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A new albanerpetontid, Wesserpeton evansae gen. et sp. nov., from the Early Cretaceous (Barremian) Wessex Formation of the Isle of Wight, southern England, is described. Wesserpeton is established on the basis of a unique combination of primitive and derived characters relating to the frontals and jaws which render it distinct from currently recognized albanerpetontid genera: Albanerpeton (Late Cretaceous to Pliocene of Europe, Early Cretaceous to Paleocene of North America and Late Cretaceous of Asia); Celtedens (Late Jurassic to Early Cretaceous of Europe); and Anoualerpeton (Middle Jurassic of Europe and Early Cretaceous of North Africa). Although Wesserpeton exhibits considerable intraspecific variation in characters pertaining to the jaws and, to a lesser extent, frontals, the new taxon differs from Celtedens in the shape of the internasal process and gross morphology of the frontals in dorsal or ventral view. It differs from Anoualerpeton in the lack of pronounced heterodonty of dentary and maxillary teeth; and in the more medial loca− tion and direction of opening of the suprapalatal pit. The new taxon cannot be referred to Albanerpeton on the basis of the morphology of the frontals. Wesserpeton currently represents the youngest record of Albanerpetontidae in Britain.
To evaluate stratigraphic evidence for the time of origin of the clade of extant amphibians (Lissamphibia), we attempt to establish a confidence interval on the lower bound of the stratigraphic range of this clade. This is based on the stratigraphic distribution of 1207 fossiliferous localities that have yielded lissamphibians, the relative area of sedimentary rocks from various periods (upper Paleozoic to present) exposed on the continents, and ten exponential−growth models of lissamphibian diversity that differ by the assumed effects of three major biological crises and the assumed starting times of lissamphibian diversification. The results suggest a more recent origin of Lissamphibia than advocated in most recent molecular studies. They are also more compatible with monophyly than with polyphyly of the extant amphibians, but heavily depend on poorly constrained assumptions about lissamphibian extinction rates during biological crises. Counts of lissamphibian diversity through time that consider ghost lineages and stage durations show moderate declines across the Cretaceous–Paleogene and Oligocene–Miocene boundaries.
A third albanerpetontid genus, Anoualerpeton gen. nov., is erected for two new species: An. unicussp. nov. (type species) from the Early Cretaceous (Berriasian) of Morocco and An. priscus sp. nov. from the Middle Jurassic (late Bathonian) of England. Anoualerpeton differs from the exclusively Laurasian albanerpetontid genera Albanerpeton (Early Cretaceous– Paleocene, North America; Miocene, Europe) and Celtedens (?Late Jurassic and Early Cretaceous, Europe) in a unique combination of primitive and derived character states of the jaws and azygous frontals. Monophyly of Anoualerpeton is supported by two synapomorphies of the maxilla and dentary (occlusal margin convex in labial outline and teeth strongly heterodont in size anteriorly) that are convergent with an unrelated, relatively derived Late Cretaceous species of Albanerpeton from North America. The two species of Anoualerpeton differ in character states of the premaxilla and azygous frontals. Cladistic analysis of 20 characters scored for ten albanerpetontid taxa postulates Anoualerpeton as the sister−taxon of Albanerpeton + Celtedens. The sister−pair of Albanerpeton + Celtedensis founded on one or, perhaps, two premaxillary synapomorphies. Anoualerpeton unicus documents the only known Gondwanan occurrence for the Albanerpetontidae and provides a minimum age of basal Cretaceous for the establishment of the clade in Africa. Characters of the mandible, vertebrae, and limbs support the interpretation that Ramonellus (Aptian; Israel) is a caudate, not an albanerpetontid.
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