Open Paleo

Anoplosaurus

Seeley, 1879 an-OP-lo-SAWR-us

From Greek 'anoplos' meaning 'unarmed' or 'unarmored' and 'sauros' meaning 'lizard'; meaning 'unarmed lizard'

113.2–100.5 million years ago Albian, Early Cretaceous
Early Cretaceous stages

Anoplosaurus is an extinct genus of herbivorous nodosaurid dinosaur from the Early Cretaceous (late Albian age) of Cambridgeshire, England. It has in the past been classified with either the armored dinosaurs or the ornithopods, but current thought has been in agreement with the "armored dinosaur" interpretation, placing it in the Ankylosauria.

Diagnosis

  1. Dorsal ribs T-shaped: visceral surface compressed and dorsal surface expanded like crosspiece of capital T, suggesting great development of intercostal muscles
  2. Scapula with distinctive massive quadrate spinous process on humeral side, increasing thickness of bone, rounded inferiorly like pulley surface
  3. Sacral region with enlarged neural canal much wider than diameter of dorsal centrum, indicating hind limbs relatively more developed than fore limbs
  4. Body carried in semierect position: dorsal vertebral centrums form upward arch unlike straight horizontal column, suggesting semierect progression
  5. Sacral vertebrae lack anchylosis but in intimate juxtaposition; series includes six centrums with dissimilar forms unlike rounded dorsal forms
  6. Tail shows semierect posture correlation: caudal vertebrae form curve with convex side downward, root elevated well above ground

Species

Anoplosaurus curtonotus Seeley, 1879

Type species

From Latin curtus, meaning 'short', and the Greek noton, meaning 'back'.

Lectotype
CAMSM B55731 , Sedgwick Museum, University of Cambridge
Material
Partial right scapula
Notes
Seeley (1879) erected the species on a syntype series and designated no holotype. Pereda-Suberbiola and Barrett (1999) designated CAMSM B55731, a partial right scapula, as the lectotype under ICZN Art. 74, chosen because it had been figured previously (Seeley 1879, pl. 35, fig. 3) and possesses a distinctive morphology; the remaining 72 cataloged syntypes (CAMSM B55670-B55742, excluding B55731) became paralectotypes. They comprise a partial left dentary, cervical, dorsal, sacral and caudal centra, neural arches, dorsal and sacral ribs, coracoids, humerus, femur, tibia, a possible metacarpal, possible metatarsals and a phalanx, apparently from a single immature individual about 2 m long, an association exceptional among Cambridge Greensand material. Pereda-Suberbiola and Barrett state 77 syntypes in prose but catalog 73 numbers; the discrepancy is in the source and is not resolvable. The type horizon is uncertain. Pereda-Suberbiola and Barrett give "?Upper Gault Clay or ?Cambridge Greensand, Upper Albian" and favor the Gault on taphonomic grounds, since an associated skeleton would be exceptional for the Cambridge Greensand; Barrett and Bonsor (2020) place the associated skeleton in the Cambridge Greensand Member, whose vertebrate remains are reworked from the underlying Gault. The material is late Albian in age either way.
Horizon
Albian, Early Cretaceous , 113.2–100.5 million years ago
Locality
Reach, Cambridgeshire, United Kingdom Which unit the syntypes came from is unresolved. Pereda-Suberbiola and Barrett (1999) place them in either the Cambridge Greensand or the underlying Gault Clay, upper Albian in either case, and suggest the associated material "may have been recovered from the phosphate beds of the uppermost Gault Clay rather than from the Cambridge Greensand". The Cambridge Greensand is itself a remanié deposit whose fossils are reworked from older beds.

References

  1. Seeley, H. G. (1879). On the Dinosauria of the Cambridge Greensand. Quarterly Journal of the Geological Society of London 35(1-4): 591-636. Geological Society of London. doi:10.1144/gsl.jgs.1879.035.01-04.42 seeley1879a
  2. Pereda-Suberbiola, X.; Barrett, P. M. (1999). A systematic review of ankylosaurian dinosaur remains from the Albian-Cenomanian of England. Special Papers in Palaeontology 60: 177-208.

    Lectotype designation (ICZN Art. 74) and redescription; removes the species from Ornithopoda to Nodosauridae.

    pereda-suberbiola1999a
  3. Barrett, P. M.; Bonsor, J. A. (2020). A revision of the non-avian dinosaurs 'Eucercosaurus tanyspondylus' and 'Syngonosaurus macrocercus' from the Cambridge Greensand, UK. Cretaceous Research 118: 104638. Elsevier BV. doi:10.1016/j.cretres.2020.104638

    Affirms Anoplosaurus curtonotus as the only valid taxon named from the Cambridge Greensand, and dates the Member's vertebrate remains as reworked from the upper Albian Gault Formation.

    barrett2020a
  4. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Ornithischians. Princeton University Press.

    Source of the body length estimate.

    jones2026a