''Cifelliodon'' is an extinct

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

mammaliaform Mammaliaformes ("mammalian forms") is a clade of synapsid tetrapods that includes the crown group mammals and their closest extinct relatives; the group radiated from earlier probainognathian cynodonts during the Late Triassic. It is defined a ...

s from the Lower Cretaceous of North America. In the describing paper, it was considered one of the latest surviving haramiyids yet known, belonging to the family Hahnodontidae. Its discovery led to the proposal to remove hahnodontids from the larger well-known group, the multituberculates. However, later papers have considered it to be a basal allotherian outside of Haramiyida. The sole species in the genus, ''Cifelliodon wahkarmoosuch'', was found in the geological rock unit called the Yellow Cat Member, part of the Cedar Mountain Formation in Grand County,

Utah Utah is a landlocked state in the Mountain states, Mountain West subregion of the Western United States. It is one of the Four Corners states, sharing a border with Arizona, Colorado, and New Mexico. It also borders Wyoming to the northea ...

. This rock unit dates to between 139-124 million years old. It was found alongside the remains of several dinosaurs - a large

iguanodon ''Iguanodon'' ( ; meaning 'iguana-tooth'), named in 1825, is a genus of iguanodontian dinosaur. While many species found worldwide have been classified in the genus ''Iguanodon'', dating from the Late Jurassic to Early Cretaceous, Taxonomy (bi ...

tian, a dromaeosaur, and an ornithopod - and parts of a crocodyliform.

Etymology

The genus name, ''Cifelliodon'', means Cifelli's tooth, and honours the well-known mammal palaeontologist, Richard Cifelli. The species name, ''C. wahkarmoosuch'' comes from the

Ute language Ute ( )Givón, T. ''Ute Reference Grammar''. John Benjamins Publishing Company, 2011 is a dialect of the Colorado River Numic language, spoken by the Ute people. Speakers primarily live on three reservations: Uintah-Ouray (or Northern Ute) in ...

, and means yellow () cat ().

Description

The holotype of ''Cifelliodon wahkarmoosuch'' is an exceptionally well-preserved skull, housed at the Natural History Museum of Utah. The skull measures 70 mm in length, giving an estimated body mass of 0.91-1.27 kg. The skull is broad and shallow with a reduced tooth count. There is a prominent

sagittal crest A sagittal crest is a ridge of bone running lengthwise along the midline of the top of the skull (at the sagittal suture) of many mammalian and reptilian skulls, among others. The presence of this ridge of bone indicates that there are excepti ...

. Inside the skull on each side are two incisors, a canine, and four postcanines, all of them broken off at the gumline except for the last molars. These last molars had not yet erupted, and so their intact crowns allowed palaeontologists to identify this mammaliaform. The preserved skull allowed palaeontologists to see the brain size of ''Cifelliodon'', and they concluded it was a transitional size and shape between earlier stem mammals, and crown mammals. It appears to have had a well-developed sense of smell, as did most mammals in the

Mesozoic The Mesozoic Era is the Era (geology), era of Earth's Geologic time scale, geological history, lasting from about , comprising the Triassic, Jurassic and Cretaceous Period (geology), Periods. It is characterized by the dominance of archosaurian r ...

Phylogeny

Previously, scientists had suggested that the hahnodontids belonged to the well-known group of mammals called multituberculates. However, examining the anatomy of ''Cifelliodon'', Huttenlocker et al. (2018) found it to be closely related to '' Hahnodon'', and placed them outside of Multituberculata and outside the crown mammals. This makes hahnodontids a late surviving stem mammal group. It also suggests that there were greater links between the tetrapod animals across the continents in the Cretaceous. Krause ''et al.'' (2020) recovered ''Cifelliodon'' as a basal member of

Allotheria Allotheria (meaning "other beasts", from the Ancient Greek language, Greek , '–other and , '–wild animal) is an extinct clade of mammals known from the Mesozoic and early Cenozoic. Shared characteristics of the group are the presence of lower ...

, outside of the clade containing Euharamiyida and 'Multituberculata + Gondwanatheria'. Their analysis did not include ''Hahnodon''.

References

{{Taxonbar, from=Q55391290 Haramiyida Prehistoric cynodont genera Early Cretaceous synapsids of North America Fossil taxa described in 2018 Taxa named by Adam K. Huttenlocker Taxa named by David M. Grossnickle Taxa named by James I. Kirkland Taxa named by Julia A. Schultz Taxa named by Zhe-Xi Luo