Revised Taxonomy of Amphibians Albanerpetontid

Revised taxonomy of albanerpetontid amphibians

JAMES D. GARDNER

Gardner, J.D. 2000. Revised taxonomy of albanerpetontid amphibians. - Acta palaeon- tologica Polonica 45, 1,55--70.

Characters of thejaws and frontals are often used to differentiate albanerpetontid genera and species, yet the reliability ofthese characters has rarely been examined. Frontals are diagnostic for the genefaAlbanerpeton and Celtedens and for species in the latter genus. The value of frontals at the specific level in ce ltedens may be inflated by lack of information about variation injaw structure. characters of the frontals, jaws, and body size differentiate speciesof Albanerpeton. Differential diagnoses are presented for the Albaner- petontidae based on cranial and vertebral characters and for the two named genera based on frontal characters. Each genus is characterized by one autapomorphy: fused frontals triangular inAlbanerpeton and internasal process bulbous in celtedens. An enigmatic albanerpetontid from the Middle Jurassic (upper Bathonian) of England has a unique mixture of frontal and premaxillary character states that precludes it from being included in either Celtedens or Albanerpeton.Thisleaves the oldest occurrences of the two genera in, respectively, the Late Jurassic (Kimmeridgian) and Early cretaceous (latest Aptian/ earliest Albian).

Key words: Albanerpeton, Albanerpetontidae, Allocaudata, Amphibia, Celtedens, Lissamphibia, taxonomy.

James D. Gardner [[email protected]], Laboratory for vertebrate paleontology and Deparxnent ofBiological sciences, university ofAlberta, Edmonton, AtbertaT6G 289 Canada.

Introduction

The AlbanerpetontidaeFox & Naylor, 1982 ne salamander-like,Middle Jurassicto Miocene amphibians that are of general interest becausethey constitute a clade of lissamphibiansdistinct from caudates,salientians, and gymnophionans.Two genera, containing at least nine species,are currently recognized:the type genusAlbanerpeton Estes& Hoffstetter,I9T6,from the Lower Cretaceous-Paleoceneof the Norttr American westernInterior andMiocene of France@stes & Hoffstetter1976; Estes 19g1; Fox & Naylor 1982;Gardner r999a, b, c) and celtedensMcGowan & Evans.1995 from the 56 Revised taxonomy of albanerpetontid amphibians; GARDNER

Lower Cretaceous,Upper Jurassic,and, purportedly, Middle Jurassicof Europe (I\4cGowan& Evans1995; McGowan1996,1998; McGowan & Ensom1997). Jaws and frontals are the most commonly recoveredalbanerpetontid elements at most sites,and charactersof theseelements are widely usedto diagnosegenera and species(Estes 1981; Nessov 1981; Fox & Naylor 1982;McGowan & Evans 1995; McGowan 1998;Gardner l999a,b, c; Rage& Hossiniin press).In many cases,the reliability of such charactershas not been adequatelyestablished. This is the result of a combinationof factors:scarcity of well preservedspecimens; a reluctanceon the part of someworkers to examineappropriate comparative collections; and misinterpreta- tionsof structure.To cite a recentexample, McGowan (1998) used only frontal characters to diagnoseAlbanerpeton, Celtedens, and their respectivespecies. McGowan's (1993)claims aboutthe diagnosticutility of frontals for Albanerpetonand its species are suspectbecause he consideredjusttwo ofthe four namedspecies then includedin the genus(I recognizeseven species), examined only material of the type speciesA. inexpectatumEstes& Hoffstetter,1976, andmisinterpretedthe structureof the frontal inA. galaktionFox & Naylor, 1982based on photographs(Fox & Naylor I982:fig.ld, e) of an incompletespecimen. McGowan's (1998)reliance on frontal charactersalone to diagnosespecies of Albanerpetonis alsoat oddswith observationsthat charactersof the jaws are also useful for this purpose(Estes 1981; Fox & Naylor 1982; Gardner I999a,b, c; Rage& Hossiniin press). Here I assessthe taxonomicvalue of charactersfor albanerpetontids,with empha- sis on frontals and jaws. Isolated examplesof theseare availablefor all speciesof Albanerpeton(Estes & Hoffstetter1976;Fox & Naylor 1982;Gardnet I999a,b, lun- published data), except for a new Turonian speciesknown only by its distinctive holotype premaxilla (Gardner I999c). Frontals are also reasonablywell known for Celtedens,bothas disassociatedelements from indeterminatespecies and articulated in the respectiveholotype skeletonsof both namedspecies, C. megacephalus(Costa, 1864)and C. ibericusMcGowan & Evans,1995 (McGowan & Evans1995; McGo- wan 1996,1998;McGowan & Ensom 1997).Jaws in theseskeletons are difficult to studybecause they arepreserved in articulationand, in the caseof the holotypeof C. megacephallzs,also poorly preserved.The only isolated,reasonably well preserved jaws availablefor Celtedensare incomplete premaxillae and dentaries of an indeterminate speciesfrom the Lower Cretaceousof Purbeck,England (McGowan & Ensom 1997).In the secondpart of this paper,I provide reviseddiagnoses and selectcom- ments for the Albanerpetontidae and its genera,then examine the identity of a pur- portedCeltedens-llke taxon (McGowan 1996,1998)from the Middle Jurassicof Eng- land. Osteologicalterms and measurements follow Gardner(1999a), with oneexception. 'lacrimal For the premaxilla, I proposethe replacementterm notch' for the indentation alongthe laterodorsaledge ofthe parsdorsalis - this notchreceived the largelacrimal, not the reducedprefrontal (Gardner in press).I follow McGowan & Evans (1995) in placingalbanerpetontids within the LissamphibiaHaeckel, 1866 and Milner (1988)in regardinglissamphibians as crown-cladetemnospondyls. Institutional abbreviations: BMNH, Natural History Museum, London, England; DORCM, Dorset County Museum, Dorchester,England; FMNH, Field Museum of NaturalHistory, Chicago, USA; LH, Las Hoyascollection, Museo de Cuenca,Cuenca, ACTA PALAEONTOLOGICAPOLONICA (45) (I) 57

Spain; MNHN.LGA, La Grive-St. Alban collection, Mus6um National d'Histoire Naturelle,Paris, France; MNP, Museodi Paleontologiadell'Universitd di Napoli, Na- ples, Italy; RTMP, Royal Tyrrell Museum of Palaeontology,Drumheller, Canada; UALVP, University of Alberta Laboratory for Vertebrate Paleontology, Edmonton, Canada;UCK, University CollegeLondon, London, England; and UCMP, University of California Museumof Paleontology,Berkeley, USA.

Taxonomic characters for albanerpetontids

Frontals (Figs 1, 2;Table 1). - Albanerpetontidfrontals are solidly fusedmedially and have a prominent internasalprocess, two pairs of slots anterior to the orbital margin for mortise and tenon style articulation with posterior endsof the paired nasalsand prefrontals, prominent ventrolateral crests adjacent to the orbital margin, and dorsal omamentcomprised of polygonal pits enclosedby ridges. Comparisonswith other temnospondylsindicate that the frst three of thesecharacter states are synapomorphic for the family (Gardnerunpublished data).

Table 1. Frontal characters for albanerpetontid genera and species. References are: lMcGowan & Ev- ans1995;2McGowan 1998;3Gardnerl999a;aRage &Hossiniinpress;5S.E. Evans personalcommu- nication 1999.

l. Dorsal or ventral outline of frontalsl,2'3. 2. Midline length of frontals relative to width across posterior edge between lateral edges of ventrolateralcrests2'3'4. 3. Dorsal or ventral outline of internasal processl,2'3. 4. Length of internasal processrelative to width acrossbase2. 5. Pattem of contact between internasal process and paired nasals3. 6. Form of anterolateral processs. 7. Medial emargination of posterior slot for receipt of prefrontal2. 8. Width of frontals between slots for receipt ofprefrontal relative to width across posterior edge of bone2. 9. Angle at which lateral wall of frontal diverges posterolaterally from midline2. 10. Position of anterior limit of orbital margin relative to midline length of frontals2. 11. Dorsal or ventral outline of orbital marginl'2. | 2. Form of ventrolateral crests. 13. Pattern of dorsal omament2.

Table 1 lists the 13 frontal charactersthat have been used to differentiateAlbaner- peton,Celtedens, and their respectivespecies. Seven characters (1-3, 6,'7,10, and 11) differ betweenAlbanerpeton and Celtedens, as follows (Figs | , 2): l, outlineof frontals triangularin Albanerpelo/z,versus more nearlyhourglass- or bell-shapedin Celtedens; 2, midline length of frontals relative to width acrossposterior edge between lateral edges of ventrolateralcrests less than about l.2inAlbanerpeton, versus more than about 1.2 in Celtedens;3,outline of intemasalprocess triangular inAlbanerpeton,versus bulbous in Celtedens;6,anterolateral process distinct from main body offrontal, extendingantero- laterally, and pointed distally tn Albanerpelor2,versus a poorly differentiated,broadly rounded shoulder in Celtedens;7, dorsal and ventral edges of slot for receipt of prefrontal excavated medially in Albanerpeton, yetslrs unexcavated tn Celtedens; 58 Revised taxonomy of albanerpetontid amphibiarcs.'GARDNER

10, anterior end of orbital margin, as marked by posterior edge of slot for receipt of prefrontal, lies approximatelyin line with, or posterior to, anteroposteriormidpoint of frontals inAlbanerpeton, vetsusanterior end of orbital margin lies anterior to midpoint of frontals in Celtedens;and 11, outline of orbital margin uniformly shallowly curvedto nearly straight in Albanerpelonoversus margin more concavemedially and, occasionally, deflectedposterolaterally near posterior end in Celtedens.Where known, the pattern of frontal-nasalcontact (character5) also differs betweenthe two genera.Ventral facetson the internasalprocess of an incompletefrontal (Fig. 2A) of Celtedenssp. from Purbeck indicate that the lateral edgesof the processdorsally overlappedthe medial edges of the paired nasals. This differs from the condition in Albanerpeton, where a groove extendingalong the lateral face of the intemasalprocess (Fig. 1G) held the medial edge of the nasal in a tongue-in-groovejoint. Outgroup comparisonswith other temnospondylsargue for the triangular-shapedfrontals of Albanerpeton and the bulbous-shapedinternasal process in Celtedensbeingthe derived statesfor characten I and 3, respectively.Polarities for statesofthe other frontal charactersare uncertain. Outlinesof the frontals (character1) also differ within genera.Among speciesof Albanerpeton,the outline approximatesthat of an equilateraltriangle in A. inexpectatum andan anteroposteriorlyelongate, isosceles triangle in othercongeners (cf. Fig. 1A versusB*F). This variationis associatedwith differencesboth in the relativelength of the frontals (character2: rutio of midline length to width acrossposterior edge of bone about0.9-1.0 in A. inexpectatum,versus closer to about1,2 in other congeners) andin the angleat which the lateralwall of the frontalsdiverges posterolaterally from the midline (character9: about 30' in A. inexpectatum,versus about 15-25' in other congeners).As these charactersvary consistentlyamong speciesof Albanerpeton, I seeno point in using all threeto differentiatecongeners. I favor usingproportions of the frontals (character1), becausethese values can be measuredor estimatedfrom specimensand reported in a relatively unambiguousmanner. Judging by McGowan's figures (1998: fig. 1C-F, H), frontal outlines in Celtedensrange from hourglass- -shaped,as in C. ibericusand specimensfrom Purbeck,to more neaily bell-shaped,as in C. megacephalusand specimens from Ufra (cf. here:Fig.2A, B versusC, D). Fron- tals from an indeterminatecongener at Guimarota (Fig. 2E) areintermediate between thesetwo extremes.Differences in frontal outlines within Celtedensare associated with variationin characters8 and 11.In hourglass-shapedfrontals, the width between the slotsfor receiptof the prefrontalsis approximatelytwo-thirds the width acrossthe posterioredge of the frontals (McGowan 1998: table 1). The orbital margin is uniformly concavemedially in C. ibericus; this is also the generalpattern in the taxon from Purbeck,except that the posteriormostpart of the margin is essentiallystraight anddeflected lateroposteriorly. In bell-shapedfrontals, the boneis markedlynilruower anteriorly,with the width betweenthe slotsfor receiptof the prefrontalsabout one-half the width acrossthe posterioredge of the frontals (McGowan 1998:table 1), and the orbital marginsare more or lessparallel to a point aboutone-half to two-thirds of the distancefrom the anteriorend of the bone,before curving more lateroposteriorly.No other frontal charactersappear diagnostic for speciesof Celtedens. Afinalthreefrontalcharacters(3,4,and12)differsignificantlywithinAlbanerpeton. Characters3 and4 describe,respectively, the outline and proportions of the internasal process.Among speciesof Albanerpeton, thesetwo charactersare essentiallyidentical: ACTA PALAEONTOLOGTCAPOLONTCA (45) (1) 59

anterolateral process*r\ posteriorslot

i- orbital margrn

.AB^

ventrolateral CTESI

G groove

Fig. 1. Azygous frontals of Albanerpeton.A. Albanerpetoninexpectatun, MNHN.LGA 1222, complete frontals,ventral view; middle or ?lowerMiocene fissure fill, La Grive-St.Alban, France.B. Albanerpeton nexuosus,reconstructed frontals basedon UALVP 39983,39986,39989, and39996, ventral view; Milk River Formation(lower Campanian),Alberta, Canada.C. Unnamedlate Paleocenespecies, UALVP un- numbered,incomplete frontals with internasal processwarped to the right (left side in figure) and missing much of anterolateral process on right side, all of anterolateral process on left side, and posterior end of bone,ventral view; PaskapooFomation (upperPaleocene), Alberta, Canada.D. Albanerpetonarthridion, FMNH PR2026,nearly completefrontals missing distal end of both anterolateralprocesses, ventral view; Antlers Formation (uppermost Aptian-middle Albian), Texas and Oklahoma, USA. E. Albanerpeton galaktion,reconsffucted frontals based on UALVP 16216,39946,39949,and 39951, ventral view; Milk River Formation (lower Campanian),Alberta, Canada.F. Unnamedmiddle Campanianspecies, recon- structedfrontals basedon RTMP 86.194.8,95.181.67, 96.1.57, and 96.78.135,ventral view; Dinosaur Park and Oldman formations (middle Campanian),Alberta, Canada.G. Albanerpeton inexpectatum, MNHN.LGA 1220, complete frontals, right lateral view, showing more posterior slot for receipt of prefrontaland groove for contactwith medialedge ofnasal. Broken surfaces are white. Scalebars = 1 mm. the process is either acuminate and relatively naffow or acute and relatively broad (cf. Fig. 1A-C versusD-F). As an aside,I shouldpoint out that McGowan & Evans' (1995:fig. 3b) andMcGowan's (1998: fig. 1b)figures of fusedfrontals of A. galaktion incorrectlydepict the internasalprocess as brcad, short,and wedge-shaped.These au- thors' drawingswerc based on publishedphotographs @ox & Naylor 1982:fig. ld, e) of 60 Revised tilconomy of albanerpetontid. amphibians: GARDNER

rl rl t1 ,' 1l lr rl 1l I .,I

Fig.2. Azygotrsfrontals of Celtedens,all in ventralview. A. Celtedenssp. indet.,DORCM GS35,incomplete frontals, with arrow indicating anterior end of orbital margin, cross-hatchingshowing areaonce pres- ent but now missing (seeMcGowan & Ensom 1991:frg.2a), and hashmarks indicatingmatrix; Purbeck (Berriasian), England. B. Celtedensibericus, outline drawing of frontals articulated in holotype skull LH 6020; Las Hoyas (upper Barremian), Spain. C. Celtedensmegacephalus, outline drawing of frontals articu- latedinholotype skullMNP542; Pietraroia(lowerAlbian),Italy.D. Celtedenssp. indet., catalogue number unreported,outline drawing of frontals; Ufla (Banemian), Spain. E. Celtedenssp. tndet., cataloguenumber unreported, outline drawing of frontals; Guimarota (Kimmeridgian), Portugal. Frontals in figures B-E redrawn from McGowan (1998:fig. l). Scalebars = 1 mm: left scalebar is for figure A, right scalebar is for figuresB and C; scalesfor specimensin figuresD and E were not reportedby McGowan (1998). a referred frontal (UALVP 16216)that is broken anterior$ and lacks the internasalpro- cessentirely. The surfacethat McGowan& Evans(1995) and McGowan (1998)inter- preted as the outtne of the internasalprocess is actually the broken anterior end of the specimen.Other referredfrontals in the collection of the UALVP show the proper form of the processforA. galahion; this information is incorporatedinto my reconstructionin Fig.2E. Character12 describesthe transverseprofile and relative width of the ventrolateral crest. In fransverseprofile, the crest is either convex ventrally or resembles a right-angled triangle, with the medial edge deep and the lateral edge shallow' The width of the crestimmediately behind the slot for receiptof the prefrontal,in large specimens,is either lessthan about0.40 or greaterthan about0.45 the width acrossthe poste- ACTA PALAEONTOLOGICAPOLOMCA (45) (1) 6l rior edgeof the frontals betweenthe medial edgesof the crest.Frontals from large indi- vidualsof A. inexpectatumandA. arthridion Fox & Naylor, 1982exhibit the most ex- treme differencesin the form of the ventrolateralcrest (cf. Fig. 2A versusD). Emargination of the slot for receipt of the prefrontal, relative length of the orbital margin, and pattern of dorsal ornament(characters 7, 10, and 13, respectively)are less variableamong species of AlbanerpetonthanMcGowan(1998) suspected. McGowan's (1998)beliefthat relativeorbital lengthsare diagnosticfor speciesis, again,based on his misinterpretationof a figured frontal (UALVP 16216) of.A. galaktion.The specimen is broken anteriorly, creating the impressionthat the anterior limit of the orbit lies more anterior. Emargination of the slot for receipt of the prefrontal and dorsal ornament both becomemore pronouncedwith grcwth in speciesof Albanerpeton;this is especiallyevident in A. inexpectatum(Gasdnet I999a). Albanerpetontidfrontals are typically omamenteddorsally with a systemof polygonalpits enclosedby ridges.Oc- casionalfrontals are encountered in which the pits areso shallowand the ridgesso low that the dorsal surfaceis virtually smooth. As this condition occurs in different-sized and,sometimes, well preservedfrontals of speciesin both genera,it appearsto be neither ontogeneticor diageneticin origin nor taxonomicallysignificant. In short,ofthe 13 frontal charactersconsidered, characters I-3,6,7, 10, 11, and, probably, 5 are taxonomically important at the generic level for albanerpetontids, whereasat the specific level characters14,9, and 12 are informative for Albaner- peton andcharacters 1, 8, and 11 areinformative for Celtedens. Jaws (Fig. 3). - Albanerpetontidjaws aredistinctive, but superficiallyresemble and havebeen confused with jaws of otherlissamphibians and lizards.For this reasonand becausealbanerpetontid jaws are not uncommonin nonmarineJurassic and Creta- ceousmicrovertebrate assemblages, abrief review of their characteristicfeatures is ap- propriate.For attachmentof the highly pleurodontteeth, the premaxilla and maxilla eachhave a deeppars dentalis and the dentaryhas a tall dentalparapet. Upperjaws are additionally chnacteized by having tiny, scatteredexternal nutritive foramina labially, the tooth row extending along virtually the entire ventral margin of the pars dentalis,and a prominent,shelf-like parspalatinum lingually. The parspalatinum on the premaxilla is pierced by a palatal foramen and on the maxilla bears a trough dorsolinguallyfor contactwith one or more palatalbones. The premaxilla is further distinctivein having afaceLon the labial face for contactwith a complementarypro- cessfrom the maxilla. The pars dorsalison the premaxilla is prominent,often with a dorsal boss labially and a lacrimal notch laterodorsally.The lingual face of the premaxillarypars dorsalis is excavatedby the suprapalatalpit,a cavity that typically is boundedon eitheror both sidesby a vertical strut.The maxilla is further characteized by having a low, posteriorly taperedpars facialis that dorsally bears a triangular- -shapedinternasal process. Anteriorly the maxilla bearsan elongatepremaxillary lateral processand a lingually broad, shelflike premaxillary dorsal process,both of which articulatewith the premaxilla.Additional diagnosticfeatures of the dentaryin- clude a row of externalnutritive foraminalabially along aboutthe anteriorone-half to two-thirds of the bone, an elongatescar ventrally for attachmentof the intermandi- bularis muscle,and a foramenin the baseof a pit on the undersideof the symphysis. Lingually, the Meckeliancanal is closedanteriorly, the subdentalshelf is low, narrow, and gutter-like anteriorly, becoming deeper and narrower posteriorly, and there is 62 Revised taxonomy of albanerpetontid amphibians: GARDNER

Fig. 3. Jawsof albanerpetontids.A,. Celtedenssp. indet., DORCM GS34,incomplete left premaxillalack- ing most of parspalatinum and dorsalpart of pars dorsalis,lingual view. B. Albanerpetonarthridion, rc- consfucted right premaxilla basedon FMNH PR805 (holotype) and FMNH PR2O23,lingualview. C. Albanerpetongalaktion, reconstructedleft premaxilla basedon UALVP 16203 (holotype),16204, and l62l2,llrngrualview.D,E. Albanerpetonnexuosus, premaxillae: D, reconstructedfused premaxillae based on UALVP 16206 and 39955, lingual view; E, UALVP 39960,teft premaxilla,occlusal view.B. Alba- nerpeton galaktion, UALVP 16212, left premaxilla, occlusal view. G-I. Albanerpeton inexpectatum, MNHN.LGA 1232, Ieft maxilla, labial, lingual, and dorsal views. J. Albanerpetonnexuosus, UALVP 16242, incomplete right maxilla missing about posterior one-third of bone and crowns of anteriormost teeth, with outline of anterolateral premaxillary process (dotted line) from UALVP 16239, labial view. K. Albanerpetongalaktion, UALVP 16240,incomplete right maxilla missingabout posterior one-thfud of boneand crowns of anteriormostteeth, labial view.L-O. Albanerpetoninexpectatum, MNHN.LGA 1249, nearly complete right dentary missing posteriormost end, labial, lingual, occlusal, and ventral views. P. Albanerpetonnexuosus,UCMP 49547 (holotype), nearly completeleft dentarymissing posterior end. Provenancesfor listed specimens:Celtedens sp. (A), Purbeck(Berriasian), England; A. arthridion (B), AntlersFormation(lower-middleAlbian),Texas,USA;A.galaktion(C,F,andK)andUALVPspecimens (D, E, andD of A. nexuosus,Milk River Formation(lower Campanian),Alberta, Canada;holotype (P) of A. nexuosus,Lance Formation (upper Maastrichtian),Wyoming, USA; and A. inexpectatum(G-I and -> ACTA PALAEONTOLOCTCAPOLONTCA (45) (r) 63 a broad areaof attachmentposteriorly for postdentarybones. One or two prominent symphysealprongs project medially from the more posteriorpart of the symphysis. Thesearticulate in a mortise and tenonfashion with complementaryprongs from the opposite dentary to form a unique interlocking intermandibularjoint (see Fox & Naylor 1982: fig.4b-d). Symphysealprongs are unique among gnathostomesto albanerpetontidsand areunquestionably autapomorphic for the family (Milner 1988; Gardner unpublished data). The arrangement,attachment, and structure of the marginal teethare also characteristic. Teeth are highly pleurodontin attachment- i.e.,they are attachedalong most of the height of the pedicleto the inner wall of thejaw. Each tooth is relatively elongate,straight, and non-pedicellate.The baseof eachtooth is rarely perforatedby a foramenand the pedicle is slightly compressedmesiodistally. The crown is chisel-like, labiolingually compressed,and bears three faint, mesiodistally aligned cuspules.Such crowns are autapomorphicfor the family, at least amongother temnospondyls,whereas non-pedicely is convergentwith vmious other lissamphibiantaxa (Gardnerunpublished data). Jawsare too poorly known for Celtedensto determineif theseelements dffier at the genericlevel for albanerpetontidsor amongspecies of Celtedens.I suspectthat befter jaw materialwould demonstrateat leastspecies level differences,comparable to those documentedbelow for Albanerpeton.Where known, jaws of Celtedenshave a general- ized albanerpetontidconstruction. Premaxillae of the indeterminatespecies from Purbeckprimitively resemblethose of A. arthridion in having a tiny suprapalatalpit locatedhigh on the lingual face of the pars dorsalis,well abovethe pars palatinum (Gardner1999b; here:cf. Fig. 3,{versusB). Charactersof the upper and lower jaws differ within Albanerpeton and have been usedto diagnosespecies @stes 1981; Fox & Naylor 1982;Gardner 1999a, b, c; Rage& Hossini in press).Variation is particularly extensivein the structureand contactsof the premaxilla (Fig. 3B-F), making this the most taxonomically useful element.I consider the following premaxillarycharacters useful for diagnosingspecies: build of bone(e.g., gracile versusrobust); premaxillaepaired or fused; proportions of pars dorsalis;pattern of contactdorsally with nasal;presence and relative size of dorsalboss; extent and pattem of labial omament;position, shape,and relative size of suprapalatalpit; numberand form of internal struts; form of palatine processand of dorsal rim on lingual edge of maxillary process;and relative size of palatal foramen.Premaxillary charactersnot useful for this purpose(contra Estes 1981; Fox & Naylor 1982;Rage & Hossiniin press)in- clude the proportionsof the lacrimal notch, length of the medial flange, and relative de- velopmentof the pars palatinum (Gardner I999b). Although I have not recognizedany diagnosticpremaxillary charactersfor Albanerpeton, subgenericclades are identified by suitesof premaxillary synapomorphies(Gardner I999b, c). For example,in all species of Albanerpeton exceptA. arthridion the suprapalatalpit is relatively larger and lies lower on the parsdorsalis (cf. Fig. 38 versusC, D).

L-O), middle and ?lowerMiocene fissurefills, La Grive-St.Alban, France.Specimens in B-D redrawn from Gardner(1999c:. frg.2), L-0 redrawnfrom Gardner& Averianov(1998: fig. 2), andP redrawnfrom Estes (1964: fig. 44c). Arrow 1 (A-D) points to suprapalatalpit and arrow 2 (E G) points to palatal foramen, both in premaxilla. Broken surfacesare white. Scalebars = 1 mm: specimensin A and B have separate scalebars; bottom centerscale bar is for other specimens. 64 Revised taxonomy of albanerpetontid amphibians: GARDNER

I attachconsiderable importance to the suprapalatalpit (Fig. 3A-D: arrow 1). Fox & Naylor's (1982)suggestion that the suprapalatalpit held a glandis reasonable,con- sidering the position of the pit in the lingual face of the premaxillary pars dorsalis and its associatedforamina. Although the identity of sucha gland is unknown,it presum- ably functionedin olfaction,feeding, or both. The suprapalatalpit is intimately associatedwith the palatalforamen (Fig. 3E, F: arrow 2), atypicaTlysmall foramenthat extends dorsally through the pars palatinum to open beneath, or in the floor of, the suprapalatalpit, regardlessof the position of the pit mediolaterallyacross the pars dorsalis. Assuming that the suprapalatalpit held a gland, the palatal foramen likely carried a duct betweenthe gland and the roof of the mouth. Differencesin the size, shape,and position of the suprapalatalpit arepronounced among species of Albaner- peton, and it is tempting to speculatethat thesemodifications were reflected in life by variation in the form and function of the presumedgland. Neither the maxilla nor dentary, where adequately known, are diagnostic for Albanerpetonor Celtedens.None of the dentary charactersthat Nessov (1981) be- lieved weretaxonomically useful at the genericlevel for albanerpetontidsseem appro- priate for this purpose(Gardner & Averianov 1998).Taxonomically useful variation is, however,evident at the specificlevelinAlbanerpetonin the following (Fig. 3G-P): proportionsand outline of the premaxillarylateral process on the maxilla; presenceof a dorsalprocess immediately behind the tooth row on the dentary;presence of labial ornamenton bothjaws in largeindividuals; and labial outline of the ventraledge of the pars dentalis on the maxilla and of the dorsal edgeof the dental parapeton the dentary. The last characteris linked with sizeheterodonty of the teeth(see below). Two tooth charactersdiffer among speciesof Albanerpeton.Teeth located about one-third of the distanceposteriorly along the tooth row on the maxilla and dentary are usually only slightly longer than the more anterior and posterior teeth, but in A. nexuosusEstes, 1981 (Fig. 3J, P) teeth aboutone-third of the distancealong the row arerelatively longer and,occasionally, more robustthan adjacentteeth. Although not evidentin Fig. 3, the positionof the anteriorend of maxillary toothrow alsovaries: the anteriorend of the tooth row is approximatelyin line with the leadingedge of the nasal processinA. inexpectatumand two new North American species(middle Campanian and Paleocene),but extends several loci more anteriorward in other congeners. Spacingof teethand crown structuredo not vary reliably amongspecies of Albaner- peton,butundescribed jaws from Europeand North Africa suggestthat this may not be true for someother albanerpetontidtaxa. Other characters and elements.- The only other characterthat I haveidentified as being taxonomically important within the Albanerpetontidaeis maximum head-body length (i.e.,length of headplus body). This straightlinevalue can be measuredor estimated directly from skeletonsor calculated from the midline length of frontals (Gardner I999b). Head-body length is informative at the specieslevel in Albaner- peton,where estimated maximum values range from about30 to over 60 mm, depend- ing on the species(Gardner I999b). This value doesnot appearto vary significantly amongspecies of Celtedens.The anteriormostthree vertebrae in albanerpetontidsare highly modified in a uniquemanner (see familial diagnosis,below). Too few examples of theseand more posterior vertebraeare available to determineif vertebral structure variessignificantly among genera and species. ACTA PALAEONTOLOGICAPOLONICA (45) (I) 65

Systematic paleontology

SubclassLissamphibia Haeckel, 1866 Order AllocaudataFox & Naylor, 1982 Family AlbanerpetontidaeFox & Naylor, L982 Reviseddiagnosis. - Cladeof lissamphibiansdiffering from all other vertebratesin the following two autapomorphies:mortise and tenon style intermandibularjoint and first threevertebrae comprised ofan atlaslacking postzygapophyses and having posterior cotyle with articular face indented by tripartite facets and dorsal and ventrolateral 'axis' marginsdeeply emarginate,a neomorphic lacking neural arch and transverse processes,and first trunk vertebralackingprezygapophyses, but havinganterior end of neural arch extending craniad above axis to fit into complementarynotch in posterior edge of atlantal neural arch. Differs from other temnospondylsin five synapomorphies:crowns on marginalteeth labiolingually compressed and distally bearthree faint cuspulesarranged mesiodistally; joint betweenskull and mandiblenemly vertical; and frontals fused, with prominentinternasal process and two pairs of slots for mortise and tenon contact with paired nasalsanteriorly and paired prefrontals antero- laterally. Differs further from some amphibamids and most lissamphibians in one homoplasy:marginal teeth non-pedicellate in adults.Among lissamphibians,lacksre- spectiveautapomorphies of gymnophionans,caudates, and salientians;more derived than gymnophionansand resemblescaudates and batrachiansin lacking surangular, splenials,and coronoids,but differs from last two groupsin primitively retaining a posteriorly closed maxillary arcade,concave articular receiving convex quadrate, more than20 presacralvertebrae, ossified pubis, and dermal scales. Primitively differs further from apodans,anurans, and many urodeles in retaining lacrimal and from apodans,salientians, and someurodeles in retainingodontoid process. Remarks. - The abovediagnosis is derivedfrom my unpublishedphylogenetic anal- ysis ofthe relationshipsof albanerpetontids.This is the first diagnosisfor the cladethat is differentialand explicitly identifiespolarities of characterstates (cf. Fox & Naylor 1982;McGowan1998). Two otheralbanerpetontid genera have been named. The two speciesof Nukusurus Nessov,1981 (Cenomanian and Coniacian, Uzbekistan) are each named on a dentary, neitherof which is diagnosticbelow the familial level. Hence,the namesNukuswrus, N. insuetusNessov, 1981, and N. sodalisNessov, 1997 ne nomina dubia within the Albanerpetontidae(Gardner & Averianov 1998). The name Bisharq Nessov, 1997 (Santonianor Campanian,Kazakhstan) denotes an indeterminate caudate taxon, not an albanerpetontid,because the holotypeof the type and only species,B. backqNessov, 1997,is an atlantalcentrum from an indeterminatesalamander (Gardner & Averianov 1998).The first Gondwananalbanerpetontids were recently reportedby Sigogneau- -Russellet al. (1998)from the basalCretaceous (Berriasian) of Morocco. Albanerpeto n Estes & Hoffstetter, 1976 Figs1,3B-P. Type species:Albanerpeton inexpectatumEstes & Hoffstetteq 1976, niuddleand ?lower Miocene, France. 66 Revised taxonorny of albanerpetontid amphibians; GARDNER

Other species: A. arthridion Fox & Naylor, 1982, uppennost Aptian/lowermost Albian-middle Albian, Texas and Oklahoma, USA; A. galaktion Fox & Naylor, 1982 and A. nexuosus Estes, 1981, both Campanian and Maastrichtian, North American Westem lnterior; and thrce unnamed species,oneeachfromtheupperTuronianof Utah, USA, middle Campanianof the NorthAmeri- can Western lnterior, and upper Paleocene of Alberta, Canada. Distribution. - UppermostAptian/lowermost Albian-upper Paleocene,North Ameri- canWestern Interior; and middle and ?lowerMiocene, France. Diagnosis (revised from McGowan 1998; Gardner 1999a).- Genus of albanerpetontid differing fromCeltedens in having fused frontals more derived in being triangular-shapedin outline and more primitive in retaining anteriorly pointed internasal process.Differs further from Celtedensin anothersix frontal characterstates of uncertain polarities: ratio of midline length to width acrossposterior edge between lateral edgesof ventrolateralcrests about 1.2 or less; lateral face of internasalprocess in- dentedby anteroposteriorlyelongate groove for tongue-in-groovecontact with medial edgeofnasal; anterolateralprocess prominent and pointed distally; dorsaland ventral edgesof slot for receipt of prefrontal excavatedmedially; anterior end of orbital margin located approximately in line with, or posterior to, anteroposteriormidpoint of frontals; and orbital margin uniformly shallowly concaveto nearly straight along entire length in dorsal or ventral outline. Remarks. - I recently presentedrevised diagnoses and redescriptronsfor Albaner- peton inexpectatum(Gardner 1999a) andA. arthridion (Gndner 1999b).The new late Turonian speciesis namedin a forthcoming paper (GardnerI999c). Descriptionsof the unnamedmiddle Campanianand late Paleocenespecies and redescriptionsof A. nexuosusandA. galaktion areinpreparation.I (Gardner1999c: fig. 2) alsopresented a simplified versionof my hypothesisof relationshipswithin the genus.A. arthridion is the basalmostspecies and the sister to a less inclusive clade comprisedof two sister-clades:the so-calledgracile-snouted clade of A. galaktion andthe late Turonian andmiddle Campanianspecies and the so-calledrobust-snouted clade of A. nexuosus, A. inexpectatum,andthe late Paleocene species. Details of this phylogenywill be published elsewhere. CeltedensMcGowan & Evans.1995 Figs2, 3,A.. Typespecies: Celtedens megacephalus (Costa, 1864), lower Albian, Italy. Otherspecies: C. ibericus McGowan & Evans,1995, upper Barremian, Spain. Distribution. - Kimmeridgian (seeRemarks below)-lower Albian, Europe. Diagnosis(revised from McGowan 1998).- Genusof albanerpetontiddiffering from Albanerpetoninhaving fusedfrontals more derivedin bearingbulbous-shaped internasalprocess and more primitive in retaininghourglass- or bell-shapedoutline. Differs further fromAlbanerpeton in anothersix frontal characterstates ofuncertain polarities: ratio of midline length to width acrossposterior edge betweenlateral edges of ventrolateral crestsgreater than about I.2; intemasalprocess ventrolaterally has facet for dorsallyoverlapping medial edge ofnasal; anterolateralprocess a poorly differentiated, broadly rounded shoulder;dorsal and ventral edgesof slot for receipt of prefrontal not excavatedmediallv: anterior end of orbital margin located anterior to ACTA PALAEONTOLOGICAPOLOMCA (45) (1) 67

anteroposteriormidpoint of frontals; and orbital margin deeply concave in dorsal or ventral outline, occasionallydeflected posterolaterally near posterior end. Remarks. - Neither of the named species of Celtedens is well documented. C. megacephalzsis known by the holotypeskeleton from nearPietraroia (lower Albian), Italy. This skeletonis poorly preservedand, consequently,difficult to interpret (Estes 1981;Gardnerin press). McGowan & Evans(1995) brieflyreported ontwo articulated skeletonsof C. ibericus,one of which preservesdetails of the soft tissue,both from Las Hoyas(upper Barremian), Spain. McGowan's (1994)more detailedinterpretations of all three skeletonsremain unpublished,although he (McGowan 1998)presented revised diagnosesfor both speciesand a controversial cranial reconstruction(see Gardnerin press)for C. ibericus. Celtedensis reliably known by frontals from another three localities: Ufra (Barremian,Spain), Purbeck (Berriasian,England), and Gui- marota (Kimmeridgian, Portugal) (McGowan & Ensom 1997; McGowan 1998). McGowan (1998) implied that frontals from Ufla and Guimarota may pertain to previ- ously unrecognizedspecies. McGowan (1998: p. I92) also reported Celtedensat Galve (Barremian), Spain, but did not figure examples of the frontals. Reports of Celtedensfrom the Middle Jurassic (upper Bathonian) of England (McGowan 1996, 1998)are incorrect (see account below); this raisesthe earliestoccurrence ofthe genus to the Kimmeridgian. Genusand speciesindeterminate Fig.4. Celtedensmegacephalus (Costa); McGowan 1996: p.233, figs I-9,ll-13. Celtedenscf. megacephalzs (Costa); McGowan & Ensom1997: p. 117;McGowan 1998: fig. lG. Celtedensibericus McGowan & Evans;McGowan 1998: fig. 4. Voucherspecimens: BMNH R.14157,UCK 14, 15, premaxillae; UCK 10, maxilla; UCK 01,03, dentaries; BMNH R. I 41 5 8- 14 1 60, UCK 26, 27, ft ontals. Horizonand locality: Middle Jurassic (upper Bathonian) Forest Marble Formation, Kirtlington Ce- mentQuarry, Oxfordshire, southcentral England. Remarks. - The Kirtlington Cement Quarry is one of four localities in the Forest Marble Formationto haveproduced albanerpetontid elements (Evans I992;Evans & Milner 1994).Fossils from the formationare the secondoldest record (late Bathonian) for the family, after an atlantalcentrum reported by Seiffert (1969) from Gardies(early Bathonianin age;Kriwet et al.1997), France.McGowan (1996) describeda modest collection of albanerpetontidskull and postcranialelements from Kirtlington and referred the specimensto Celtedenson the strengthof an incompletefrontal (UCK26; Fig. 4A). While this specimenmore closely resembledfrontals of Celtedensthan Albanerpeton in the apparent hourglass shape of the bone (the inferred primitive albanerpetontidstate) and the outline of the orbital margin, it is important to emphasize that none of the frontals from Kirtlington available to McGowan at the time of his study preservedthe diagnosticinternasal process. Such a specimenis now available: BMNH R.14158(Fig. 48, C) consistsof aboutthe anteriorone-third of apair of fused frontals,broken posteriorly between the slotsfor receiptof the prefrontals.As thereis no evidence from other specimensthat more than one albanerpetontidtaxon is repre- sentedat Kirtlington, BMNH R.14158and UCK 26 evidentlypertainto the samespe- cies. Whereasthe poorly differentiatedanterolateral processes on BMNH R.14158 68 Revis e d taxonomy of albanerpetontid amphibians.' GARDNER

Fig. 4. Frontalsandjaws ofAlbanerpetontidaegen. et sp.indet.; Middle Jurassic(upper Bathonian) Forest MarbleFormation,KirtlingtonCementQuarry, England. A. UCK26, posteriortwo-thirdsof fusedfrontals missing posterior end of both ventrolateral crests,ventral view, with arrow indicating anterior limit of orbital margin.B, C. BMNH R.14158,anterior one-third of fusedfrontals, dorsal and right lateralviews. D, UCK 15,incomplete rightpremaxilla, lacking dorsalend ofpars dorsalisandmedial parts ofpars palatinum and pars dentalis,lingual view, with arrow indicating suprapalatalpit. Broken surfacesare white. Scalebars = 1 mm: left scalebar is for frontals (A-C) and right scalebar is for premarilla (D). alsorecall the condition in Celtedens,the intemasalprocess instead resembles that of Albanerpetoruin being triangular in outline (the infened primitive albanerpetontid state)and in having an elongategroove along the lateral face for articulation with the nasal. Premaxillae from Kirtlington (Fig. 4D) are also distinctive in having the suprapalatalpit located more laterally within the external narial margin and facing laterolingually.By contrast,the suprapalatalpit lies more medially in the lingual face of the parsdorsalis and openslingually in Celtedensand Albanerpeton. This mixture of frontal and premaxillary characterstates precludes the Kirtlington albanerpetontid from membershipin either of the two currently recognizedgenera.

Conclusions r Frontals are diagnosticfor Albanerpeton,Celtedens, and speciesof Celtedens,as previousauthors have suggested.The relative diagnosticvalue of frontals in these casesmay be inflated,because no otherelements are as well known for Celtedens.In particular,I suspectthat betterjaw specimenswould also show specificlevel differ- enceswithin Celtedens.This is the caseinAlbanerpeton, where the premaxillais the mosttaxonomically informative element for species.Characters of the maxilla, dentary, andfrontals and inferred head-body sizeare also useful for diagnosingspecies of Albanerpeton. . I provide revised,differential diagnosesfor the Albanerpetontidae,Albanerpeton, andCeltedens. These are the first diagnosesfor the taxain which the inferredpolari- ties of characterstates are explicitly stated.One frontal autapomorphyis identified ACTA PALAEONTOLOGICAPOLONTCA (45) (l) 69

for eachgenus: the fusedfrontals are triangularin Albanerpetonand the intemasal processis bulbousin Celtedens. r A Middle Jurassicalbanerpetontid from Kirtlington cannotbe assignedto Celtedens or Albanerpeton,becausethe taxon in questionhas frontal characterstates of both generaand premaxillary character states not seenin eithergenus. This combination of characterstates, especially the lack of obviousgeneric level apomorphies,is not surprisingconsidering that the Kirtlington albanerpetontidpredates by some15 and 50 million years(Gradstein et al. 1995)the oldestunequivocal occuffences of, respectively,Celtedens in the Kimmeridgianof Portugal andAlbanerpeton in the up- permostAptian/lowermost Albian of Oklahoma,USA.

Acknowledgements

G.J. McGowan provided the final prompt for me to write this paper by sending me a reprint of his stimulating 1998 paper. I also thank the curators and collections managers listed in my earlier papers for accessto specimens,S.E. Evans for discussionsand freely sharing information on Old World albanerpetontids, G. Braybrook, G.F. Hanke, and B.R.K. Hunda for help with digitizing the figures and use of equipment, and J.-C. Rage and M. Borsuk-Bialynicka for their reviews. Funding for my studies has been provided by a University of Alberta Ph.D. Recruitment Scholarship, Dissertation Fellowship, and Andrew Steward Memorial Prize and by my parents and parents-in-laws. Special thanks to my ever supportive wife, N.J. Marklund.

References

Estes,R. 1964.Fossil vertebrates from theLate CretaceousLance Formation, eastern Wyoming.- Univer- sityof California Publicationsin GeologicalSciences 49, l-180. Estes,R. 1981.Gymnophiona,Catdata.In'P. Wellnhofer (ed.), Encyclopediaof Paleoherpetology,Prt2, 1-115. GustavFischer Verlag, Stuttgaft. Estes,R. & Hoffstetter,R. 1976.Les Uroddlesdu Miocbnede La Grive-Saint-Alban(Isdre,France). - Bul- ktin du MusdumNational d'Histoire Naturelle,3" s6rie,no. 398, Sciencesde Ia Terre 57,297-343. Evans,S.E. 1992.Small reptilesand amphibiansfrom the ForestMarble (Middle Jurassic)of Dorset.- Proceedingsof the Dorset Natural History and ArchaeologicalSociety ll4,2OIJO2. Evans,S.E. & Milner, A.R. 1994.Middle Jurassicmicrovertebrate assemblages from the British Isles.12.' N.C. Fraser& H.-D. Sues(eds),In theShadow of theDinosaurs: Early MesozoicTetrapods,303-321. Cambridge University Press,New York. Fox, R.C. & Naylor, B.G. 1982. A reconsiderationof the relationshipsof the fossil arnphtbianAlba- nerpeton.- CanarlianJournal of Earth Sciences19, ll8-128. Gardner,J .D . 1999a.Redescription of the geologicallyyoungest albanerpetontid (?Lissamphibia): Al&a- nerpetoninexpectatumEstesatdHoffstetter,19T6,fromthemiddleMioceneofFrance.-Annalesde Pal4ontologie 85, 57-84. Gardner, J.D. 1999b. The amphibian Albanerpeton arthridion and the Aptian-Albian biogeography of albanerpetontids.- Palaeontology 42, 529-544. Gardner,J.D.l999c.NewalbanerpetontidamphibiansfromtheAlbian-ConiacianofUtah,USA-bridging the gap.- Journal of VertebrateP ale ontolo gy 19, 632438. Gardner, J.D. (in press). Commefis on the anterior region of the skull in the Albanerpetontidae (Temnso- spondyli;Lissamphibia). - NeuesJahrbuchfiir Geologieund Palciontologie,Monatshefte. Gardner,J.D. & Averianov,A.O. 1998.Albanerpetontidamphibians fromMiddle Asia.-Acta Palaeonto- logic a Polonic a 43,453467 . Gradstein,F.M., Agterberg,F.P., Ogg, J.G., Hardenbol,J., Veen, P. van, Thierry, J., & Huang,Z. 1995. A Triassic, Jurassicand Cretaceoustime scale.1n: W.A. Berggren,D.V. Kent, M.-P. Aubry, & Revised taxonomy of albanerpetontid amphibians: GARDNER

J. Hardenbol (eds), Geochronology, Time Scales and Global Stratigraphic Correlation. -SEPM Spe- cial Publication 54,95-126. Kriwet, J., Rauhut, O.W.M., & Gloy, U. 1997. Microvertebrate remains (Pisces, Archosauria) from the Middle Jurassic of southern France. - Neues Jahrbuch fir Geologie und Palaontologie, Abhand- lungen 206, 1-28. McGowan, G.J. 1994.A description of new albanelpetontid materialffom the Mesozoic of Europe and its bearing on the systematicposition of the group. Unpub1ishedPh.D. thesis, University College London. McGowan, G.J. 1996.Albanerpetontid amphibians from the Jurassic (Bathonian) of southern England. In: M. Morales (ed.), The Continental Jurassic. -Museum of Northern Arizona Bulletin 60,227-234. McGowan, G.J. 1998.Frontals as diagnostic indicators in fossil albanerpetontid amphibians. -Bulletin of the National Science Museum, C (Geology and Paleontology) 24,185-194. McGowan, G.J. &Evans, S.E. 1995. Albanerpetontid amphibians from the Cretaceous of Spain. -Nature 373,143-145. McGowan, G.J. & Ensom, PC. 1997. Albanerpetontid amphibians from the Lower Cretaceous of the Isle of Purbeck, Dorset. -Proceedings of the DorsetNatural History andArchaeologica1Society 118,113-1 17. Milner, A.R. 1988. The relationships and origin of living amphibians. In: M.J. Benton (ed.), The Phylogeny and Classification of the Tetrapods, Volume 1: Amphibians, Reptiles, Birds. - Systematics Associa- tion Special Volume 35A, 59-102. Clarendon Press, Oxford. Nessov, L. A. (Nesov, L.A.) 1981. Cretaceous salamanders and frogs of KyzylkumDesert [in Russian with English abstract]. - Trudy Zoologi&skogo Znstituta, Akademia Nauk SSSR 101,57788. Rage, J.-C. & Hossini, S. (in press). Les amphibiens du Mioctne moyen de Sansan (Gers, France). - Mhoires du Muslum National d'Histoire Naturelle. Seiffert, J. 1969. Urodelen-Atlas aus dem obersten Bajocien von SE-Aveyron (Siidfrankreich). -Palaon- tologische Zeitschrift 43, 32-36. Sigogneau-Russell, D., Evans, S.E., Levine, J.F., & Russell, D.A. 1998. The Early Cretaceous rnicro- vertebrate locality of Anoual, Morocco: a glimpse at the small vertebrate assemblages of Africa. In: S.G. Lucas, J.I. Kirkland, & J.W. Estep (eds), Lower andMiddle Cretaceous Terrestrial Ecosystems. - New Mexico Museum of Natural History and Science Bulletin 14, 177-181.

Rewizja taksonomiczna piaz6w z rodziny Albanerpetodontidae

JAMES D. GARDNER

Streszczenie

Rodzaje albanerpetodont6w klasyfikowano na podstawie cech morfologicznych szczqk i kos'ci czolowych, ale rzadko zastanawiano siq nad przydatnos'ciq taksono- micznq tych cech. Budowa ko6ci czolowych jest diagnostyczna dla rodzaj6w Alba- nerpeton i Celtedens oraz gatunk6w w obrqbie tego ostatniego (zwlaszcza, ze brak jest danych na temat zr6znicowania morfologii szczqk w obrqbie tego rodzaju). W obrqbie rodzaju Albanerpeton gatunki wyr6zniajq siq cechami kos'ci czolowych i szczqk oraz rozmiarami ciala. Podano diagnozy r6znicujqce dla obu rodzajdw opisanych na podstawie powyiszych cech, obejmujqce take morfologiq krqg6w. Kazdy z rodzaj6w odznacza siq jednq autapomorfiq: Albanerpeton - tr6jkqtnymi zros'niqtymi kos'Cmi czolowymi, a Celtedens - pqkatym wyrostkiem miqdzynoso- wym tych kos'ci. Zagadkowy albanerpetodont ze 6rodkowej jury (baton) Anglii ma mieszane cechy, nie pozwalajqce zaliczyC go do wyzej wymienionych. Oznacza to, ze Celtedens znany jest od p6inej jury (kimeryd) a Albanerpeton - od wczesnej kredy (apvalb).