New material ascribed to Albanerpetontidae (Lissamphibia; Allocaudata) from the Lourinhã Formation: evidence for intraspecific variation

Guillaume, A. R. D., Natário C., Moreno-Azanza M., & Mateus O. (2021).  New material ascribed to Albanerpetontidae (Lissamphibia; Allocaudata) from the Lourinhã Formation: evidence for intraspecific variation. XIX Encontro de Jovens Investigadores em Paleontologia. 50-51.





Albanerpetontidae form an enigmatic extinct group of highly derived small ballistic tongue feeding amphibians. They ranged from the early Bathonian of Europe and Morocco to the early Pleistocene of Italy, and were predominant in Laurasia, mainly in Europe and North America. 

Due to their small size, their fossil record is fragmentary and scarce, most generally recovered as isolated fragmented bones from vertebrate microfossil assemblages. Their characteristic fused frontals yield a relatively large set of diagnostic features, allowing to identify taxa at the species level.

The Late Jurassic Guimarota microfossil assemblage yielded thousands of albanerpetontid specimens, although only partial results and identification were none of the result have been formally published since 17 years. 

Here, we provide revision of 40 frontal bones from Guimarota and descriptions of 31 new specimens recovered from the coeval Lourinhã Formation, whose variations suggest intraspecific variation due to ontogeny. With the words you saved here and in the end, specify from which localities you recover the specimens.

The All specimens from the Lourinhã Formation and Guimarota all share and hourglass outline shaped frontal bone, with a curved orbital margin and a broad, blunt internasal process, which are diagnostic features of Celtedens, supporting the assessment to this genus. However, 15 specimens from Lourinhã display a vermicular dorsal ornamentation, made of tiny dorsal grooves defining irregular flat polygons, not observed in the Guimarota specimens, and , which are distinguishable of the more characteristic polygonal, concave pit dorsal ornamentation observed in other albanerpetontids. Nevertheless, the pits vary in shape and depth among our specimens, from irregular and shallow to honeycomb and deep. Variations in size and shape in the features observed in 10 fairly the ten best preserved Portuguese specimens would suggests these morphological differences could may represent ontogenetic intraspecific variations.

Our results highlight the hidden diversity of the Lourinhã Formation, and its ecological similarities with the coeval Guimarota assemblage.

These new occurrences and material should allow us to understand better the albanerpetontid paleobiogeography during the Late Jurassic and Early Cretaceous in Europe, which seem to be key period in their evolutionary history.

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