A new large didelphid of the genus Thylophorops (Mammalia: Didelphimorphia: Didelphidae), from the late Tertiary of the Pampean Region (Argentina)

Abstract

We describe Thylophorops lorenzinii sp. nov. (Marsupialia, Didelphidae), the largest known didelphid opossum, living or extinct. Its type specimen comes from Late Pliocene levels at Punta San Andrés, southeastern Buenos Aires Province, Argentina. With an estimated body mass between 4.8 and 7.4 kg, it obviously surpasses that of the (up to now) largest didelphid, the living Didelphis virginiana Kerr. In addition to its larger size, the new species differs from T. chapalmalensis Ameghino and T. perplanus Ameghino in that its lower molars have more labially salient hypoconids and proportionally large hypoconulids which are not antero-posteriorly compressed.

Mammalian predator–prey relationships and reoccupation of burrows in the Pliocene of the Pampean Region (Argentina): new ichnological and taphonomic evidence

“…the body masses were taken from redford and Einsenberg (1992), Nowak (1999Nowak ( , 2005, Mares and Braun (2000), and aranda ( for Actenomys sp. presents a better fit to the estimated mass for T. chapadmalensis (3.1-3.7 kg; Goin et al 2009;Zimicz 2014) and C. lutaria (6-7 kg, Soibelzon 2011) than to the remaining small Chapadmalalan carnivores whose body masses are equal or smaller to that of the postulated prey. However, the strong carnivorous trend observed in Hyperdidelphys spp.…”

“…The molar morphology of the new specimens shares the traits described for known species of Thylophorops (see Goin and Pardiñas 1996). The remains were assigned to T. chapadmalensis, because they are smaller than Thylophorops lorenzinii Goin et al 2009 (the largest known didelphid), and larger than other didelphoidea taxa (i.e. Hyperdidelphys spp., Didelphis spp., Lutreolina spp.…”

“…Hyperdidelphys spp., Didelphis spp., Lutreolina spp. and Thylophorops perplanus [Ameghino 1904], see molar measures in Goin et al 2009;Zimicz 2014). Additionally, T. chapadmalensis is the only species of the genus recovered in the Chapadmalal 'Formation' (Goin and Pardiñas 1996).…”

“…During the late Cenozoic in South American, the ecological niches currently occupied by small placental carnivores were dominated by highly specialised didelphimorph marsupials (Reig and Simpson 1972;Goin and Pardiñas 1996;Goin et al 2000;Zimicz 2014). Considering the rest of the guild members, the body mass inferred for the coprolite producer (1-6 kg), allows us to consider as possible producers the large didelphids Hyperdidelphys parvula (0.98 kg; Zimicz 2014), H. inexpectata (0.99 kg; Zimicz 2014) and Thylophorops chapalmalensis (3.1-3.7 kg; Goin et al 2009;Zimicz 2014); or the procyonid C. lutaria (6-7 kg; Soibelzon 2011) with apparently more carnivorous adaptations than its living relatives (Soibelzon 2011). The presence in the fossil assemblage of specimens referred to T. chapalmalensis and C. lutaria strongly supports to these taxa as potencial producers.…”

“…in filling of crotovine' (1996:339) from basal levels of Irene's Formation (possibly correlated with the Chapadmalal 'Formation' , see Isla et al 2014). It has been recently described Thylophorops lorenzinii, found inside a crotovine (type 3) preserved in the San Andrés Formation (late Pliocene -early Pleistocene) and possibly produced by an indeterminate fossorial Xenarthra (Goin et al 2009). On the other hand, the record of C. lutaria here reported is the first evidence of fossil procyonids found in burrows.…”