One is a large extant icon of Florida, famous for crossing golf courses. The other is a Cretaceous giant of coastal North America. Today Alligator (Fig. 1) and Deinosuchus (Fig. 2) enter the large reptile tree (LRT, 1936+ taxa; subset Fig. 3).
This started with an online NPR story (link below):
“There’s this concept out there that crocodylians are unchanging forms,” Brochu said. “That they appear way back in the distant past and haven’t changed since the days of the dinosaurs. That is simply not true.” Dr. Chris Brochu was a co-author on the paper: Cosette AP and Brochu CA 2020, a systematic review of Deinosuchus, which prompted the NPR story.
Alligator mississippiensis (Holbrook 1842; originally Crocodilius mississippiensis, Daudin 1802; up to 4.6m) is the American alligator. Derived (through a long chain of transitional taxa) from a sister to Middle Cretaceous Isisfordia (Fig. 4), these aquatic archosaurs have shifted the internal nares to the rear of the pterygoid enabling breathing while eating, like mammals.
(Colbert and Bird 1954, originally Phobosuchus riograndensis, TMM 43620-1), original genus: (Deinosuchus hatcheri (Holland 1909 CM963; Late Cretaceous; approaching 10m in length) is a coastal giant of North America. Premaxillary fenestrae are found on the anterior dorsally expanded premaxilla, as in Crocodylus niloticus, but not Alligator. The confluent nares open dorsoposteriorly along the parasagittal plane. Note the model lateral view does not quite match the fossil dorsal view with regard to the anterior extent of the quadratojugal.
The cladogram by Cosette and Brochu 2020
focused solely only the species surrounding Deinosuchus and do not extend to the base of the Crocodylomorpha and beyond. When you deal at the species level, like that, you may need more characters or you may not, but you will need more pertinent characters to separate taxa at the specimen and species level, while eliminating irrelevant characters and states.
In the LRT,
working at the generic level, 238 multi-state characters have, so far, done the job of separating one fish from another, one croc from another, etc. Calls for more characters in the LRT are not based on experience and fact, but on out-of-date hypotheses still found in university textbooks and lectures. Not sure why academics are adamant about adding traits and equally adamant about not adding taxa. That’s why the LRT experiment exists.
(Simpson 1937, Pol et al. 2012, Eocene; Fig. 5) is a land croc from South America. Like a theropod dinosaur, the teeth were laterally compressed and serrated. Sebecus was earlier nested with Baurusuchus, but now nests more closely to living crocs with conical teeth.
This hypothesis of interrelationships appears to be novel.
If there is a prior citation, please let me know so I can promote it here.
Cosette AP and Brochu CA 2020. A systematic review of the giant alligatoroid Deinosuchus from the Campanian of North America and its implications for the relationships at the root of Crocodylia. Journal of Vertebrate Paleontology 40(1):e1767638
Daudin FM 1801-2. Histoire Naturelle, Générale et Particulière des Reptiles; ouvrage faisant suit à l’Histoire naturell générale et particulière, composée par Leclerc de Buffon; et rédigee par C.S. Sonnini, membre de plusieurs sociétés savantes. Vol. 2. F. Dufart, Paris, 432 pp.
Hollbrook JE 1842. North American Herpetology; or, A description of the reptiles inhabiting the United States. Vol II (2nd ed.). J. Dobson, Philadelphia, 142 pp.
Simpson GG 1937. An ancient eusuchian crocodile from Patagonia. American Museum Noviates 965: 19–20.