[D] Dryosaurus altus [Su] [T]
Jurassic Late Kimmeridgian Tithonian
Ornithischia Ornithopoda Dryosauridae
Morrison Formation, Colorado, Utah, Wyoming, US
Typespesies - Skull
Dryosaurus (Marsh, 1894) = Dysalotosaurus (Virchow, 1919)
Dryosaurus > Dryosaurus altus (Marsh, 1878) = Laosaurus altus (Marsh, 1878)
Dryosaurus > Dryosaurus lettowvorbecki (Virchow, 1919) = Dysalotosaurus lettow-vorbecki (Virchow, 1919)
Nearly complete skeleton 7 partial skeletons, postcranial elements, teeth.
Dryosaurus resembles hypsilophodontid ornithopods in many skeletal features but differs significantly from them in the following characters: absence of premaxillary teeth (also in Tenontosaurus); presence of prominent median vertical ridge on bucaal aspect of maxillary tooth crowns; contact between premaxilla and both prefrontal and lacrimal; quadratojugal small, overlapped extensively by jugal and quadrate; predentery with bilobed ventral process; humerus relatively long and slender, with low deltopectoral crest; ischium with proximally placed oburator process; ischium with curved (cauodorsally convex shaft and rostrocaudally expanded distal end.
Dryosaurus shares these characters with iguanodont ornithopods and, therefore should not be included in the Hypsilophodontidae