A stem-group frog from the Early Triassic of Poland sUsAN E. EVANS andMAGDALENA BORSUK-BIAŁYNICKA

Evans, s.E. & Borsuk-BiĄnicka, M. 1998. A stem-group frog from the Early Triassic of Poland. - Acta Palaeontologica Polonica 43,4,573-580.

Descńbed on the basis of disarticulated postcranial bones (vertebrae,humeri, ilia) from karst deposits of Scythian age at the locality of Czatkowice in the Kraków Upland, Poland, Czatkobątrachus polonicus gen. et sp. n. is the first salientian known from the Triassic of the Northern part of Pangea. It may be only slightĘ younger (about 5 MA) than Triadobatrachus massinoti (Piveteau, 1936) from Madagascar' the only EaĄ Triassic salientian known hitherto. Czatkobatrachus resemb(es Tńadobatrachus but is more derived in some features of the vertebrae and elbow joint. It provides evidence of a global distribution of stem-frogs at the very beginning of the Mesozoic, and suggests that the origin of the group must be sought in the Permian.

Key word s: Anura, Lissamphibia, Salientia,Triassic, Poland.

Susan E. Evans [[email protected]], Department of Anatomy and Developmental Biology, University College Inndon, Gower Street, London, WCIE 68T, England. M a gdale na B o r s uk-B i aĘni cka I bo r suk. b @ twarda. p an.p I], Ins Ę tut P ale ob i o l o gii P AN, ul. Twarda 5l/55, PL-00-818 Warszawa, Poland.

Introduction

Frogs (Anura) form a successfuland very distinctive componentof the modern biota. Their early history,however, remains very poorly known and this complicatesdiscus- sion of their origins, evolution, and relationships.Until now, the Triassic record has been based on a single specimen,Triadobatrąchus, from the Early Triassic of Mada- gascar(Rage & Roćek 1989)'but the morphologicaI,temporal (50 Ma) and geographi- cal gap betweenit and the earliest true frogs is considerable.The latter are currbntly representedby a small group of Early to Middle Jurassic taxa - Prosalirus (Shubin & Jenkins 1995)from the Early Jurassic of North America, the slightly younger Veraella and Notobatrąchus from Argentina (Baez & Basso 1996)' and the Middle Jurassic Eodiscoglossus from England (Evans et aI. 1990).Like modern frogs, theseJurassic taxa were short-bodiedand tail-less, with long hind limbs. Tńadobatrachus,in con- 574 A steam-group frog: Evans & Borsuk-BiĄnicka trast, was relatively long-bodied, had short hind limbs, and retained at least six tail vertebrae,although it sharesa small suite of characterswith the younger taxa - most notably the anteriorly-elongatedblade of the ilium. Clearly, thereis a substantialhiatus in the early record of Salientia (Milner 1988),and the recovery of additional Triassic material is a priority. Czatkowice is a limestone quarry in the Kraków Upland region of Poland. The microvertebratematerial described here comes from a single fissure, Czatkowice I (Paszkowski & Wieczorek 1982).The karstificationphase during which the infillings of Czatkowice 1 were depositedmay have lasted from the Late Permian to the Early Triassic, but ended when the entirę region was submergedby the Róth Transgression at the end of the Scythian (about f38 Ma). Czatkowice 1 is yielding a diverse Early Triassic microvertebrateassemblage including a range of reptiles (procolophonids, lepidosauromorphs,prolacertiforms and basal archosaurs),as well as fish and amphi- bians. Amphibian bones are extremely rare, but they include elements which show morphologlcal featuresunique to the Salientia. Institutional abbreviations: MNHN - Museum National d'Histoire Naturelle, Paris; ZPAL- Instituteof Paleobiology, Polish Academy of Sciences,Warsaw.

Description

Amphibia Linnó,1758 Salientia Laurenti, 1768 Family indet. Czatlrob atrachus gen. n. Type species: Czatkobatrachus polonicus sp. n. Derivation of name: From the type localiĘ of Czatkowice near Kraków, Poland, and Greek batrachos - a frog. Diagnosis.- As for thespecies. Range.- Early Triassicof Poland. Czatkobatrachuspolonicus sp. n. Derivation of name: From the counĘ of origin, Poland. HoloĘpe: ZPAL Ab.IV/7, a partial right ilium (Figs 1B' 2A). Other illustrated specimens: TAL Ab.fV/3 partial right humerus (Fig. fB, C); ZPAL Ab.IV/6 presacralvertebra (Frg. 3A); ZPALAb.MS (Fig. 3E) andZPALAb.tV/lO (Fig. 38) sacral vertebrae; ZPALAb.Ivll5 atlas centrum (Fig. 3Ę G); ZPAL Ab.rV/zO caudal vertebra (Fig. 3C, D); ZPA- LAb.MZ3 partial ulna (Fig. 2D). Other referred material: TAL Ab.M\ Ab.:NlIf, Ab.IV/13, partial right humeri; Ab.IV/4, Ab.IV/5, Ab.tv/g, Ab.IV/18, Ab.M19, Ab.IYlzI, partial left ilia; Ab.Iyll7, partial right ilium; Ab.IV/16, partial left ilium and fused ischium; Ab.Mll, Ab.\rll4, presacral vertebrae; Ab.Ivl22 caudalvertebra; ąnd furtherhumeral (4) and vertebral(11) specimens as yet uncatalogued. Diagnosi A small frog-like amphibian(about 50 mm snout-ventlengtĘ, showing the following combination of deńved character states:ilium with very prominent dorsal tuberosity;atlantal centrum single and without ńb facets, anteriorcotyles well spaced and slightly divergent;most or all presacral vertebraebearing long slender transverse processes; sacral rib robust, posterolaterally curved, fused to vertebral ACTA PALAEONTOLOGTCA POLONTCA (43) (4) 575

A

Fig. 1.A. Triadobatrachusmassinoti (Piveteau, t936),right ilium, MNHN, MAE 126.B. Czatl

Fig.2. Czatlrobatrachuspolonicil.s gen. et sp. n., isolated bones.A. Holotype ńght ilium, ZPALAb'IV/7, lateral view. B, C. Partial right humerus,ZPN- Ab.IV/3, in partial dorsal (B) and ventral (C) views. D. Ulna, TN, Ab.I\I/Ż3,side view of olecranonregion. All SEM micrographs;scale bars 0.5 mm.

Discussion

Attribution of the mateńal. - The Czatkowice material is dissociatedand attribu- tion of specimensto Czatkobatrachusis made on the basis of resemblanceto other primitive salientians and modem frogs. The atlas, humeri and ilia are distinctively salientianin their morphology.The post-atlantalvertebrae share a common structure (ectochordalcentra in which the dorso-lateralmargins bear a comma-shapedthicken- ing, relatively elongatedneural arches,no traceof neurocentralsufures, small size and delicatebuild) and clearly belong to a single genus.The form of the centrumis identical to that of the attributedatlas, and the vertebraeare compatable in size with the ilia and humeri. They also show a close generalresemblance to the vertebraeof Triadobatra- chus.The thin cylindrical ectochordalcentrum is quite differentfrom the more robustly built centrum of a small reptile (e.g., a notochordal lepidosauromorph),and quite different from that of small temnospondyls (to which the other amphibian material from the locality has been attributed). The vertebrae can therefore be referred to Czątkobatrąchuswith some confidence. In most presacraIvertebrae, the transverse processesare broken, but ZPAL Ab.IV/ 6 (Fig. 3,Ą) preservesa long narow process ACTA PALAEONTOLOGTCA POLONTCA (43) (4) 517

Fig. 3. Czatkobatrachuspolonicus gen. et sp. n., isolated bones. A. Presacral vertebra,ZPAL Ab.M6, antęńor view. B. Sacral vertebra,ZPAL Ab.IV/10, dorsal view. C, D. Caudal vertebra,ZPALAb.IV/20 in dorsal (C) and left lateral (D) views. E. Sacral vertebra,ZPN,Ab.IV/S, left lateralview. F, G. Atlas, ZPAL Ab.M5 in anterior(F) and antero-lateral(H) views.All SEM micrographs;scale bars 0.5 mm. culminating in a slightly expanded unicapitate tip which may have supported a small free rib such as that of living discoglossid frogs. The sacral transverse processes are very robust and are directed posterolaterally (Fig. 38, E). The general shape agarn resembles that of Triadobatrachus, except that the ribs are fused to the centrum. Finally, thęrę are two small vertebrae (ZPN- Ab.IV/2O and Ab.IVlfŻ,Fig.3C, D) which share thę common central morphology but arę much Smaller and lack either transverse processes or proper zygapophyses. They resemble the tiny caudal vertebrae of Triadobatrachus and suggest that Czatkobatrachus also retained a small tail. A single ulna with a fully ossified olecranon (Fig. 2D) is tentatively attributed to Czatkobatrachus since this is the only animal in the deposit known to have an ossified distal humeral condyle (Fig. 28, C), and the size and curvature of the olecranon provide 578 A steam-group frog: Evans & Borsuk-BiĄnicka

Notobatrachus Prosalirus& otherAnura

Caudata ś'9

Fig. 4. Diagram (basedon Baez & Basso 1996)showing hypothesized relationships of early salientianswith the addition of Czatkobatrachus and Prosalirus: I - Salientia, pelvis with anteriorly directed iliac blade; single distal humeral condyle; reduction of tail; 14 or fewer presacral vertebrae;2 - Unnamed node (Cz = Czatlabatrachus), elongate transverseprocesses on some or all presacrals,sacral rib fused to vertebral centrum; single atlantal centrum; no aflantal ribs; 3 - Unnamed node (V = Veraella). shortenedpresacral neural atches, loss of tail, fusion of radius+ulną tibia+fibu|a:4 - Unnamed node, 9 or fewer presacral vertebrae,coccyx present;hind limb substantiallylonger thanfore limb; 5 - Anura, well ossified spheneth- moid; no separatecaudal vertebrabetween sacrum and coccyx. a good match. If the attribution is correct then, as in Triadobatrachus, the ulna and radius remainedunfused.

Phylogenetic discussion. - Allowing for the limited charactersavailable, Czątkobą- trachuscanbefittedinto arecentlypublishedcladogramofearlyfrogs (Baez&Basso 1996)as a sistergroup of Veraella,Notobatrachus, ProsaliruJ, and othercrown-group anurans(Fig. 3' node Z).The developmentof the transversęprocesses may be a syna- pomorphy at the level of node 2, suggestinga reductionin rib size with a concomitant reduction in the iliocostąlis musculaturein favour of iliolumbaris and longissimus dorsi muscles. This in turn may signal the beginnings of an evolutionary shift away ACTA PALAEONTOLOGTCA POLOMCA (43\ (4) 579 from predominantlyundulatory movementsof the body towards a locomotor style in which dorso-ventralmovements had a more importantrole (Hinsche 1941;Emerson & De Jongh 1980;Emerson 1982).Czatkobatrachus thus appearsto documentan early post-Triadobatrachr,rstage in salientian evolution where the presacral vertebralcol- umn remained comparatively long (basędon the length of individual neural arches), a shorttail was retained,and the epipodials remainedseparate, but elongatetransverse processes and fused sacral ribs provided added presacral stability and improved transferof thrustfrom the hind limb. The presenceof near contemporaneoussalientian remains in both northernand southerncontinents provides confirmationof a pan-Pan- gean distribution of Salientia by the Early Triassic (Shubin & Jenkins 1995).This in turn supportsthe idea that the origins of the Salientia, and - by implication - of other lissamphibianlineages (salamanders,caecilians, albanerpetontids),must be soughtin the Permian, a view supportedby the molecular data (e.g.,Salthe & Kaplan 1966). Whether Lissamphibia is monophyletic (Milner 1988;Trueb & Cloutier l99l) or not (Caroll & Currie 1975), theremust have been a period of evolution and diversification in the Permian and Early Tńassic of which we currently have no knowledge. This highlights the paucity of the small freshwater/terresffialtetrapod record and the need to identify and prospectearly depositionalenvironments suitable for their preservation.

Acknowledgements

We thank Dr Mariusz Paszkowski (Kraków) for information on the Czatkowice deposits, and Dr J.-C. Rage @aris) for access to a high fidelity cast of Triadobatrachus.This work was supported under a BritisMPolish Joint Research Collaboration Programme funded by the British Council and the Polish State Committee for Scientific Research. Fig. 1 was prepared by AyshaRaza, Figs 2, 3 by Jane Pendjiky (University College, London) and Andrzej Baliński (Institute of Palaeobiology, Polish Academy of Sciences, Warsaw).

References

Bóez, A.M. & Basso, N. 1996. The earliest known frogs of the Jurassic of South Ameńca: review and cladistic appraisal of their relationships. - Milnchner geowissenschnftlicheAbhandlungen A 30, 131-158. Carroll, R.L. & Currie, P .l . 1975 . Microsaurs as possible apodanancestors. - Zoological Journal of the Linnean SocieĘ 57,2f9-f47 . Emerson, S.B. 1982. Frog postcranial morphology: identification of a functional complex. - Copeia3, 603-ó13. Emerson, S.B. & Jongh, H.J. De 1980.Muscle activity at the ilio-sacral articulationof frogs. - Joumal of M orp holo gy 166, I29-144. Evans, S.E., Milner, A.R., & Mussett, F. 1990.A discoglossid frog from the Middte Jurassic of England. - Geobios21.,539-55f. Hinsche, G.lg4lUntersuchungenzumfunktionellenAufbauderAnurenmitbesondererBeriicksichtigung der eoziinerGeiseltalfun de. - N ova Act a Le opoldina 7 l, 3 13-343. Milner, A.R. 1988.The relationshipsand origin of living amphibians.In: M.l. Benton (ed.),The Phylogeny and Classification of the Tetrapods. - The SystematicAssociation Special Volume 35A, 59-102. Clarendon Press, Oxford. Paszkowski, M. & Wieczorek, J.1982. Fossil karst with Mesozoic bone breccia in Czatkowice (Cracow Upland, Poland). - Kras i speleologia3,32-38. Rage, J.C. & Roćek, Z. |989. Redescription of Triadobatrachus massinoti (Piveteau, 1936) an anuran amphibian from the early Tńassic. - Palaeontographica A' 206, |_t6. 580 A steam-group frog: Evans & Borsuk-Białynicka

Salthe,S.N. & Kaplan,N.O. 1966.Immunologyandrates of enzymeevolutionintheAmphibiainrelation to the ońgins of ceńain taxa.- Evolutionzl,603416. Shubin, N.H. & Jenkins, F.A. Jr. 1995.An early Jurassicjumping frog. - Nature 377,49-52. Trueb, L. & Cloutier, R. 1991. A phylogenetic investigation of the inter- and intrarelationshipsof the Lissamphibia (Amphibia: Temnospondyli).In: HP. Schulze & L. Trueb (eds),ońgins of the Higher Groups ofTetrapods.Controversy and Consensus,223-313.ComstockPublishing Association,Ithaca.

lllczesnotriasowa pra -żaba z Polski sUsAN E. EvANs i MAGDALENA BoRSUK-BIAŁYNICKA

Streszczenie Czatkobatrachuspolonicus gen. et sp.n. jest drugimw świecie,po Triadobatrachusmassinoti (Piveteau,1936), triasowym przedstawicielem linii filogeneĘczne1płazow bezogonowych (Anura).Jest on równocześniepierwszym przedstawicielem tego odcinka filogenezy spoza Gondwany. Fragmenty szkieletu pozaczaszkowego zaliczone do Czatkobatrachus polonicus pochodząz brekcji kostnej wypełniającejstruktury krasowe rozwinięte w wapieniach karboń- skich w kamieniołomieCzatkowice koło Krakowa. Brekcja tatworzyłasię w permsko-wczes- notriasowej fazie krasowienia wapieni, a końcem tej fazy była transgresjaretu (Paszkowski & Wieczorek 1982). Zesp6ł'fauny, do którego należLyCzatkobatracłus (Borsuk-Biatynicka et aI. w opracowaniu),jest więc najprawdopodobniejwieku scytyjskiego (wczesny trias). Materiałkostny zaliczony do Czatkobatrachuspolonicus składasię z ok. 40 okazów. Wśród nich są liczne lecz niekompletnekości biodrowe (Fig. 2A)' kościramienne (Fig. 28' C) i kręgi' w tymkręgikrzyżowe(Fig. 3B, E),przedkłzyŻowe(Fig. 3A)' ogonowe(Fig. 3C' D)idźwigacz (Fig. 3F, G) oraz pojedynczy fragmentproksymalnego zakoilczeniakości łokciowej (Fig. 2D). Kościte zostĄ wybrane spośródsetek llźnych okazów uzyskanych drogą preparacji chemi. cznej i przemywania wielu kilogramów brekcji. Pruyna|eŻnośćokazów do jednego gatunku opiera się na połączeniuw nich cech zabich (budowa kościbiodrowych, ramiennych i dźwigacza,brak szwów mięfuy tukami a trzonami kręgów) z jednoliĘ budową i rozmiarami szcząków (trzony kręgów ektochordalneo podobnej długościi delikatnej budowie, r1żrltącesię od innych kregów tego zespołufaunistycznego) oraz podobieństwemwzględem rodzaju Triadobatrachus(np. rozmiary guzk.agrzbietowego Fig. 1). Grupa Salientia,doktóĘ rodzaj Czatkobatrachuszostał.zaltczony,obejmujepłazybezogo- nowe (Anura), znaneod jury i ich prymiĘwnych krewniaków,teptezentowanych dotądwyłą- cznie ptzez Tńadobatrachus z wczesnego triasu Madagaskaru. Jako drugi przedstawiciel triasowych Salientia Czatkobatrachusuzupełniawiadomościnatemattegobardzo słabopozna- nego etapu filogenezy, rzacając światłona proces ewolucyjny powstawania samych Anura. W kladogramie ilustĘącym stosunki pokrewieństwawczesnych Salientia (wg Baez & Basso 1996)lokuje się on jako pierwsza grupa zewnętrznaw stosunkudo Anura (Fig. a). Podstawą takiej lokalizacji jest wykształceniewyrostków poprzecznychkręgów przedkrzyiowych zwią- zane z redukcją żLeber(a zatem i ruchów bocznych kręgosłupa)lznane za synapomorfię Czatkobatrachusi Anura. Pod względem wykształceniastawu łokciowego Czatkobatrachus jest takżebardziej nowoczesny nźLTriadobatrachus,który lokuje sięjako dalszagrupa zewnę- trzna Tak skonstruowanykladogram wskazuje, ż'ewydłuiLenie kości biodrowej i redukcja ruchów bocznych kregosłupanastąpiła w linii płazow bezogonowych wcześniejniż zrosty podramieniai podudzia oraz powstanieurostylu. Stanowi to wskazanie dla przyszłychrekon- strukcji procesupowstawania żabiegosposobu lokomocji. Laurazyjskie połozeńe stanowiska z Czatkobatrachus potwierdza światowyzasięg prymi- tywnych Salientia w ffiasie (ekstapolowany wcześniejna podstawie rozmieszczeriajurajskich żab),implihją" równocześniedtug4, moŻepermską, wcześniejszą historię tej linii płazów.