Isisfordia duncani (Salisbury et al., 2006; QM F36211; 1.1m, 3.6 feet long; Middle Cretaceous (Albian–Cenomanian) is the most primitive taxon basal to all living crocodilians.

The vertebrae fit together as they do in modern crocodilians (oose ball-and-socket joints), and a secondary palate similar to that in living crocodilians.

From the abstract: Members of Eusuchia do not appear until the Cretaceous. Eusuchia includes the crown group Crocodylia, which comprises Crocodyloidea, Alligatoroidea and Gavialoidea.

Tomistoma schlegelii (Müller 1838; Oligocene to present) is theextant false gharial, a sister to Crocodylus (above) in the LRT. Not a sister to Gavialis, depite the convergence.

Crocodylus niloticus As everyone knows, the crocodile has a narrower snout and the dentary teeth are visible when the mouth is closed. Note the very long retroarticular process. In caimans the dentary teeth show and the skull is midway between wide and narrow. An analysis by Brochu (1999) nested caimans as sisters to alligators with one unambiguous synapomorphy: the dermal bones of the skull roof overhang the rim of the upper temporal fenestrae, but only near maturity.

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 Isisfordia (above), these aquatic archosaurs have shifted the internal nares to the rear of the pterygoid (those two little conjoined dots in the posterior palate), enabling breathing while eating.

Sebecus icaeorhinus (Simpson 1937, Pol et al. 2012, Eocene) 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 in the large reptile tree it nests more closely to living crocs.

Deinosuchus riograndensis (TMM 43620-1 Deinosuchus hatcheri Holland 1909 CM963; Late Cretaceous; approaching 10m in length) is a coatal giant of North America is derived from earlier forms, close to the more terrestrial taxon, Sebecus, in the LRT. Premaxillary fenestrae are found on the anterior dorsally expanded premaxilla. The confluent nares open dorsoposteriorly along the parasagittal plane. Note the lateral view does not quite match the dorsal view with regard to the anterior extend of the quadratojugal.

Brochu CA 1999. Phylogenetics, Taxonomy, and Historical Biogeography of Alligatoroidea. Society of Vertebrate Paleontology Memoir 6: 9–100.

Brochu CA and Storrs GW 2012. A giant crocodile from the Plio-Pleistocene of Kenya, the phylogenetic relationships of Neogene African crocodylines, and the antiquity of Crocodylusin Africa. Journal of Vertebrate Paleontology 32: 587-602.

Cossette AP and CA Brochu 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. DOI: 10.1080/02724634.2020.1767638.

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.

Farmer CG and Sanders K 2010. Unidirectional Airflow in the Lungs of Alligators. Science 327 (5963):338–340.

Holland WJ 1909. Deinosuchus hatcheri, a new genus and species of crocodile
from the Judith River Beds of Montana. Annals of the Carnegie Museum 6:281–294.

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.

Müller S 1838. Waarnemingen over de Indische Krokodillen en Beschrijving van eene nieuwe Soort". Tijdschrift voor Natuurlijke Geschiedenis en Physiologie (in Dutch). 5: 61–87.

Pol D, Leardi JM, Lecuona A and Krause M 2012. Postcranial anatomy of Sebecus icaeorhinus (Crocodyliformes, Sebecidae) from the Eocene of Patagonia. Journal of Vertebrate Paleontology 32 (2): 328–354.

Salisbur SWY, Molnar RE, Frey E and Willis PMA 2006. The origin of modern crocodyliforms: new evidence from the Cretaceous of Australia. Proceedings of the Royal Society B 273:2439-2448

Simpson GG 1937. An ancient eusuchian crocodile from Patagonia. American Museum Noviates 965: 19–20.

wiki/Crocodylus
wiki/Alligator
wiki/American_alligator
wiki/Caiman
wiki/Isisfordia
wiki/Sebecus
wiki/Tomistoma
wiki/Deinosuchus