentanalysis.Fornexusfile,seeElectronic

Supplement.

Historical Biology 17

Dow

nloa

ded

by [

Uni

vers

ity o

f Fl

orid

a] a

t 08:

16 2

6 M

ay 2

014

result was 30 equally most parsimonious cladograms

(Figure 12), as opposed to 124 in the heuristic search of

Jouve et al. (2006). The overall results were similar to

those of Jouve et al. (2006). Thalattosuchians shared a

close relationship with dyrosaurids and pholidosaurids. All

four dyrosaurids were monophyletic, although the only

internal resolution had Cerrejonisuchus and Anthracosu-

chus as sister taxa. Despite the short-snouted dyrosaurids

being present in the analysis, the resultant topology

was very similar to other studies addressing the

thalattosuchian issue (e.g. Pol and Gasparini 2009; de

Adrade et al. 2011).

Following Jouve et al. (2006), the same data-set was

used for another heuristic search with 10,000 replicates

with the 15 characters suggested as associated with

longirostry removed (characters 5, 7, 8, 12, 15, 30, 46, 47,

68, 83, 103, 150, 161, 172 and 189). The result of this

analysis was very similar to the heuristic search of Jouve

et al. (2006), with Thalattosuchia having a more basal

position within Crocodyliformes, basal to nearly all of

Mesoeucrocodylia (Figure 12). Pholidosauridae and

Dyrosauridae were united in a node, but different from

the previous analysis in that Elosuchus had an unresolved

relationship in a polytomy including Dyrosauridae and a

clade that includes all other pholidosaurids. Jouve et al.

(2006) found Elosuchus as primitive to both Pholidosaur-

idae and Dyrosauridae. Pol and Gasparini (2009) studied

the correlation between longirostrine characters and the

thalattosuchian phylogenetic issue. They concluded from

their analyses that because these characters are not

uniformly found in longirostrine taxa, they are in fact

informative of the phylogenetic evolution of the taxa. In

the present study, the addition of short-snouted dyrosaurids

did not resolve the problem of convergence driving the

topology between thalattosuchians, dyrosaurids and

pholidosaurids. These results suggest that these convergent

characters are not limited to longirostry and are present

even in non-longirostrine taxa.

Figure 12. Two cladograms from analyses utilising a matrix with representatives across Crocodylomorpha. (A) Strict consensuscladogram resulting from analysis using all 234 characters of Jouve et al. (2006). (B) Strict consensus cladogram resulting from analysisthat omitted the 15 characters associated with longirostry. Note the very different placement of Thalattosuchia with respect toDyrosauridae in the two analyses. CI, consistency index; RI, retention index; RC, rescaled consistency index; HI, homplasy index.

18 A. K. Hastings et al.

Dow

nloa

ded

by [

Uni

vers

ity o

f Fl

orid

a] a

t 08:

16 2

6 M

ay 2

014

Biogeography

In order to discern possible methods of dispersal within

Dyrosauridae, a biogeographic analysis was run on the

dyrosaurid matrix (Table 3) using the program S-DIVA

(Yu et al. 2010a), which utilises a tree file as generated by

PAUP (Swofford 2003). We assigned each taxon to a

region: Africa, North America and South America,

assigned as regions A, B and C, respectively (Figure 13).

The program generates a consensus cladogram from the

tree file, incorporating the biogeographic region of the taxa

included (Yu et al. 2010b). The program generates likely

regions of origin for the ancestors of the taxa included in

the analysis. The program creates a pie chart at each of

these nodes with per cent probability by region for the

ancestor. The program can be set to allow for multiple

regions to be occupied simultaneously.

Four limitations of the software should be kept in

mind. The first is that the program from which it was

derived (DIVA; Ronquist 1996) treats dispersal between

different regions as equally possible, with no preference

for a certain direction or between certain regions

(Kodandaramaiah 2010). The second is that the program

must assign a topology with no polytomies. As a result,

taxa with unresolved relationships in non-biogeographic

studies should be interpreted with caution when using S-

DIVA (Yu et al. 2010b). For this reason, both wildcard

taxa recognised in the earlier analysis were not included.

The third limitation is due to S-DIVA utilising phylogeny

to determine dispersal; taxonomically uninformative

fossils cannot be included. Thus, the present analysis and

discussion are limited to identifiable taxa known from

nearly complete fossil skulls and do not take into account

regions where dyrosaurid fossils were found that could not

be diagnosed to genus. Finally, the program cannot

incorporate temporal data, and timing of dispersal must be

determined using ages of the fossil taxa.

All past phylogenetic studies of Dyrosauridae have

recovered an African origin for the family, and the current

analysis supports this as well. The biogeographic analysis

recovered five optimised dispersal histories, with a

minimum of three dispersal events from Africa to the

New World within Dyrosauridae. The first of these

occurred with the ancestor of Anthracosuchus to South

America (Figure 14). The second dispersal occurred with

the ancestor of Guarinisuchus munizi reaching eastern

Brazil. The third independent trans-Atlantic dispersal

would have been the ancestor ofH. rogersii immigrating to

North America. Had Acherontisuchus guajiraensis been

included, it would likely have represented a fourth

dispersal, as its relationships were most often close to

Arambourgisuchus and Dyrosaurus of Africa and did not

have a direct relationship with Guarinisuchus or any other

Figure 13. Cladogram resulting from biogeographic analysis of Dyrosauridae using the program S-DIVA (Yu et al. 2010a). Solid arrowsindicate dispersal events. The dotted line indicates a possible back dispersal from South America to Africa.

Historical Biology 19

Dow

nloa

ded

by [

Uni

vers

ity o

f Fl

orid

a] a

t 08:

16 2

6 M

ay 2

014

New World dyrosaurid. Most of these dispersal events

would have occurred during the Late Cretaceous. This is

supported by the one Late Cretaceous report of a dyrosaurid

from Colombia, although the six isolated vertebral centra

could only be identified as belonging to Dyrosauridae

(Langston 1965). Congosaurus bequaerti shared a close

relationship with other African taxa in the analysis of

Hastings et al. (2011), and it likely only required dispersal

within Africa to account for its occurrence in Angola. This

interpretation excludes the occurrence of dyrosaurids

known from fragmentary fossils in Asia (e.g. Buffetaut

1978b, 1978c) due to the limitations of the analysis. The

dispersal into central South America is indicated by

Palaeocene fossil occurrences in Bolivia (Buffetaut 1991)

that likely occurred during the Late Cretaceous while a

shallow continental seaway was still present in western

South America (Riccardi 1991; Hoorn et al. 2012).

Discussion

Taxonomy. The new taxon can be referred to Dyrosauridae

based on the following diagnostic characters for the

family, following the diagnosis of Jouve et al. (2006): (1)

lateral margins of external nares lower than anterior or

posterior margins; (2) supratemporal fenestrae at least

twice longer than wide; (3) occipital tuberosities present,

directed posteriorly and formed by exoccipitals; (4)

exoccipitals participate greatly in occipital condyle; (5)

neural spines extremely elongate dorsally in caudal

vertebrae; (6) dorsal margin of neural spines narrow, not

thickened; (7) caudal centra quadrangular in cross section;

(8) haemal arches extremely elongate ventrally. For a list

of characters discerning Anthracosuchus from all other

dyrosaurid diagnoses, see Electronic Supplement.

Palaeobiology. The orbits of Anthracosuchus are very

widely spaced for Dyrosauridae (Figures 2–4). Typical

dyrosaurids (e.g. Dyrosaurus, Rhabdognathus and Hypo-

saurus) have centrally placed orbits, close to the midline of

the skull (Jouve, Bouya, et al. 2005). The only other

dyrosaurid with widely set orbits is Chenanisuchus (Jouve,

Bouya, et al. 2005). The only extant crocodylian with

notably wide-set orbits is Gavialis gangeticus. A bivariate

plot of width of skull measured at orbits and interorbital

Figure 14. (Colour online) Map showing dispersal pattern andtiming for Dyrosauridae. Map is of the Late Cretaceous, colourisedfromScotese (2001). There are at least three independent dispersalsfrom Africa to the New World (see text for explanation).

Figure 15. (Colour online) Bivariate plot with natural log transform of skull width as measured at orbit (x-axis) and interorbital width ofdyrosaurids and extant crocodylians.

20 A. K. Hastings et al.

Dow

nloa

ded

by [

Uni

vers

ity o

f Fl

orid

a] a

t 08:

16 2

6 M

ay 2

014

width (with natural log transform) revealed that Anthra-

cosuchus had greater similarity in terms of orbital spacing

with Gavialis than with typical dyrosaurids, Alligator

mississippiensis, Caiman crocodilus or Crocodylus nilo-

ticus (Figure 15). Extant Gavialis typically acquire their

prey, almost exclusively fish, below the water surface

(Thorbjarnarson 1990; Grenard 1991). The three extant

species with more narrowly placed orbits more commonly

acquire prey from a position at the surface of the water

(Grenard 1991; Thorbjarnarson 1993). More widely set

orbits may be tied to a non-surficial prey acquisition

feeding strategy and likely indicate a deviation by

Anthracosuchus and Chenanisuchus from the typical

behaviour of dyrosaurids. This subsurface predation

method may also be inferred in the highly marine

metriorhynchid crocodyliforms, which have laterally

placed orbits (Pol and Gasparini 2009).

The distal pubis is rarely recovered for New World

dyrosaurids, with the only other figured specimen from H.

rogersii from the Late Cretaceous marine deposits of New

Jersey (Troxell 1925). Both have a more elongate suture

between left and right pubes as compared to extant

crocodylians. That of Anthracosuchus (Figure 8) is

proportionally longer than that of H. rogersii. The pubic

cartilage attaches to the anterior portions of these bones in

extant crocodylians, and the symphyseal region is where

the ischiopubis and ischiotruncus muscles attach (Uriona

and Farmer 2008; Schwarz-Wings et al. 2009). A non-

enlarged distal ischium, also preserved with UF/IGM 68,

indicates highly reduced attachment surfaces for the

ischiopubis, ischiotruncus and ischiocaudalis muscles

(Figure 8). The ischiopubis muscle in particular is used

primarily in buoyancy control (Uriona and Farmer 2008).

Much like the implications for Acherontisuchus (Hastings

et al. 2011), it would appear Anthracosuchus also relied

less on these muscles for pitch control within the water.

The pubis is heavily utilised in extant crocodylian

respiration and the bone is pulled ventrally and rotated

slightly by the rectus abdominus and diaphragmaticus

muscles, bringing air into the lungs (Claessons 2004). The

pubic cartilage is what dominantly attaches these two bones

in extant crocodylians (Uriona andFarmer 2008). The longer

and more rigid suture marks in Anthracosuchus may have

reduced the flexibility of this joint, but provided a firmer

basis from which to depress the pubes and take in air. This

firmer suture may have also meant that Anthracosuchuswas

less capable of pubic rotation as in extant crocodylians

(Claessons 2004). The Eocene Dyrosaurus maghribensis of

Morocco possessed a pubis that is spatulate and much more

similar to that of extant crocodylia (Jouve et al. 2006).

The preserved ribs of Anthracosuchus indicate similar

vertical positions for muscle attachments, as indicated for

Hyposaurinae (Schwarz-Wings et al. 2009) and Acheronti-

suchus (Hastings et al. 2011). The resultant angle for axial

muscles was found to imply dyrosaurids likely swam in a

much more undulating fashion than extant crocodylians,

which are nearly entirely tail-based swimmers (MacDonald

2005; Schwarz-Wings et al. 2009). The osteoderms of

hyposaurine dyrosaurids are known to imbricate dorsally,

providing bracing for the vertebral column.

Osteoderms are not as extensive along the lateral

portion of the dyrosaurid body as in some extant

crocodylians, likely affording dyrosaurids greater flexi-

bility at the sacrifice of reduced stability and armoured

Figure 16. (Colour online) Portions of pelomedosoid turtlecarapace,UF/IGM71,with crocodyliformbitemarks. (A,C)Costalfragment in dorsal view; (B, D) same fragment in ventral view; (E,G) neural fragment in dorsal view; (F, H) peripheral in dorsal view;(I, K) m1 tooth from holotype of Anthracosuchus balrogus gen. etsp. nov., UF/IGM67, placedwithin the impact shell scar featured in(I); (J, L) peripheral indorsal view. bm, bitemark; bm?, possible bitemark; bm&p, bite mark and regrown bone plug; dm, drag marks;m1, first maxillary tooth; pr, proximal rib. Scale bar for A–H, J andL equals 5 cm; scale bar for I and K equals 1 cm.

Historical Biology 21

Dow

nloa

ded

by [

Uni

vers

ity o

f Fl

orid

a] a

t 08:

16 2

6 M

ay 2

014

protection. This flexibility would have been necessary for

the more undulating locomotion of dyrosaurids (Schwarz-

Wings et al. 2009). The osteoderms of Anthracosuchus

likely did not imbricate at all, implying an even greater

degree of flexibility, at the sacrifice of reduced stability,

particularly for rostroterminal torsion.

Pitting in osteoderms has been associated with thermal

regulation in extant crocodyliforms, with the increased

surface area and veination allowing a greater amount of

heat transfer to take place along the animal’s broadly

exposed dorsal surface (Seidel 1979). Bones of the skull

that are unpitted are separated from the dermis by muscle,

as opposed to pitted surfaces that are very near to the

dermis (Seidel 1979). The osteoderms of Anthracosuchus

are unpitted and likely resided deeper in the dorsal

musculature than in extant crocodylians, and were likely

not utilised as much for thermoregulation. The small

rivulets and thin crevices radiating from the centre of the

dorsal surface are instead likely indicative of keratinisa-

tion, which has been proposed for similar features on the

cranium as a display feature in the extinct crocodyliform

Aegisuchus (Holliday and Gardner 2012).

Diet. The teeth of Anthracosuchus are blunt and robust,

which may be indicative of a durophagous diet with a

strong crushing bite (Massare 1987). A large turtle shell

(UF/IGM 71) has preserved several dents, scores and

scratch marks on dorsal and ventral surfaces that resemble

predation attempts by a crocodyliform (Noto et al. 2012).

There are straight puncture marks, tooth slide marks and at

least one rehealed puncture mark (Figure 16). The largest

of these puncture marks fits very well with the largest

preserved tooth (m1) of UF/IGM 67 (Figure 2).

Acknowledgements

Many thanks to L. Teicher, F. Chavez, G. Hernandez, C. Montesand the rest of the crew at the Cerrejon coal mine for access to thesite and housing during field work. Thanks to Ecopetrol S.A.-ICPfor logistic support. Thanks to H. Garcia, A. Rincon, E. Cadena,F. Herrera, S. Wing and M. Ramirez for help collecting fossils atCerrejon. J. Bourque provided useful guidance for specimenpreparation and conservation. Thanks to E. Whiting for takingadditional measurements during manuscript revision. Thanks toR. Pellegrini for access to and assistance with the collections at theNJSM. Thanks to J. Head for assistance and guidance during thedevelopment of this manuscript. Lastly, thanks to the ColombianGeological Survey (SGC) in Bogota, Colombia, for access tospecimens and facilitating ongoing research of the remarkablevertebrate fossils of the Palaeocene–Eocene of Colombia.

Funding

Funding for research and fieldwork was made possible by theNational Science Foundation [grant numbers DEB-0733725 andDSGC 640179], funds from the Florida Museum of NaturalHistory, the Smithsonian Tropical Research Institute Paleobiol-ogy Fund, the Geological Society of America Graduate StudentResearch Grant, the R. Jerry Britt, Jr Paleobiology Award

(Florida Museum of Natural History), Gary S. Morgan StudentResearch Award and the Cerrejon Coal mine.

References

Barbosa JA, Kellner WA, Viana MSS. 2008. New dyrosauridcrocodylomorph and evidences for faunal turnover at the K–Ptransition in Brazil. Proc R Soc B. 275(1641):1385–1391.

Benson RBJ, Butler RJ, Lindgren J, Smith AS. 2010. Mesozoic marinetetrapod diversity: mass extinctions and temporal heterogeneity ingeological megabiases affecting vertebrates. Proc R Soc B. 277(1683):829–834.

Brochu CA. 1996. Closure of neurocentral sutures during crocodilianontogeny: implications for maturity assessment in fossil archosaurs.J Vert Paleontol. 16(1):49–62.

Brochu CA, Bouare ML, Sissoko F, Roberts EM, O’Leary MA. 2002.A dyrosaurid crocodyliform braincase from Mali. J Paleontol. 76(6):1060–1071.

Buffetaut E. 1978a. Les Dyrosauridae (Crocodylia, Mesosuchia) desphosphates de l’Eocene inferieur de Tunisie: Dyrosaurus, Rhabdog-nathus, Phosphatosaurus. Geol Mediter. 5(2):237–256.

Buffetaut E. 1978b. A dyrosaurid (Crocodilia, Mesosuchia) from theupper Eocene of Burma. Neues Jahrb Geol Palaontol Monatshefte.5:273–281.

Buffetaut E. 1978c. Crocodilian remains from the Eocene of Pakistan.Neues Jahrb Geol Palaontol Abh. 156:262–283.

Buffetaut E. 1979. Sokotosuchus ianwilsoni and the evolution of thedyrosaurid crocodiles. Niger Field Monogr. 1(6):31–41.

Buffetaut E. 1991. Fossil crocodilians from Tiupampa, (Santa LuciaFormation, Early Paleocene) Bolivia: a preliminary report. Rev TecYacim Pet Fisc Boliv. 12(3–4):541–544.

Burns ME. 2000. Taxonomic utility of ankylosaur (Dinosauria,Ornithischia) osteoderms: Glyptodontopelta mimus Ford, 2000: atest case. J Vert Paleontol. 28(4):1102–1109.

Cadena E, Bloch JI, Jaramillo C. 2010. New podocnemidid turtle(Testudines: Pleurodira) from the middle-upper Paleocene of SouthAmerica. J Vert Paleontol. 30(2):367–382.

Cadena EA, Bloch JI, Jaramillo C. 2012. New bothremydid turtle(Testudines, Pleurodira) from the Paleocene of NortheasternColombia. J Paleontol. 86(4):689–699.

Cadena EA, Ksepka DT, Jaramillo CA, Bloch JI. 2012. Newpelomedusoid turtles from the late Palaeocene Cerrejon Formationof Colombia and implications for phylogeny and body size evolution.J Syst Palaeontol. 10(2):313–331.

Claessons LPAM. 2004. Archosaurian respiration and the pelvic girdleaspiration breathing of crocodyliforms. Proc R Soc Lond B.271(1547):1461–1465.

Clark JM. 1994. Patterns of evolution in Mesozoic Crocodyliformes.In: In the shadow of the dinosaurs. New York, NY: CambridgeUniversity Press; p. 84–97.

de Andrade MB, Edmonds R, Benton MJ, Schouten R. 2011. A newBerriasian species of Goniopholis (Mesoeucrocodylia, Neosuchia)from England, and a review of the genus. Zool J Linn Soc. 163(s1):S66–S108.

de Stefano G. 1903. Nuovi rettili degli strati a fosfato della Tunisia. BollSoc Geol Ital. 22(1):51–80.

Denton RK, Dobie JL, Parris DC. 1997. The marine crocodilianHyposaurus in North America. In: Ancient marine reptiles.New York, NY: Academic Press; p. 375–397.

Dodson PD, Krause W, Forster CA, Sampson SD, Ravoavy F. 1998.Titanosaurid (Sauropoda) osteoderms from the Late Cretaceous ofMadagascar. J Vert Paleontol. 18(3):563–568.

Gasparini Z, Pol D, Spalletti LA. 2006. An unusual marine crocodyliformfrom the Jurassic–Cretaceous boundary of Patagonia. Science.311(70):70–73.

Gradstein F, Ogg J, Smith A. 2004. A geologic time scale 2004.Cambridge: Cambridge University Press.

Grenard S. 1991. Handbook of alligators and crocodiles. Malabar, FL:Krieger Publishing Company.

Hastings AK, Bloch JI, Jaramillo CA. 2011. A new longirostrinedyrosaurid (Crocodylomorpha, Mesoeucrocodylia) from the Paleo-

22 A. K. Hastings et al.

Dow

nloa

ded

by [

Uni

vers

ity o

f Fl

orid

a] a

t 08:

16 2

6 M

ay 2

014

cene of north-eastern Colombia: biogeographic and behaviouralimplications for new-world Dyrosauridae. Palaeontology. 54(5):1095–1116.

Hastings AK, Bloch JI, Cadena EA, Jaramillo CA. 2010. A new smallshort-snouted dyrosaurid (Crocodylomorpha, Mesoeucrocodylia)from the Paleocene of Northeastern Colombia. J Vert Paleontol.30(1):139–162.

Hay OP. 1930. Second bibliography and catalogue of the fossil Vertebrataof North America. Vol. 2. Carnegie Inst Washington Publ.390:1–1074.

Head JJ, Bloch JI, Hastings AK, Bourque JR, Cadena EA, Herrera FA,Polly PD, Jaramillo CA. 2009a. Giant boid snake from the Paleoceneneotropics reveals hotter past equatorial temperatures. Nature.457:715–717.

Head JJ, Bloch JI, Hastings AK, Bourque JR, Cadena EA, Herrera FA,Polly PD, Jaramillo CA. 2009b. Brief communication arising (reply).Nature. 460:E4–E5.

Hill RV. 2006. Comparative anatomy and histology of xenarthranosteoderms. J Morphol. 267(12):1441–1460.

Holliday CM, Gardner NM. 2012. A new eusuchian crocodyliform withnovel cranial integument and its significance for the origin andevolution of Crocodylia. PLoS ONE. 7:e30471.

Hoorn C, Wesselingh FP, ter Steege H, Bermudez MA, Mora A, Sevink J,Sanmartın I, Sanchez-Meseguer, Anderson CL, Figueirido JP. 2012.Amazonia through time: andean uplift, climate change, landscapeevolution, and biodiversity. Science. 330(927):927–931.

Jaramillo C, Pardo-Trujillo A, Rueda M, Harrington G, Bayona G, TorresV, Mora G. 2007. Palynology of the Upper Paleocene CerrejonFormation. North Colombia Palynol. 31(1):153–189.

Jouve S. 2005. A new description of Dyrosaurus phosphaticus (Thomas,1893) (Mesoeucrocodylia: Dyrosauridae) from the Lower Eocene ofNorth Africa. Can J Earth Sci. 42(3):323–337.

Jouve S. 2007. Taxonomic revision of the dyrosaurid assemblage(Crocodyliformes: Mesoeucrocodylia) from the Paleocene of theIullemmeden Basin, West Africa. J Paleontol. 81(1):163–175.

Jouve S, Bardet N, Jalil N-E, Suberbiola X, Bouya B, AmaghzazM. 2008.The oldest African crocodylian: phylogeny, paleobiogeography, anddifferential survivorship of marine reptiles through the Cretaceous-Tertiary boundary. J Vert Paleontol. 28(2):409–421.

Jouve S, Bouya B, Amaghzaz M. 2005. A short-snouted dyrosaurid(Crocodyliformes, Mesoeucrocodylia) from the Palaeocene ofMorocco. Palaeontolgy. 48(2):359–369.

Jouve S, Bouya B, Amaghzaz M. 2008. A long-snouted dyrosaurid(Crocodyliformes, Mesoeucrocodylia) from the Paleocene ofMorocco: phylogenetic and palaeobiogeographic implications.Palaeontology. 51(2):281–294.

Jouve S, Iarochene M, Bouya B, Amaghzaz M. 2005. A newcrocodyliform dyrosaurid from the Palaeocene of Morocco and aphylogenetic analysis of Dyrosauridae. Acta Palaeontol Pol. 50(3):581–594.

Jouve S, Iarochene M, Bouya B, Amaghzaz M. 2006. A new species ofDyrosaurus (Crocodylomorpha, Dyrosauridae) from the earlyEocene of Morocco: phylogenetic implications. Zool J Linn Soc.148(4):603–656.

Jouve S, Schwarz D. 2004. Congosaurus bequaerti, a Paleocenedyrosaurid (Crocodyliformes; Mesoeucrocodylia) from Landana(Angola). Bull Inst R Sci Nat Belg Sci Terre. 74:129–146.

Kellner AWA, Campos DA, Riff D, de Andrade MB. 2011. A newcrocodylomorph (Sphagesauridae, Notosuchia) with horn-liketubercles from Brazil. Zool J Linn Soc. 163(s1):S57–S65.

Kodandaramaiah U. 2010. Use of dispersal-vicariance analysis inbiogeography – a critique. J Biogeogr. 37(1):3–11.

LangstonWL. 1965. Fossil crocodilians from Colombia and the Cenozoichistory of the Crocodilia in South America. U Calif Publ Geol Sci.52:1–168.

Langston WL. 1995. Dyrosaurs (Crocodilia, Mesosuchia) from thePaleocene Umm Himar Formation, Kingdom of Saudi Arabia. USGeol Surv Bull. 2093:F1–F36.

MacDonald S. 2005. Activation of the axial muscles during aquaticlocomotion in the estuarine crocodile (Crocodylus porosus) [honoursthesis]. Brisbane: University of Queensland.

Marinho TS, Carvalho IS. 2009. An armadillo-like sphagesauridcrocodyliform from the Late Cretaceous of Brazil. J S Am EarthSci. 27(2009):36–41.

Massare JA. 1987. Tooth morphology and prey preference of Mesozoicmarine reptiles. J Vert Paleontol. 7(2):121–137.

McGregor J. 2005. Crocodile crimes: people versus wildlife and thepolitics of postcolonial conservation on Lake Kariba. Zimbabwe.Geoforum. 36(2005):353–369.

Noto CR, Main DJ, Drumheller SK. 2012. Feeding traces andpaleobiology of a Cretaceous (Cenomanian) crocodyliform: examplefrom the Woodbine Formation of Texas. Palaios. 27(2):105–115.

Pol D, Gasparini Z. 2009. Skull Anatomy of Dakosaurus andiniensis(Thalattosuchia: Crocodylomorpha) and the phylogentic position ofThalattosuchia. J Syst Palaeontol. 7:165–197.

Riccardi AC. 1991. Jurassic and Cretaceous marine connections betweenthe Southeast Pacific and Tethys. Palaeogeogr Palaeoecol.87:155–189.

Ronquist F. 1996. DIVA, version 1.1. Computer program and manualavailable by anonymous FTP from Uppsala University, Uppsala,Sweden. Available at: ftp.uu.se or ftp.systbot.uu.se.

Ross CA. 1989. Crocodiles and alligators. New York, NY: Facts on File.Schwarz D, Frey E, Martin T. 2006. The postcranial skeleton of the

Hyposaurinae (Dyrosauridae; Crocodyliformes). Palaeontology.49(4):695–718.

Schwarz-Wings D, Frey E, Martin T. 2009. Reconstruction of the bracingsystem of the trunk and tail in hyposaurine dyrosaurids(Crocodylomorpha; Mesoeucrocodylia). J Vert Paleontol. 29(2):453–472.

Scotese CR. 2001. Digital paleogeographic map archive on CD-ROM.Arlington, TX: PALEOMAP Project.

Seidel MR. 1979. The osteoderms of the American Alligator and theirfunctional significance. Herpetologica. 35(4):375–380.

Sereno PC, Larsson HC, Sidor CA, Gado B. 2001. The giantcrocodyliform Sarcosuchus from the Cretaceous of Africa. Science.294(5546):1516–1519.

Swofford D. 2003. PAUP* 4.0b10. Sunderland, MA: Sinauer Associates.Thorbjarnarson JB. 1990. Notes on the feeding behavior of the gharial

(Gavialis gangeticus) under semi-natural conditions. J Herpetol.24(1):99–100.

Thorbjarnarson JB. 1993. Fishing behavior of spectacled caiman in theVenezuelan Llanos. Copeia. 1993(4):1166–1171.

Troxell EL. 1925. Hyposaurus, a marine crocodilian. Am J Sci Ser 5.9(54):489–514.

Tolkien JRR. 1954. The fellowship of the ring. London: Unwin Books.Uriona TJ, Farmer CG. 2008. Recruitment of the diaphragmaticus,

ischiopubis and other respiratory muscles to control pitch and roll inthe American alligator (Alligator mississippiensis). J Exp Biol.211(7):1141–1147.

Walker AD. 1970. A revision of the Jurassic reptile Hallopus victor(Marsh), with remarks on the classification of crocodiles. PhilosTrans R Soc Lond Biol Sci. 257(816):323–372.

Walker AD. 1990. A revision of Sphenosuchus acutus Haughton,a crocodylomorph reptile from the Elliot Formation (Late Triassic orEarly Jurassic) of South Africa. Philos Trans R Soc Lond Biol Sci.330(1256):1–120.

Wheatley PV. 2010. Understanding saltwater tolerance and marineresource use in the Crocodylia: a stable isotope approach[dissertation]. Santa Cruz, CA: University of California.

Whetstone KN, Whybrow PJ. 1983. A ‘cursorial’ crocodilian from theTriassic of Lesotho (Basutoland), southern Africa. Occas Pap UnivKans Mus Nat Hist. 106:1–37.

Wing S, Herrera F, Jaramillo C, Gomez-Navarro C,Wilf P, Labandeira C.2009. Late Paleocene fossils from the Cerrejon Formation,Colombia, are the earliest record of Neotropical rainforest. ProcNatl Acad Sci. 106(44):18627–18632.

Yu Y, Harris AJ, He XJ. 2010a. S-DIVA (Statistical Dispersal–Vicariance Analysis) 1.5. Accessed from http://mnh.scu.edu.cn/soft/blog/sdiva on September 2, 2011.

Yu Y, Harris AJ, He XJ. 2010b. S-DIVA (statistical dispersal-vicarianceanalysis): a tool for inferring biogeographic histories. MolPhylogenet Evol. 56(2):848–850.

Historical Biology 23

Dow

nloa

ded

by [

Uni

vers

ity o

f Fl

orid

a] a

t 08:

16 2

6 M

ay 2

014