Caiman wannlangstoni

Caiman wannlangstoni Temporal range: Late Middle Miocene, 13–6 Ma PreЄ Є O S D C P T J K Pg N
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Superorder:	Crocodylomorpha
Order:	Crocodilia
Family:	Alligatoridae
Genus:	Caiman
Species:	†Caiman wannlangstoni Salas-Gismondi et al., 2015

Caiman wannlangstoni is an extinct species of caiman that lived in Amazonia during the Middle and Late Miocene. Fossils of C. wannlangstoni have been found in the Pebas and Urumaco Formations near Iquitos in Peru and include partial skulls and isolated skull bones. The species was first described in 2015 and the name honors Wann Langston, Jr., a paleontologist who studied South American fossil crocodylians for many decades. Features that in combination distinguish C. wannlangstoni from other caimans include a deep snout, a wavy upper jaw margin, a large and upward-directed narial opening (hole for the nostrils), and blunt teeth at the back of the jaws. Based on the sizes of the skulls, its estimated body length is about 211 to 227 centimetres (6.92 to 7.45 ft).^[1]

C. wannlangstoni lived through a major climatic and ecological shift in South America during the Middle to Late Miocene. The oldest fossils of the species come from the Pebas Formation, which was deposited during the Middle Miocene about 13 million years ago (Ma) over a vast area of Amazonia called the Pebas mega-wetland. The Pebas mega-wetland developed at the start of the Neogene, coincident with the main phase of uplift of the Andes Mountains and the formation of a massive (>1 million square kilometers) drainage basin that extended from the Andes to the Caribbean Sea. During this time C. wannlangstoni would have inhabited oxygen-poor marshes and swamps, feeding on thick-shelled molluscs alongside other caiman species with crushing dentitions like Gnatusuchus pebasensis and Kuttanacaiman iquitosensis. Beginning around 10.5 Ma, continued uplift of the Andes separated the Pebas region into three smaller basins: the Magdalena, Orinoco and Amazon basins. The youngest remains of C. wannlangstoni come from the Urumaco Formation, which was deposited during the Late Miocene around 6 to 9 Ma^[2] in the early Orinoco basin. At this time C. wannlangstoni would have lived in more energetic and oxygen-rich river environments. It occurs alongside several other caiman species, including Caiman brevirostris and Globidentosuchus brachyrostris, that also had crushing dentition.^[3] This assemblage of crushing-dentition caimans is similar to the earlier caiman assemblage from the Pebas Formation, but is not found in either the Magdalena or Amazon basins during the Late Miocene, suggesting that the Orinoco basin could have been the last refuge for these types of caimans before they became extinct.^[1]

The phylogenetic position of C. wannlangstoni with respect to other caimans is interesting in that it is more derived than other crushing-dentition caimans like Gnatusuchus, Globidentosuchus, and Kuttanacaiman, which seem to be the most basal members of the group. Therefore, a crushing dentition was likely present in the ancestors of caimans but later lost, and then was reacquired C. wannlangstoni. Below is a cladogram showing this pattern, with crushing-dentition caimans in bold:^[1]

Globidonta

Alligatorinae †Albertochampsa †Brachychampsa †Stangerochampsa Caimaninae (caimans) †Gnatusuchus pebasensis †Globidentosuchus brachyrostris †Eocaiman cavernensis †Kuttanacaiman iquitosensis †Purussaurus spp. †Mourasuchus spp. †Tsoabichi greenriverensis †Necrosuchus ionensis Paleosuchus spp. Jacarea †Centenariosuchus gilmorei Caiman crocodilus Caiman yacare †Caiman brevirostris Caiman latirostris †Caiman wannlangstoni †La Venta caiman †Melanosuchus fisheri Melanosuchus niger

References

1. Salas-Gismondi, R.; Flynn, J. J.; Baby, P.; Tejada-Lara, J. V.; Wesselingh, F. P.; Antoine, P. -O. (2015). "A Miocene hyperdiverse crocodylian community reveals peculiar trophic dynamics in proto-Amazonian mega-wetlands". Proceedings of the Royal Society B: Biological Sciences 282 (1804): 20142490. doi:10.1098/rspb.2014.2490.
2. Kay, R. F.; Cozzuol, M. A. (2006). "New platyrrhine monkeys from the Solimões Formation (late Miocene, Acre State, Brazil)". Journal of Human Evolution 50 (6): 673–86. doi:10.1016/j.jhevol.2006.01.002. PMID 16530809.
3. Scheyer, T. M.; Aguilera, O. A.; Delfino, M.; Fortier, D. C.; Carlini, A. A.; Sánchez, R.; Carrillo-Briceño, J. D.; Quiroz, L.; Sánchez-Villagra, M. R. (2013). "Crocodylian diversity peak and extinction in the late Cenozoic of the northern Neotropics". Nature Communications 4: 1907. doi:10.1038/ncomms2940. PMID 23695701.