At a Glance Field Information Species Stegosaurus stenops — Ornithischia, Stegosauridae Period Late Jurassic, approximately 155–150 Ma Formation Morrison Formation, western North America Climate Seasonal, semi-arid with wet and dry cycles Vegetation Ferns, cycads, conifers, horsetails — no grasses or flowering plants Quick Answer: Stegosaurus lived in the floodplains and river valleys of what is … Read more
At a Glance Field Information Species Stegosaurus stenops — Ornithischia, Stegosauridae Period Late Jurassic, approximately 155–150 Ma Extinction timing End of the Late Jurassic, ~150 Ma — approximately 84 million years before the K-Pg event Extinction type Late Jurassic faunal turnover — not a mass extinction event Replaced by Ankylosaurs and ceratopsians as dominant herbivores … Read more
At a Glance Field Information Species Stegosaurus stenops — Ornithischia, Stegosauridae Period Late Jurassic (155–150 Ma) First described 1877 by Othniel Charles Marsh, Yale University Holotype YPM 1850 — fragmentary; S. armatus (later replaced by S. stenops as type species) Most complete specimen NHMUK PV R36730 (“Sophie”) — 85% complete, Natural History Museum London Formation … Read more
Stegosaurus vs Allosaurus At a Glance Feature Stegosaurus Allosaurus Classification Ornithischia, Stegosauridae Saurischia, Allosauridae Period Late Jurassic (155–150 Ma) Late Jurassic (155–145 Ma) Length ~9 m (30 ft) ~8.5–12 m (28–39 ft) Weight Estimated 2,700–4,000 kg (5,950–8,820 lb) ~1,500–2,200 kg (3,300–4,900 lb) Primary weapon Thagomizer — 4 spikes, 60–90 cm each Serrated teeth, three-clawed forelimbs … Read more
At a Glance Field Information Species Stegosaurus stenops — Ornithischia, Stegosauridae Period Late Jurassic (155–150 Ma) Spike count 4 spikes arranged in 2 pairs Spike length 60–90 cm (2–3 ft) per spike Orientation Horizontal, not vertical Key fossil evidence Allosaurus vertebra UMNH 10781 — puncture wound matching spike dimensions Quick Answer The stegosaurus thagomizer is … Read more
At a Glance Field Information Species Stegosaurus spp. — Ornithischia, Stegosauridae Period Late Jurassic, approximately 155–150 Ma Number of plates 17 in well-documented S. stenops specimens Plate arrangement Two alternating rows running from neck to tail base Plate composition Osteoderms — bony skin structures, not attached to the spine Current consensus No settled consensus; multiple … Read more
At a Glance Field Information Species Stegosaurus spp. — Ornithischia, Stegosauridae Period Late Jurassic, approximately 155–150 Ma Diet type Herbivore Tooth type Small, leaf-shaped, non-occluding Feeding height Low to mid-level browse; estimated reach up to approximately 1 metre (3.3 ft) at ground level to potentially higher with bipedal rearing Feeding evidence Tooth morphology, jaw structure, … Read more
At a Glance Field Information Species Stegosaurus ungulatus / S. stenops — Ornithischia, Stegosauridae Period Late Jurassic, approximately 155–150 Ma Length Up to 9 metres (30 ft) Weight Estimated 2,700–4,000 kg (5,950–8,820 lb) Height at hips Approximately 2.75 metres (9 ft) Plate height Up to 60 cm (24 in) on the largest individuals Quick Answer: … Read more
At a Glance Feature Archaeopteryx Confuciusornis Period Late Jurassic (150–148 Ma) Early Cretaceous (125–120 Ma) Body length ~50 cm ~50–60 cm Teeth Present — small, conical Absent — toothless beak Tail Long, bony (approx. 20 vertebrae) Short — true pygostyle present Wing claws Three functional clawed fingers Reduced or absent Sternum No keeled sternum evidenced … Read more
At a Glance Feature Archaeopteryx Deinonychus Period Late Jurassic (150–148 Ma) Early Cretaceous (115–108 Ma) Body length ~50 cm ~3.4 m Body mass ~0.8–1 kg ~70–80 kg (estimated) Feathers Fully feathered — flight and body feathers evidenced Feathers inferred from related taxa; not directly evidenced in all specimens Flight capability Contested — powered flight possible … Read more