Sparassocynus (Marsupialia, Didelphidae), a peculiar mammal from the late Cenozoic of Argentina

Abstract

The extinct genus Sparassocynus is known from the Montehermosan, Chapadmalalan, and Uquian stages of Argentina, spanning the Pliocene‐Pleistocene transition, and a relative occurs in the older Huayquerian. After a taxonomict review, the morphology of skull, mandible, and dentition is described. The short, triangular face, wide zygomata, broad cranium with large completely bone‐enclosed hypo‐ and epitympanic sinuses, and carnassialized molars are unique among known American marsupials. All these characters are functionally convergent toward living Australian phascogaline dasyurids, small marsupial carnivores, although phylogenetically Sparassocynus clearly represents a moderately specialized offshoot of the American family Didelphidae. It represents a small steppe carnivore now ecologically replaced, at least in part, by placental carnivores that spread from North America in the late Pliocene and Pleistocene.

Biostratigraphy and correlation of the Monte Hermoso Formation (early Pliocene, Argentina): The evidence from caviomorph rodents

“…Simpson (1972) instead supported the independence of both faunas until a complete revision of Kraglievich's 1934 paper was accomplished. Reig and Simpson (1972) supported that the fauna of Chapadmalal Formation is more closely related to that of the overlying Vorohué Formation than that of the Monte Hermoso Formation. Marshall et al (1983) differentiated both ages.…”

“…3-Biozone of P. chapalmalensis. Exclusive taxa: P. chapalmalensis (Ameghino, 1908) (Bordas, 1933); Sparassocynus derivatus Reig and Simpson, 1972; Thylatheridium cristatum Reig, 1952;Microtragulus reigi Simpson, 1970. Last record: Argyrolagus; Lutreolina tracheia (Rovereto, 1914) …”

A new species of small-bodied sparassodont (Mammalia, Metatheria) from the middle Miocene locality of Quebrada Honda, Bolivia

“…This hypothesis is supported by UF 27881, which expands the known diversity of small sparassodonts during the middle Miocene. It is also supported by the observation that many species of hypercarnivorous didelphoid taxa first appear in the fossil record only when the diversity of small sparassodonts begins to wane (Reig and Simpson, 1972;Goin and Pardiñas, 1996).…”

“…4C, D) and some didelphoids (e.g., Sparassocynus and caluromyids; see Reig and Simpson, 1972;Voss and Jansa, 2009), UF 27881 lacks any trace of the maxillopalatine fenestrae. Additionally, the palate of UF 27881 bears many tiny foramina instead of a single, large major palatine foramen.…”

Contribution to the knowledge of the Sparassocynidae (Mammalia, Metatheria, Didelphoidea), with comments on the age of the Aisol Formation (Neogene), Mendoza Province, Argentina

“…Most other faunivorously-specialised metatherians, such as sparassocynid and didelphin didelphimorphians (Reig and Simpson 1972;Jansa 2003, 2009;Forasiepi et al 2009), differ from Archaeonothos henkgodthelpi in exhibiting a V-shaped, rather than straight, centrocrista. The centrocrista is straight in the Cretaceous Laurasian deltatheroidans, but the latter differ markedly from A. henkgodthelpi in having a paracone that is taller than the metacone (probably a boreosphenidan plesiomorphy; Rougier et al 2004;Davis et al 2008).…”