Austronaga (Triassic marine archosauromorph) fossil with soft tissue internal organ preservation (free pdf)

[Ben Creisler]

Ben Creisler

bcre...@gmail.com

A new paper:

Free pdf:

Wei Wang, Nicholas C. Fraser, Stephan N. F. Spiekman, Zhiheng Li, Olivier Rieppel, Hong Lei, Torsten M. Scheyer, and Chun Li (2026)
Highly aquatic marine stem archosaur with soft tissue preservation
Science Advances 12(31): eaeb7528
DOI: 10.1126/sciadv.aeb7528
https://www.science.org/doi/10.1126/sciadv.aeb7528

Free pdf:
https://www.science.org/doi/epdf/10.1126/sciadv.aeb7528

Archosauromorpha is a dominant reptile clade that primarily occupied terrestrial ecosystems with limited secondarily aquatic invasions that are poorly known. Here we report on a well-preserved Triassic reptile representing the earliest stem-archosaur to evolve unequivocal aquatic specializations. This taxon exhibits a suite of aquatic adaptations previously unknown in stem-archosaurs, such as hyperphalangy, enhanced paddle-like forelimbs, and a loss of articulation between the sacrum and pelvis, indicating an advanced aquatic lifestyle. The fossil exhibits the oldest known stomach, liver, and intestinal preservations in reptiles. Our findings provide unexpected insights into the early aquatic diversification of Archosauromorpha during the Triassic marine ecosystem recovery and highlight a conservative gastrointestinal system in an early Mesozoic vertebrate. In the absence of clear terrestrial members of the other major Mesozoic marine reptile lineages (e.g., ichthyosaurs and sauropterygians), this discovery provides an unambiguous example of such a lineage including both decidedly terrestrial and extensively marine forms, providing tantalizing evidence for the land-to-sea transition in Triassic reptiles.

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News:

Spectacular discovery provides insight into the internal organs of a marine reptile

https://www.eurekalert.org/news-releases/1137431

https://phys.org/news/2026-07-unique-fossil-reveals-internal-million.html

https://www.newscientist.com/article/2582138-spectacular-fossil-preserves-internal-organs-of-ancient-marine-reptile/

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