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Common avian infection plagued the tyrant dinosaurs.

Wolff ED, Salisbury SW, Horner JR, Varricchio DJ - PLoS ONE (2009)

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin, Madison, Wisconsin, United States of America. ewolff@wisc.edu

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 findings: We 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/significance: This 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.

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Tyrannosaurid mandibular pathology(arrows indicate trichomonosis-type lesions; the position of each specimen is shown in red on the accompanying schematic interpretation of the reconstructed skull of Tyrannosaurus rex, FMNH PR2081); (A), Tyrannosaurus rex (holotype; CMNH 9380) right caudal mandibular ramus in lateral view, displaying a large circumscribed erosive lesion on the caudal part of the dentary. (B) Daspletosaurus torosus (RTMP 2001.36.01) left caudal mandibular ramus in lateral view, displaying a single erosive lesion. (C), Daspletosaurus torosus (RTMP 2001.36.01) multiple erosive lesions are visible on the right surangular in medial view. (D), Albertosaurus sarcophagus (RTMP 1981.10.01), left caudal mandibular ramus in lateral view, showing a slit-shaped trichomonosis-type lesion in the middle of the angular, (enlarged area, inset). (E) Tyrannosaurus rex (MOR 1125), caudal part of left dentary in lateral view, showing a cylindrical-shaped lesion, with smooth edges and almost no surrounding bony alteration. (F), Daspletosaurus torosus (RTMP 94.143.1), surangular in ventral view, with one slit-shaped lesion and one intermediate lesion. The close-up shows the smooth edges and limited surrounding bony alteration characteristic of a trichomonosis-type lesion. (G), Tyrannosaurus rex (MOR 980), left surangular in lateral view, exhibiting multiple oval- to sub-oval-shaped lesions.
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pone-0007288-g002: Tyrannosaurid mandibular pathology(arrows indicate trichomonosis-type lesions; the position of each specimen is shown in red on the accompanying schematic interpretation of the reconstructed skull of Tyrannosaurus rex, FMNH PR2081); (A), Tyrannosaurus rex (holotype; CMNH 9380) right caudal mandibular ramus in lateral view, displaying a large circumscribed erosive lesion on the caudal part of the dentary. (B) Daspletosaurus torosus (RTMP 2001.36.01) left caudal mandibular ramus in lateral view, displaying a single erosive lesion. (C), Daspletosaurus torosus (RTMP 2001.36.01) multiple erosive lesions are visible on the right surangular in medial view. (D), Albertosaurus sarcophagus (RTMP 1981.10.01), left caudal mandibular ramus in lateral view, showing a slit-shaped trichomonosis-type lesion in the middle of the angular, (enlarged area, inset). (E) Tyrannosaurus rex (MOR 1125), caudal part of left dentary in lateral view, showing a cylindrical-shaped lesion, with smooth edges and almost no surrounding bony alteration. (F), Daspletosaurus torosus (RTMP 94.143.1), surangular in ventral view, with one slit-shaped lesion and one intermediate lesion. The close-up shows the smooth edges and limited surrounding bony alteration characteristic of a trichomonosis-type lesion. (G), Tyrannosaurus rex (MOR 980), left surangular in lateral view, exhibiting multiple oval- to sub-oval-shaped lesions.

Mentions: Nearly 15% of the 61 tyrannosaurid individuals examined during this study exhibited trichomonosis-type lesions on the mandible (Figure 1, Figure 2, and Supporting Information S1). In seven out of nine cases, the trichomonosis-type lesions showed a unilateral distribution (Figure 2, A, D, E, F and G, and Supporting Information S1). In the remaining cases, they occurred on both sides of the mandible (Figure 1, Figure 2, B and C, and Supporting Information S1). These abnormalities comprise multiple chronic smooth-edged erosive lesions with a focal distribution in the caudal part of the mandible, usually on the surangular and less commonly on the dentary (Figure 1, Figure 2, and Supporting Information S1). The abnormalities typically have a circular or slit-like shape, with moderate surrounding thickening of the bone. In the majority of cases, these lesions exhibit neither alteration to the bone fabric, deformation of the periosteal bone nor exposure of the endosteal bone. Instead, the outward appearance often consists of a developmental change in the bone with no indication of any obvious mechanism of formation.


Common avian infection plagued the tyrant dinosaurs.

Wolff ED, Salisbury SW, Horner JR, Varricchio DJ - PLoS ONE (2009)

Tyrannosaurid mandibular pathology(arrows indicate trichomonosis-type lesions; the position of each specimen is shown in red on the accompanying schematic interpretation of the reconstructed skull of Tyrannosaurus rex, FMNH PR2081); (A), Tyrannosaurus rex (holotype; CMNH 9380) right caudal mandibular ramus in lateral view, displaying a large circumscribed erosive lesion on the caudal part of the dentary. (B) Daspletosaurus torosus (RTMP 2001.36.01) left caudal mandibular ramus in lateral view, displaying a single erosive lesion. (C), Daspletosaurus torosus (RTMP 2001.36.01) multiple erosive lesions are visible on the right surangular in medial view. (D), Albertosaurus sarcophagus (RTMP 1981.10.01), left caudal mandibular ramus in lateral view, showing a slit-shaped trichomonosis-type lesion in the middle of the angular, (enlarged area, inset). (E) Tyrannosaurus rex (MOR 1125), caudal part of left dentary in lateral view, showing a cylindrical-shaped lesion, with smooth edges and almost no surrounding bony alteration. (F), Daspletosaurus torosus (RTMP 94.143.1), surangular in ventral view, with one slit-shaped lesion and one intermediate lesion. The close-up shows the smooth edges and limited surrounding bony alteration characteristic of a trichomonosis-type lesion. (G), Tyrannosaurus rex (MOR 980), left surangular in lateral view, exhibiting multiple oval- to sub-oval-shaped lesions.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2748709&req=5

pone-0007288-g002: Tyrannosaurid mandibular pathology(arrows indicate trichomonosis-type lesions; the position of each specimen is shown in red on the accompanying schematic interpretation of the reconstructed skull of Tyrannosaurus rex, FMNH PR2081); (A), Tyrannosaurus rex (holotype; CMNH 9380) right caudal mandibular ramus in lateral view, displaying a large circumscribed erosive lesion on the caudal part of the dentary. (B) Daspletosaurus torosus (RTMP 2001.36.01) left caudal mandibular ramus in lateral view, displaying a single erosive lesion. (C), Daspletosaurus torosus (RTMP 2001.36.01) multiple erosive lesions are visible on the right surangular in medial view. (D), Albertosaurus sarcophagus (RTMP 1981.10.01), left caudal mandibular ramus in lateral view, showing a slit-shaped trichomonosis-type lesion in the middle of the angular, (enlarged area, inset). (E) Tyrannosaurus rex (MOR 1125), caudal part of left dentary in lateral view, showing a cylindrical-shaped lesion, with smooth edges and almost no surrounding bony alteration. (F), Daspletosaurus torosus (RTMP 94.143.1), surangular in ventral view, with one slit-shaped lesion and one intermediate lesion. The close-up shows the smooth edges and limited surrounding bony alteration characteristic of a trichomonosis-type lesion. (G), Tyrannosaurus rex (MOR 980), left surangular in lateral view, exhibiting multiple oval- to sub-oval-shaped lesions.
Mentions: Nearly 15% of the 61 tyrannosaurid individuals examined during this study exhibited trichomonosis-type lesions on the mandible (Figure 1, Figure 2, and Supporting Information S1). In seven out of nine cases, the trichomonosis-type lesions showed a unilateral distribution (Figure 2, A, D, E, F and G, and Supporting Information S1). In the remaining cases, they occurred on both sides of the mandible (Figure 1, Figure 2, B and C, and Supporting Information S1). These abnormalities comprise multiple chronic smooth-edged erosive lesions with a focal distribution in the caudal part of the mandible, usually on the surangular and less commonly on the dentary (Figure 1, Figure 2, and Supporting Information S1). The abnormalities typically have a circular or slit-like shape, with moderate surrounding thickening of the bone. In the majority of cases, these lesions exhibit neither alteration to the bone fabric, deformation of the periosteal bone nor exposure of the endosteal bone. Instead, the outward appearance often consists of a developmental change in the bone with no indication of any obvious mechanism of formation.

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin, Madison, Wisconsin, United States of America. ewolff@wisc.edu

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 findings: We 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/significance: This 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.

Show MeSH
Related in: MedlinePlus