Plasticity in the morphology of the fused frontals of Albanerpetontidae (Lissamphibia; Allocaudata)

Abstract

Albanerpetontidae form an enigmatic extinct group of lissamphibians, ranging from the early Bathonian to the early Pleistocene. The Upper Jurassic outcrops of Portugal yield a large collection of material, suitable for addressing the intraspecific variation in and diagnostic potential of the characteristic fused frontals. We revise 58 specimens from the Guimarota beds in of the Kimmeridgian Alcobaça Formation and describe 64 new frontal bones from the Kimmeridgian -Tithonian Lourinhã Formation. Smaller specimens exhibit a vermicular dorsal ornamentation, while it is polygonal in larger specimens and other albanerpetontids. Compared to small specimens, larger specimens display: (1) larger ventrolateral crests extending posteriorly after the parietal margin; (2) an relatively shorter internasal process relatively shorter; (3) a frontal width across posterior edges relatively smaller; and (4) a ventromedian crest less pronounced.Morphometric analyses suggest a single species with different ontogenetic stages.Specimens are attributed to aff. Celtedens sp., based on a bell-shaped outline with a curved orbital margin (although variable in Portuguese specimens), and a flabellate, bulbous-shaped internasal process. They areThe species is more similar to C. megacephalus than C. ibericus, but its phylogenetic position remains comprises an unresolved trichotomy. Our results show that intraspecific variation and homoplasy render the fused frontal non-diagnostic below the generic level.

14th Symposium on Mesozoic Terrestrial Ecosystems and Biota

“…Therefore, albanerpetontid taxonomy is mostly based on few but highly diagnostic bones (Gardner, 2000), as the fused frontals, considered to be key to both identifying and diagnosing taxa at generic and specific level (Gardner, 2000;McGowan, 1998). However, recent works challenged such use, due to plasticity and intraspecific variation in the frontals and other bones (Guillaume et al, 2022;Sweetman & Gardner, 2013). In this work we present new material from the Lourinhã Formation (Kimmeridgian-Tithonian), which includes cranial and post-cranial elements, in order to better characterize the anatomy of the albanerpetontid from the Late Jurassic of Portugal (Figure 1).…”

A new gnathosaurine (Pterosauria, Archaeopterodactyloidea) from the Late Jurassic of Portugal

“…The middle level comprises Jurassicorbula edwarsi , Isognomon lusitanica , Nerinea , coprolites, fish, Eomiodon securiformes , echinoids (outcropping at the base of Praia do Caniçal), while the upper level fauna consists of Jurassicorbula edwarsi , abundant ostreids, pleurosternidae turtles, and Isognomon lusitanica (outcropping at the top of Praia do Caniçal) ( Mateus, Dinis & Cunha, 2017 ). The member is known to bear abundant dinosaur remains, including bones, eggs, and tracks ( Ribeiro et al, 2014 ; Mateus et al, 2011 ), and also crocodylomorphs ( Young et al, 2014 ), turtles ( Pérez-Garcí, 2015 ; Pérez-García & Ortega, 2022 ), pterosaurs ( Bertozzo et al, 2021 ), mammals, lissamphibians, and lepidosaurs ( Mateus, Dinis & Cunha, 2017 ; Guillaume et al, 2023 ).…”