It never fails. Whenever I visit a zoo's African wild dog exhibit someone inevitably asks "Are those hyenas?", and when I visit spotted hyena enclosures I often hear the question "Are those dogs?" These carnivores, known to scientists as Lycaon pictus and Crocuta crocuta (respectively), are only distant cousins, but the vague similarities shared between them often cause people to confuse one with the other.
There are a few quick and dirty ways to tell them apart. Spotted hyenas, as their name indicates, have a coat flecked with solid spots while the fur of each African wild dog carries a distinctive pattern of caramel, white, black, and dark brown. They are also shaped a little bit differently; hyenas are stockier, with relatively shorter midsections, while African wild dogs have a longer, more lanky appearance. And, if you are really an astute observer, you might notice that African wild dogs lack something your more familiar domestic dogs have; a fifth toe, or dewclaw, on the forelimb. It is thought that this loss might be an adaptation which allows African wild dogs to more efficiently run after prey over long distances, but when did this happen, and how do these canids relate to other dogs?
To figure out the history of Lycaon we need to turn to the fossil record, and a report just published in the Journal of Paleontology proposes that a recently-discovered fossil dog may hold the key to he origins of the painted carnivores. In the 1-2 million year old deposits of Sterkfontein, South Africa (not far from where Australopithecus sediba was found), paleontologists Adam Hartstone-Rose, Lars Werdelin, Darryl de Ruiter, Lee Berger, and Steven Churchill recovered the remains of a previously unknown fossil dog. It shows some peculiar similarities with living Lycaon.
The new canid, named Lycaon sekowei, is represented by several specimens from two different time periods. The first group of fossils, dated to about 1.6-1.9 million years ago, consists of several bits of jaw with the teeth still anchored inside. The second, appraised to be about 1 million years old and tentatively referred to the new species, together make up nearly 40% of a skeleton, meaning that the anatomy of the carnivore is about 70% known (i.e. once you have the right femur, you also know what the left one looks like.) It appears to have been the largest canid, living or fossil, ever found in Africa, but what really makes it special are the details of its teeth and limbs.
As vertebrate paleontologists know well, a tooth can tell you a lot about a fossil mammal. Despite the fact that animals with similar diets often have similar teeth, the distinctive patterns of cusps and ridges are often useful in determining what kind of animal a fossilized tooth represents. In the case of Lycaon sekowei, it has peculiar accessory cusps on its premolars that are only seen in the canid genus Lycaon, and in a direct comparison the premolars of the new species more closely resemble those of Lycaon pictus than the gray wolf (Canius lupus) or the fossil wolf Xenocyon.
The dental resemblances between Lycaon pictus and Lycaon sekowei places the fossil species in a good position to be a potential ancestor of the living species, but if this is correct then there was a significant change elsewhere in the skeleton during the transition. When the scientists looked at the skeleton of the tentatively referred specimen they found part of the first metacarpal, or part of the digit which has been lost in living African wild dogs. Supposing that Lycaon sekowei is the ancestor of Lycaon pictus, the 1 million year old specimen is correctly referred to the new fossil species, and the loss of the first digital is an adaptation to hunting behavior centered around running after prey for significant distances, then the presence of this bone in Lycaon sekowei may mean that the cursorial hunting techniques of African wild dogs were relatively recent developments.
There are a lot of assumptions packed up into this hypothesis, however, and the ancestral status of Lycaon sekowei cannot be taken as a certainty. Based upon the evidence reviewed by the paleontologists it appears that Lycaon sekowei was a close relative of living African wild dogs. It certainly had a very similar dentition well-suited to a diet consisting mostly of meat, but the rarity of fossil canid remains from Africa, as well as the tentative referral of the more complete skeleton to the species, makes me wary of saying it was an ancestor of living African wild dogs just yet. Lycaon sekowei is the best candidate for an ancestor of African wild dogs discovered to date, but without a more complete array of fossil material we cannot yet be sure whether it was truly an ancestor of African wild dogs or instead a close relative of that as-yet-undiscovered ancestor.
ADAM HARTSTONE-ROSE, LARS WERDELIN, DARRYL J. DE RUITER, LEE R. BERGER and STEVEN E. CHURCHILL (2010). THE PLIO-PLEISTOCENE ANCESTOR OF WILD DOGS, LYCAON SEKOWEI N. SP Journal of Paleontology, 84 (2), 299-308 : 10.1666/09-124.1
You might want a paragraph break in that second paragraph or something... you switch from comparing wild dogs with hyenas to comparing them with other canids, which, since you haven't specified exactly *how* distant of cousins hyenas (as feliform carnivorans) are, is possibly confusing. =)
The last time I was in London zoo, a parent standing next to me said to her child, "Look, hyenas!" in front of the wild dogs enclosure. I took a photo from my vantage point. Can you spot the big clue that these are not hyenas?
Geez Ed, people go to the zoo to make faces at the animals, not to READ!
I find it quite interesting that the large cursorial hypercarnivorous pack-hunting canids (Canis, Lycaon, and Cuon) appear to be close relatives and share a common ancestor. I wonder where Xenocyon fits, since it has been proposed to be directly ancestral to Lycaon, Cuon and Cynotherium, but has also been subsumed into Canis.
I also wonder if pack-hunting is basal behaviour or evolved multiple times in Canis, or whether it's more constrained by size and ability to subsist on small prey like rodents. Coyotes and jackals live in pairs or small family groups but mostly hunt alone, although they do team up to take on large prey on rare occasions. The grey wolf and red wolf are large enough to depend more on ungulates. Is there any direct evidence that the dire wolf or any of the other extinct "wolves" lived and hunted in packs? I'm not sure about the phylogeny of the extant canids, but I would believe that pack-hunting evolved repeatedly in Canis.
Apart from this clade, the only extant social canid that hunts in packs is the bush dog (Speothos). I'm left wondering if the Late Pleistocene Protocyon and Theriodictis, which were large hypercarnivorous canids that lived in open environments of South America show any adaptations for hunting in packs as well.
Speaking of which, are there any hesperocyonine or borophagine canids that are known to have hunted in packs?
Why did they make the earlier, less complete, remains the type?
Alex; Yes, the transition is a little messy, but I wanted to keep the observation about people at zoos. I probably should have chucked it, but oh well.
Andreas; I think because the jaw fragments showed more diagnostic features which could be linked to Lycaon (and therefore made a better case for being an ancestor). The partial skeleton, while more complete, seems to lack parts of the skeleton which would have definitively placed it within Lycaon, and, as the authors note, they are only tentatively referring it to the new species.
Ed and Jason; I am always amazed by the fact that people ask questions like "What is that thing?" at the zoo but don't read the big signs all around the enclosures. Okapi exhibits are the best example of this - every time I visit the one at the Bronx Zoo I hear lots of off-the-cuff hypotheses on what the animal is but almost no one reads the signs explaining what the animal is.
I don't really have a problem with the loss of dew claws, they are sometimes a problem for running dogs (mine break theirs frequently, usually just the nail breaks off, several now have stumps.) It make good evolutionary sense if they were switching from a more open area to an area with more brush. It would be interesting to find a fossil with a reduced claw to sort of confirm things.:)
The last time I was in London zoo, a parent standing next to me said to her child, "Look, hyenas!" in front of the wild dogs enclosure.
Certainly a lot of people misidentify zoo animals to their kids, but I have some sympathy for them in this case. How would you know -- if you didn't already know -- that hynenas and hunting dogs were not both names given to one animal? Go over to the cougar enclosure and see if they have big letters spelling out all its names; they'd better not or you'd never see past them to see the animal. :)
Do we have any idea how the african hunting dog relates to the jackal, wolf, coyote in
every time I visit the one at the Bronx Zoo I hear lots of off-the-cuff hypotheses on what the animal is but almost no one reads the signs explaining what the animal is.
"Don't you ever become discouraged seeing so much creationist nonsense?" I could only reply honestly; "Of course I do.
BLOGS WE NEED TO BE CREATIVE....