Comparison between Sarcophilus and Gulo

(writing in progress)

The Tasmanian devil and the wolverine may seem worlds apart. One is a marsupial isolated in Tasmania while the other, surviving the rigours of Siberia and Alaska, is related to weasels. However, the two species are remarkably similar owing to the process of convergent evolution. And understanding the differences that remain between them can deepen our understanding of the Tasmanian devil in ways not possible by comparisons within Australia.
 
Apart from a certain ‘appealingly diabolical’ image in the public mind, the Tasmanian devil and the wolverine resemble each other in many ways. Both species:

  • weigh about 10 kg, with male bigger than female
  • have notoriously strong jaws for their body size
  • have small eyes considering that they forage mainly in darkness
  • retain a social life despite foraging as solitary individuals
  • combine versatile predation with scavenging and an ability to eat bones
  • forage over great distances despite running with a lumbering canter rather than the neat trot used by canids, felids, and wombats
  • retain fore feet dexterous enough to handle food objects, and an ability to climb despite foraging mainly on the ground
  • have similar colouration: dark with erratic white markings on the chest, and an individually variable pattern of pale stretching from the shoulders along the flanks to the rump.

Evolutionary convergence is a favourite concept in biology textbooks. However, the examples usually given – such as kangaroos being Australia’s answer to deer, or echidnas being analogous to the aardvark – can seem rather far-fetched. One of the most convincing of these supposed ‘mirror-images’ is Tasmanian devil vs wolverine, but even in this case we will see that the differences can be more revealing than the similarities. Explaining certain disparities between these two, beyond the marsupial-eutherian difference or the polarities in their climates, may give us new understanding of the largest surviving marsupial carnivore.
 
So why have the Tasmanian devil and the wolverine evolved to be so similar despite being ancestrally unrelated and having such different reproductive modes?
 
Both mammals live in poor environments: nutrient-poor, fire- and flood-prone Australia and underlain by permafrost and covered by snow for most of the year in the subarctic. In both places, prey is sparse and carnivorous mammals cannot afford to be too demanding. In adaptation to these conditions, both the Tasmanian devil and the wolverine combine relatively small bodies – and therefore appetites - with outsize abilities to bite any large item that does present itself. The body size and leg length in both cases are finely balanced to limit demands while at the same time to allow enduring locomotion in search of what little food there is. When confronted, both forms display their impressive teeth. The odd colouration shared by Tasmanian devil and  wolverine combines general concealment in the dark with social self-advertisement: the whitish markings are like exclamatory insignia, allowing individuals to recognise each other in occasional encounters at distances just at the limits of olfaction and the vision of relatively small eyes. The patterns of colouration thus reflect societies so stretched, in these poor environments, that they seem to consist of loners in human terms.
 
Given these similarities between two independently evolved mammals, the disparities between the Tasmanian devil and the wolverine become all the more revealing. These include both morphological and behavioural differences.
 
Morphologically:

  • the head - and particularly the jaws - are far larger, proportional to the body, in the Tasmanian devil than in the wolverine, but the brain is smaller
  • the dentition of the Tasmanian devil remains typical of dasyurid marsupials while that of the wolverine remains typical of eutherian Carnivora
  • the feet are more powerful, with more prominent claws and rubbery pads, in the wolverine than in the Tasmanian devil
  • the eyes are emphasised by pale skin in the Tasmanian devil but hidden by a dark mask in the wolverine, and differ greatly in the orientation of the pupil (vertical in the Australian form but horizontal in the subarctic form)
  • whiskers (facial vibrissae) are far more prominent in the Tasmanian devil than in the wolverine.

Functionally:

  • the Tasmanian devil eats gregariously, calling in unrelated individuals to share large carcasses, whereas the wolverine eats alone, caches any leftovers, and tolerates only family members anywhere near its food
  • the Tasmanian devil, although not territorial, maintains communal latrines for olfactory communication, whereas the wolverine does not.
  • the fang-baring display of the Tasmanian devil – despite extremely wide opening of the mouth – is essentially bluff whereas that of the wolverine means business
  • in adulthood, the wolverine retains a far greater ability to climb trees than does the Tasmanian devil
  • the rates of metabolism and growth are far greater in the wolverine (which does not hibernate) than in the Tasmanian devil
  • longevity in the Tasmanian devil is half that in the wolverine, balanced by the greater number of infants per average litter (four) than in the latter (two).

In explaining these disparities, we can first discount the results of incongruities in climates. For example, there is no mystery as to why the wolverine is by far the furrier form, with feet broad enough to act as snowshoes. The difference in the orientation of the pupils may possibly be explained by excessive reflection of ultraviolet from snow: the wolverine has adapted by restricting this glare to a horizontal slit during daylight.
 
An important difference in the environments is that the wolverine risks occasional encounters with predators far larger than itself: the wolf and up to three species of bears. Although the Tasmanian devil formerly coexisted with the thylacine, the difference is that the wolf can fight gregariously whereas the thylacine fought alone or perhaps in pairs. Furthermore, there is competition between the wolverine and both the wolf and the brown bear for bones, whereas the dentition of the thylacine suggests that it left bones to the Tasmanian devil. These different predatory environments explain why the wolverine retains an ability to take refuge rapidly up trees, using the purchase of rubbery treads and sharp claws. Also thus explained is the subtlety of facial displays in the wolverine, which not only warns of a powerful bite but escalates the fang-baring expressions while at the same time hiding the eyes and thus the precise direction of attention of the confronted wolverine – which can also use its fore feet in self-defence.
 
The Tasmanian devil has, proportionately to its body size, the largest head of any marsupial or eutherian carnivore worldwide. The according differences in the dentitions amount to a case of quantity in the Tasmanian devil versus quality in the wolverine: the marsupial uses brute force of its molars to break bones whereas the wolverine uses fine adjustments of the jaw joints to apply precise pressure on its premolars and separately on specialised, small molars oriented at odds to the rest of the toothrows.
 
The extreme development of the facial whiskers in the Tasmanian devil remains to be fully explained, but it seems to be related to both the exceptionally large size of the head, and a habit of intraspecific ‘jaw-fencing’, a behaviour not seen in the wolverine or other eutherian carnivores. When the Tasmanian devil eats socially, the combination of whiskers and glaring eyes seem to help in maintaining sufficient personal distance.
 
Although the Tasmanian devil has been intensively studied, one aspect of its life history is seldom appreciated. This is the combination, in common with other dasyurids such as quolls and antechinuses, of a combination of reduced longevity and limited rates of reproduction (needs elaboration). At first glance it may seem that the Tasmanian devil reproduces more rapidly than does the wolverine, in keeping with the difference in longevity. However, this does not stand up to scrutiny because in fact the marsupial grows more slowly from conception to maturity than does any eutherian carnivore of similar body size – even one as beset by a difficult environment as the wolverine. The limited pressures from other predators in Australia have allowed the Tasmanian devil to breed relatively slowly (because of its relatively slow growth and despite the many newborns per litter), while relatively rapid turnover of generations have allowed it to respond to fluctuations in the availability of food according to cycles of climate and fire in Australia.
 
There is no real evolutionary convergence between the dentition of Gulo and that of Sarcophilus.

The dentition of Sarcophilus is essentially still that of a typical dasyurid marsupial, albeit scaled-up impressively. The dentition of Gulo is essentially still that of a typical member of the Carnivora (of which the most familiar examples are felids), but achieves its bone-crushing strength by being scaled DOWN in such a way that it is so compact that the teeth are unlikely to break no matter how much force is applied to them.
 
This concept is what seems to have been missed in previous comparisons of Sarcophilus with Gulo: that in a sense they not only fail to show any evolutionary convergence in dentition, but if anything have evolved in ‘opposite’ directions, with Sarcophilus going for increased size of jaws and teeth and compensating for the resulting breakage of the cusps by retaining the limited lifespan of dasyurids, whereas Gulo has gone for decreased size of the jaws and teeth so that its carnassials can be efficient at both shearing flesh and breaking bones, while its upper molar (which has no counterpart in Sarcophilus) can be brought to bear by precise sideways movement in the jaw joint, something apparently not used by any carnivorous marsupial.
  
I have found no suitable photos of the skeleton of Gulo, but this drawing does show how small the skull is relative to the body – the opposite of what we’ve seen in Sarcophilus. Because of the proportions shown by head to body, Sarcophilus looks like a ‘mighty mouse’ rather than a hyena, whereas Gulo looks like a small bear rather than a giant marten. This is relevant to our topic of bone-crushing jaws because it immediately raises the question ‘if the wolverine has such a proportionately small head, how does it crack large bones?’
 
https://s-media-cache-ak0.pinimg.com/originals/79/b5/76/79b57686b6a14a0c268dae5384993e3e.jpg
 
The following, again, is a drawing, but it is useful for its clarity. What is immediately noticeable in comparison with Sarcophilus is the development of the massive premolar on the upper jaw and its corresponding molar on the mandible. The cheek-teeth are far more differentiated and specialised in Gulo than in Sarcophilus. And the outer incisor on the upper jaw, i.e. that closest to the canine, is far larger than that in Sarcophilus; indeed Gulo has a kind of clamp in which the lower canine fits into a slot between upper canine and the nearby upper incisor, whereas Sarcophilus lacks this feature despite having more upper incisors (2 X 4) than Gulo (2 X 3).
 
http://img09.deviantart.net/00b7/i/2009/111/f/0/wolverine_skull_by_revelation_six.jpg
 
https://web.archive.org/web/20080527021506/http://www.wolverinefoundation.org/dentition.htm

The following shows how specialised the last upper premolar is in Gulo. This is a carnassial tooth typical of Carnivora, but it is also so stout that it may be used for breaking bones, without much risk of fracture of the cusps. And note the biggest difference of all from Sarcophilus: there is only one upper molar (compared with what is usually stated to be 4 in Sarcophilus), and this molar of Gulo looks nothing like those of Sarcophilus, being a) blunt and suitable for crushing bones, and b) set at right angles to the rest of the cheek-tooth row, providing broadened purchase or traction. What this means is that, although Gulo has fewer teeth than does Sarcophilus, its dentition is geometrically the more complex and by inference the more efficient relative to jaw size.
  
The following shows the two lower molars in Gulo: the small posterior-most tooth and the stout carnassial anterior to it. Compare this with the upper jaw above and note that there is no way for the upper molar (which projects inwards from the rest of the tooth row) to occlude any molar on the mandible unless the jaw is moved considerably sideways. What I infer from this is that, in order to crush bones or to grasp frozen meat/hide firmly, Gulo has to use considerable lateral mobility in its mandible. If so, this is, in a sense, the ‘opposite’ of the specialisation shown by Sarcophilus. The Australian mamma specialised in an extremely wide gape but there is no suggestion of unusual lateral mobility in the jaw-joint mechanism. Gulo is not known to gape widely but, as I infer from its dentition, it also has a kind of loose joint of the mandible with the rest of the skull, allowing it to apply a relatively small pair of jaws to large items with great force.
  
In Sarcophilus, the orbital socket is located about halfway between the front of the skull and the back of the skull. In Gulo the orbit is far closer to the front than to the back, and this is because the cranium is far longer in Gulo than in Sarcophilus. The point is that the skull shows how much larger the brain of Gulo is than that of Sarcophilus, relative to skull size. I suspect that this applies also relative to body size as a whole: Gulo is the brainier mammal.
 
http://wolverinefoundation.org/wp-content/uploads/2010/12/skull.gif
 
The following four photos show the skull of Gulo for direct comparison to that of Sarcophilus. This shows the clamping mechanism at the front of the jaw, and the far greater development of the carnassial mechanism at the rear of the jaw, in Gulo.
 
http://www.skullsunlimited.com/userfiles/image/variants_large_4328.jpg

https://www.nature-watch.com/images/products/large/806xx.jpg

http://www.boneroom.com/uploads/4/8/1/1/48118243/s521972503441136676_p1363_i1_w640.jpeg

http://www.educationalbiofacts.com/images/R-S302-Wolverine.jpg

The following two photos show the lower incisor row clearly. Please note that the lower incisors have a naturally staggered formation in Gulo, which means that the lower incisor row can maintain its strength and durability by a kind of ‘bracing’ in which the incisors are compacted into a short row. I have seen nothing like this kind of complexity in the lower incisor row of Sarcophilus.

What this means is that Gulo has a relatively narrow mouth compared with Sarcophilus, but when it latches on to an object with the front teeth, there is an extremely strong clamping mechanism because a) the lower canine fits between two large upper teeth, and b) the lower incisors are unlikely to break because they are arranged with such compactness and such mutual bracing.
 
http://www.skullsunlimited.com/userfiles/image/category5_species_1990_large_3.jpg

https://www.skullsunlimited.com/userfiles/image/category5_species_6600_large_3.jpg

 
The following several photos show the skull with the mouth open. The dentition resembles that of Felidae more than that of Sarcophilus, but is stronger than that of any cat, relative to skull size, because the dentition combines compactness with stoutness while at the same time retaining sharpness in a) the upper and lower canines, and b) the carnassial shear provided by the sliding occlusion of the last upper premolar against the first lower molar.
 
https://s-media-cache-ak0.pinimg.com/originals/72/e1/86/72e1861883ac7877f1b2505b2ecb3b13.jpg

http://img01.deviantart.net/9c7a/i/2004/260/a/0/wolverine_skull_1_by_rgstock777.jpg

http://img02.deviantart.net/b158/i/2010/342/5/2/wolverine_skull_by_zasalamell-d34hedj.jpg

http://images.hideandfur.com/inventory/wolverskullc.jpg

https://s-media-cache-ak0.pinimg.com/564x/bb/53/cf/bb53cf6f906043f31b92e87c0d643b52.jpg

http://img01.deviantart.net/0a74/i/2010/070/6/b/wolverine_skull_reference_2_by_lamelobo.jpg

To be continued...

(writing in progress)

Posted by milewski milewski, June 07, 2022 05:31

Comments

The following show that Sarcophilus is essentially plantigrade. This is important when considering its mobility as a scavenger and carnivore.
   
The following photo shows a domestic dog of about the same body mass as Sarcophilus. This carnivore is fully digitigrade, because it stands on its toes, not on its soles. Not only is the hind sole (i.e. the part of its hind leg below the hock) upright, it is more than upright because it actually inclines forward. Dogs never locomote using the sole of the hind foot, i.e. the metatarsal surface, for traction. Accordingly, the metatarsal ‘sole’ is fully furred and unworn and uncalloused in all dogs. Dogs provide the perfect illustration of a digitigrade stance and digitigrade locomotion, as in textbook descriptions of mammalian morphology.
 
Canis familiaris:
http://st.depositphotos.com/1654654/4933/i/950/depositphotos_49332893-stock-photo-cute-rat-terrier-dog-with.jpg
 
By contrast, Sarcophilus never stands with its metatarsal sole vertical. This surface, which is routinely used for traction, is bare in accordance with its normal wear on the ground surface. When Sarcophilus stands normally, this metatarsal sole is held closer to the horizontal than to the vertical. In the case of the following photo, the tarsal joint = heel = hock is virtually on the ground, something that would never be seen in even the smallest dog, provided the dog is adult and standing as opposed to sitting.
 
Sarcophilus:
https://cdn.audleytravel.com/960/%7Bheight%7D/79/141132064172125238053045079068174098082063007185.jpg
 
The wolverine is more like Sarcophilus than like dogs. However, one can find photos of the wolverine standing with its metatarsal sole closer to vertical than to horizontal. I have yet to find a similar photo for Sarcophilus.
 
Gulo:
http://c8.alamy.com/comp/D1Y0PN/wolverine-gulo-gulo-portrait-on-the-subarctic-tundra-in-sweden-scandinavia-D1Y0PN.jpg
 
The following is the closest to the above that I’ve found for Sarcophilus. As you can see, this animal is certainly standing as opposed to sitting, and yet its metatarsal sole is held at an angle of 45 degrees, not ca 100 degrees as seen in the terrier above. Although Sarcophilus is not fully plantigrade, it could certainly not be described as digitigrade.
 
http://www.flightcentre.co.uk/uk-travel-blog/files/2016/01/RS-3-Tasmanian-devil.jpg

The following shows what I consider to be the normal posture of the hind foot in Sarcophilus when it stands. Not only is the tarsal (heel) joint not fully extended, even the knee joint remains flexed (again, compare this with the terrier above).
 
https://petetheclown.files.wordpress.com/2016/02/img_8010_s.jpg

Posted by milewski 4 months ago (Flag)

The following shows that the wolverine sometimes stands in a typically plantigrade way. The hind soles are fully on the snow. Even the fore feet have the metacarpal surface far more in contact with the ground than would be the case in any dog or fox. In this way, the wolverine resembles Sarcophilus rather than canids. (his photo once again shows how small the head of Gulo is, relative to its body, for such a small-bodied animal, weighing less than15 kg.) 

Gulo gulo:

http://i130.photobucket.com/albums/p245/racophil/140740733_8f552a3db5_o.jpg 

The following shows the only way in which the Tasmanian devil can ‘stand up’ if unsupported by a tree or a wall. The important point is that its metatarsal surface = sole remains fully on the ground. Note also the bracing with the stout tail, something unnecessary in any adult dog. 

Sarcophilus harrisii:

https://s-media-cache-ak0.pinimg.com/736x/23/89/77/238977f3838226712bd791240d8acaa8.jpg

The following shows similar stance in the wolverine. I don’t think Gulo gulp needs to brace itself with its tail when ‘standing’ bipedally like this. Incidentally, this individual shows the maximum incidence of the irregular (and extremely variable individually) white markings on the chest in Gulo gulo. 

Gulo gulo:

https://s-media-cache-ak0.pinimg.com/736x/ef/c1/71/efc1715be377ebe1a833c35ca6d0d8cc.jpg 

The following confirms that when Gulo gulo ‘stands bipedally’ this is usually using a plantigrade stance. Incidentally, note the extreme contrast between these individuals in the extent of white on the chest. I doubt not that individuals can instantly recognise each other based on these insignia alone.

Gulo gulo:

https://s-media-cache-ak0.pinimg.com/564x/de/92/b8/de92b87602d69d0f4c585c8e556271e9.jpg

The following shows that the wolverine tends to keep its metatarsal surface on the ground even when it uses a tree for support. This and the previous two photos confirm that Gulo, like Sarcophilus, is in the plantigrade category. 

Gulo gulo:

http://cdn1.arkive.org/media/5C/5C151CFA-74EE-48F6-878C-685B01C74B30/Presentation.Large/European-wolverine-standing-on-hind-legs.jpg 

The following shows that the metatarsal surface, i.e. the sole, is bare of fur in the Tasmanian devil. This bareness is typical of plantigrade mammals and contrasts with the full pelage of the corresponding surface in all canids including foxes. Incidentally, note the faint pale spotting on this individual, which hearks back to its phylogenetic closeness to Dasyurus.

Sarcophilus harrisii:

https://media-cdn.tripadvisor.com/media/photo-s/01/75/b5/33/the-devils-like-to-sleep.jpg 

The following shows the typical stance of the Tasmanian devil, which is a plantigrade stance albeit with the bare metatarsal surface raised somewhat off the ground, i.e. with the heels somewhat off the ground. If Sarcophilus were fully, classically plantigrade the soles would be fully in contact with the ground and only lifted during actual locomotion. 

Sarcophilus harrisii:

https://www.phactual.com/wp-content/uploads/2015/01/tasmanian4.jpg

The following is another useful view of the hind feet in the Tasmanian devil. Note that even the fore feet have an extensive bare surface, which would not be the case in a classically digitigrade mammal such as the dog.

Sarcophilus harrisii:

http://cdn.newsapi.c

Posted by milewski 4 months ago (Flag)

MORE ON DOMESTIC DOG

The following shows how different the dingo is from the wolverine or Tasmanian devil: when it stands the metatarsal surface is vertically upright, fully furred, with no contact with the ground unless the animal sits fully. The dingo is a typical example of a digitigrade carnivore, and this stance is more conducive to rapid locomotion and endurance than is a plantigrade stance. 

Canis familiaris dingo:

https://pommepal.files.wordpress.com/2015/07/dingo_2244x2135.jpg?w=690&h=656

The following again shows how upright the metatarsus is in the dog. One never sees Sarcophilus standing like this.

Canis familiaris:

http://www.petyourdog.com/uploads/dog_pictures/large/1358652967~-Siberian-Indian-Dog-is-looking-back.jpg

The following shows the ability of canids to stand bipedally while keeping the metatarsal surface fully vertical, i.e. dogs can remain in the digitigrade stance even when reducing their support to the hind legs alone. Sarcophilus, as we will see below, cannot do this.

Canis familiaris:
https://previews.123rf.com/images/adogslifephoto/adogslifephoto1402/adogslifephoto140200117/25849517-Labrador-Retriever-and-Shepherd-mixed-breed-dog-standing-on-his-hind-legs-and-begging-for-a-treat-Stock-Photo.jpg 

The following shows that dogs can also stand bipedally with the metatarsal surface on the ground, as if rearing up while sitting. However, I suspect that only the smallest breeds of dogs (and infants/juveniles of larger breeds) can perform this relatively plantigrade posture, which demands a degree of flexibility of the tarsal joint of which I think larger dogs are incapable.

Canis familiaris:

http://media.gettyimages.com/photos/dog-standing-on-hind-legs-picture-id87469541?s=170667a&w=1007

Posted by milewski 4 months ago (Flag)

The following shows the typical stance of the Tasmanian devil, which is a plantigrade stance albeit with the bare metatarsal surface raised somewhat off the ground, i.e. with the heels somewhat off the ground. If Sarcophilus were fully, classically plantigrade the soles would be fully in contact with the ground and only lifted during actual locomotion. 
Sarcophilus:
https://www.phactual.com/wp-content/uploads/2015/01/tasmanian4.jpg 
The following is another useful view of the hind feet in the Tasmanian devil. Note that even the fore feet have an extensive bare surface, which would not be the case in a classically digitigrade mammal such as the dog. 
Sarcophilus:
http://cdn.newsapi.com.au/image/v1/102fa0f51f8d339af17035c78e43938f 
The following again shows how bare the metatarsal sole is in the Tasmanian devil. A hind foot like this cannot be described as digitigrade. The obvious dexterity of the fore foot is also something not associated with a digitigrade stance. 
Sarcophilus:
http://i.dailymail.co.uk/i/pix/2016/10/17/03/39726EB800000578-3842476-image-a-22_1476670419113.jpg 
The following again shows the typically plantigrade-looking hind foot of the Tasmanian devil, which is quite different from the hind foot of a dog and more similar to that of a possum, bear or even (except for the great difference in the incidence of a big toe) monkey. 
Sarcophilus:
http://www.mrwallpaper.com/wallpapers/tasmanian-devil-baby.jpg 
The following shows the small size of the hind foot of the Tasmanian devil relative to its fore foot. In typically digitigrade mammals such as canids, the hind foot is far longer than the fore foot. 
Sarcophilus:
https://scienceandmedia.files.wordpress.com/2012/08/p1090144.jpg 
The following shows the fore foot of the Tasmanian devil. The fact that the bare surface on palm and wrist are so extensive is in keeping with the use of an extended area for traction during locomotion. If this were a digitigrade limb, the bare surface would be far more restricted and divided (visualise the paw of a dog).
Sarcophilus:
http://www.abc.net.au/science/scribblygum/April2001/img/f_Devilhand.jpg 
The following shows that the metatarsal surface of the wolverine is furred. However, this does not necessarily indicate a digitigrade stance because the wolverine, adapted to snow and ice, has ‘snowshoe’ feet in a way quite unnecessary in Sarcophilus. 
Gulo:
http://online.sfsu.edu/bholzman/courses/Fall00Projects/wolverinefigure5.jpg 
The following shows that, although all four feet are far larger in Gulo than in Sarcophilus, there is less disparity between fore and hind in Gulo than in Sarcophilus. Both Gulo and Sarcophilus are essentially plantigrade, but in addition to being plantigrade Sarcophilus has a relative diminution (and flexion while standing) in the whole hind limb. 
Gulo:
https://s-media-cache-ak0.pinimg.com/236x/19/c5/cb/19c5cb0d90da125a9dc5648e334f9a61.jpg
The following shows that, although the metatarsal ‘sole’ is not held upright in Gulo as it is in canids, nevertheless one cannot classify Gulo (or Sarcophilus) as classically plantigrade because in normal stances the tarsal joint = heel = hock is in fact raised above the ground surface. And as you can also see in this photo there is corresponding flexibility in the fore foot, which functions in a fully plantigrade way when maximum traction is needed, but can be raised partly towards a digitigrade stance when alleviated of its weight. 
Gulo:
http://l450v.alamy.com/450v/brdbyr/wolverine-gulo-gulo-largest-member-of-weasel-family-brdbyr.jpg 
In the following photo, we see the wolverine standing more like a digitigrade mammal (e.g. dog) than like a plantigrade mammal (e.g. bear). Sarcophilus rarely stands with its metatarsal surface so close to upright. Both Gulo and Sarcophilus are plantigrade but Gulo is less so than Sarcophilus, in keeping with the fact that the fore- and hindquarters show less disparity in development in Gulo than in Sarcophilus. 
Gulo:
http://l7.alamy.com/zooms/debd533648464d82a82dae507aaca67f/wolverine-standing-on-snow-in-woodland-wetlands-finland-ey5mcb.jpg 
The following reminds us that even in Gulo there remains some tendency to keep the metatarsal surface (sole) on the ground when standing, which is why this mammal must be classified (with qualifications) as plantigrade. 
Gulo:
https://thumbs.dreamstime.com/z/wolverine-gulo-gulo-standing-its-natural-habitat-52702145.jpg 
The final photo shows how the hind foot is used in normal running locomotion in the Tasmanian devil. The heel = ankle = hock is kept off the ground as in digitrade mammals. If the Tasmanian devil were fully plantigrade like a bear, the full surface of the metatarsal part of the foot would contact the ground with every stride while running. Incidentally, note the fat deposit in the tail, something that I do not thing applies to Gulo. 
Sarcophilus:
https://us.123rf.com/450wm/izanbar/izanbar1512/izanbar151200032/49043658-tasmania-d

Posted by milewski 4 months ago (Flag)

BODY SIZE RELATIVE TO HUMAN

When hand-reared with plenty of food, both Gulo and Sarcophilus reach their maximum sizes. However, as the following photos show, the maximum size of Gulo far exceeds that of Sarcophilus. 

Even if the wolverine depicted here (female) is only 20 kg whereas the largest of the Sarcophilus depicted here (if male) is as much as 7 kg, we have a three-fold difference in body mass and this is despite the expectation based on sexual dimorphism, which is that in both species the male is more massive than the female. 

The following is the same individual to which I referred yesterday, the body mass of which I estimated to be as much as 25 kg. Note how much smaller the head of the wolverine is than the head of the man. This individual wolverine is said to be female. 

https://www.outsideonline.com/sites/default/files/styles/img_850x480/public/wolverine-steve-kroschel_h.jpg?itok=Rr-sANlI

http://www.kroschelfilms.com/sites/default/files/images/webpage019.jpg 

The following shows the true size of Sarcophilus under comparable conditions and with a comparable scale of reference. The Tasmanian devil is not even half of the body mass of the wolverine above, yet its head is no smaller relative to the size of the man’s head, not so? 

https://i.ytimg.com/vi/ZNOIkC9zBzA/maxresdefault.jpg

http://nnimgt-a.akamaihd.net/transform/v1/crop/frm/storypad-c9uxyP9vLBnGRF7ifn73Fv/e1392f79-82b8-401a-8b66-086c61f19bc8.jpg/r0_1_1200_676_w1200_h678_fmax.jpg

http://nnimgt-a.akamaihd.net/transform/v1/crop/frm/storypad-c9uxyP9vLBnGRF7ifn73Fv/63bad729-1f3e-4f43-9e33-d8f3753de8c1.jpg/r0_1_1200_676_w1200_h678_fmax.jpg

http://www.smh.com.au/ffximage/2008/02/13/tassiedevil_140208_wideweb__470x322,0.jpg

https://i.ytimg.com/vi/aw87M8MVGBM/hqdefault.jpg

Posted by milewski 4 months ago (Flag)

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