''Rodcania'' is an extinct

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

of mammal, belonging to the order

Xenungulata Xenungulata ("strange ungulates") is an order of extinct and primitive South American hoofed mammals that lived from the Late Paleocene to Early Eocene (Itaboraian to Casamayoran in the SALMA classification). Fossils of the order are known f ...

. It contains a single species, ''Rodcania kakan'', which lived during 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 ...

. Its remains were found in

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the sout ...

. The genus name is an anagram of '' Carodnia''.

Description

This animal is only known from scarce fossil remains, and its appearance is therefore only conjectural. From a comparison with its relative '' Carodnia'', it is supposed that ''Rodcania'' was a rather heavy animal with a massive build and strong legs. An adult ''Rodcania'' could weigh around 165 kilograms. ''Rodcania'' is only known from a fragmentary left

mandible In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower teeth in place. The mandible sits beneath the maxilla. It is the only movable bone ...

, bearing the second and third molars. Both teeth are characterized by a thick layer of enamel, vertically oriented

Hunter-Schreger band Hunter-Schreger bands, commonly abbreviated as HSB, are features of the enamel of the teeth in mammals, mostly placentals.Line and Bergqvist, 2005, p. 924 In HSB, enamel prisms are arranged in layers of varying thickness at about right angles ...

s, and distally inclined dental wear marks. ''Rodcania'' differs from its similar relative ''Carodnia'' and other xenungulates by the simplified and mesiodistally short trigonid of the third molar, the absence of paraconid, the protolophid more oblique with respect to the mesiodistal axis, and by a straight and oblique cristid, directed towards the position of the protoconid, and in the wider and longer thalonid. As in all xenungulates, the second lower molar was bilophodont.

Classification

''Rodcania kakan'' was first described in 2020, based on a fossil from the Rio Loro Formation, dated from the

, and found in

Tucumán Province Tucumán () is the most densely populated, and the second-smallest by land area, of the provinces of Argentina. Located in the northwest of the country, the province has the capital of San Miguel de Tucumán, often shortened to Tucumán. Neigh ...

in Northwestern

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 ...

. According to phylogenetic analyzes present in that description, ''Rodcania'' is a basal member of the Carodniidae, one of the two families of xenungulates, a group of large archaid mammals, typical of the Paleocene and Eocene of South America, that may be related with Pyrotheres and

Notoungulate Notoungulata is an extinct order of mammalian ungulates that inhabited South America from the early Paleocene to the Holocene, living from approximately 61 million to 11,000 years ago. Notoungulates were morphologically diverse, with forms resemb ...

Paleoecology

''Rodcania'', about the size of a large

tapir Tapirs ( ) are large, herbivorous mammals belonging to the family Tapiridae. They are similar in shape to a pig, with a short, prehensile nose trunk. Tapirs inhabit jungle and forest regions of South and Central America, with one species inh ...

, was the largest animal from the Rio Loro fauna. The increase in size of xenungulates does not show a clear relationship with the evolution of increasingly derived forms.Javier N. Gelfo; Daniel A. García-López; Lilian P. Bergqvist (2020). "Phylogenetic relationships and palaeobiology of a new xenungulate (Mammalia: Eutheria) from the Palaeogene of Argentina". Journal of Systematic Palaeontology. Online edition. doi:10.1080/14772019.2020.1715496

References

{{Taxonbar, from1=Q97369865, from2=Q112083291 Meridiungulata Paleocene mammals of South America Paleogene Argentina Fossils of Argentina Fossil taxa described in 2008 Prehistoric placental genera Monotypic mammal genera