New albanerpetontid species (Lissamphibia) from the Late Jurassic of Portugal

The Albanerpetontidae are a group of small extinct lissamphibians ranging from the Bathonian to the early Pleistocene. The Upper Jurassic of Portugal is known to yield a large collection of albanerpetontid remains, ascribed to the genus Celtedens. However, recent studies have shown that the frontal bones used for species diagnosis display important intraspecific variation. Here, we describe 468 bones from the Kimmeridgian-Tithonian Lourinhã Formation, together with thousands of remains from the Guimarota beds of the Kimmeridgian Alcobaça Formation. They support the erection of a new genus and species, Nabia civiscientrix gen. et sp. nov., characterized by a unique combination of five synapomorphies: a bulbous/flabellate outline of the internasal process of the frontal in dorsal or ventral view; no sculpture on the postorbital wing of the parietals; the dorsal condyle of the axis with a recurved edge; the long axis of the iliac shaft strongly tilted posteriorly; and a limited pubic/ischial articulation flaring. This material represents the oldest albanerpetontid species from the Iberian Peninsula and potentially the third described from the Jurassic, during which time it played a major palaeobiogeographical role in relation to Europe, north-western Africa and North America. Our results further confirm the need to revise Celtedens. The material from the Lourinhã Formation suggests that other multi-specific microfossil vertebrate bonebeds should contain a greater variety of elements than is reported. We stress the need to review unpicked and unidentified material to look for postcranial bones rather than focusing only on cranial elements, as in combination they aid a better characterisation of this group.