CVA - Axial skeleton

• Early ancestral vertebrates had a rudimentary axial skeleton. Early vertebrae were projections from the notochord
• In shark, the notochord is reduces
• Amphicoelous vertebra - (biconcave, or depressed on both the anterior and posterior sides), most common in amphibians and fish
• Opisthocoelous vertebrae - the anterior end end is convex and the posterior end is concave, common in ungulates (horses, cow, deer)
• Procoelous vertebrae - Concave at the anterior end and convex in the posterior end, typically found in reptiles and frogs
• Acoelous vertebrae - ends of the centrum are flat and are separated by intervertebral disks, found in most mammals
• Heterocoelous vertebrae - saddle-shaped, found in birds and turtles
• Purpose of the axial skeleton

  • Sites for muscle attachment
  • Supporting the weight of the body
  • Prevent telescoping of the body
• Uniqueness of vertebra shape

  • Amphicoelous and acoelous are designed to keep a stiffer vertebral column (fish)
  • Procoelous and opisthocoelous are more like a ball and socket joint and allow for more movement (snakes)
  • Heterocoelous allows for flexibility up and down, but not really twisting
• Lamprey have rudimentary and reduced vertebrae
• The neural arch (dorsal side) and hemal arch (ventral) protects vessels, etc.
• Sharks have underdeveloped ribs, whereas a bowfin fin has more developed ribs
• Coelacanths may retain their vertebrae into adulthood, but not much of a centra
• Eusthenopteron has a notochord very similar to a tetrapod
• Zygapopheses are how vertebrae attach to eachother. The prezygapophyses articulates with postzygapopheses on the vertebrae in front
• Xenarths (armadillos) have elongated and thick articulations that provide for more attachment for movement. This give them more force when burrowing
• Tightly interlocking vertebrae in shrews allow them to withstand lots of force to better protect them
• In gnathostomes, trunk and caudal vertebrae are the only identifiable features. If they have any ribs, it's on the thoracic vertebrae
• In fish, the pectoral girdle is attached to part of the skull. Whereas in tetrapods, the pectoral girdle is attached to the vertebrae, allowing the head to be able to move up and down and independently from the body
• Bone is just a big surface for muscle attachment to help with mobility, and muscles are receiving help from the neural spine
• Humans may have a reduced spine due to gravity weighing down on them
• Sloths/manatees are the only mammals that have either 5 to  9 vertebrae – they either add or subtract
• Squamates – a lot of trunk vertebrae
• Salamander – elongated trunks/tails
• Sacrum are fused vertebrae
• To go from shorter to longer spines, you either add vertebrae or make them longer
• Some regions are more likely to change than others, such as cervical vertebrae
• low variation of cervical vertebrae in mammals
• Lineatriton made vertebrae longer, oedipina added more vertebrae
• Turtles have reduced caudal vertebrae and elongated cervical vertebrae and modified trunk vertebrae.

  The carapace is fused flat ribs and vertebrae
• 2 clades of turtles, hidden necked and side necked.
• Chondrichthyans have multiple types of ribs.
• Tuberculum attaches dorsally to the diapophyses

  Capitulum attaches ventrally to the parapophysis
• The tips of the ribs often remain cartilage
• Facets are attachment points for cartilage
• Sternum is a floating bone that’s roughly associated with the pectoral girdle
• Birds have huge pectoral muscles that attach to a really long sternum, this is for flight