''Coloniatherium'' is a
meridiolestid mammal from the
Late Cretaceous
The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', ...
of
Argentina
Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, th ...
. The single species, ''Coloniatherium cilinskii'', was a large member of the family
Mesungulatidae
Mesungulatidae is an extinct clade of meridiolestidan dryolestoid mammals from the Late Cretaceous of South America and possibly other Gondwannan landmasses. They are particularly notable for their ecological speciation and large size.
Charact ...
.
Taxonomy
''Coloniatherium'' was named in 2009 by
Guillermo Rougier and colleagues and assigned to the family
Mesungulatidae
Mesungulatidae is an extinct clade of meridiolestidan dryolestoid mammals from the Late Cretaceous of South America and possibly other Gondwannan landmasses. They are particularly notable for their ecological speciation and large size.
Charact ...
within the
Dryolestoidea. Dryolestoidea is an extinct mammalian group that occurred in North America, Eurasia, and Africa during the
Jurassic
The Jurassic ( ) is a geologic period and stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The Jurassic constitutes the middle period of ...
and
Early Cretaceous, but survived in South America during the
Late Cretaceous
The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', ...
and into the
Paleocene
The Paleocene, ( ) or Palaeocene, is a geological epoch that lasted from about 66 to 56 million years ago (mya). It is the first epoch of the Paleogene Period in the modern Cenozoic Era. The name is a combination of the Ancient Greek ''pal ...
. The
generic name, ''Coloniatherium'', combines the name of the
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.Weishampel et al., 2004, pp.600-604
Originally thou ...
, 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
incisor
Incisors (from Latin ''incidere'', "to cut") are the front teeth present in most mammals. They are located in the premaxilla above and on the mandible below. Humans have a total of eight (two on each side, top and bottom). Opossums have 18, wher ...
s (probably two or three in the lower jaw), one
canine, three
premolars, and three
molars
The molars or molar teeth are large, flat teeth at the back of the mouth. They are more developed in mammals. They are used primarily to grind food during chewing. The name ''molar'' derives from Latin, ''molaris dens'', meaning "millstone to ...
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
''Leonardus'' is an extinct mammal genus from the Late Cretaceous ( Late Santonian to Maastrichtian) of South America. '' from the approximately contemporaneous
Los Alamitos Formation
The Los Alamitos Formation is a geological formation of the North Patagonian Massif in Rio Negro Province, northwestern Patagonia, Argentina, whose strata date back to the Late Cretaceous (Late Campanian to Maastrichtian). Dinosaur remains are amo ...
of Argentina among dryolestoids.
The petrosal of ''Coloniatherium'' appears to be similar in terms of
phylogenetic
In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...
position to ''
Vincelestes'', an Early Cretaceous Argentinean mammal, but also share some apparently
derived traits with
theria
Theria (; Greek: , wild beast) is a subclass of mammals amongst the Theriiformes. Theria includes the eutherians (including the placental mammals) and the metatherians (including the marsupials) but excludes the egg-laying monotremes.
...
ns (i.e.,
marsupial
Marsupials are any members of the mammalian infraclass Marsupialia. All extant marsupials are endemic to Australasia, Wallacea and the Americas. A distinctive characteristic common to most of these species is that the young are carried in a ...
s,
placental
Placental mammals (infraclass Placentalia ) are one of the three extant subdivisions of the class Mammalia, the other two being Monotremata and Marsupialia. Placentalia contains the vast majority of extant mammals, which are partly distinguishe ...
s, 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 Province
Chubut ( es, Provincia del Chubut, ; cy, Talaith Chubut) is a province in southern Argentina, situated between the 42nd parallel south (the border with Río Negro Province), the 46th parallel south (bordering Santa Cruz Province), the Andes rang ...
. 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'' was a mammal that lived during the Late Cretaceous, in the (Late Campanian-Maastrichtian). Its fossils have been found in the Los Alamitos and the La Colonia Formations of Argentina.
Description
The original specimen of ''Re ...
'', as well as the enigmatic possible multituberculates ''
Argentodites'' and ''
Ferugliotherium
''Ferugliotherium'' is a genus of fossil mammals in the family Ferugliotheriidae from the Campanian and/or Maastrichtian period (Late Cretaceous; around 70 million years ago) of Argentina. It contains a single species, ''Ferugliotherium windhause ...
''. ''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
An omnivore () is an animal that has the ability to eat and survive on both plant and animal matter. Obtaining energy and nutrients from plant and animal matter, omnivores digest carbohydrates, protein, fat, and fiber, and metabolize the nut ...
to
herbivorous
A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthpar ...
diet, ''Coloniatherium cilinskii's'' large population density possibly indicating the latter as it is among the most common vertebrates in its faunal assemblage.
[Chornogubsky, L. (2011). "New remains of the dryolestoid mammal Leonardus cuspidatus from the Los Alamitos Formation (Late Cretaceous, Argentina)". Paläontologische Zeitschrift. doi:10.1007/s12542-010-0095-4.] They are among the most distinctive products of the unique Mesozoic radiation of South American mammals.
References
Bibliography
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{{Taxonbar, from=Q5148434
Dryolestida
Maastrichtian life
Late Cretaceous tetrapods of South America
Cretaceous mammals of South America
Cretaceous Argentina
Fossils of Argentina
Cañadón Asfalto Basin
Fossil taxa described in 2009
Prehistoric mammal genera