#rutiodon

By Ripley Cook

Etymology: Wrinkle Tooth 

First Described By: Emmons, 1856

Classification: Biota, Archaea, Proteoarchaeota, Asgardarchaeota, Eukaryota, Neokaryota, Scotokaryota Opimoda, Podiata, Amorphea, Obazoa, Opisthokonta, Holozoa, Filozoa, Choanozoa, Animalia, Eumetazoa, Parahoxozoa, Bilateria, Nephrozoa, Deuterostomia, Chordata, Olfactores, Vertebrata, Craniata, Gnathostomata, Eugnathostomata, Osteichthyes, Sarcopterygii, Rhipidistia, Tetrapodomorpha, Eotetrapodiformes, Elpistostegalia, Stegocephalia, Tetrapoda, Reptiliomorpha, Amniota, Sauropsida, Eureptilia, Romeriida, Diapsida, Neodiapsida, Sauria, Archosauromorpha, Crocopoda, Archosauriformes, Eucrocopoda, Crurotarsi, Archosauria?, Pseudosuchia?, Phytosauria, Parasuchidae, Mystriosuchinae 

Referred Species: R. carolinensis, R. manhattanensis 

Status: Extinct 

Time and Place: Sometime between 227 and 208.5 million years ago, in the Norian of the Late Triassic

Rutiodon is primarily known from the Eastern United States; there are reports from Canada, as well, but these are more dubious. All reports from the Chinle Formation that were once assigned to Rutiodon have since been given their own names. It is known from the Blue Bell Quarry and the New Oxford Formation of Pennsylvania, the Cumnock and Pekin Formations of North Carolina, and the Ewing Creek Member of the Lockatong Formation and the Passaic Formation of New Jersey.

Physical Description: Rutiodon was a Phytosaur, so naturally it looked ridiculously similar to modern crocodilians - and wasn’t one in the slightest. In fact, Phytosaurs and Crocodilians have a major difference - they had their nostrils far back on the head, close to the eyes, rather than on the tip of the snout. Rutiodon itself was very long, between 3 and 8 meters in body length, making it one of the largest animals in its environment. It had a very long, narrow jaw, with large teeth inside that grew much bigger at the front of the jaw. Weirdly enough, it was covered in armored plates like modern crocodilians on its back, sides, and tail, though this is a clear-cut case of convergent evolution - Crocodilians evolved from completely different Triassic reptiles. Rutiodon had a long tail, a squat body, and legs splayed out to the sides, just enhancing how much it resembled living crocodilians. 

Diet: Rutiodon would have fed on small animals and fish in its environment, using the hook in its jaw as well as the large teeth to grab onto struggling prey and hold it steady.

Behavior: Despite its uncanny resemblance to living crocodilians, it is difficult to determine whether or not Phytosaurs such as Rutiodon would have actually behaved like them. While being an ambush predator in the water it called home makes a certain amount of sense, that sense is primarily based on its resemblance to living analogues. That said, it’s also possible that the extreme length of its mouth would have aided Rutiodon in reaching and grabbing food that would be out of reach for a more snort-shouted animal (such as the large predatory amphibians that it shared a home with). It probably would have taken care of its young, though if it was more social than that it would have been more out of convenience than anything else. That said, Rutiodon seems to have been quite common, so groups of “I guess we’re all in this place together” may have been very common and a large annoyance to animals in the area trying to move through unscathed. 

Ecosystem: In general, Rutiodon lived in lake environments, usually near forests with decent amounts of water present beyond the lake. Flooding and swamp-like conditions were probably favored by this genus, based on its fossil neighbors. It was found in lakes, river deltas, and floodplains that would frequently turn into extremely overflowed swamps. In the Cumnock Environment of North Carolina, it lived alongside the large amphibian Dictyocephalus, as well as therapsids like Dromatherium and Microconodon and a variety of fish and unnamed reptiles. In the New Oxford Formation of Pennsylvania, it lived alongside another large amphibian - Koskinodon - as well as the fish Synorichthys, and potentially other Phytosaurs like Suchoprion and Palaeoctonus. Finally, in Lockatong, it lived with the Tanystropheid Tanytrachelos, the Kuehneosaurid Icarosaurus, the Protorosaur Hypuronector, the Rhynchosaurid Rhynchosauroides, unnamed dinosaurs, another Metoposaurid, and a variety of fish like Diplurus, Synorichthys, Turseodus, and Osteopleurus. All that fish would have made an excellent source of food for Rutiodon, along with those small Therapsids! 

Other: Phytosaurs like Rutiodon are a fun group of creatures that actually come in a wide variety of shapes and sizes, and aren’t all so similar to Crocodilians - they had weaker ankyls, no bony structure in the mouth to aid in breathing while underwater (though they may have had a fleshy one), and they actually had even more armor than crocodilians. That said, there is a chance Rutiodon and relatives are… stem-Crocodilians. What this means is, that living Crocodilians are their closest modern relatives. This is a subject of hot debate - they’re either the earliest branching members of the Crocodile-Relative group, or they’re closely but equally related to all modern archosaurs (so, they’d be equally Crocodile - and equally bird!) More research on these animals are sure to reveal further insights into their place in the evolution of the ruling reptiles. 

~ By Meig Dickson

Sources Under the Cut

RUTIODON “Wrinkle tooth” Late Triassic 225-215 million years ago

Easily mistaken for a crocodile, Rutiodon was actually a phytosaur – a crocodile-like reptile from the Triassic. Phytosaurs had long, splay-legged bodies with tough, bony scales like crocs, but their nostrils were located in front of (or above!) their eyes, instead of on the tips of their snouts. And speaking of snouts – Rutiodon's snout was very, very narrow, to best reflect its outlook on the world and social issues.