''Unguinychus'' (meaning "claw claw") is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

genus of drepanosaurid reptiles from the

Late Triassic The Late Triassic is the third and final epoch (geology), epoch of the Triassic geologic time scale, Period in the geologic time scale, spanning the time between annum, Ma and Ma (million years ago). It is preceded by the Middle Triassic Epoch a ...

Garita Creek Formation The Garita Creek Formation is a geologic formation in New Mexico that contains vertebrate fossils characteristic of the Carnian Age of the late Triassic .Lucas and Hunt 1989 The formation may be synonymous with the Tecovas Formation in Texas. ...

of New Mexico, United States. The genus contains a single species, ''U. onyx'', known from several partial claws. In contrast to some of its relatives that may have been

arboreal Arboreal locomotion is the locomotion of animals in trees. In habitats in which trees are present, animals have evolved to move in them. Some animals may scale trees only occasionally (scansorial), but others are exclusively arboreal. The hab ...

, ''Unguinychus'' may have been a more

fossorial A fossorial animal () is one that is adapted to digging and which lives primarily (but not solely) underground. Examples of fossorial vertebrates are Mole (animal), moles, badgers, naked mole-rats, meerkats, armadillos, wombats, and mole salamand ...

species. Based on the morphology of the claws, ''Unguinychus'' appears to be most similar to ''

Skybalonyx ''Skybalonyx'' is an extinct genus of drepanosaur from the Chinle Formation in the Late Triassic. The type and only known species is ''Skybalonyx skapter'', meaning "digging dung claw" from Ancient Greek, in reference to the association of this t ...

'', another possibly fossorial drepanosaur from the

Chinle Formation The Chinle Formation is an Upper Triassic continental geological formation of fluvial, lacustrine, and palustrine to eolian deposits spread across the U.S. states of Nevada, Utah, northern Arizona, western New Mexico, and western Colorado. In ...

of Arizona.

Discovery and naming

The ''Unguinychus'' fossil material, was discovered in sediments of the

(Homestead Site) on a

cattle ranch A ranch (from /Mexican Spanish) is an area of landscape, land, including various structures, given primarily to ranching, the practice of raising grazing livestock such as cattle and sheep. It is a subtype of farm. These terms are most often ap ...

in San Miguel County, New Mexico. The

holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

specimen, LF 5575, consists of a manual

ungual An ungual (from Latin ''unguis'', i.e. ''nail'') is a highly modified distal toe bone which ends in a hoof, claw, or nail. Elephants and ungulates have ungual phalanges, as did the sauropod Sauropoda (), whose members are known as sauropods (; ...

(hand claw) from the second digit, missing the tip. Nine other unguals—also missing their pointed tips—presumably from the second manual digit as well, were assigned to ''Unguinychus'' as

paratype In zoology and botany, a paratype is a specimen of an organism that helps define what the scientific name of a species and other taxon actually represents, but it is not the holotype (and in botany is also neither an isotype (biology), isotype ...

s. Other drepanosaurid fossil material was found at the same locality as ''Unguinychus'', including caudal unguals (tail claws) and fragmentary cervical,

dorsal Dorsal (from Latin ''dorsum'' ‘back’) may refer to: * Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism * Dorsal, positioned on top of an aircraft's fuselage The fus ...

, and

caudal vertebrae Caudal vertebrae are the vertebrae of the tail in many vertebrates. In birds, the last few caudal vertebrae fuse into the pygostyle, and in apes, including humans, the caudal vertebrae are fused into the coccyx. In many reptiles, some of the caud ...

. While these bones may also belong to ''Unguinychus'', Pugh et al. (2024) refrained from making this referral due to a lack of associated and overlapping skeletal material. In 2024, Pugh et al. described ''Unguinychus onyx'' as a new genus and species of drepanosaurid based on these fossil remains. The

binomial Binomial may refer to: In mathematics *Binomial (polynomial), a polynomial with two terms *Binomial coefficient, numbers appearing in the expansions of powers of binomials *Binomial QMF, a perfect-reconstruction orthogonal wavelet decomposition * ...

combines the

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

word "''unguis''", and the

Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...

words "''nychus''" and "''onyx''", all of which mean "claw". As such, the full scientific name means "claw claw claw", referencing the fact that unguals are the only known bone of the species.

References

{{Taxonbar, from=Q127789838 Drepanosauromorpha Fossil taxa described in 2024 Late Triassic reptiles of North America Paleontology in New Mexico Monotypic prehistoric reptile genera