Caiman Wannlangstoni

''Caiman wannlangstoni'' is an extinct species of caiman that lived in what is now the Amazon Basin and surrounding areas during the Middle and Late Miocene. Fossils of ''C. wannlangstoni'' have been found in the Pebas Formation near Iquitos in Peru and include partial skulls and isolated skull bones. Other fossils were uncovered from the Urumaco Formation in Venezuela and the Laventan Honda Group of Colombia.''Caiman wannlangstoni''
at Fossilworks.org The species was first described in 2015. 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 .

Etymology

The species name ''wannlangstoni'' is named in honor of American paleontologist Wann Langston Jr. for his contributions to the study of South American fossil crocodilians.

Discovery and taxonomy

''Caiman wannlangstoni'' was described in 2015 by Rodolfo Salas-Gismondi ''et al'' on the basis a well preserved partial skull ( MUSM 2377) that had been collected from the late Middle Miocene strata of the Pebas Formation in “Locality IQ26” in Iquitos, Peru. A second specimen was referred to the species from Iquitos, though it only included several associated skull and mandible elements. A specimen consisting of a right premaxilla and maxilla that was previously referred to ''Caiman lutescens'' from the Late Miocene Urumaco Formation in Venezuela was also referred to the species by Salas-Gismondi et al, extending the species’ range into more of Proto-Amazonia.Scheyer, T. M., & Delfino, M. (2016)
The late Miocene caimanine fauna (Crocodylia: alligatoroidea) of the Urumaco Formation, Venezuela.
''Palaeontologia Electronica'', ''19''(3), 1-57. A partial skull from the La Venta Formation of Colombia may be from  ''C. lanngstoni'', but it lacks some diagnostic features of the species.

Description

''Caiman wannlangstoni'' was a small-medium sized ''Caiman'' species, with estimates placing it from 210.5 – 226.7 cm long. The most distinctive feature of ''C. wannlangstoni'' is its high and robust rostrum, which has very large nasal openings and strong sinuous rostral margins. The species also has robust, large, and globular posterior teeth, built for "crushing" mollusks and hard shelled prey. The skull is roughly triangular in dorsal view with large, oval orbits. The posterior margin of skull table is semicircular and overhangs the occipital plate, resembling the skull tables in '' C. latirostris'' and '' Melanosuchus niger''. ''Kuttanacaiman iquitosensis'' has a very similar skull anatomy to ''C. wannlangstoni'', but ''C. wannlangstoni'' differs in the anatomy of its orbitals and mandibles. The overall skull anatomy of ''C. wannlangstoni'' is very similar to that of ''C. brevirostris'' from Brazil, but the latter has a shorter and parallel-sided rostrum than ''C. wannlangstoni,'' among other distinguishing traits.

Classification

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:

Paleoenvironment

''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 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. 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. The crusher caimans went extinct due to their extreme specializations and were replaced by generalist caimanine species, many of which exist today.

References

{{Taxonbar, from=Q20080405

Alligatoridae
Miocene crocodylomorphs
Miocene reptiles of South America
Montehermosan
Huayquerian
Chasicoan
Mayoan
Laventan
Neogene Colombia
Fossils of Colombia
Neogene Peru
Fossils of Peru
Neogene Venezuela
Fossils of Venezuela
Fossil taxa described in 2015