The Parasite that Killed a T-Rex

There are few dinosaurs quite as iconic as Tyrannosaurus Rex. At 12 metres long and up to 6 metres tall it was a ferocious apex predator, using its estimated 57,000N bite force to easily kill and eat the large herbivores of the day. Now you might expect that such a feared predator is going to appear on a blog about palaeopathology either because its tooth marks have been found in some poor unfortunate dinosaur, or because it was involved in the same kind of in-fighting which seems to have been endemic in some other predatory dinosaurs. You would however be wrong.

Sue_TRex_Skull_Full_Frontal
Sue the T-Rex. Source: Wikimedia Commons

“Sue” the T-Rex is one of the most complete specimens of her kind to ever be discovered. She was found in South Dakota during the summer of 1990 and although it is impossible to determine her real gender she was nicknamed after the palaeontologist who discovered her, Sue Hendrickson. Properly the specimen is known as FMNH PR2081 but for obvious reasons ‘Sue’ stuck. From a pathological point of view Sue is very interesting as the skeleton showed evidence of numerous healed injuries, including broken ribs and even arthritis. Analysis suggested that when she died Sue had reached 28 years old, quite a ripe age for a large predatory dinosaur. One of the most interesting injuries though is a series of lesions on the T-Rex’s skull, mostly along the lower jaw, and it’s a feature found in other specimens too.  For years palaeontologists have argued about what caused these lesions which theories ranging from bite marks to bone infections but then in 2009 a new theory emerged.

The new study focused not just on Sue but on a total of 10 individual skeletons all with the same lesions. The aim was to properly examine, measure and identify the lesions by comparing them to similar marks found in other archosaurs (this is a large group which includes dinosaurs, crocodiles, some other ancient reptiles, and birds). What they found was that the closest match for Sue’s lesions was actually to those produced by a modern parasitic infection found in birds. The disease is called trichomonosis, sometimes called ‘canker’ or ‘frounce’ depending on the species it is infecting at the time, and it is caused by a tiny parasite called Trichomonas gallinae. It can be a very serious disease and it has been suggested as the culprit in a recent, massive population decline amongst British green finches. Trichomonosis mainly damages the jaw and throat, producing lesions which can block the throat which cause problems swallowing and breathing. Death can eventually come from starvation, or occasionally actual asphyxiation. In Sue and her fellow T-Rex specimens the lesions were large and pronounced suggesting the infection was well advanced. The authors of the study even went as far as to suggest that in Sue’s case the infection was probably fatal.

References: Wolff, E.D.S., et al. 2009. Common Avian Infection Plagued the Tyrant Dinosaurs. Plos One. DOI: 10.1371/journal.pone.0007288

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