Scrotifera

Scrotifera ("scrotum bearers") is a clade of placental mammals that groups together grandorder Ferungulata, Chiroptera (bats), other extinct members and their common ancestors. The clade Scrotifera is a sister group to the order Eulipotyphla (true insectivores) based on evidence from molecular phylogenetics,^[2] and together they make superorder Laurasiatheria. The last common ancestor of Scrotifera is supposed to have diversified ca. 73.1^[4] to 85.5^[5] million years ago.

Scrotifera Temporal range: 66.3–0 Ma[1] PreꞒ Ꞓ O S D C P T J K Pg N Late Cretaceous to present
From top to right: tiger, Indian pangolin, red deer, white rhino and Lyle's flying fox. Representing the living orders: Carnivora, Pholidota, Artiodactyla, Perissodactyla and Chiroptera, comprising Scrotifera.
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Superorder:	Laurasiatheria
Clade:	Scrotifera Waddell et al., 1999[2]
Subgroups
[see classification]
Synonyms
Variamana (Springer, 2005)[3]

Etymology

Peter Waddell, then of the Institute of Statistical Mathematics, explains the etymology of the clade's name as follows:

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 pangolin (which has 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.^[2]

Classification and phylogeny

History of phylogeny

In 2006, the clade Pegasoferae (a clade of mammals that includes orders Chiroptera, Carnivora, Perissodactyla and Pholidota) was proposed as part of the clade Scrotifera and a sister group to the order Artiodactyla, based on genomic research in molecular systematics.^[6] The monophyly of the group is not well supported, and recent studies have indicated that this clade is not a natural grouping.^[5][7]

According to a 2022 study, two extinct species (Eosoricodon terrigena and "Wyonycteris" microtis) were identified as outside of the family Nyctitheriidae and more closely related mammals to bats.^[8] In another 2022 study, the extinct genus Acmeodon was recognized as not a member of the extinct order Cimolesta but a basal laurasiatherian mammal in the clade Scrotifera.^[9][10]

Taxonomy

Former classification (Nishihara, 2006):

Current classification:

Clade: Scrotifera (Waddell, 1999) Order: Artiodactyla (Owen, 1848) (even-toed ungulates) Clade: Pegasoferae (Nishihara, 2006) Order: Chiroptera (Blumenbach, 1779) (bats) Clade: Zooamata (Waddell, 1999) Miroder: Ferae (Linnaeus, 1758) Order: Perissodactyla (Owen, 1848) (odd-toed ungulates)

Clade: Scrotifera (Waddell, 1999) Grandorder: Ferungulata (Simpson, 1945) Mirorder: Ferae (Linnaeus, 1758) Clade: Pan-Euungulata (O'Leary, 2013) Clade: Apo-Chiroptera (Cirranello, Simmons & Gunnell, 2020) (bats) Family: †Eosoricodontidae (Lopatin, 2005) Genus: †Acmeodon (Matthew & Granger, 1921) Genus: †Avunculus (Van Valen, 1966) Genus: †Gelastops (Simpson, 1935) Incertae sedis: †"Wyonycteris" microtis (Secord, 2008)

See also

• Mammal classification
• Laurasiatheria