First record of a basal mammaliamorph from the early Late Triassic Ischigualasto Formation of Argentina

Researchers have identified Pseudotherium argentinus, a new basal mammaliamorph cynodont from the early Late Triassic Ischigualasto Formation in Argentina. This discovery provides critical insights into the evolutionary path leading to mammals and Mammaliaformes. The study utilized high-resolution X-ray computed tomography (CT) to analyze the well-preserved skull of Pseudotherium, revealing unique features such as an elongated but uncoiled cochlea and turbinal-like bones in the nasopharyngeal passage. Phylogenetic analysis suggests that Pseudotherium may be closely related to Tritylodontidae or lie within Mammaliamorpha, though relationships remain uncertain due to limited fossil data. The study highlights the need for more complete specimens and broader CT datasets to clarify these evolutionary relationships. The CT dataset of Pseudotherium argentinus is publicly available under a Creative Commons license.

Wallace, R. V. S., Martínez, R., & Rowe, T. (2019). First record of a basal mammaliamorph from the early Late Triassic Ischigualasto Formation of Argentina. Plos One, 14(8), e0218791. https://doi.org/10.1371/journal.pone.0218791