ARTICLE

A PARTIAL SKELETON AND ISOLATED HUMERI OF NOTHOSAURUS (REPTILIA:EOSAUROPTERYGIA) FROM WINTERSWIJK, THE NETHERLANDS

CONSTANZE BICKELMANN*,† and P. MARTIN SANDERRheinische Friedrich-Wilhelms-Universität Bonn, Institut für Paläontologie, Nussallee 8, 53115 Bonn, Germany;

constanze.bickelmann@museum.hu-berlin.de

ABSTRACT—A rare partial postcranium and isolated humeri of Nothosaurus from the Lower Muschelkalk of Winter-swijk, The Netherlands are described. The partial skeleton consists of a vertebral column with ribs, pectoral girdleelements, and incomplete forelimbs. Because current species-level taxonomy of Nothosaurus is based only on features ofthe skull, we examined the postcranial morphology in detail in order to assign the skeleton to a valid species. We focusedon the humerus because this bone generally shows a complex morphology in Lower Muschelkalk Nothosaurus. Threedifferent humerus morphotypes were recognized in the Winterswijk material, which were also seen among humeri fromother Lower and lowermost Middle Muschelkalk localities such as Rüdersdorf and Oberdorla (both in Germany), andGogolin (Poland). Morphotype I is characterized by a slender appearance with a bulky proximal end. The preaxial andpostaxial edges of the shaft are very distinct, and the distal end is fan-shaped. Morphotype II is rather small and gracilewith the distal end being only slightly fan-shaped. Morphotype III is rather large with an especially massive proximal end,and the distal end is thick and shovel-like. Ontogenetic variation could also be recognized within the morphotypes. Onesmall humerus from Oberdorla belongs to a juvenile and cannot be assigned to a specific morphotype. Type II humeribelong to the N. winterswijkensis-N. marchicus clade. Type III may represent a sexual morph of type II humeri and typeI a new species of Nothosaurus, or both may pertain to the nothosaurian Germanosaurus and/or the eosauropterygianCymatosaurus.

INTRODUCTION

Nothosaurs are reported from Middle and lower Upper Tri-assic localities in Europe, Israel, Tunisia, and China (Rieppel,1997; Lin and Rieppel, 1998; Rieppel, 1998a; Rieppel et al., 1999;Rieppel, 2000). However, only a few fossil sites have yieldedarticulated postcranial skeletons, such as the black shale locali-ties in the Southern Alps and China. Most nothosaur materialdoes not come from these black shales, but from the marinecarbonates of the Muschelkalk and its equivalents. Usually, thesedeposits yield only skulls and isolated bones of marine reptiles(Rieppel, 2000). The ‘Steengroeve’ locality at Winterswijk, TheNetherlands, is one of the rare exceptions. In the middle LowerMuschelkalk sediments cropping out at this locality, articulatedor associated postcranial skeletons of marine reptiles of an as-tonishingly good three-dimensional quality are found. This in-cludes skeletons of Anarosaurus heterodontus (Hooijer, 1959;Oosterink, 1986; Oosterink et al., 2003), Dactylosaurus cf. graci-lis (Oosterink et al., 2003), Nothosaurus sp. (Oosterink, 1986;Oosterink and Diepenbroek, 1990; Oosterink et al., 2003), andthe enigmatic Saurosphargis, whereas Placodus sp. (Oosterink,1986; Oosterink and Diepenbroek, 1990; Oosterink et al., 2003)and Tanystropheus sp. (Oosterink, 1986; Oosterink et al., 2003)are represented by isolated bones and teeth. It is not only thegood preservation of marine reptile skeletons, but also the goodpreservation of tracks made by terrestrial reptiles (Rynchosau-roides peabodyi [Faber, 1958], Procolophonichnium haar-muehlensis [Holst et al., 1970]) preserved in cyanobacterial mats,

which make the locality so extraordinary and valuable. Remainsof sharks, coelacanths, and Saurichthys as well as isolated bonesof capitosaurid amphibians have also been found at this locality,along with invertebrates and trace fossils (Oosterink, 1986; Oos-terink et al., 2003).

Most of the fossil vertebrate material from Winterswijk wasrecovered by private collectors (especially by members of the‘Werkgroep Muschelkalk Winterswijk’) and still remains in theircollections, although some of the better preserved specimenswere acquired by the National Museum of Natural History Natu-ralis, Leiden, and the Natuurmuseum Enschede, both in TheNetherlands. In addition, a new species of Nothosaurus, N. win-terswijkensis (Albers and Rieppel, 2003), was recently describedfrom bed IX of the local stratigraphy, while another specimenwas ascribed to N. marchicus (Koken, 1893), although it alsoexhibits features of N. winterswijkensis (Albers, 2005). Addition-ally, there exists an as yet undescribed Nothosaurus species rep-resented by a lower jaw (NMNHL St 445913, assigned to Notho-saurus cf. raabi by Hooijer, 1959) along with material in privatecollections, which is much larger than the above mentionedspecimens.

After many decades of long-lasting debates on the classifica-tion of sauropterygians, a comprehensive handbook with exten-sive descriptions was published by Rieppel (2000), in whichnothosaur classification is based exclusively on features of theskull. So far, the genus Nothosaurus includes nine valid species.

The present work focuses on a partial articulated postcranium(NMNHL St 87289) briefly described and illustrated by Hooijer(1959) as Nothosaurus sp. because of the similarity of its humerusto that of Nothosaurus raabi (Schröder, 1914, later synonymizedwith N. marchicus, Koken, 1893). It was the first recorded dis-covery of Nothosaurus from this locality. Also, this find is re-markable as only three other specimens of Nothosaurus from the

*Corresponding author. Current address: Humboldt-Universität zuBerlin, Museum für Naturkunde, Abteilung für Forschung, Invaliden-strasse 43, 10115 Berlin, Germany

Journal of Vertebrate Paleontology 28(2):326–338, June 2008© 2008 by the Society of Vertebrate Paleontology

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Germanic Muschelkalk preserve an articulated postcranial skel-eton: the holotype of Nothosaurus raabi (MB.I.007.18), the ho-lotype of Nothosaurus jagisteus (SMNS 56618), and the holotypeof Nothosaurus mirabilis (UMO 100). The holotype ofParanothosaurus amsleri (PIMUZ T 4829, later synonymizedwith Nothosaurus giganteus) is also known from a complete skel-eton, but this specimen is from the Monte San Giorgio blackshales and not from the Germanic Muschelkalk. The preserva-tion of the forelimb is also notable, as only three other manus ofwestern Tethys Nothosaurus are known so far (holotype ofNothosaurus raabi [MB.I.007.18], the holotype of Nothosaurusjagisteus [SMNS 56618], and the holotype of Paranothosaurusamsleri [PIMUZ T 4829]). Because NMNHL St 87289 is lackinga skull and nothosaur phylogeny is based on skull features(Rieppel, 2000), it was necessary to find diagnostic features inother skeletal elements in order to assign this partial skeleton toa valid species. We focused on the humeri because nothosaurhumeri from the Lower and lowermost Middle Muschelkalkshow a complex morphology, as opposed to those from the Up-per Muschelkalk, which have a much simpler shape. For com-parison, we studied isolated humeri from Winterswijk and threeother Lower and lowermost Middle Muschelkalk localities inEurope. The examination of these led to the recognition of threedifferent humerus morphotypes. Due to several anatomical fea-tures, all but one humerus (of 16 specimens) could be assigned toone of the three different morphotypes, and within these typesthey could then also be ordered into ontogenetic series. The onlyhumerus that could not be assigned to a morphotype belongs toa juvenile.

Institutional Abbreviations—BGR Berlin, Bundesanstalt fürGeowissenschaften und Rohstoffe, Dienstbereich Berlin, Berlin,Germany; CHW, Private collection Herman Winkelhorst,Aalten, The Netherlands; MB, Museum für Naturkunde, Hum-boldt-Universität zu Berlin, Berlin, Germany; MHI, Mus-chelkalkmuseum Hagdorn, Ingelfingen, Germany; NME,Natuurmuseum Enschede, Enschede, The Netherlands;NMNHL, National Museum of Natural History Naturalis,Leiden, The Netherlands; UMO, Urwelt-Museum Oberfranken,Bayreuth, Germany; PIMUZ, Paläontologisches Institut undMuseum der Universität Zürich, Zürich, Switzerland; SMNS,Staatliches Museum für Naturkunde Stuttgart, Stuttgart, Ger-many.

Anatomical Abbreviations—cl, clavicle; dc 4, distal carpal 4;dg, deltopectoral groove; dpc, deltopectoral crest; ect, ectepicon-dyle; ect. gr, ectepicondylar groove; ent. f, entepicondylar fora-men; fac. m, facet margin; hu, humerus; g, gastral rib; ind, in-dentation; int, intermedium; l, left; ldi, latissimus dorsi insertion;mc 1-5, metacarpals 1-5; mf, midshaft foramen; n, no; pa, pittedarea; pes, preaxial edge of the shaft; ph, phalange; po. e, post-axial edge; r, rib; ra, radius; ri, right; sc, scapula; ul, ulna; uln,ulnare; v, vertebra; well, well developed; y, yes.

STRATIGRAPHY

Stratigraphy of the Winterswijk Locality

The locality of Winterswijk, The Netherlands, is the mostnorthwestern locality with Lower Muschelkalk deposits exposedat the surface. The locality is an active quarry, which has been inoperation since 1935. It is run by ‘Ankerpoort B.V.’, which ex-ploits limestone for the production of asphalt gravel and fertil-izers. The presence of bluish-gray limestones and marls, yellow-ish dolomites and black-grayish mudstones indicate a shallowmarine and nearshore environment. Sediments with ripple marksand polygonal mud cracks even indicate a tidal flat facies, withthe mud crack beds representing algeal laminates produced bycyanobacteria stabilizing the sediment surface. Bones of Mus-chelkalk reptiles occur accumulated in specific layers, for ex-ample in bed IX bones of N. winterswijkensis.

Stratigraphically, the rocks represent the middle Lower Mus-chelkalk (H. Hagdorn, pers. comm.). Thus, these beds areyounger than the famous Lower Gogolin beds (basal LowerMuschelkalk) but are older than those of Rüdersdorf and Ober-dorla. A discrete Winterswijk Formation has recently been pro-posed to the Permian-Triassic Subcomission of the GermanStratigraphic Comission (H. Hagdorn, pers. comm.).

Stratigraphy of the Rüdersdorf Nothosaur Beds

The Rüdersdorf locality near Berlin, Germany, is an outcropwhere the entire Lower and Middle, and the basal part of theUpper Muschelkalk, is exposed (Hagdorn, 1991). The dolomiticmarls of the orbicularis Beds (lowermost Middle Muschelkalk)contain a thin bone bed layer that has yielded much isolatedmarine reptile material, especially nothosaurs (Hagdorn, 1991;Hagdorn and Rieppel, 1998). The most prominent but excep-tional find is the articulated skeleton of the holotype of Notho-saurus raabi (Schröder, 1914).

Stratigraphy of the Oberdorla Nothosaur Beds

Stratigraphically, the famous ‘Oberdorla Schaumkalk’ belongsto the lowermost Middle Muschelkalk (Hagdorn and Rieppel,1998). Thus, the finds from this locality are nearly the same ageas those from the Rüdersdorf locality. The limestones from Jena(‘Saurierkalke von Jena’) containing the nothosaurian bones il-lustrated by H. v. Meyer in the 19th century (Meyer, 1847-1855)are also of the same age.

Stratigraphy of the Gogolin Locality

The locality of Gogolin, Silesia, Poland, exposes the lower-most sediments of the Silesian Muschelkalk. The sediments be-long to the basal Lower Muschelkalk and correspond with theUpper Röt Formation in age (Hagdorn and Rieppel, 1998).

SYSTEMATIC PALEONTOLOGY

SAUROPTERYGIA Owen, 1860EOSAUROPTERYGIA Rieppel, 1994

NOTHOSAURIDAE Baur, 1889NOTHOSAURUS Münster, 1834

Type Species—Nothosaurus mirabilis Münster, 1834.Included Species—N. giganteus Münster, 1834, N. mirabilis

Münster, 1834, N. marchicus Koken, 1893, N. juvenilis Edinger,1921, N. edingerae Schultze, 1970, N. tchernovi Haas, 1980, N.haasi Rieppel et al., 1997, N. jagisteus Rieppel, 2001, N. winter-swijkensis Albers and Rieppel, 2003.

Diagnosis—For skull characters see Rieppel (2000). Vertebralcentrum with platycoelous vertebrae (Rieppel, 2000); sacral ribswithout distinct expansion of distal end (Rieppel, 1998b); ribswith slightly pachyostotic proximal articular heads (Rieppel andHagdorn, 1997); relatively large coracoids (Rieppel, 2001); char-acteristically curved humerus with straight preaxial angle andpostaxial concavity (Romer, 1956; Storrs, 1991); distinct delto-pectoral crest and latissimus dorsi insertion on the proximal hu-merus head (Rieppel et al., 1999); entepicondylar foramenmostly present (Rieppel, 2000); ectepicondyle not markedly de-veloped (Rieppel et al., 1999); phalangeal formula in the manus:2-3-4-5-3 (Rieppel, 2000).

Distribution—Middle to lower Upper Triassic; westernThetyan faunal province and new finds from the eastern Thetyanfaunal province (China).

Remarks—The diagnosis is a synthesis of postcranial charac-ters from various publications. This was done because so far nophylogenetic analysis of the species of Nothosaurus includingpostcranial characters is available.

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DESCRIPTION

Material

An incomplete articulated postcranium (NMNHL St 87289),as well as several humeri: Type I humeri (BGR X 13072; MHI1875; NMNHL St 36375; NMNHL St 87289; SMNS 16253), TypeII humeri (CHW 56; MB.I.007.18; MB.R.162.3; MB.R.162.2;NME 480000126), Type III humeri (MB.R.159; MB.R.162.1;MB.R.539; MB.R.542; NMNHL St 445914), and a juvenile hu-merus (MB.R.162.4).

NMNHL St 87289

The specimen is preserved in ventral view (Fig. 1). Its pre-served length is 345 mm, lacking the skull and the posterior partincluding the pelvic girdle, hind limbs and tail. The specimen isassigned to Nothosaurus sp. (Hooijer, 1959).

Trunk—The preserved vertebral column comprises ninenearly complete vertebrae (Fig. 1). These are identified as dorsalvertebrae because of their location in the articulated skeletonand their short neural spines that are typical for Nothosaurusvertebrae from the Lower Muschelkalk (Romer, 1956; Rieppeland Hagdorn, 1997). As in all nothosaurs, the vertebral centraare platycoelous (Rieppel, 2000). They are slightly constricted inthe middle and reveal a smooth surface. On average, they havea length of 14 mm and a minimum transverse width of 12 mm.

On the articular surface, the diameter of the centra amounts to13 mm on average. The total height of the vertebra including theneural spine averages 33 mm.

The neural spines can be seen in lateral view by separating thetwo parts of the slab containing the skeleton. In nothosaurs, theneural spine usually slants slightly backwards and shows no dor-sal expansion (Rieppel and Hagdorn, 1997). Here, four of theneural spines are well preserved and look alike. On average, theyare 15 mm wide and 12 mm high. Additionally, they show strik-ing ‘saw-cut’ rugosities, which are also present in Augustasaurus(Sander et al., 1997), Endennasaurus (Müller et al., 2005), Pa-chystropheus (Storrs et al., 1996), and other aquatic reptiles.These cover approximately the top third of each neural spine.

A few transverse processes are found next to the vertebralcolumn. Usually, they are fused laterally with the neural arches(Rieppel, 2001), but in this specimen they all are broken off dueto the crack in the slab. Their appearance is cylindrical and com-pact. On average, they are 5 mm long and reach a diameter of 7mm.

Ribs—According to their position in the articulated skeleton,the ribs that are preserved can be identified as dorsal ribs. In allnothosaurs, dorsal ribs are unicipital and articulate with thetransverse processes (Rieppel, 2001). As seen in Figure 1, onlythree ribs are preserved for their entire length (68 mm + 76 mm+ 85 mm, measured along their outer curvature). The proximalarticular head is massive and slightly pachyostotic as in all notho-saurs (Rieppel and Hagdorn, 1997). It has an oval proximal ar-ticular surface, which is oriented anteroposteriorly and averages10 mm in diameter. The head continues into a distinctly arched‘shoulder’ region (Rieppel, 2001), a smooth shaft and a moder-ately expanded distal end that shows the same ‘saw-cut’ rugosi-ties seen on the neural spines.

Gastral Ribs—The gastral rib basket is well developed in allstem-group sauropterygians (Rieppel, 2000). Here, only frag-ments remain (Fig. 1), including some pieces covering the manusand one complete intermediate gastral rib segment sensu Riep-pel (2001), lying on the left side of the posterior portion of thevertebral column.

Pectoral Girdle—NMNHL St 87289 preserves a completeright scapula and a fragmentary bone embedded on the right sideof the vertebral column (Fig. 1), which is interpreted here as theleft clavicle.

The relatively short scapula is associated with the right fore-

limb (Fig. 1). It has the characteristic nothosaurian shape, ven-trally displaying the broad and ventrally expanded glenoidal por-tion sensu Rieppel (2000). Dorsally, the narrow, posterodorsallytrending process replaces the usual dorsal blade (Schmidt, 1987).The glenoid is a small cavity on the scapula and the coracoidwhere the humerus articulates with the pectoral girdle. The totallength of the scapula is 62 mm, with the glenoidal part measuring30 mm and the process measuring 34 mm. The suture betweenscapula and coracoid is well developed as is the coracoid fora-men (Fig. 1) (Rieppel, 2000).

The clavicle in NMNHL St 87289 is only fragmentarily pre-served (Fig. 1). The left medical part of the partial fragmentarybone (width: 20 mm) is the central portion of the left clavicle andexposes the typical curved surface. The right lateral part of thefragmentary bone is not definitively identifiable. Either it is theposterodorsal process of the left clavicle or it is the posterior partof the left coracoid. The bone is highly flattened dorsoventrally(Fig. 1).

Forelimbs—Both forelimbs are partially preserved (Fig. 1).The right humerus is completely preserved (Fig. 2C-G) and wasprepared out of the sediment for this study. Overall, the humerushas a slender appearance. It shows the characteristically curvedsauropterygian structure with the concavity on the postaxial side(Fig. 2C, D, F) (Romer, 1956; Storrs, 1991). The preaxial side hasa straight margin. The total length of the humerus is 107 mm.The proximal head is oval in cross-section with an anteroposte-rior orientation and measures 22 mm in width. In Nothosaurus,the boundary between bone covered by cartilage and bone notcovered by cartilage (periosteal bone) is very distinct and wastermed the proximal/distal facet margin on the articular ends ofthe long bones.

Adjacent to the proximal articular head, there is a distinctdeltopectoral crest extending distally along the postaxial marginand projecting ventrally for about one third of the length of thehumerus (Rieppel et al., 1999). It has a highly ornamented sur-face, indicating that there had been strong muscles attached (Fig.2C, D). On the most proximal tip of the deltopectoral crest, thereis a small indentation (Fig. 2C, D). Dorsally, there is a distinctcrest for the insertion of the latissimus dorsi muscle (Fig. 2F). Itextends distally from the proximal head. The latissimus dorsi is agroup of muscles that originate on the dorsolateral body wall andinsert onto the humerus (Rieppel et al., 1999). In specimenNMNHL St 87289, the deltopectoral crest on the ventral side andthe latissimus dorsi insertion on the dorsal side are strongly de-veloped. Dorsally, next to the latissimus dorsi insertion, there isan area where the surface is pitted, indicating an area of muscleattachment (Fig. 2F). The shaft of the humerus is triangular incross-section, resulting from the sharp edge of the preaxial mar-gin. Measured anteroposteriorly, the minimal shaft width is 16mm. The convex margin serves as the articular facet for radiusand ulna (Romer and Parsons, 1986). The distal end of the hu-merus is dorsoventrally flattened and expanded with a convexdistal margin. The distal width of the humerus is 29 mm. Anentepicondylar foramen, which is variably present in sauropte-rygian taxa (Rieppel, 2000), is not seen in specimen NMNHL St87289. Dorsally, the ectepicondyle is not markedly developed, asis also the case in other sauropterygians (Rieppel, 2001), but isnonetheless present and serves for the attachment of the strongflexor muscles of the forearm (Romer, 1956; Starck, 1979). Inbetween the ectepicondyle and the preaxial margin is the ectepi-condylar groove, through which the radial nerve and blood ves-sels passed (Fig. 2C, D, F). A true ectepicondylar foramen isalways absent in the sauropterygian lineage (Rieppel, 2000).Deep and long grooves (referred to as rugosities in this study)are seen all over the bone, mainly at the ends, indicating it be-longed to an individual of a relatively advanced age (Tumarkin-Deratzian et al., 2006). The humerus type seen in NMNHL St87289 is designated as type I.

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FIGURE 1. Nothosaurus sp., partial skeleton. Photograph (A) and drawing (B) of specimen NMNHL St 87289 from Winterswijk, The Netherlands,in ventral view. Diagonal hatching indicates broken bone. Scale bar equals 50 mm.

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FIGURE 2. Nothosaurus sp. Humerus morphotype I. Photograph (A) and drawing (B) of specimen NMNHL St 36375 from Winterswijk, TheNetherlands, in ventral view. Photograph (C) and drawings of specimen NMNHL St 87289 from Winterswijk, The Netherlands, in ventral (D),postaxial (E), dorsal (F) and proximal (G) view. Photograph (H) and drawing (I) of specimen BGR X 13072 from Rüdersdorf in ventral view.Proximal is at the top. Diagonal hatching indicates broken bone. All images are to the same scale, and each scale bar equals 10 mm.

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The right ulna is complete (Fig. 1). It is a dorsoventrally flat-tened bone with both proximal and distal ends being clearlyexpanded. In total, it is 55 mm long and the shaft is oval incross-section. The postaxial margin is straight. Preaxially, in themiddle of the shaft, there is a small section missing. Both endsare somewhat more flattened than the shaft and have concavemargins, with the proximal end being slightly wider (21 mm) thanthe distal end (19 mm). As seen in Fig. 1, only the proximal partof the left ulna is preserved. Its concave preaxial margin mea-sures 22 mm in length. In all other respects, the left ulna has thesame appearance as the right one.

As seen in Figure 1, the radius is a small bone with a totallength of 54 mm. The slightly constricted shaft measures 7 mm inwidth. On the preaxial side, there is an oblong indentation that is15 mm long whose function is not clear. The proximal part of theradius is slightly broadened and very massive (width: 15 mm).The distal end is only slightly expanded, measuring 10 mm inwidth. At both ends, there are shallow concavities that are likelyto have served for the attachment of muscles. The left radius isonly partially preserved (Fig. 1), lacking the distal end. The mini-mal width of the shaft is 8 mm. The oblong indentation on thepreaxial side also measures 15 mm in length.

Preparation exposed an incomplete but articulated left manus,which consists of three carpals, five metacarpals, and a few pha-langes (Fig. 1). The three carpals (Fig. 1) are interpreted as theulnare, the intermedium, and the distal carpal 4 (dc 4) (Rieppeland Wild, 1996). The ulnare and dc 4 are rounded and dorso-ventrally flattened. Dc 4 is much smaller (7 mm in diameter) thanthe ulnare (13 mm in diameter). Only dc 4 displays a margincomposed completely of unfinished bone. In the ulnare, a smallpart of the margin exposes finished bone. The intermedium,which has a semilunar shape, is the largest of the three carpals. Itis 18 mm wide and 12 mm long. Here, all but the proximal marginof the bone is unfinished.

The metacarpals (mc) are small, elongate bones with a narrowshaft and slightly expanded ends (Fig. 1). They are preserved inarticulation (mc 1-5). Farthest preaxially is mc 1, which is thesmallest (length: 12 mm), followed by three larger bones (mc 2-4with a length of 21 mm, 24 mm, and 23 mm) and the small mc 5(length: 17 mm). Mc 2-5 are similar in appearance, with a con-stricted shaft (average width: 3 mm) and expanded and dorso-ventrally flattened proximal (average width: 8 mm) and distalends (average width: 6 mm). Mc 1 lacks the shaft and an ex-panded distal end seen in the other metacarpals. Its proximalpart is 8 mm wide.

Distal to the metacarpals, nine phalanges are scattered on theslab (Fig. 1). These are small, dorsoventrally flattened boneswith a short shaft (average width: 3 mm) and only moderatelyexpanded ends (average width: 4 mm). Their total length rangesfrom 3 mm to 8 mm. As far as it is known, Nothosaurus has aphalangeal formula of 2-3-4-5-3 in the manus (Rieppel, 2000). Inthis specimen, there is only a count of 2-3-3-1-0.

Other Humeri

As mentioned previously, several humeri from Lower Mus-chelkalk outcrops were studied and found to fall into three mor-photypes. Additionally, one humerus was found to be that of ajuvenile. These three morphotypes can be distinguished by theiroverall appearance as well as by the shape of the proximal anddistal ends. Furthermore, ontogentic stages, based on four fea-tures, were observed ranging from subadult to old specimens.These series are found within in the morphotypes and are ac-companied by size increase. Therefore, the humeri are describedby morphotype and the descriptions within these types are sortedontogenetically.

Type I Humeri—All humeri assigned to type I (Fig. 2) have anoverall slender appearance. The proximal end is bulkier than the

rest of the humerus. The articular facet margins are distinct. Theshaft is very narrow in proportion to the proximal head. All typeI humeri show a very straight preaxial edge of the shaft and avery pronounced postaxial concavity resulting in a triangularcross-section. The distal end is strongly flattened dorsoventrally,broadened, and fan-shaped. An ectepicondylar groove is welldeveloped. Type I humeri range in length from 78 to 129 mm.

One humerus from the Gogolin locality (MHI 1875) was as-signed to this type (Table 1+2). Based on the ontogeneticchanges within the three humerus types, this specimen is theyoungest representative of type I.

NMNHL St 36375 from the locality of Winterswijk is onlypartially preserved, as seen in Fig. 2A, B. The shaft and the distalpart of this left humerus are the cast of a natural mold where thebone had fallen out of the rock. This humerus has a slenderappearance. Length, however, cannot be measured exactly asparts of the distal facet are broken off (approximate length: 95mm). The proximal head is rounded and measures 20 mm indiameter. The deltopectoral crest is fused with the margin of theproximal facet, which exposes a spongy surface. The deltopec-toral crest is not markedly set off. The latissimus dorsi insertionis also not well developed. The shaft is triangular in cross-sectionand measures 14 mm in width. Its preaxial edge is distinct andstraight. There is a distinct postaxial edge of the shaft, indicatingthe attachment of two muscle groups that meet along this edge.An entepicondylar foramen appears to be recorded by the cast,but only on the ventral side. Therefore it is unclear if this is a realentepicondylar foramen. The ectepicondylar groove is weaklydeveloped. Rugosities all over the bone are also weakly devel-oped.

In terms of ontogenetic stages, SMNS 16253 from the Gogolinlocality is the next older specimen (Tables 1, 2). The humerus ofspecimen NMNHL St 87289 shows an intermediate ontogeneticstage.

This right humerus BGR X 13072 (Fig. 2H, I), which comesfrom the locality of Rüdersdorf, is very large, with a length of 129mm. It has an overall slender appearance. As parts are brokenoff, the width of the proximal end cannot be measured reliably.The deltopectoral crest and the latissimus dorsi insertion aremarkedly developed and heavily set off. The deltopectoral crestexposes a small indentation at its most proximal tip. There isanother indentation on the preaxial side of the distal end. On theproximal dorsal side, there is the same pitted area seen on hu-merus NMNHL St 87289. The preaxial edge of the shaft is ex-tremely straight. The shaft is triangular in cross-section and 19mm wide. There is also a weakly developed postaxial edge of theshaft, where two muscle groups would have met. The distal endof this humerus measures 30 mm in width. An entepicondylarforamen is not present, but the ectepicondylar groove is welldeveloped. Rugosities all over the bone are heavily developed.

A humerus of type I was described in the monograph withdrawings of Muschelkalk reptiles published by von Meyer(Meyer, 1847-1855). It is depicted on plate 32, fig. 11, and comesfrom the locality of Mertendorf, near Freyburg an der Unstrut,Germany. An entepicondylar foramen is also missing in this hu-merus, but von Meyer (1847-1855) concluded after intense studythat this was due to individual variation.

Type II Humeri—In the following, three humeri assigned totype II (Fig. 3) are illustrated and described in detail and inontogenetic order. Several other humeri were also assigned tothis type (Tables 1, 2).

Type II humeri (Fig. 3) have an overall slender and gracileappearance. They are also rather small, ranging from 66 mm to105 mm in length. The proximal part appears gracile, and itsfacet margin is distinct. In ventral view, the proximal head showsthe same narrowness as the shaft. In all specimens, the deltopec-toral crest is not set off but its proximal tip is fused with themargin of the proximal articular facet. The latissimus dorsi in-

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sertion on the dorsal side is well developed but not set off fromthe proximal articular surface. All specimens also have a shaft inwhich the preaxial edge is never as straight as that of type Ihumeri. The distal end of the humerus is only slightly broadenedand fan-shaped, and in some specimens this area is depressed inthe middle. In all specimens, an entepicondylar foramen is pre-sent. Distally, the ectepicondylar groove is identifiable on eachhumerus. No marked rugosities are developed in any specimen.

In terms of ontogenetic stages, the humeri of MB.I.007.18(Tables 1, 2), which is the holotype of Nothosaurus raabi andcomes from the Rüdersdorf locality, is the youngest specimenthat could be assigned to this type.

The next largest specimen (CHW 56) is a right humerus, com-ing from the Winterswijk locality, and is only exposed in ventral(Fig. 3A, B) and postaxial view (Fig. 3C), as it remains partiallyembedded in the sediment. Unlike any of the other humeri stud-ied, the specimen has suffered moderate crushing in the dorso-ventral plane. CHW 56 is 87 mm long, and the proximal end hasa width of 17 mm. The deltopectoral crest reaches to the marginof the proximal articular head. The preaxial edge of the shaft isidentifiable but not very pronounced. The shaft measures 14 mmin width. Postaxially, there is a small midshaft foramen (Fig. 3C).Here, a blood vessel extended into the bone. On the distal end ofthe bone (width: 30 mm), there is a small indentation on thepreaxial side. An entepicondylar foramen is well developed(length: 10 mm, maximal width: 3 mm), as is an ectepicondylargroove preaxially. The surface of both articular facets is spongy.Despite the crushing, the humerus shows several original rugosi-ties.

The next largest humerus (MB.R.162.3) comes from the local-ity of Oberdorla and is a right one (Fig. 3D–G). It measures 90mm in length and has a proximal width of 21 mm. The deltopec-toral crest is fused with the proximal facet margin (Fig. 3D, E),as is the latissimus dorsi insertion (Fig. 3F). The preaxial edge ofthe shaft is not very distinct and bears a small indentation proxi-mally. The shaft is triangular in cross-section and 18 mm wide.As seen in Fig. 3F, there is also a small postaxial midshaft fora-men. Here, it is located further dorsally than in CHW 56. Thedistal end of MB.R.162.3 is slightly broadened and measures 31mm in width. There is an entepicondylar foramen. The groove ofthe entepicondylar foramen is distinct and 6 mm in length and 2mm in width. The ectepicondylar groove is indistinct and notnotched distally. There are rather weakly developed rugositiesover the entire bone surface.

Both humeri of specimen NME 480000126 are partially pre-served (Fig. 3H-M). Based on the associated skull, the specimen

was assigned to Nothosaurus winterswijkensis by Albers andRieppel (2003). It was found at the locality of Winterswijk.

The right humerus (Fig. 3H–K) is represented by the proximaland the distal end. The proximal part (Fig. 3H, J) is slender andmeasures 22 mm in width. A distinct preaxial edge appears tohave been present on the shaft. As parts are broken off, it is notclear if the deltopectoral crest fuses with the proximal articularmargin. The latissimus dorsi insertion is identifiable on the dor-sal side. Preaxially, a small indentation is developed. Also, theshaft shows an indication of a weakly developed postaxial edge.The distal end (Fig. 3I, K) is 24 mm wide. An entepicondylarforamen is present, but its length cannot be measured because itis truncated by a fracture. Also, due to incomplete preservation,an ectepicondylar groove could not be identified.

The left humerus is only represented by the proximal head(width: 22 mm) (Fig. 3L, M). The ventral side shows the delto-pectoral crest being fused with the margin of the articular headand being heavily ornamented. Also, the latissimus dorsi inser-tion on the dorsal side is fused with the facet margin and mark-edly sculptured. All over the bone, there are moderately devel-oped rugosities.

Although these two humeri are rather fragmentary, they canbe definitely assigned to type II. Their dimensions fit the patternand their proximal heads look the same. Also, the distal end isslightly broadened and fan-shaped, as in all other type II humeri.

In terms of individual age, MB.R.162.2 (Tables 1, 2) from theOberdorla locality, which could also be assigned to this type, isthe oldest of all the studied type II humeri.

The humerus depicted on plate 32, fig. 12, in von Meyer’scompendium (Meyer, 1847-1855) is also a type II humerus. It isas slender and gracile as the type II humeri described above, andan entepicondylar foramen is well developed. The specimen wasalso found in Mertendorf, Germany.

Type III Humeri—Humeri assigned to this type (Fig. 4) havea very massive appearance. Especially the proximal ends arevery massive and only slightly narrower than the shaft. The hu-meri are rather large, ranging from 114 mm to 129 mm in length.The preaxial edge is less straight, and the postaxial concavity lessdistinct than in type I. The margins of the articular facets are welldeveloped. The distal end is rather thick, and greatly broadened,resulting in a shovel-like distal end. An entepicondylar foramenis present in all specimens, as is an ectepicondylar groove. Thespecimens described below are sorted according to ontogeneticstage.

NMNHL St 445914 is a left humerus which was already figured

TABLE 1. Morphometrics of all studied humeri.

Specimen no. Left/rightLength(mm)

Proximalwidth (mm)

Minimalwidth (mm)

Distalwidth (mm) Morphotype

MHI 1875 l 78 15 15 23 INMNHL St 36375 l 95 20 15 — ISMNS 16253 r 104 17 16.5 29.5 INMNHL St 87289 r 107 22 16 29 IBGR X 13072 r 129 — 20 30 IMB.I.007.18 r 66 12 12 17 IIMB.I.007.18 l 63 11 12 15 IICHW 56 r 87 17 14 22 IIMB.R.162.3 r 90 21 17 25 IINME 480000126 r — 22 — 24 IINME 480000126 l — 22 — — IIMB.R.162.2 r 105 23 — 27 IINMNHL St 445914 l 114 28 21 31 IIIMB.R.162.1 r 116 24 — — IIIMB.R.159 l 128 33 26 — IIIMB.R.542 r — 27 — — IIIMB.R.539 r 129 30 22 — IIIMB.R.162.4 r 85 16 11 18 Juvenile

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by Hooijer (1959, fig. 3) in ventral view. This bone, coming fromthe Winterswijk locality, has a length of 114 mm and is verymassive (Fig. 4A–D). It is characteristically curved and exhibitsa nearly straight preaxial edge of the shaft (Fig. 4A, B). Theproximal head measures 28 mm in width. The deltopectoral crestextends to the margin of the articular head and is not set off (Fig.4A, B), nor is the insertion for the latissimus dorsi muscle (Fig.4C). On the dorsal side, there is also a pitted area indicatingmuscle attachments. The shaft displays the characteristically tri-angular cross-section and has a width of 22 mm. It has a distinctpostaxial edge as well as a small midshaft foramen (Fig. 4D). Thedistal end of the humerus is somewhat flattened dorsoventrallyand measures 31 mm in width. Preaxially, there is a small inden-tation on the distal end (Fig. 4A, B). There is a well-definedentepicondylar foramen (length: 9 mm, width: 3 mm), and theectepicondylar groove is also well developed. Rugosities can befound all over the bone, indicating a mature stage for the speci-men.

The right humerus MB.R.162.1 from the locality of Oberdorlais only partially preserved (Fig. 4E, F). It is 116 mm long with itsproximal end reaching a width of 24 mm. The deltopectoral crestand the latissimus dorsi insertion are well developed and not setoff. Between these, there is again a pitted muscle attachmentarea. The deltopectoral crest is fused with the margin of theproximal articular facet, which shows an incipient additionalfacet margin starting to develop. The shaft is triangular in cross-section, but the preaxial edge of the shaft is not very straight. Asparts of the shaft and the distal end are reconstructed in plaster,their width cannot be measured reliably. An entepicondylar fo-ramen is present, but incompletely preserved. In the middle ofthe distal part of the bone there is a small, raised area (Fig. 4E,F). Its function may be the insertion for muscles because thesurface shows the same pattern as other muscle attachment sites.There is a well-developed ectepicondylar groove. Rugosities allover the bone are of heavy intensity.

In terms of ontogenetic stages, the next largest humerus isMB.R.159 from the Oberdorla locality (Tables 1, 2), followed byMB.R.542 from the locality of Rüdersdorf (Table 1+2).

MB.R.539 from the Rüdersdorf locality is the largest humerusof type III, though incompleteley preserved (Fig. 4G–I), withparts of the preaxial distal end missing. Nevertheless, this righthumerus measures approximately 129 mm in length. The proxi-mal head is bulgy and 30 mm wide. The deltopectoral crest (Fig.4G, H) as well as the latissimus dorsi insertion (Fig. 4I) are verywell developed and set off distinctly. Due to the incomplete

preservation, no indentation is identifiable on the preaxial side.The shaft of the humerus is characteristically triangular in cross-section, 22 mm wide, and has a straight preaxial edge. Also,postaxially (Fig. 4I) the shaft has a well pronounced postaxialedge of the shaft. There is a well developed entepicondylar fo-ramen on the distal end of the humerus. It measures 8 mm inlength and 4 mm in width. Rugosities all over the bone are verywell developed.

A type III humerus from the Mertendorf locality is also de-picted in von Meyer’s (1847-1855) compendium on plate 32, fig.8. Von Meyer noted that this humerus resembled the humerus ofNothosaurus mirabilis from Bayreuth (Meyer, 1847-1855, plate44, fig.1), a nothosaur inhabiting the Muschelkalk Sea during theUpper Muschelkalk and Lower Keutimes.

The Juvenile Humerus

Specimen MB.R.162.4, which comes from the locality of Ob-erdorla, is a right humerus and has a very different appearance(Fig. 5A–E) from the ones described above. It measures 85 mmin length and is very slender and gracile. The proximal end is 16mm wide (Fig. 5E). The most notable feature is the deltopectoralgroove, a deep, elongate groove on the ventral side of the proxi-mal section of the humerus, which reaches to the middle of theshaft and thus extends for half the length of the bone (Fig. 5A,B). The groove indicates that the bone is incompletely ossified(Bellairs, 1970), and therefore suggests a juvenile stage for thespecimen. As such, the deltopectoral crest is not yet developedand the latissimus dorsi insertion is only weakly developed (Fig.5C). The surface of the articular facets is spongy and covered bysmall, rounded, and regularly spaced pits (Fig. 5E), already ob-served in NMNHL St 36375. The shaft is semicircular in cross-section, and at a width of 11 mm is very narrow. Its preaxialmargin is less straight than in all other described humeri. Post-axially, there is a small midshaft foramen (Fig. 5D) as describedfor the other specimens. The distal end (width: 18 mm) of thehumerus is not as flattened and not as concave as in other humeristudied. The entepicondylar foramen is very large (length: 4 mm,width: 3 mm). As noted earlier, ontogenetically, the entepicon-dylar foramen starts as a groove that becomes bridged over bybone, thus resulting in a foramen (Romer, 1956). In humerusMB.R.162.4, the groove seems to have been covered over onlyshortly before death, which is another indicator of the juvenilestatus of the specimen. There is a very slightly developed ectepi-condylar groove is a deep groove, which appears as if it just

TABLE 2. Characters of all studied humeri.

Specimen no.Left/right Morphotype Locality Appearance

dpc fusedwith facet

margin

ldi fusedwith facet

marginPittedarea

Cross-sectionof shaft

Indentationon preaxial

edgePostaxial

edge

MHI 1875 l I Gogolin slender Y — — — Y, proximally —NMNHL St 36375 l I Winterswijk slender Y Y N triangular N YSMNS 16253 r I Gogolin slender Y Y N triangular Y, proximally Y, sligthlyNMNHL St 87289 r I Winterswijk slender N N Y triangular N NBGR X 13072 r I Rüdersdorf slender N N Y triangular Y, proximally Y, sligthlyMB.I.007.18 r II Rüdersdorf slender — Y N — Y, distally NMB.I.007.18 l II Rüdersdorf slender Y — — — — NCHW 56 r II Winterswijk slender Y — — — Y, distally NMB.R 162.3 r II Oberdorla slender Y Y N triangular Y, proximally NNME 480000126 r II Winterswijk slender Y Y N — Y, proximally YNME 480000126 l II Winterswijk slender Y Y N — — —MB.R.162.2 r II Oberdorla slender — Y N triangular Y, distally NNMNHL St 445914 l III Winterswijk massive Y Y Y triangular Y, distally YMB.R.162.1 r III Oberdorla massive Y Y N triangular — Y, slightlyMB.R.159 l III Oberdorla massive N N N triangular N YMB.R.542 r III Rüdersdorf massive N Y Y — — —MB.R.539 r III Rüdersdorf massive N N N triangular — YMB.R.162.4 r Juvenile Oberdorla slender — Y N semicircular N N

BICKELMANN AND SANDER—NOTHOSAURUS FROM THE NETHERLANDS 333

started to close over, eventually resulting in an ectepicondylarforamen (Fig. 5 C, D). No rugosities could be identified on thebone surface.

Ontogenetic Changes

Several different ontogenetic changes could be observed in thehumeri, based on four features and correlating with size:

(1) Fusion of the Deltopectoral Crest and the LatissimusDorsi Insertion with the Margin of the Proximal ArticularFacet—At an early stage of development, the deltopectoral crestextends to the margin of the proximal head, and the facet marginis in contact with the proximal tip of the deltopectoral crest.Later in development, as the bone increases in size, the margin ofthe articular facet separates from the deltopectoral crest, result-ing in a notch between the articular head and the deltopectoralcrest, which becomes more distinct and widens with age. Simi-larly, a notch develops between the latissimus dorsi insertion andthe facet margin.

(2) Presence of an Indentation on the Most Proximal Tip ofthe Deltopectoral Crest—During the increase in size and thedevelopment of a notch, the articular facet margin of the hu-merus is still fused with the deltopectoral crest. It increasinglybecomes tongue-like in shape, and finally, a small part of thistongue-like structure separates from the rest and is found at themost proximal tip of the deltopectoral crest, resulting in whatlooks like a small indentation.

(3) Development of the Ectepicondylar Groove—In thesmallest specimens, the ectepicondylar groove is not well devel-oped. Later, a groove appears that successively deepens duringdevelopment, finally resulting in a deep kerf through which theradial nerve and blood vessels pass.

(4) Intensity of Rugosities—Rugosities on the bone surfaceare often associated with tendinous muscle attachments (Hi-eronymus, 2006). The intensity of deep grooves all over the boneincreases during development as the muscles, which insert intothe bone, become stronger. At an early developmental stage, thesurface of areas of muscle attachments is smooth, whereas olderspecimens show a lot of rugosities. On the other hand, the re-maining bone surface becomes smoother with age because fewerblood vessels enter the bone tissue as bone apposition slowsdown.

The development of these four features, accompanied by anincrease in length, can be nicely observed in all Lower and low-ermost Middle Muschelkalk nothosaur humeri considered in thisstudy. As seen in MB.R.162.4, the juvenile humerus differs

greatly from the older specimens. All other humeri presumablyrecord the ontogenetic changes from a subadult to a very maturestage.

DISCUSSION

In Lower and lowermost Middle Muschelkalk times, the Ger-manic Basin was inhabited by various sauropterygian species,such as the pachypleurosaurids Anarosaurus and Dactylosaurus,the cymatosaurid Cymatosaurus, from which so far only skullsare known, the nothosaurs Germanosaurus and Nothosaurus,and the placodonts Placodus and Paraplacodus, with the humeriof each group possessing a distinct morphology (Hagdorn andRieppel, 1998).

Only two named Nothosaurus species inhabited the Germanicbasin at the time of deposition of the Lower and lowermostMiddle Muschelkalk: N. winterswijkensis (Albers and Rieppel,2003) and N. marchicus (Koken, 1893). N. winterswijkensis, andmaterial ascribed to N. marchicus (Koken, 1893) but showingfeatures which put it in a position intermediate between N. win-terswijkensis and N. marchicus, are found in Winterswijk (Albersand Rieppel, 2003; Albers, 2005). The lower jaw (NMNHL St445913) of Hooijer (1959) and other bones of a large nothosaurrepresent a new but yet unnamed Nothosaurus species. From theLower Muschelkalk of Rüdersdorf, N. raabi (Schröder, 1914),which was later assigned to N. marchicus, is reported. The notho-saurian bones found in Oberdorla and Gogolin have not beenassigned to a named species.

Humeri of all three types are found at Winterswijk andRüdersdorf. Oberdorla produced only humeri of type II and typeIII. In Gogolin, only humeri of type I are found. Because of thesmall number of specimens, this may be an artifact of sampling,and all three types may be present at all localities.

Currently, the taxonomic affinities and the biological back-ground of the three morphotypes are not understood. One wayto solve this problem would be to assign the types to the validNothosaurus species. Since there are not enough skeletons withboth cranium and postcranium preserved at Winterswijk and theother Lower and lowermost Middle Muschelkalk localities, thiswas problematic. Only humerus type could be assigned to anamed taxon humerus belongs to a skull of N. winterswijkensis(Albers and Rieppel, 2003), as noted above. In addition, thehumerus of the holotype of N. raabi (i.e. N. marchicus) fromRüdersdorf. This leaves several possible hypotheses for the af-finities of the Nothosaurus humeri from the Lower and lower-most Middle Muschelkalk:

TABLE 2. (Extended)

Small midshaftforamen postaxially

Entepicondylarforamen

Length ofentepicondylarforamen (mm)

Width ofentepicondylarforamen (mm) Ectepicondyle

Ectepicondylargroove

Spongy surfaceon facet heads

Rugositieson surface

— Y — — — Y, sligthly N nearly noN Y — — Y Y, sligthly Y mediumY N — — Y Y N mediumN N — — Y Y N heavyY N — — Y, well Y, well N heavy— Y 4.5 1 — — N nearly no— Y 4 1 Y Y, slightly N nearly noY Y 10 3 — Y Y medium

Y, more dorsally Y 6 2 Y Y N medium— Y — — — — N medium— — — — — — N medium— Y — — Y, well Y Y mediumY Y 9 3 Y, well Y, well N heavy— Y — — Y, well Y N heavyN Y — — Y Y, well Y/N heavy— — — — — — Y heavyN Y 8 4 — — N heavyY Y 4 3 N Y, sligthly Y N

JOURNAL OF VERTEBRATE PALEONTOLOGY, VOL. 28, NO. 2, 2008334

FIGURE 3. Nothosaurus sp. Humerus morphotype II. Photograph (A) and drawings of specimen CHW 56 from Winterswijk, The Netherlands, inventral (B) and postaxial (C) view. The dorsoventral thinness is due to crushing. Photograph (D) and drawings of specimen MB.R.162.3 fromOberdorla in ventral (E), dorsal (F), and postaxial (G) view. Photographs and drawings of specimen NME 480000126 from Winterswijk, theNetherlands, in ventral view. Right (H–K) and left (L, M) humerus. Diagonal hatching indicates broken bone. Proximal is at the top. All images areto the same scale and each scale bar equals 10 mm.

BICKELMANN AND SANDER—NOTHOSAURUS FROM THE NETHERLANDS 335

FIGURE 4. Nothosaurus sp. Humerus morphotype III. Photograph (A) and drawings of specimen NMNHL St 445914 from Winterswijk, TheNetherlands, in ventral (B), dorsal (C) and postaxial (D) view. Photograph (E) and drawing (F) of specimen MB.R.162.1 from Oberdorla in ventralview. Photograph (G) and drawings of specimen MB.R.539 from Rüdersdorf in ventral (H) and postaxial (I) view. Proximal is at the top. All imagesare to the same scale and each scale bar equals 10 mm.

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(1) Each of the three types represents a different Nothosaurusspecies. In Winterswijk, skulls of N. winterswijkensis and anintermediate form, which was assigned to N. marchicus (Al-bers and Rieppel, 2003; Albers, 2005) were found. The hu-meri of both N. winterswijkensis (NME 480000126) and N.marchicus (holotype of N. raabi, MB.I.007.18) belong to typeII, suggesting that these are a single evolutionary lineage,namely the N. winterswijkensis-N. marchicus-clade, in whichthe species cannot be differentiated on the basis of the hu-meri. The other two types belong to a yet unknown medium-sized species of Nothosaurus in Winterswijk. The large spe-cies of Nothosaurus found at Winterswijk (Hooijer, 1959)can be excluded from consideration because of the relativelysmall size of even the most mature humeri.

(2) There are two different medium-sized Nothosaurus specieswith at least one showing sexual dimorphism. Sexual dimor-phism involving the forelimb has been demonstrated for allpachypleurosaurs that are known from sufficient material(Sander, 1989; Lin and Rieppel, 1998). Also, Renesto et al.(2004) have already suggested the existence of sexual dimor-phism in Lariosaurus. Pachypleurosaurs being the sister-taxon to Nothosauridae, a taxon including Nothosaurus andLariosaurus, would lend support to the hypothesis of humer-al sexual dimorphism in Nothosaurus. As type II humeri canbe assigned to the N. winterswijkensis-N. marchicus-clade,either type I or type III would belong to the other sex. TypeII humeri are found at Winterswijk, Rüdersdorf, and Ober-dorla, but not at Gogolin. Gogolin has produced only type Ihumeri. Since Oberdorla produced type II and type III hu-meri, it could then be assumed that these two are the sexualmorphs of the same species. Type I, found at Winterswijk,Rüdersdorf, and Gogolin would represent an as yet un-known Nothosaurus species.

(3) Because the eosauropterygian taxa Germanosaurus and Cy-matosaurus are only known from skulls, it is also possiblethat type I belongs to Germanosaurus and type III belongs toCymatosaurus, or vice versa, and only type II humeri belong

to Nothosaurus, i.e. the N. winterswijkensis-N. marchicus-clade. This hypothesis remains a possibility because Cyma-tosaurus and Germanosaurus are closely related to Notho-saurus. In this regard, it should be noted that the humerusfrom Winterswijk identified by Rieppel (1994) as Cymato-saurus is that of a large pachypleurosaur, which is docu-mented by a nearly complete skeleton of a large pachypleu-rosaur (Dactylosaurus) from the same locality that bears thesame humerus type (Oosterrink et al., 2003; Fig. 47).

In conclusion, although the humeri of Nothosaurus from theLower and lowermost Middle Muschelkalk show a complex mor-phology, they are still insufficient for a diagnosis at species level.While the complex morphology reveals enough features to dis-tinguish the morphotypes, it is not known which morphotypebelongs to which species, and only future finds of more completeskeletons of Nothosaurus will clarify matters.

ACKNOWLEDGMENTS

We would like to thank the following institutions and indi-viduals for access to the specimens examined for this study: M.Blokhuis, Natuurmuseum Enschede, Enschede, The Nether-lands; J. Fenner, Bundesanstalt für Geowissenschaften und Roh-stoffe, Dienstbereich Berlin, Berlin, Germany; H. Hagdorn,Muschelkalkmuseum Hagdorn Ingelfingen, Ingelfingen, Ger-many; W.-D. Heinrich, Museum für Naturkunde, Humboldt-Universität zu Berlin, Berlin, Germany; J. de Vos, National Mu-seum of Natural History Naturalis, Leiden, The Netherlands; H.Winkelhorst, private collection Herman Winkelhorst, Aalten,The Netherlands. We specially would like to thank P. Albers,Emmen, for his help with the Winterswijk fossils, including ar-ranging for their transfer from private collections to Naturalis,Leiden. Furthermore, we are grateful to H. Hagdorn, Mus-chelkalkmuseum Hagdorn Ingelfingen, for the clarifying discus-sions on Muschelkalk stratigraphy. We are very grateful to the‘Werkgroep Muschelkalk Winterswijk’, especially H. Winkel-horst and J. Lankamp, for arranging access to some private col-

FIGURE 5. Nothosaurus sp. Juvenile humerus MB.R.162.4 from Oberdorla . Photograph (A) and drawings of the specimen in ventral (B), dorsal(C), postaxial (D) and proximal (E) view. Proximal is at the top. Scale bar equals 10 mm.

BICKELMANN AND SANDER—NOTHOSAURUS FROM THE NETHERLANDS 337

lections of Winterswijk fossils. Special thanks go to O. Dülfer forassisting during the preparation work, D. Kranz for improvingthe drawing technique of the first author, and G. Oleschinski forthe excellent photography. All are on the staff of the Institute ofPaleontology, University of Bonn. W. Klein introduced the firstauthor to the Dutch collections and collectors. The comments ofC. Kolb, J. Müller, and L.Tsuji improved an earlier version of themanuscript, and the reviews by S. Renesto and F. R. O’Keefe aregreatfully acknowledged.

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Submitted August 27, 2007; accepted October 30, 2007

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