''Cronopio'' 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 small insectivorous mammal known from the early Late Cretaceous of the Río Negro region in

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 ...

. Its only species is ''Cronopio dentiacutus''.supplementary information
It belongs to the Meridiolestida, an extinct group of mammals widespread in South America during the Late Cretaceous, which are more closely related to modern

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 and

placental mammals 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 ...

than to monotremes.

Description

''Cronopio'' is known from the

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of sever ...

MPCA PV 454, a partial

skull The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, th ...

around 27mm long which is missing the skull roof, basicranium and squamosals and from the referred specimens MPCA PV 450, a partial left

lower jaw 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 ...

with damaged teeth and MPCA PV 453, an incomplete skull with a relatively complete right lower jaw missing some teeth. All specimens were collected in La Buitrera locality, from the Candeleros Formation of the

Neuquén Group The Neuquén Group is a group of geologic formations found in Argentina. Rocks in the Neuquén Group fall within the Cenomanian to early Campanian stages of the Late Cretaceous Period. It overlies the older Lohan Cura Formation and is itself over ...

, dating to the early Cenomanian stage of the early

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'', ...

, about 99.6-96

million years ago The abbreviation Myr, "million years", is a unit of a quantity of (i.e. ) years, or 31.556926 teraseconds. Usage Myr (million years) is in common use in fields such as Earth science and cosmology. Myr is also used with Mya (million years ago) ...

. Paleontologist Guillermo Rougier commented on the creature's "superficial" resemblance to the fictional character

Scrat Scrat is a fictional character in the ''Ice Age'' franchise. He is a saber-toothed squirrel who is obsessed with collecting acorns, constantly putting his life in danger to obtain and defend them. Scrat's storylines are mostly independent o ...

in the '' Ice Age franchise'' created by

Chris Wedge John Christian Wedge (born March 20, 1957) is an American animator, designer, film director, voice actor, film producer, screenwriter, and cartoonist. He is known for directing the films '' Ice Age'' (2002), ''Robots'' (2005), '' Epic'' (2013), ...

, saying "it just goes to show how diverse ancient mammals are, that we can just imagine some bizarre critter and later find something just like it."

Etymology

''Cronopio'' was first named by Guillermo W. Rougier, Sebastián Apesteguía and Leandro C. Gaetano in 2011 and the

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specime ...

is ''C. dentiacutus''. The generic name is named after the fictional characters appearing in the work of Argentinian writer Julio Cortázar. The specific name is derived from

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

, meaning "sharp-toothed".

Phylogeny

Cladogram A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to ...

following the analysis of Rougier, Wible, Beck and Apesteguía (2012):

References

{{Taxonbar, from1=Q16014290, from2=Q134994 Dryolestida Late Cretaceous mammals Cenomanian life Cretaceous mammals of South America Late Cretaceous tetrapods of South America Cretaceous Argentina Fossils of Argentina Candeleros Formation Fossil taxa described in 2011