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<p>“Peradectoids” are among the most discussed extinct metatherians, primarily due to their uncertain affinities. Among South American localities, the Itaboraí Basin (late Paleocene-early Eocene), southeastern Brazil, preserves a minimum of five genera and seven species of putative “peradectoids”. Among them, a small-sized taxon, <i>Lonchotrigonatus osvaldoi</i> gen. et sp. nov., is described based on dental features. A phylogenetic analysis recovered it, other Itaboraí “peradectoids” (<i>Bergqvistherium</i> and <i>Procaroloameghinia</i>), and the Australian <i>Archaeonothos</i> within a clade, here informally named the southern peradectoid clade. These taxa did not form a clade with Peradectidae, which was also not recovered as a clade. The analysis suggests a late Campanian maximum origin for the clade comprising Peradectidae and Sudameridelphia. The cf. “<i>Peradectes</i>” <i>austrinum</i> from Tiupampa has a similar dental pattern to the ancestral lineage of Sudameridelphia, with the latter evolving from a common ancestor with a broad stylar shelf, straight centrocrista, and subequal paracone and metacone. Southern peradectoids share more dental features with notometatherians such as “herpetotheriids” than with northern “peradectoids”. Multiple South American clades comprise the early Eocene Australian fauna from Tingamarra. The early southern peradectoids occupied the role of generalized faunivores (insectivores-carnivores), especially at Itaboraí and Tingamarra, with <i>Lonchotrigonatus</i> and <i>Archaeonothos</i> as small-sized predators.</p>

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A small animalivorous mammal from the Paleogene of South America and the ancestral dental pattern of South American metatherians

  • 期刊论文

  • 发表日期：

    2026年5月2日

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  • Leonardo M. Carneiro,
  • Hugo Bampi,
  • Rafael Costa da Silva

摘要

“Peradectoids” are among the most discussed extinct metatherians, primarily due to their uncertain affinities. Among South American localities, the Itaboraí Basin (late Paleocene-early Eocene), southeastern Brazil, preserves a minimum of five genera and seven species of putative “peradectoids”. Among them, a small-sized taxon, Lonchotrigonatus osvaldoi gen. et sp. nov., is described based on dental features. A phylogenetic analysis recovered it, other Itaboraí “peradectoids” (Bergqvistherium and Procaroloameghinia), and the Australian Archaeonothos within a clade, here informally named the southern peradectoid clade. These taxa did not form a clade with Peradectidae, which was also not recovered as a clade. The analysis suggests a late Campanian maximum origin for the clade comprising Peradectidae and Sudameridelphia. The cf. “Peradectes” austrinum from Tiupampa has a similar dental pattern to the ancestral lineage of Sudameridelphia, with the latter evolving from a common ancestor with a broad stylar shelf, straight centrocrista, and subequal paracone and metacone. Southern peradectoids share more dental features with notometatherians such as “herpetotheriids” than with northern “peradectoids”. Multiple South American clades comprise the early Eocene Australian fauna from Tingamarra. The early southern peradectoids occupied the role of generalized faunivores (insectivores-carnivores), especially at Itaboraí and Tingamarra, with Lonchotrigonatus and Archaeonothos as small-sized predators.