Tsoabichi

Last updated

Tsoabichi
Temporal range: Eocene: Ypresian, 56–47.8  Ma [1]
Tsoabichi greenriverensis cast Catalog number FOBU801.jpg
Tsoabichi greenriverensis cast at Fossil Butte National Monument, Lincoln County, Wyoming
Scientific classification Red Pencil Icon.png
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Crocodilia
Family: Alligatoridae
Subfamily: Caimaninae
Genus: Tsoabichi
Brochu, 2010
Type species
Tsoabichi greenriverensis
Brochu, 2010

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 (Wasatchian stage of North American age). The genus was named and described in 2010 by paleontologist Christopher A. Brochu, with the type species being Tsoabichi greenriverensis. [2] 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. [3]

Contents

Description

Some living caimans such as the Spectacled Caiman have a "spectacle", or a bony ridge between the eyes. Tsoabichi lacks a spectacle, but it does have three smaller ridges between the orbits, or eye sockets. In Tsoabichi, distinct rims are seen around the supratemporal fenestrae, two holes on the skull table. Much of the supraoccipital bone is also found on the skull table, and forms a V-shape. To either side of the V-shaped supraoccipitals are the parietal bones, which form the posterior margin of the skull table. Along the snout, the nasal bone forms a thin ridge, and narrows as it approaches the external naris where the nostrils are located. [2]

The dorsal osteoderms (bony scutes along the back) are wider than those of other caimans. Some have two keels on their outer surface. Tsoabichi also has bipartite ventral osteoderms on its underside. [2]

Phylogeny

Tsoabichi was included in a phylogenetic analysis when it was described in 2010. Brochu (2010) found it to be a basal member of Caimaninae closely related to the living genus Paleosuchus . [2] The analysis of Hastings et al. (2013), which included several more species of caimans, also placed Tsoabichi in a basal position within Caimaninae as the sister taxon to crown group caimans (the smallest clade that includes all living caimans and their most recent common ancestor). Eocaiman and Culebrasuchus were successively more basal than Tsoabichi, as shown in the cladogram below: [3]

Stangerochampsa mccabei

Brachychampsa montana

Brachychampsa sealeyi

  Alligatoridae  

Alligatorinae

  Caimaninae  

Culebrasuchus mesoamericanus

Eocaiman cavernensis

Tsoabichi greenriverensis

crown group   caimans

Paleosuchus palpebrosus Cuvier's dwarf caiman

Paleosuchus trigonatus Smooth-fronted caiman

Centenariosuchus gilmorei

Purussaurus neivensis

Mourasuchus

Orthogenysuchus olseni

Caiman crocodilus Spectacled caiman

Caiman yacare Yacare caiman

Caiman latirostris Broad-snouted caiman

Caiman lutescens

Melanosuchus fisheri

Melanosuchus niger Black caiman

Biogeography

Tsoabichi is one of the few caimanines known to have lived north of what is now Mexico; the majority of caimans living and extinct are known from Central and South America. Caimans are thought to have originated in North America in the Late Cretaceous, yet Tsoabichi most likely originated from a South American population that reentered North America in the Early Eocene. The route by which a population of caimans could have reached North America in the Early Eocene is unknown. A sea route is unlikely given that living caimans have low tolerance for salt water, yet North and South America were separated by a large expanse of ocean. A continuous land route would not appear until the Isthmus of Panama formed several tens of millions of years later in the Pliocene, and a potentially crossable island chain would not form until tectonic uplift between the two continents occurred in the Late Eocene. An alternative biogeographic explanation is that Tsoabichi descended from a population of ancestral caimans that never left North America, but this hypothesis is unlikely given that it would necessitate multiple independent dispersals into Central and South America (including one for Culebrasuchus, one for Eocaiman, one for Paleosuchus, and one for derived caimans). [3]

Related Research Articles

<span class="mw-page-title-main">Alligatoridae</span> Family of crocodilians including alligators, caimans and kin

The family Alligatoridae of crocodylians includes alligators, caimans and their extinct relatives.

<i>Melanosuchus</i> Genus of caiman

Melanosuchus is a genus of alligatorid caiman. The black caiman of South America is the sole extant (living) species, and is the largest living member of the subfamily caimaninae, and the entire alligator family.

<i>Trilophosuchus</i> Genus of crocodiles

Trilophosuchus is an extinct genus of mekosuchine crocodilian from Australia. Unlike living crocodilians, it is hypothesized to have been terrestrial. Trilophosuchus was approximately 1.5 metres (4.9 ft) in length. It had a short skull with three ridges on top and large eyes. Fossils have been found at Riversleigh in north-western Queensland, and are Miocene in age. Only a single species has been described, the type species T. rackhami.

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

Ceratosuchus is an extinct genus of alligatorine crocodylian from latest Paleocene rocks of Colorado's Piceance Basin and earliest Eocene rocks of Wyoming's Bighorn Basin in North America, a slice of time known as the Clarkforkian North American Land Mammal Age. Like its modern relatives, Ceratosuchus was a swamp-dwelling predator. It is named for the pair of flattened, triangular bony plates that extend from the back of its head.

Wannaganosuchus is an extinct genus of small alligatorid crocodylian. It was found in Late Paleocene-age rocks of Billings County, North Dakota, United States.

Procaimanoidea is an extinct genus of alligatorid from the Eocene of North America. It was named posthumously in 1946 by Charles W. Gilmore; the type species is P. utahensis, from the Uintan of Utah. It is based on USNM 15996, a nearly complete skull and partial left hind leg. A second species, P. kayi, was named in 1941 by C.C. Mook as a species of Hassiacosuchus, for remains from the Bridgerian of Wyoming. It was reassigned to Procaimanoidea in 1967 by Wassersug and Hecht.

<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 inhabit Mexico, Central and South America from marshes and swamps to mangrove rivers and lakes. 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>Necrosuchus</i> Extinct genus of reptiles

Necrosuchus is an extinct genus of caiman from modern day Argentina that lived during the Paleocene epoch. It inhabited the fluvio-lacustrine environment of the Patagonian Salamanca Formation.

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

Allognathosuchus is an extinct genus of alligatorine crocodylian with a complicated taxonomic history. It was named in 1921.

Arambourgia is an extinct monotypic genus of alligatorine crocodylian from Europe. It was named in 1905 as Allognathosuchus gaudryi. It was made a separate genus Arambourgia in 1940. This was synonymized with Allognathosuchus haupti in 1990, but later reassigned as its own genus once again in 2004. Arambourgia was likely to have been part of an early dispersal event of alligatorines from North America to Europe during the Eocene epoch. Arambourgia had non-serrated teeth and a deep orienirostral snout, unlike the flatter snouts of most other alligatorids.

Bottosaurus is an extinct genus of alligatorid from the Late Cretaceous-Early Paleocene of New Jersey, Texas, and possibly North Carolina and South Carolina. Two species are currently accepted, with a third requiring re-evaluation.

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

Fruitachampsa is a genus of shartegosuchid crocodyliform from the Upper Jurassic Morrison Formation of Colorado. It is known from multiple specimens that show it to have been a relatively long-limbed terrestrial quadrupedal predator less than 1 metre (3.3 ft) long, with a short face and a prominent pair of canine-like teeth in the lower jaw. Before it was formally described in 2011, it was also known as the "Fruita form". Its type species is F. callisoni.

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.

<span class="mw-page-title-main">Globidonta</span> Clade of reptiles

Globidonta is a clade of alligatoroids that includes alligators, caimans, and closely related extinct forms. It is defined as a stem-based clade including Alligator mississippiensis and all forms more closely related to it than to Diplocynodon. The group's fossil range extends back into the Late Cretaceous with early alligatoroids such as Albertochampsa and Brachychampsa. Extinct globidontans were particularly common in North America and Eurasia, and their modern range also includes South America.

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.

Centenariosuchus is an extinct genus of caimanine crocodylian known from the Miocene of the Panama Canal Zone of Panama. It contains a single species, Centenariosuchus gilmorei, that was named in 2013 in honor of the upcoming centennial anniversary of the digging of the Panama Canal. Two fossil specimens consisting of skull fragments were found in the Early to Middle Miocene Cucaracha Formation in 2009 and 2011, and may belong to a single individual. The species is diagnosed by a combination of skull features that it shares with basal caimans like Tsoabichi, Eocaiman, Culebrasuchus, and the living genus Paleosuchus, as well as more derived caimans such as those in the genus Caiman. One feature that distinguishes Centenariosuchus from all other caimans is the straight outer margin of a hole on the underside of the skull called the suborbital fenestra. According to one phylogenetic analysis of caimanine relationships, Centenariosuchus falls within a clade or evolutionary grouping of caimans that includes the very large and highly specialized forms Purussaurus and Mourasuchus, known from the Miocene of South America.

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">Planocraniidae</span> Extinct family of reptiles

Planocraniidae is an extinct family of eusuchian crocodyliforms known from the Paleogene of Asia, Europe and North America. The family was coined by Li in 1976, and contains three genera, Boverisuchus, Duerosuchus and Planocrania. Planocraniids were highly specialized crocodyliforms that were adapted to living on land. They had extensive body armor, long legs, and blunt claws resembling hooves, and are sometimes informally called "hoofed crocodiles".

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 andVenezuela. The genus contains a single species, Acresuchus pachytemporalis. Acresuchus is a close relative of the giant caiman Purussaurus.

References

  1. Rio, Jonathan P.; Mannion, Philip D. (6 September 2021). "Phylogenetic analysis of a new morphological dataset elucidates the evolutionary history of Crocodylia and resolves the long-standing gharial problem". PeerJ . 9: e12094. doi: 10.7717/peerj.12094 . PMC   8428266 . PMID   34567843.
  2. 1 2 3 4 Brochu, C.A. (2010). "A new alligatorid from the lower Eocene Green River Formation of Wyoming and the origin of caimans". Journal of Vertebrate Paleontology. 30 (4): 1109–1126. doi:10.1080/02724634.2010.483569. S2CID   129231903.
  3. 1 2 3 Hastings, A. K.; Bloch, J. I.; Jaramillo, C. A.; Rincon, A. F.; MacFadden, B. J. (2013). "Systematics and biogeography of crocodylians from the Miocene of Panama". Journal of Vertebrate Paleontology. 33 (2): 239. doi: 10.1080/02724634.2012.713814 . S2CID   83972694.