Genus: Duonychus KOBAYSHI, ZELENITSKY, FIORILLO & TSOGTBAATAR, 2025
Etymology: Greek, duo, "two" and Greek, onyx, "claw."

Species: tsogtbaatari KOBAYSHI, ZELENITSKY, FIORILLO & TSOGTBAATAR, 2025
Etymology: In honor of Khishigjav Tsogtbaatar, a paleontologist and former director of the Institute of Paleontology, Mongolian Academy of Sciences in ulaanbaatar, Mongolia.

Holotype: MPC-D 100/85

Locality: Urlibe Khudak locality N43°27.092', E107°23.476, Ömnögov, eastern Gobi Desert, Mongolia.

Horizon: Bayanshiree Formaiton.

Biostratigraphy:

Age: Cenomanina Stage, Middle Gallic Subepoch, Early Gulf Epoch, Middle Cretaceous-Coniacian Stage, Early Senonina Subepoch, Middle Gulf Epoch, Early Late Cretaceous.

Material: 6 articulated dorsal vertebrae, 6 articulated sacral vertebrae with sacral ribs, the anterior-most caudal vertebra, some dorsal ribs, partial left scapula and coracoid, humeri, ulnae, radii, carpals, metacarpals, the left and right manus, right ilium, both pubes and the proximal end of the left sichium.

Duonychus tsogtbaatari after KOBAYSHI, ZELENITSKY, FIORILLO & TSOGTBAATAR, 2025, Holotype: MPC-D 100/85: A) partial ilium: B) anterior view of pubis; C) ischium; D) dorsal view of sacrum and ilium and E) dorsal vertebrae.

Duonychus tsogtbaatari after KOBAYSHI, ZELENITSKY, FIORILLO & TSOGTBAATAR, 2025, Holotype: MPC-D 100/85:A) partial scapula, coracoid and humerus; B) left humerus in ventral view; C) left humeurs in distal views; D) right ulna and radius in anterior view; E) right manus in dorsal view; and F) right manus in lateral view.

Duonychus tsogtbaatari after KOBAYSHI, ZELENITSKY, FIORILLO & TSOGTBAATAR, 2025, Holotype: MPC-D 100/85: left distal carpals 1 and 2 in A) dorsal, B) proximal and C) left radiale in dorsal view.

Duonychus tsogtbaatari after KOBAYSHI, ZELENITSKY, FIORILLO & TSOGTBAATAR, 2025, Holotype: MPC-D 100/85: right distal carpals and metacarpals A) dorsal; B) medial; C) proximal: D) ventral; E) lateral views; F) intermedium in proxial, distal and dorsal views from left to right; G) left parital matacarpals in dorsal and H) proximal views.

Duonychus tsogtbaatari after KOBAYSHI, ZELENITSKY, FIORILLO & TSOGTBAATAR, 2025, Holotype: MPC-D 100/85: A) Left digit I with keratinous sheath; B) left digit II in laterial view and C) midsection of ungual II.

Duonychus tsogtbaatari after KOBAYSHI, ZELENITSKY, FIORILLO & TSOGTBAATAR, 2025, Holotype: MPC-D 100/85: forelimb roatation; A) B) and C) ungual roatation.

Duonychus tsogtbaatari skeleton after KOBAYSHI, ZELENITSKY, FIORILLO & TSOGTBAATAR, 2025, Holotype: MPC-D 100/85.