Scrotifera ("scrotum bearers") is a

clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

placental mammals Placental mammals ( infraclass Placentalia ) are one of the three extant subdivisions of the class Mammalia, the other two being Monotremata and Marsupialia. Placentalia contains the vast majority of extant mammals, which are partly distinguish ...

that groups together grandorder

Ferungulata Ferungulata (" wild beasts and ungulates") is a grandorder of placental mammals that groups together mirorder Ferae and clade Pan-Euungulata. It has existed in two guises, a traditional one based on morphological analysis and a revised one ta ...

Chiroptera Bats are flying mammals of the order Chiroptera (). With their forelimbs adapted as wings, they are the only mammals capable of true and sustained flight. Bats are more agile in flight than most birds, flying with their very long spread-out ...

(bats), other extinct members and their common ancestors. The clade Scrotifera is a sister group to the order

Eulipotyphla Eulipotyphla (, from '' eu-'' + '' Lipotyphla'', meaning truly lacking blind gut; sometimes called true insectivores) is an order of mammals comprising the Erinaceidae ( hedgehogs and gymnures); Solenodontidae (solenodons); Talpidae ( mole ...

(true insectivores) based on evidence from

molecular phylogenetics Molecular phylogenetics () is the branch of phylogeny that analyzes genetic, hereditary molecular differences, predominantly in DNA sequences, to gain information on an organism's evolutionary relationships. From these analyses, it is possible to ...

, and together they make superorder

Laurasiatheria Laurasiatheria (; "Laurasian beasts") is a superorder of Placentalia, placental mammals that groups together true insectivores (eulipotyphlans), bats (chiropterans), carnivorans, pangolins (Pholidota, pholidotes), even-toed ungulates (Artiodacty ...

. The

last common ancestor A most recent common ancestor (MRCA), also known as a last common ancestor (LCA), is the most recent individual from which all organisms of a set are inferred to have descended. The most recent common ancestor of a higher taxon is generally assu ...

of Scrotifera is supposed to have diversified ca. 73.1 to 85.5 million years ago.

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 In most terrestrial mammals, the scrotum (: scrotums or scrota; possibly from Latin ''scortum'', meaning "hide" or "skin") or scrotal sac is a part of the external male genitalia located at the base of the penis. It consists of a sac of skin ...
'', a pouch in which the
testes A testicle or testis ( testes) is the gonad in all male bilaterians, including humans, and is homologous to the ovary in females. Its primary functions are the production of sperm and the secretion of androgens, primarily testosterone. The ...
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 Pangolins, sometimes known as scaly anteaters, are mammals of the order Pholidota (). The one extant family, the Manidae, has three genera: '' Manis'', '' Phataginus'', and '' Smutsia''. ''Manis'' comprises four species found in Asia, while ' ...
(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
Primate Primates is an order (biology), order of mammals, which is further divided into the Strepsirrhini, strepsirrhines, which include lemurs, galagos, and Lorisidae, lorisids; and the Haplorhini, haplorhines, which include Tarsiiformes, tarsiers a ...
s.

Classification and phylogeny

History of phylogeny

In 2006, the clade Pegasoferae (a clade of mammals that includes orders Chiroptera,

Carnivora Carnivora ( ) is an order of placental mammals specialized primarily in eating flesh, whose members are formally referred to as carnivorans. The order Carnivora is the sixth largest order of mammals, comprising at least 279 species. Carnivor ...

Perissodactyla Perissodactyla (, ), or odd-toed ungulates, is an order of ungulates. The order includes about 17 living species divided into three families: Equidae (horses, asses, and zebras), Rhinocerotidae (rhinoceroses), and Tapiridae (tapirs). They t ...

and

Pholidota Pangolins, sometimes known as scaly anteaters, are mammals of the order Pholidota (). The one Neontology, extant family, the Manidae, has three genera: ''Manis'', ''Phataginus'', and ''Smutsia''. ''Manis'' comprises four species found in Asia, ...

) was proposed as part of the clade Scrotifera and a sister group to the order

Artiodactyla Artiodactyls are placental mammals belonging to the order (biology), order Artiodactyla ( , ). Typically, they are ungulates which bear weight equally on two (an even number) of their five toes (the third and fourth, often in the form of a hoof ...

, based on genomic research in molecular systematics. The monophyly of the group is not well supported, and recent studies have indicated that this clade is not a natural grouping. According to a 2022 study, two extinct species ('' Eosoricodon terrigena'' and '' "Wyonycteris" microtis'') were identified as outside of the family

Nyctitheriidae Nyctitheriidae is a family of extinct eulipotyphlan insectivores known from the Paleocene and Eocene Epoch, epochs of North America and Asia and persisting into the Oligocene of Europe. Several genera, including ''Nyctitherium'', ''Paradoxonycter ...

and more closely related mammals to bats. In another 2022 study, the extinct genus '' Acmeodon'' was recognized as not a member of the extinct order

Cimolesta Cimolesta is an extinct order of non-placental eutherian mammals. Cimolestans had a wide variety of body shapes, dentition and lifestyles, though the majority of them were small to medium-sized general mammals that bore superficial resemblances t ...

but a basal

laurasiatheria Laurasiatheria (; "Laurasian beasts") is a superorder of Placentalia, placental mammals that groups together true insectivores (eulipotyphlans), bats (chiropterans), carnivorans, pangolins (Pholidota, pholidotes), even-toed ungulates (Artiodacty ...

n mammal in the clade Scrotifera.

Taxonomy

References

{{Taxonbar, from=Q7439311 Mammal taxonomy Extant Paleocene first appearances

Etymology

Classification and phylogeny

History of phylogeny

Taxonomy

See also

References