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Albanerpetontid from the Upper of Middle Asia

JAMES D. GARDNER and ALEXANDER O. AVERIANOV

Gardneą J.D. & Aveńanov, A.o. 1998. Albanerpetontid amphibians from the Upper Cretaceous of Middle Asia. -Acta Palaeontologica Polonica 43,3,453-4ó7.

We review the fossil record of Asian albanerpetontids. The three dentaries previously attributed to the two species of. Nuhtsurus Nessov, 1981 (lower and Coniacian, Uzbekistan) are from albanerpetontids, but none are distinctive below the familial level. We thus designate the nłlmesNukusurus, N. insuetus Nessov, 1981, and N. sodalis Nessov, 1997 as nomina dubia within the Albanerpetontidae. Two dentaries (lower Cenomanian, Uzbekistan) descńbed herein for the first time supplement the known record of Asian albanerpetontids. The holotype atlas and only specimen of the supposed albanerpetontid B ishara bacl

Key words: Albanerpetontidae,Bishara, Cretaceous,Kazakhstan, Kirghizia, Nuku- surus, Uzbekistan.

James D. Gardner [[email protected]], I-aboratory for Vertebrate Paleontology and Departtnent of Biological Sciences, University of Alberta, Edmonton, AlbertaT6G 289 Canada. Alexander O. Averinnov [[email protected]], Zool.ogical Institute,Russian Acade- my of Sciences, Universitetsl

Introduction

The Albanerpetontidaeare small-bodied, superficially salamander-likeamphibians known almost exclusively by rare articulatedskeletons and abundantbones from the Middle -Mioceneof Laurasia(e.g., Estes & Hoffstetterl976;Estes 1981;Fox & Naylor 1982; Milner L994; McGowan & Evans 1995; Nessov L997). The higher level affinities of the Albanerpetontidaeare unresolved (Milner 1988, I993a, 1994). 454 Albanerpetontid amphiblałzs; GARDNER & AVERIANOV

5 5 o z

5 o o z

620E 660E 700E 7 40E

Fig. 1. Map of Middle Asian fossil localities mentionedin text. Insetmap shows locations of Kazakhstan, Kirghizia, and Uzbekistan and approńmate areashown in larger map. Symbols: O _ Upper Cretaceous locality; A - Jurassic locality. Distance betweenlocalities I and2 is exaggerated.Localities: 1 - Chelpyk locality, Uzbekistan,Upper Cretaceous(lower Cenomanian)Khodzhakul Formation;2 - Sites SSHD-8 and -8a, Sheikdzheili locality, Uzbekistan, Upper Cretaceous(lower Cenomanian)Khodzhakul Formation; 3 - Sites CBI-4v and -17, Dńyrakuduk locality, Uzbekistan, Upper Cretaceous(Coniacian) Bissekty Forma- tion; 4 - Tashkumyr locality, Kirghizia, (Callovian) BalabansayFormation; 5 - Baybishe locality, Kazakhstan,Upper Cretaceous(upper -?Campanian) Bostobe Formation.Map modified from Nessov (1988:fig. 1) andNessov et al. (1994:fig.2).

Originally they were regarded as prosirenid salamanders(e.g., Estes & Hoffstetter 1976;Estes 1981;Duellman & Trueb 1986;Trueb & Cloutier I99I), but it is more likely that they are adistinct lissamphibianlineage not otherwiseclosely relatedto the (Fox & Naylor 198f; McGowan & Evans 1995).Four albanerpetontidgenera have been iecognized to date. These are Albanerpeton Estes & Hoffstetter, 1976 (Aptian-,; Miocene, France), McGowan & Evans, t995 (-,Europe),'NukusLrus'Nessov, 1981 (lowerCenomanianand Coniacian, Uzbekistan), and Bishara Nessov, 1997 (upper Santonian-?Campanian, Kazakhstan)(e.g., Estes & HoffstettęrI976; Estes 1981;Nessov 1981,1988, 1997; Fox & Naylor 1982;McGowan & Evans 1995;McGowan 1996;McGowan & Ensom 1997;Gardner 1996).The two Asian generaare known by only threejaws and an atlas, none of which havebeen adequatelydescribed, figured, or comparedwith homologous bones from other albanerpetontidtaxa. The statusof thesesupposedly endemic Asian taxa is thusunclear, a situationthat frustrates attempts to examinethe phylogeneticand paleobiogeographichistory of the Albanerpetontidae. ACTA PALAEONTOLOGTCA POLOMCA (43) (3) 455

external nutritiveforamina dental

Imm openingfor Meckeliancanal

symphysealprongs unnamedpit symphysealeminence D

scar for attachment of intermandibularismusculature

Fig. f. Osteological terms for albanerpetontiddentaries. A-D. MNHN.LGA49, Albanerpeton inexpecta- tum Estes & Hoffstettel 1976; nearly complete right dentary lacking posteńormostend, labial, lingual, dorsal, and ventral views; La Grive-St. Alban, France, middle Miocene.

In this paperwe (1) redescribeand refigurethe threedentaries attributed by Nessov ,Nuktłsttrus,, (1981'1988, 1997; Nessov & Udovichenko1986) to the two speciesof (f) cnttcaTlyexamine the statusof 'Nukusurus' and its two species,(3) describe two recently identified albanerpetontiddentaries from the Cretaceousof Uzbekistan, (4) examine the identity of the holotype atlas and only specimenof the supposedalbaner- petontidBishara, (5)review otherreports(Nessov 1981, 1988, 1997) of albanerpeton- tid fossils from Asia, and (6) speculateon the history of Asian albanerpetontids.

Terms, conventions' and institutional abbreviations: We follow Nessov et ąI. (1994)for names of localities and formationsand in using the term 'Middle Asia'for the region encompassingKazakhstan, Kirghizia, Tajikistan,Turkmenistan, and Uzbe- kistan (Fig. 1).A taxonomicname in quotes(e.9., 'Nukusurus') denotes a taxon as it was understoodby earlier authors.Fig.Z shows osteologicalterms for dentaries;terms 456 Albanerpetontid amphiblans: GARDNER & AVERIANOV for other elementsfollow Estes (1981) and Fox & Naylor (1982).Tooth positions are counted from the anterior end of the tooth row, unless statedotherwise. Institutional abbreviationsare as follows: CCMGE, Chernyshev Central Museum of Geological Exploration, Saint Petersburg;.FMNH, Field Museum of Natural History Chicago; MNHN Musóum National d'Histoire Nafurelle, Paris; OMNH, oklahoma Museum of Natural History Norman; UALVP, University of Alberta Laboratory for Vertebrate Paleontology,Edmonton; and ZN, TnologScallnstitute, Russian Academy of Scien- ces, Saint Petersburg.

Redescription of lllukusurus insuetns Nessov, 1981 nomen dubium and JlL sodalis Nessov, L997 n;omert dubium

Family AlbanerpetontidaeFox & Naylor,1982 Genusindeterminate (- NukusurusNessov, L981 nomen dubium) - ,Nukusurus Remarks. Two species, insuetus, Nessov, 1981 (Nessov's Ępe species) and W. 'Nuhtsurus'. sodnlis' Nessov, 1997, have been included in We consider these three names to be nomina dubia within the Albanerpetontidae. and species indeterminate A (- Nukusurus insuetus Nessov, 1981 nomend.ubium) Fig. 3A-H. Material.-ZIN PHA K 774, incomplete dentary and fragmentary angular, Nessov's (1981) 'Nukusurus holotype of insuetus'; and CCMGEf4IllflTT ,nearly complete dentary and fragmentary angular, referred by Nessov & Udovichenko (1986) and Nessov (1988) to W. insuetus'. Localities, horizon, and age. - ZIN PHA K 77-4: Chehpyk localiĘ; and CCMGE24I|12I77: site SSHD-8, Sheikdńeili localĘ; Kyzylkum Desert, north-cenffal Uzbekistan (Frg. 1); upper part of Khodzhakul Formation; lower Cenomanian (Nessov et al.1994; Nessov 1997). Description. - ZN PHA K 77-4 (Fig.3A-D) is an incomplete left dentary and the anterior tip of a left angular. The angular is displaced labial to its point of articulation, in the opening for the Meckelian canal, with the dentary. The dentary is missing much of the area for attachment of the postdentary bones and all but the base of the symphyseal prong. The dentary is moderately robust and small, 4.8 mm long as preserved. The dental parapet is relatively uniform in height along its length and its dorsal edge is nearly straight in labial view. The dentary is smooth externally, except for a row of five small external nutitive foramina. The posteriormost foramen is lateral to the sixteenth tooth position. The symphyseal eminence is not prominent. Internally, the anterior edge of the opening for the Meckelian canal is in line with the twenty-first locus. The posterior end of the tooth row is broken, and we estimate that at least the posteriormost six loci are missing .T\e 23 preserved loci include 16 tooth bases, six empty tooth slots, and at the fust locus a tooth slot containing an in situ replacement crown. Judging by the broken pedicles and empty tooth slots, the teeth were relativeĘ gracile and those located about one-third of the distance along the ramus were only slightly enlarged relative to other teeth along the tooth row. CCMGE 241lIfI77 (Fig. 3E-H) is a more nearly complete left dentary that lacks the posterior part of the area for articulation with the postdentary bones and preserves the anterior end of the angular in articulation. This specimen is 5.4 mm in preserved length, and came from an individual about one-quarter again as large as the individual represented by ZN PHA K 77-4.Like the latter dentary, CCMGE 241112177 is elongate, moderately robust, and the dental parapet is relatively uniform in height along its length. A row of four small external nutritive foramina penetrates the ĄCTA PALAEoNToLOGICA POLONICA (43) (3) 451

Fig. 3. Dentańes of Nukusuru.r Nessov, |981 nomen dttbiutn and Albanelpetontidae indeterminate fiom the Upper Cretaceous of Uzbekistan. A-D. ZII{ PHA K 7l -4, Nukusurus insuetus Nessov, I98l nomen clubiutn; incomplete left dentary and an.Ęular,labial, lingual, occlusal, and ventral views; Chelpyk locality, Khodz- hakul Formation, lower Cenomanian. E-H. CCMGE f4llIflll , N. insuetusNessov, I98I nomen dubium, nearly complete left dentary and incomplete angular, labial, lingual, occlusal, and ventral views; Sheikdzheili locality, Khodzhakul Formation, lower Cenomanian. I, J. CCMGE lI1l1fl17, Nukusurus :otlalis Nessov, |99J nołnen dubium; fragmentary right dentary, labial and lingual views; Dzhyrakuduk locality. Bissekty Fomation, Coniacian. K. ZIN PC I146, Albanerpetontidae indeterminate; posterior end of right dentary, lingual view; Sheikdzheili locality, Khodzhakul Formation, lower Cenomanian. L. ZIN PC 2146, Albanerpetontidae indeterminate; posterior end of right dentary, lingual view; Sheikdzheili locality, Khodzhakul Formation, lower Cenomanian. Scalc bzLr1 mm. All SEM micrographs.

dentary externally, with the posteriormost foramen situated lateral to the seventeenth tooth position. The dentary ventrally and ventrolaterally bears a shallow and anteroposteńorly elongate scar, bounded labially by a low ńdge, for attachment of the intermandibularis musculature. The sym- 458 Albanetpetontid amphibrans; GARDNER & AVERIANOV

physeal eminence is more prominently developed than on ZIN PHA K 71-4 and two symphyseal prongs are preserved intact. Just posterior to the bases of the symphyseal prongs, an unidentified small and flattened fragment of bone adheres to the lingual edge of the subdental shelf. More posteńorly, the anterior margin of the opening for the Meckelian canalis in line with the twenty-third tooth position, or the ninth locus from the posterior end of the tooth row. The intact tooth row consists of 32 loci, including 11 nearly complete teeth, 12 broken teeth, and nine empty tooth slots. Teeth are highly pleurodont, non-pedicellate, closely spaced, gracile, and not particularly elongate. Tooth apices are abraded, but are clearly labiolingually compressed and chisel like. Broken tooth bases and empty tooth slots indicate that the teeth were largest about one-third of the distance along the tooth row, but not markedly so. Genus and speciesindeterminate B (=Nukusurus sodnlis Nessov,1997 nomen dubium) Fig. 3I, J. Material. - CCMGE III|I2I7T ,fragmentarydentary, designated by Nessov (1997)as the holotype 'Nukusurus and only specimen of sodalis'. LocaliĘ horizon, and age. - Site CBI-17, Dzhyrakuduk locality, KyzylkumDesert, north-cenfal Uzbekistan (Fig. 1); upper part of ; Coniacian (Nessov et al. 1998). Descńption. - CCMGE II1./I2I77 (Fig. 3I' J) is a fragment of a right dentary missing the symphyseal region and all of the bone posterior to the opening of the Meckelian canal. The preserved part of the dentary is 4.0 mm long, and appears to be from an individual that was about the same size as that representedby ZIN PHA K 77-4.The dorsal edge of the dental parapet is hońzontal along its preserved length, but it is lowerthan in the two dentaries descńbed above. Arow of four tiny external nutritive foramina is present labially and a faint scar for the intermandibularis musculature is developed ventally. The tooth row is incomplete anteriorly and posteńorly. The preserved section of the tooth row includes about 21 tooth positions, consisting of approximately equal numbers of broken tooth bases and empty slots. 'Nukusurus Remarks. - Although Nessov & Udovichenko (1986) used the name sodalis', the first valid publication of this name was by Nessov (1997). Nessov (1988) previously listed CCMGE 'new 'new III|ILITT as belonging to a form of albanerpetontid' (p. 478) and a albanerpetontid ' (caption for pl. 14:31).

Evaluation of ffuknsurus Nessov, 198L nomen dubhrm and its included species

Status of Nukusurus Nessov, 1981 nomen dubium. - Nessov (1981) diagnosed 'Nukusurus', then known only by ZIN PHA K77-4, using 11 featuresof the dentary. We consider each of thesefeatures below. (1) Dentary small. Albanerpetontidswere small and had coffespondingly small bones. For example, articulated skeletons of Celtedens megacephalus and C. ibericus from theLower Cretaceousof Europe have snout-ventlengths of about50 mm (McGowan & Evans 1995;Gardner pers. obs.). Dentaries attributed to 'Nukusurus' aire small in absoluteterms, but they are comparablein size to dentariesknown for most other albanerpetontidspecies. There is no evidencethat body size, and by implication elementsize, differs among genera.However, body size does differ among speciesof AIbanerp et on (G ardnerin preparation). (2) Ornament absent.Ornament develops ontogeneticallyon the labial surface of the dentary n Albanerpeton inexpectatum,and this feature is diagnostic for larger ACTA PALAEONTOLOGTCA POLONTCA (43) (3) 459 individuals of this species (Gardner in preparation).The labial surface of the dentary is smooth and unornamentedin all other albanerpetontids,indicating that lack of ornamenton the dentaryis not diagnostic for 'Nukusurus'nor for any other albanerpe- tontid taxon. (3) Dental parapet low. In absolute terms, the dental parapet in albanerpetontid dentaries is low. Even in dentańes of large-bodied species such as Albąnerpeton inexpectatumand A. galaktion, the dentalparapet is rarely higher than about 1.5 mm. Relative to overall dentary size, however, the dental parapetin albanerpetontidden- taries is actually rather high. The dental parapetin dentariesof 'Nukusurus'is com- parable in height to the parapetin similar-sized dentariesof other albanerpetontids; hence,a low dentalparapet is not diagnostic for 'Nukusurus'. In labial outline,the dorsal edgeof the dentalparapet is straighttoshallowly convex dorsally on the three dentariesof 'Nukusurus'. This is the condition seenin dentaries of most other albanerpetontids,and it is clearly is not diagnosticfor genera.The only appreciablevariation in this featureoccurs at the specific level within Albanerpeton, where in dentariesof A. nexuosrzsthe dorsal edge of the dental parapetis strongly convex to angular dorsally (seeEstes 1964:figs 43e, 44c). (4) Symphyseal prongs present.Albanerpetontid dentaries each bear one or two prongs that arise from the posteriorpart of the symphysis and projectmedially. In life, these prongs formed a mortise-in-tenonjoint with complementary prongs on the oppositedentary. Symphyseal prongs are an autapomorphyfor the Albanerpetontidae (Milner 1988, 1994),and their presenceis diagnostic only at the familial level. (5) Size of symphysealprongs. Nessov (1981)stated that dentaries of 'Nukusurus' differ those of ,Prodesmodon,(= Albąnerpeton nexuosus)in having smaller Sym- physeal prongs. Differences in the relative sizes of the symphyseal prongs between these two taxa reflect nothing more than the larger size of the two dentariesof A. nexuosus figured by Estes (1964: figs 43e, 44a--c)and thus are not taxonomically significant. (6) Pit on ventral surface of symphysis. Albanerpetontiddentańes have a small, unnamed pit on the ventral surface of the symphysis, between the bases of the symphysealeminence and symphysealprongs. An unnamedforamen in this pit opens dorsally into the Meckelian canal. As this pit and foramenoccur in all albanerpetontid dentaries,their presenceis neither diagnostic for generanor for species. (7) Size of pit on ventral surface of symphysis.According to Nessov (1981), dentariesof 'Nukusurus'differ from those of 'Prodesmodon' (=Albanerpeton nextto- srzs)in having a smaller pit on the ventral surfaceof the symphysis.The size of this pit varies ontogeneticallyand this variation is not taxonomically significant. (8) Meckelian canal long. The Meckelian groove in albanerpetontiddentaries is enclosedas abony canal along most of its length.The relative length of the Meckelian canal does not differ among albanerpetontidtaxa, because the anterior edge of the openingfor the canal consistentlylies below the seventhto ninth loci from the posterior end of the tooth row. ZIN PHA K77-4lacks the posteriorend of the tooth row, which createsthe impressionthat the openingfor theMeckelian canal lies more posteriorward in this dentary. (9) Number of teeth.Nessov (1981) estimatedthat ZIN PHA K77-4had 17-23 teeth when complete, and on this basis he proposed that dentaries of 'Nukusurus' 460 Albanetpetontid amphibians: GARDNER & AVERIANOV differed from those of 'Prosiren' (= Albanerpeton arthridion) in having fewer teeth. Given that ZIN PHA K77-4lacks the posterior section of the tooth row, the original number of loci for this dentary,when it was complete,cannot be estimatedwith any confidence. The only 'Nukusurus' dentary with a complete tooth row is CCMGE 24I1I2I77, andthis specimenhas 32 tooth positions. This neither differs appreciably from the 33 loci in FMNH PR806 (Estes 1969:ftg. fI), theonly dentaryof A. arthńdion with a complete tooth roq nor from tooth counts in larger dentariesof other albaner- petontidtaxa. (10) Teeth largest near anterior end of dentary.[n albanerpetontiddentańes, the largestteeth occur aboutone-third of the distancealong thętooth row from the anteńor end, and become smaller anteriorwardand posteńorward along the tooth row. This patternoccurs in all albanerpetontiddentaries and it is clearly not diagnosticfor genera. Variation in the relative heterodontyof the anteriorteeth is seenwithin Albanerpeton, withA. nexuosushaving dentariesin which the largestteeth are considerablyenlarged relative to othersalong the tooth row (Estes 1964:figs 43e, 44c). (11) Teeth less pleurodont in posteńor part of tooth row. As tooth size decreases posteriorwardalong the albanerpetontiddentary, the posteriormostteeth become little more thantiny denticles.Due to their shortenedpedicles and thereforeręduced area for attachment,these posteriormost teeth are less firmly attachedto the inner wall of the parapet.Nevertheless, these teeth retain their pleurodontattachment. This patternis not taxonomically significant becauseit occurs in all albanerpetontids. In short,none of the 11 featuresused by Nessov (1981)to diagnose 'Nukusurus' are informative at the generic level among albanerpetontids.We see no other features in the three dentariesfrom Uzbekistan that can be interpretedas being diagnostic for albanerpetontidgenera. Given that it is uncertain which albanerpetontidgenus is representedby thesedentaries, we designatethe nźlme,Nukusurus, anomen dubium. Specific stafus of Nukusurus insuetus Nessov, 1981 nomen dubium and N. sodalis Nessov, 1997 nornen dubium. - It is evident from the preceding sectionthat neither of the dentańesattributed by Nessov (1981' 1988)and Nessov & Udovichenko(1986) to 'Nukusurusinsuetus' aredistinctive at the specific level. There is also no compelling morphological evidence that thesedentaries are from conspecific individuals. As it is uncertain which species is representedby Nessov's (1981) holotype dentary,we designatethe name 'N. insuetus'anomen dubium. Nessov (1997: p. 161) statedthat his holotype dentary of 'Nukusurussodalis' differed from dentariesof 'N. insuetus'in having a lower dentalparapet and larger teeth.We offer the following comments about these features:(1) The dental parapet in CCMGE ttt/t2l77 is indeed low in absolute and ręlative terms, but it is comparablein height to the parapetin most other albanerpetontiddentaries of similar size. In albanerpetontids,the dental parapet typically is low in small dentaries and becomes relatively taller with increased dentary size. Other features of CCMGE III/1LI77, such as its small size and weakly developedscar for the intermandibu- laris musculature,further suggestthat this dentaryis from a subadult.As such, we interpret the low dental parapet on this specimen as an ontogenetic feature of no taxonomic significance. (2) Tooth size is difficult to determine for CCMGE III|12I77, because the specimen lacks intact teeth. Examination of the original ACTA PALAEONTOLOGTCA POLOMCA (43) (3) 46r photographs(see Nessov & Udovichenko 1986: pl.f, ftg. 22) of the dentaryshow that this damage was not inflicted afterNessov described the specimen. Judging by the broken tooth bases and empty tooth slots, teeth on this dentary were probably similar in size to those on the two dentaries attributed to 'M insuetus'. CCMGE IIL|ILI77 cannotbe identified more precisely thanto the familial level, and for this reasonwe designatethe name 'N. sodalis' a nomendubium.

New albanerpetontid fossils from Middle Asia

Mateńa|. - ZIN PC 1146and2l46, incomplete dentaries. Localities, horizon, and age. - ZIN PC 1146: site SSHDa; and ZIN PC 2146: site SSHD-8; Sheikdzheili locality, Kyzylkum Desert, north-cenfral Uzbekistan (Fig. 1); upper part of Khodńakul Formation; lower Cenomanian (Nessov et al.I994;Nessov 1997). Description. - ZIN PC 1146 and 2146 (Fig. 2K, L, respectively) are incomplete right dentaries, comparable in size to CCMGE f4Il|2I77. Each lacks the anteńor one-third or so of the ramus, but retains more of the area for attachment of the postdentary bones than do the otherthree dentaries from Uzbekistan. The anterior margin of the opening for the Meckelian canal is in line with the seventh (ZIN PC 2146) and about the ninth (ZIN PC 1/46) locus from the posterior end of the tooth row, as it is in other albanerpetontid dentaries. In ZIN PC L146,the dorsal margin immediately behind the tooth row is intact and horizontal in lingual or labial view. Remarks. - Neither dentary can be identified below the familial level. One of these may be the 'prosirenid'dentary same specimen (CCMGE 203111657)reportedby Nessov (1981) as a small from an unspecified site at the Sheikdńeili localiĘ.

Re-interpretation of Bishąrą Nessov, L997

Nessov (1997: p. 161) named a new albanerpetontid genus and species, Bishnra backa, on an incomplete atlantal cenffum, CCMGE 240112177. This is the only specimen known for the taxon. The holotype was collected from the upper Santonian-?Campanian (Nessov et al. 1994; Nessov 1997) Baybishe localiĘ (Fig. 1)' located in south-centalKazakhstan in the middle or upper part of the Bostobe Formation. One of us (Averianov) has not been able to locate CCMGE 240112177 in the collections of the CCMGE or ZIN. Nevertheless, we can comment on the identity of this specimen based on published photographs(Nessov 1988: pl. 16, fig. 1,f;1997: pl. 10, fig. 3) that depict the fossil in anterior and ventral views. These photographs show an odontoid process flanked to either side by a vertical cotyle - features that confirm CCMGE 2401t2177 is an atlantal centrum. These photographs further demonstrate,however, that CCMGE 240|12177lacks characteństic feafures that are plainly visible in anterior and vental views on unequivocal albanerpetontid atlantes. These features include the following: odontoid process broad (width equal to or greater than one-half the width across the outer edges of the anteńor cotyles), gutter-like in anterior view, with concave dorsal surface and lateral edges confluent with dorsal margins of anterior coĘles; anterior coĘles slightly compressed dor- somedially_ventrolaterally and kidney-shaped in anteńor outline, with concave margin facing odon- toid process; and deep notch below odontoid process separating anteńor cotyles (Seiffert 1969: fig. 1B, C; Estes & Hoffstefter 1976: text-fig. 1A, E; Fox & Naylor I98f: ftg. lf; McGowan 1996: fig. 9a, c). CCMGE 240112177compares favorably with salamander atlantes, and we identify it as such. Consequently, the name Bishara backa denotes a salamander, not an albanerpetontid. 462 Albanerpeto;ntid amphibians.' GARDNER & AVERIANOV

Purported albanerpetontid fossils from Middle Asia

?Albanerpetontid frontal. - Nessov (1988) reported an uncatalogued albanelpetontid frontal from the Upper Jurassic (Callovian) Tashkumyr locality (Fig. 1), western Kirghizia, in the upper part of the Balabansay Formation. Wę cannot confirm the identity of this fossil, because it was never described or figured and one of us (Averianov) has not been able to locate it in collections of the CCMGE or ZIN. If the reported geological age and identity of this specimen are correct, it would be among the geologically oldest known albanerpetontid fossils (see below).

A B Fig.4. Distal ends of selectedalbanerpetontid and caudatehumeń in venfral view' A. OMNH 33516, Albanerpeton arthridion, left humerus;OMNH locality y706, Oklahoma, Antlers Formation, uppermost Aptian-lowermost Albian. B. CCMGE 183111657,Caudata indeterminate,right humerus;Dzhyrakuduk locality, Bissekty Formation, Coniacian. C. UALVP unnumbered,Ambystoma tigrinum (Caudata;Amby- stomatidae)'ńght humerus;southern Alberta, Canada,Recent. Scale bars 1 mm.

Salamander humerus. - CCMGE 183/11657 is the distal end of a right humerus (Fig. aB) thathas been referred to the Prosirenidae and Albanerpetontidae (Nessov 198I, L997, respectively). This humerus was collected from site CBI-4v, Dzhyrakuduk locality, Kyzylkum Desert, north-central Uzbekistan (Fig. 1), which lies in the middle part of the Coniacian-aged Bissekty Formation (Nessov et al. |998). Unequivocal albanerpetontid humeń are characteńsed by feafures such as having the shaft in line with the radial condyle, the distal end moderately wide, the radial condyle a relatively large hemispheńcal ball, and the ulnar condyle smaller than the radial condyle (Estes & Hoffstetter 1976: pL.9, figs 6,'7; McGowan & Ensom 1997: ftg. 2b:.here; Fig. 4A). We interpret CCMGE 183111657as a salamander humerus (Fig. 4B, C), because the shaft is offset from the radial condyle, the distal end is relatively wider, the radial condyle is a small ball with a flattened distal end, and the ulnar condyle is larger than the radial condyle.

Speculations on the history of Middle Asian albanerpetontids

The five dentariesdescribed above from Uzbekistan provide little direct information about the evolution of albanerpetontids,aside from confirming that the group was widespreadacross Laurasia during the Late Cretaceous.The record of albanerpetontids ACTA PALAEONTOLOGTCA POLOMCA (43) (3) 463 elsewhereis betteĘbut significant temporal and geographicgaps remain. In general, these gaps correspondto intervals and areas from which nonmarinemicrovertebrate assemblagesas a whole are poorly documented.This suggests that breaks in the albanerpetontidfossil record are attributableat leastin part to taphonomicand collect- ing biases,and should not be interpretedas reflecting an actual absenceof albanerpe- tontidsin time and space.Despite theselimitations, some constrainedspeculations can be made about the Mesozoic history of Asian albanerpetontidsbased on the distribu- tions of fossils, land rnasses,and marine barriers shown in Fig. 5. The geologrcallyoldest albanerpetontid fossils datefromthelowerBathonian(Kriwet et ąl. 1997)of France (Estes1981) and the upperBathonian of England (Evans & Milner I994;McGowan l996).These occuffenceslikely underestimatethe time of origin for the family, an event that Milner (1994) suggestedoccurred no later than the Early . This date is supportedby hypothesesof higher level relationships of the (e.9.,Milner 1988, 1990, I993b; Trueb & Cloutier I99I; McGowan & Evans 1995; Laurin & Reisz 1997)constrained against fossil occulrences(e.g., Milner I993a). Except for a Lower Cretaceousrecord in Morocco (Broschinski & Sigogneau-Rus- sell 1996),albanerpetontids are known only from Laurasia and most likely originated there.Continental tetrapodassemblages of Triassic-Early Jurassic age are relatively cosmopolitan,indicating that therewere few barriers to overland dispersalduring this time (e.g.,Shubin & Sues I99I; Russell 1993;Sues 1997).In the absenceof fossils, the extentto which albanerpetontidswere able to disperseacross Laurasia during this interval obviously remains unknown. However, judging by distńbutions of other contemporaneousamphibians (Milner 1994),it would not be surprising if albanerpe- tontids also broadly distributedacross Laurasia by at least the Middle Jurassic. Regardless of when and where albanerpetontidsoriginated and what the early undocumentedbiogeographic history of the group might have been, the European Bathonian occunences show that albanerpetontidswere in Europe when the Turgai Straits flrst openedbetween Europe and Asia in the late Middle to early Late Jurassic. With the openingof thesestraits, Asia was isolatedfrom the remainderof Laurasia for about 50 million years (Gradsteinet ąI. 1995),until about the late . While it is possible that albanerpetontidswere already in Asia prior to the opening of the Turgai Straits and could have evolved vicariantly on the continent during its subsequentisolation, fossil evidencethat this occurredis lacking. Albanerpetontidsare reliably known from Asia when the continentwas connected first with Europe from about the Aptian-Coniacian by a series of intermittentland bridges acrossthe Turgai Straits,and then acrossthe Bering Isthmuswith the western subcontinentof Nonh America continuously from the latest Albian or earliest Ceno- manian to Maastrichtian. Fossils in Europe and North America predate the estab- lishment of these land bridges, and thus argue against albanerpetontidshaving dis- persed from Asia into Europe or North America. Evidence for faunal interchangeof any kind acrossthe Turgai Straitsduring the Aptian-Coniacian is lacking, in large part because the European record of nonmarine vertebratesfrom this interval is sparse (Buffetautet aI. 1981;Le Loeuff & Buffetaut1995). By contrast,considerable faunal interchangeocculred across the Bering Isthmusbetween western North America and Asia during the Late Cretaceous(e.g., Russell 1993; Sereno 1997).This interchange need not have been limited to large tetrapods,as evidenced by occunences of the 464 Albanerpetontid amphibiazs.. GARDNER & AVERIANOV

MiddleJurassic

.=o Europe o Asia 5 1t, a 'd 40 06 ol J Late Jurassic - Aptian

o.E Asia N. Am. o

o 10 11 s g^ Albian -

(u o ln oL s ; Coniacian

.Ą (E f o Europe (! U'

L. o o 14 (o ct) c f F Santonian - Maastrichtian

Fig' 5' Diagrammatic representationof Laurasian continents and disnibution of albanerpetontid-Funnell fossils from the Middle Jurassic{retaceous. Continentalreconstructions based on Barron (1987), (1990), and Smith (L994). et al. Dashed lines are intermittentland connections;abbreviations: N. Am. - North America - and W. Inter.Sea WesternInterior Seaway; symbols: O and numeral- Celtedens.A and numeral - Albanerpeton,'?'and - numeral unverified occurrence,and numeral- Albanerpetontidaeindeterminate. Localities: - 1 lower Bathonian, France; 2 _ upper Bathonian, England; 3 - ćallovian, Kirghizia;4 _ Kimmeńdgian,Portugat;5_Berriasian,England; 6-Barremian,Spain;7_Albian, Italy;8-lower Cenomanian' - Uzbekistan; 9 Aptian-Albian, USA; 10 - upper Albian-lower Cenomanian, USA; 11 - Turonian, - USA; 12 Coniacian, Uzbekistan; 13 - lower o. *iddl" Coniacian, USA; 14 - upper Campa- nian-lower - Maastrichtian,Spain; 15 lower and middle Campanian,Canada; and 16- upperMaastrichtian, USA. earliest scapherpetontidsalamanders in the upperAlbian of Uzbekistan (Nessov 19gl) and uppermost Albian-lowermost Cenomanian of Utah (Cifelli et al. in press). Ii albanerpetontidsdispersed into Asia from Europe or westernNorth Ameńca diuringthe ACTA PALAEONTOLOGTCA POLOMCA (43) (3) 465 late Early and Late Cretaceous,as is implied by continentalreconstructions and limited fossil occulrences,we would expect Asian albanerpetontidsto show close affinities with European or North American taxa. Testing of the ideas we have presentedhere must await the recovery from Asia of fossils that are more systematicallyinformative and sample a broadertemporal range than the five dentariespresently available. Prospects for recovering such fossils are promising, judging from the abundant and occasionally well-preserved amphibian bones that have already been collected from Middle Jurassic-Cretaceouslocalities in Middle Asia (e.g.,Nessov1988, 1997).

Conclusions

The Asian record of albanerpetontidsis limited to five indeterminatedentaries from the Upper Cretaceous(lower Cenomanianand Coniacian) of Uzbekistan. There are no endemic Asian albanerpetontids.The namesNukusurus, N. insuetus, and N. sodalis are nomina dubia within the Albanerpetontidae.The name Bishara denotesan indeterminatesalamander, not an albanerpetontid.These findings leave Albanerpeton(Aptian-Paleocene,NorthAmerica; Miocene, Europe) andCeltedens (Bathonian-Albian, westernEurope) as the only valid albanerpetontidgenera. Limited evidencesuggests that a Cretaceousdispersal from Europe or North Ameri- ca, rather than vicariance within Asia, may have played the more prominent role in the evolution of Asian albanerpetontids,but evidence for either scenario remains weak.

Acknowledgements

Our study was possible because Dr. N.B. Ananjeva carried the fossils described here from Saint Petersburg to Gardner in Prague. For access to comparative specimens we thank Drs. D. Goujet and J.-C. Rage (MNHN), Dr. R.L. Cifelli and R.L. Nydam (OMNH), Dr. R.C. Fox (UALVP), Dr. S.E. Evans (University College l,ondon), and Drs F. Barattolo, S. Bravi, C. Barberą and P. De Casfro (Dipartimento di Paleontologie dell'Universitd di Napoli). We also thank B. Badzio for tanslating part of Nessov's (1981) paper, G.D. Braybrook fortaking the scanning electron micrographs, and Drs G.E. Ball' M. Borsuk-BiaĘnicką R.C. Fox, Gao K., and A.R. Milner for reviewing earlier versions of our paper. Gardner's funding was provided by a University of Alberta Recruitment Scholarship and Dissertation Fellowship, and more recently by his wife, N.J. Marklund, and parents-in-law, G.T. and G.F. Marklund. Averianov thanks I.G. Danilov (ZN) for various hĘ during our sfudy.

References

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Płazy z todziny Albanerpetontidae z górnej kredy Azii Srodkowej

JAMES D. GARDNER i ALEXANDER O. AVERIANOV

Streszczenie

Rewizja azjatycŁjego Zapisu kopalnego albanerpetontydówpozwoliła potwierdzić obecnośćtej grupy na podstawiedwóch żuchwz dolnego cenomanuUzbekistanu, opisanych tu po raz pierwszy, otaz trzech okazów opisanych wcześniejprzez Nesowa z dolnegocenomanu i koniaku Uzbekistanu.Materiał nie wykazujejednak cech diagnostycznych pozwa|ających go określićponiiLej szczeb|a rodzajowego. Dlatego nazwy Nukusuru,r,N. insuetus Nessov, 1981 i N. sodalis Nessov, 1997 wypada nznaćZanominą dubia. Holotyp domniemanegoalbanerpetontyda Bishara backą Nessov, 1997 (górny santon_?kampanKazachstanu) _ pojedynczy dźwigacz _ na|ezy natomiast do salamandry, a nie albanerpetontyda.Tak więc jedynymi waznymi rodzajami albanerpetontydówpozostają Albanerpeton (Weda_miocen, Ameryka Północna i Europa) oraz Celtedens (środkowajura-dolna kreda, Europa). Na podstawie ograniczonego materiałukopalnego mozna przypnszczać, Ze w po- łowie kredy doszło do jednorźVowegolub kilkakrotnego zasiedlenia Azji przez albanerpetontydyz Europy lub Ameryki Północnej.