| Caiman wannlangstoni | |
|---|---|
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| Size compared to a human. | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Archosauria |
| Order: | Crocodilia |
| Family: | Alligatoridae |
| Subfamily: | Caimaninae |
| Clade: | Jacarea |
| Genus: | Caiman |
| Species: | †C. wannlangstoni |
| Binomial name | |
| †Caiman wannlangstoni Salas-Gismondiet al.,2015 | |
Caiman wannlangstoni is an extinct species ofcaiman that lived in what is now theAmazon Basin and surrounding areas during theMiddle andLate Miocene. Fossils ofC. wannlangstoni have been found in thePebas Formation nearIquitos in Peru and include partial skulls and isolated skull bones. Other fossils were uncovered from theUrumaco Formation inVenezuela and theLaventanHonda Group ofColombia.[2] The species was first described in 2015. Features that in combination distinguishC. wannlangstoni from other caimans include a deep snout, a wavy upper jaw margin, a large and upward-directednarial 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).[3]
The species namewannlangstoni is named in honor of American paleontologistWann Langston Jr. for his contributions to the study of South American fossil crocodilians.[3]
Caiman wannlangstoni was described in 2015 by Rodolfo Salas-Gismondiet al on the basis a well preserved partial skull (MUSM 2377) that had been collected from the lateMiddle Miocene strata of thePebas Formation in “Locality IQ26” inIquitos,Peru.[3] 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 toCaiman lutescens[4] from theLate MioceneUrumaco Formation inVenezuela was also referred to the species by Salas-Gismondi et al., extending the species’ range into more of Proto-Amazonia.[5][3] A partial skull from theLa Venta Formation ofColombia may be from C. lanngstoni, but it lacks some diagnostic features of the species.[5][3]
Thephylogenetic position ofC. wannlangstoni with respect to other caimans is interesting in that it is morederived than other crushing-dentition caimans likeGnatusuchus,Globidentosuchus, andKuttanacaiman, which seem to be the mostbasal members of the group. Therefore, a crushing dentition was likely present in the ancestors of caimans but later lost, and then was reacquiredC. wannlangstoni. Below is acladogram showing this pattern, with crushing-dentition caimans in bold:[3]
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Caiman wannlangstoni was a small-medium-sizedCaiman species, with estimates placing it from 210.5 – 226.7 cm long. The most distinctive feature ofC. wannlangstoni is its high and robustrostrum, which has very largenasal 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 inC. latirostris andMelanosuchus niger.Kuttanacaiman iquitosensis has a very similar skull anatomy toC. wannlangstoni, butC. wannlangstoni differs in the anatomy of its orbitals and mandibles. The overall skull anatomy ofC. wannlangstoni is very similar to that ofC. brevirostris from Brazil, but the latter has a shorter and parallel-sided rostrum thanC. wannlangstoni,[6] among other distinguishing traits.[3][5]
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 theNeogene, coincident with the main phase of uplift of theAndes Mountains and the formation of a massive (>1 million square kilometers)drainage basin that extended from the Andes to theCaribbean Sea. During this timeC. wannlangstoni would have inhabited oxygen-poor marshes and swamps, feeding on thick-shelled molluscs alongside other caiman species with crushing dentitions likeGnatusuchus pebasensis andKuttanacaiman iquitosensis. Beginning around 10.5 Ma, continued uplift of the Andes separated the Pebas region into three smaller basins: theMagdalena,Orinoco andAmazon basins. The youngest remains ofC. wannlangstoni come from the Urumaco Formation, which was deposited during the Late Miocene around 6 to 9 Ma[7] in the early Orinoco basin. At this timeC. wannlangstoni would have lived in more energetic and oxygen-rich river environments. It occurs alongside several other caiman species, includingCaiman brevirostris andGlobidentosuchus brachyrostris, that also had crushing dentition.[8] 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 lastrefuge for these types of caimans before they became extinct.[3] The crusher caimans went extinct due to their extreme specializations and were replaced by generalist caimanine species, many of which exist today.[3]
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