BIO 113 Dinosaurs
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Lab 10
Herbivorous Dinosaurs

Heterodontosauridae


  • Primitive ornithischians not closely related to any other group
  • Small size (<2m)
  • Bipedal, with long tail
  • Unique chewing teeth and canine-like fangs
  • At least one species had filamentous (hair-like) fibers
  • Probably herbivorous
Pegomastax

Thyreophora

  • Armored dinosaurs
  • Have rows of osteoderms (dermal armor) along neck, back & tail
  • Mostly quadrupedal
  • All are herbivorous, with shearing dentition
  • All are relatively small-brained

Basal Thyreophorans
  • Most primitive of the Thyreophorans
  • Armor plates are small and do not connect or form spikes
  • Hind limbs longer than forelimbs: probably partially bipedal
Scelidosaurus

Stegosauria
  • 2 rows of enlarged dorsal osteoderms that form vertical plates or spikes
  • 4 spikes at end of tail ("thagomizer")
  • Head very small
  • Forelegs shorter than hindlegs
Hesperosaurus fossil
Hesperosaurus skeleton, Late Jurassic, North America (MAL1)
Stegosaurs

Ankylosauria
  • Osteoderms form a nearly contiguous dorsal shell-like covering
  • Body very wide and low to the ground
  • Many have laterally-projecting spikes
Gastonia fossil
Gastonia skeleton, Early Cretaceous, North America (MAL)
Ankylosaurs

Marginocephalia

  • Back of skull with bone ridge or frill
  • Herbivorous
  • Known only from Northern Hemisphere from late Jurassic to Cretaceous

Pachycephalosauria
  • Dome-headed (or bone-headed) dinosaurs
  • Top of skull is greatly thickened (may be flat or dome-shaped)
  • Skull usually has various knobs or spikes
  • Bipedal
  • Snout ends in broad beak
Pachycephalosaurus fossil
Pachycephalosaurus skeleton, Late Cretaceous, North America (MAL)
Pachycephalosaurs

Ceratopsia
  • Horned dinosaurs (though not all have horns)
  • Narrow snout with parrot-like beak (and a unique bone at tip of upper jaw)
  • Projecting bones at side of skull near cheek
  • Most have enlarged bone frill extending from back of skull

Basal Ceratopsians
  • Primitive members of the group near base of family tree
  • Generally lack horns
  • May be bipedal or quadrupedal
  • Generally smaller than the more derived forms
Protoceratops fossil
Protoceratops skeleton, Late Cretaceous, Mongolia (WDC2)
Basal Ceratopsians

Ceratopsidae
  • Advanced, derived species
  • Nearly all have some horns on head, especially on nose and above eyes
  • Frills are large and well developed
  • Dental batteries indicate chewing ability
  • All are quadrupedal
  • Generally large-sized
Albertaceratops fossil
Albertaceratops skeleton, Late Cretaceous, Montana (WDC2)
Ceratopsidae

Ornithopoda

  • Beaked Dinosaurs
  • Relatively unspecialized body form without armor or weapons
  • Hind legs longer than front legs
  • Bipedal or semiquadrupedal
  • Ossified tendons stiffened large tail
  • Herbivorous; most chopped or chewed their food

Hypsilophodontids & other Stem Ornithopods
  • Most primitive group of Ornithopods
  • Relationships uncertain, but likely paraphyletic
  • Relatively small size
  • Bipedal; probably fast runners
Thescelosaurus fossil
Thescelosaurus skeleton, Late Cretaceous, North America (MAL)
Hysilophodonts

Iguanodontia
  • Paraphyletic grouping of species intermediate
    between Hypsilophodonts and Hadrosaurids
  • Moderate to large size
  • Moved both bipedally and quadrupedally
  • Necks relatively long
  • Generally lacked any head ornamentation
  • Some had enlarged thumb spikes
Probactrosaurus fossil
Probactrosaurus adult & juvenile skeletons, Early Cretaceous, China (AMNH3)
Iguanodontoids

Hadrosauridae
  • "Duck-billed Dinosaurs"
  • Large size
  • Mostly quadrupedal (but may have run on hind legs)
  • Mouth generally broad and flat
  • Had well-developed dental batteries for efficient chewing
  • Many with distinctive head crests
  • Uncrested forms may have had inflatable nasal sacs
Edmontosaurus fossil
Edmontosaurus skeletons, Late Cretaceous, North America (MAL)
Hadrosaurs

Sauropodomorpha

  • Have very long necks
  • Head is proportionately small
  • Herbivores with weak cropping teeth
  • Enlarged thumb claw
  • Generally large to gigantic in size

Prosauropoda
  • Long necks, small heads
  • Bipedal: forelegs smaller than hindlegs
  • Probably paraphyletic
Plateosaurus fossil
Plateosaurus skeleton, Late Triassic, Europe
Prosauropods

Sauropoda
  • Necks long to extremely long
  • Heads proportionately tiny
  • Quadrupedal
  • Tails often very long
  • Large to enormous sized
Mamenchisaurus fossil
Juvenile Mamenchisaurus skeleton, Late Jurassic, China
Basal Sauropods
Diplodocoid Sauropods
Macronarian Sauropods
Titanosaurs

Footnotes
  1. MAL = Museum of Ancient Life, Lehi, UT
  2. WDC = Wyoming Dinosaur Center, Thermopolis
  3. AMNH = Arizona Museum of Natural History, Mesa
  4. FMNH = Fernbank Museum of Natural History, GA
This page last updated 14 July 2017 by Udo M. Savalli ()
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