Redescription of the overlooked basal frog Wealdenbatrachus reveals increased diversity among Early Cretaceous anurans

Abstract

The anuran Wealdenbatrachus jucarensis Fey, 1988 is represented by several specimens, each consisting of an association of disarticulated bones preserved on slabs from a lignite mine near the village of Uña, Cuenca Province, Spain, from which remains of plants and other vertebrates also have been recovered. The bearing unit, La Huérguina Formation, is estimated to be late Barremian in age. Originally these anuran specimens were considered to represent a crown-group costatan closer to the living Discoglossus than to Alytes or Bombina. Herein we redescribe this material, including some hitherto unknown skeletal elements, such as nasal and atlas, and reinterpreting other elements, such as pterygoid and squamosal. Our observations and comparisons led us to validate this taxon and to present an updated restoration. It is noteworthy that several characters that have been used to ally Wealdenbatrachus with the early Barremian Eodiscoglossus santonjae occur widely in basal frogs, thus probably being plesiomorphic at this phylogenetic level, and contrast sharply with the conditions in living costatans. Available information points to a position of W. jucarensis outside the node that unites crown-group costatans, as a relatively basal taxon within Anura.