Acherontisuchus
Encyclopedia
Acherontisuchus is an extinct genus
of dyrosaurid
neosuchia
n from Middle to Late Paleocene deposits of Colombia
. The only known species is A. guajiraensis, whose name means "Acheron
crocodile
of the Guajira Peninsula
".
/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 rib
s, 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.
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.
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 cm (28.3–33.9 in) long, about midsize for a dyrosaurid. It grew to a relatively large size compared to most dyrosaurids, between 4.66 and 6.46 m (15.3 and 21.2 ft).
freshwater
habitat in the tropical rainforest
s 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 current
s. Since Acherontisuchus lived in a shallow freshwater environment, it had less need to control its position.
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 lungfish
es and eel
s.
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:
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of dyrosaurid
Dyrosauridae
Dyrosauridae is a family of extinct neosuchian crocodyliforms that lived from the Late Cretaceous to the Eocene. Fossils of this group have been found in almost every continent, specifically Africa, Asia, Europe, North America and South America....
neosuchia
Neosuchia
Neosuchia is an unranked clade within Mesoeucrocodylia that includes all modern extant crocodilians and their closest fossil relatives. It is defined as the most inclusive clade containing all crocodylomorphs more closely related to Crocodylus niloticus than to Notosuchus terrestris...
n from Middle to Late Paleocene deposits of Colombia
Colombia
Colombia, officially the Republic of Colombia , is a unitary constitutional republic comprising thirty-two departments. The country is located in northwestern South America, bordered to the east by Venezuela and Brazil; to the south by Ecuador and Peru; to the north by the Caribbean Sea; to the...
. The only known species is A. guajiraensis, whose name means "Acheron
Acheron
The Acheron is a river located in the Epirus region of northwest Greece. It flows into the Ionian Sea in Ammoudia, near Parga.-In mythology:...
crocodile
Crocodile
A crocodile is any species belonging to the family Crocodylidae . The term can also be used more loosely to include all extant members of the order Crocodilia: i.e...
of the Guajira Peninsula
Guajira Peninsula
Guajira Peninsula , is a peninsula in northern Colombia and northwestern Venezuela in the Caribbean Sea...
".
Description
Acherontisuchus is known from six specimens UFUniversity of Florida
The University of Florida is an American public land-grant, sea-grant, and space-grant research university located on a campus in Gainesville, Florida. The university traces its historical origins to 1853, and has operated continuously on its present Gainesville campus since September 1906...
/IGM 34 through 39 (Hastings et al. 2011 noted these six specimens may represent only a single animal), including three partial lower jawbones
Mandible
The mandible pronunciation or inferior maxillary bone forms the lower jaw and holds the lower teeth in place...
, four fragments of the upper jaw
Maxillary
Maxillary means "related to the maxilla ". Terms containing "maxillary" include:*Maxillary artery*Maxillary nerve*Maxillary prominence*Maxillary sinus...
, fragments of 21 teeth, two rib
Rib
In vertebrate anatomy, ribs are the long curved bones which form the rib cage. In most vertebrates, ribs surround the chest, enabling the lungs to expand and thus facilitate breathing by expanding the chest cavity. They serve to protect the lungs, heart, and other internal organs of the thorax...
s, 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
Pelvis
In human anatomy, the pelvis is the lower part of the trunk, between the abdomen and the lower limbs .The pelvis includes several structures:...
including the ilium
Ilium
-Places:* Ilion or, Latinized, Ilium, another name for the legendary city of Troy, hence the title of Homer's Iliad*Ilium , an ancient city in Epirus...
and ischium bones, an upper leg bone
Femur
The femur , or thigh bone, is the most proximal bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs. In vertebrates with four legs such as dogs and horses, the femur is found only in...
, and one metatarsal foot bone. All Acherontisuchus specimens were collected from the Cerrejón Formation
Cerrejón Formation
The Cerrejón Formation is a geologic formation in Colombia dating back to the Middle-Late Paleocene. It is found in the El Cerrejón subbasin of the Racheria basin of La Guajira. The formation consists of bituminous coal fields that are an important economic resource. Coal from the Cerrejón...
within the Cerrejón
Cerrejón
Cerrejón is a coal mine located in the Guajira department in the north of Colombia. It is the largest mining operation in Colombia and among the largest open-pit coal mines in the world. The legal entity managing the Cerrejón operation is known as Carbones del Cerrejón Ltd...
coal mine of northeastern Colombia
Colombia
Colombia, officially the Republic of Colombia , is a unitary constitutional republic comprising thirty-two departments. The country is located in northwestern South America, bordered to the east by Venezuela and Brazil; to the south by Ecuador and Peru; to the north by the Caribbean Sea; to the...
and described in 2011
2011 in paleontology
-Lobopods:-Arachnids:-Insects:-Newly named jawless vertebrates:-Newly named acanthodian:-Newly named cartilaginous fishes:-Newly named bony fishes:-Newly named lepospondyls:-Newly named temnospondyls:-Newly named lissamphibians:...
in Palaeontology
Palaeontology (journal)
Palaeontology is one of the two scientific journals of the Palaeontological Association. It was established in 1957. It is published on behalf of the Association by Wiley-Blackwell. The editor-in-chief is David Batten. Palaeontology publishes articles on a range of palaeontological topics,...
journal by Alexander K. Hastings, Jonathan Bloch and Carlos A. Jaramillo. It is named after the river Acheron, which in Greek mythology
Greek mythology
Greek mythology is the body of myths and legends belonging to the ancient Greeks, concerning their gods and heroes, the nature of the world, and the origins and significance of their own cult and ritual practices. They were a part of religion in ancient Greece...
was a branch of the river Styx
Styx
In Greek mythology the Styx is the river that forms the boundary between the underworld and the world of the living, as well as a goddess and a nymph that represents the river.Styx may also refer to:-Popular culture:...
meaning "river of woe" (Acherontisuchus is thought to have lived in a large river that emptied out into the Caribbean Sea
Caribbean Sea
The Caribbean Sea is a sea of the Atlantic Ocean located in the tropics of the Western hemisphere. It is bounded by Mexico and Central America to the west and southwest, to the north by the Greater Antilles, and to the east by the Lesser Antilles....
during the Paleocene). The type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
A. guajiraensis is named after Guajira Peninsula
Guajira Peninsula
Guajira Peninsula , is a peninsula in northern Colombia and northwestern Venezuela in the Caribbean Sea...
where Cerrejón is located.
Acherontisuchus is found in multiple layers between coal seams, giving it a wide time distribution throughout the formation. Another dyrosaurid called Cerrejonisuchus
Cerrejonisuchus
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...
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.
Acherontisuchus is considered a long-snouted, or longirostrine, dyrosaurid. Its snout is shorter than those of Dyrosaurus
Dyrosaurus
Dyrosaurus was an extinct genus of dyrosaurid crocodyliform from the Eocene of North Africa. The type species D. phosphaticus possessed slender jaws with numerous recurved teeth, indicative of a primarily fish diet...
, Atlantosuchus
Atlantosuchus
Atlantosuchus is an extinct genus of dyrosaurid crocodylomorph from Morocco. One defining characteristic that distinguishes it from other long-snouted dyrosaurids was its proportionally elongate snout, the longest in proportion to body size of any dyrosaurid...
, Rhabdognathus
Rhabdognathus
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...
, and Congosaurus
Congosaurus
Congosaurus is an extinct genus of dyrosaurid mesoeucrocodylian. Fossils have been found from Angola and date back to the Paleocene epoch. In 1952 and 1964 Congosaurus was proposed to be synonymous with Dyrosaurus. The genus was later regarded to be synonymous with Hyposaurus in 1976 and 1980...
. 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 cm (28.3–33.9 in) long, about midsize for a dyrosaurid. It grew to a relatively large size compared to most dyrosaurids, between 4.66 and 6.46 m (15.3 and 21.2 ft).
Life history
Acherontisuchus lived in a calm, shallow, inlandInland
Inland is an area of land away from the coast or shore line. It usually refers to the interior part of a country or region.Inland may refer to:* Inland Fräkne Hundred, a hundred of Bohuslän in Sweden...
freshwater
Freshwater
Fresh water is naturally occurring water on the Earth's surface in ice sheets, ice caps, glaciers, bogs, ponds, lakes, rivers and streams, and underground as groundwater in aquifers and underground streams. Fresh water is generally characterized by having low concentrations of dissolved salts and...
habitat in the tropical rainforest
Tropical rainforest
A tropical rainforest is an ecosystem type that occurs roughly within the latitudes 28 degrees north or south of the equator . This ecosystem experiences high average temperatures and a significant amount of rainfall...
s of northeastern Colombia, where its distant cousin Cerrejonisuchus
Cerrejonisuchus
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...
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
Buoyancy
In physics, buoyancy is a force exerted by a fluid that opposes an object's weight. In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid. Thus a column of fluid, or an object submerged in the fluid, experiences greater pressure at the bottom of the...
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 current
Ocean current
An ocean current is a continuous, directed movement of ocean water generated by the forces acting upon this mean flow, such as breaking waves, wind, Coriolis effect, cabbeling, temperature and salinity differences and tides caused by the gravitational pull of the Moon and the Sun...
s. Since Acherontisuchus lived in a shallow freshwater environment, it had less need to control its position.
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 lungfish
Lungfish
Lungfish are freshwater fish belonging to the Subclass Dipnoi. Lungfish are best known for retaining characteristics primitive within the Osteichthyes, including the ability to breathe air, and structures primitive within Sarcopterygii, including the presence of lobed fins with a well-developed...
es and eel
Eel
Eels are an order of fish, which consists of four suborders, 20 families, 111 genera and approximately 800 species. Most eels are predators...
s.
Systematics
Acherontisuchus is closely related dyrosaurids from both Africa and the Americas. The phylogenetic analysis conducted with its first description placed Acherontisuchus in an derivedDerived
In phylogenetics, a derived trait is a trait that is present in an organism, but was absent in the last common ancestor of the group being considered. This may also refer to structures that are not present in an organism, but were present in its ancestors, i.e. traits that have undergone secondary...
clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
of dyrosaurids that included Hyposaurus
Hyposaurus
Hyposaurus is a genus of extinct dyrosaurid crocodyliform. Fossils have been found in Paleocene aged rocks of the Maria Farinha Formation in Pernambuco, Brazil and Iullemmeden Basin in West Africa and Maastrichtian strata in New Jersey. It was related to Dyrosaurus....
of North America, Congosaurus
Congosaurus
Congosaurus is an extinct genus of dyrosaurid mesoeucrocodylian. Fossils have been found from Angola and date back to the Paleocene epoch. In 1952 and 1964 Congosaurus was proposed to be synonymous with Dyrosaurus. The genus was later regarded to be synonymous with Hyposaurus in 1976 and 1980...
, Atlantosuchus
Atlantosuchus
Atlantosuchus is an extinct genus of dyrosaurid crocodylomorph from Morocco. One defining characteristic that distinguishes it from other long-snouted dyrosaurids was its proportionally elongate snout, the longest in proportion to body size of any dyrosaurid...
, and Rhabdognathus
Rhabdognathus
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...
of Africa, and Guarinisuchus
Guarinisuchus
Guarinisuchus is an extinct genus of marine crocodyliform from the Early Paleocene 62 million years ago of Brazil. The type species is G. munizi.- Sources :*http://news.nationalgeographic.com/news/2008/03/photogalleries/crocodile-pictures/index.html...
of South America. The relationships between these dyrosaurids were not resolved, as Acherontisuchus was placed in a polytomy
Polytomy
A polytomy , meaning many temporal based branches, is a section of a phylogeny in which the evolutionary relationships can not be fully resolved to dichotomies. In a phylogenetic tree, a polytomy is represented as a node which has more than two immediate descending branches...
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
Cladogram
A cladogram is a diagram used in cladistics which shows ancestral relations between organisms, to represent the evolutionary tree of life. Although traditionally such cladograms were generated largely on the basis of morphological characters, DNA and RNA sequencing data and computational...
showing the phylogenetic relationships of Acherontisuchus and the distributions of dyrosaurids: