Temporal range: Early Paleocene - Holocene, 65–0 Ma
|European mole (Talpa europaea)|
Boreoeutheria (synonymous with Boreotheria) (Greek: βόρειο "north" + ευ "good" + θεριό "beast") is a clade (magnorder) of placental mammals that is composed of the sister taxa Laurasiatheria (most hoofed mammals, most pawed carnivores, and several other groups) and Euarchontoglires (Supraprimates). It is now well supported by DNA sequence analyses, as well as retrotransposon presence or absence data.
The earliest known fossils belonging to this group date to about 65 million years ago, shortly after the K-Pg extinction event, though molecular data suggest they may have originated earlier, during the Cretaceous period.
With the exceptions of moles, hedgehogs, pangolins, some seals and walruses, rhinoceroses, tapirs, hippopotamuses and cetaceans, male members of the clade share the distinction of external testicles which serve the function of cooling the testicles.
The common ancestor of Boreoeutheria lived between 100 and 80 million years ago. The boreoeutherian ancestor gave rise to species as diverse as giraffes, dogs, mice, bats, whales, and humans. The concept of 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.
- Magnorder Boreoeutheria
- Superorder Euarchontoglires (Supraprimates)
- Grandorder Euarchonta
- Grandorder Glires
- Superorder Laurasiatheria
- Order Eulipotyphla
- Order Cetartiodactyla: even-toed ungulates, including pigs, hippopotamus, camels, giraffe, deer, antelope, cattle, whales, dolphins, porpoises, etc.
- Suborder Tylopoda: camels and extinct relatives
- Suborder Suina: pigs,peccaries, and extinct relatives
- Suborder Ruminantia: cattle, sheep, goats, deer, antelope, etc.
- Suborder Whippomorpha: whales, dolphins, porpoises, and hippopotamuses
- Order Chiroptera: bats (cosmopolitan)
- Order Perissodactyla: odd-toed ungulates, including horses, donkeys, zebras, tapirs, rhinoceroses, and Chalicotheres (cosmopolitan)
- Clade Ferae
- Superorder Euarchontoglires (Supraprimates)
While it is agreed that the cetaceans evolved within artiodactyls, much of the branching order within Laurasiatheria is not yet well resolved. In particular, the most difficult order to place definitively has been and still is Perissodactyla: Their placement within Zooamata is controversial.
One study has suggested that the carnivores, cetaceans, chiroptera and ungulates form an ancient clade. This is supported by another study that suggests that Eulipotyphla are the earliest diverging clade within the Laurasiatheria.
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- Drew, Liam (8 July 2013). "Why are testicles kept in a vulnerable dangling sac?". slate.com. "Between these branches, however, is where it gets interesting, for there are numerous groups, our descended but ascrotal cousins, whose testes drop down away from the kidneys but don't exit the abdomen. Almost certainly, these animals evolved from ancestors whose testes were external, which means at some point they backtracked on scrotality, evolving anew gonads inside the abdomen. They are a ragtag bunch including hedgehogs, moles, rhinos and tapirs, hippopotamuses, dolphins and whales, some seals and walruses, and scaly anteaters."
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