| Acherontisuchus | |
|---|---|
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Family: | † Dyrosauridae |
| Genus: | † Acherontisuchus Hastings et al., 2011 |
| Type species | |
| †A. guajiraensis Hastings et al., 2011 | |
Acherontisuchus is an extinct genus of dyrosaurid neosuchian from Middle to Late Paleocene deposits of Colombia. [1] The only known species is A. guajiraensis, whose name means "Acheron crocodile of the Guajira Peninsula". [2]
Acherontisuchus is known from six specimens UF/IGM 34 through 39 (Hastings et al. 2011 noted these six specimens may represent only a single animal), including three partial lower jawbones, four fragments of the upper jaw, fragments of 21 teeth, two ribs, one upper backbone segment, one sacral vertebra (a bone that connects the hips to the rest of the spine), ribs that attach to the sacral vertebrae, a partial hip including the ilium and ischium bones, an upper leg bone, and one metatarsal foot bone. All Acherontisuchus specimens were collected from the Cerrejón Formation within the Cerrejón coal mine of northeastern Colombia and described in 2011 in Palaeontology journal by Alexander K. Hastings, Jonathan Bloch and Carlos A. Jaramillo. It is named after the river Acheron, which in Greek mythology was a branch of the river Styx meaning "river of woe" (Acherontisuchus is thought to have lived in a large river that emptied out into the Caribbean Sea during the Paleocene). The type species A. guajiraensis is named after Guajira Peninsula where Cerrejón is located. [2]
Acherontisuchus is found in multiple layers between coal seams, giving it a wide time distribution throughout the formation. Another dyrosaurid called Cerrejonisuchus was named from Cerrejón in 2010, but is only found in one layer of the formation. Aside from the consistently fractured fossils, no evidence exists of an altered fossil size. [2]
Acherontisuchus is considered a long-snouted, or longirostrine, dyrosaurid. Its snout is shorter than those of Dyrosaurus , Atlantosuchus , Rhabdognathus , and Congosaurus . Some of its teeth have pronounced grooves on both sides. The upper jaw is wide rather than high. Its head is estimated to have been 72–86 centimetres (28–34 in) long, about midsize for a dyrosaurid. It grew to a relatively large size compared to most dyrosaurids, between 4.66 and 6.46 metres (15.3 and 21.2 ft). [2]
Acherontisuchus lived in a calm, shallow, inland freshwater habitat in the tropical rainforests of northeastern Colombia, where its distant cousin Cerrejonisuchus lived as well. Most dyrosaurids, including the ancestors of Acherontisuchus, were well adapted to a coastal marine lifestyle. Like living crocodilians, these dyrosaurids were able to control their pitch and buoyancy in the water by contracting muscles that run between the abdomen and the hip. A projection of bone in the back of the hip called the ischial shaft serves as an anchor for the muscles that control pitch. Acherontisuchus has a slender ischial shaft, suggesting that the muscles that controlled its position in water were less developed. Oceanic dyrosaurids evolved an advanced system of pitch correction as an adaptation to rough ocean currents. Since Acherontisuchus lived in a shallow freshwater environment, it had less need to control its position. [2]
Based on the shape of its ribs and limb bones, Acherontisuchus probably had strong muscles along its back and in its legs that enabled movement on land. It probably lived in rivers that were present far from the ocean. In these inland rivers, Acherontisuchus most likely fed on lungfishes and eels. [2]
Acherontisuchus is closely related dyrosaurids from both Africa and the Americas. The phylogenetic analysis conducted with its first description placed Acherontisuchus in a derived clade of dyrosaurids that included Hyposaurus of North America, Congosaurus , Atlantosuchus , and Rhabdognathus of Africa, and Guarinisuchus of South America. The relationships between these dyrosaurids were not resolved, as Acherontisuchus was placed in a polytomy with Hyposaurus, Congosaurus, and a group containing the other close relatives. Acherontisuchus has several primitive features that distance it from other members of the derived dyrosaurid clade, including uniformly-spaced teeth and a wide connection between the two halves of the lower jaw. Below is a cladogram showing the phylogenetic relationships of Acherontisuchus and the distributions of dyrosaurids: [2]
| Neosuchia |
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Champsosaurus is an extinct genus of crocodile-like choristodere reptile, known from the Late Cretaceous and early Paleogene periods of North America and Europe (Campanian-Paleocene). The name Champsosaurus is thought to come from champsai, (χαμψαι) said in an Ancient Greek source to be an Egyptian word for "crocodiles", and sauros,(σαύρος) Greek for "lizard". The morphology of Champsosaurus resembles that of gharials, with a long, elongated snout. It was native to freshwater environments where it likely preyed on fish, similar to living gharials.
Prestosuchus is an extinct genus of pseudosuchian in the group Loricata, which also includes Saurosuchus and Postosuchus. It has historically been referred to as a "rauisuchian", and was the defining member of the family Prestosuchidae, though the validity of both of these groups is questionable: Rauisuchia is now considered paraphyletic and Prestosuchidae is polyphyletic in its widest form.
Chenanisuchus is a genus of dyrosaurid crocodyliform from the Late Cretaceous of Mali and the Late Palaeocene of Sidi Chenane in Morocco. It was described in 2005, after expeditions uncovered it in 2000.
Dyrosauridae is a family of extinct neosuchian crocodyliforms that lived from the Late Cretaceous (Maastrichtian) to the Eocene. Dyrosaurid fossils are globally distributed, having been found in Africa, Asia, Europe, North America and South America. Over a dozen species are currently known, varying greatly in overall size and cranial shape. A majority were aquatic, some terrestrial and others fully marine, with species inhabiting both freshwater and marine environments. Ocean-dwelling dyrosaurids were among the few marine reptiles to survive the Cretaceous–Paleogene extinction event.
Hyposaurus is a genus of extinct marine dyrosaurid crocodyliform. Fossils have been found in Paleocene aged rocks of the Iullemmeden Basin in West Africa, Campanian–Maastrichtian Shendi Formation of Sudan and Maastrichtian through Danian strata in New Jersey, Alabama and South Carolina. Isolated teeth comparable to Hyposaurus have also been found in Thanetian strata of Virginia. It was related to Dyrosaurus. The priority of the species H. rogersii has been debated, however there is no sound basis for the recognition of more than one species from North America. The other North American species are therefore considered nomina vanum.
Titanoboa is an extinct genus of very large snakes that lived in what is now La Guajira in northeastern Colombia. They could grow up to 12.8 m (42 ft) long and reach a weight of 1,135 kg (2,500 lb).
The Peligran age is a period of geologic time within the Paleocene epoch of the Paleogene, used more specifically with South American land mammal ages (SALMA). It follows the Tiupampan and precedes the Riochican age.
The Itaboraian age is a period within the Early Eocene geologic time epoch of the Paleogene, used more specifically with South American land mammal ages (SALMA). It follows the Riochican and precedes the Casamayoran age.
Congosaurus is an extinct genus of dyrosaurid mesoeucrocodylian. Fossils have been found from Lândana, in Angola and date back to the Paleocene epoch. In 1952 and 1964 Congosaurus was proposed to be synonymous with Dyrosaurus. The genus was later thought synonymous with Hyposaurus in 1976 and 1980. It has since been proven a distinct genus of dyrosaurid separate from both Dyrosaurus and Hyposaurus.
Phosphatosaurus is an extinct genus of dyrosaurid crocodylomorph. It existed during the early Eocene, with fossils having been found from North Africa in Tunisia and Mali. Named in 1955, Phosphatosaurus is a monotypic genus; the type species is P. gavialoides. A specimen has been discovered from Niger, but it cannot be classified at the species level.
Cerrejonisuchus is an extinct genus of dyrosaurid crocodylomorph. It is known from a complete skull and mandible from the Cerrejón Formation in northeastern Colombia, which is Paleocene in age. Specimens belonging to Cerrejonisuchus and to several other dyrosaurids have been found from the Cerrejón open-pit coal mine in La Guajira. The length of the rostrum is only 54-59% of the total length of the skull, making the snout of Cerrejonisuchus the shortest of all dyrosaurids.
The Cerrejón Formation is a geologic formation in Colombia dating back to the Middle-Late Paleocene. It is found in the El Cerrejón sub-basin of the Cesar-Ranchería Basin of La Guajira and Cesar. The formation consists of bituminous coal fields that are an important economic resource. Coal from the Cerrejón Formation is mined extensively from the Cerrejón open-pit coal mine, one of the largest in the world. The formation also bears fossils that are the earliest record of Neotropical rainforests.
Rhabdognathus is an extinct genus of dyrosaurid crocodylomorph. It is known from rocks dating to the Paleocene epoch from western Africa, and specimens dating back to the Maastrichtian era were identified in 2008. It was named by Swinton in 1930 for a lower jaw fragment from Nigeria. The type species is Rhabdognathus rarus. Stéphane Jouve subsequently assessed R. rarus as indeterminate at the species level, but not at the genus level, and thus dubious. Two skulls which were assigned to the genus Rhabdognathus but which could not be shown to be identical to R. rarus were given new species: R. aslerensis and R. keiniensis, both from Mali. The genus formerly contained the species Rhabdognathus compressus, which was reassigned to Congosaurus compressus after analysis of the lower jaw of a specimen found that it was more similar to that of the species Congosaurus bequaerti. Rhabdognathus is believed to be the closest relative to the extinct Atlantosuchus.
Sokotosuchus is an extinct genus of dyrosaurid crocodyliform which existed during the Maastrichtian in western Africa. Fossils of the genus were found in the Dukamaje Formation of Nigeria.
Cerrejonemys wayuunaiki is an extinct podocnemid turtle which existed in Colombia during the Paleogene period; the Middle to Late Paleocene epoch.
Montrichardia aquatica is an extinct species of monocot plant in the family Araceae. M. aquatica is related to the living species M. arborescens and M. linifera. The species is solely known from the Middle to Late Paleocene, fossil-rich Cerrejón Formation in La Guajira, northern Colombia.
Anthracosuchus is an extinct genus of dyrosaurid crocodyliform from the Paleocene of Colombia. Remains of Anthracosuchus balrogus, the only known species, come from the Cerrejón Formation in the Cerrejón mine, and include four fossil specimens with partial skulls. Anthracosuchus differs from other dyrosaurids in having an extremely short (brevirostrine) snout, widely spaced eye sockets with bony protuberances around them, and osteoderms that are smooth and thick. It is one of the most basal dyrosaurids along with Chenanisuchus and Cerrejonisuchus.
Hilarcotherium is an extinct genus of astrapotheriid mammals that lived in South America during the Middle Miocene (Laventan). The type species is H. castanedaii, found in sediments of the La Victoria Formation, part of the Honda Group in the department of Tolima in Colombia. In 2018, Carrillo et al. described a partial skull and mandible of a second species H. miyou from the Castilletes Formation in the Cocinetas Basin of northern Colombia, and estimated the body weight of the animal at 6,465 kilograms (14,253 lb).
The Cesar-Ranchería Basin is a sedimentary basin in northeastern Colombia. It is located in the southern part of the department of La Guajira and northeastern portion of Cesar. The basin is bound by the Oca Fault in the northeast and the Bucaramanga-Santa Marta Fault in the west. The mountain ranges Sierra Nevada de Santa Marta and the Serranía del Perijá enclose the narrow triangular intermontane basin, that covers an area of 11,668 square kilometres (4,505 sq mi). The Cesar and Ranchería Rivers flow through the basin, bearing their names.
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