Ankylosaurs Slurped Food With Powerful Tongues

Over eight decades ago, while pondering the heavily-armored dinosaur Scolosaurus, the eccentric paleontologist Franz Nopcsa proposed what is probably one of the oddest ideas in the annals of paleobiological speculation. Scolosaurus was a low-slung quadruped that shuffled around what were then thought to be parched sand dunes. Even though its close ankylosaurian relatives had been interpreted as herbivores from the very start, the Cretaceous desert may have been nearly devoid of low-lying vegetation. But there was another source of food. Perhaps Scolosaurus was an insectivore, Nopcsa suggested, nabbing little arthropods as if the dinosaur were an overgrown horned toad.

Nopcsa’s proposal didn’t catch on. The little leaf-shaped teeth in ankylosaurian mouths accorded better with an herbivorous diet, and a rare find of ankylosaur gut contents confirmed that some of these dinosaurs ate seeds, fruit, leaves, and other low-growing plants. But new evidence has led paleontologist Robert Hill and colleagues to tentatively revive Nopcsa’s idea for a different armored dinosaur. The chief line of evidence is a bone that’s never been seen in a non-avian dinosaur until now.

Most dinosaurs go undiscovered. Of those we find, most are in pieces. Fewer still are represented by elements that came apart but remained in close proximity (or are in association). An even smaller number are articulated, preserving the moment of burial. But even then, even in seemingly the most complete and beautifully-articulated specimens, certain parts are often missing. Among them are delicate little throat bones that dinosaurian tongues attached to.

While carefully cleaning up a skull and series of neck vertebrae from the 80-75 million year old ankylosaur Pinacosaurus, preparators Virginia Heisey and Joe Groenke started to uncover thin, triangular bones in the dinosaur’s throat. These were the paraglossalia – elements that had only previously seen in birds.

In our living dinosaurs, paraglossalia are relatively small and flat. They make up the forward-most part of a set of elements called the hyobranchial apparatus. This set of rods, derived from the gill arches of the four-limbed fish that were also our ancestors, provides an attachment site for the tongue muscles at the front and embeds into the pharynx at the back.

There’s a variety of reasons why no one has recognized paraglossalia in non-avian dinosaurs until now. The most obvious is that these elements are usually made of cartilage and probably decay before fossilization. And even when these elements turn to bone, Hill and coauthors point out, they are very thin. The front part of the paraglossalia in Pinacosaurus are so thin that they’re translucent. Even then, these parts might remain embedded in rock that stabilizes the skull, confused for unimportant bone shards and prepared away, or simply set aside as unknown bones. In fact, paleontologists already had at least one example of paraglossalia in collections prior to this discovery. When Hill and colleagues had another look at the armored dinosaur Edmontonia, they found another instance of these elements.

The throat bones of Pinacosaurus. From Hill et al., 2015.
The throat bones of Pinacosaurus. From Hill et al., 2015.

Other dinosaurs resting in museum collections probably have paraglossalia, too. That’s because the presence of these elements in both birds and ankylosaurs – distant cousins in the dinosaur family tree – indicates that this apparatus went back to the last common ancestor of all dinosaurs, at the very least. Field workers, preparators, and paleontologists should keep a sharp eye out for these bones that may have otherwise been set aside as mystery pieces.

This is about more than simply adding more bones to the dinosaurian skeleton, though. In the case of Pinacosaurus, Hill and co-authors report that the paraglossalia are much larger and more robust than what’s seen in birds. This dinosaur must have had a powerful tongue. Rather than chomping at vegetation with its jaws, it may have plucked and scooped green food with a muscular tongue.

But here’s where Nopsca comes in. Pinacosaurus lived in a relatively arid environment of rolling sand dunes. Plants may have been rare, and insect fossils are commonly found in the same rocks. While it’s a speculative stretch, Hill and colleagues entertain the idea that Pinacosaurus could have slurped up social insects and millipedes as a large part of its diet. As anteater, pangolins, armadillos, and even salamanders show us today, a powerful tongue can be quite useful in snaffling ants and other invertebrates. Instead of being bumpy vegetarians, some ankylosaurs might have been highly-armored anteaters.

Reference:

Hill, R., D’Emic, M., Bever, G., Norell, M. 2015. A complex hyobranchial apparatus in a Cretaceous dinosaur and the antiquity of avian paraglossalia. Zoological Journal of the Linnean Society. doi: 10.1111/zoj.12293

8 thoughts on “Ankylosaurs Slurped Food With Powerful Tongues

  1. Yes a lot of ankylosaurs have a bit of notch on the upper beak that would facilitate a tongue that darted in and out. Although I’m not sure if a truly dedicated insect diet could sustain animals this large such a tongue could have pulled in insects, plants, aquatic vegetation, fruits, nuts, or eggs. In fact the low, compact and armored build of ankylosaurs would have made them excellent egg thiefs.

  2. I actually wonder if Pinacosaurus was more similar to a giraffe (hear me out). Giraffes have thick muscular tongues partly to help them deal with the thorns and spines of the acacia trees they feed on. In arid environments, spines are one of the ways plants deter herbivores. Couldn’t Pinacosaurus’ muscular tongue have helped it overcome similar plant armaments?

  3. Steve Hasiotis has been telling me for years that all armored dinosaurs were insectivores. Never liked it for such big animals.

  4. Omnivory would make sense in an arid environment where resources are low as it would allow these animals to exploit all available food sources. Additionally, plants in these ecosystems tend to be tough and thorny. Giraffes use their large tongues to navigate around the thorns of acacia trees. Perhaps ankylosaurs were doing something similar.

  5. Right Steve Hasiotis has been interpreting armored dinos that way for a while. I don’t think that it is either/or type of thing with ankylosaur diet. I’ve often described ankylosaurs as the mobile compost bins of the mesozoic taking up all manner of weird foodstuffs that the environment coughs up including eggs (fresh/rotten), fruits, nuts, fungi, aquatic plants, feces, dino gruel robbed from baby nestling dinos, detritus, rotten wood, insects, grubs, small animals, carrion, toxic/poisonous stuff. Kind of a combination pig, armadillo, and sloth bear. Of course there was probably a spectrum of dietary predilections. For reference ursidae – the bears – display a remarkable diversity of dietary specialization from orchids (spectacled bear) to seals (polar bear) all within a fairly conservative bauplan. I also think ankylosaurs were excellent nest raiders and would have been persistent kleptoparasites of large dino nesting colonies feeding on eggs, dung, and crop milk/regurtitated food. Again though there was likely a spectrum i.e. Talarurus was doing something different than Euoplocephalus.

  6. Fascinating; the importance of the tongue reminds me of tortoises.

    The nomenclature of the hyobranchials is wrong, though; it’s shifted dorsolaterally by one element, as is largely traditional in salamanders. The “ceratobranchials” are hypobranchials, and the “epibranchial” is ceratobranchial 1; epibranchials have not been seen in limbed vertebrates since Acanthostega (and in rudimentary form in one extant salamander individual).

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