Caiman wannlangstoni

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Caiman wannlangstoni
Temporal range: Mid-Late Miocene, 16–5.3  Ma [1]
Caiman wannlangstoni size.jpg
Size compared to a human.
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Clade: Archosauromorpha
Clade: Archosauriformes
Order: Crocodilia
Family: Alligatoridae
Subfamily: Caimaninae
Clade: Jacarea
Genus: Caiman
Species:
C. wannlangstoni
Binomial name
Caiman wannlangstoni
Salas-Gismondi et al., 2015

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. [2] 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 211 to 227 centimetres (6.92 to 7.45 ft). [3]

Contents

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. [3]

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. [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 to Caiman lutescens [4] 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. [5] [3] A partial skull from the La Venta Formation of Colombia may be from  C. lanngstoni, but it lacks some diagnostic features of the species. [5] [3]

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: [3]

Globidonta

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, [6] among other distinguishing traits. [3] [5]

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 [7] 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. [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 last refuge 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]

Related Research Articles

<i>Caiman</i> (genus) Genus of reptiles

Caiman is a genus of caimans within the alligatorid subfamily Caimaninae. They inhabit Central and South America. They are relatively small sized crocodilians, with all species reaching lengths of only a couple of meters and weighing 6 to 40 kg on average.

<i>Purussaurus</i> Extinct genus of reptiles

Purussaurus is an extinct genus of giant caiman that lived in South America during the Miocene epoch, from the Friasian to the Huayquerian in the SALMA classification. It is known from skull material found in the Brazilian and Peruvian Amazon, Colombian Villavieja Formation, Panamanian Culebra Formation, Urumaco and Socorro Formations of northern Venezuela.

<i>Mourasuchus</i> Extinct genus of reptiles

Mourasuchus is an extinct genus of giant, aberrant caiman from the Miocene of South America. Its skull has been described as duck-like, being broad, flat, and very elongate, superficially resembling Stomatosuchus from the Late Cretaceous.

<span class="mw-page-title-main">Caiman</span> Subfamily of reptiles

A caiman is an alligatorid belonging to the subfamily Caimaninae, one of two primary lineages within the Alligatoridae family, the other being alligators. Caimans are native to Central and South America and inhabit marshes, swamps, lakes, and mangrove rivers. They have scaly skin and live a fairly nocturnal existence. They are relatively small-sized crocodilians with an average maximum weight of 6 to 40 kg depending on species, with the exception of the black caiman, which can grow more than 4 m (13 ft) in length and weigh in excess of 1,000 kg. The black caiman is the largest caiman species in the world and is found in the slow-moving rivers and lakes that surround the Amazon basin. The smallest species is the Cuvier's dwarf caiman, which grows to 1.2 to 1.5 m long. There are six different species of caiman found throughout the watery jungle habitats of Central and Southern America. The average length for most of the other caiman species is about 2 to 2.5 m long.

<i>Gryposuchus</i> Extinct genus of gavialoid crocodilian

Gryposuchus is an extinct genus of gavialid crocodilian. Fossils have been found from Argentina, Colombia, Venezuela, Brazil and the Peruvian Amazon. The genus existed during the Miocene epoch. One recently described species, G. croizati, grew to an estimated length of 10 metres (33 ft). Gryposuchus is the type genus of the subfamily Gryposuchinae, although a 2018 study indicates that Gryposuchinae and Gryposuchus might be paraphyletic and rather an evolutionary grade towards the gharial.

Hesperogavialis is an extinct genus of gryposuchine gavialid. Fossils have been found from Venezuela and Brazil that date back to the Middle to Late Miocene. Although Hesperogavialis is one of the best known gavialoids from South America, the posterior portion of the skull is still unknown, making any attempts at classification within the family somewhat more difficult than other gavialoids in which much of the skull is present. The genus possibly comprises three species. The type species, H. cruxenti, has been found in the Urumaco Formation in Venezuela. A second possible species, named H. bocquentini, has been described from the Solimões Formation in Acre, Brazil, and can be distinguished from H. cruxenti by the asymmetry seen in the anterior portion of the nasals and the small distance between alveoli. A third species can be recognized from the same locality in Acre, although a formal name has yet to be given to it.

Orthogenysuchus is an extinct genus of caimanine alligatorids. Fossils have been found from the Wasatch Beds of the Willwood Formation of Wyoming, deposited during the early Eocene. The type species is O. olseni. The holotype, known as AMNH 5178, is the only known specimen belonging to the genus and consists of a skull lacking the lower jaws. The braincase is filled in by the matrix and most of the suture lines between bones are indiscernible, making comparisons with other eusuchian material difficult.

<i>Tsoabichi</i> Extinct genus of reptiles

Tsoabichi is an extinct genus of caimanine crocodylian. Fossils are known from the Green River Formation in Wyoming, and date back to the Ypresian stage of the Eocene. The genus was named and described in 2010 by paleontologist Christopher A. Brochu, with the type species being Tsoabichi greenriverensis. According to the current understanding of caiman evolutionary relationships, Tsoabichi is a basal member of Caimaninae and may have evolved after caimans dispersed into North America from northern and central South America, their main center of diversity in the Cenozoic.

Gryposuchinae is an extinct subfamily of gavialid crocodylians. Gryposuchines lived mainly in the Miocene of South America. However, "Ikanogavialis" papuensis may have survived more recently, into the Late Pleistocene/Holocene. Most were long-snouted coastal forms. The group was named in 2007 and includes genera such as Gryposuchus and Aktiogavialis, although a 2018 study indicates that the group might be paraphyletic and rather an evolutionary grade towards the gharial.

Culebrasuchus is an extinct, monotypic genus of caiman alligatorid known from the Early to Middle Miocene (Hemingfordian) of the Panama Canal Zone of Panama. It contains a single species, Culebrasuchus mesoamericanus.

Globidentosuchus is an extinct genus of basal caimanine crocodylian known from the late Middle to Late Miocene of the Middle and the Upper Members of the Urumaco Formation at Urumaco, Venezuela. Its skull was very short and robust, with large units of spherical teeth used to break the shells of molluscs as part of its durophagus diet. It is thought to be one of the most basal Caimanines, even sharing some traits with alligatorids.

<span class="mw-page-title-main">Pebas Formation</span> Geological formation in Brazil, Colombia, Ecuador and Peru

The Pebas Formation is a lithostratigraphic unit of Miocene age, found in western Amazonia. The formation extends over 1,000,000 square kilometres (390,000 sq mi), including parts of Brazil, Peru, Ecuador and Colombia. It is interpreted as representing the deposits of a lake or series of lakes, formed within the foreland basin of the Andes mountain belt. It is known for its abundant fossil ostracods and molluscs and an unusually diverse group of crocodylians.

<i>Kuttanacaiman</i> Extinct genus of reptiles

Kuttanacaiman is a monotypic genus of extinct caiman represented by the type species Kuttanacaiman iquitosensis. Kuttanacaiman lived in what is now the Amazon basin during the Middle Miocene, approximately 13 million years ago (Ma). The species was named in 2015 on the basis of one nearly complete skull and a second partial skull from the Pebas Formation near Iquitos, Peru. K. iquitosensis is characterized by a short, rounded snout and blunt teeth at the back of its jaws that were likely adapted to crushing freshwater bivalves. Its estimated total body length is 171.2 to 189.1 centimetres.

<i>Gnatusuchus</i> Extinct genus of reptiles

Gnatusuchus is an extinct genus of caiman represented by the type species Gnatusuchus pebasensis from the Middle Miocene Pebas Formation of Peru. Gnatusuchus lived about 13 million years ago (Ma) in a large wetland system called the Pebas mega-wetlands that covered over one million square kilometers of what is now the Amazon Basin.

The Urumaco Formation is a formation in Venezuela that includes deposits from the Late Miocene. It is the site of several "giant forms": the turtles, crocodiles, sloths and rodents of Urumaco are among the largest of their groups.

Bairdemys is an extinct genus of side-necked turtles in the family Podocnemididae. The genus existed from the Late Oligocene to Late Miocene and its fossils have been found in South Carolina, Puerto Rico, Panama and Venezuela. The genus was described in 2002 by Gaffney & Wood and the type species is B. hartsteini.

Caiman brevirostris is an extinct species of caiman that lived during the Late Miocene, around 11.6 million years ago, to the end of the Miocene 5.3 million years ago in Acre and Amazonas, Brazil as well as Urumaco, Venezuela. Several specimens have been referred to the species, but only 3 of them are confidently placed in the species. C. brevirostris was originally named in 1987 on the basis of a single, incomplete rostrum with an associated mandibular ramus that had been found in Acre, Brazil. C. brevirostris is very distinct among Caiman species and caimaninae overall in that it preserves a characteristically short and robust skull that bears blunt posterior teeth that were built to break down harder foods. This was an adaption for durophagy, likely to crush shells of mollusks and clams which were common in the wetlands that C. brevirostris resided in.

Acresuchus is an extinct monospecific genus of medium-sized caiman from the Late Miocene of western Brazil and Venezuela. The genus contains a single species, Acresuchus pachytemporalis. Acresuchus is a close relative of the giant caiman Purussaurus.

<i>Pseudoprepotherium</i> Extinct genus of ground sloths

Pseudoprepotherium is an extinct genus of sloths of the family Mylodontidae. It was widespread across northern South America during the Early to Late Miocene epoch around 21 to 5.3 million years ago. Fossils of the animal have been found in Brazil, Venezuela, and Peru. Pseudoprepotherium lived in a tropical climate with a water-rich environment. Their known remains are limited to limb bones, except for a few skulls and teeth. Based on these remains, they were most likely medium to large-sized mylodontid. The genus was described in 1961 and currently contains three species, which were originally assigned to the genus Prepotherium.

Sacacosuchus is an extinct monospecific genus of marine gavialid that lived along the coast of the south-east Pacific from approximately 19 to 6.3 million years ago. Its fossils have been found in the Chilcatay and Pisco Formations of Peru, where it coexisted with the much larger Piscogavialis. Based on its skull, Sacacosuchus was most likely a generalist feeder with an estimated total body length of 4.32 m (14.2 ft). Its extinction is thought to have been caused by a combination of factors including falling sea levels and global cooling.

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