Laurasiatheria: Overview

Taxa on This Page

1. Laurasiatheria

Descriptions

Laurasiatheria: Northern mammals and their descendents.

Comments: Laurasiatheria are, with Boreoeutheria, Euarchontaglires, Afrotheria, and Xenarthra, one of five major clades of eutherian mammals revealed through molecular phylogeny. Although they have become increasingly well resolved through gene sequencing studies, there is absolutely no morphological evidence in support of their status (in contrast to Xenarthra and, to a lesser extent, Euarchontaglires). As the name implies, they include placental mammals originating in the northern supercontinent of Laurasia (ditto their parent clade of Boreoeutheria, eutherians of the north). They include a total grab bag: insectivores, bats, pangolins, most hoofed mammals (and whales, already include dhere on paleontological grounds), and carnivorans.

Basing a clade purely on molecular evidence alone is problematic, as it assumes molecular sequencing has a more reliable phylogenetic signal than synapomorphy-based morphological analysis (cladistics). Such a claim may be true, or it may not; in any case it remains a hypothesis that has never been tested. Using cladistic analysis Wible et al 2007 and 2009 recovered three molecular clades - Euarchontaglires, Afrotheria, and Xenarthra - but found the Laurasiatheria as conventionally defined to be polyphyletic (insectivores are more derived than ferungulates), and the Boreoeutheria paraphyletic (representing a stepwise series to Atlantogenata (i.e. Afrotheria + Xenarthra) MAK120321

Image: Laurasiatheria as defined by molecular phylogeny include a highlty diverse range of mammals. This collage shows a giraffe (Giraffa camelopardalis angolensis) (Cetartiodactyla), Golden crowned fruit bat (Chiroptera), Hedgehog (Eulipotyphla), and Lion (Carnivora). Creative Commons Share Alike Attribution, via Wikipedia