Systematic affinities of the extinct metatherian Eobrasilia coutoi Simpson, 1947, a South American Early Eocene Stagodontidae: implications for "Eobrasiliinae"

2017/12/29 by Leonardo M. Carneiro, Édison Vicente Oliveira · 2 citations
Earth and Planetary Sciences · #Evolution and Paleontology Studies #Paleontology and Evolutionary Biology #Paleontology and Stratigraphy of Fossils #Sister group #Taxon #Affinities #Phylogenetic tree #Biology #Zoology #Evolutionary biology #Paleontology #Cretaceous #Morphology (biology) #Geography #Genealogy #Clade #History

paper · pdf · doi:10.4072/rbp.2017.3.07

openalex publication_date 2017/12/29 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/04

Abstract

Eobrasilia coutoi Simpson is currently considered one of the most enigmatic metatherian mammals of Itabora Basin, Brazil. A single badly broken and incomplete skull, with a single strongly worn M3, and an associated fragmentary dentary are the elements currently attributed to this taxon. This fragmentary condition contributes for its uncertain position within Metatheria. Herein, the preserved dental morphology of this species is re-analyzed. The morphology of these structures, such as a tiny, obliquely oriented, one-rooted P1; absence of retro-premolar spaces between the premolars and mesiodistally developed p3, supports the assignment of Eobrasilia as a South American stagodontid. This new result leads a systematic review of the affinities of "Eobrasiliinae", currently represented by Eobrasilia, Gaylordia and Didelphopsis. The hypothesis that "Eobrasiliinae" represents a valid taxon is refuted in the phylogenetic analysis, which recovered Eobrasilia as more closely related to Didelphodon within Stagodontidae, Gaylordia as the sister taxon of Tiulordia and more closely related to Minusculodelphis and Marmosopsis, and Didelphopsis as the sister taxon of Itaboraidelphys and more closely related to Herpetotherium, Carolopaulacoutoia and Derorhynchus. The shared characters between Eobrasilia, Gaylordia and Didelphopsis were likely a result of convergent evolution, as these three lineages independently adapted to more durophagous diets. The phylogenetic analysis did not support the sister relation between Fumodelphodon and Didelphodon and Eodelphis and Hoodootherium. The grouping of Eobrasilia and Didelphodon corroborates the previous hypothesis that Metatheria dispersed from North to South America during the Late Cretaceous.

Citations

• The phylogeny and evolution of Cretaceous–Palaeogene metatherians: cladistic analysis and description of new early Palaeocene specimens from the Nacimiento Formation, New Mexico
• Dispersal, vicariance, and the Late Cretaceous to early tertiary land mammal biogeography from South America to Australia
• The Gondwanan and South American Episodes: Two Major and Unrelated Moments in the History of the South American Mammals
• TNT, a free program for phylogenetic analysis
• Giant taxon‐character matrices: quality of character constructions remains critical regardless of size
• A large carnivorous mammal from the Late Cretaceous and the North American origin of marsupials

Cited by

• Diversity, Affinities and Adaptations of the Basal Sparassodont Patene (Mammalia, Metatheria)
• Didelphodon [wikipedia]

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