from the Upper Cretaceous redbeds at Bayan

A new species of Zangerlia (Testudines: Nanhsiungchelyidae) from the Upper Cretaceous redbeds at Bayan Mandahu, Inner Mongolia, and the relationships of the genus

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Donald Brinkman and Jiang-Hua Peng

Abstract: Zangerlia neimongolensis sp.nov. is described on the basis of material from the Upper Cretaceous redbeds at Bayan Mandahu in Inner Mongolia. Zangerlia neimongolensis is similar to Zangerlia testudinimotpha in the proportions of the carapace and plastron and presence of a knob at the posterior end of the neural series, but differs from it in the arrangement of scutes covering the bridge. The placement of Zangerlia in the Nanhsiungchelyidae is supported by derived features of the bridge peripherals and plastral scutes shared by 2. neimongolensis, Basilemys, and Nanhsiungchelys. These are the presence of ventrally expanded sixth inframarginal scutes, humeral scutes that are narrow at the midline and expanded laterally, pectoral scutes that are wide at the midline and narrow laterally, and large rectangular abdominal scutes. The skull of Zangerlia is more primitive than that of Nanhsiungchelys, the only other member of the family for which a skull is known. It shows extensive emargination of the temporal and cheek regions and the absence of a large, tubular external narial opening. A cladistic analysis of the Trionychoidea using Zangerlia as the representative of the Nanhsiungchelyidae suggests a sister-group relationship between the Nanhsiungchelyidae and Adocidae. RCsumC : Nous dkcrivons Zangerlia neimongolensis n.sp. a partir de vestiges rCcupCrCs dans les couches rouges d'lge CrCtacC tardif, a Bayan Mandahu, Mongolie intCrieure. Les proportions de la carapace et du plastron et la prCsence d'une protubkrance I'extrCmitC postCrieure de la sCrie neurale de 2. neimongolensis sont similaires i ce qu'on observe chez Zangerlia testudinimotpha, mais il y a des diffkrences quant i la disposition des plaques qui recouvrent le dos. Le classement de Zangerlia parmi les NanhsiungchClyidCs est fond6 sur les caractkres dCrivCs des plaques pCriphCriques du dos et les Ccailles du plastron ventral communes i Z. neimongolensis, Basilemys et Nanhsiungchelys. Leur plastron ventral est formCe de six Ccailles inframarginales, d'Ccailles humCrales Ctroites au centre du plastron et s'klargissant lateralement, d'tcailles pectorales larges au centre du plastron se rCtrtcissant latkralement et de larges Ccailles abdominales rectangulaires. Le crsne de Zangerlia est plus primitif que celui de Nanhsiungchelys, seul autre membre de la famille dont le crlne a CtC CtudiC. Le crlne exhibe une Cmargination Ctendue des rCgions temporale et jugale, avec l'absence de grande ouverture tubulaire externe des narines. Une analyse cladistique des TrionychoidCs, utilisant Zangerlia cornrne reprCsentant des NanhsiungchClyidCs, suggCre une relation de groupe-soeur entre les NanhsiungchClyidCs et les AdocidCs. [Traduit par la rCdaction]

I

Received February 18, 1995. Accepted June 28, 1995.

D. Brinkman.' Royal Tyrrell Museum of Palaeontology, P.O. Box 7500, Drurnheller, AB TOJ OYO, Canada. J.-H. Peng. Institute of Vertebrate Paleontology and Paleoanthropology, Academia Sinica, P.O. Box 643, Beijing 100044, People's Republic of China.

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Corresponding author (e-mail: [email protected] .ab. ca) .

Can. J. Earth Sci. 33: 526-540 (1996). Printed in Canada / Imprim6 au Canada


Brinkrnan and Peng

527

Pet$epa~ Zangerlia neimongolend sp.nov. onacrmaeTcR Ha ocHose MaTepaana ~ BO B H Y T P ~ H HM~ o~ H~o~MH. a3 KpaCHOqBeTHbIX nnaCTOB B E a f i ~MaHAaXY Zangerlia neimongolensis cxoma c z . testudinimorpha B oTHomeHaa nponopqan KapanaKca a nnacTpoHa a npacyTcTsaR 6 y r o p ~ aB s a n ~ e ~ Koaqe AopcanbHoro pHgar HO OTnaYawrcR pacnonoxeaseM CKYTOB, noKpHsamuax MocTnK. noMeueaae Zangerlia B ~anhsiungchelyidae nOATBepXAaeTCR yHaCnenOBaHHbIMI-3XapaKTepHCTHKaMH nepa@epasec~ax neperoponoK ( c e n ~ )a nnacTpanbHbIx CKYTOB, 064ax An2 ~ Z.neimonqolensis, Basilemys, B Nanhsiungchelys. T ~ K o B M MRBnmoTcs npHCyTCTBHe BeHTpaJIbHO BHCTynaKluHX UeCTbIX H H & X L M ~ ~ ~ H H ~ ~ ~ H ~ I X CKYTOB, nneYeBMX uHTKOB, KOTOpbIe RBnHKlTCR y3KHMI-I B cpen~efinHHaH a pacuapeHHmMa naTepanbso, neKTopanbHMx CKYTOB, KoTopHe mapoKae B c p e n ~ e nnaHaa a y s ~ a enaTepanbao, a 6onbwax npxMoyronbHMx Yepen Zangerlia 6onee n p n ~ a ~ a ~no~ a n a 6 n o ~ a ~ a n b ~ bCKYTOB. 1x CpaBHeHPiH3 C Nanhsiunqchel~,eAHHCTBeHHMM ApyraM YneHOM C ~ M ~ ~ C T B ~ , AnR KOTOpOI'O H3BeCTeH Yepen. OH HeMOHCTPWpYeT CYILleCTBeHHYD BbIeMYaTOCTb BHCOYHHX E-3 WeYHbIX o6nac~efia OTCyTCTBMe 60nbuoro Tpy65~aTor0BHemHerO HO3ApeBOOrO OTBepCTE'iR. AHanE33 KnaAOreHe3a Trionychoidea, nonbsy~cbZangerlia KaK npeAcTaBaTeneM Nanhsiungchelyidae, npeAnonomaTenbHo n o ~ a 3 a ~ acecTpaHcKoe~ rpynnoBoe ~ s a w ~ o o ~ ~ o mMexqy e ~ a Nanhsiungchelyidae e a Adocidae. [nepeaon BbrnonHeH nnH penaKgm H a y q ~ o - M c c n e n o ~ a r e n b cX~y~pe~ a n b r ]

Introduction The Upper Cretaceous redbeds at Bayan Mandahu in Inner Mongolia have yielded a diverse assemblage of fossil vertebrates that is, in general, similar to that from the Djadokhta Formation in Mongolia (Jerzykiewicz et al. 1993; Dong 1993; Dong and Currie 1993). However, turtle remains are much more abundant in the Bayan Mandahu locality. In contrast to the two fragmentary turtle specimens collected in the Djadokhta Formation of Mongolia (Gilmore 193I), seven substantially complete shells have been collected at Bayan Mandahu. Many are associated with postcranial elements, and two include cranial remains. This material is herein described as Zungerlia neimongolensis sp.nov. The genus Zungerlia was erected by Mlynarski (1972) for a large, terrestrial turtle from the "Lower Nemeget Beds" of Mongolia (now the Barun Goyat Formation, Jerzykiewicz and Russell 1991). Mlynarski placed Zungerlia in the Dermatemydidae, because of the presence of inframarginal scutes and dermal sculpture similar to that of some other members

of the family. This was followed by Mlynarski (1976), who included these features in the diagnosis of the Dermatemydidae. However, the presence of inframarginal scutes is a primitive character state within the Eucryptodira and dermal sculpture varies among taxa included within the Dermatemydidae, so the placement of Zungerlia in the family is only weakly supported at present. Meylan and Gaffney (1989) used derived features to resolve the relationships of many of the turtles placed in the Dermatemydidae by Mlynarski (1976). The family was restricted to the genera Dermatemys and Baptemys and was placed with the ~inosternidaein the ~inosternoidae.Zungerlia was united with Basilemys and Nanhsiungchelys in the Nanhsiungchelyidae, and this family was placed with Adocus and the ~ r i o n ~ c hwithin ia the ~ r i o n ~ c h o i d eA a . sister-group relationship between the Nanhsiungchelyidae and Peltochelys plus Trionychia was supported primarily by features from the skull of Nanhsiungchelys. A close relationship between Basilemys and Nanhsiung-

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Fig. 1. Zangerlia neirnongolensis, carapace and plastron. (A, B) Type specimen, IVPP 020788-7, in (A) dorsal and (B) posterior views. (C) Specimen IVPP 290690-6, in ventral view.

the Trionychoidea. It is concluded that Zungerlia is more closely related to Basilemys than is Nanhsiungchelys. A sister-group relationship between Adocus and the Nanhsiungchelyidae is suggested by the new information. Institutional abbreviations IVPP, Institute of Vertebrate Paleontology and Paleoanthropology, Beijing; NMB, Nei Mongo Bowuguan (= Inner Mongolia Museum), Hohhot, Inner Mongolia; TMP, Royal Tyrrell Museum of Palaeontology, Drurnheller .


Taxonomy Order Cryptodira Cope, 1868 Suborder Eucryptodira Gaffney , 1975 Superfamily Trionychoidea Fritzinger 1876 Family Nanhsiungchelyidae Yeh, 1966 Genus Zungerlia Mlynarski, 1972 Diagnosis Shell relatively short and and wide compared with other members of the family; posterior peripherals subvertical in position, not flared outwards; first suprapygal much smaller than second; a knob present at about the position of the first suprapygal and the posterior edge of the shell steeply deflected below this; anterior lobe of plastron subrectangular in shape; posterior lobe short compared with other members of the family, distance between the posterior end of the plastron and posterior end of the carapace greater than the length of the posterior lobe of plastron.

Zangerlia neimongolensis sp.nov . (Figs. 1-9) Type specimen IVPP 020788-7, back half of shell, carapace preserved from the seventh neural, and plastron preserved posterior to hyoplastron-hypoplastron suture, skull, neck, girdles and limbs preserved within this portion of carapace, hind limbs and pelvis in articulation except for feet, remainder of skeleton disarticulated.

chelys was also suggested by Sukhanov and Narmandakh (1977), who synonymized the two genera and described the shell and limbs of a species from Mongolia, "Basilemys" orientalis. Brinkman and Nicholls (1993) argued that this synonymy is not justified, and that the two Asian taxa are both members of the genus Nanhsiungchelys. Nanhsiungchelys orientalis is primitive relative to Basilemys in the retention of four inframarginal scutes. Only the axillary and inguinal scutes are present in Basilemys. Zungerlia was considered the most primitive member of the Nanhsiungchelyidae by Brinkman and Nicholls (1993), because of the presence of irregularly shaped inframarginals and the lack of a ventrally expanded sixth marginal scute in Zungerlia testudinimorpha. Information from Z. neimongolensis sp.nov. leads to a reappraisal of both the interrelationships of the genus within the Nanhsiungchelyidae and the position of that family within

Locality and horizon Inner Mongolia, Nuchidaba locality, about 9 km northeast of Bayan Mandahu, which lies about 45 km north of Urad Houqi (Dong 1993; Eberth 1993). All the turtle specimens collected from this locality come from a limited area within the Nuchidaba locality referred to as "the gate" (Eberth 1993), and are within Eberth's zone 2. Eberth interpreted this zone as an organically productive, sandy area between the margins of an alluvial fan (zone 1) and a dune field (zone 3). Etymology The name is derived from Nei Mongol Zizhiqu, the province in which the Bayan Mandahu locality occurs. Diagnosis A species of the genus Zungerlia in which a midline keel is absent; the entoplastron is of large size and extends posterior

Brinkman and Peng

Fig. 2. Zangerlia neimongolensis, carapace and plastron. (A, B) Type specimen, IVPP 020788-7, in (A) dorsal and (B) posterior views. (C) Specimen IVPP 290690-6, in ventral view. (D) Specimen IVPP 020790-5, in ventral view. AX, axillary scute; C8, eighth costal; GU, gular scute; IGU, intergular scute; ING, inguinal scute;


M4-M6, marginal four to marginal six; N8, eighth neural; P6-Pll, peripheral six to peripheral eleven; PY, pygal; SP2, second suprapygal.

to the level of the axillary notches; and the midline plastral sulcus is highly sinusoidal on the posterior lobe.

Referred specimens IVPP 020790-5, complete plastron, first dorsal vertebra, right first dorsal rib, rib head of first costal, and isolated phalanges and carpals; IVPP 290690-6, back end of plastron and carapace prepared in ventral view, both feet and tail preserved in articulation, scattered dermal ossicles around both feet; IVPP 020790-4, posterior three quarters of carapace prepared in dorsal view; IVPP 130790-1, posteriorlateral edge of carapace prepared in dorsal view; NMB 2802, shell, nearly complete except for anterodorsal surface, which has eroded away, skull with lower jaws sitting on visceral surface of anterior lobe of plastron, skull roof missing; NMB 4252, posterior half of carapace, hind limbs preserved in articulation but feet disarticulated and scattered.

Description and comparisons The carapace of Z. neimongolensis (Figs. 1, 2, 3B) matches that of Z. testudinimorpha (Fig. 3A) in proportions, being shorter and more nearly circular in outline than that of Nanhsiungchelys or Basilemys (Figs. 3C, 3D). As in Z. testudinimorpha, a knob is present at about the end of the neural series, and the posterior edge of the shell is steeply deflected below this (Figs. lA, 1B). A midline keel is absent in Z. neimongolensis. A shallow depression runs along the mid-dorsal surface of the carapace in some specimens (e.g., NMB 2802), but this is interpreted as an artifact of preservation, and the presence of a smoothly rounded carapace is thought to be the normal condition for the species. None of the available shells preserve the nuchal bone or the anterior edge of the neural series. Of the neural series, only the last two neurals can be distinguished (Fig. 2A). Both

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Fig. 3. A comparison of the plastron of (A) Zangerlia testudinimorpha, (after Mlynarski 1972), (B) Zangerlia neimongolensis (from specimen IVPP 020790-5), (C) Nanhsiungchelys orientalis, (after Sukhanov and Narmandakh 1977), and (D) Basilemys variolosa (from


Langston 1956).

are relatively short, rectangular elements. These completely separate the costal bones. The first suprapygal is intermediate in size between the second suprapygal and last neural (Figs. 2A, 2B). The second is a large, wide triangular element extending laterally to contact the tenth peripheral. The pygal is a short, rectangular element. This arrangement of the posterior neurals and suprapygalpygal series is similar to that of 2. testudinimorpha. The first two costals are not preserved. The third to sixth costals are relatively narrow elements with little expansion of either medial or lateral ends. The seventh and eighth costals are both subrectangular but with their lateral ends slightly wider than their medial ends (Figs. 2A, 2B). Only the seventh and more posterior peripherals are preserved in dorsal view (Figs. lA, 2A, 2B). The seventh to tenth peripherals are tall and narrow, their height being about one and a half times their width. The height of the eleventh peripheral is about equal to its width. These proportions are

similar to those of Basilemys and Nanhsiungchelys, although the posterior peripherals do not flair outwards as they do in those taxa. The vertebral scutes are narrow, as in all other members of the family. The proportions of the pleural scutes do not differ significantly from those of 2. testudinimorpha. The pleurornarginal sulcus follows the costal-peripheral suture from peripherals seven to ten, then crosses the lower third of the second suprapygal. The plastron is best represented by IVPP 020790-5 (Fig. 2D). The surface of the bone is well preserved, and most sutures and sulci can be clearly identified. Areas of uncertainty, principally on the posterior half of the plastron, are documented by specimens IVPP 290690-6 (Fig. 1C) and IVPP 020788-7 (Fig. 2C). The anterior lobe of the plastron is subrectangular, in contrast to Nanhsiungchelys and Basilemys, where the anterior lobe is more triangular in shape (Figs. 3C, 3D). The pos-

Brinkman and Peng


Fig. 4 . Zangerlia neimongolensis, skull, type specimen, IVPP 020788-7, in (A) dorsal, (B) palatal, and (C) lateral views.

terior lobe is generally shorter than wide, has a rounded outline and is separated from the posterior edge of the carapace by a distance about equal to the length of the posterior lobe (Fig. 2C), matching the posterior lobe in Z. testudinirnorpha (Fig. 3A) in proportions. However, some variation is present. In IVPP 290690-6, the posterior lobe is relatively longer and is more nearly rectangular in shape (Fig. 1C). The bridge is much longer than either of the plastral lobes. The epiplastra form much of the anterior lobe of the plastron and have a long sutural contact with one another at the midline (Fig. 2D). The entoplastron is a large element, wider than long, that extends posterior to the level of the axillary notches (Fig. 2D). Both Nanhsiungchelys and Basilemys also have a large entoplastron wider than long, although it does not extend as far posteriorly in these genera. An entoplastron was not preserved in Z. testudinimopha, but Mlynarski (1972) noted on the basis of the preserved portion of the hyoplastron that it was at most a small element. The hyoplastron-hypoplastron suture is located midway between the axillary and inguinal notches. The hyoplastron contacts peripheral three anteriorly and extends to the anterior corner of peripheral six posteriorly. The hypoplastron extends to the anterior tip of peripheral eight. The hypoplastronxiphiplastron suture extends transversely across the base of the posterior lobe of the plastron, rather than being V-shaped, as in primitive eucryptodires such as Ordosernys (Brinkman and Peng 1 9 9 3 ~ ) . The plastral scutes are most completely preserved in IVPP

Fig. 5 . Zangerlia neimongolensis, skull, type specimen, IVPP 020788-7, in (A) dorsal, (B) palatal, (C) lateral, (D) anterior, and (E) occipital views. F BS, foramen basisphenoidale; F PO, fenestra postoticum; F POST CAN CAR, foramen posterior canalis carotici interni; F ST, foramen stapedio-temporalis; PR TR OT, processus trochlearis oticum.

020790-5 (Fig, 2D). The in~ergularscures are large paired scutes that extend onto the anterior tip of the entoplastron. The pular scutes meet one another at the midline, formins a narrow band that separates the intergular and hurneral scutes. This is a derived feature. differing from that o r Nanlrsiungchelys (Fig. 3Cj and two species of Bf~silernys(B. variolosa and R. rlohilis) where the gulars are trian_gular elements restricted to the anterolateral edges of the epiplastra. However. Rosil~n~vs sinuo,~a( F i g . 3D) and Bnsilernys prueclnra are similar to Zclngrrlia in having gular scutes that contact onc another at the midline. The gencral arrangement of the more posterior scutes (Figs. IC, X , 2D) conforms closely with that of other memhers of the Nanhsiungchefyidae. The hurneral scutes are narrow at the midline and cxpand laterally. They contact the axillary scute. preventing exposure of the pectoral scutes on rhe axillary notch. The pectoral scutes are wide at the midline and narrow laterally. They cnntact the inguinal and Lfth rnarpinal scutes laterally. The abdominal scutes span the hyoplastron-hypplastron suture and cover a rectangular

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Fig. 6 . Zangerlia neimongolensis, lower jaws, type specimen, IVPP 020788-7, in (A) lateral and (B) dorsal views. DENT POCK, dentary pocket; FO MECK, fossa meckelii; PR COR, processus coronoideus.

area on the ventral surface of the plastron. The femoral scutes span the hypoplastron-xiphiplastron suture. cover the base of the posterior Iobe of the plastron, and contact the inguinal scute laterally. The anal scutes are V-shaped, pointing forwards, but do not reach the hypoplastronxiphiplastron suture. The midline sulcus is straight from the anterior tip of the plastron to about the base of the posterior lobe of the plastron. The sulcus cannot be traced completely on the posterior Iobe, but at least two wide loops are present. Thus the sulcus in this region is, in general, similar to that of N, orientalis, B, praeclara, and B. nohilis in being highly sinuous, Jthough the number of loops and their full lateral extent is uncertain. In 2. restudinirnorphathe sulcus is nearly straight, and in B. varioIosa the sulcus is only weakly sinuous. Sulci on the bridge area are incompletely preserved, so some uncertainty concerning the arrangement of scutes in this area exists. Following the pattern in Basilernys, as revised by B r i n b a n and Nicholls (19931, a large scute covering the axillary notch is identified as the axillary scute, and a large scute covering the inguinal notch is identified as the inguinal smite. In Basilemvs, a narrow scute passes between the inguinal and femora1 scutes to the posterior edge of the carapace. IVPP 290690-6 (Fig. 1C) demonstrates clearly that no such scute was present in 2. neimangolensis.

Rather, the inguinal scute contacts the femoral scute. A second inframarginal scute is absent, in contrast to the condition in Nanhsiungchelys (Fig. 3C). However, a third inframarginal may be present as an individual variant. On the right side of specimen IVPP 020790-5 (Fig. 2D), the presence of this scute is indicated by traces of a suIcus between the sixth marginal and the abdominal scutes. The shape and position of this scute are similar to the third inframarginal of Nanhsiungchelys (Fig. 3C). However, no other specimen shows traces of such a scute, so the presence of a third inframarginal scute may be variable within Z. neimongolensis. The marginal series is dominated by the sixth marginal, which is ventrally expanded as in Basilcmys and Nanhsiungchdys. The fourth and fifth marginal scutes are visibIe on the left side of IVPP 020790-5 (Fig. 2D). The fourth is retracted and does not make contact with the pectoral scute. Zangerlia testudinimopha differs from 2. neimongolensis in that the infrarnargind scutes are irregularly developed and the right side does not match the left. Likely, as noted by MIynarski (1972), the scutes on the bridge area are abnormally developed in 2. testudinimolpha, and do not represent a primitive pattern for the genus, as assumed by Brinkrnan and Nicholls (I 993). The skull is best preserved in specimen N P P 020788-7 (Figs. 4, 5). As in Adocus, Baptem~s,and Dennatemys, and in contrast to Nanhsiungche(vs, deep temporal and cheek ernarginations are present. The temporal emargination reaches forwards to the posterior edge of the orbit. and thus is relatively longer than in Adocus, which ends relatively more posteriorly. The cheek emargination reaches above the ventral edge of the orbit, although the bar separating the cheek emargination from the temporal ernargination remains relatively deep compared with that of Adocus. The depth of this bar in Zangerlia is about half the vertical distance from the quadrate articular surface to the edge of the temporal ernargination. In Adocus the bar is about a third of this distance. The antorbitat region of Zangeriia does not project forward as a tubular snout as it does in Nanhsiringchelys. Rather, the external n a r d opening is a relatively small opening nearly round in end view and vertical in lateral view, as in Adocus. The opening is bordered ventrally by the paired premaxilla, laterally by the maxitlae, and dorsally by the prefrontal. The contact between the prefrontal and maxilla meets the narial opening midway along its side. Notches are present on either side of the opening at the prefrontal-maxilla suture. Both Zangerlia and Adocus have a wide interorbital region, with little embayment of the skull roof between the orbits. A groove on the external surface of the maxilla borders the anteroventral edge of the orbit in Zangerlia. No such groove is present in Adccus. The jugal forms much of the posterior border of the orbit. The prefrontal forms the anterodorsal edge and extends well posterior to the centre of the orbit, suggesting that the ftontal was excluded from the margn of the orbit. However, the anterior edge of the postorbital cannot be identified, so the relationships of the frontal, prefrontal, and postorbital are uncertain. The otic capsule is anteroposteriorly elongate and bears a sharply defined processus trochlearis oticum. The lateral edge of the trochlearis is separated from the quadratojugal by a distinct notch; the medial edge does not project forwards as sharply. This differs from the condition in Adocus where both the medial and lateral edges of the processus trochlearis

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Brinkrnan and Peng

Fig. 7. Zangerlia neimongolensis, cervical vertebrae, type specimen, IVPP 020788-7. (A-G) Cervical vertebrae two to eight in lateral and dorsal views. (H) Cervical vertebra two in posterior view. (I) Cervical vertebra five in anterior view. (J) Cervical


vertebra six in posterior view.

Fig. 8. Zangerlia neimongolensis, scapula and coracoid, type specimen IVPP 020788-7. (A, B) Right scapula in (A) posterior and (B) anterior views. (C, D) Right coracoid in (C) ventral and (D) dorsal views.

oticum are well defined and the process projects forward into the adductor fossa. It is uncertain whether the descending process of the parietal forms a portion of the trochlear surface. Only the medial edge of the foramen stapedio-tempsralis is preserved. The diameter of this opening is slightly less than the diameter of the foramen posterius canalis carotici interni. The supraoccipital spine is long, deep, slightly thickened ventrally, and has a rounded ventral edge. The squamosal spines are much shorter in length than the supraoccipital spine, comparable to those of Adocus. The occipital condyle is a low, wide structure formed by the basioccipital and exoccipitals. Unlike the condition in most turtles, the basioccipital reaches the dorsal surface of the condyle and forms the ventralmost border of the foramen magnum. The exoccipitals form the lateral borders of the foramen

magnum and the dorsolateral portion of the occipital condyle. Two foramina nervi hypoglossi are present in the exoccipital just lateral to the occipital condyle. These foramina are floored by the basioccipital tubercula. The basioccipital tubercula are wide structures weakly subdivided into a medial portion formed by the basioccipital and a lateral portion formed by the exoccipital. The basioccipital tubercles are separated from one another by a deep median trough in the ventral surface of the basioccipital. The fenestra postotica is a nearly circular opening bordered dorsally by the opisthotic, laterally by the quadrate, medially by the exoccipital, and ventrally by the pterygoid. Meylan and Gaffney (1989, their Fig. 4) identify in Adocus a foramen bordered by the exoccipital and basioccipital and located medial to the foramen nervi hypoglossi as a foramen jugulare posterius. However, the foramen jugulare posterius



Fig. 9. Zangerlia neimongolensis, forelimb elements, type specimen, IVPP 020788-7. (A-C) Right humerus in (A) dorsal, (B) ventral, and (C) posterior views. (D, E) Right radius and ulna in (D) anterior and (E) posterior views.

is typically lateral to both the foramen nervi hypoglossi and the exoccipital, so the foramen jugulare posterius of Meylan and Gaffney (1989) is likely one of the foramina nervi hypoglossi. Thus reinterpreted, Zangerlia and Adocus would be similar in the absence of a distinct foramen jugulare posterius and in the position of the foramen nervi hypoglossi. The quadrate of Zangerlia has a completely enclosed incisura columella auris, as does that of all trionychids. A shallow, wide groove extends across the posterior end of the quadrate above the jaw joint. The tympanic cavity is antero-

posteriorly elongate, rather than nearly circular as in Adocus, and the distance between the anterior edge of this cavity and the posterior edge of the orbit in Zangerlia is relatively less. The triturating surface of Zangerlia is simpler than that of Adocus, Baptemys, and Dermutemys, in the absence of a maxillary tooth. A deep pit is present on the most anterior part of the triturating surface, which is formed by the premaxilla, suggesting the presence of a symphyseal hook on the dentary. As in Adocus, this pit is not bordered posteriorly by a commissual ridge, which in Baptemys and Dermutemys is a sharp transversely oriented ridge located just posterior to the symphyseal pit. A small opening at the base of this pit is in the position of the intermaxillary foramen of trionychids, but is interpreted as an artifact of preservation because it is irregular in shape. The triturating surface is widest lateral to the posterior half of the internal nares. At its maximum width, the triturating surface is much narrower than in Adocus. Lateral to the internal nares, the lingual ridge is high and sharp. The internal nares are oval openings relatively wider than in Adocus and separated by a relatively wider internarial bar. The palatines roof the posterior end of the internal nares and extend lateral to them, reaching the medial edge of the triturating surface. The palatines are not truncated anteriorly as they are in Nanhsiungchelys and members of the Trionychia, so the orbit has only a small area of exposure looking dorsally through the foramen orbito-nasale. The foramen palatinum posterius is preserved only on the left side of the skull. It is larger than in Adocus and differs in its position. In Zangerlia, the foramen is located between the palatine and pterygoid, the primitive position, whereas in Adocus, Baptemys, and Dermatemys the foramen palatinum posterius is surrounded entirely by the palatine. The processus pterygoideus externus, preserved only on the left side of the skull, is longer than in Adocus and does not have as strongly concave a posterior edge. The foramen posterius canalis carotici interni is located entirely within the pterygoid well anterior to its posterior edge. A large foramen basisphenoidale is present between the basisphenoid and pterygoid, a feature that Brinkman and Nicholls (1993) interpreted as primitive for eucryptodires and equivalent to the foramen carotico-pharyngeale of Chrysemys (Albrecht 1967). Poor preservation of the bone in this area prevents identification of the canalis caroticus lateralis or canalis caroticus internus, both of which should be visible within the foramen basisphenoidale. The basisphenoid has only a small area of exposure on the palate. The small size of ventral exposure of the basisphenoid and its rectangular shape differ from the condition in Adocus, where the basisphenoid is large and triangular in ventral view. The lower jaws, present in specimen IVPP V020788-7 (Fig. 6), are incompletely preserved, the postdentary portion of the right ramus is missing, and the articular is missing from the left. The triturating surface has a shallow dentary pocket with a convex medial edge. This pocket opposed the sharp lingual ridge of the maxillary triturating surface. It is possible that this edge is homologous to the maxillary tooth present in some other trionychoids. The coronoid process is located at about the middle of the lower jaw and is lower than that of either Adocus or Baptemys. A large fossa meckelii is present posterior to the coronoid process. The articular is not


Brinkrnan and Peng

preserved, so it is uncertain whether a retroarticular process was present. Sutures cannot be identified with confidence. Cervical vertebrae two to eight are present in specimen IVPP 020788-7 (Fig. 7), and the first thoracic vertebra is present in specimen IVPP 020790-5. Numbers two to seven are opisthocoelous. Cervical eight is biconvex. The articulation between the sixth and seventh vertebrae is doubled, although the two surfaces are continuous. The articulations between the seventh and eighth vertebrae and between the eighth cervical and first thoracic are doubled, and the two surfaces are separated from each other. Adocus differs in that the eighth cervical is opisthocoelous and has a single articular surface posteriorly. Centra two to seven are relatively long. Centrum eight is much shorter, less than half the length of the preceding centrum. The axis has a sharp mid-ventral ridge. The more posterior vertebrae each have a well-defined keel that extends ventrally as a narrow plate of bone (not preserved on the fourth centrum). On centrum three, this keel extends the full length of the centrum. More posteriorly the keel becomes relatively shorter, and by centrum six the keel is restricted to the anterior portion of the centrum. In contrast to Adocus, where the ventral keel of the eighth centrum is thickened and has small accessory keels on either side of the mid-ventral keel, only a single, unthickened keel is present in Zangerlia. Neural spines are not present on any of the cervical centra, although the axis has a mid-dorsal ridge extending the length of the neural arch. The zygapophyses of all the cervicals are strongly divergent, forming an X in dorsal view. The length of the neural arch measured mid-dorsally between the bases of the pre- and postzygapophyses decreases from the axis to vertebra six, then increases slightly. On centrum two to five, the postzygapophyses emerge from the middle of the neural arch and extend nearly straight dorsolaterally. In cervicals six and seven, the postzygapophyses originate from an increasingly more anterior position and become increasingly more curved, leading to a massive hook-shaped structure on cervical eight. In lateral view, the postzygapophysis of cervical eight originates from an anterior position on the centrum and incorporates most of the neural arch (Fig. 7G). Transverse processes are located below the prezygapophysis. These processes are of very small size on the axis, increase in size on vertebrae three to six, and decrease in size on the more posterior vertebrae. The transverse process of the third vertebra is barely separated from the prezygapophysis. On the fifth and sixth cervicals, the transverse process is a large structure that points ventrally. The first thoracic vertebra is low and wide and has a rounded ventral surface and ventrally facing concave proximal articular surfaces. The first thoracic rib is relatively short. It articulates with the first thoracic vertebra along the anterior half of the centrum. None of the remaining thoracic vertebrae are visible. Both right and left pectoral girdles are present in specimen IVPP 020788-5. The scapular and acromion processes of the scapula meet at about right angles (Figs. 8A, 8B). The scapular process is rod-like. The acromion process is flattened and is bowed concave downwards. Also, the blade of the acromion process is twisted, the base of the process being nearly vertical in cross section, and the distal end

being nearly horizontal. The coracoid (Figs. 8C, 8D) is a paddle-like structure sutured to the acromion process at an acute angle. The humerus is short and strongly curved (Figs. 9A, 9C). The humeral head is oval in end view. The greater trochanter (medial process) of the humerus is much larger than the lesser trochanter (lateral process), and is directed only slightly lateral relative to the long axis of the humerus. The distal articular surface is narrow and faces strongly ventrally. The radius and ulna (Figs. 9D, 9E) are short, about half the length of the humerus. Both elements are nearly straight. The ulna is a massive bone, with little constriction of the shaft region. The proximal articular surface is triangular in proximal view, with a well-developed olecranon process. The radius has a rounded, concave proximal end, and an expanded, flattened distal end. The pelvis of IVPP 020788-5 is preserved in place, but is exposed in ventral and anterior view. The dorsal blade of the ilium is tall but not greatly expanded. Undescribed pelvic elements of Basilemys (e.g., TMP 82.19.231) show that the ilium had a similar structure in that taxon. The ventral plate of the pelvis is short and wide. The thyroid fenestra is large and not divided by a pubis-ischium contact at the midline. The ischium forms a nearly vertical plate, with the metischial processes reduced to thickened rugose areas projecting only slightly posteriorly from the vertical plate. The pubis is composed of two portions, a lateral pillar formed by the acetabular portion and the pectineal process, and a triangular ventral plate that meets its fellow along the midline. The pectineal process is stout, being nearly circular in cross section. The ventral end of this process ends in a rugose area that rested on the plastron. The ventral plate has a weak suture with the opposite pubis at the midline. The posterior portion of this plate is nearly horizontal, and the anterior portion curves ventrally, so is nearly vertical. The femur (Fig. 1C) is sigmoidal, although slightly less so than the humerus. The intertrochanteric fossa is deep and bordered distally by a low ridge connecting the base of the two trochanters. The distal end of the femur is wider than that of the humerus and does not project as far ventrally. However, as with the humerus, the articular surface faces ventrally and is divided into two distinct condyles. Little detail can be seen on the tibia. The fibula is a slender element, little expanded at either end. No trace of ridges or crests are visible on its shaft. Well-preserved feet visible in ventral view are present in specimen IVPP 290690-6 (Fig. 1C). The tarsus includes a single astragalocalcaneum, as in turtles generally. Four toes are present, each with two phalanges. The basal phalanx is a short element, higher than it is long. Dermal ossicles are scattered around the feet. As in Basilemys, these are conical elements with a roughened surface.

Discussion Zangerlia neimongolensis and Z. testudinimorpha are similar to one another but differ significantly from other members of the Nanhsiungchelyidae (Nanhsiungchelys and Basilemys). They have a relatively shorter carapace, with a short posterior plastral lobe, and the presence of a strong knob at the posterior end of the neural series marking a change in slope from the



dorsal to the posterior edge of the carapace. The last two of these features are considered to be uniquely derived for the genus within the Nanhsiungchelyidae. The anterior lobe of the plastron, known only in Z. neimongolensis, differs from that of Nanhsiungchelys and Basilemys in being rectangular in shape and in having a broad anterior edge. In Nanhsiungchelys and Basilemys, the anterior lobe is triangular in shape and the anterior edge is very narrow. Zungerlia is likely primitive in this feature. Zungerlia neimongolensis differs from Z. testudinimorpha most significantly in the arrangement of scutes covering the bridge. The bridge marginals of Z. neimongolensis are similar to those of Basilemys and Nanhsiungchelys in that the marginal~extend far ventrally onto the bridge, reaching a line connecting the inguinal and axillary notches. In all three the medial end of the sixth inframarginal is markedly expanded. Zungerlia neimongolensis is distinctive in that the fourth marginal scute is retracted, so does not contact the abdominal scute. In Z. testudinimolpha, the marginals do not extend as far ventrally, the sixth marginal is not strongly expanded, and the inframarginals are irregularly developed. Since the right and left sides of the shell of Z. testudinimolpha do not match one another, this arrangement may be an individual anomaly. However, in the absence of independent evidence for this, the arrangement of the marginals and inframarginals in Z. testudinimolpha is considered an autapomorphic feature of that species. Zungerlia testudinimolpha also differs from Z. neimongolensis in the size of the entoplastron, the sinuosity of the midline sulcus, and the absence of a midline carapacial keel. The entoplastron of Z. testudinimorpha was not preserved, but based on the hyoplastron, Mlynarski (1972) concluded that it is at most a small element. In Z. neimongolensis, the entoplastron is a large pentagonal element that extends far posteriorly. The midline sulcus in Z. testudinimorpha is straight or at most weakly sinuous on the posterior lobe of the plastron. In Z. neimongolensis, the midline sulcus on the posterior lobe of the plastron is highly sinuous. A mid-dorsal keel is present in Z. testudinimolpha, whereas Z. neimongolensis has a rounded dorsal surface or possibly a shallow groove running along the mid-dorsal surface of the shell. In all these features, Z. neimongolensis is similar to Nanhsiungchelys and at least some species of the genus Basilemys. Thus these character states are interpreted as primitive for both the genus Zangerlia and the family Nanhsiungchelyidae. Zangerlia is derived relative to Nanhsiungchelys and similar to Basilemys in the loss of the second inframarginal, absent in both Z. neimongolensis and Basilemys. Zungerlia is primitive relative to Basilemys in the presence of a large third marginal scute in at least some individuals, and in the absence of a narrow extension from the posterolateral corner of the abdominal scute between the inguinal and femoral scutes to the inguinal notch. This extension has a sulcus separating it from the abdominal scute in B. variolosa (preserved in specimen TMP 94.666.28), but not in B. praeclara (Brinkman and Nicholls 1993). We consider the B. praeclara condition to be primitive for the genus, and identify the narrow scute between the inguinal and femoral scutes as an extension of the abdominal scute. The presence of this feature is interpreted as an autapomorphic character of Basilemys. The presence of band-shaped gular scutes that meet on the

midline and separate the intergular from the humeral scutes is a derived feature shared with B. sinuosa and B. praeclara. In the primitive condition, seen in N. orientalis, B. variolosa, B. nobilis, and Adocus, the gulars are triangular scutes that generally do not extend onto the entoplastron and never meet on the midline. The similarities in the shape of the gular scutes in Zungerlia and Basilemys are interpreted as independently derived character states. In summary, the family Nanhsiungchelyidae is considered to be a well-defined monophyletic unit on the basis of derived features of the plastron and carapace. Within this family, Zungerlia is interpreted as the sister taxon to Basilemys and they are, in combination, the sister group of Nanhsiungchelys.

Phylogenetic position of the Nanhsiungchelyidae Previously, the only member of the Nanhsiungchelyidae represented by cranial material was Nanhsiungchelys. Sirnilarities in the skull of Nanhsiungchelys and the Trionychia suggested a sister-group relationship between these taxa relative to Adocus (Meylan and Gaffney 1989). However, many of the characters that unite Nanhsiungchelys and the Trionychia are not present in Zangerlia. These include differences in the degree of cheek emargination (well developed in Zangerlia but weakly developed in Nanhsiungchelys and the Trionychia), the degree of reduction of the vomer (not reduced in Zungerlia but reduced in Nanhsiungchelys and the Trionychia), and in development of the processus ptyerygoideus externus (present in Zungerlia, reduced or absent in Nanhsiungchelys and the Trionychia). In all these features, the condition seen in Zangerlia is interpreted as primitive for the family Nanhsiungchelyidae. In order to evaluate the phylogenetic significance of this new information the data set used by Meylan and Gaffney (1989) was modified by including Zangerlia in place of Nanhsiungchelys and Basilemys. Zangerlia was used as the sole representative of the family Nanhsiungchelyidae because it was assumed that within the family it retained the primitive states of the characters used. This will be tested in the future by information from the skull of Basilemys that is currently under study (Canadian Museum of Nature specimen NMC 8890). In addition, recently published information on the structure and relationships of primitive eucryptodires has provided a more detailed understanding of the outgroups appropriate for interpreting the polarity of character states within the Trionychoidea. In particular, Peng and Brinkman (1994) argued that Xinjiangchelys is more closely related to the Centrocryptodira, a clade including all living cryptodires, than is Plesiochelys. Further, Brinkman and Peng (1993a, 1993b) argued that within the Centrocryptodira the macrobaenids, such as Ordosemys, and the sinemydids, such as Sinemys, are the most primitive known taxa. Thus these taxa are here used to reevaluate the polarity of character states within the Trionychoidea. The revised list of characters and their states is given in Table 1. The polarity of four characters was revised. These are character 3 (foramen posterius canalis carotici interni completely surrounded by pterygoid), character 14 (scutes sulci of skull roof), character 29 (plastron strongly sutured to carapace at bridge), and character 42 (cheek emargination reaches level of orbit).

Brinkman and Peng

Table 1. Characters and character states used in the analysis of relationships of the members of the Trionychoidea. Character state

n


Character 1. Foramen stapediotemporale 2. Size of foramen caroticum laterale (FCL) relative to size of foramen anterius canalis carotici interni (FACCI)* 3. Foramen posterius canalis carotici interni ventral in position and completely surrounded by pterygoid 4. Basis tuberculi basalis 5. Maxillary "tooth" 6. Commissural ridge 7. Premaxillae fused 8. Foramen intermaxillaris 9. Vomer reduced 10. Palatine truncated anteriorly 11. External process of pterygoid 12. Basisphenoid -palatine contact 13. Incisura columellae auris closed 14. Scutes sulci of skull roofing bones 15. Skull roofing bones sculptured 16. Frontal bones enter orbit 17. Maxilla contacts quadratojugal 18. Retroarticular process 19. Three keels on carapace 20. Neural formula: 6>4