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

  title={The Placental Mammal Ancestor and the Post–K-Pg Radiation of Placentals},
  author={Maureen A. O'Leary and Jonathan I. Bloch and John J. Flynn and Timothy J. Gaudin and Andres Giallombardo and Norberto Pedro Giannini and Suzann L. Goldberg and Brian P. Kraatz and Zhe‐Xi Luo and Jin Meng and Xijun Ni and Michael J. Novacek and Fernando Ara{\'u}jo Perini and Zachary S Randall and Guillermo W. Rougier and Eric J. Sargis and Mary T. Silcox and Nancy B. Simmons and Michelle Spaulding and Pa{\'u}l M. Velazco and Marcelo Weksler and John R. Wible and Andrea L. Cirranello},
  pages={662 - 667}
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… 

Genomic evidence reveals a radiation of placental mammals uninterrupted by the KPg boundary

It is demonstrated that reconciliation between molecular and paleontological estimates of placental divergence times can be achieved using the appropriate clock model and gene partitioning scheme while accounting for the degree to which individual genes violate molecular clock assumptions.

Evolutionary Models for the Diversification of Placental Mammals Across the KPg Boundary

The strengths and weaknesses of different timetree methods that may now be applied to estimate the timing of the placental radiation are examined and the complexities of timetree estimation when the signal of speciation times is impacted by incomplete lineage sorting (ILS) and hybridization.

Combined data analysis of fossil and living mammals: a Paleogene sister taxon of Placentalia and the antiquity of Marsupialia

P phylogenetic analyses of >6000 newly scored anatomical observations drawn from six untested fossils and added to the largest existing morphological matrix for mammals show the existence of a new eutherian sister clade to Placentalia, which is named and characterize and indicates that the sisterClade survived the KPg event to co‐exist in ancient ecosystems during the Paleogene radiation of placentals.

Rapid morphological evolution in placental mammals post-dates the origin of the crown group

It is shown that, independent of divergence dates, morphological rates of evolution were slow relative to molecular evolution during the initial divergence of Placentalia, but substantially increased during the origination of the extant orders, supporting a Late Cretaceous origin of crown placentals with an ordinal-level adaptive radiation in the early Paleocene.

Attenuated evolution of mammals through the Cenozoic

The rate of evolutionary change peaked around the time of the Cretaceous-Paleogene boundary and has general tapered off since then, whereas in some species such as rodents, morphological change appeared to be decoupled from taxonomic diversification.

The origin of placental mammal life histories

The findings suggest that the ability to produce well-developed, precocial young was established early in placental evolution, and that larger neonate sizes were a possible mechanism for rapid size increase in early placentals.

Placenta-Specific Protein 1 Is Conserved throughout the Placentalia under Purifying Selection

  • E. Devor
  • Biology
  • 2014
A phylogenetic analysis of the PLAC1 protein in 25 placental mammal species suggests that this protein was present in the placental common ancestor in the form the authors see it today, that it evolved in the Placentalia and has been subject to the effects of purifying selection since its appearance.

The Interrelationships of Placental Mammals and the Limits of Phylogenetic Inference

This work shows that the root of Placentalia lies between Atlantogenata and Boreoeutheria, and finds evidence for ILS in early placental evolution, and is able to reject previous conclusions that the placental root is a hard polytomy that cannot be resolved.

Eutherians experienced elevated evolutionary rates in the immediate aftermath of the Cretaceous–Palaeogene mass extinction

It is shown that Placentalia likely originated in the Late Cretaceous, but that most intraordinal diversification occurred during the earliest Palaeocene, supporting the view that an evolutionary radiation occurred as placental lineages invaded new ecological niches during the EarlyPalaeocene.

Neither phylogenomic nor palaeontological data support a Palaeogene origin of placental mammals

A 20 million nucleotide genome-scale alignment in conjunction with a probabilistic interpretation of the fossil ages from O'Leary et al. demonstrates that Placentalia originated in the Cretaceous.



Placental mammal diversification and the Cretaceous–Tertiary boundary

The largest available molecular data set for placental mammals is investigated, which includes segments of 19 nuclear and three mitochondrial genes for representatives of all extant placental orders and permits simultaneous constraints from the fossil record and allows rates of molecular evolution to vary on different branches of a phylogenetic tree.

Molecular phylogenetics and the origins of placental mammals

The potential weaknesses of limited character and taxon sampling are addressed in a comprehensive molecular phylogenetic analysis of 64 species sampled across all extant orders of placental mammals, providing new insight into the pattern of the early placental mammal radiation.

Evolution of the mammalian placenta revealed by phylogenetic analysis.

Using phylogenetic and statistical analyses of molecular and morphological data, it is demonstrated that the ancestral eutherian mammalian placenta had the distinctive features of (i) hemochorial placental interface, (ii) a discoid shape, and (iii) a labyrinthine maternofetal interdigitation.

Cretaceous eutherians and Laurasian origin for placental mammals near the K/T boundary

The discovery of a new well-preserved mammal from the Late Cretaceous of Mongolia and a broad-scale phylogenetic analysis that includes all well-known CRETaceous fossils and a wide sample of morphology among Tertiary and recent placentals are reported.

Quantitative Analysis of the Timing of the Origin and Diversification of Extant Placental Orders

Although the fossil record is incomplete, it appears adequate to reject the hypothesis that orders of placentals began to diversify before the K/T boundary; thus, early Tertiary ordinal diversification is real.

Impacts of the Cretaceous Terrestrial Revolution and KPg Extinction on Mammal Diversification

Molecular phylogenetic analysis, calibrated with fossils, resolves the time frame of the mammalian radiation and diversification analyses suggest important roles for the Cretaceous Terrestrial Revolution and KPg mass extinction in opening up ecospace that promoted interordinal and intraordinal diversification, respectively.

Resolution of the Early Placental Mammal Radiation Using Bayesian Phylogenetics

Crown-group Eutheria may have their most recent common ancestry in the Southern Hemisphere (Gondwana), and placental phylogeny is investigated using Bayesian and maximum-likelihood methods and a 16.4-kilobase molecular data set.

The earliest known eutherian mammal

The skeleton of a eutherian (placental) mammal found in northeastern China has limb and foot features that are known only from scansorial and arboreal extant mammals, in contrast to the terrestrial or cursorial features of other Cretaceous eutherians.

A Jurassic eutherian mammal and divergence of marsupials and placentals

This mammal has scansorial forelimb features, and provides the ancestral condition for dental and other anatomical features of eutherians, reducing and resolving a discrepancy between the previous fossil record and the molecular estimate for the placental–marsupial divergence.