Weasel Clan
Today, we have a selection of mustelids: members of the weasel family. This is a very long and picture-heavy post, but it's worth it. Come explore!
Mustelids are an incredibly varied lot, and the family is a large one including otters, badgers, wolverines, martens, ferrets, weasels, and polecats. They are all carnivores, but of a particularly primitive design. This body type, long with short limbs and a long tail, has been successful for over 50 million years, with a notable start in the creodonts and miacids, early carnivorous mammals. In fact, the ancestor of all modern carnivorans is thought to be Miacis, a genus of weasel-like creatures that gave its name to the miacid family.
The weasel family doesn't diverge much from this basic and very efficient model. There is, however, considerable variation within the family itself. Today we'll look at five skulls: a male fisher, a female fisher, a marten, a river otter, and an American badger.
Let's get going!
Here is a pair of fishers, (Martes pennanti). They are strongly sexually dimorphic, with adults ranging from about five to fifteen pounds. Fishers have retractile claws like a cat's, and these, along with their slender body shape, allow them to pursue prey into trees or burrows. They are excellent climbers - despite their name, they don't fish.
The one on the left is female, and has been painted in black ink (there will be pictures of her unpainted later on). The one on the left is male. Note the size difference. Remember when I said dimorphic?
A side view. You can really see the differences in their sagittal crests here. Females don't develop crests nearly as strong as males'.
This is the female above, before she was painted. You can see that her nasal bones have all fused together. Nasal sutures fuse early in the weasel clan, so this does not indicate the advanced age that it would in a dog or coyote. Nevertheless, as we have seen, a male of this age would have wider cheekbones and much more prominent sagittal crest.
You can see how delicate the cheekbones are in this picture. All members of the weasel family have particularly elegant cheekbones. It's one of those surprising features that really appeal to me.
Here's the male.
See what I mean about the cheekbones? Handsome animals.
The fisher's teeth are really impressive, and you can bet that with sagittal crests like that, they can deliver savage bites.
Here you can see the respectable fangs, as well as the upsweep of the cheekbones and the strong ridge of the sagittal crest.
The underside of the cranium. There's something particularly attractive about the arrangement of the lines and channels and projections here. It's a very beautiful skull.
This picture really reminds me of Fish. Golly, I wonder why?
Next we have a marten. Martes americana. The American marten is a wee little beastie, as you can see from its wee little skull.
Pointy little bugger, though.
I love the beautiful architecture of the cheekbone here, as it arches across toward the front of the skull. I love the area between the orbit, the infraorbital foramen, and the space below the cheekbone. It's just beautiful.
The marten has a large, round braincase, and very little in the way of a sagittal crest.
I have said that I have small hands, yes?
Look at that little jawbone!
A nice view of the underside of the skull. So delicate!
Now we come to something far less delicate, the American badger, Taxidea taxus.
At the crown of the skull are the massive occipital crests. These crests provide anchor points for the powerful neck muscles. The badger, however, has a very flat head, and exhibits almost no sagittal crest at all.
This is an adult specimen, but not an old one; the nasal bones have fused but the teeth show little wear.
Compare the size of the eyesockets to the size of the nasal opening. Also note how heavy those teeth are.
The badger's head is shaped like a flat wedge.
Here you can see the badger's impressive dentition. Its teeth are strong and stout, and adapted to a varied diet that includes some vegetable material. You can see that it has rudimentary grinding surfaces on its rearmost teeth.
Here you can see the large auditory bullae, the round bulbs on either side just behind the joint of the jaw. Large auditory bullae, or well-rounded bullae, are general indicators of a good sense of hearing. Badgers have better hearing than one might expect.
Here is a northern river otter, (Lontra canadensis).
A strange skull, quite distinctive.
You can see some similarities here to the badger skull.
Viewed from straight above, you can see the wide-bowed cheekbones, and even the rear of the infraorbital foramina -- the little openings between eye and nose, which are not so little in the otter.
The wide cheekbones and very large infraorbital foramina are even more apparent here. The nerves leading to the whiskers and parts of the face enter through the infraorbital foramen; the larger the opening, the more nerves.
The worn and broken teeth provide a clue to the animal's age.
The otter's skull is wide and flat to reduce drag in the water.
Here you can see that the jaw is firmly attached to the skull. The groove of the mandibular fossa on the upper part of the skull receives the ridge of the mandibular condyle on the bottom jaw, and in mature otters the edges of the groove often grow to hold the jaw firmly to the cranium.
The lower jawbones cannot be disarticulated from the top of the skull without separating them at the front suture and sliding them out independently.
Again, this is an older animal, as evident from the extensive wear to the teeth. Still, it is an impressive display.
Otters are devilishly cute animals, so cute it is easy to forget that they are pointy.
I love this shot, too, for the infraorbital foramina, visible to the sides of the canines. They are absolutely enormous!
Seen from below, it's obvious the otter doesn't have very good hearing. The auditory bullae are small, flat, and somewhat deformed.
For size comparison, here's a roundup of skulls:
Top row, left to right: coyote, gray wolf, coyote, Canadian lynx. Bottom row, left to right: badger, otter, red fox, raccoon, female fisher. Click through and click "all sizes" to get a large version of this photo.
Comparing the palates of various skulls. From top left to bottom right: coyote, gray wolf, coyote, raccoon, lynx, badger, red fox, female fisher.
And the mustelids all together. Clockwise from left to right, male fisher, female fisher, marten, otter, and badger. You can really see how small the marten skull is with the CD for comparison.
Hope you enjoyed the guided tour. I really love this family. They are so varied and so beautiful! I want to add a least weasel (Mustela nivalis) someday, as it's the smallest of the entire order of Carnivora.
Mustelids are an incredibly varied lot, and the family is a large one including otters, badgers, wolverines, martens, ferrets, weasels, and polecats. They are all carnivores, but of a particularly primitive design. This body type, long with short limbs and a long tail, has been successful for over 50 million years, with a notable start in the creodonts and miacids, early carnivorous mammals. In fact, the ancestor of all modern carnivorans is thought to be Miacis, a genus of weasel-like creatures that gave its name to the miacid family.
The weasel family doesn't diverge much from this basic and very efficient model. There is, however, considerable variation within the family itself. Today we'll look at five skulls: a male fisher, a female fisher, a marten, a river otter, and an American badger.
Let's get going!
Here is a pair of fishers, (Martes pennanti). They are strongly sexually dimorphic, with adults ranging from about five to fifteen pounds. Fishers have retractile claws like a cat's, and these, along with their slender body shape, allow them to pursue prey into trees or burrows. They are excellent climbers - despite their name, they don't fish.
The one on the left is female, and has been painted in black ink (there will be pictures of her unpainted later on). The one on the left is male. Note the size difference. Remember when I said dimorphic?
A side view. You can really see the differences in their sagittal crests here. Females don't develop crests nearly as strong as males'.
This is the female above, before she was painted. You can see that her nasal bones have all fused together. Nasal sutures fuse early in the weasel clan, so this does not indicate the advanced age that it would in a dog or coyote. Nevertheless, as we have seen, a male of this age would have wider cheekbones and much more prominent sagittal crest.
You can see how delicate the cheekbones are in this picture. All members of the weasel family have particularly elegant cheekbones. It's one of those surprising features that really appeal to me.
Here's the male.
See what I mean about the cheekbones? Handsome animals.
The fisher's teeth are really impressive, and you can bet that with sagittal crests like that, they can deliver savage bites.
Here you can see the respectable fangs, as well as the upsweep of the cheekbones and the strong ridge of the sagittal crest.
The underside of the cranium. There's something particularly attractive about the arrangement of the lines and channels and projections here. It's a very beautiful skull.
This picture really reminds me of Fish. Golly, I wonder why?
Next we have a marten. Martes americana. The American marten is a wee little beastie, as you can see from its wee little skull.
Pointy little bugger, though.
I love the beautiful architecture of the cheekbone here, as it arches across toward the front of the skull. I love the area between the orbit, the infraorbital foramen, and the space below the cheekbone. It's just beautiful.
The marten has a large, round braincase, and very little in the way of a sagittal crest.
I have said that I have small hands, yes?
Look at that little jawbone!
A nice view of the underside of the skull. So delicate!
Now we come to something far less delicate, the American badger, Taxidea taxus.
At the crown of the skull are the massive occipital crests. These crests provide anchor points for the powerful neck muscles. The badger, however, has a very flat head, and exhibits almost no sagittal crest at all.
This is an adult specimen, but not an old one; the nasal bones have fused but the teeth show little wear.
Compare the size of the eyesockets to the size of the nasal opening. Also note how heavy those teeth are.
The badger's head is shaped like a flat wedge.
Here you can see the badger's impressive dentition. Its teeth are strong and stout, and adapted to a varied diet that includes some vegetable material. You can see that it has rudimentary grinding surfaces on its rearmost teeth.
Here you can see the large auditory bullae, the round bulbs on either side just behind the joint of the jaw. Large auditory bullae, or well-rounded bullae, are general indicators of a good sense of hearing. Badgers have better hearing than one might expect.
Here is a northern river otter, (Lontra canadensis).
A strange skull, quite distinctive.
You can see some similarities here to the badger skull.
Viewed from straight above, you can see the wide-bowed cheekbones, and even the rear of the infraorbital foramina -- the little openings between eye and nose, which are not so little in the otter.
The wide cheekbones and very large infraorbital foramina are even more apparent here. The nerves leading to the whiskers and parts of the face enter through the infraorbital foramen; the larger the opening, the more nerves.
The worn and broken teeth provide a clue to the animal's age.
The otter's skull is wide and flat to reduce drag in the water.
Here you can see that the jaw is firmly attached to the skull. The groove of the mandibular fossa on the upper part of the skull receives the ridge of the mandibular condyle on the bottom jaw, and in mature otters the edges of the groove often grow to hold the jaw firmly to the cranium.
The lower jawbones cannot be disarticulated from the top of the skull without separating them at the front suture and sliding them out independently.
Again, this is an older animal, as evident from the extensive wear to the teeth. Still, it is an impressive display.
Otters are devilishly cute animals, so cute it is easy to forget that they are pointy.
I love this shot, too, for the infraorbital foramina, visible to the sides of the canines. They are absolutely enormous!
Seen from below, it's obvious the otter doesn't have very good hearing. The auditory bullae are small, flat, and somewhat deformed.
For size comparison, here's a roundup of skulls:
Top row, left to right: coyote, gray wolf, coyote, Canadian lynx. Bottom row, left to right: badger, otter, red fox, raccoon, female fisher. Click through and click "all sizes" to get a large version of this photo.
Comparing the palates of various skulls. From top left to bottom right: coyote, gray wolf, coyote, raccoon, lynx, badger, red fox, female fisher.
And the mustelids all together. Clockwise from left to right, male fisher, female fisher, marten, otter, and badger. You can really see how small the marten skull is with the CD for comparison.
Hope you enjoyed the guided tour. I really love this family. They are so varied and so beautiful! I want to add a least weasel (Mustela nivalis) someday, as it's the smallest of the entire order of Carnivora.