Perodicticus and Amargasaurus: together at last!

Is it a serious breach of netiquette if I post my comments on the SV-POW! article here on Tet Zoo instead? Of well, here goes...

Hardly known and rarely mentioned is that the last four (or so) cervical neural spines and first three thoracic spines of the Potto Perodicticus potto (a peculiar African strepsirrhine primate, closely related to the Asian lorises) protrude from the skin of the neck and shoulders, have sharply pointed tips, and are usually stated to serve a defensive function [...] The spines donât protrude as naked bone (though this was claimed by Ivan Sanderson), but are covered with skin and some hair, and form a series of tubercles in the live animal. When threatened, a potto is supposed to hide its head and point those protruding neck spines towards the danger, sometimes even butting the predator or aggressor with the spines. Other functions have been suggested for the spines, but a defensive function remains most popular and in the absence of any special knowledge Iâll go with the majority.

Considering how little there seems to be published on the subject of these potto spines I don't know if there is such a thing as a majority view explanation for their function. I do know, though, that Walker (1970) didn't accept Sanderson's claims about the supposed use of the spines in defence*. And it certainly is hard to imagine against what potential potto predator these 'spines' in the neck would be effective. Pythons and other large snakes, for example, are not deterred by the far more formidable spines of porcupines (Duarte, 2003). In other parts of the world, large owls (e.g., Bubo), regularly prey on hedgehogs. And I highly doubt that the potto's spines offer any protection whatsoever against, say, leopards or chimpanzees (both confirmed if infrequent predators of pottos - see Zuberbühler & Jenny, 2002; Pobiner et al., 2007).

* Instead of a protective function, Walker (1970) favoured the explanation that the potto's elongated spines are used for peaceful tactile communication between conspecifics.

References:

Duarte, M.R. 2003. Prickly food: snakes preying upon porcupines. Phyllomedusa 2, 109-112.

Pobiner, B.L., DeSilva, J., Sanders, W.J. & Mitani, J.C. 2007. Taphonomic analysis of skeletal remains from chimpanzee hunts at Ngogo, Kibale National Park, Uganda. Journal of Human Evolution 52, 614-636.

Walker, A. 1970. Nuchal adaptations in Perodicticus potto. Primates 11, 135-144.

Zuberbühler, K. & Jenny, D. 2002. Leopard predation and primate evolution. Journal of Human Evolution 43, 873-886.

Dartian, I would say that it's ok to put potto-themed comments here, while amargasaur-themed ones should go on SV-POW! Anyway...

I don't know if there is such a thing as a majority view explanation for their function

I'd say there definitely is a 'majority view': I looked at, I dunno, ten or so sources on the potto and all said flat-out that self-defence is the main explanation. Sanderson was certainly not the only one to say it, though his claims were boldest (as they usually were).

Maybe if the chupie does turn out to be a real animal (unlikely, but one can never know), it will turn out to be a highly derived New World primate. Perhaps an island dwelling species that developed into a carnivore to take advantage of the lack of ground predators (such things do happen on islands, and the chupie stories did start in Puerto Rico after all), or else it would be a New World Monkey adapted to live like a "solitary chimpanzee" or something.

Then again, it wouldn't be a potto descendant, seeing as pottos are old world.

Perhaps the lower parts of Amargrasaurus' spines were covered in skin, to make it appear larger. But at the same time the extremities were sharp and pointed, to ward off predatory theropods.

I love the defensive function, but G.S.Paul's awesome idea that they could be "clattered/clacked" to attract a mate during a "dance" was awesome.

If you want my opinion as to what the chupacabra is, I think it's a highly contrived form of domestic dog. Look at the resemblance between a chupacabra and a snarling Chihuahua, for example.

Regarding the uniqueness of the potto's elongated spines...

In 1996, Jeffrey Schwartz* described a new species of extant lorisid, the 'false potto' Pseudopotto martini. His new species description was based on skeletal material of two museum specimens, the skull of a subadult and the skull & the complete skeleton of an adult individual. The false potto has never been observed in its natural habitat, and it may be added that the geographical place of origin given for these specimens is rather vague (the holotype, for example, is listed as being from 'Equatorial Africa'). Unsurprisingly, the taxonomic validity of Pseudopotto is far from universally accepted and it's been suggested that these two specimens are, in fact, just ordinary pottos.

* For those who wonder: yes, this is Jeffrey 'orangutans-are-the-closest-living-relatives-of-humans' Schwartz.

Nevertheless, in the context of Darren's post it is of interest to note that the type specimen (the adult with the complete skeleton) has only moderately elongated cervical/thoracic spines - much shorter than those of a typical Perodicticus potto individual. This could suggest that the degree of elongation of the spines in Perodicticus potto is quite variable. (Or, alternatively, it could suggest that the 'false potto' is a valid taxon after all. But we'll need more data to be able to assess that.)

Reference:

Schwartz, J.H. 1996. Pseudopotto martini: a new genus and species of extant lorisiform primate. Anthropological Papers of the American Museum of Natural History 78, 1-14.

I was planning to cover Pseudopotto here at some stage; have always been interested in the controversy over its validity.

I was planning to cover Pseudopotto here at some stage

Great! Primatological posts are somewhat underrepresented here on Tet Zoo (if you don't mind me saying so).

I'd say that the whole of Euarchontoglires is horribly under-represented. There are whole groups that I've barely touched. It's all down to time.

Here's a different apotasaurus:

http://ursulav.deviantart.com/art/Apotasaurus-139594981

As to underrepresentation of Euarchontoglires...
There have been some nice Rodent posts, and there was the Version 1 post on the utter weirdness of rabbits, so don't feel TOO guilty, Darren! (Me, I'm amazed by how much you DO find time to blog about. If you are fishing for signs of what the audience would like, I'm a Mammal chauvinist, and would love to read about Euarchontoglires, Laurasiatheria, Afrotheria, Xenarthra, other Eutheria, Metatheria, Monotramata, Allotheria....)

I've always believed that the presumed sails on stuff like Spinosaurus or Ouranosaurus would likely be for display, so it makes perfect sense to me. Defensive? Not so sure on that. Structures like that, big and garish, in modern animals seem to relate to internalised behaviour, territory, sex, whatever, , rather than external pressures like predation.

But what do I know?

I just imagined that male Amagsaurus lowered necks until the spines pointed forwards, and tried to stab each other. Like horns of Oryx multiplied five times!

BTW - any link to the soft-tissue crests of other diplodocids?

"My favourite 'fact' about potto neck spines: they demonstrate a link with the Chupacabras"

- This is a great example of convergent evolution:

Pottos are to Chupacabras as Koalas are to Drop Bears. :-)