The Scaled Mammal

Today is World Pangolin Day; a day to reflect on the endangered, but also incredibly interesting and special nature of this mammal (here’s Dr. John Hutchinson of What’s in John’s Freezer on the many peculiarities of pangolins).

The pangolin, Manis spp. (Manidae, Pholidota, the only extant members of this group) is one of few mammals today that is so exceptional in its appearance one might mistake it for a non-mammal. Linnaeus confused bats with birds, and contended with those who classified whales as fish; but pangolins were confused with reptiles because of their bearing large, overlapping scales. Amongst mammals, pangolins have one of the longest tails to body length, and it too is covered in these diamond-shaped scales.

Click image for a link to download as a wallpaper. Not mine.

Not all agree that all living pangolins belong in Manis. Some split the “subgenera” off as equal clades, for which the strongest evidence includes the giant pangolins in Smutsia (shown above) for temmincki and gigantea (both central to south Africa); Manis proper for pentadactylua, crassicaudata, and paleojavanica (southeast Asia, from Nepal to the Philippines); Paramanis (see below) for javanica and colionensis (southeast Asia); and the smaller and arboreal Phataganis for tricuspis (east and central Africa) and Uromanis for tetradactyla (central Africa).

It is easy to compare these to many extinct animals, conceive of them covered in their home-grown armor, and wonder at the evolutionary progress of this anatomy. Like aardvarks, armadillos, and many sloths — the last two pangolins were once thought to be closely related with — the limbs end in a few large claws, which rather than dig are used to tear into earthen substrate or trees, or get at the delicious goodness within. Pangolins are insectivorous, specializing in various ants and termites. They climb, using their claws as pitons to scale the trees that some dwell in. Those arboreal pangolins have much longer tails than their more terrestrial kin (as above).

Climbing pangolin from Borneo, Manis javanica. Note only the feet and tail are being used to grasp the tree; the hands are free. The pangolin is holding up “tri”pedally. From Wikimedia Commons and user Piekfrosch.

Pangolins have many unusual traits, not the least of which is the long prehensile tongue nearly as long as its body, anchored by muscles attached to its breastbone (sternum) and pelvis; but also a prehensile tail used to aid in climbing; the ability to, like armadillos, roll into balls for defense; and the rather fantastic ability to, unlike any other extant mammal aside from humans, to walk and run bipedally. That latter was well-documented in Life of Mammals.

Pangolins, much like anteaters and tamandua, lack teeth in their jaws. Given their similar diet, it seems no surprise. The pangolin skull seems a lot less specialized for this, though, in that it still retains many straits of its former morphology, features including a slight ascending process of the dentary and a more robust ramus. The tip of the jaw is downturned and forms a “spout,” as in many xenarthrans, but there are also a pair of side-facing “spurs” that project upwards and outwards, with very large foramina at their bases; the function of these “spurs” remains unknown. The bone of the mandible here is so thin that the normally internal passages for the mandibular branch of the trigeminal nerve (cnV3) simply pass right through the bone, leaving large openings in the side. But nonetheless, pangolins are convergent on their xenarthran relatives in both diet and some features of their jaw morphology. Recent genetic work has placed pangolins as the sister group to Carnivora (otters, civets, wolverines, bears, dogs, cats), known as Ferae. This nature belies its appearance.

Mandble of Manis tridactyla, a pangolin, in dorsal, lateral, medial, and ventral views. The mandibular symphysis is grey. Note the elongate "spurs" projecting from the front of the jaw.

Mandble of Manis (=Phataginus) tricuspis, a pangolin, in dorsal, lateral, medial, and ventral views. The mandibular symphysis is grey. Note the elongate “spurs” projecting from the front of the jaw.

Pangolins are endangered. They are sought for their meat, their skin, and their armor. Their organs and scales are said to cure ills. To raise awareness of their strangeness, their uniqueness, and their relationship to their habitat (and us), pangolins must be protected. World Pangolin Day is a new organization seeking to promote awareness of these mystifying, yet dying animals, and includes resources to help protect them when possible.

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2 Responses to The Scaled Mammal

  1. The spurs seem like muscle attachment sites, which would be convenient for an animal that needs to form a tigh tube with the lips. But I guess no muscle systems have been identified with them?

    • You are correct, there are no muscles attached to this region of the face. Not anything requiring such large knobby processes. It’s possible circumoral muscles could, but pangolins don’t have such need of them. The only thinks that pangolins consume are tiny insects, and these are destroyed in the stomach using stones. So there’s not even much oral processing going on. They may allow mechanical leverage, permitting the face to push through heavy substrates, but that’d have to be tested.

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