Pinacosaurus: Long Tongued, Armoured Beast Of The Cretaceous

A Pinacosaurus showing off its impressive, purple tongue. To see my reasoning behind this, read on . . .

By Kabacchi - Pinacosaurus - 01Uploaded by FunkMonk, CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=9933724

Pinacosaurus was an ankylosaurid which lived in Mongolia during the late Cretaceous, around 75-80 million years ago. I've got to admit, I've got a softspot for ankylosaurids, as I can really visualize them as these low-slung, cantankerous, armoured creatures bulldozing their way through the undergrowth - in fact, hold that thought, I'll be looking more into this and ankylosaurid ecology in a future post.

Anyway, onto today's subject - a particular ankylosaurid, Pinacosaurus. These creatures lived in an arid, semi-desert region, interspaced with the occaisonal oasis. Now, deserts aren't exactly renowned for their large amount of plant life, so what was Pinacosaurus finding to eat out there to eat in the arid, sandy plains?

This isn't to say that there aren't plants in deserts, and that large herbivores can't survive there. Take dromedary camels, for example - they manage to find enough vegetation to feed upon even in their arid habitat. According to one study, a typical diet is 47.5% dwarf shrubs, 29.9% trees, 11.2% grasses, 11% vines, and 0.2% other herbs. Can we, in fact, learn anything about Pinacosaurus diet from dromedaries? I think that we can:
A large portion of the plants that these camels are eating - many of the shrubs and trees shown in the statistics above - are spiny. Examples include Vachellia tortilis and Balanites aegyptiaca, both of which protect their leaves with vicious spines.

The spines of Vachellia tortilis

 By JMK - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=24858716

Spiny vegetation is something of a recurring theme in deserts, actually. Cacti are the most well-known, and are a very succesful group of plants. In arid regions, leaves are often relatively moisture-filled, and make for good food for animals. Therefore, the plants have to protect what little they have - with spiky defences.

Now, let's put two and two together: Pinacosaurus, the desert dwelling ankylosaurid, likely ate a lot of spiny plants, which are predominant in desert ecosystems. If so, then we would expect to see some kind of adaptations towards feeding on thorny plants . . .

And that's where this fascinating article comes in: http://phenomena.nationalgeographic.com/2015/07/27/ankylosaurs-slurped-food-with-powerful-tongues/

In short, preserved paraglossalia have been found in a Pinacosaurus fossil. Paraglossalia are part of the hydrobranchial apparatus, attachment points for tongue muscles.

From Hill et al., 2015

It's unusual for paraglossalia to fossilize because they're so delicate and often decay rather than fossilize. However, Pinacosaurus has provided us with the opportunity to have an amazing insight into its life appearance and diet thanks to its preserved throat bones.

The paraglossalia in this specimen are unusually large and robust, as can be quite clearly seen in the image above. As these are muscle attachment points, this strongly suggests that Pinacosaurus had a muscular, powerful tongue.

Well, this is really interesting to me. There's not much point in having powerful tongue unless it can extend out of your mouth, so it in turn suggests that as well as it being muscular, its tongue was also quite long. The presence of such an organ may actually have been the vital adaptation that allowed Pinacosaurus to conquer its envioroment and get at its food.

So, there's 2 theories here, I'll present both of them and then come to a conclusion at the end of the post.

Theory #1: Giraffe Theory

Now let's go back to the stuff I was going on about at the beginning of the post, about spiny plants. Pinacosaurus, living in its arid envioroment, would likely find a lot of vegetation to be thorny. A modern-day adaptation to help combat this is found in the giraffe. Its long, prehensile, purple tongue is used for grasping prickly vegetation and pulling up leaves while avoiding the larger spikes. Given the habitat of Pinacosaurus, it seems quite plausible that it might have used its tongue for feeding upon spiny plants.

Also of note is the dark purple-black colouration of giraffe tongues - probably to protect it from sunburn. Other animals that often keep their tongue out of their mouth, such as anteaters, also have similarly-coloured tongues - it's probable that whichever theory is true, this one or the one below, the tongue of Pinacosaurus would be similar.

Theory #2: Anteater Theory

Even before the article I linked to earlier in this post was published, Duane Nash, a paleontology enthusiast who I hugely admire for his brilliant theories, was already suggesting the presence of a large tongue in Tarchia, due to the unusual notch in its upper jaw, which resembles that of a sloth bear, and he suggested that as with the bear, it allowed a long tongue to protrude from the mouth. See his post here.

However, his conclusion was different from the giraffe theory I suggested above. Instead, his conclusion was that Tarchia might have been an insectivore, rather like a well-armoured anteater. Of course, Tarchia isn't the species that I've been referring to in this post, I've been talking about Pinacosaurus, but both have a similar jaw notch, and I believe that both of them - and possibly other species of ankylosaurids - had similarly large tongues.

As another convincing element of Nash's argument is that like many ankylosaurids, Tarchia has quite weak dentition. This is something that I will probably touch upon in a future post. However, it is usually argued that where they lacked in good plant-munching teeth, they made up for in large, fermenting guts, and they may have used stones to help grind down vegetation.

 So could the insectivore argument extend from Tarchia, to Pinacosaurus as well? I don't see any reason why not. Could they have both been ant-slurping specialists, perhaps tempering their diet with plant matter?

Now, to come to a conclusion is difficult, but after some thought, I believe that both of the above theories are true to an extent. Pinacosaurus, I believe, was an omnivore with a long, prehensile tongue, equally adept at lapping up insects as it is at pulling at spiny vegetation.

Duane Nash uses the comparison between Tarchia and the sloth bear. But looking at the sloth bear, despite it feeding a lot on termites, it also eats plant matter (particularly fruit) and honey. So I actually think the sloth bear comparison is good - a specialized insect eater, but not so specialized.

To conclude, Pinacosaurus and Tarchia almost certainly had a long, prehensile tongue, perfect for both feeding upon invertebrates and grasping thorny plants.

Now, take a moment to imagine these things in their natural habitat - like miniature tanks, well armoured, trundling across the sand dunes, extending a long, purple tongue . . .

Now that's an image that I like.

By the author. Anatomic accuracy not guaranteed.