snaggle Posted October 12, 2009 Share Posted October 12, 2009 Here are 2 bones from the same site as the other material. A bit different in shape from the other vertebrae that I have. With the general animal id and the bone id and the bone placement id, any guesses on the size of said animal? Go for it. Anne Link to comment Share on other sites More sharing options...
Boesse Posted October 12, 2009 Share Posted October 12, 2009 The bone on the left is an anterior thoracic vertebra from a mid-size cetacean, *most likely* a small mysticete, but possibly a large odontocete. The Bone on the right is an axis (second vertebra) from a medium sized odontocete (~12-20' range) or from a small mysticete. Bobby Link to comment Share on other sites More sharing options...
snaggle Posted October 12, 2009 Author Share Posted October 12, 2009 Hi Bobby, Is the axis bone mostly complete? Where would the spinal cord go? I have a couple of bones here that are half of a circle, somewhat flatish and if complete would create a large opening in the center. Here are 2 views of one. 6 inches across. Your guesstimates of size creates a question. Are Mysticete larger-boned than Odontocete for their size? Anne Link to comment Share on other sites More sharing options...
Boesse Posted October 12, 2009 Share Posted October 12, 2009 Hi Anne, The short answer is 'yes'. If you look at the axis, the the 'bump' on one of the articular surfaces is the odontoid process, which faces anteriorly; above this on the narrower side of the bone (it sorta looks like a broken off triangle) would be the spinal cord/neural canal. The other bone you have here is one half of an atlas; the odontoid process fits in to the ventral part of the big hole in the middle of the atlas (that whole hole isn't all neural canal, in other words). Mysticetes are generally larger, but there are many large odontocetes (extant and fossil) which are larger. Thus when dealing with isolated postcrania, it is often difficult to correctly ID whether the element belongs to a mysticete or odontocete. Your atlas is probably from a mysticete. Where are these fossils from, by the way? Bobby Link to comment Share on other sites More sharing options...
snaggle Posted October 13, 2009 Author Share Posted October 13, 2009 Bobby, Virginia, Yorktown Formation. The axis is ventral or on the backside of the atlas, correct. And the atlas would be the first vertebrae, right at the base of the skull? At what point along the spine do the vertebrae change from these compressed shapes to a more "vertebrae" shape? And with the inter-vertebral discs: At what point do they appear along the spine and when do they fuse to the vertebrae (age)? Amazing how it all fits together! You've been a great help! I'm constructing a whale in my mind! Thanks for taking the time. Maybe I've helped you bone up on your studies although it does sound like you've mastered this! Anne Link to comment Share on other sites More sharing options...
Boesse Posted October 13, 2009 Share Posted October 13, 2009 Hi Anne, The atlas is the 1st, the axis the 2nd, then there are five more cervicals; the thoracics are the ones that are the first 'vert-like' (the cervicals are still pretty flat). Bobby Link to comment Share on other sites More sharing options...
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