Boreoeutheria Explained

Boreoeutheria ("northern true beasts") is a magnorder of placental mammals that groups together superorders Euarchontoglires and Laurasiatheria.[1] With a few exceptions,[2] male boreoeutherians have a scrotum, an ancestral feature of the clade.[3] [4] The sub-clade Scrotifera was named after this feature.[5]

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.[6] [7] 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.[6] 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.[8] [9] 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.[8]

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.[10] [11] [12] [13] [14]

See also

References

Additional references

External links

Notes and References

  1. Scally M, Madsen O, Douady CJ, de Jong WW, Stanhope MJ, Springer MS . 2001 . Molecular evidence for the major clades of placental mammals . Journal of Mammalian Evolution . 8 . 4 . 239–277. 10.1023/A:1014446915393 . 24199924 .
  2. Exceptional clades whose males lack the usual boreoeutherian scrotum are moles, hedgehogs, pangolins, some pinnipeds, rhinoceroses, tapirs, hippopotamuses, and cetaceans.
  3. Book: Mills . D. S. . Marchant-Forde . Jeremy N. . The Encyclopedia of Applied Animal Behaviour and Welfare . 20 June 2019 . 2010 . CABI . 978-0-85199-724-7 . 293.
  4. Web site: Drew . Liam . Why are testicles kept in a vulnerable dangling sac? . 8 July 2013 . slate.com . 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..
  5. Waddell . 1999 . Using novel phylogenetic methods to evaluate mammalian mtDNA, including amino acid-invariant sites-LogDet plus site stripping, to detect internal conflicts in the data, with special reference to the positions of hedgehog, armadillo, and elephant . . 48 . 1 . 31–53 . 10.1080/106351599260427 . 12078643 . etal . 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. . free.
  6. Zhou . X. . Xu . S. . Xu . J. . Chen . B. . Zhou . K. . Yang . G. . Phylogenomic Analysis Resolves the Interordinal Relationships and Rapid Diversification of the Laurasiatherian Mammals . Systematic Biology . 61 . 1 . 2012 . 1063-5157 . 10.1093/sysbio/syr089 . 150–164. 21900649 . 3243735 .
  7. O'Leary . M. A. . Bloch . J. I. . Flynn . J. J. . Gaudin . T. J. . Giallombardo . A. . Giannini . N. P. . Cirranello . A. L. . 206544776 . 2013 . The placental mammal ancestor and the post–K-Pg radiation of placentals . Science . 339 . 6120 . 662–667 . 10.1126/science.1229237 . 23393258. 2013Sci...339..662O . 11336/7302 . free.
  8. Web site: Scientists recreate genome of ancient human ancestor . https://web.archive.org/web/20060321235843/http://news.nationalgeographic.com/news/2005/01/0125_050125_genome_2.html . dead . March 21, 2006 . . John Roach . 25 Jan 2005 . 14 Feb 2015.
  9. Mathieu Blanchette . Eric D. Green . Webb Miller . David Haussler . 2004 . Reconstructing large regions of an ancestral mammalian genome in silico . . 10.1101/gr.2800104 . 14 . 12 . 2412–2423 . 15574820 . 534665.
  10. Waddell . Peter J. . Kishino . Hirohisa . Ota . Rissa . 2001 . A phylogenetic foundation for comparative mammalian genomics . . 12 . 141–154 . 11791233 . 2021-08-09 . 2019-07-10 . https://web.archive.org/web/20190710063147/https://www.jsbi.org/pdfs/journal1/GIW01/GIW01F15.html . dead .
  11. Foley . Nicole M. . Springer . Mark S. . Teeling . Emma C. . 2016-07-19 . Mammal madness: Is the mammal tree of life not yet resolved? . Philosophical Transactions of the Royal Society B . 371 . 1699 . 20150140 . 10.1098/rstb.2015.0140 . 0962-8436 . 4920340 . 27325836 . dmy-all.
  12. Esselstyn . Jacob A. . Oliveros . Carl H. . Swanson . Mark T. . Faircloth . Brant C. . 2017-08-26 . Investigating Difficult Nodes in the Placental Mammal Tree with Expanded Taxon Sampling and Thousands of Ultraconserved Elements . Genome Biology and Evolution . en . 9 . 9 . 2308–2321 . 10.1093/gbe/evx168 . 1759-6653 . 5604124 . 28934378.
  13. Frank Zachos (2020.) "Mammalian Phylogenetics: A Short Overview of Recent Advances", In book: "Mammals of Europe - Past, Present, and Future" (pp.31-48)
  14. Xue Lv, Jingyang Hu, Yiwen Hu, Yitian Li, Dongming Xu, Oliver A. Ryder, David M. Irwin, Li Yu (2021.) "Diverse phylogenomic datasets uncover a concordant scenario of laurasiatherian interordinal relationships", Molecular Phylogenetics and Evolution, Volume 157

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