Divergence Between Cats & Dogs

[maddog]

I heard an interesting piece of trivia this morning...

 

That is that cats don't have collar bones and that is why they are easily able to right themselves when falling

upside down. Interesting.

 

So this got me to thinking. If cats can and dogs can't then dogs must have collar bones as we do. Then how

long ago was it that the orders of canine and feline diverged ?

 

The monkey found in Germany had properties of both apes and monkeys so it has been thought it was before

their divergence. Just curious if anyone knows and how or why...

 

maddog

[maddog]

What... My question is not controversial, so no one has any comments or can lead me in a direction for my inquiry???

 

Now, if I had claimed that I had been to Mars recently -- I know I would have gotten a response (not the one I am seeking!) &

would have likely had my thread moved to silly claims. I find it odd that in all the recent posts, I am getting nil in response

(not even a comment).

 

maddog

[belovelife]

well, how different are the skelital structures of cats and dogs,

brain orientation, desighn and stuff

 

muscle structure

 

etc

 

probably at around the same time we left the water, mabe,

 

if that infact is what happened

[JMJones0424]

What... My question is not controversial, so no one has any comments or can lead me in a direction for my inquiry???

I don't know, but I did some quick digging around in wikipedia and can give you what I've found. Cats and dogs are both members of the order carnivora and their lineage diverges at the suborders feliformia and caniformia about 42 million years ago.

 

Cladogram of feliforms-

 

EDIT: After some googling, I don't think it's accurate to say that dogs have collarbones and cats don't. It looks like most members of carnivora either don't have clavicles or they have extremely reduced clavicles. Cats do have clavicles, but they're small and free-floating, and most dogs have vestigial clavicles embedded in muscle tissue.

Edited August 7, 2012 by JMJones0424

[CraigD]

That is that cats don't have collar bones and that is why they are easily able to right themselves when falling upside down. Interesting.

I remember being told the same thing, by my dad, a human medical doc who did occasional veterinary surgeries with a vet doc friend of his, except that account attributed cats’ ability to absorb more acceleration with their front legs when jumping down from high places, compared to dogs, which would be injured in the same jump.

 

It appears, from JMJones’s research, that we were both too credulous in accepting this folk wisdom:

EDIT: After some googling, I don't think it's accurate to say that dogs have collarbones and cats don't. It looks like most members of carnivora either don't have clavicles or they have extremely reduced clavicles. Cats do have clavicles, but they're small and free-floating, and most dogs have vestigial clavicles embedded in muscle tissue.

Having had 40+ years of error corrected, I did some internet-assisted reading of my own, and have a much more accurate grasp of cat anatomy now. :)

 

Anatomically, the difference between us rigid-shouldered humans and flexible-shouldered housecats isn’t the lack of a clavicle (collar bone) in the cat, but the length and flexibility of the ligaments and muscles between the scapula (shoulder blade) specifically the knob of the scapula called the acromion – and hence, the connection between them, the acromioclavicular joint. Though kitty clearly has lots of ligaments and muscles connecting his scapular and clavicle (now that I know to look for such a bone, my poor hapless pet is a handy and accurate, if not entirely cooperative, anatomical model :cat: ) I find no references to such a joint in any internet search, suggesting it’s such a lose connection that it doesn’t qualify as a joint in normal anatomical nomenclature.

 

Though I can’t find any online reference, the other end of the clavicle, the sternoclavicular joint attaching it to (your gotta love the obvious consistency of anatomical nomenclature) the sternum, appears in my furry in-hand reference to be as tightly attached as my own.

 

From what I can tell, dogs have even smaller, less rigidly attached clavicles than cats. The “clavicle has ossified in 96%” reference in JM’s reference NIH linked-to references appear to mean that, in 4% of dogs, the bone is entirely absent.

 

This pretty much completely contradicts the folktale-derived “dogs have collar bones, cat’s don’t”, which IMHO pretty much goes to show that, when it comes to skeletal anatomy, you should be slow to trust anything short of an actual dissection and mount – or at least, and less messy and distressing, a thorough prodding and poking.

 

This reminds me of the 5th through 4th century Greeks, who though they invented most of its terms and did a wonderful job of eliminating superstitions about anatomy, had some bizarrely misguided idea about it, such as the idea that the arteries contained air rather than blood, and that a “wandering womb”, attracted to pleasant smells and repelled by nasty ones, causes many diseases in women.

 

At least we 21st century folk have good reference materials, and folk who think to use them. Progress is good.

 

Back to the evolutionary question: as best I can tell, clavicles appear or don’t appear in varyingly rigid attachments, in a lot of evolutionarily distantly related present day animals. This wikipedia section describes them as appearing in primitive bony fish, where they’re associated with the pectoral fins and gills, but being absent in most fish presently alive. The earliest 4-legged land animals appear to have had them, but present day crocodiles don’t, turtles do, and in birds, they’ve fused together with an intermediate bone to form the familiar wishbone (furcula).

 

Bony fish appeared in the Middle Devonian, around 420,000,000 years ago, way before the Feliformia/Caniformia split of about 42,000,000 years ago pictures in JM’s diagram, or even the appearance of the first land animals around 400,000,000 years ago. So clavicles are very, very old bones.

[maddog]

I don't know, but I did some quick digging around in wikipedia and can give you what I've found. Cats and dogs are both members of the order carnivora and their lineage diverges at the suborders feliformia and caniformia about 42 million years ago.

Thanks, JMJones..., I found that same jpeg, yesterday. Though I do appreciate the extra stuff you found out. I feel more

completed in adding to what I found out. ;-)

 

maddog

[maddog]

Having had 40+ years of error corrected, I did some internet-assisted reading of my own, and have a much more accurate grasp of cat anatomy now. :)

 

Anatomically, the difference between us rigid-shouldered humans and flexible-shouldered housecats isn’t the lack of a clavicle (collar bone) in the cat, but the length and flexibility of the ligaments and muscles between the scapula (shoulder blade) specifically the knob of the scapula called the acromion – and hence, the connection between them, the acromioclavicular joint. Though kitty clearly has lots of ligaments and muscles connecting his scapular and clavicle (now that I know to look for such a bone, my poor hapless pet is a handy and accurate, if not entirely cooperative, anatomical model :cat: ) I find no references to such a joint in any internet search, suggesting it’s such a lose connection that it doesn’t qualify as a joint in normal anatomical nomenclature.

 

Though I can’t find any online reference, the other end of the clavicle, the sternoclavicular joint attaching it to (your gotta love the obvious consistency of anatomical nomenclature) the sternum, appears in my furry in-hand reference to be as tightly attached as my own.

 

From what I can tell, dogs have even smaller, less rigidly attached clavicles than cats. The “clavicle has ossified in 96%” reference in JM’s reference NIH linked-to references appear to mean that, in 4% of dogs, the bone is entirely absent.

 

This pretty much completely contradicts the folktale-derived “dogs have collar bones, cat’s don’t”, which IMHO pretty much goes to show that, when it comes to skeletal anatomy, you should be slow to trust anything short of an actual dissection and mount – or at least, and less messy and distressing, a thorough prodding and poking.

I was wondering if what I heard was too simple an explanation (Clavicle and all).

 

Back to the evolutionary question: as best I can tell, clavicles appear or don’t appear in varyingly rigid attachments, in a lot of evolutionarily distantly related present day animals. This wikipedia section describes them as appearing in primitive bony fish, where they’re associated with the pectoral fins and gills, but being absent in most fish presently alive. The earliest 4-legged land animals appear to have had them, but present day crocodiles don’t, turtles do, and in birds, they’ve fused together with an intermediate bone to form the familiar wishbone (furcula).

 

Bony fish appeared in the Middle Devonian, around 420,000,000 years ago, way before the Feliformia/Caniformia split of about 42,000,000 years ago pictures in JM’s diagram, or even the appearance of the first land animals around 400,000,000 years ago. So clavicles are very, very old bones.

Yeah, in JMJones' post, it appears that the whole line (Micadae) of which Carnivora formed from that the Clavicle was more vestigial in the most part. Thanks to you both for the clarification.

 

maddog