Boreoeutheria (, "northern true beasts") is a magnorder of placental mammals that groups together superorders Euarchontoglires and Laurasiatheria. With a few exceptions, male boreoeutherians have a scrotum, an ancestral feature of the clade. The sub-clade Scrotifera was named after this feature.

Etymology

The name of this magnorder comes from Ancient Greek words:

Boreoeutherian ancestor

The majority of earliest known fossils belonging to this group date to about 66 million years ago, shortly after the K-Pg extinction event, though molecular data suggest they may have originated earlier, during the Cretaceous period. This is further supported with fossils of Altacreodus magnus and two species from genus Protungulatum dated about 70.6 million years ago. The common ancestor of Boreoeutheria lived between 107 and 90 million years ago. The boreoeutherian ancestor gave rise to species as diverse as giraffes, pigs, zebras, rhinos, dogs, cats, rabbits, mice, squirrels, bats, whales, dolphins, lemurs, monkeys, and humans. The concept of a boreoeutherian ancestor was first proposed in 2004 in the journal Genome Research. The paper's authors claimed that the genome sequence of the boreoeutherian ancestor could be computationally predicted with 98% accuracy, but would "take a few years and a lot of money". It is estimated to contain three billion base pairs.

Classification and phylogeny

Taxonomy

Phylogeny

The phylogenetic relationships of magnorder Boreoeutheria are shown in the following cladogram, reconstructed from mitochondrial and nuclear DNA and protein characters, as well as the fossil record.

Additional references