ZooKeys 465: The Origin and Early Evolution of Metatherian Mammals The Cretaceous record

About this book

This is a review of Cretaceous metatherian mammals, the group that includes marsupials and their closest relatives, which was one of the most dominant groups of mammals near the end of the Mesozoic.

Metatherians, the group of mammals most closely related to placental mammals, and which today is represented by marsupials, enjoyed a long and complex history during the Cretaceous. Metatherians differ from placental mammals in giving birth to extremely poorly-developed young followed by an extended period of suckling. This distinctive process is reflected in their dental formula and tooth replacement pattern. Metatherian mammals were present throughout the northern continents through the Cretaceous, but were especially abundant in the Late Cretaceous of western North America, where they are represented chiefly by fossil jaws and teeth. Here we provide a review of the phylogenetic relationships of metatherians with respect to other mammals, discuss the taxonomic definition and diagnosis of Metatheria, outline the Cretaceous history of major metatherian clades, describe the paleobiology, biogeography, and macroevolution of Cretaceous metatherians, and provide a physical and climatic background of Cretaceous metatherian faunas. During the Late Cretaceous, terrestrial ecosystems went through radical changes as flowering plants, the angiosperms, rapidly diversified. However, the pattern of metatherian diversity during this interval does not closely track that of angiosperms. Metatherians were diverse in the latest Cretaceous of North America, but underwent a profound extinction at the end of the Cretaceous. Only a few lineages of metatherians survived into the Paleogene.

Contents

Introduction   3
The taxonomic and evolutionary context of Metatheria   4
Mammalia   4
Boreosphenida   6
Theria   8
Metatheria   8
Definition   8
Diagnosis   8
A survey of Cretaceous metatherian taxa   12
Sinodelphys   13
Deltatheroida   14
Marsupialiformes   14
Basal stem marsupialiforms   15
Stagodontidae   16
Pediomyidae   16
Glasbiidae   17
Herpetotheriidae   18
Peradectidae   19
A note on metatherian taxonomy    9
Phylogenetic analysis   21
Results of phylogenetic analysis   22
Osteology of Metatheria   24
Skull   25
Postcrania   27
Dating the origin and evolution of Metatheria   36
Molecular evidence   36
Paleontological evidence   36
Summary   37
Geologic setting and paleoenvironment of Cretaceous Metatheria   38
Paleobiology   45
Cretaceous paleobiogeography   48
Macroevolution, diversification, and extinction patterns   53
Phylogenetic evidence for macroevolutionary patterns   56

Acknowledgements   57
References   57

Supplementary material 1   75
Supplementary material 2   75
Supplementary material 3   75
Supplementary material 4   76
Supplementary material 5   76

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