Argochampsa

Description

Argochampsa is based on OCP DEK-GE 1201, a nearly complete skull from the Oulad Abdoun Basin, in the vicinity of Khouribga, Morocco. The skull, 43.3 centimeters long (17.0 in), had a long, narrow snout, marking it as a longirostrine crocodilian; the snout made up about 70% of the skull's length. The premaxillae at the tip of the snout were downturned, and the tip somewhat squared off, with the first few tooth positions in a straight line perpendicular to the long axis of the skull. There were five teeth in each premaxilla and 26 in each maxilla (the main tooth-bearing bone of the upper jaw). The nasal bones were fused, and there were several short diastemas or gaps in the tooth row at the tip of the snout. Argochampsa had concave depressions on the internal surface of the lacrimal and prefrontal bones, indicating the presence of salt glands.

Hua and Jouve performed a cladistic analysis incorporating their new taxon, and found Argochampsa to be a gavialoid, but outside of the clade Gavialidae. They noted that the snout shape of Argochampsa is unusual among crocodilians, with only pholidosaurids and Terminonaris having similarly shaped snout tips, and suggested that this layout may have facilitated precise occlusion. Argochampsa lived in an environment otherwise dominated by dyrosaurid marine crocodyliforms.

Argochampsa krebsi was included in the study on the phylogenetic relationships of putative fossil gavialoids published by Lee & Yates (2018). The authors considered it most likely that Argochampsa was not a gavialoid, or even a crocodylian, but rather a member of the clade of non-crocodylian eusuchians that also included the genera Eogavialis, Eosuchus, Eothoracosaurus and Thoracosaurus.

References

References

1. (6 September 2021). "Phylogenetic analysis of a new morphological dataset elucidates the evolutionary history of Crocodylia and resolves the long-standing gharial problem". [[PeerJ]].
2. (2004). "A primitive marine gavialoid from the Paleocene of Morocco". Journal of Vertebrate Paleontology.
3. Jouve, Stéphane. (2006). "New material of ''Argochampsa krebsi'' (Crocodylia: Gavialoidea) from the Lower Paleocene of the Oulad Abdoun Basin (Morocco): phylogenetic implications". Geobios.
4. Pligersdorffer, Carly C.. (15 January 2025). "Evaluation of the endocranial anatomy of the early Paleogene north African gavialoid crocodylian Argochampsa krebsi and evolutionary implications for adaptation to salinity tolerance in marine crocodyliforms". [[Journal of Anatomy]].
5. (2018). "Tip-dating and homoplasy: reconciling the shallow molecular divergences of modern gharials with their long fossil record". Proceedings of the Royal Society B: Biological Sciences.