The anecdotal Tarbosaurus throat skin

An illustration of Tarbosaurus with a hypothetical throat pouch, from Carpenter (1999).

A persistent rumor in the online paleontological community is that the tyrannosaurid Tarbosaurus bataar had a throat pouch or dewlap. This is allegedly based on an undescribed skull with associated skin impressions. If true, it would have interesting implications for the paleobiology of this species. It would be even more important considering that tyrannosaur integument has become a hotly debated issue in recent years. Although commonly represented in paleoart, a source for this information is almost never cited by the artist. So where did the account of Tarbosaurus throat skin originate?

Unfortunately it is only from a personal communication briefly mentioned in two books over 20 years ago. The communication, from Russian paleontologist Konstantin Mikhailov to Ken Carpenter, was first published in Encyclopedia of Dinosaurs (Carpenter, 1997).

“Impressions of skin around a badly weathered skull of Tyrannosaurus (= Tarbosaurus) bataar in Mongolia showed the presence of a wattle or bag of skin under the jaws (Mikhailov, personal communication). Perhaps this bag of skin enabled large chunks of prey to be swallowed. It is also possible that the skin was a brightly colored dewlap similar to that seen in some lizards today.”

It was published again in Eggs, Nests, and Baby Dinosaurs, this time with an accompanying life restoration (Carpenter, 1999).

“Tyrannosaurus and related large carnivores lack any display structure of bone on the head or body. Tyrannosaurus did, however, apparently have either a pelican-like pouch or dewlap based on an impression of the skin found below a skull in Mongolia (Mikhailov, personal communication). This, like other remarkable traces of dinosaur skin, shows that dinosaurs had display structures that rarely fossilized. If the impression is a dewlap, then Tyrannosaurus might have courted by displaying his dewlap. If the impression was a pelican-like pouch, then possibly a brightly-colored pouch was inflated and displayed with the head tilted back somewhat like a frigate bird (Fig. 4.13).”

This is all of the information available about the Tarbosaurus throat skin. No photographs or illustrations of the actual impressions have ever surfaced. Mikhailov’s description is missing a lot of critical details. The locality where the specimen came from is unknown, as are its present whereabouts. Was it collected and placed in a museum, or was it left in the field to erode completely? There are no measurements for the impressions and the exact type of integument (e.g. naked skin or scales) is not stated. The specimen could have been misinterpreted, with the “pouch” actually representing post-mortem skin slippage. Given the lack of further study it is best to remain cautious.

A chart of the published skin impressions from Tarbosaurus.

There are two published specimens of preserved integument from Tarbosaurus, both in the collections of the Mongolian Paleontological Center (see chart above). Multiple patches of skin from the toe and sole pads of a footprint (MPC-D 100F/12 – Currie et al. 2003) and two small patches from the thoracic area (MPC-D 107/6A – Currie et al. 2003; Bell et al. 2017) are known. These impressions show small, pebbly scales with an average diameter of 2 mm. It is possible that MPC-D 107/6A was the specimen described by Mikhailov, considering it was recovered near a damaged skull and could have been mistaken for coming from the throat. However, this is impossible to confirm without locality data.

The Tarbosaurus throat skin is another example of an internet rumor that should be subjected to more scrutiny. It is misleading to claim that there is hard evidence for a pouch or dewlap when it is entirely anecdotal. Taphonomic distortion or incorrect recollection are factors to be considered here. That being said, it is still acceptable to include in paleoart as a speculative feature, in the absence of contradictory evidence.

References

• Bell, P.R., Campione, N.E., Persons, W.S., IV, Currie, P.J., Larson, P.L., Tanke, D.H., & Bakker, R.T. (2017). Supplementary material from “Tyrannosauroid integument reveals conflicting patterns of gigantism and feather evolution” (version 2). The Royal Society. https://doi.org/10.6084/m9.figshare.c.3787391.v2
• Carpenter, K. (1997). Tyrannosauridae. In P.J. Currie & K. Padian (Eds.), Encyclopedia of Dinosaurs (pp. 766-768). Academic Press.
• Carpenter, K. (1999). Eggs, Nests, and Baby Dinosaurs: A Look at Dinosaur Reproduction. Indiana University Press.
• Currie, P.J., Badamgarav, D., & Koppelhus, E.B. (2003). The first Late Cretaceous footprints from the Nemegt locality in the Gobi of Mongolia. Ichnos, 10(1), 1-13.

Addendum (10/9/2019)

Some new information is available thanks to Mickey Mortimer (see comment below). A personal communication with Mikhailov has revealed that the throat skin specimen was not collected. It has also shown that the pouch/dewlap identification was proposed by Sergei Kurzanov, who was the original discoverer. Unfortunately the loss of this specimen means that no analyses can be done to determine the true nature of the integument.

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