1 23

ZoomorphologyEvolutionary, Comparative andFunctional Morphology ISSN 0720-213XVolume 134Number 2 Zoomorphology (2015) 134:325-338DOI 10.1007/s00435-015-0255-x

Dental anomalies in pinnipeds (Carnivora:Otariidae and Phocidae): occurrence andevolutionary implications

César Jaeger Drehmer, Daniela Sanfelice& Carolina Loch

1 23

Your article is protected by copyright and

all rights are held exclusively by Springer-

Verlag Berlin Heidelberg. This e-offprint is

for personal use only and shall not be self-

archived in electronic repositories. If you wish

to self-archive your article, please use the

accepted manuscript version for posting on

your own website. You may further deposit

the accepted manuscript version in any

repository, provided it is only made publicly

available 12 months after official publication

or later and provided acknowledgement is

given to the original source of publication

and a link is inserted to the published article

on Springer's website. The link must be

accompanied by the following text: "The final

publication is available at link.springer.com”.

ORIGINAL PAPER

Dental anomalies in pinnipeds (Carnivora: Otariidaeand Phocidae): occurrence and evolutionary implications

Cesar Jaeger Drehmer • Daniela Sanfelice •

Carolina Loch

Received: 17 September 2014 / Revised: 18 January 2015 / Accepted: 23 January 2015 / Published online: 13 February 2015

� Springer-Verlag Berlin Heidelberg 2015

Abstract Dental anomalies comprise variations in num-

ber, shape, size, position and occlusion of teeth, mainly

caused by genetic mechanisms. This study aimed to in-

vestigate the nature and prevalence of dental anomalies in a

large sample of pinnipeds (Otariidae and Phocidae) and to

discuss potential evolutionary and ecological implications.

Thirty-four species in twenty genera were sampled. The

dentition of the specimens examined was compared with

the normal dental formula for the species, and supernu-

merary and congenitally missing teeth were identified and

recorded. Agenesis was observed in 0.93 % of the speci-

mens analyzed (n = 10), being more frequent in otariids.

The posteriormost upper postcanines were the teeth absent

most frequently. Supernumerary teeth were observed in

1.8 % of the specimens (n = 19), more commonly in

phocids. Supernumerary teeth can be interpreted as either

atavistic manifestations (particularly for the posteriormost

postcanines in Otariidae) or cases of disturbances in dental

morphogenesis leading to the formation of extra teeth when

they occur in other positions of the tooth row. Morpho-

logical dental variants such as ectopic and geminated teeth

were also recorded. Cases of dental anomalies should have

a limited effect on the functional morphology of the

feeding apparatus in pinnipeds, with little influence on the

fitness and performance of the animals. Nevertheless, un-

derstanding patterns of dental variation should contribute

to future studies aiming to elucidate aspects of dental

evolution and the phylogenetic relationships of pinnipeds.

Keywords Agenesis � Atavism � Fur seals � Sea lions �Seals � Supernumerary teeth

Introduction

Extant pinnipeds are aquatic members of the mammalian

order Carnivora and comprise three monophyletic lineages:

Otariidae (fur seals and sea lions), Odobenidae (walruses)

and Phocidae (true or earless seals). Their fossil record

goes back at least to the late Oligocene (27–25 Ma), when

the earliest pinnipeds were aquatic carnivores with well-

developed paddle-shaped limbs. Pinnipeds originated in the

North Pacific and subsequently diversified throughout the

world’s oceans. Cladistic analysis of both morphologic and

molecular data supports pinnipeds as a monophyletic clade,

with ursids being the closest relatives of the group (Nya-

katura and Bininda-Emonds 2012).

Pinnipeds are generalist carnivores, feeding pre-

dominantly on fish and squid, and less often on crus-

taceans. Due to the lack of refined occlusion and reduced

mastication and food processing, their dentition is quite

simple in comparison with other members of Carnivora

(Berta 2002; Salazar-Ciudad and Jernvall 2010; Jones et al.

2013). Due to the simplification and morphological simi-

larity, premolars and molars are grouped as postcanine

teeth (Eastman and Coalson 1974). However, some pin-

niped species have specialized diets that are also reflected

Communicated by A. Schmidt-Rhaesa.

C. J. Drehmer

Departamento de Ecologia, Zoologia e Genetica, Universidade

Federal de Pelotas, Pelotas, RS, Brazil

D. Sanfelice

Instituto Federal de Ciencia, Tecnologia e Educacao do Rio

Grande do Sul, Campus Restinga, Porto Alegre, RS, Brazil

C. Loch (&)

Sir John Walsh Research Institute, Faculty of Dentistry,

University of Otago, Dunedin 9054, New Zealand

e-mail: carolina.loch@otago.ac.nz

123

Zoomorphology (2015) 134:325–338

DOI 10.1007/s00435-015-0255-x

Author's personal copy

in dental modifications. Crabeater (Lobodon carcinophaga)

and leopard seals (Hydrurga leptonyx), for instance, have

highly modified postcanine teeth with complex cusps to

trap and strain krill (Eastman and Coalson 1974). Walruses

(Odobenus rosmarus) have an unusual dentition composed

of large tusk-like canines that primarily function as social

organs used in display and striking, but are also used to stir

up benthic bivalves on the sea bottom and to help position

the walrus mouth and oral vibrissae for sensing food and

properly sucking it from the substrate (Miller 1975; Fay

1982). In addition, the peg-shaped postcanines are used to

crush bivalve molluscs (Berta 2002; Jones et al. 2013).

As most mammals, pinnipeds have diphyodont denti-

tion; however, the deciduous teeth are commonly shed in

utero or just after birth (Scheffer and Kraus 1964; East-

man and Coalson 1974; Miyazaki 2002). The early

establishment of the permanent dentition allows the pups

to be able to feed independently at a young age, a few

months before they are weaned (Kubota et al. 2000). The

number of teeth in the permanent dentition varies among

otariids and phocids, as well as among species of these

groups. For otariids, the dental formula is I3/3, C1/1,

PC5-6/5. For phocids, the dental formula is I2-3/2-1, C1/

1, PC5/5 in the Phocinae and I2/2, C1/1, PC5/5 in the

Monachinae (Monk seals) (King 1983, Hillson 2005). In

general, pinnipeds show considerable individual variation

in tooth number and illustrate nearly all the principles

observed in the numerical variation of teeth (Bateson

1894; Miles and Grigson 1990). The postcanine dental

series can be variable in number of teeth present with

frequent asymmetries from side to side of the same dental

arcade or between maxilla and mandible on the same side

(Briggs 1974). The high degree of dental variation found

in pinniped populations is a likely result of the relaxed

functional demands of their dentition, which lacks refined

occlusion and other complex specialized anatomical

adaptations for food processing (Jernvall 2000; Salazar-

Ciudad and Jernvall 2010).

In most mammals, teeth can vary in number, shape,

size, position and occlusion patterns among individuals of

the same species. When the variation is conspicuous and

uncommon among individuals, they are considered dental

anomalies (Miles and Grigson 1990). The etiology of

most so-called developmental dental anomalies is related

to genetic mechanisms; however, in some cases nutri-

tional and metabolic disorders, infection and environ-

mental influences may also be involved (Hoff and Hoff

1996). Dental anomalies have been largely investigated

since the beginning of the twentieth century, in almost all

mammalian orders (Bateson 1894; Miles and Grigson

1990; Hoff and Hoff 1996). While most efforts were

concentrated in humans and other primates, as well as

domesticated or economically important animals, investi-

gations focusing on wild species were much rarer. These

investigations ranged from analysis of single species (e.g.,

Vila et al. 1993; Szuma 1999) to broader taxonomic

surveys based on museum specimens (e.g., Bateson 1894;

Hall 1940; Miles and Grigson 1990; Hoff and Hoff 1996).

The occurrence of dental anomalies in other families of

Carnivora closely related to pinnipeds also was reviewed

in the classical works of Hall (1940) and Miles and

Grigson (1990). These studies reported variable frequen-

cies of dental anomalies in several species of Mustelidae

and Ursidae, with agenesis being more common than

supernumerary teeth.

Dental anomalies have been studied in some species of

pinnipeds, notably in Northern Hemisphere taxa (e.g.,

Chiasson 1955 for northern fur seals (Callorhinus ursinus);

Scheffer 1960 for the ribbon seal (Histriophoca fasciata);

Kubota and Togawa 1964 for northern fur seals, sea lions

and seals; Scheffer and Kraus 1964 for the northern fur

seal; Briggs 1974 for the northern elephant seal (Mirounga

angustirostris); Eastman and Coalson 1974 for the Weddell

seal (Leptonychotes weddellii); Stewart and Stewart 1987

for harp seals (Pagophilus groenlandicus); Stewart et al.

1988 for ringed seals (Pusa hispida); Suzuki et al. 1990 for

the Kuril, largha and ribbon seals (Phoca vitulina, Phoca

largha and H. fasciata); Konemann and van Bree 1997 for

North Atlantic phocids; Abbott and Verstraete 2005 for the

northern elephant seal; Cruwys and Friday 2006 for several

otariids and phocids; Sinai et al. 2014 for the California sea

lion (Zalophus californianus). For the Southern Hemi-

sphere, investigations were mostly based on Otariids from

southern South America (Drehmer and Ferigolo 1996 for

the South American fur seal (Arctocephalus australis);

Hamilton 1934, Drehmer et al. 2004 and Drehmer et al.

2009 for the southern sea lion (Otaria byronia); Loch et al.

2010 for southern fur seals and sea lions). While some of

these previous studies provided evolutionary and eco-

logical perspective in the interpretation of dental anomalies

in pinnipeds, most of them were focused on single taxa or

several species from the same geographic region.

The aim of this study was to investigate the nature and

prevalence of dental anomalies in a large sample of pin-

nipeds, representing most extant species. In particular, we

focused our observations on congenital anomalies such as

agenesis, supernumerary teeth and morphological variants,

and discussed the potential evolutionary and ecological

implications of such anomalies. Investigating patterns of

dental variation should help elucidate the phylogenetic

relationships, general biology and dental evolution of

pinnipeds, as well as shed light on the potential functional

implications of these anomalies. We did not include the

walrus O. rosmarus in this study.

326 Zoomorphology (2015) 134:325–338

123

Author's personal copy

Materials and methods

We recorded the incidence of agenesis, supernumerary

teeth and morphological variants in 1,078 pinniped speci-

mens in the following museum collections: Grant Museum

of Zoology, University College of London, UK (acronym

UCL-GMZ); the Natural History Museum, London, UK

(BMNH); University Museum of Zoology Cambridge, UK

(UMZC); Oxford University Museum of Natural History,

UK (OUM); Natural History Collections of the University

of Edinburgh, UK (UE-NHC); Museum National d’His-

toire Naturelle, France (MNHN); Zoologisch Museum

Amsterdam, The Netherlands (ZMA) and Museum fur

Naturkunde der Humboldt-Universitat zu Berlin, Germany

(MNHB).

Thirty-four species in twenty genera were studied

(Table 1). This sample represents all living pinniped spe-

cies currently recognized with exception of the walrus. The

number of specimens analyzed per species was not ho-

mogenous and varied depending on the availability of

material in the collections visited, particularly for the

species with low sample numbers. Although it is expected

that the cases of dental anomalies described here were

typical of each species, the conclusions were made with

some caution for taxa with low sample sizes.

The sample consisted of 521 males, 369 females and 168

individuals with undetermined sex. Individuals of all age

classes were examined. A complete list of the specimens

examined is presented in the ‘‘Appendix 1’’. From the 1,078

specimens analyzed, 976 had both skulls and lower jaws

available for analysis, while 102 consisted of skulls only. All

specimens studied had permanent teeth erupted. The sim-

plified crown morphology, extremely small size (no more

than 2 mm wide and 3 mm in length) and totally resorbed

roots of deciduous teeth (Kubota et al. 2000), allowed their

differentiation from supernumerary permanent teeth.

Specimens were analyzed macroscopically and pho-

tographed with a high-resolution digital camera. No ra-

diographs were obtained in this study. We compared the

dentition of the specimens examined with the normal

dental formula (I3/3, C1/1, PC5-6/5 for otariids; I2-3/2-1,

C1/1, PC5/5 for Phocinae and I2/2, C1/1, PC5/5 for

Monachinae) and identified supernumerary and missing

teeth by location in the tooth row and relative size and

form. Both the number of teeth and number of alveoli were

counted. We counted alveoli when teeth were presumably

lost during preparation. In cases of teeth with double roots,

especial attention was given to differentiate between in-

traalveolar (interradicular) and interalveolar (interdental)

septa in order to avoid miscounting partial as single

alveolus. Missing teeth due to possible trauma or patho-

logical losses were not included in this analysis. Following

Drehmer et al. (2004), Abbott and Verstraete (2005) and

Loch et al. (2010), supernumerary and congenitally miss-

ing teeth were identified on the basis of absent or multiple

alveolar sockets. Congenitally missing teeth were defined

by taking into consideration the absence of the tooth and

alveolus, as well as morphologically normal bone (smooth

aspect) present at the site. Supernumerary teeth included

extra teeth adjacent to the normal teeth present in the tooth

row. Morphological variants were teeth that differed from

the expected normal morphology and included cases of

ectopic (teeth that develop away from the normal tooth-

bearing area) and geminated teeth (teeth with double

crown, but single root).

Results

Agenesis

Congenital loss of teeth was observed in 0.93 % of the

specimens (n = 10). We found agenesis in 1/661 phocids

(0.15 %) and 9/418 otariids (2.15 %; mainly PC6;

Table 1). The difference of 2.0 falls within the 95 % CI

(with correction for continuity) of 0.63–4.05 %, being not

significant. Cases of agenesis were observed in 6/369 fe-

males (1.6 %), 3/521 males (0.5 %) and 1/168 (0.6 %)

specimens with undetermined sex.

Upper postcanines were the teeth more commonly absent,

particularly the most posterior ones (Fig. 1). The agenesis of

upper PC/6 was observed in 5 specimens of Otariidae, from

which four of them corresponded to symmetrical agenesis of

both PC/6 (northern fur seal C. ursinus, UMZC 7227.2

911.KB; Galapagos fur seal Arctocephalus galapagoensis,

MNHN 1962-1153; South American fur seal A. australis,

BMNH84.915;Cape fur sealArctocephalus pusillus, BMNH

1927.7.2.4). One specimen of the Antarctic fur seal Arcto-

cephalus gazella (UMZC 7321.K) showed the asymmetrical

agenesis of the left PC/6. The only phocid diagnosed with

agenesis (southern elephant seal Mirounga leonina, BMNH

1951.7.17.5) was lacking an upper right PC/5. Agenesis of

other postcanine teeth included the congenital loss of both

PC/3 (California sea lion Z. californianus,MNHN1882-190)

and both PC/5 (Antarctic fur sealA. gazella,UMZC7321.D).

Incisors were also recorded as absent in one specimen of the

Steller sea lion Eumetopias jubatus (UMZC 7081) in which

the symmetrical absence of both upper I/1 was observed. The

only case of agenesis recorded for the lower jaw was regis-

tered for the Antarctic fur seal A. gazella (UMZC 7321.F),

where the right PC/1 was absent.

Supernumerary teeth

Supernumerary teeth were observed in 1.8 % of the spe-

cimens (n = 19). We noted supernumerary teeth in 13/661

Zoomorphology (2015) 134:325–338 327

123

Author's personal copy

phocids (2.0 %) and 6/418 otariids (1.4 %; Table 1). As for

agenesis, this difference (0.53 %) was not significant

(95 % CI -1.5 to 2.2 %). Of the 19 specimens with su-

pernumerary teeth, 42 % (n = 8) had extra teeth occurring

simultaneously and symmetrically on both sides of upper

or lower jaws. Supernumerary teeth were observed in

10/521 males (1.9 %), 4/369 females (1 %) and 5/168 of

specimens with undetermined sex (2.9 %).

In the Otariidae, most supernumerary teeth were noted

in the upper jaw (n = 5) (Fig. 2). Two specimens of the

Australian sea lion Neophoca cinerea (BMNH

1968.9.26.27 and BMNH 1968.9.26.30) had extra teeth

Table 1 Number of cases of dental anomalies (agenesis, supernumerary teeth and morphological variants) for each species of Phocidae and

Otariidae studied

Species Author and year Number of specimens

analyzed

Number of cases

Agenesis Supernumerary Morphological variants

Phocidae

Cystophora cristata Erxleben (1777) 58 – 4 –

Erignathus barbatus Erxleben (1777) 8 – – –

Halichoerus grypus Fabricius (1791) 73 – 1 –

Histriophoca fasciata Zimmerman (1783) 4 – – –

Hydrurga leptonyx Blainville (1820) 69 – – 2

Leptonychotes weddellii Lesson (1826) 94 – – –

Lobodon carcinophaga Hombron and Jacquinot (1842) 71 – 1 –

Mirounga leonina Linnaeus (1758) 80 1 2 1

Mirounga angustirostris Gill (1866) 1 – – –

Neomonachus tropicalis Gray (1850) 1 – – –

Monachus monachus Hermann (1779) 9 – 1 –

Neomonachus schauinslandi Matschie (1905) 1 – – –

Ommatophoca rossii Gray (1844) 20 – 2 –

Pagophilus groenlandicus Erxleben (1777) 50 – 1 –

Phoca vitulina Linnaeus (1758) 69 – – –

Phoca largha Pallas (1811) 5 – – –

Pusa caspica Gmelin (1788) 10 – – –

Pusa hispida Schreber (1775) 28 – 1 –

Pusa sibirica Gmelin (1788) 10 – – –

Otariidae

Arctocephalus australis Zimmermann (1783) 54 1 – –

Arctocephalus forsteri Lesson (1828) 15 – – –

Arctocephalus galapagoensis Heller (1904) 7 1 – –

Arctocephalus gazella Peters (1876) 65 3 – –

Arctocephalus philippii Peters (1866) 1 – – –

Arctocephalus pusillus Schreber (1775) 31 1 1 –

Arctocephalus tropicalis Gray (1872) 33 – 1 –

Callorhinus ursinus Linnaeus (1758) 44 1 2 –

Eumetopias jubatus Schreber (1776) 27 1 – –

Neophoca cinerea Peron (1816) 9 – 2 –

Otaria byronia Blainville (1820) 72 – – –

Phocarctos hookeri Gray (1844) 5 – – –

Zalophus californianus Lesson (1828) 13 – – –

Zalophus japonicus Peters (1866) 1 – – –

Zalophus. wollebaeki Sivertsen (1953) 12 – – –

Zalophus sp. 29 1 – –

Species names follow the ‘‘List of marine mammal species and subspecies of the Society for Marine Mammalogy’’ (Committee on Taxonomy

2014)

328 Zoomorphology (2015) 134:325–338

123

Author's personal copy

posterior to the left PC/5, resulting in six upper postca-

nines. Other cases of supernumerary upper teeth in otariids

include extra postcanines in different positions in the tooth

row (northern fur seal C. ursinus, UMZC 7223.2—between

left PC/2 and 3; Subantarctic fur seal Arctocephalus

tropicalis, MNHN 1972-644—at left PC/4 position; Cape

fur seal A. pusillus, BMNH 1960.1.29.6—posterior to up-

per left PC/6). Only one case of supernumerary teeth in the

lower jaw was recorded in Otariidae. One specimen of C.

ursinus (MNHB 37402) had a small extra tooth behind the

right PC/5.

In phocids, supernumerary teeth (n = 8) also were more

frequent in the upper than lower jaw (Fig. 2). Supernumerary

lower teeth were observed in only 3 specimens, and 2 spe-

cimens of the Ross sealOmmatophoca rossii (MNHB 36245

and MNHB 36248) presented extra teeth simultaneously in

the upper and lower jaw. Cases of supernumerary upper teeth

were more frequently observed for postcanines, normally

located between the canine and PC/1. Supernumerary in-

cisors were recorded for the southern elephant sealMirounga

leonina (MNHB 47195) at the left I/1 position and for the

Mediterranean monk seal Monachus monachus (BMNH

1894.7.27.1). Bilateral supernumerary teethwere observed in

75 % of the specimenswith extra teeth (n = 6), always at the

same tooth position on both sides.

Morphological variants

We noted 3/1,079 (0.3 %) skulls with abnormal teeth, all in

the Phocidae: two ectopic teeth and one germinated teeth

(Fig. 3). Ectopic teeth were observed in two specimens of

the leopard seal H. leptonyx (BMNH 1939.4.29.5 and

MNHN 1982-799). While in one specimen the ectopic

tooth was located in the center of the palate equidistant

between the two upper PC2 (MNHN 1982-799), in the

other specimen (BMNH 1939.4.29.5), it was located at the

palatine horizontal lamina, near the right PC3. One case of

geminated teeth was diagnosed in the southern elephant

seal M. leonina (BMNH 867), in which the upper left PC3

and PC4 were joined together.

Discussion

This study aimed to investigate the nature and prevalence

of dental anomalies in a large sample of pinnipeds, with

Fig. 1 Cases of dental agenesis in pinnipeds. a Both upper PC/6

(arrows) are missing in a specimen of the Galapagos fur seal A.

galapagoensis (MNHN 1962-1153). b The left PC/6 (arrow) is

missing in the Antarctic fur seal A. gazella (UMZC 7321.K). c The

upper right PC/5 (arrow) is missing in the southern elephant seal M.

leonina (BMNH 1951.7.17.5). d Both I/1 (arrow) are missing in the

Steller sea lion E. jubatus (UMZC 7081)

Zoomorphology (2015) 134:325–338 329

123

Author's personal copy

Fig. 2 Cases of supernumerary teeth in pinnipeds. a An extra

alveolus in the upper PC/6 position (arrow) in the Australian sea lion

N. cinerea (BMNH 1968.9.26.30). b Extra alveolus in the lower PC/6

position (arrow) in the northern fur seal C. ursinus (MNHB 37402).

c Bilateral supernumerary teeth in the PC/6 position and extra upper

left PC/7 (arrows) in the Ross seal O. rossii (MNHB 36248).

d Bilateral supernumerary teeth (arrows) in the hooded seal C.

cristata (ZMA 18.060) located mesially to the PC/1. e Supernumerary

incisor (arrow) in the southern elephant seal M. leonina (MNHB

47195) located mesially to the left I/1. f Supernumerary upper PC/6

(arrow) in the gray seal H. grypus (MNHB 28412), reduced in size

and simplified in shape

330 Zoomorphology (2015) 134:325–338

123

Author's personal copy

particular focus in cases of agenesis, supernumerary teeth

and morphological variants. The sample analyzed repre-

sented all extant species currently recognized in a global

scale, with exception of the walrus. These anomalies were

discussed in light of their etiology and the potential evo-

lutionary and ecological implications of their occurrence.

Agenesis of teeth

The congenital loss of teeth is one of the most common

cases of dental anomalies in mammals (Hall 1940), and it

has been recorded in several species of pinnipeds (Kubota

and Togawa 1964; Miles and Grigson 1990). For this

group, agenesis of the last postcanines is often observed in

museum specimens, commonly the upper PC/5 or 6

(Hamilton 1934; Drehmer et al. 2004; Loch et al. 2010).

This observation is consistent with the findings of this

study, where 60 % (n = 6) of the specimens diagnosed

with agenesis corresponded to congenital losses of the most

posterior postcanines. Here, four of these six cases were

cases of symmetrical agenesis of both upper PC/5 and 6.

It is widely accepted that the oral processing of food is

less prominent in pinnipeds than in most terrestrial Car-

nivora. Most phocids and otariids share a generalist pierce-

feeding method, catching fish and squid using sharp ho-

modont teeth and swallowing prey whole (Adam and Berta

2002; Berta et al. 2006; Jones et al. 2013). The limited food

processing has led to a simplification of the dentition,

particularly the postcanine teeth, which experienced re-

duction in crown size, complexity and coalescence of roots.

The complex dentitions of their terrestrial ancestors and of

archaic pinnipeds such as Enaliarctos Mitchell & Tedford,

1973 and Puijila Rybczynski, Dawson and Tedford, 2009

suggest that the homodont dentition of most living pin-

nipeds underwent simplification during their evolution

(Boessenecker 2011). The overall more simplified dental

morphology of otariids when compared to those of other

pinnipeds, with little variation in the form of teeth between

species (Eastman and Coalson 1974), could account for a

higher incidence of agenesis in otariids than in taxa with

more complex dental morphologies such as phocids.

Another important aspect of the postcanine dentition in

pinnipeds is the reduced integration and occlusion between

the upper and lower jaws (Miller et al. 2007; Boessenecker

2011). In otariids, the two most posterior upper postcanine

teeth lie medial to the lower tooth row and do not occlude

(Adam and Berta 2002). The most posterior upper post-

canine (PC/5 or 6) is normally located posterior to the

lower tooth row and also lacks an occlusal counterpart in

the lower jaw. The small size and single-rooted condition

of this tooth has been interpreted as a vestigial structure

that can often be absent (Chiasson 1957; Kubota and To-

gawa 1964; Drehmer et al. 2004). Hall (1940) concluded

that the most common place for the absence of a molar

tooth is the posterior end of the molar series, supporting the

observations of this study. He also suggested that con-

genitally missing teeth are the teeth of the least survival

value to the individual and to the species as a whole, due to

the small size and degenerate nature of the crown of teeth

commonly present in places where agenesis is common.

Miller et al. (2007) hypothesized that teeth that are not

integrated within the dentition for food processing may be

variably present or may be variable in morphology or size.

Thus, the lack of integration and occlusion in the dentition

of pinnipeds may relate to a higher degree of dental var-

iation in this group if compared to most terrestrial carni-

vores in which the dentition is highly integrated (Jernvall

2000; Miller et al. 2007; Salazar-Ciudad and Jernvall 2010;

Boessenecker 2011) and might explain the cases of

agenesis of the posteriormost teeth. Other marine mammals

Fig. 3 Cases of morphological variants in pinnipeds. a An ectopic palatal tooth (arrow) in the leopard seal H. leptonyx (MNHN 1982-799). b A

geminated postcanine tooth (arrow) in the southern elephant seal M. leonina (BMNH 867)

Zoomorphology (2015) 134:325–338 331

123

Author's personal copy

such as cetaceans also experienced loss of tooth occlusion

during their evolution, generating less constrained tooth

developmental mechanisms and allowing for some ex-

perimentation in tooth pattern and number (Armfield et al.

2013). The homodont and commonly polydont dentition of

most extant cetaceans is a result of this relaxed selective

pressure, although some species have secondarily reduced

the number of teeth (Werth 2006). In most homodont and

polydont delphinids, tooth counts are often variable among

individuals (Miyazaki 2002).

Sea lions of the genus Zalophus illustrate common

patterns of dental variation in pinnipeds. It has been sug-

gested that the number of teeth is variable among species,

with the California sea lion Z. californianus having 5 upper

postcanine teeth, the Galapagos sea lion Zalophus wolle-

baeki having 6 and the Japanese sea lion Zalophus japo-

nicus having either 5 or 6 postcanines (King 1983). Sinai

et al. (2014) reported a high incidence (25 %) of extra

maxillary teeth in the PC/6 position for a large sample of

the Californian sea lion. In our study, Z. wollebaeki showed

a similar proportion of individuals with 5 and also with 6

postcanine teeth; the only Z. japonicus had 5, and the

majority of Z. californianus sampled also had 5 postcanine

teeth. The presence of the upper PC/6 in Zalophus is thus

variable, which suggests that this tooth can be regarded

either as a vestigial (evolutionary remnant found in adults)

or rudimentary structure (partially formed structures often

found during early stages of development—see Hall (1984)

for the definitions of these terms). It is possible that the

upper PC/6 in Z. wollebaeki can also be regarded as a case

of taxic atavism, similar to the condition that Drehmer

et al. (2004) proposed for the South American sea lion O.

byronia and New Zealand sea lion Phocarctos hookeri (see

below in Supernumerary teeth).

Supernumerary teeth

The interpretation of the significance of supernumerary

teeth in pinnipeds is dependent on their position of oc-

currence. In otariids, supernumerary teeth at end of the

lower tooth row (posterior to the PC/5), reduced in size and

with simplified crown shape, have been considered as

spontaneous atavistic manifestations (Drehmer et al. 2004,

2009). According to Hall (1940), extra molars always occur

at the posterior end of the molar series and are always

smaller than the other teeth in the tooth row. In pinnipeds,

these extra teeth could represent the reappearance of the

lower second molar observed in more ancient pinni-

pedimorphs such as the Oligo-Miocene genera Pter-

onarctos Barnes, 1989 and Enaliarctos. Basal pinnipeds

such the desmatophocid Allodesmus Kellogg, 1922 the

dusignathine walrus Pontolis magnus True, 1905 and

Imagotaria downsi Mitchell, 1968 also possessed the lower

second molar (Barnes 1972; Repenning and Tedford 1977;

Demere 1994). The occurrence of a reduced extra tooth

posterior to the PC/5 in a specimen of the northern fur seal

C. ursinus (MNHB 37402) could be thus interpreted as an

atavistic reappearance of the lower second molar.

Two specimens of the Australian sea lion N. cinerea

(BMNH 1968.9.26.27 and BMNH 1968.9.26.30) presented

supernumerary teeth at the end of the upper tooth row. Five

upper postcanines are normally present in this species

(King 1983), a derived condition in the phylogenetic

framework of otariids (Berta and Wyss 1994). The occur-

rence of supernumerary teeth at the PC/6 position could

also be considered as a spontaneous atavistic manifestation,

a similar condition as described earlier for the northern fur

seal C. ursinus. According to Drehmer et al. (2004), the

presence of 5 upper postcanines is a synapomorphy of the

Steller sea lion and Australian sea lion, and it could be

interpreted as a reversal from 5 to 6 postcanines in other

otariid genera such as Otaria and Phocarctos. Reversals

have been recognized as atavistic phenomena (for taxic

atavisms, see Stiassny 1992). The two specimens of the

Australian sea lion (N. cinerea) reported here support this

interpretation; however, no specimens of the Steller sea

lion E. jubatus and New Zealand sea lion P. hookeri ana-

lyzed here were diagnosed with dental anomalies.

The occurrence of supernumerary teeth at other posi-

tions in the tooth row, particularly its mid-section between

PC/1 and PC/5 and 6, is better interpreted as cases of

disturbances in dental morphogenesis leading to the du-

plication of the dental germ and formation of extra teeth

(Hall 1940; Wolsan 1984; Suzuki et al. 1990; Hoff and

Hoff 1996). This was possibly the case for the otariids C.

ursinus (northern fur seal, UMZC 7223.2) and A. tropicalis

(Subantarctic fur seal, MNHN 1972-644).

Supernumerary teeth were the most common dental

anomalies that we noted in Phocidae. This was cor-

roborated in past studies with diverse species (Burns and

Fay 1970—ribbon seals H. fasciata; Stewart and Stewart

1987—harp seals P. groenlandicus; Suzuki et al. 1990—

Kuril, largha and ribbon seals (P. vitulina, P. largha and H.

fasciata); Cruwys and Friday 2006—several taxa). In most

mammals, cases of agenesis are more common than su-

pernumerary teeth; however, the opposite is often common

for true seals (Suzuki et al. 1990). Extra upper postcanines

located between the canine and PC/1 were common in the

present study in the harp seal P. groenlandicus and hooded

seal Cystophora cristata. Stewart and Stewart (1987) also

observed extra teeth at the PC/1 position as the most fre-

quent anomaly in P. groenlandicus. Lower supernumerary

teeth were observed here in the Ross seal O. rossii,

southern elephant seal M. leonina, harp seal P. groen-

landicus and ringed seal P. hispida, commonly posterior to

the PC/5. Eastman and Coalson (1974) also reported a high

332 Zoomorphology (2015) 134:325–338

123

Author's personal copy

incidence of dental variation in the Ross seal, with speci-

mens often presenting either 4, 6 or 7 postcanines instead

of the expected 5. Briggs (1974) and Abbott and Verstraete

(2005) performed a broad investigation on the dentition of

the northern elephant seal M. angustirostris, and both

studies reported the presence of lower supernumerary teeth

posterior to the PC/5.

The occurrence of supernumerary teeth in phocids has

no clear evolutionary implications. It is likely that distur-

bances during dental morphogenesis leading to formation

of extra teeth are the main causes (Kubota and Togawa

1964; Wolsan 1984; Hoff and Hoff 1996). Future studies

integrating dental development, analysis of fossils and

phylogenetic relationships should help elucidate whether

supernumerary teeth in Phocidae would also represent

cases of taxic atavisms.

Morphological variants

Morphological variants analyzed in this study comprised

cases of ectopic and geminated teeth. Ectopic teeth involve

cases of dental elements that develop away from the nor-

mal tooth-bearing area, including cases where the normal

pathway was obstructed by another tooth and the impacted

tooth emerged in an abnormal position (Miles and Grigson

1990; Richardson and Russel 2000). According to

Richardson and Russel (2000), ectopic palatal teeth are

caused by a genetic-base developmental disturbance during

embryonic growth and are often associated with anomalies

in tooth size, shape, number and structure. The specimen

MNHN 1982-799 (leopard seal, H. leptonyx) corroborates

this description, as the ectopic palatal tooth is supernu-

merary, reduced in size and with a much simplified shape

than the other teeth.

In the case of double teeth, they can develop from either

the incomplete division of a single dental germ (gemina-

tion) or the fusion of two adjacent germs (dental fusion),

resulting in a tooth with double crown, but single root

(Hoff and Hoff 1996; Schuurs and van Loveren 2000).

Double teeth are likely caused by disturbances in the epi-

genetic system underlying dental morphogenesis, which

may lead to duplication or coalescence of the dental germ

(Schuurs and van Loveren 2000; Drehmer et al. 2004).

Geminated teeth have been previously reported in pin-

nipeds (Bateson 1894; Kubota and Togawa 1964; Stewart

and Stewart 1987; Drehmer et al. 2004) and other marine

mammals such as cetaceans (Loch et al. 2011). The similar

size between the two dental elements and the apparent

presence of two root canals in the geminated tooth of

BMNH 867 (southern elephant seal, M. leonina) suggest a

typical case of dental fusion by the coalescence of the PC/3

and 4.

Conclusions

Due to a trend toward homodonty in the postcanines, the

loss of integration and occlusion between teeth and the

limited food processing of most pinnipeds, cases of dental

agenesis, supernumerary teeth and morphological variants

should have a limited effect in the functional morphology

of the feeding apparatus of fur seals, sea lions and true

seals, with little influence on the fitness and performance of

individuals. Similarly, cases of dental anomalies most

likely do not contribute toward morbidity or mortality.

Although it is unlikely these dental anomalies resulted in

ecological implications, some of these cases may have

evolutionary significance such as the atavistic reappearance

of teeth commonly present in their ancestors and the con-

genital loss of posteriormost teeth due to a trend of nu-

merical reduction in the dentition of some pinnipeds.

Understanding patterns of dental variation will contribute

to future studies aiming to elucidate aspects of dental

evolution and the phylogenetic relationships of Pinnipedia.

Acknowledgments Thanks are extended to the curators of the sci-

entific collections visited for allowing us to study the specimens under

their care: Robert Asher and Mathew Lowe (Museum of Zoology

Cambridge); Mark Carnall (Grant Museum of Zoology, UCL); Mal-

gosia Nowak-Kemp (Oxford University Museum of Natural History);

Graham Stone (University of Edinburgh); Roberto Portela-Miguez,

Richard Sabin and Louise Tomsett (Natural History Museum, Lon-

don); Ronald Vonk (Zoologisch Museum Amsterdam); Christine

Lefevre (Museum National d’Histoire Naturelle) and Frieder Mayer

(Museum fur Naturkunde der Humboldt-Universitat zu Berlin). Jules

A. Kieser (in memoriam) and Robert Boessenecker patiently revised

early drafts of this study. Alexander Werth and an anonymous referee

provided valuable suggestions that greatly improved this manuscript.

D. Sanfelice acknowledges CAPES for a Postdoctoral fellowship and

is indebted to Anjali Goswami (UCL), the Centre for Ecology and

Evolution (UCL) and Synthesys (especially Manja Voss, DE-TAF

Office) for their financial and logistic support. C Loch acknowledges

the Sir John Walsh Research Institute for a Postdoctoral Fellowship

and Jules A. Kieser for the inspirational mentoring in life and

research.

Appendix 1: Specimens examined

Otariidae. Arctocephalus australis: BMNH-1013.e,

BMNH-1879.8.21.5, BMNH-1880.7.28.17, BMNH-1919.

7.7.10090, BMNH-1949.3.17.1, BMNH-1949.3.17.11,

BMNH-1949.3.17.13, BMNH-1949.3.17.15, BMNH-

1949.3.17.16, BMNH-1949.3.17.19, BMNH-1949.3.17.21,

BMNH-1949.3.17.23, BMNH-1949.3.17.34, BMNH-

1949.3.17.38, BMNH-1949.3.17.5, BMNH-1949.3.17.58,

BMNH-1949.3.17.6, BMNH-1949.3.17.8, BMNH-1949.

3.17.9, BMNH-1950.11.14.1, BMNH-1984.954, BMNH-

1984.956, BMNH-1984919, BMNH-1984942, BMNH-

83.314, BMNH-84.91, BMNH-84.911, BMNH-84.912,

Zoomorphology (2015) 134:325–338 333

123

Author's personal copy

BMNH-84.915, BMNH-84.916, BMNH-84.918, BMNH-

84.921, BMNH-84.923, BMNH-84.925, BMNH-84.928,

BMNH-84.93, BMNH-84.932, BMNH-84.935, BMNH-

84.937, BMNH-84.947, BMNH-84.957, BMNH-84.959,

BMNH-84.967, BMNH-84.968, BMNH-84.97, BMNH-

84.974, BMNH-84.978, BMNH-84917, BMNH-84933,

BMNH-84938, BMNH-84940, BMNH-84948, BMNH-

84973, MNHB-4961. Arctocephalus forsteri: BMNH-

1968.9.26.2, BMNH-1872.6.25.1, BMNH-1876.2.15.4,

BMNH-1876.2.16.5, BMNH-1897.10.10.6, BMNH-

1968.9.26.4, BMNH-1968.9.26.6, BMNH-1968.9.26.9,

MNHB-70660, UMZC 7422, UMZC 7423, UMZC 7424,

UMZC 7427, UMZC 7429, UMZC 7434. Arctocephalus

galapagoensis: BMNH-1991.1, BMNH-1991.2, BMNH-

1991.3, MNHN-1962-1152, MNHN-1962-1153, MNHN-

1962-1157, MNHN-1962-1159. Arctocephalus gazella:

BMNH-1958.4.24.4, BMNH-1958.4.24.5, BMNH-

1958.4.24.6, BMNH-1960.8.10.13, BMNH-1960.8.10.14,

BMNH-1960.8.10.19, BMNH-1960.8.10.2, BMNH-

1960.8.10.24, BMNH-1960.8.10.29, BMNH-1960.8.10.30,

BMNH-1960.8.10.31, BMNH-1960.8.10.32, BMNH-

1960.8.10.33, BMNH-1960.8.10.34, BMNH-1960.8.10.36,

BMNH-1960.8.10.37, BMNH-1960.8.10.38, BMNH-

1960.8.10.39, BMNH-1960.8.10.41, BMNH-1960.8.10.46,

BMNH-1960.8.10.49, BMNH-1960.8.10.5, BMNH-

1960.8.10.50, BMNH-1960.8.10.51, BMNH-1960.8.10.54,

BMNH-1960.8.10.55, BMNH-1960.8.10.7, BMNH-

1960.8.10.8, BMNH-1960.81.10.57, BMNH-1962.10.16.1,

BMNH-1962.6.14.13, BMNH-1962.6.14.14, BMNH-

1962.6.14.15, BMNH-1962.6.14.16, BMNH-1964.9.22.1,

BMNH-1964.9.22.2, BMNH-1980.8.4.4, BMNH-

1981.1239, BMNH-1981.124, BMNH-1981.1241, BMNH-

1981.1243, BMNH-1981.125, BMNH-1981.1251, BMNH-

1981.1254, BMNH-1981.1255, BMNH-1981.1257,

BMNH-1981.1258, BMNH-1991.4, MNHB-86626, UMZC

7321.A, UMZC 7321.B, UMZC 7321.C, UMZC 7321.D,

UMZC 7321.E, UMZC 7321.F, UMZC 7321.G, UMZC

7321.H, UMZC 7321.I, UMZC 7321.J, UMZC 7321.K,

UMZC 7321.L, UMZC 7321.M, UMZC 7321.N, UMZC

7321.O. Arctocephalus philippii: BMNH-1883.11.8.1.

Arctocephalus pusillus: BMNH-1220a, BMNH-

1925.1.2.268, BMNH-1925.1.2.269, BMNH-1925.1.2.66,

BMNH-1925.1.2.68, BMNH-1927.7.2.2, BMNH-

1927.7.2.4, BMNH-1927.7.2.7, BMNH-1939.1889,

BMNH-1953.4.9.1, BMNH-1953.4.9.2, MNHB-5175,

MNHB-5176, OUM13884, UMZC 7361, BMNH-

1883.7.28.1, BMNH-1883.7.28.13, BMNH-1887.5.6.1,

BMNH-1889.2.20.1, BMNH-1960.1.29.1, BMNH-

1960.1.29.2, BMNH-1960.1.29.3, BMNH-1960.1.29.4,

BMNH-1960.1.29.6, BMNH-1968.9.26.1, BMNH-

1968.9.26.10, BMNH-1968.9.26.11, BMNH-1968.9.26.12,

UMZC 7425, UMZC 7426, MNHB-32100. Arctocephalus

tropicalis: BMNH-1955.3.14.2, BMNH-1955.3.14.5,

BMNH-1955.3.14.7, BMNH-1957.4.23.10, BMNH-

1957.4.23.11, BMNH-1957.4.23.20, BMNH-1957.4.23.20,

BMNH-1957.4.23.21, BMNH-1957.8.1.1, BMNH-

1968.4.4.1, BMNH-1968.4.4.2, BMNH-1968.4.4.9,

MNHB-5027, MNHN-1875-623, MNHN-1962-4146,

MNHN-1962-4146, MNHN-1962-4147, MNHN-1962-

4148, MNHN-1962-4149, MNHN-1962-4150, MNHN-

1962-4151, MNHN-1962-4153, MNHN-1963-30, MNHN-

1971-118, MNHN-1972-644, MNHN-1976-378, MNHN-

1976-384, MNHN-1978-334, MNHN-1978-339, MNHN-

1986-070, MNHN-1986-72, ZMA 19.584, ZMA 19.585.

Callorhinus ursinus: BMNH-1878.5.10.2, BMNH-

1891.12.18.10, BMNH-1891.12.18.9, BMNH-

1891.18.12.11, BMNH-1893.1.28.2, BMNH-1897.1.18.10,

BMNH-1897.2.17.2, BMNH-1928.4.21.45, BMNH-

1928.4.21.52, BMNH-1928.4.21.53, BMNH-1928.4.21.54,

BMNH-1928.4.21.55, BMNH-1928.4.21.59, BMNH-

1928.4.21.60, BMNH-1928.4.21.61, BMNH-1928.4.21.63,

BMNH-1928.4.21.65, BMNH-1928.4.21.67, BMNH-

1950.3.29.4, BMNH-1950.3.29.5, BMNH-1950.3.29.6,

BMNH-1950.3.29.7, BMNH-1951.2.15.1, BMNH-

1960.5.2.2, MNHB-10111899, MNHB-37402, MNHB-

37403, MNHB-5142, MNHB-5627, MNHB-5648, MNHB-

74328, MNHN-1878-198, MNHN-26, MNHN-27, UMZC

7221, UMZC 7223.2, UMZC 7225.2, UMZC 7227.2

911.KA, UMZC 7227.2 911.KB, UMZC 7228, UMZC

7229, ZMA 17.131, ZMA 17.132, ZMA 17.992. Eume-

topias jubatus: BMNH-1950.7.21.4, BMNH-

1880.10.11.11, BMNH-1897.1.18.6, BMNH-1897.1.18.8,

BMNH-1897.2.17.1, BMNH-1903.10.11.7, BMNH-

1903.10.11.8, BMNH-1905.11.8.1, BMNH-1928.4.21.70,

BMNH-1950.3.29.10, BMNH-1950.3.29.11, BMNH-

1950.3.29.12, BMNH-1950.7.21.3, BMNH-1950.7.21.5,

BMNH-1950.7.21.6, BMNH-1950.7.21.7, BMNH-

1950.7.21.8, BMNH-1968.8.9.1, BMNH-1991.272, UCL-

GMZ-Z309, MNHB-2782, MNHB-37702, MNHB-47500,

MNHB-70692, MNHB-72815, MNHB-72816, UMZC

7081. Neophoca cinerea: BMNH-1897.10.10.5, BMNH-

1925.10.8.32, BMNH-1925.10.8.33, BMNH-1968.9.26.27,

BMNH-1968.9.26.23, BMNH-1968.9.26.25, BMNH-

1968.9.26.29, BMNH-1968.9.26.30, UMZC 7152. Otaria

byronia: BMNH-1851.5.5.51, BMNH-1869.2.24.1,

BMNH-1869.8.10.1, BMNH-1886.12.13.1, BMNH-

1900.5.7.10, BMNH-1920.6.5.1, BMNH-1925.12.17.11,

BMNH-1934.1.21.4, BMNH-1939.1.21.10, BMNH-

1939.1.21.104, BMNH-1939.1.21.106, BMNH-1939.1.

21.107, BMNH-1939.1.21.108, BMNH-1939.1.21.109,

BMNH-1939.1.21.112, BMNH-1939.1.21.113, BMNH-

1939.1.21.115, BMNH-1939.1.21.116, BMNH-1939.1.

21.118, BMNH-1939.1.21.119, BMNH-1939.1.21.12,

BMNH-1939.1.21.120, BMNH-1939.1.21.122, BMNH-

1939.1.21.133, BMNH-1939.1.21.14, BMNH-1939.1.

21.163, BMNH-1939.1.21.17, BMNH-1939.1.21.177,

334 Zoomorphology (2015) 134:325–338

123

Author's personal copy

BMNH-1939.1.21.180, BMNH-1939.1.21.3, BMNH-

1939.1.21.5, BMNH-1939.1.21.71, BMNH-1939.1.21.72,

BMNH-1939.1.21.76, BMNH-1939.1.21.77, BMNH-

1939.1.21.78, BMNH-1939.1.21.81, BMNH-1939.1.21.83,

BMNH-1939.1.21.84, BMNH-1939.1.21.85, BMNH-

1939.1.21.86, BMNH-1939.1.21.89, BMNH-1949.3.17.83,

BMNH-1950.11.6.1, BMNH-1959.12.4.6, BMNH-335.d,

BMNH-335 m, BMNH-84.984, BMNH-84987, BMNH-

WS 479, UCL-GMZ-Z2247, MNHB-288, MNHB-33881,

MNHB-70685, MNHB-70693, MNHB-70695, MNHB-

72817, MNHB-72822, MNHN-1889-1540, OUM13885,

OUM13887, OUM14203, UMZC 7005, UMZC 7024,

UMZC 7028, UMZC 7029, UMZC 7030, UMZC 907.AB.

Phocarctos hookeri: BMNH-1876.2.16.9, BMNH-

1908.2.20.53, UMZC 7182, UMZC 7183, UMZC 7184.

Phocidae. Cystophora cristata: UMZC 7746, UMZC

7750, UMZC 7741, BMNH-1843.10.7.7, BMNH-

1843.10.7.8, BMNH-1844.2.2.1, BMNH-1844.6.23.1

(332.a), BMNH-1870.6.22.10 (332.i), BMNH-1890.8.1.4,

BMNH-1907.9.4.4, BMNH-1949.2.3.7, BMNH-

1949.2.3.8, BMNH-1951.4.19.2, BMNH-332.d, BMNH-

332.g, BMNH-332.h, MNHB-16322, MNHB-3296,

MNHB-33244, MNHB-33246, MNHB-33255, MNHB-

33258, MNHB-60594, MNHN-1929.226, MNHN-1990-

689, MNHN-2007-406, OUM13881, ZMA 16.334, ZMA

16.336, ZMA 16.337, ZMA 16.338, ZMA 16.339, ZMA

16.34, ZMA 16.341, ZMA 16.343, ZMA 16.344, ZMA

16.345, ZMA 16.346, ZMA 16.347, ZMA 18.059, ZMA

18.060, ZMA 18.061, ZMA 18.062, ZMA 18.063, ZMA

18.065, ZMA 18.066, ZMA 18.067, ZMA 18.068, ZMA

18.069, ZMA 18.081, ZMA 18.088, ZMA 18.089, ZMA

18.098, ZMA 24.696, ZMA 25.384, ZMA 25.448. Erig-

nathus barbatus: BMNH-1887.9.28.1, BMNH-1896.9.

23.6, BMNH-1937.10.23.9, OUM13878, OUM13890,

UMZC 8022, UMZC 8023, UMZC 8024. Halichoerus

grypus: BMNH-1845.3.17.8, BMNH-1863.3.18.3, BMNH-

1924.1.3.1, BMNH-1934.6.20.1, BMNH-1938.3.12.1,

BMNH-1939.1.14.1, BMNH-1950.1.23.5, BMNH-1951.

11.28.1, BMNH-1955.9.23.1, BMNH-1956.9.26.4,

BMNH-196.1.23.7, BMNH-1961.1.23.3, BMNH-1961.

1.23.4, BMNH-1961.1.23.8, BMNH-1961.11.1.2, BMNH-

1961.5.18.1, BMNH-1961.5.18.10, BMNH-1961.5.18.11,

BMNH-1961.5.18.11, BMNH-1961.5.18.12, BMNH-

1961.5.18.13, BMNH-1961.5.18.14, BMNH-1961.5.18.15,

BMNH-1961.5.18.16, BMNH-1961.5.18.17, BMNH-

1961.5.18.18, BMNH-1961.5.18.19, BMNH-1961.5.18.2,

BMNH-1961.5.18.23, BMNH-1961.5.18.25, BMNH-

1961.5.18.26, BMNH-1961.5.18.27, BMNH-1961.5.18.3,

BMNH-1961.5.18.30, BMNH-1961.5.18.31, BMNH-

1961.5.18.32, BMNH-1961.5.18.33, BMNH-1961.5.18.34,

BMNH-1961.5.18.35, BMNH-1961.5.18.36, BMNH-

1961.5.18.37, BMNH-1961.5.18.4, BMNH-1962.3.6.1,

BMNH-88.328, UCL-GMZ-LDUC-Z1630, UCL-GMZ-

Z1123, UCL-GMZ-Z1124, UCL-GMZ-Z2243, UCL-

GMZ-Z2298, MNHB-1502, MNHB-26346, MNHB-26584,

MNHB-28412, MNHB-31975, MNHN-1952.28, MNHN-

1966-03, MNHN-1978-47, MNHN-1978-48, MNHN-

1979-19, MNHN-1981-165, MNHN-1988-016, MNHN-

1991-723, MNHN-1991-724, MNHN-2004-301,

OUM13907, UMZC 7942, ZMA 14.514, ZMA 5845, UE-

NHC-XH13-4.1, UMZC 7941, UMZC 7943. Histriophoca

fasciata: BMNH-1963.7.19.6, BMNH-1965.7.19.8.

BMNH-1965.7.19.9, BMNH-1966.12.7.2. Hydrurga lep-

tonyx: BMNH-1843.1.8.4, BMNH-1846.4.15.23 (325.d),

BMNH-1846.4.15.24 (325.b), BMNH-1851.7.18.47

(325.h), BMNH-1854.8.25.5 (325.i), BMNH-1885.10.20.2

(325.n), BMNH-1893.9.14.1, BMNH-1901.1.4.15, BMNH-

1908.2.20.54, BMNH-1914.1.29.2, BMNH-1934.12.4.1,

BMNH-1938.12.3.2, BMNH-1939.1891, BMNH-

1939.2.11.10, BMNH-1939.2.11.11, BMNH-1939.2.11.12,

BMNH-1939.2.11.13, BMNH-1939.2.11.14, BMNH-

1939.2.11.15, BMNH-1939.2.11.16, BMNH-1939.2.11.17,

BMNH-1939.2.11.18, BMNH-1939.2.11.20, BMNH-

1939.2.11.21, BMNH-1939.2.11.22, BMNH-1939.2.11.23,

BMNH-1939.2.11.3, BMNH-1939.2.11.4, BMNH-

1939.2.11.8, BMNH-1939.2.25.1, BMNH-1939.2.25.2,

BMNH-1939.2.25.3, BMNH-1939.2.25.5, BMNH-

1939.2.25.7, BMNH-1939.2.265.4, BMNH-1939.4.29.5,

BMNH-1940.4.6.126, BMNH-1940.4.6.127, BMNH-

1940.4.6.14, BMNH-1940.4.6.142, BMNH-1940.4.6.146,

BMNH-1940.4.6.16, BMNH-1940.4.6.17, BMNH-

1940.4.6144, BMNH-1949.2.1.2, BMNH-1949.4.6.28,

BMNH-1958.4.24.7, BMNH-1959.12.17.4, BMNH-

1959.12.4.1, BMNH-1959.12.4.2, BMNH-1959.12.4.3,

UCL-GMZ-Z1125, UCL-GMZ-Z1646, UCL-GMZ-Z312,

UCL-GMZ-Z313, MNHB-12714, MNHB-36250, MNHB-

36253, MNHB-38317, MNHB-38321, MNHN-1884-1152,

MNHN-1952-194, MNHN-1952-195, MNHN-1955-173,

MNHN-1971-116, MNHN-1973-190, MNHN-1982-799,

ZMA 24.204. Leptonychotes weddellii: BMNH-1846.

4.25.22, BMNH-1908.2.20.11, BMNH-1908.2.20.13,

BMNH-1908.2.20.16, BMNH-1908.2.20.17, BMNH-

1908.2.20.18, BMNH-1908.2.20.2, BMNH-1908.2.20.20,

BMNH-1908.2.20.21, BMNH-1908.2.20.22, BMNH-

1908.2.20.23, BMNH-1908.2.20.25, BMNH-1908.2.20.26,

BMNH-1908.2.20.58, BMNH-1908.2.20.59, BMNH-1908.

2.20.6, BMNH-1908.2.20.60, BMNH-1908.2.20.62,

BMNH-1908.2.20.63, BMNH-1910.9.19.1, BMNH-

1940.4.6.108, BMNH-1940.4.6.109, BMNH-1940.4.6.110,

BMNH-1940.4.6.18, BMNH-1940.4.6.21, BMNH-

1940.4.6.22, BMNH-1940.4.6.23, BMNH-1940.4.6.24,

BMNH-1940.4.6.25, BMNH-1940.4.6.27, BMNH-

1940.4.6.32, BMNH-1940.4.6.33, BMNH-1940.4.6.35,

BMNH-1940.4.6.36, BMNH-1940.4.6.38, BMNH-

1940.4.6.39, BMNH-1940.4.6.41, BMNH-1940.4.6.44,

BMNH-1940.4.6.47, BMNH-1940.4.6.65, BMNH-1940.

Zoomorphology (2015) 134:325–338 335

123

Author's personal copy

4.6.72, BMNH-1940.4.6.73, BMNH-1940.4.6.99, BMNH-

1949.2.3.4, BMNH-1951.5.1.12, BMNH-1951.5.1.13,

BMNH-1951.5.1.2, BMNH-1951.5.1.3, BMNH-1951.

5.1.4, BMNH-1951.5.1.6, BMNH-1951.5.1.7, BMNH-

1951.5.16.5, BMNH-1951.5.8.3, BMNH-1951.5.8.4,

BMNH-1951.5.8.5, BMNH-1951.5.8.6, BMNH-

1951.5.8.8, BMNH-1951.8.28.16, BMNH-1951.8.28.17,

BMNH-1951.8.28.18, BMNH-1959.12.16.1, BMNH-

1959.12.16.10, BMNH-1959.12.16.11, BMNH-1959.

12.16.13, BMNH-1959.12.16.15, BMNH-1959.12.16.2,

BMNH-1959.12.16.3, BMNH-1959.12.16.4, BMNH-

1959.12.16.6, BMNH-1959.12.16.7, BMNH-1959.12.16.8,

BMNH-1959.12.6.5, BMNH-1959.5.16.1, BMNH-

1980.2.20.14, BMNH-1981.1394, BMNH-1981.1395,

BMNH-1981.1787, UCL-GMZ-Z1126, UCL-GMZ-Z1127,

MNHB-36268, MNHB-36269, MNHB-36270, MNHB-

36271, MNHB-36274, MNHB-36275, MNHB-36278,

MNHB-36281, MNHB-36282, MNHB-36283, MNHB-

36284, OUM4788, UMZC 7881, UMZC 7882, UMZC

7884. Lobodon carcinophaga: BMNH-1843.11.16.2,

BMNH-1844.10.29.18, BMNH-1844.11.16.4, BMNH-

1846.4.15.19, BMNH-1846.4.15.20, BMNH-1901.1.4.10,

BMNH-1908.2.10.36, BMNH-1908.2.20.32, BMNH-

1908.2.20.34, BMNH-1908.2.20.39, BMNH-1908.2.20.41,

BMNH-1908.2.20.43, BMNH-1910.9.19.3, BMNH-

1935.3.29.1, BMNH-1935.3.29.3, BMNH-1935.3.29.4,

BMNH-1939.2.4.1, BMNH-1939.2.4.3, BMNH-

1939.2.4.4, BMNH-1939.2.4.6, BMNH-1939.2.4.7,

BMNH-1939.2.4.8, BMNH-1939.4479, BMNH-

1940.4.6.10, BMNH-1940.4.6.11, BMNH-1940.4.6.111,

BMNH-1940.4.6.12, BMNH-1940.4.6.129, BMNH-

1940.4.6.13, BMNH-1940.4.6.132, BMNH-1940.4.6.49,

BMNH-1940.4.6.52, BMNH-1940.4.6.58, BMNH-

1940.4.6.63, BMNH-1940.4.6.67, BMNH-1940.4.6.7,

BMNH-1940.4.6.77, BMNH-1940.4.6.85, BMNH-

1940.4.6.86, BMNH-1940.4.6.88, BMNH-1940.4.6.89,

BMNH-1940.4.6.90, BMNH-1940.4.6.92, BMNH-

1940.4.6.93, BMNH-1949.4.6.8, BMNH-1951.6.25.4,

BMNH-1951.6.25.5, BMNH-1951.8.28.15, BMNH-

1956.12.8.6, BMNH-1957.3.12.1, BMNH-1957.8.15.1,

BMNH-1959.12.8.10, BMNH-1959.12.8.18, BMNH-

1959.12.8.2, BMNH-1959.12.8.3, BMNH-1959.12.8.5,

BMNH-1959.12.8.7, BMNH-1959.12.8.8, BMNH-

1959.12.8.9, BMNH-1981.1323, BMNH-1981.1324,

BMNH-1981.1325, BMNH-1981.1334, BMNH-

1981.1336, MNHB-36258, MNHB-36265, MNHB-38325,

MNHB-38329, MNHB-86629, MNHB-86630. Mirounga

angustirostris: BMNH-1966.10.24.3. Mirounga leonina:

UE-NHC-XH13-6.1, BMNH-1843.11.16.25 (334.b),

BMNH-1846.4.15.21 (33.4.c), BMNH-1876.1.28.82

334.e), BMNH-1894.11.17.1, BMNH-1912.9.28.1,

BMNH-1922.1.28.2, BMNH-1930.12.13.1, BMNH-

1933.8.12.1, BMNH-1939.4.29.1, BMNH-1939.4.29.4,

BMNH-1939.5.20.1, BMNH-1949.2.1.3, BMNH-

1949.2.3.11, BMNH-1949.2.3.12, BMNH-1949.2.3.14,

BMNH-1950.7.21.9, BMNH-1951.7.17.1, BMNH-

1951.7.17.3, BMNH-1951.7.17.5, BMNH-1951.7.17.7,

BMNH-1951.7.17.8, BMNH-1954.5.20.13, BMNH-

1954.5.20.21, BMNH-1954.5.20.22, BMNH-1954.5.20.23,

BMNH-1954.5.20.32, BMNH-1954.5.20.33, BMNH-

1954.5.20.34, BMNH-1954.5.20.37, BMNH-1954.5.20.38,

BMNH-1954.5.20.4, BMNH-1954.5.20.5, BMNH-

1954.5.20.52, BMNH-1954.5.20.55, BMNH-1954.5.20.58,

BMNH-1954.5.20.6, BMNH-1954.5.20.60, BMNH-

1954.5.20.61, BMNH-1954.5.20.61, BMNH-1954.5.20.62,

BMNH-1954.5.20.64, BMNH-1954.5.20.67, BMNH-

1954.5.20.67, BMNH-1954.5.20.68, BMNH-1954.5.20.7,

BMNH-1954.5.20.8, BMNH-1954.5.20.9, BMNH-

1955.11.24.3, BMNH-1959.12.17.2, BMNH-1959.12.17.3,

BMNH-1981.1265, BMNH-1981.1392, BMNH-334d,

BMNH-81.1381, BMNH-82200, BMNH-867, MNHB-

36227, MNHB-36230, MNHB-36238, MNHB-36239,

MNHB-36240, MNHB-36241, MNHB-36242, MNHB-

47195, MNHB-4857, MNHB-4894, MNHB-86281,

MNHN-1931-46, MNHN-1952-185, MNHN-1952-198,

MNHN-1955-170, MNHN-1955-171, MNHN-1972-142,

MNHN-1977-20, MNHN-1977-23, MNHN-1977-24,

MNHN-1983-045, ZMA 23.394. Monachus monachus:

BMNH-1863.4.1.1 (1421.a), BMNH-1892.11.7.1, BMNH-

1894.7.27.1 (1063.f), BMNH-1894.7.27.2 (1063.g),

BMNH-1951.4.17.1, MNHB-1520, MNHB-16083,

MNHB-47518, UMZC 7781. Neomonachus schauinslandi:

BMNH-1958.11.26.1. Neomonachus tropicalis: BMNH-

1989.11.5.1. Ommatophoca rossii: BMNH-1901.1.4.12,

BMNH-1901.1.4.13, BMNH-1908.2.20.47, BMNH-

1908.2.20.48, BMNH-1908.2.20.50, BMNH-1949.2.3.1,

BMNH-1949.9.2.3.2, BMNH-1951.4.24.1, BMNH-

1961.2.24.1, BMNH-1961.2.24.10, BMNH-1961.2.24.2,

BMNH-1961.2.24.4, BMNH-1961.2.24.7, BMNH-

1961.2.24.8, BMNH-1961.2.24.9, BMNH-1965.12.20.1,

MNHB-36245, MNHB-36246, MNHB-36247, MNHB-

36248. Pagophilus groenlandicus: BMNH-1843.10.7.9,

UCL-GMZ-Z304, BMNH-1843.6.23.5, BMNH-

1843.6.23.6, BMNH-1843.6.23.7, BMNH-1919.7.7.3262,

BMNH-1938.12.10.1, BMNH-1938.12.10.2, BMNH-

1938.12.10.3, BMNH-1951.11.28.2, BMNH-1963.7.19.1,

BMNH-1963.7.19.3, BMNH-1963.7.19.4, BMNH-

1963.7.19.5, BMNH-328.g, MNHN-1865-509, MNHN-

1985-2007, UMZC 8281, UMZC 8282, UMZC 8283,

UMZC 8284, UMZC 8285, ZMA 16.851, ZMA 16.852,

ZMA 20.229, ZMA 20.301, ZMA 20.323, ZMA 20.324,

ZMA 20.325, ZMA 20.326, ZMA 20.327, ZMA 20.331,

ZMA 20.334, ZMA 20.344, ZMA 20.347, ZMA 20.348,

ZMA 20.364, ZMA 20.367, ZMA 20.382, ZMA 20.406,

ZMA 20.41, ZMA 20.412, ZMA 20.413, ZMA 23.233,

ZMA 23.483, ZMA 24.694, ZMA 671, ZMA 699, ZMA

336 Zoomorphology (2015) 134:325–338

123

Author's personal copy

890, ZMA 893. Pusa hispida: BMNH-1004.c, BMNH-

1889.4.1.1., BMNH-1895.6.20.1, BMNH-1919.7.7.3264,

BMNH-1937.10.23.1, BMNH-1937.10.23.2, BMNH-

1937.10.23.3, BMNH-1937.10.23.5, BMNH-1937.10.23.6,

BMNH-1937.5.19.1, BMNH-1937.5.19.3, BMNH-

1938.11.26.6, BMNH-1938.11.26.7, BMNH-1938.12.10.5,

BMNH-1938.12.3.1, BMNH-1997.585, MNHN-1934-45,

OUM13899, UMZC 8201, UMZC 8204, UMZC 8205,

ZMA 17.183, ZMA 24.214, ZMA 24.348, ZMA 25.003,

ZMA 33.706, ZMA 898, ZMA 899. Phoca largha:

BMNH-1873.11.5.7, BMNH-1891.12.18.6, BMNH-

1965.7.19.12, BMNH-1965.7.19.13, BMNH-1965.7.19.14.

Phoca vitulina: BMNH-1004.f, BMNH-1868.3.21.1,

BMNH-1877.12.10.2, BMNH-1919.7.7.3260, BMNH-

1951.3.2.1, BMNH-1954.9.23.1, BMNH-329.d, BMNH-

1886.3.18.1, BMNH-1928.9.1.2, BMNH-329.i, UCL-

GMZ-Z2250, UCL-GMZ-Z303, MNHB-72452, MNHB-

72453, MNHB-72454, MNHB-72455, MNHB-85866,

MNHN-1880-771, MNHN-1894-524, MNHN-1902-560,

MNHN-1940-161, MNHN-1940-294, MNHN-1951-147,

MNHN-1983-792, MNHN-2007-411, UE-NHC-XH13-2.3,

UE-NHC-XH13-2.3a, UE-NHC-XH13-2.6, OUM 13871,

OUM 13875, OUM13870, OUM13873, OUM13902,

OUM7105, UMZC 8081, UMZC 8087, UMZC 8088,

UMZC 8089, UMZC 8090, UMZC 8092, UMZC 8095,

UMZC 8099, UMZC 8173, UMZC 8191, ZMA 23.556,

ZMA 23.558, ZMA 23.559, ZMA 23.56, ZMA 23.561,

ZMA 23.562, ZMA 23.712, ZMA 23.713, ZMA 23.716,

ZMA 23.717, ZMA 23.718, ZMA 23.721, ZMA 23.722,

ZMA 23.725, ZMA 23.726, ZMA 23.735, ZMA 23.758,

ZMA 23.759, ZMA 23.76, ZMA 23.771, ZMA 23.817,

ZMA 23.819, ZMA 23.823, ZMA 23.824. Pusa caspica:

BMNH-1963.7.19.10, BMNH-1963.7.19.11, BMNH-

1963.7.19.12, BMNH-1963.7.19.13, BMNH-1963.7.19.14,

BMNH-1963.7.19.15, BMNH-1965.7.19.1, BMNH-

1965.7.19.2, BMNH-1966.2.15.1, UMZC 8241. Pusa si-

birica: BMNH-1909.10.15.2, BMNH-1959.6.10.1,

BMNH-1960.12.21.1, BMNH-1963.7.19.8, BMNH-

1963.7.19.9, BMNH-1965.7.19.3, BMNH-1965.7.19.4,

BMNH-1965.9.6.1, BMNH-1965.9.6.2, MNHB-83441.

Zalophus californianus: ZMA 24.440, MNHN-1901-646,

MNHN-1879-271, MNHN-1882-190, MNHN-1879-269,

MNHN-1879-270, MNHN-1897-22, BMNH-1903.10.11.3,

BMNH-1903.10.11.4, BMNH-1952.12.19.1, BMNH-

1903.10.11.5, BMNH-1903.10.11.6, BMNH-1908.10.11.2.

Zalophus japonicus: BMNH-1973.3.12.1. Zalophus wolle-

baeki: MNHN-1962-1141, MNHN-1962-1142, MNHN-

1962-1143, MNHN-1962-1144, MNHN-1962-1145,

MNHN-1962-1146, MNHN-1962-1148, MNHN-1962-

1149, MNHN-1962-1155, MNHN-1962-1156, MNHN-

1962-1158, MNHN-1973-293. Zalophus sp.: BMNH-

1951.2.2.1, BMNH-1951.3.6.2, BMNH-1954.2.9.1, UCL-

GMZ-Z1076, UCL-GMZ-Z2238, UCL-GMZ-Z2342,

UCL-GMZ-Z301, MNHB-43163, MNHB-61617, MNHB-

72821, MNHB-92601, MNHN-1934-528, MNHN-1944-

276, UE-NHC-XH13-3.1, UE-NHC-XH13-3.1a, UE-NHC-

XH13-3.5, UE-NHC-XH13-3.6, UMZC 7122, ZMA

11.124, ZMA 11.125, ZMA 11.126, ZMA 1698, ZMA

17.819, ZMA 20.346, ZMA 21.902, ZMA 22.956, ZMA

667, ZMA 7384, MNHB-31399.

References

Abbott C, Verstraete FJM (2005) The dental pathology of northern

elephant seals (Mirounga angustirostris). J Comp Pathol

132:169–178

Adam PJ, Berta A (2002) Evolution of prey capture strategies and diet

in the Pinnipedimorpha (Mammalia, Carnivora). Oryctos

4:83–107

Armfield BA, Zheng Z, Bajpaj S, Vinyard CJ, Thewissen JGM (2013)

Development and evolution of the unique cetacean dentition.

PeerJ 1:e24

Barnes LG (1972) Miocene desmatophocinae (Mammalia: Carnivora)

from California. Univ Calif Publ Geol Sci 89:1–68

Bateson W (1894) Materials for the study of variation treated with

especial regard to discontinuity in the origin of species.

Macmillan and Co, London

Berta A (2002) Pinnipedia, overview. In: Perrin WF, Wursig B,

Thewissen JGM (eds) Encyclopedia of marine mammals.

Academic Press, San Diego, pp 903–911

Berta A, Wyss AR (1994) Pinniped phylogeny. Proc San Diego Soc

Nat Hist 29:33–56

Berta A, Sumich J, Kovaks K (2006) Marine mammals: evolutionary

biology. Academic Press, San Diego

Boessenecker RW (2011) New records of the fur seal Callorhinus

(Carnivora: Otariidae) from the Plio-Pleistocene Rio Dell

Formation of Northern California and comments on otariid

dental evolution. J Vertebr Paleontol 31:454–467

Briggs KT (1974) Dentition of the northern elephant seal. J Mammal

55:158–171

Burns JJ, Fay FH (1970) Comparative morphology of the skull of the

ribbon seal, Histriophoca fasciata, with remarks on systematics

of Phocidae. J Zool 161:363–394

Chiasson RB (1955) Dental abnormalities of the Alaskan fur seal.

J Mammal 36:562–564

Chiasson RB (1957) The dentition of the Alaskan fur seal. J Mammal

38:310–319

Committee on Taxonomy (2014) List of marine mammal

species and subspecies. Society for Marine Mammalogy,

www.marinemammalscience.org, consulted on 01 June 2014

Cruwys L, Friday A (2006) Visible supernumerary teeth in pinnipeds.

Polar Rec 42:83–85

Demere TA (1994) The family Odobenidae: a phylogenetic analysis

of fossil and living taxa. In: Berta A, Demere TA (eds)

Contributions in Marine Mammal Paleontology Honoring Frank

C. Whitmore, Jr. Proceeding of San Diego Society of Natural

History, vol 29, pp 99–123

Drehmer CJ, Ferigolo J (1996) Anomalias e patologias dentarias em

Arctocephalus G. Saint-Hilaire & Cuvier (Pinnipedia, Otariidae)

da costa do Rio Grande do Sul, Brasil. Rev Bras Zool 13:857–865

Drehmer CJ, Fabian ME, Menegheti JO (2004) Dental anomalies in

the Atlantic population of South American sea lion, Otaria

byronia (Pinnipedia: Otariidae): evolutionary implications and

ecological approach. Latin Am J Aquat Mamm 3:7–18

Zoomorphology (2015) 134:325–338 337

123

Author's personal copy

Drehmer CJ, Dornelles JE, Loch C (2009) Variations on the dental

formula of Otaria byronia de Blainville (Pinnipedia: Otariidae)

in the Pacific Ocean: a new kind of dental anomaly. Neotrop Biol

Conserv 4:21–35

Eastman JT, Coalson RE (1974) The digestive system of the Weddell

seal Leptonychotes weddelli—a review. In: Harrison RJ (ed)

Functional anatomy of marine mammals, vol 2. Academic Press,

London, pp 253–320

Fay FH (1982) Ecology and biology of the Pacific walrus, Odobenus

rosmarus divergens Illiger. North Am Fauna 74:1–279

Hall ER (1940) Supernumerary and missing teeth in wild mammals of

the orders Insectivora and Carnivora with some notes on disease.

J Dent Res 19:103–143

Hall BK (1984) Developmental mechanisms underlying the formation

of atavisms. Biol Rev Camb Philos Soc 59:89–124

Hamilton JE (1934) The southern sea lion Otaria byronia (De

Blainville). Discov Rep 8:269–318

Hillson S (2005) Teeth. Cambridge Manuals in Archaeology,

Cambridge

Hoff GL, Hoff DM (1996) Dental anomalies in mammals. In:

Fairbrother A, Locke LN, Hoff GL (eds) Noninfectious diseases

of wildlife. Iowa State University Press, Iowa, pp 100–108

Jernvall J (2000) Linking development with generation of novelty in

mammalian teeth. Proc Nat Acad Sci USA 97:2641–2645

Jones KE, Ruff CB, Goswami A (2013) Morphology and biome-

chanics of the pinniped jaw: mandibular evolution without

mastication. Anat Rec 296:1049–1063

King JE (1983) Seals of the world. Oxford University Press, Oxford

Konemann VS, Van Bree PJH (1997) Gebianomalien bei nordat-

lantischen Phociden (Mammalia, Phocidae). Zeitschrift fur

Saugetierkunde 62:71–85

Kubota K, Togawa S (1964) Numerical variations in the dentition of

some Pinnipeds. Anat Rec 150:487–502

Kubota K, Shibanai S, Kubota J, Togawa S (2000) Developmental

transition to monophyodonty in adaptation to marine life by the

northern fur seal, Callorhinus ursinus (Otariidae). Hist Biol

14:91–95

Loch C, Simoes-Lopes PC, Drehmer CJ (2010) Numerical anomalies

in the dentition of southern fur seals and sea lions. Zoologia

27:477–482

Loch C, Grando LJ, Kieser JA, Simoes-Lopes PC (2011) Dental

pathology in dolphins (Cetacea: Delphinidae) from the southern

coast of Brazil. Dis Aquat Org 94:225–234

Miles AEW, Grigson C (1990) Colyer’s variations and diseases of the

teeth of animals. Cambridge University Press, Cambridge

Miller EH (1975) Walrus ethology. I. The social role of tusks

and applications of multidimensional scaling. Can J Zool

53:590–613

Miller EH, Sung HC, Moulton VD, Miller GW, Finley JK, Stenson

GB (2007) Variation and integration of the simple mandibular

postcanine dentition in two species of phocid seal. J Mammal

88:1325–1334

Miyazaki N (2002) Teeth. In: Perrin WF, Wursig B, Thewissen JGM

(eds) Encyclopedia of marine mammals. Academic Press, San

Diego, pp 1127–1132

Nyakatura K, Bininda-Emonds ORP (2012) Updating the evolution-

ary history of Carnivora (Mammalia): a new species-level

supertree complete with divergence time estimates. BMC Biol

10:12

Repenning CA, Tedford RH (1977) Otarioid seals of the Neogene:

classification, historical zoogeography, and temporal correlation

of the sea lions and walruses from the North Pacific region. US

Government Printing Office, Washington

Richardson G, Russel KA (2000) A review of impacted permanent

maxillary cuspids-diagnosis and prevention. J Can Dent Assoc

66:497–501

Salazar-Ciudad I, Jernvall J (2010) A computational model of teeth

and the developmental origins of morphological variation.

Nature 464:583–586

Scheffer VB (1960) Dentition of the ribbon seal. Proc Zool Soc Lond

135:579–585

Scheffer VB, Kraus BS (1964) Dentition of the Northern fur seal.

Fishery Bull 63:293–342

Schuurs AHB, van Loveren C (2000) Double teeth: review of the

literature. ASDC J Dent Child 67:313–325

Sinai NL, Dadaian RH, Kass PH, Verstraete FJM (2014) Dental

pathology of the California sea lion (Zalophus californianus).

J Comp Pathol 151:113–121

Stewart REA, Stewart BE (1987) Mandibular dental anomalies of

Northwest Atlantic harp seals, Phoca groenlandica. Can J Zool

65:769–771

Stewart REA, Innes S, Stewart BE (1988) Mandibular dental

ontogeny of ringed seals (Phoca hispida). Mar Mamm Sci

14:221–230

Stiassny MLJ (1992) Atavisms, phylogenetic character reversals, and

the origin of evolutionary novelties. Neth J Zool 42:2–3

Suzuki M, Ohtaishi N, Nakane F (1990) Supernumerary postcanine

teeth in the kuril seal (Phoca vitulina stejnegeri), the largha seal

(Phoca largha) and the ribbon seal (Phoca fasciata). Jpn J Oral

Biol 32:323–329

Szuma E (1999) Dental abnormalities in the red fox Vulpes vulpes

from Poland. Acta Theriol 44:393–412

Vila C, Urios V, Castroviejo J (1993) Tooth losses and anomalies in

the wolf (Canis lupus). J Zool 71:968–971

Werth AJ (2006) Mandibular and dental variation and the evolution of

suction feeding in Odontoceti. J Mammal 87:579–588

Wolsan M (1984) The origin of extra teeth in mammals. Acta Theriol

29:128–133

338 Zoomorphology (2015) 134:325–338

123

Author's personal copy