Open Paleo

Segnosaurus

Perle, 1979 SEG-no-SAWR-us

From Latin 'segnis' meaning 'slow' and Greek 'sauros' meaning 'lizard'; meaning 'slow lizard.' The specific name galbinensis refers to the Galbin region of the Gobi Desert.

100.5–89.8 million years ago Cenomanian–Turonian, Late Cretaceous
Late Cretaceous stages

Segnosaurus is a genus of therizinosaurid dinosaur that lived in what is now southeastern Mongolia during the Late Cretaceous, about 102-86 million years ago. Multiple incomplete but well-preserved specimens were discovered in the Gobi Desert in the 1970s, and in 1979 the genus and species Segnosaurus galbinensis were named. The generic name Segnosaurus means "slow lizard" and the specific name galbinensis refers to the Galbin region. The known material of this dinosaur includes the lower jaw, neck and tail vertebrae, the pelvis, shoulder girdle, and limb bones. Parts of the specimens have gone missing or become damaged since they were collected. Remains from Japan originally assigned to Allosaurus were reassigned to Segnosaurus sp. (of unspecified species) in 2025.

Diagnosis

  1. Lower jaw long and thin with closely positioned teeth
  2. Anterior teeth morphologically similar to theropods but much smaller than carnosaur teeth
  3. Deltopectoral crest of humerus prodigally developed
  4. Forelimb claw sharply curved, pointed and laterally compressed
  5. Ilia with broad anterior lobes and short posterior lobes with massive posterodorsal thickening
  6. Metatarsus short and massive, does not narrow proximally

Species

Segnosaurus galbinensis Perle, 1979

Type species

Named for the Galbin region of Mongolia, the area where the holotype was discovered.

Holotype
IGM 100/80 , Paleontological Center, Mongolian Academy of Sciences
Material
Lower jaws, incomplete humerus, complete radius and ulna, separate phalanges and forelimb claw, almost complete pelvis, incomplete right femur, 6 sacrals, 10 anterior caudals, 15 posterior caudals, first abdominal rib, dorsal rib fragments
Horizon
Bayanshiree Formation, Cenomanian–Turonian, Late Cretaceous , 100.5–89.8 million years ago
Locality
Amtgai, Ömnögovi, Mongolia

References

  1. Perle, A. (1979). Segnosauridae - novoe semeistvo teropod is posdnego mela Mongolii [Segnosauridae - a new family of theropods from the Late Cretaceous of Mongolia]. Trudy - Sovmestnaya Sovetsko-Mongol'skaya Paleontologicheskaya Ekspeditsiya 8: 45-55. perle1979a
  2. Barsbold, R. (1983). Khishchnye dinozavry mela Mongolii [Carnivorous dinosaurs from the Cretaceous of Mongolia]. Trudy - Sovmestnaya Sovetsko-Mongol'skaya Paleontologicheskaya Ekspeditsiya 19: 1-117.

    Supplies the stage the erecting paper omits, giving the holotype as Cenomanian-Turonian of the Baynshirenskaya Svita.

    barsbold1983a
  3. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Theropods. Princeton University Press.

    Source of the hip height estimate, and the appearance features.

    jones2026c