Common Avian Infection Plagued the Tyrant Dinosaurs

Abstract

Background Tyrannosaurus rex and other tyrannosaurid fossils often display multiple, smooth-edged full-thickness erosive lesions on the mandible, either unilaterally or bilaterally. The cause of these lesions in the Tyrannosaurus rex specimen FMNH PR2081 (known informally by the name ‘Sue’) has previously been attributed to actinomycosis, a bacterial bone infection, or bite wounds from other tyrannosaurids.Methodology/Principal FindingsWe conducted an extensive survey of tyrannosaurid specimens and identified ten individuals with full-thickness erosive lesions. These lesions were described, measured and photographed for comparison with one another. We also conducted an extensive survey of related archosaurs for similar lesions. We show here that these lesions are consistent with those caused by an avian parasitic infection called trichomonosis, which causes similar abnormalities on the mandible of modern birds, in particular raptors.Conclusions/SignificanceThis finding represents the first evidence for the ancient evolutionary origin of an avian transmissible disease in non-avian theropod dinosaurs. It also provides a valuable insight into the palaeobiology of these now extinct animals. Based on the frequency with which these lesions occur, we hypothesize that tyrannosaurids were commonly infected by a Trichomonas gallinae-like protozoan. For tyrannosaurid populations, the only non-avian dinosaur group that show trichomonosis-type lesions, it is likely that the disease became endemic and spread as a result of antagonistic intraspecific behavior, consumption of prey infected by a Trichomonas gallinae-like protozoan and possibly even cannibalism. The severity of trichomonosis-related lesions in specimens such as Tyrannosaurus rex FMNH PR2081 and Tyrannosaurus rex MOR 980, strongly suggests that these animals died as a direct result of this disease, mostly likely through starvation.

Studies on protozoa in ancient remains - A Review

“…The presence of Plasmodium dominicana in a Tertiary Dominican Republic amber specimen establishes a minimum age for the genus Plasmodium and places avian malaria in the Americas by the mid-Tertiary, supporting earlier theories that some species responsible for primate malaria could have evolved in the Americas (Poinar 2005b). Indirect evidence based on the frequency of erosive lesions found in tyrannosaurids suggests infection by a Trichomonas gallinae-like protozoan and represents the first report of an avian-transmissible disease in non-avian theropod dinosaurs (Wolff et al 2009). Cysts similar to those of the extant genus Entamoeba have been preserved in coprolites from the Early Cretaceous, enabling the description of two new genera and species, Entamoebites antiquus (Poinar & Boucot 2006) and Endamoebites proterus (Poinar 2009).…”

A new ascarid species in cynodont coprolite dated of 240 million years

“…Besides the possible presence of parasites, important information such as dietary habits, paleoclimate and paleoecological adaptations can be evidenced (Wolff et al 2009). The first study was conducted by Renault and Bertrand (1895), describing structures classified as bacteria on vertebrate coprolites dated from the Permian of France.…”

A history of Albertosaurus discoveries in Alberta, CanadaThis article is one of a series of papers published in this Special Issue on the theme Albertosaurus.

“…This appears to be a case of DISH (diffuse idiopathic skeletal hyperostosis), which is known in numerous dinosaur clades plus other extinct and extant vertebrates (Rothschild 1985;Rothschild and Berman 1991). Wolff et al (2009) in their study of tyrannosaurid mandibular lesions attributed an anomalous opening in the angular of TMP 1981.010.0001 to a trichomonosis-type infection.…”