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Updated: May 14, 2026

Dissection and Explant Culture of Murine Allantois for the In Vitro Analysis of Allantoic Attachment
Published on: January 13, 2018
The placental mammal ancestor and the post-K-Pg radiation of placentals
Maureen A O'Leary1, Jonathan I Bloch, John J Flynn
1Department of Anatomical Sciences, School of Medicine, HSC T-8 (040), Stony Brook University, Stony Brook, NY 11794-8081, USA. maureen.oleary@stonybrook.edu
Abstract:
To discover interordinal relationships of living and fossil placental mammals and the time of origin of placentals relative to the Cretaceous-Paleogene (K-Pg) boundary, we scored 4541 phenomic characters de novo for 86 fossil and living species. Combining these data with molecular sequences, we obtained a phylogenetic tree that, when calibrated with fossils, shows that crown clade Placentalia and placental orders originated after the K-Pg boundary. Many nodes discovered using molecular data are upheld, but phenomic signals overturn molecular signals to show Sundatheria (Dermoptera + Scandentia) as the sister taxon of Primates, a close link between Proboscidea (elephants) and Sirenia (sea cows), and the monophyly of echolocating Chiroptera (bats). Our tree suggests that Placentalia first split into Xenarthra and Epitheria; extinct New World species are the oldest members of Afrotheria.
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