''Callistoe'' is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

sparassodont Sparassodonta (from Greek to tear, rend; and , gen. , ' tooth) is an extinct order of carnivorous metatherian mammals native to South America, related to modern marsupials. They were once considered to be true marsupials, but are now thought ...

. It lived during the Early

Eocene The Eocene ( ) is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (Ma). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene'' comes ...

, and its fossilized remains were found in

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...

Description

Unlike most of its relatives, such as '' Proborhyaena'' and ''

Arminiheringia ''Arminiheringia'' is an extinct genus of sparassodont. It lived during the Early Eocene in South America. Description This animal had an exceptionally robust skull with strong teeth. The lower canines were exceptionally long and projected forw ...

'', ''Callistoe'' had a narrow, puny snout, and the shape of its skull resembled that of a

thylacine The thylacine (; binomial name ''Thylacinus cynocephalus''), also commonly known as the Tasmanian tiger or Tasmanian wolf, was a carnivorous marsupial that was native to the Mainland Australia, Australian mainland and the islands of Tasmani ...

. ''Callistoe'' lacked the characteristics associated with the ability to climb in its limbs and vertebrae. The shape of its limb joints, the presence of an ossified patella and the shape of the limb bones show that it was limited to a parasagittal gait, and possessed little flexibility in its elbows, wrists, knees and ankles; ''Callistoe'' probably specialized in walking and running. ''Callistoe'', approximately two meters long, had a slender and light body, and weighed approximately 23 kilograms.

Classification

''Callistoe vincei'' was first described in 2002, based on an almost complete and exceptionally preserved skeleton from the Lumbrera Formation, in the

Salta Province Salta () is a Provinces of Argentina, province of Argentina, located in the northwest of the country. Neighboring provinces are from the east clockwise Formosa Province, Formosa, Chaco Province, Chaco, Santiago del Estero Province, Santiago del Es ...

Argentina Argentina, officially the Argentine Republic, is a country in the southern half of South America. It covers an area of , making it the List of South American countries by area, second-largest country in South America after Brazil, the fourt ...

. Its generic name, ''Callistoe'', derives from

Callisto CALLISTO (''Cooperative Action Leading to Launcher Innovation in Stage Toss-back Operations'') is a reusable VTVL Prototype, demonstrator propelled by a small 40 kN Japanese LOX-LH2 rocket engine. It is being developed jointly by the CNES, French ...

, a

nymph A nymph (; ; sometimes spelled nymphe) is a minor female nature deity in ancient Greek folklore. Distinct from other Greek goddesses, nymphs are generally regarded as personifications of nature; they are typically tied to a specific place, land ...

loved by

Zeus Zeus (, ) is the chief deity of the List of Greek deities, Greek pantheon. He is a sky father, sky and thunder god in ancient Greek religion and Greek mythology, mythology, who rules as king of the gods on Mount Olympus. Zeus is the child ...

, and transformed by him into a

bear Bears are carnivoran mammals of the family (biology), family Ursidae (). They are classified as caniforms, or doglike carnivorans. Although only eight species of bears are extant, they are widespread, appearing in a wide variety of habitats ...

to protect her from

Hera In ancient Greek religion, Hera (; ; in Ionic Greek, Ionic and Homeric Greek) is the goddess of marriage, women, and family, and the protector of women during childbirth. In Greek mythology, she is queen of the twelve Olympians and Mount Oly ...

's wrath. ''Callistoe'' was a member of the family

Proborhyaenidae Proborhyaenidae is an extinct Family (biology), family of metatherian mammals of the order Sparassodonta, which lived in South America from the Eocene (Mustersan) until the Oligocene (Deseadan). Sometimes it has been included as a subfamily of th ...

, a clade of

Sparassodont Sparassodonta (from Greek to tear, rend; and , gen. , ' tooth) is an extinct order of carnivorous metatherian mammals native to South America, related to modern marsupials. They were once considered to be true marsupials, but are now thought ...

s typical of the Early

Cenozoic The Cenozoic Era ( ; ) is Earth's current geological era, representing the last 66million years of Earth's history. It is characterized by the dominance of mammals, insects, birds and angiosperms (flowering plants). It is the latest of three g ...

, usually large-sized and with a robust build.

Paleobiology

Argot & Babot described in 2011 very long and slightly curved claws, quite different from those of other sparassodonts; their shape suggesting an ability to dig. What appears to be an healed fracture on the front leg of a specimen of ''Callistoe'' indicates that those were used intensively. The slender outer toes of the quite short feet indicates an aptitude for running. ''Callistoe'' lived alongside a large variety of

armadillo Armadillos () are New World placental mammals in the order (biology), order Cingulata. They form part of the superorder Xenarthra, along with the anteaters and sloths. 21 extant species of armadillo have been described, some of which are dis ...

s and small

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

s, all animals with fossorial habits, and it is possible that the animal covered large distances and was able to enter the burrows of these animals. As it lived during the Early Eocene, it may be one of the first examples of a predatory mammal with fossorial habits, millions of years before the rise of the first burrowing

mustelidae The Mustelidae (; from Latin , weasel) are a diverse family of carnivora, carnivoran mammals, including weasels, badgers, otters, polecats, martens, grisons, and wolverines. Otherwise known as mustelids (), they form the largest family in the s ...

on other continents. The dental morphology of ''C. vincei'', particularly the presence of a

trigonid 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 tooth ...

cutting-edge that was maintained by tooth wear and overeruption, suggests that it was a hypercarnivore.

Bibliography

*Babot, María J.; Jaime E. Powell; Christian de Muizon (2002). "Callistoe vincei a new Proborhyaenidae (Borhyaenoidea, Metatheria, Mammalia) from the Early Eocene of Argentina". Geobios 35 (5): 615–629. doi:10.1016/S0016-6995(02)00073-6. *Argot, C. & Babot, J. 2011. Postcranial morphology, functional adaptations and palaeobiology of Callistoe vincei, a predaceous metatherian from the Eocene of Salta, north-western Argentina. Palaeontology 54, 411–480. {{Taxonbar, from=Q20721931 Sparassodonta Eocene mammals of South America Fossils of Argentina Paleogene Argentina Fossil taxa described in 2002 Prehistoric mammal genera