title: Taxonomy, affinities, and paleobiology of the tiny metatherian mammal Minusculodelphis, from the early Eocene of South America.
abstract: With less than 3 g of estimated body mass, the early Eocene Minusculodelphis minimus Paula Couto (Mammalia, Metatheria, Jaskhadelphyidae) is one of the smallest mammals, living or extinct. It has alternatively been regarded as a didelphid or a derorhynchid "ameridelphian," or even as an eometatherian marsupial. Here, we describe a new species of Minusculodelphis coming from the same locality (Itaboraí Quarry, Brazil) and age (Itaboraian age) of the type species of the genus. It differs from M. minimus in its larger size and several dental characters. The new species offers data on the upper dentition and femur, which are unknown in the type species. Compared to other Paleogene metatherians, Minusculodelphis shows closer relationships with Jaskhadelphys, from the early Paleocene of Tiupampa, Bolivia, as well as with Kiruwamaq, from the late Eocene-early Oligocene of Perú. A cladistic analysis places all three genera within the family Jaskhadelphyidae (Metatheria, Order indet.), which includes small to tiny, insectivorous-like metatherians. We argue that insectivory (soft insects) is the best-supported diet for both species of Minusculodelphis, and that the most probable microhabitat for them was the understorey or leaf litter of tropical, rain forested environments.
authors.affiliation: Departamento de Geologia, Centro de Tecnologia e Geociências, Universidade Federal de Pernambuco, UFPE, Av. Acadêmico Hélio Ramos s/n, CEP 50740-530, Recife, PE, Brazil. vicenteedi@gmail.com.|CNPq (Conselho Nacional de Desenvolvimento Científico e Tecnológico), Brasilia, Brazil. vicenteedi@gmail.com.
authors.forename: Édison Vicente
authors.initials: ÉV
authors.lastname: Oliveira
authors.affiliation: IBIGEO (Instituto de Bio y Geociencias del Noroeste), Facultad de Ciencias Naturales, Universidad Nacional de Salta, 9 de Julio 14, Rosario de Lerma, 4405, Salta, Argentina.|División Paleontología Vertebrados, Museo de La Plata, Paseo del Bosque s/n, B1900FWA, La Plata, Argentina.
authors.forename: Natalia
authors.initials: N
authors.lastname: Zimicz
authors.affiliation: División Paleontología Vertebrados, Museo de La Plata, Paseo del Bosque s/n, B1900FWA, La Plata, Argentina.|CONICET (Consejo Nacional de Investigaciones Científicas y Técnicas), Buenos Aires, Argentina.
authors.forename: Francisco J
authors.initials: FJ
authors.lastname: Goin
mesh_terms: D000818:Animals; D004032:Diet; D017753:Ecosystem; D005269:Femur / Q000033:anatomy & histology; D005580:Fossils; D008394:Marsupialia / Q000033:anatomy & histology* / Q000145:classification* / Q000502:physiology; D010802:Phylogeny; D013020:South America; D013045:Species Specificity; D014070:Tooth / Q000033:anatomy & histology
keywords: Brazil; Itaboraí; Jaskhadelphyidae; Metatheria; Paleogene; Systematics