How many bones is a lot of bones? Is 206 a lot of bones, maybe it is. Maybe we need to compare the bones of other animals; how many bones in a giraffe, a cat, a mouse, a snake, a fish?
Mammals have very similar features and therefore we might expect the same number of bones. However, it doesn’t take long to find differences, cats with a long tail for example should have more bones and they do -cats - have about 244 bones. How about giraffes with their long neck? It turns out giraffe’s necks, long as they are, have the same number of vertebrae as our neck, seven. Obviously each vertebra is much longer in a giraffe. Giraffes do have more thoracic vertebrae than we do (we have 12 and they have 14) and in their tail, 20 bones, where as in what is left of our tail, the tiny coccyx mentioned earlier, is 3-5 vertebrae fused together and considered one bone.
The Baculum - penis bone - is found in some mammals (raccoons, dogs, chimps), but not humans, elephants, whales, monotremes, marsupials, rabbits, or any of the ungulates - deer cables, rhinos, hippos, horses, giraffes, pigs.
How about fish - they must have lots of bones - they are so hard to avoid if you try to fillet your own fish - have you ever done that - there is a real skill to doing it well.
Take the lowly cod fish- Gladus morhua - of collapsing fisheries fame. This species has more than 300 bones just in its skull. For comparison we have 22 bones in our skull. Why does a cod have so many?
Take a gander at this skull from a gar. Lots of teeth - not lots of bones.
The gar is also a fish, right? Why doesn’t it have as many as a cod? Of course the course of evolution has altered fish anatomy, which of course includes the bones. The gar, considered to have the gross anatomy more similar to ancient fish (or thinking about it another way the gar skeleton has not changed much over long periods of time). While the cod is a more modern fish, at least modern in the sense of its current anatomy has not been around for as long. This suggests that the as the numbers of bones increased in the ancestors to modern cod, population found the increases bony array beneficial to their survival and passed on those traits to the next generation of cod. The gar skull suggests, in turn, that though they have few bones, that array of skull bones/they look like plates really don’t they, so that array of plates enabled the survival of the species and therefore those traits (skull plates) still survive today.
The most fascination fish skeleton I have seen is this remarkable skeleton of a Porcupinefish, genus Diodon:
These fish have spines that extend out when they are threatened as defense against predator.
Some fish have other bony structures directly out of a sci-fi movie, like these pharyngeal jaws of the moray eel:
Sharks, known as cartilaginous fishes, have partial calcification of their vertebrae; but it is not ossified. More advanced bony fishes, carp, bass, tuna, grouper, have completely ossified vertebrae.
Quick look at calcification vs ossification: Calcification is the process where calcium salts accumulate and this occurs during bone formation but can also occur without the formation of actual bones cells. Calcium salts can also build up in tissues abnormally as well, causing hardening of otherwise soft tissue. Ossification is the formation of bone cells and structures of the bone tissue layer down by those bones cells. Overall ossification includes calcification but calcification does not include ossification.
Back to mammals: I came across this Jaguar skeleton in Belize:
The second cervical vertebra (called the axis) has large ‘wings’. Likely these are for muscle attachment - large/strong muscles of the neck - for aid in pulling prey into trees?
I couldn’t find a good video of a jaguar but check out this video of a leopard pulling prey into tree: https://www.youtube.com/watch?v=bzr7czsMxOE
What good are bones?
The evolution of bones was a great moment in evolution - vertebrates exploded and seem to be running the planet, though maybe not very well.
Want to read some old pondering with much more thought than I have put in here go find Richard Owens book from 1943 on the Vertebrate skeleton printed: The Archetype and homologies of the vertebrate skeleton. It's on the web somewhere - google scanned it :-)