''Eoscansor'' (EE-oh-SKAN-sor; meaning "dawn climber") is a species of small

varanopid Varanopidae is an extinct family of amniotes that resembled monitor lizards and may have filled a similar niche, hence the name. Typically, they are considered synapsids that evolved from an ''Archaeothyris''-like synapsid in the Late Carbonifero ...

amniote Amniotes are a clade of tetrapod vertebrates that comprises sauropsids (including all reptiles and birds, and extinct parareptiles and non-avian dinosaurs) and synapsids (including pelycosaurs and therapsids such as mammals). They are disti ...

that lives from the upper Pennsylvanian subperiod in northern

New Mexico, United States ) , population_demonym = New Mexican ( es, Neomexicano, Neomejicano, Nuevo Mexicano) , seat = Santa Fe , LargestCity = Albuquerque , LargestMetro = Tiguex , OfficialLang = None , Languages = English, Spanish ( New Mexican), Navajo, Ker ...

305 million years ago. The species ''Eoscansor cobrensis'' was 24.5 centimeters (9.6 inches) long and weighed 58.3 grams. The tetrapods teeth indicated that it was insectivorous. The small size and grasping limbs means that was ''E. cobrensis'' highly agile and likely

arboreal Arboreal locomotion is the Animal locomotion, 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, but others are exclusively arboreal. Th ...

(tree climbing). The name ''Eoscansor'' means "dawn climber", derived from

Greek Greek may refer to: Greece 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 ...

with "Eo" meaning dawn and "scansor" meaning climber. ''E. cobrensis'' is currently the oldest specialised climbing tetrapod animal pushing back the original record by 15 million years. The species was discovered in the

El Cobre Canyon Formation The El Cobre Canyon Formation is a geologic formation in New Mexico. It preserves fossils dating back to the late Pennsylvanian to early Permian periods. Description The El Cobre Canyon Formation consists of siliciclastic red beds with a total t ...

in northern

New Mexico ) , population_demonym = New Mexican ( es, Neomexicano, Neomejicano, Nuevo Mexicano) , seat = Santa Fe , LargestCity = Albuquerque , LargestMetro = Tiguex , OfficialLang = None , Languages = English, Spanish ( New Mexican), Navajo, Ker ...

near the village of Chama in 2005 but was not prepared until 2015. The

COVID-19 pandemic The COVID-19 pandemic, also known as the coronavirus pandemic, is an ongoing global pandemic of coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The novel virus was first identif ...

in 2020 pushed study back until 2022 where it was described as a new genus and species. ''Eoscansor'' fossil holotype (NMMHS P-75122) is part of the

New Mexico Museum of Natural History and Science The New Mexico Museum of Natural History and Science is a natural history and science museum in Albuquerque, New Mexico near Old Town Albuquerque. The Museum was founded in 1986. It operates as a public revenue facility of the New Mexico Departmen ...

(NMMNHS) collection. The holotype specimen of ''E. cobrensis'' is incomplete. Preserved skeletal remains consist of some

skull The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, the ...

fragments, an incomplete

dentary In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower tooth, teeth in place. The mandible sits beneath the maxilla. It is the only movabl ...

with several

teeth A tooth ( : teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, tear ...

atlas An atlas is a collection of maps; it is typically a bundle of maps of Earth or of a region of Earth. Atlases have traditionally been bound into book form, but today many atlases are in multimedia formats. In addition to presenting geographic ...

axis An axis (plural ''axes'') is an imaginary line around which an object rotates or is symmetrical. Axis may also refer to: Mathematics * Axis of rotation: see rotation around a fixed axis *Axis (mathematics), a designator for a Cartesian-coordinate ...

. The fossil includes two anterior vertebrae and at least ten

dorsal vertebrae In vertebrates, thoracic vertebrae compose the middle segment of the vertebral column, between the cervical vertebrae and the lumbar vertebrae. In humans, there are twelve thoracic vertebrae and they are intermediate in size between the cervical ...

, eight

caudal vertebrae The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic ...

, incomplete

interclavicle An interclavicle is a bone which, in most tetrapods, is located between the clavicles. Therian mammals ( marsupials and placentals) are the only tetrapods which never have an interclavicle, although some members of other groups also lack one. In th ...

, parts of both

clavicle The clavicle, or collarbone, is a slender, S-shaped long bone approximately 6 inches (15 cm) long that serves as a strut between the shoulder blade and the sternum (breastbone). There are two clavicles, one on the left and one on the rig ...

rib In vertebrate anatomy, ribs ( la, costae) are the long curved bones which form the rib cage, part of the axial skeleton. In most tetrapods, ribs surround the chest, enabling the lungs to expand and thus facilitate breathing by expanding the ches ...

bones and

gastralia Gastralia (singular gastralium) are dermal bones found in the ventral body wall of modern crocodilians and tuatara, and many prehistoric tetrapods. They are found between the sternum and pelvis, and do not articulate with the vertebrae. In these ...

humeri The humerus (; ) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius and ulna, and consists of three sections. The humeral upper extremity consists of a round ...

, right raidus,

ulna The ulna (''pl''. ulnae or ulnas) is a long bone found in the forearm that stretches from the elbow to the smallest finger, and when in anatomical position, is found on the medial side of the forearm. That is, the ulna is on the same side of t ...

e, partial left and right manus and left ilium. The skeleton also includes a

ischium The ischium () form ...

, pubis,

femora The femur (; ), or thigh bone, is the proximal bone of the hindlimb in tetrapod vertebrates. The head of the femur articulates with the acetabulum in the pelvic bone forming the hip joint, while the distal part of the femur articulates with t ...

(~22mm),

tibia The tibia (; ), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outside of the tibia); it connects ...

fibula The fibula or calf bone is a leg bone on the lateral side of the tibia, to which it is connected above and below. It is the smaller of the two bones and, in proportion to its length, the most slender of all the long bones. Its upper extremity is ...

e and both left and right incomplete pedes.

References

{{Taxonbar, from=Q113124883 Varanopids Fossil taxa described in 2022