Aelurodon ferox was a species of wild dog that lived in North America between 10 and 16 million years ago.
It was about the size of a wolf– weighing between 88 and 100 pounds.
It was not a wolf at all.
It was sort of a wolf before there were wolves.
You see, North America, there was a subfamily of the dog family that was solely endemic to North America.
They were called the Borophaginae (technically, “the bone eaters” but are more popularly known as the bone crushers).
Some of these dogs had quite powerful jaws– much more so than those of a modern Northern big-game hunting wolf– and rather large size.
These dogs are often popularly referred to as “hyena dogs,” which makes things even more wonderfully confusing. African wild dogs were sometimes given exactly the same name.
The largest Borophagine dogs were in the genus Epicyon, and these dogs were very much like large hyenas. They had very powerful jaws and robust teeth that allowed them break large bones in much the same way modern hyenas do. (Wikipedia says that there was a species of Aelurodon that was as large as a tiger. I can’t find the reference. Wikipedia is probably wrong.)
This image of Aelurodon ferox comes from Dogs: Their Fossil Relatives and Evolutionary History (2010) by Xiaoming Wang and Richard Tedford.
You’ll note that the image of Aelurodon ferox shows a dewclaw on the hind legs. All Borophagine dogs had dewclaws on their hind legs. No modern wild dogs have this feature, except domestic dogs and wild dogs that inherited this trait through crossbreeding with domestic dogs with this trait. (These dewclaws on the hind legs have been a great diagnostic feature for determining if Italian wolves have dog ancestry.)
Dogs derive from ancestors that had five digits on each toe. Bears and raccoons have five digits on each foot, as did the ancestors of dogs, bears, and raccoons.
However, dogs have evolved to be long distance runners, and as they have developed into runners, they have evolved specialized running feet. These feet are digitigrade, which means they walk on their toes. Having one less toe on the ground allows for more efficient movement, so the fifth toe on the inside has moved away from the bottom of the foot and up the leg. The fifth toe in most modern dogs is found only on the front legs. African wild dogs have actually lost the fifth toe on the front legs, but it is found on all other dog species.
Borophagine dogs evolved from ancestors with five digits on each foot. They were capable of running long and hard, like wolves and other modern dogs, but they had not yet lost the dewclaw on the hind legs.
So there were once wolves that were not wolves and dogs that had hyena features living in North America, and these animals had dewclaws on their hind legs.
Supporting a very large size for A. Taxoides is: “The American Naturalist, Vol. 28”, by the Essex Institute, American Society of Naturalists, pub. Essex Institute, 1894, which compares it to Sabre Toothed Tigers (Smilodon ran 790 to 1000 lb.)
However on, “Top-10 Largest Canids”
(http://carnivoraforum.com/index.cgi?board=zoological&action=print&thread=12518)
there’s a drawing comparing A. taxoides w/ C. Dirus & C. Lupus, in which A. toxoides appearsw to t be the smallest of the 3.
Supporting this, the “Paleobiology Database (http://museumu03.museumwww.naturkundemuseum-berlin.de/cgi-bin/bridge.pl?action=basicTaxonInfo&taxon_no=43778&is_real_user=1)
lays out the following statistics in which A. toxoides is estimated to have run about 108lbs.
“†Aelurodon taxoides Hatcher 1894 (bone-crushing dog)….
Average measurements (in mm): P4 length 28.2, P4 width 13.0, P4 area 365.4, M1 length 17.0, M1 width 19.9, M1 area 338.6, M2 length 8.41, M2 width 12.6, M2 area 105.6, p4 length 19.2, p4 width 11.0, p4 area 210.8, m1 length 30.1, m1 width 11.8, m1 area 355.2, m2 length 12.8, m2 width 9.08, m2 area 116.6
Estimated body mass: 48.8 kg based on m1 area”
Wang and Tedford don’t put have these high weights for Aelurodon. They do have it for some Epicyon, though.
The Aelurodon were more like wolves or African wild dogs, while the Epicyon were more like hyenas.
Accounts of a species of dog weighing close to half a ton, sound rather dubious to me as well. I would think that C. dirus represents the extreme in dog size. Based on the skeletal structure & metabolism needed to support a critter measurably larger than that, the result wud most likely look and act more like a bear than a dog.
so is the hind dewclaw (which doesn’t occur in all domestic dogs) a reversed HOX gene ? might be interesting to see what else that gene (for the hind dew) involves. I always thought the Beauceron, Briard and Great Pyr double dews was a polydactyl mutation. Could it be a reversal instead? (by the way, have that book. Worth getting).
Peggy Richter.
It’s Alx-4. homeobox knockout and then another knockout:
http://www.nature.com/scitable/topicpage/tandem-repeats-and-morphological-variation-40690
Thanks for the reference to the ALX-4 article. Surprisingly, it indicates that the double dewclaw of the Great Pyr differs from that of the Beauceron/Briards (since it said the only breed. I presume that they bothered to check the only other dog breeds known to have double dewclaws). Interesting.
Since I live near Los Angeles, I’ve been to the Page museum and seen the dire wolf displays. Sadly, despite the number of fossils found, the “saber tooth” is still the animal mostly studied. Pretty much folk looked at the Dire and just opted to conclude “large wolf”. I read a lot of stuff that assumes how fast they could run, etc, that have never bothered to compare the Dire to anything similar (like the top speed or running style of a well built mastiff. It just seems that studies of cats are more “in” than studies of canids. You see the same in science fiction. Guy has some exotic “felid” companion, not some “plain vanilla” canid 9 times out of 10. The exeptions are always notable because they ARE exceptions. Consequently, even though we’ve been in contact with dogs for longer than any other species, I think what we really know about them is less than we know about other, more exotic species.
Peggy Richter.