23-9 Addressing amniote phylogeny with new specimens elucidates the evolution of reptilian olfaction

Session: Phylogenetic and Computational Approaches in Paleobiology and Paleoecology, Part I

Presenting Author:

Authors:

Abstract:

Early amniote phylogeny is currently in a state of flux, with recent phylogenetic hypotheses suggesting drastically different topologies than more traditional works. Recent work suggests that some aspects of newer topologies may be a result of sampling bias or inadequate anatomical study (e.g., some or all varanopids as stem reptiles), while others may reflect actual evolutionary relationships (e.g., “parareptiles” as paraphyletic). These issues are further compounded by two additional problems: (1) entirely extinct clades can only be assessed based on morphological data, and molecular data cannot be used to resolve uncertain relationships, and (2) Bayesian and Parsimony frameworks often produce discordant topologies, and there is currently no consensus as to which analytical framework is more appropriate for morphological datasets composed entirely of extinct taxa. Although we are need ways to address these problems, particularly because sampling and analytical issues differently affect many taxonomic groups, we can still glean insights into trait evolution in some instances. Here we present new data on the early Permian stem reptile Protorothyris archeri based on µCT segmentations. We included this specimen in a character-taxon matrix of 177 taxa and 628 characters that tests the relationships of early-diverging amniotes. We recovered occasionally strikingly different relationships between Parsimony and Bayesian analyses, but the placement of Protorothyris archeri as an early-diverging stem reptile in both types of trees allows us to examine evolutionary transitions across stem reptiles. By examining a selection of Paleozoic and Triassic amniotes, we found evidence for improved olfactory capabilities in stem reptiles developing during the Permian, suggesting there may have been improvements in overall olfactory function within the lineage. We encourage further anatomical work to improve uncertain areas of early amniote phylogeny and to elucidate the utility of potential osteological correlates for reconstructing sensory evolution during the initial terrestrialization of tetrapods.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-8686

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