Cerrejonisuchus
Encyclopedia
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.
/IGM 29 and UF/IGM 31. Cerrejonisuchus has the shortest body length of any known dyrosaur, much smaller than that of the longest dyrosaur, Phosphatosaurus gavialoides
, which was 7.22 metres (23.7 ft) to 8.05 metres (26.4 ft) in length.
Currently the only known specimens of Cerrejonisuchus are UF/IGM 29 (the type specimen
), UF/IGM 30, UF/IGM 31, and UF/IGM 32. Of these, UF/IGM 29 and UF/IGM 31 are thought to represent fully mature individuals while UF/IGM 32 is thought to represent a less mature individual. In UF/IGM 31, the neurocentral sutures of the anterior dorsal vertebrae are closed, an indication of morphological maturity. Additionally, the presence of well-developed osteoderm
s is likely to be an indication that the animal was mature because in living crocodylians, the osteoderms begin calcification after 1 year and grow to articulate with other osteoderms to form a dermal shield at maturity. Also, the sutures that separate the bones of the skull in both specimens are fully fused, suggesting that the individuals have reached a late ontogenic stage. In contrast, UF/IGM 32 has an unfused nasal
suture, suggesting that it was less mature than the other individuals. UF/IGM 32 is also noticeably smaller than the other specimens.
Relative to the entire skull length, the rostrum of Cerrejonisuchus is the shortest of any dyrosaurid. It, along with Chenanisuchus
, are the only short-snouted dyrosaurids. The snout of Cerrejonisuchus is narrow and consistent in width from the external nares, or nostril
openings, to the orbit
s, or eye sockets. The margin of the snout, unlike that of many long-snouted dyrosaurids, is smooth rather than festooned. "Festooned" refers to the lateral undulations in the maxillae and premaxillae that form around the tooth sockets, or alveoli. The external nares are positioned extremely anteriorly at the very tip of the snout. The orbits are oriented anterodorsally, facing upward and slightly forward. The dentition of Cerrejonisuchus is generally homodont, although the third maxilla
ry tooth is enlarged and the fourth is somewhat smaller than the rest. They are conical, labiolingually
compressed, each having a relatively rounded apex. The carinae, or tooth edges, are strongly developed both anteriorly and posteriorly. The premaxilla
ry teeth are generally thinner and longer than the maxillary teeth. Like Chenanisuchus, Cerrejonisuchus visibly lacks striations on the tooth surfaces. Unlike many other dyrosaurids, including Dyrosaurus maghribensis
, Atlantosuchus coupatezi
, Guarinisuchus munizi
, Phosphatosaurus gavialoides, and Sokotosuchus ianwilsoni
, the teeth of Cerrejonisuchus are not curved.
ly in the dyrosaur clade between Phosphatosaurus gavialoides and Arambourgisuchus khouribgaensis
. Cerrejonisuchus was not found to be closely related to the other short-snouted dyrosaur Chenanisuchus, which was placed at the base of the clade. Although it might be expected that Chenanisuchus and Cerrejonisuchus are closely related because they are the only dyrosaurids with short snouts, the results of the analysis show that snout proportions alone are not indicative of phylogenetic relatedness in dyrosaurs.
Below is the cladogram
from Hastings et al. (2010) showing the phylogenetic relationship of Cerrejonisuchus within Dyrosauridae:
in the neotropical rainforest environment of Paleocene Colombia.
Cerrejonisuchus is known from the Middle to Late Paleocene Cerrejón Formation. All known specimens have been found from the Cerrejón open-pit coal mine at the La Puente Pit below Coal Seam 90. The mine has also yielded remains of Titanoboa cerrejonensis
, a recently described 12.8 metres (42 ft) long extinct boid that is the largest known snake to have ever existed. Like Cerrejonisuchus, fossils of Titanoboa were found in a gray claystone
layer directly underlying Coal Seam 90. Additional dyrosaurid material has been found from the Cerrejón Formation alongside that of Cerrejonisuchus, and is thought to represent at least two different taxa. The age of the Cerrejón Formation has been dated as Middle-Late Paleocene based on carbon
isotope
s, pollen
, spore
s, and dinoflagellate
cysts.
The section of the Cerrejón Formation from which fossils of Cerrejonisuchus have been found was likely deposited in a transitional environment, probably brackish water
in a river
-to-lagoon
al setting. Large freshwater podocnemidid
turtle
s and dipnoan
and elopomorph
fish
es have also been found from this part of the formation. Cerrejonisuchus may have been a food source for Titanoboa, which would have lived in the same brackish water environment. The vertebrate paleofauna of the Cerrejón Formation was similar to modern neotropical riverine vertebrate faunas.
During the Paleocene, river systems would have incised a coastal plain
covered by a wet neotropical rainforest
. The global temperature was much warmer than it is today, based on paleoclimate models. The latitudinal temperature gradient between the equator and mid-latitudes of South America was similar to the gradient that exists today. Elevated levels of carbon dioxide
in the atmosphere are thought to have caused the global greenhouse temperature. The high rainfall estimates and increased pCO2 would have maintained the rainforest floras during the Paleocene greenhouse.
and the Cretaceous–Tertiary extinction event. There may have been a dispersal from Africa
to Brazil
, and continued immigration into North America
. Colombia can be seen as a transitional route from Brazil to North America, and also to Bolivia
, assuming that it was coastal.
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....
crocodylomorph. It is known from a complete skull and mandible 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...
in 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...
, which is Paleocene
Paleocene
The Paleocene or Palaeocene, the "early recent", is a geologic epoch that lasted from about . It is the first epoch of the Palaeogene Period in the modern Cenozoic Era...
in age. Specimens belonging to Cerrejonisuchus and to several other dyrosaurids have been found from 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...
open-pit
Open-pit mining
Open-pit mining or opencast mining refers to a method of extracting rock or minerals from the earth by their removal from an open pit or borrow....
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.
Description
At an estimated length of 1.22 metres (4 ft) to 2.22 metres (7.3 ft), Cerrejonisuchus was small for a dyrosaur. This size estimate is based on the dorsal skull lengths of specimens UFFlorida Museum of Natural History
The Florida Museum of Natural History is the State of Florida's official state-sponsored and chartered natural history museum. Its main facilities are located on the campus of the University of Florida in Gainesville, Florida....
/IGM 29 and UF/IGM 31. Cerrejonisuchus has the shortest body length of any known dyrosaur, much smaller than that of the longest dyrosaur, Phosphatosaurus gavialoides
Phosphatosaurus
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...
, which was 7.22 metres (23.7 ft) to 8.05 metres (26.4 ft) in length.
Currently the only known specimens of Cerrejonisuchus are UF/IGM 29 (the type specimen
Holotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
), UF/IGM 30, UF/IGM 31, and UF/IGM 32. Of these, UF/IGM 29 and UF/IGM 31 are thought to represent fully mature individuals while UF/IGM 32 is thought to represent a less mature individual. In UF/IGM 31, the neurocentral sutures of the anterior dorsal vertebrae are closed, an indication of morphological maturity. Additionally, the presence of well-developed osteoderm
Osteoderm
Osteoderms are bony deposits forming scales, plates or other structures in the dermal layers of the skin. Osteoderms are found in many groups of extant and extinct reptiles, including lizards, various groups of dinosaurs , crocodilians, phytosaurs, aetosaurs, placodonts, and hupehsuchians...
s is likely to be an indication that the animal was mature because in living crocodylians, the osteoderms begin calcification after 1 year and grow to articulate with other osteoderms to form a dermal shield at maturity. Also, the sutures that separate the bones of the skull in both specimens are fully fused, suggesting that the individuals have reached a late ontogenic stage. In contrast, UF/IGM 32 has an unfused nasal
Nasal bone
The nasal bones are two small oblong bones, varying in size and form in different individuals; they are placed side by side at the middle and upper part of the face, and form, by their junction, "the bridge" of the nose.Each has two surfaces and four borders....
suture, suggesting that it was less mature than the other individuals. UF/IGM 32 is also noticeably smaller than the other specimens.
Relative to the entire skull length, the rostrum of Cerrejonisuchus is the shortest of any dyrosaurid. It, along with Chenanisuchus
Chenanisuchus
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.The type species is C...
, are the only short-snouted dyrosaurids. The snout of Cerrejonisuchus is narrow and consistent in width from the external nares, or nostril
Nostril
A nostril is one of the two channels of the nose, from the point where they bifurcate to the external opening. In birds and mammals, they contain branched bones or cartilages called turbinates, whose function is to warm air on inhalation and remove moisture on exhalation...
openings, to the orbit
Orbit (anatomy)
In anatomy, the orbit is the cavity or socket of the skull in which the eye and its appendages are situated. "Orbit" can refer to the bony socket, or it can also be used to imply the contents...
s, or eye sockets. The margin of the snout, unlike that of many long-snouted dyrosaurids, is smooth rather than festooned. "Festooned" refers to the lateral undulations in the maxillae and premaxillae that form around the tooth sockets, or alveoli. The external nares are positioned extremely anteriorly at the very tip of the snout. The orbits are oriented anterodorsally, facing upward and slightly forward. The dentition of Cerrejonisuchus is generally homodont, although the third maxilla
Maxilla
The maxilla is a fusion of two bones along the palatal fissure that form the upper jaw. This is similar to the mandible , which is also a fusion of two halves at the mental symphysis. Sometimes The maxilla (plural: maxillae) is a fusion of two bones along the palatal fissure that form the upper...
ry tooth is enlarged and the fourth is somewhat smaller than the rest. They are conical, labiolingually
Commonly used terms of relationship and comparison in dentistry
There are numerous commonly used terms of relationship and comparison that refer to different aspects of teeth and are frequently utilized in articles about dentistry...
compressed, each having a relatively rounded apex. The carinae, or tooth edges, are strongly developed both anteriorly and posteriorly. The premaxilla
Premaxilla
The incisive bone is the portion of the maxilla adjacent to the incisors. It is a pair of small cranial bones at the very tip of the jaws of many animals, usually bearing teeth, but not always. They are connected to the maxilla and the nasals....
ry teeth are generally thinner and longer than the maxillary teeth. Like Chenanisuchus, Cerrejonisuchus visibly lacks striations on the tooth surfaces. Unlike many other dyrosaurids, including Dyrosaurus maghribensis
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 coupatezi
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...
, Guarinisuchus munizi
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...
, Phosphatosaurus gavialoides, and Sokotosuchus ianwilsoni
Sokotosuchus
Sokotosuchus is an extinct genus of dyrosaurid crocodyliform which existed in Africa.-External links:* at the Paleobiology Database...
, the teeth of Cerrejonisuchus are not curved.
Classification
A phylogenetic analysis of dyrosaurids by Hastings et al. (2010) placed Cerrejonisuchus relatively basalBasal (phylogenetics)
In phylogenetics, a basal clade is the earliest clade to branch in a larger clade; it appears at the base of a cladogram.A basal group forms an outgroup to the rest of the clade, such as in the following example:...
ly in the dyrosaur clade between Phosphatosaurus gavialoides and Arambourgisuchus khouribgaensis
Arambourgisuchus
Arambourgisuchus was a dyrosaurid crocodylomorph from the late Palaeocene of Morocco, found in the region of Sidi Chenane in 2000, following collaboration by French and Moroccan institutions, and described in 2005 by a team led by palaeontologist Stéphane Jouve.Its type and only species is A...
. Cerrejonisuchus was not found to be closely related to the other short-snouted dyrosaur Chenanisuchus, which was placed at the base of the clade. Although it might be expected that Chenanisuchus and Cerrejonisuchus are closely related because they are the only dyrosaurids with short snouts, the results of the analysis show that snout proportions alone are not indicative of phylogenetic relatedness in dyrosaurs.
Below is the 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...
from Hastings et al. (2010) showing the phylogenetic relationship of Cerrejonisuchus within Dyrosauridae:
Feeding strategy
Cerrejonisuchus likely had a diet consisting of fish, invertebrates, frogs, lizards, small snakes, and possibly mammals. The short snout of Cerrejonisuchus is thought to be an adaptation to such a generalized diet. Other long-snouted marine dyrosaurs are presumed to have had a strongly piscivorous diet consisting solely of fish. With its short snout, Cerrejonisuchus would have been able to occupy a new ecological nicheEcological niche
In ecology, a niche is a term describing the relational position of a species or population in its ecosystem to each other; e.g. a dolphin could potentially be in another ecological niche from one that travels in a different pod if the members of these pods utilize significantly different food...
in the neotropical rainforest environment of Paleocene Colombia.
Paleoenvironment
Titanoboa
Titanoboa, , meaning "titanic boa," is a genus of snake that lived approximately 58 to 60 million years ago, in the Paleocene epoch, a 10-million-year period immediately following the dinosaur extinction event...
, a recently described 12.8 metres (42 ft) long extinct boid that is the largest known snake to have ever existed. Like Cerrejonisuchus, fossils of Titanoboa were found in a gray claystone
Claystone
Claystone is a geological term used to describe a clastic sedimentary rock that is composed primarily of clay-sized particles ....
layer directly underlying Coal Seam 90. Additional dyrosaurid material has been found from the Cerrejón Formation alongside that of Cerrejonisuchus, and is thought to represent at least two different taxa. The age of the Cerrejón Formation has been dated as Middle-Late Paleocene based on carbon
Carbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...
isotope
Isotope
Isotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation...
s, pollen
Pollen
Pollen is a fine to coarse powder containing the microgametophytes of seed plants, which produce the male gametes . Pollen grains have a hard coat that protects the sperm cells during the process of their movement from the stamens to the pistil of flowering plants or from the male cone to the...
, spore
Spore
In biology, a spore is a reproductive structure that is adapted for dispersal and surviving for extended periods of time in unfavorable conditions. Spores form part of the life cycles of many bacteria, plants, algae, fungi and some protozoa. According to scientist Dr...
s, and dinoflagellate
Dinoflagellate
The dinoflagellates are a large group of flagellate protists. Most are marine plankton, but they are common in fresh water habitats as well. Their populations are distributed depending on temperature, salinity, or depth...
cysts.
The section of the Cerrejón Formation from which fossils of Cerrejonisuchus have been found was likely deposited in a transitional environment, probably brackish water
Brackish water
Brackish water is water that has more salinity than fresh water, but not as much as seawater. It may result from mixing of seawater with fresh water, as in estuaries, or it may occur in brackish fossil aquifers. The word comes from the Middle Dutch root "brak," meaning "salty"...
in a river
River
A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...
-to-lagoon
Lagoon
A lagoon is a body of shallow sea water or brackish water separated from the sea by some form of barrier. The EU's habitat directive defines lagoons as "expanses of shallow coastal salt water, of varying salinity or water volume, wholly or partially separated from the sea by sand banks or shingle,...
al setting. Large freshwater podocnemidid
Podocnemididae
Podocnemididae is a family of turtles native to Madagascar and northern South America. They are side-necked turtles , which means they do not retract their heads backwards, but hide it sideways....
turtle
Turtle
Turtles are reptiles of the order Testudines , characterised by a special bony or cartilaginous shell developed from their ribs that acts as a shield...
s and dipnoan
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...
and elopomorph
Elopomorpha
The superorder Elopomorpha contains a variety of types of fishes that range from typical silvery colored fish-like species such as the tarpons and ladyfishes of the Elopiformes and the bonefishes of the Albuliformes, to the long and slender, smooth bodied eels of the Anguilliformes...
fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
es have also been found from this part of the formation. Cerrejonisuchus may have been a food source for Titanoboa, which would have lived in the same brackish water environment. The vertebrate paleofauna of the Cerrejón Formation was similar to modern neotropical riverine vertebrate faunas.
During the Paleocene, river systems would have incised a coastal plain
Coastal plain
A coastal plain is an area of flat, low-lying land adjacent to a seacoast and separated from the interior by other features. One of the world's longest coastal plains is located in eastern South America. The southwestern coastal plain of North America is notable for its species diversity...
covered by a wet neotropical rainforest
Rainforest
Rainforests are forests characterized by high rainfall, with definitions based on a minimum normal annual rainfall of 1750-2000 mm...
. The global temperature was much warmer than it is today, based on paleoclimate models. The latitudinal temperature gradient between the equator and mid-latitudes of South America was similar to the gradient that exists today. Elevated levels of carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
in the atmosphere are thought to have caused the global greenhouse temperature. The high rainfall estimates and increased pCO2 would have maintained the rainforest floras during the Paleocene greenhouse.
Paleobiogeography
The presence of dyrosaurids such as Cerrejonisuchus in the Paleocene of Colombia suggests that there was a radiation of dyrosaurids in South America following the K–T boundaryK–T boundary
The K–T boundary is a geological signature, usually a thin band, dated to 65.5 ± 0.3 Ma ago. K is the traditional abbreviation for the Cretaceous period, and T is the abbreviation for the Tertiary period...
and the Cretaceous–Tertiary extinction event. There may have been a dispersal from Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
to Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
, and continued immigration into North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
. Colombia can be seen as a transitional route from Brazil to North America, and also to Bolivia
Bolivia
Bolivia officially known as Plurinational State of Bolivia , is a landlocked country in central South America. It is the poorest country in South America...
, assuming that it was coastal.