Genus: Halgaitosaurus HENRICI, BERMAN, SUMIDA & HUTTENLOCKER, 2023
Etymology: In reference to the Halgaito Formation in which it was collected and Latin, sauros, "lizard."
= Araeoscelida n. sp HUTTENLOCKER, HENRICI, NELSON, ELRICK, BERMAN, SCHLOTTERBECK & SUMIDA, 2018

Species: gregarious HENRICI, BERMAN, SUMIDA & HUTTENLOCKER, 2023
Etymology: Latin, gregarius, pertaiing to flock or herd.

Holotype: CM 96000

Locality: Birthday bonebed (CM locality no. 3345), Valley of the Gods, Bears Ears National Monument, San Juan County, southeast Utah.

Horizon: Halgaito Formation, Cutler Group.

Biostratigraphy:

Age: Virgilian, Gzhelian Epoch, Late Pennsylvanian Subperiod, Latest Carboniferous Period.

Material: Right maxilla, right mandible, postfrontals, right jugal, left pterygoid, ectopterygoid and palatine, proatlases, atlantal centrum, axis, cervical, dorsal and caudal vertebrae, ribs, right scapulocoracoid, interclavicle, right humerus, radius, and ulna, femora, left fibula, right astragalus and calcaneum and metapodials. In Block H-3-91)

Referred material:

CM 8910 (H-1-90): Partial vertebral column, humerus, ulna, partial right manus, femur, partial right pes and most of which are weathered.

CM 89211 (H-1-90): Clavicle, scapulocoracoids, humeru, radii, left ulna, dorsal vertebrae, right pelvis, left femur, tibia and fibula.

CM 89212 (H-1-90): Right femur, fragmentry fibula, and other incompletely exposed limb bones.

CM 89213 (H-1-90): Incomplete left maxilla, disarticulated dorsal and caudal vertebrae, and incompletely exposed ulna and radius.

CM 90273 (H-3-90): Left premaxilla, right and left maxillae, left nasal, left postorbital and possible left jugal and right vomer.

CM 92600 (H-2C-15): Dorsal vertebra.

CM 96001(H-3-91): Incomplete left maxilla, left mandible, left frontal and left postfrontal.

CM 96003 (H-3-91): Right maxilla (very fragmentary), parietals, incomlpete pterygoid, vertebrae, and limb bones preserved nearby that might be associated.

CM 96004 (H-3-90): Parietals and everal cerical vertebrae.

CM 96005 (H-3-91): Left frontal, right jugal, left mandible and two cervical vertebrae that might be associated with the skull bones.

CM 96006 (H-1-90): Left and incomplete rigth maxillae, right pterygoid, right palatine, and other palatal bones too weathered to identified, dorsal vertebrae, ribs, and incomplete pelvis.

CM 96007 (H-1-90): Caudal vertebrae, pelvis (right incompletely exposed), femora, and tibia, fibula, astragalus, calcaneum, and phalanges.

CM 96008 (H-1-90): 9 dorsal vertebrae, puboischiadic plates, femora, left parietal tibia nd right proximal.

CM 96009 (H-1-90): Left tibia and fibula.

CM 96010 (H-1-90): Right ulna.

CM 96011 (H-1-90): Mandibles.

CM 96012 (H-3-90): Partial skeleton of a juvenile with frontal, partial maxilla (very incomlete), dorsal vertebrae, left clavicle, puboischiadic plate, humeri (ight incomplete) femora (both incomplete), and fragmentary fibula.

CM 96013 (H-1-90): Left astrabalus.

CM 96014 (H-11-91): Interclavicle, rigth humerus, metaodial and rib.

CM 96015 (H-3-91): Partial fibula and pes