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<p>The Itaboraí Basin (late Paleocene-early Eocene), southeastern Brazil, preserved a diverse metatherian fauna. Among them, a pucadelphyid, described as <i>Nyctodon ladevezeae</i> gen. et sp. nov., is identified by its broad, V-shaped protocone with a well-developed protoconal bulge, a trigonid basin higher than the metaconid-entoconid notch, enlarged hypoconulids on m2-4, and p3 with a mesial cuspule. Including <i>Nyctodon</i> gen. nov. in a phylogenetic analysis (PA) recovered it within Pucadelphyidae based on its developed stylar cusp E, broad protocone, trigonids higher and broader than talonids, small entoconids, and hypertrophied hypoconulids. <i>Nyctodon</i> represents a pucadelphyid in the Itaboraí Basin, extending their fossil record to the early Eocene of Brazil. The PA recovered “Pucadelphyoidea” as polyphyletic and did not recover pucadelphyid affinities for <i>Itaboraidelphys</i>, a “sternbergiid” notometatherian, and <i>Mizquedelphys</i>, which is likely closely related to <i>Tiulordia</i> and <i>Gaylordia</i>. The isolated petrosal morphotypes from the Itaboraí Basin do not support <i>Marmosopsis</i> as a member of Pucadelphyda, as the latter was described based on petrosal features, with assigned dental features representing retained plesiomorphies for Sudameridelphia. The m4s of <i>N</i>. <i>ladevezeae</i> resemble the cf. <i>Cimolestes</i> from the Tiupampa fauna, suggesting that this specimen may represent an m4 of an unnoticed ‘pucadelphydan-like’ taxon from this locality. A PCA based on morphometric and morphofunctional variables positioned <i>N</i>. <i>ladevezeae</i> in a similar morphospace to <i>Derorhynchus</i>, an insectivorous or insectivorous-carnivorous metatherian. <i>Nyctodon ladevezeae</i> probably had an insectivorous-omnivorous diet based mainly on invertebrates, but not ruling out fruits and small vertebrates as exploitable food.</p>

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A new pucadelphyid (Metatheria) from the Itaboraí Basin (late Paleocene-early Eocene): systematic affinities, taxonomic revision, and evolutionary inferences for Pucadelphyda

  • 期刊论文

  • 发表日期：

    2025年12月1日

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

摘要

The Itaboraí Basin (late Paleocene-early Eocene), southeastern Brazil, preserved a diverse metatherian fauna. Among them, a pucadelphyid, described as Nyctodon ladevezeae gen. et sp. nov., is identified by its broad, V-shaped protocone with a well-developed protoconal bulge, a trigonid basin higher than the metaconid-entoconid notch, enlarged hypoconulids on m2-4, and p3 with a mesial cuspule. Including Nyctodon gen. nov. in a phylogenetic analysis (PA) recovered it within Pucadelphyidae based on its developed stylar cusp E, broad protocone, trigonids higher and broader than talonids, small entoconids, and hypertrophied hypoconulids. Nyctodon represents a pucadelphyid in the Itaboraí Basin, extending their fossil record to the early Eocene of Brazil. The PA recovered “Pucadelphyoidea” as polyphyletic and did not recover pucadelphyid affinities for Itaboraidelphys, a “sternbergiid” notometatherian, and Mizquedelphys, which is likely closely related to Tiulordia and Gaylordia. The isolated petrosal morphotypes from the Itaboraí Basin do not support Marmosopsis as a member of Pucadelphyda, as the latter was described based on petrosal features, with assigned dental features representing retained plesiomorphies for Sudameridelphia. The m4s of N. ladevezeae resemble the cf. Cimolestes from the Tiupampa fauna, suggesting that this specimen may represent an m4 of an unnoticed ‘pucadelphydan-like’ taxon from this locality. A PCA based on morphometric and morphofunctional variables positioned N. ladevezeae in a similar morphospace to Derorhynchus, an insectivorous or insectivorous-carnivorous metatherian. Nyctodon ladevezeae probably had an insectivorous-omnivorous diet based mainly on invertebrates, but not ruling out fruits and small vertebrates as exploitable food.