Anoualerpeton, Gardner & Evans & Sigogneau-Russell, 2003

Gardner, James D., Evans, Susan E. & Sigogneau-Russell, Denise, 2003, New albanerpetontid amphibians from the Early Cretaceous of Morocco and Middle Jurassic of England, Acta Palaeontologica Polonica 48 (2), pp. 301-319 : 302-303

Family Albanerpetontidae Fox and Naylor, 1982 Anoualerpeton gen. nov.

Type species: Anoualerpeton unicus sp. nov.

Other species: Anoualerpeton priscus sp. nov.

Etymology: Anoual,thetypelocality nearthecity ofAnoualin Morocco + erpeton,Greeknounmeaning“creeping[creature]”,nowusedforamphibians and reptiles.

Distribution.—Middle Jurassic (late Bathonian), England, and Early Cretaceous (Berriasian), Morocco.

Diagnosis.—Genus of albanerpetontid having no recognized autapomorphies. Differs from Celtedens and most species of Albanerpeton , but convergently resembles A. nexuosus Estes 1964 , in two maxillary and dentary synapomorphies: occlusal edge of bone convex occlusally in labial or lingual outline and teeth about one−third of distance from anterior end of tooth row markedly longer than nearby teeth. In addition to generic characters listed below, primitively differs from A. nexuosus in having premaxillae unfused, relatively more gracile in build, and more weakly sutured dorsally with nasals, with boss covering less than about one−third of premaxillary pars dorsalis and ornamented with irregular pits and ridges, with suprapalatal pit relatively smaller and opening higher on pars dorsalis, and with dorsal ridge on lingual edge of maxillary process lower and in having maxilla with premaxillary lateral process relatively longer. Primitively differs from Celtedens and Albanerpeton in having premaxilla with suprapalatal pit in pars dorsalis facing more laterally; from Celtedens and resembles Albanerpeton in having frontals with internasal process tapered anteriorly and lateral edge of process indented by anteroposteriorly elongate groove for tongue−in−groove contact with medial edge of nasal; from Albanerpeton and resembles Celtedens in having frontals relatively longer (midline length no less than about 1.2 times posterior width) and more nearly bell−shaped or rectangular in dorsal or ventral outline; and from Albanerpeton (condition not reliably known for Celtedens ) in having premaxilla with canal between dorsal and ventral openings of palatal foramen extending dorsolaterally–ventromedially through pars palatinum.

Remarks.— Anoualerpeton differs from Albanerpeton and Celtedens in a unique combination of eight character states. Chief among these are two linked characters that describe size heterodonty of teeth and the profile of the occlusal margin on the maxilla and dentary. Marginalteeth in albanerpetontids are highly pleurodont—i.e., teeth are attached along about the basal one−half or more of their labial surface to the inner wall of the jaw. As tooth lengths vary along the jaw, so must the depth of the pars dentalis on the maxilla and the height of the dental parapet on the dentary to ensure that the teeth remain adequately braced labially ( Gardner 2002). Teeth in most albanerpetontids are moderately heterodont in size along the maxillary and dentary row. The longest teeth occur about one−third of the distance from the anterior end of the tooth row, but are not substantially longer than nearby teeth in the same row. Concomitantly, the occlusal edge of the jaw is essentially straight in labial outline (see Gardner and Averianov 1998: fig. 2A, B). These two character states appear to be primitive for albanerpetontids, based on outgroup comparisons with other temnospondyls ( Gardner 2002). Enlargement of teeth about one−third of the distance posteriorly (i.e., from anterior end) along the maxillary and dentary tooth rows and a more strongly convex occlusal margin, with the apex adjacent to the longest teeth, are derived character states within the Albanerpetontidae ( Gardner 2002) . These apomorphies occur in the two species of Anoualerpeton , in the North American Campanian and Maastrichtian Albanerpeton nexuosus ( Estes 1964: figs. 43e, 44c; Gardner 2000b: figs. 2D, 3A), and in an indeterminate dentary from the Albian–Cenomanian boundary in Utah, USA ( Gardner 1999c: fig. 3D, E). The nested sets of synapomorphies that place A. nexuosus crownward within Albanerpeton ( Gardner 2000b, 2002; this study) argue against a close relationship with Anoualerpeton and, instead, imply that strongly heterodont teeth and a convex occlusal margin on the maxilla and dentary developed convergently in A. nexuosus and Anoualerpeton . In this context it is worth noting that both conditions tend to be more pronounced in A. nexuosus , although we have not been able to quantify these differences. In some dentaries and maxillae of A. nexuosus the enlarged teeth appear relatively larger or more massive and the occlusal edge of the bone is more strongly convex in labial or lingual outline; in extreme cases the occlusal edge of the dentary assumes a more nearly angular profile, with an obtuse−angled apex.

Stratigraphical distributions of character states among albanerpetontids and, where informative, outgroup comparisons with other temnospondyls imply that the remaining character states that are diagnostic at the generic level for Anoualerpeton are primitive for albanerpetontids, as follows: (1) suprapalatal pit in premaxilla opens laterolingually (versus opens lingually in Celtedens and Albanerpeton ); (2) canal between dorsal and ventral openings of palatal foramen in premaxilla extends dorsolaterally–ventromedially (versus vertically in Albanerpeton ; condition unknown in Celtedens ); (3) internasal process on frontals tapered anteriorly (shared with Albanerpeton ; versus bulbous in outline in Celtedens ); (4) internasal process has lateral groove for tongue−in−groove contact with nasal (shared with Albanerpeton ; versus groove absent and, instead, lateral margin of process dorsally overlaps medial edge of nasal in Celtedens ); (5) fused frontals relatively elongate, with midline length no less than about 1.2 times posterior width (shared with Celtedens ; versus midline length no more than about 1.2 times posterior width in Albanerpeton ); and (6) fused frontals more nearly bell−shaped or rectangular in dorsal or ventral outline (shared with Celtedens ; versus triangular in Albanerpeton ).

Albanerpetontid specimens at Anoual consistently differ from those at Kirtlington in two premaxillary and three frontal characters. This suite of differences, along with the considerable temporal and geographical gaps between the Anoual and Kirtlington localities, support our interpretation that specimens from each locality pertain to a different species of Anoualerpeton . For the species from Anoual, outgroup comparisons suggest the taxon exhibits the derived state for one character describing the form of the paired anterolateral processes on the frontals, while stratigraphical distributions of character states within the Albanerpetontidae suggest the species also exhibits the derived states for two premaxillary characters describing the positions of the suprapalatal pit and the dorsal opening of the palatal foramen. For the species from Kirtlington, outgroup comparisons suggest the taxon exhibits the derived state for one character describing the form of the internasal process on the frontals, while both outgroup comparisons and stratigraphical distributions of character states within the Albanerpetontidae suggest the taxon exhibits the derived state for one character describing the form of the ventrolateral crests.