Open Paleo

Bactrosaurus

Gilmore, 1933 BAK-tro-SAWR-us /ˌbæktrəˈsɔːrəs/

From Greek baktron (βάκτρον) meaning 'club' or 'walking stick' + Greek sauros (σαῦρος) meaning 'lizard'; overall meaning 'club lizard'.

89.8–66.0 million years ago Coniacian–Maastrichtian, Late Cretaceous
Late Cretaceous stages

Bactrosaurus is a genus of herbivorous hadrosauroid dinosaur that lived in Asia during the Late Cretaceous. The position Bactrosaurus occupies in the Cretaceous makes it one of the earliest known hadrosauroids, and although it is not known from a full skeleton, Bactrosaurus is one of the best known of these early hadrosauroids, making its discovery a significant finding.

Diagnosis

  1. Posterior dorsal vertebrae with tall club-shaped spines, transverse diameter increasing from base to top, nearly as wide fore-and-aft as centrum length.
  2. Sacrum composed of seven coossified vertebrae.
  3. Ilium strongly arched upward at center with strongly decurved, blade-like preacetabular process.
  4. Pubis with very short neck and greatly expanded prepubic blade, far shorter and more expanded than in any other known hadrosaurian.
  5. Dentition reduced: 20-23 vertical tooth rows in dentary, 28 in maxillary (fewest in any known hadrosaurian at adult size).
  6. Pes unguals with squarely truncated, rugosely roughened anterior margins in adults.

Species

Bactrosaurus johnsoni Gilmore, 1933

Type species

Named for Albert F. Johnson, who collected the first specimens in 1923.

Holotype
AMNH 6553 , American Museum of Natural History
Material
Dentary, maxillary and other skull parts; ten dorsal vertebrae, seven sacrals, thirty-six caudals (mostly in series); left scapula, left sternal, both pubes, both ischia, left femur, fibula, complete left hind foot and part of right.
Horizon
Iren Dabasu Formation, Coniacian–Maastrichtian, Late Cretaceous , 89.8–66.0 million years ago
Locality
Johnson's Quarry, Inner Mongolia, China

Synonyms of the genus

Name Type Reason
Bakesaurus nomen nudum Informal name based on a maxilla assigned to Bactrosaurus; created and pictured in a Chinese-language book by Zhou (2005).
Paraiguanodon nomen nudum Manuscript name (Paraiguanodon incolapaludis) coined by Barnum Brown in the early 1930s, perhaps for a lecture series, and seen on figures of Bactrosaurus johnsoni skeletons in the files of the American Museum of Natural History. Never formally published; reported by Olshevsky (1991).

References

  1. Gilmore, C. W. (1933). On the dinosaurian fauna of the Iren Dabasu Formation. Bulletin of the American Museum of Natural History 67(2): 23-78. gilmore1933a
  2. Olshevsky, G. (1991). A revision of the parainfraclass Archosauria Cope, 1869, excluding the advanced Crocodylia. Mesozoic Meanderings 2: 1-196.

    Reports the manuscript name Paraiguanodon incolapaludis, coined by Barnum Brown in the early 1930s on figures of Bactrosaurus johnsoni skeletons in the American Museum of Natural History.

    olshevsky1991a
  3. Paul, G. S. (2024). The Princeton Field Guide to Dinosaurs (3rd ed.). Princeton University Press.

    Source of the appearance features.

    paul2024a
  4. Zhou, S. Q. D. (2005). The Dinosaur Egg Fossils in Nanyang, China. 1-145. China University of Geosciences Press.

    Chinese-language book that created and pictured the maxilla underlying the nomen nudum Bakesaurus.

    zhou2005a