Scelidosaurus harrisonii

Scelidosaurus harrisonii was an early armoured ornithischian from the Jurassic coast of southern England. Several articulated skeletons preserve nearly the entire animal, making it unusually informative for the beginning of thyreophoran evolution. Its low body carried multiple longitudinal rows of osteoderms, ranging from small ossicles to keeled plates and pointed elements around the neck and shoulders. A modern redescription found it closer to ankylosaurs than to stegosaurs, but the deepest branches of the armoured-dinosaur tree remain sensitive to analytical choices.

Its fossils occur between approximately 193 and 190 million years ago. Values shown here are approximate and reflect the current curated seed dataset.

The skull was long and low, with a narrow beak and leaf-shaped teeth. Keratinous scutes covered much of the skull roof, inferred from the texture and boundaries of the underlying bone. Three principal rows of larger osteoderms ran along each side of the neck, trunk and tail, with smaller ossicles between them. Robust hind limbs and shorter forelimbs supported habitual quadrupedal movement, although limb anatomy retained features inherited from bipedal ancestors. Its jaws moved mainly up and down, with limited flexion helping pulp and shear vegetation.

• Multiple longitudinal rows of keeled osteoderms
• Pointed armour elements around the neck and shoulders
• Keratinous scutes inferred across much of the skull roof
• Long, low skull with a narrow beak and leaf-shaped teeth
• Robust limbs supporting habitual quadrupedal movement
• Several nearly complete articulated skeletons

Quarry owner James Harrison sent fossil bones from the cliffs near Charmouth to Richard Owen beginning in 1858. Owen named Scelidosaurus harrisonii in 1861 and later produced a fuller monograph. The principal type skeleton NHMUK R1111 is held by London's Natural History Museum. Additional articulated specimens from the same Dorset coast, including material prepared in the twenty-first century, allowed David Norman to redescribe the skull, armour, skeleton and biology in a series of studies culminating in 2020.

Discovery credit: James Harrison.

Naming authors: Richard Owen.

The Charmouth Mudstone Formation accumulated in a shallow marine setting along the Early Jurassic coast. Scelidosaurus carcasses were transported from nearby land into the sea, where fine sediment buried them. The marine rocks preserve ammonites, fish and marine reptiles exceptionally well, but provide only indirect evidence for the vegetation and terrestrial community in which the living dinosaur fed.

Scelidosaurus was a low-browsing herbivore. Jaw reconstruction suggests mainly vertical biting with some controlled flexion that improved plant processing. Its armour plausibly reduced injury from predators and may also have contributed to display or species recognition. The fossils do not reveal herd structure, parental care, colour patterns or how often it adopted a bipedal stance.

• It is one of the most completely known dinosaurs from the Early Jurassic.
• Its fossils were washed from land into a shallow sea before burial.
• Detailed bone surfaces indicate that keratinous scutes covered much of its skull.
• Its anatomy records an early stage in the evolution of ankylosaur-like armour.

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1. 01
   Scelidosaurus harrisonii (Dinosauria: Ornithischia) from the Early Jurassic of Dorset, England: biology and phylogenetic relationships

   David B. Norman · Zoological Journal of the Linnean Society 191(1), 1–86 · 2020

   Open source
2. 02
   Scelidosaurus

   Natural History Museum, London

   Open source