The Placental Mammal Ancestor and the Post–K-Pg Radiation of Placentals

By Maureen A. OLeary, J. Bloch, J. J. Flynn, T. Gaudin, A. Giallombardo, N. Giannini, Suzann L. Goldberg, B. Kraatz, Zhe‐Xi Luo, Jin Meng and 13 more. Science, 2013

1,124 citations recorded by the source corpus.

Let There Be Mammals The timing of the evolution and radiation of placental mammals and their most recent common ancestor has long been debated, with many questions surrounding the relationships of groups that pre- and postdate the Cretaceous-Paleogene boundary (66 million years ago). While the fossil record suggests that placental mammals radiated after the Cretaceous, molecular clocks have consistently placed the ancestors of mammalian lineages earlier. O'Leary et al. (p. 662; see the Perspective by Yoder) examined the morphology of fossil and extant taxa and conclude that living placentals originated and radiated after the Cretaceous and reconstruct the phenotype of the ancestral placental mammal. Fossil and DNA phylogenies suggest that placental mammals diversified in the Cenozoic and reconstruct the ancestral form. [Also see Perspective by Yoder] 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.

Subfields: Ecology, Evolution, Behavior and Systematics, Paleontology

View Paper: https://www.semanticscholar.org/paper/d7a4824937556d33cd5d499eb469c6e87673a719

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Citations in the corpus

Inferring the mammal tree: Species-level sets of phylogenies for questions in ecology, evolution, and conservation (2019, background): “estimates closer to the strict fossil age of approximately 166 Ma [66].”
A Brief History of South American Metatherians: Evolutionary Contexts and Intercontinental Dispersals (2016, background): “In addition, some South American notoungulates have been proposed as having Afrotherian affinities (Agnolin and Chimento 2011; O’Leary et al. 2013), but this has been soundly discounted by López et al.”
Morphology should not be forgotten in the era of genomics—a phylogenetic perspective (2015, background): “ 151 Fossils constitute a key element for understanding the phylogenies of many animal 152 groups (Donoghue et al., 1989; Edgecombe, 2010; Wiens, 2004), from placental mammals 153 (O'Leary et al., 2013) to early panarthropods (Legg et al., 2013).”
What do we know about armadillos? An analysis of four centuries of knowledge about a group of South American mammals, with emphasis on their conservation (2014, neutral): “Together with sloths (Folivora) and anteaters (Vermilingua) they form the Xenarthra, a mono-phyletic clade restricted to the Americas, which is considered to be one of the four major clades of placental mammals (Patterson & Pascual 1972, Delsuc et al. 2002, O’Leary et al. 2013).”
Bat Systematics in the Light of Unconstrained Analyses of a Comprehensive Molecular Supermatrix (2018, background): “…of Natural History (AMNH), Division of Vertebrate Zoology, Department of Mammalogy, NY, USA et al. 2004; Meredith et al. 2011; dos Reis et al. 2012; O'Leary et al. 2013), which led to the conclusion that the historically recognized Chiroptera was among the most robustly supported clade of mammals,…”
Neural progenitors, neurogenesis and the evolution of the neocortex (2014, background): “Since its relatively recent evolutionary origin in the mammalian ancestor ∼220 million years ago (Meredith et al., 2011; O’Leary et al., 2013), the neocortex has undergone dramatic expansion, independently, in several mammalian lineages (Borrell and Reillo, 2012), reflecting a positive selection…”
Therian mammals experience an ecomorphological radiation during the Late Cretaceous and selective extinction at the K–Pg boundary (2016, background): “[5] conclude that placental mammals radiated extremely rapidly in the first 200 000–400 000 years after the K–Pg extinction event.”
Splendid Innovation: The Extinct South American Native Ungulates (2020, background): “O’Leary et al. (2013) did not include mioclaenids in their analysis but, as noted previously, did find a sister-group relationship between didolodontids and litopterns, with North American condylarths as more basal representatives of that clade (Figure 3c).”