Archovember 2025 Day 28
Phytosaur Smilosuchus gregorii, of Late Triassic, USA!
While the pseudosuchians were still figuring things out in the Triassic, trying out diverse body types, the entirely unrelated phytosaurs had already perfected the semi-aquatic reptilian predator bodyplan. Phytosaurs are known from many different morphologies, specifically with vastly different skull forms, though they can be told apart from pseudosuchians by the position of their nostrils close to their eyes on their snout. One of the largest phytosaurs was the North American Smilosuchus. There are three known species of Smilosuchus, each with different skull morphologies. Smilosuchus gregorii, seen here, had a robust skull, less long and slender than its relatives. Like other phytosaurs, it had heterodont teeth; with large tusks at the front of its mouth for impaling prey, and smaller, blade-like teeth near the back for slicing flesh. It had powerful jaw muscles, and was likely able to hunt large prey, perhaps ambushing the giant dicynodonts and even aetosaurs of the time.
Smilosuchus gregorii was found in the Late Triassic Chinle Formation of Arizona, USA. It would have lived alongside its Smilosuchus relatives, S. adamanensis and S. lithodendrorum, and other phytosaurs like Leptosuchus, Machaeroprosopus, Pravusuchus, and Protome. Pseudosuchians lived here too, though they had the land colonized while the phytosaurs dominated the waters. These included the aetosauriformes Acaenasuchus and Revueltosaurus, the true aetosaurs Adamanasuchus, Calyptosuchus, Desmatosuchus, Kryphioparma, Paratypothorax, Rioarribasuchus, Scutarx, Typothorax, and Tecovasuchus, the small, cat-like Hesperosuchus and Parrishia, the bipedal, theropod-like predator Poposaurus, and the giant land predator Postosuchus. Other archosaurimorphs Smilosuchus would have come across would have been the tanystropheid Akidostropheus, doswelliids like Doswellia and Vancleavea, allokotosaurs like Puercosuchus and Trilophosaurus, and others like Syntomiprosopus. Other animals that lived here (and could have been preyed on by Smilosuchus) included the enigmatic Acallosuchus, drepanosaurs like Ancistronychus, Fabanychus, and Skybalonyx, cynodonts like Kataigidodon, the dicynodont Placerias (thought to be Smilosuchus’ preferred prey), and temnospondyl amphibians like Anaschisma.
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