Rutiodon

Extinct genus of reptiles

Rutiodon ("Wrinkle tooth") is an extinct genus of mystriosuchine phytosaurs from the Late Triassic of the eastern United States. The type species of Rutiodon, Rutiodon carolinensis, encompasses a large number of skulls and assorted postcranial fossils discovered in the Cumnock Formation of North Carolina. Fossils referable to the species are also known from Pennsylvania, New Jersey, and Virginia. Rutiodon carolinensis is the most well described species of phytosaur in eastern North America, though its validity as a natural taxon has been questioned. Some paleontologists also recognize a larger and more robust species, Rutiodon manhattanensis, which is known from teeth and postcranial fossils from New Jersey and Pennsylvania.

Like other phytosaurs, Rutiodon strongly resembled a crocodile, but its nostrils were positioned far back on the head, close to the eyes, instead of at the tip of the snout. It had enlarged front teeth, and a relatively narrow jaw, somewhat resembling that of a modern gharial. This suggests that this carnivore probably caught fish and it may also have snatched land animals from the waterside. Rutiodon was among the largest carnivorous animals of its environment, measuring up to long and weighing about .

The type species of Rutiodon is R. carolinensis. It was originally named by Ebenezer Emmons in 1856, based on fossils from the Deep River coal field (Cumnock Formation) of North Carolina. The original fossils include five striated teeth and associated vertebrae, ribs, and interclavicle fragments. Emmons' phytosaur skull was originally stored in the Williams College geological museum, Many skulls and partial skeletons of R. carolinensis have been discovered near Egypt, North Carolina, and are now housed and displayed at the American Museum of Natural History (AMNH). Doyle and Sues (1995) described a well preserved phytosaur skull (SMP VP 45) from the New Oxford Formation in York County, Pennsylvania. This skull was very similar to skulls previously referred to R. carolinesis. They considered R. carolinensis to be an undiagnostic species, as it was originally diagnosed based on teeth. According to these authors, "Rutiodon" is a metataxon of eastern phytosaurs for which monophyly cannot be established. In 1896, Marsh mentioned a phytosaur skull from Chatham County, North Carolina. This was the second phytosaur skull found in the area, after that of Emmons (1860). Marsh named his phytosaur skull Rhytidodon rostratus. Belodon validus is considered dubious and undiagnostic,

Fossils of a second species, R. manhattanensis, were discovered in 1910 from "red sandy marl" (Stockton Formation)

Some authors have referred R. manhattanensis to "Clepsysaurus"

Several papers in the late 20th century extended the scope of the genus Rutiodon, allowing it to encompass phytosaur species from both the eastern and western United States. Western species lumped into Rutiodon include nearly all species previously placed into the genera Leptosuchus, Machaeroprosopus, and Pseudopalatus. A 1995 paper, and most subsequent studies on phytosaurs, disagreed with the idea that Rutiodon encompassed western phytosaur species. Recent papers agree that Rutiodon occupies a tier of the phytosaur family tree more derived than Paleorhinus and less derived than Leptosuchus. mirroring older suggestions that Angistorhinus was directly ancestral to Rutiodon. Over half of the most parsimonious trees in the 2023 description of Colossosuchus positioned Rutiodon as the sister taxon to Volcanosuchus.