Tag: Gregory Wilson Mantilla

Which group of mammals has the more “primitive” reproductive strategy — marsupials, with their short gestation periods, or humans and other placental mammals, which have long gestation periods? For decades, biologists viewed marsupial reproduction as “more primitive.” But University of Washington scientists have discovered that a third group of mammals, the long-extinct multituberculates, had a long gestation period like placental mammals. Since multituberculates split off from the rest of the mammalian lineage before placentals and marsupials had even evolved, these findings question the view that marsupials were “less advanced” than their placental cousins.

A team of paleontologists from the University of Washington and its Burke Museum of Natural History and Culture excavated four dinosaurs in northeastern Montana this summer. The four dinosaur fossils are: the ilium — or hip bones — of an ostrich-sized theropod, the group of meat-eating, two-legged dinosaurs that includes Tyrannosaurus rex and raptors; the hips and legs of a duck-billed dinosaur; a pelvis, toe claw and limbs from another theropod that could be a rare ostrich-mimic Anzu, or possibly a new species; and a Triceratops specimen consisting of its skull and other fossilized bones.

A new study published Feb. 24 in the journal Royal Society Open Science documents the earliest-known fossil evidence of primates. These creatures lived less than 150,000 years after the Cretaceous-Paleogene mass extinction event that killed off non-avian dinosaurs and saw the rise of mammals.

A new study led by paleontologists at the University of Washington indicates that the earliest evidence of mammal social behavior goes back to the Age of Dinosaurs. A multituberculate that lived 75.5 million years ago, Filikomys primaevus engaged in multi-generational, group-nesting and burrowing behavior, and possibly lived in colonies.