| Boreoeutheria
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| From top to right: European hedgehog, Lyle's flying fox, Siberian tiger, Indian pangolin, red deer and white rhino. Representing the orders: Eulipotyphla, Chiroptera, Carnivora, Pholidota, Artiodactyla and Perissodactyla, comprising Laurasiatheria. | |
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| From top to left: Sunda colugo, Desmarest's hutia, lar gibbon, European hare, brown rat, common treeshrew, ring-tailed lemur, and human playing with a rabbit. Representing the orders: Dermoptera, Rodentia, Primates, Lagomorpha, and Scandentia, comprising Euarchontoglires. | |
Scientific classification 
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Clade: | Eutheria |
| Infraclass: | Placentalia |
| Magnorder: | Boreoeutheria Springer & de Jong, 2001;[1] Murphy et al., 2001[2] |
| Superorders | |
| Synonyms | |
Boreoeutheria (/boʊˌriːoʊjuːˈθɛriə/, "northern true beasts") is a magnorder of placental mammals that groups together superorders Euarchontoglires and Laurasiatheria.[1][2][5] With a few exceptions,[a] male boreoeutherians have a scrotum, an ancestral feature of the clade.[6][7] The sub-clade Scrotifera was named after this feature.[8]
The name of this magnorder comes from Ancient Greek words:
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.[9][10] 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.[9] 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.[11][12] 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.[11]
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.[4][9][10][13][14][15][16]
Between these branches, however, is where it gets interesting, for there are numerous groups, our descended but a-scrotal 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 ... , 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.
The name comes from the word scrotum a pouch in which the testes permanently reside in the adult male. All members of the group have a postpenile scrotum, often prominently displayed, except for some aquatic forms and pangolins (which have the testes just below the skin). It appears to be an ancestral character for this group, yet other orders generally lack this as an ancestral feature, with the probable exception of Primates.
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Extant mammal orders
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| Yinotheria |
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| Theria |
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| Boreoeutheria |
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