Coloniatherium
Encyclopedia
Coloniatherium is a dryolestoid mammal from the Late Cretaceous
of Argentina
. The single species, Coloniatherium cilinskii, was a large member of the family Mesungulatidae.
. Dryolestoidea is an extinct mammalian group that occurred in North America, Eurasia, and Africa during the Jurassic
and Early Cretaceous
, but survived in South America during the Late Cretaceous
and into the Paleocene
. The generic name, Coloniatherium, combines the name of the La Colonia Formation
, the stratigraphical unit where fossils of the animal were found, and its namesake the Sierra de La Colonia with the Greek therion "beast". The specific name, cilinskii, honors Juan Cilinski, a local rancher who helped with the fieldwork that led to the discovery of Coloniatherium.
s (probably two or three in the lower jaw), one canine, three premolar
s, and three molars
per jaw quadrant. It is larger than Mesungulatum, has broader molars, and the back molars are more reduced; the two also differ in numerous details of tooth morphology. The first molar has three roots, a trait shared only with Leonardus from the approximately contemporaneous Los Alamitos Formation
of Argentina among dryolestoids.
The petrosal of Coloniatherium appears to be similar in terms of phylogenetic position to Vincelestes
, an Early Cretaceous Argentinean mammal, but also share some apparently derived
traits with theria
ns (i.e., marsupial
s, placentals, and relatives). Based on comparisons with Vincelestes, the length of the skull of Coloniatherium would be estimated to be 87.5 mm (3.4 in); comparisons with therians suggest a larger skull length, but the former estimate is more in line with the size of the jaws.
. The mammalian fossils come from the Mirasol Chico valley. The formation includes fluvial (river), deep-sea, and near-shore deposits, and the mammalian fauna probably comes from an estuary, tidal flat, or coastal plain. La Colonia Formation also contains dryolestoids, such as Coloniatherium and Reigitherium
, as well as the enigmatic possible multituberculates Argentodites
and Ferugliotherium
. Coloniatherium is the largest and most abundant mammal found in the formation.
Mesungulatids, including Coloniatherium, are a highly derived group of mammals, possibly specialized for an omnivorous to herbivorous diet. They are among the most distinctive products of the unique Mesozoic radiation of South American mammals.
Late Cretaceous
The Late Cretaceous is the younger of two epochs into which the Cretaceous period is divided in the geologic timescale. Rock strata from this epoch form the Upper Cretaceous series...
of Argentina
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
. The single species, Coloniatherium cilinskii, was a large member of the family Mesungulatidae.
Taxonomy
Coloniatherium was named in 2009 by Guillermo Rougier and colleagues and assigned to the family Mesungulatidae within the DryolestoideaDryolestoidea
Dryolestoidea is an extinct clade of Mesozoic mammals that only contains two orders. It has been suggested that this group contained the ancestors of modern therian mammals. They are mostly represented by teeth, fragmented dentaries and parts of the rostrum. The Jurassic forms retained a...
. Dryolestoidea is an extinct mammalian group that occurred in North America, Eurasia, and Africa during the Jurassic
Jurassic
The Jurassic is a geologic period and system that extends from about Mya to Mya, that is, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic era, also known as the age of reptiles. The start of the period is marked by...
and Early Cretaceous
Early Cretaceous
The Early Cretaceous or the Lower Cretaceous , is the earlier or lower of the two major divisions of the Cretaceous...
, but survived in South America during the Late Cretaceous
Late Cretaceous
The Late Cretaceous is the younger of two epochs into which the Cretaceous period is divided in the geologic timescale. Rock strata from this epoch form the Upper Cretaceous series...
and into the 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...
. The generic name, Coloniatherium, combines the name of the La Colonia Formation
La Colonia Formation
The La Colonia Formation is a geological formation in Argentina whose strata date back to the Late Cretaceous. Dinosaur remains are among the fossils that have been recovered from the formation....
, the stratigraphical unit where fossils of the animal were found, and its namesake the Sierra de La Colonia with the Greek therion "beast". The specific name, cilinskii, honors Juan Cilinski, a local rancher who helped with the fieldwork that led to the discovery of Coloniatherium.
Description
Coloniatherium is known from a few jaw fragments, a number of isolated teeth, and some petrosals (ear bones). It was a large mesungulatid. The animal had an unknown number of incisorIncisor
Incisors are the first kind of tooth in heterodont mammals. They are located in the premaxilla above and mandible below.-Function:...
s (probably two or three in the lower jaw), one canine, three premolar
Premolar
The premolar teeth or bicuspids are transitional teeth located between the canine and molar teeth. In humans, there are two premolars per quadrant, making eight premolars total in the mouth. They have at least two cusps. Premolars can be considered as a 'transitional tooth' during chewing, or...
s, and three molars
Molar (tooth)
Molars are the rearmost and most complicated kind of tooth in most mammals. In many mammals they grind food; hence the Latin name mola, "millstone"....
per jaw quadrant. It is larger than Mesungulatum, has broader molars, and the back molars are more reduced; the two also differ in numerous details of tooth morphology. The first molar has three roots, a trait shared only with Leonardus from the approximately contemporaneous Los Alamitos Formation
Los Alamitos Formation
The Los Alamitos Formation is a geological formation in Rio Negro, Argentina whose strata date back to the Late Cretaceous. Dinosaur remains are among the fossils that have been recovered from the formation.-Dinosaurs:-Mammaliaforms:-References:...
of Argentina among dryolestoids.
The petrosal of Coloniatherium appears to be similar in terms of phylogenetic position to Vincelestes
Vincelestes
Vincelestes is an extinct genus of actively mobile mammal, that lived in what would be South America during the Early Cretaceous from 130—112 mya, existing for approximately ....
, an Early Cretaceous Argentinean mammal, but also share some apparently derived
Derived
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...
traits with theria
Theria
Theria is a subclass of mammals that give birth to live young without using a shelled egg, including both eutherians and metatherians . The only omitted extant mammal group is the egg-laying monotremes....
ns (i.e., marsupial
Marsupial
Marsupials are an infraclass of mammals, characterized by giving birth to relatively undeveloped young. Close to 70% of the 334 extant species occur in Australia, New Guinea, and nearby islands, with the remaining 100 found in the Americas, primarily in South America, but with thirteen in Central...
s, placentals, and relatives). Based on comparisons with Vincelestes, the length of the skull of Coloniatherium would be estimated to be 87.5 mm (3.4 in); comparisons with therians suggest a larger skull length, but the former estimate is more in line with the size of the jaws.
Range and ecology
Fossils of Coloniatherium come from the La Colonia Formation, which outcrops in north-central Chubut ProvinceChubut Province
Chubut a province in the southern part of Argentina situated between the 42nd parallel south and the 46th parallel south , the Andes range separating Argentina from Chile, and the Atlantic ocean...
. The mammalian fossils come from the Mirasol Chico valley. The formation includes fluvial (river), deep-sea, and near-shore deposits, and the mammalian fauna probably comes from an estuary, tidal flat, or coastal plain. La Colonia Formation also contains dryolestoids, such as Coloniatherium and Reigitherium
Reigitherium
Reigitherium bunodontum is a mammal that lived during the Late Cretaceous . Fossils of it have been found in the Los Alamitos and the La Colonia Formations of Argentina....
, as well as the enigmatic possible multituberculates Argentodites
Argentodites
Argentodites is a possible multituberculate mammal from the Cretaceous of Argentina. The single species, Argentodites coloniensis, is known from a single blade-like fourth lower premolar from the La Colonia Formation, which is mostly or entirely Maastrichtian in age...
and Ferugliotherium
Ferugliotherium
Ferugliotherium is a fossil mammal from the Campanian and/or Maastrichtian of Argentina in the family Ferugliotheriidae. The genus contains a single species, Ferugliotherium windhauseni, which was first described in 1986...
. Coloniatherium is the largest and most abundant mammal found in the formation.
Mesungulatids, including Coloniatherium, are a highly derived group of mammals, possibly specialized for an omnivorous to herbivorous diet. They are among the most distinctive products of the unique Mesozoic radiation of South American mammals.