DB

Chapter 1-6: Introduction to Dinosaur Anatomy

Cranium and Skull Landmarks

  • Skull = cranium + dentary (jaw).
  • Orbit = eye socket; nares = nasal opening.
  • Fenestrae:
    • antorbital fenestra = window in skull anterior to orbit
    • mandibular fenestra = window within mandible
    • infra- and supratemporal fenestrae; lateral temporal fenestrae
  • Tooth-bearing bones:
    • maxilla = posterior tooth-bearing bone in the skull
    • premaxilla = anterior tooth-bearing bone
    • dentary = mandible's tooth-bearing bone
  • Other nearby bones: lacrimal, jugal (cheek region), quadrate
  • Foramen magnum = spinal cord opening; occipital condyles = articulation with atlas
  • Endocast = braincase representation of brain
  • Openings and landmarks help identify taxa; skull anatomy varies across taxa

Skeleton Organization

  • Axial skeleton: skull + vertebral column; rib cage included
  • Postcranial skeleton: everything else (limbs and girdles) beyond the skull
  • Appendicular skeleton: limbs and girdles (pectoral and pelvic)
  • Postcranial landmarks include vertebrae, ribs, tail; girdles and limbs
  • Orientation terms: anterior (front), posterior (back), dorsal (top/back), ventral (belly)

Vertebral Column and Axial Features

  • Three spine sections in dinosaurs: 3 sections (humans have 5)
  • Vertebra parts:
    • body (ventral)
    • neural arch
    • neural spine (dorsal)
    • transverse processes
  • Chevrons = ventral elements along the tail (in some vertebrae)
  • Atlas (C1) supports skull; occipital condyles articulate with atlas
  • Sacral vertebrae attach to pelvis; important for hindlimb support
  • Osteoderms = bony plates in the skin (e.g., ankylosaurs)

Pectoral Girdle and Forelimbs

  • Pectoral girdle components: scapula (shoulder blade), coracoid
  • Furcula (wishbone) in some dinosaurs; clavicles fused in dinosaurs
  • Sternum = breastbone (sternal plates)
  • Forelimb basics (proximal to distal): carpus (wrist), metacarpus (hand), digits (fingers)
  • Distal vs proximal references apply to limbs

Pelvic Girdle and Hind Limbs

  • Pelvic bones: ilium (dorsal), pubis (anterior), ischium (posterior)
  • Acetabulum = hip socket; articulates with femur
  • Three bones in the pelvis: 3 bones
  • Hind limb progression: tarsus (ankle) → metatarsus (sole) → digits (toes)
  • Sacral vertebrae connect spine to pelvis; important for weight-bearing

Dinosaur Hip Types and Relationships

  • Ornithischia = lizard-hip dinosaurs
  • Saurischia = bird-hip dinosaurs (includes Theropoda and Sauropoda)
  • Major groups often contrasted by hip structure and key synapomorphies; systematics to cover later

Miscellaneous Concepts and Study Tips

  • Endocasts illustrate the brain cavity; example braincase with color-coded brain shown in some fossils
  • Homology = shared ancestry of structures; Systematics = naming and relationships among taxa
  • Synapomorphy vs Apomorphy = key concepts for recognizing shared derived traits (to be covered next)
  • Review approach: use the review sheet and notes to describe features and time scales for quick recall