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. 2018 Oct 24;13(10):e0204951.
doi: 10.1371/journal.pone.0204951. eCollection 2018.

Pathological Survey on Temnodontosaurus From the Early Jurassic of Southern Germany

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Free PMC article

Pathological Survey on Temnodontosaurus From the Early Jurassic of Southern Germany

Judith M Pardo-Pérez et al. PLoS One. .
Free PMC article

Abstract

Paleopathologies document skeletal damage in extinct organisms and can be used to infer the causes of injury, as well as aspects of related biology, ecology and behavior. To date, few studies have been undertaken on Jurassic marine reptiles, while ichthyosaur pathologies in particular have never been systematically evaluated. Here we survey 41 specimens of the apex predator ichthyosaur Temnodontosaurus from the Early Jurassic of southern Germany in order to document the range and absolute frequency of pathologies observed in this taxon as a function of the number of specimens examined. According to our analysis, most observed pathologies in Temnodontosaurus are force-induced traumas with signs of healing, possibly inflicted during aggressive interactions with conspecifics. When the material is preserved, broken ribs are correlated in most of the cases with traumas elsewhere in the skeleton such as cranial injuries. The range of cranial pathologies in Temnodontosaurus is similar to those reported for extinct cetaceans and mosasaurs, which were interpreted as traces of aggressive encounters. Nevertheless, Temnodontosaurus differs from these other marine amniotes in the absence of pathologies in the vertebral column, consistent with the pattern previously documented in ichthyosaurs. We did not detect any instances of avascular necrosis in Temnodontosaurus from southern Germany, which may reflect a shallow diving life style. This study is intended to provide baseline data for the various types of observed pathologies in large ichthyosaurs occupying the 'apex predator' niche, and potentially clarifies aspects of species-specific behavior relative to other ichthyosaurs and marine amniotes.

Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. Examples of pathological vs non-pathological bone modifications in Temnodontosaurus.
Fig 2
Fig 2. Healing process of bone.
Modified from Cummings (2004). 1. Hematoma formation. 2. Fibrocartilaginous callus formation. 3. Bony callus formation. 4. Bone remodeling.
Fig 3
Fig 3. Temnodontosaurus sp., Jurensismergel Formation (upper Toarcian).
Urwelt-Museum Oberfranken, Bayreuth, Germany; Rabold and Eggmaier (2013) specimen no. 14. a. Overview of the skull exposed in ventral view, indicating the pathological areas in b, c, d and e. b. Posteriormost end of the right angular and surangular showing deformed, rugose tissue on the surangular and a deep pit in the angular. c. Long groove on the right ventrolateral margin of the right surangular. The margins are made of a crest of reactive bone. d. The same reactive bone crest in left ventrolateral view. e. Small protuberance of reactive bone on the ventral surface of the right splenial. f. Complete preserved skeleton in ventral view indicating the pathological portion of the right pectoral girdle. g. A broken fragment of premaxilla indicating the three areas with fibre remodeling with the white arrows. h. The pathological right coracoid, scapula, and humerus in ventral view, showing the pitting and the dorsoventral thickening compared with the elements of the left pectoral girdle. i-j. Two broken anterior dorsal ribs showing a rugose concavity at the distal end, which represents the proximal callus of a pseudarthrosis. Abbreviations: an, angular; d, dentary; hy, hyoid; ms, mandibular symphysis; pb, parabasisphenoid; pt, pterygoid; slp, sclerotic plates; sp, splenial; st p, stapes; su, surangular; v, vomer.
Fig 4
Fig 4. Temnodontosaurus nuertingensis (SMNS 13488).
Numismalismergel Formation (lower Pliensbachian). a. Skull in dorsal view indicating the pathologies in the premaxilla in b, c and d. b. Right premaxilla showing two areas of fibre remodeling (inset: magnified view). c. Lateral surface of the right premaxilla indicating five small areas of fibre remodeling. d. Dorsal view of the right and left premaxillae, indicating areas with fibre remodeling. e. Skull in left lateral view indicating pathological areas on the left premaxilla (f) and left dentary (g). f. Three small areas with fibre remodeling on the left premaxilla. g. Fibre remodeling on the ventrolateral margin of the left premaxilla and the lateral surface of the left dentary. h. Skull in ventral view, showing the location of the pathologies illustrated in i-n. i. A posteroventral to anterodorsally oriented concavity in the right angular. The arrows indicate slight fibre remodeling at the ends. j. A rugose protuberance with fibre remodeling on the right splenial. k. Pathological area between the left angular and surangular demarcated by dotted lines. l. A small area with callus development on the left angular. m. Three small protuberances with fibre remodeling on the lateral margin of the left angular. n. A teardrop concavity between the left angular and left surangular with fibre remodeling at its dorsal and ventral corners.
Fig 5
Fig 5. Temnodontosaurus trigonodon (SMNS 15950).
Posidonienschiefer Formation (lower–middle Toarcian). a. Complete skeleton prepared in left lateral view indicating the pathological areas in the skull (b) and ribs (g). b. Skull, indicating the detected pathologies of the left premaxilla, maxilla and dentary in c, d, e and f. c. Detail of the fibre remodeling observed in the premaxilla indicated in the black circles. d, e. Arrows indicating remodeled areas on the lateral surface of the premaxilla. f. Left dentary indicating two areas with fibre remodeling on the anteroventral edge. g. left lateral view of the left and right (h) dorsal ribs indicating the broken and healed ribs with the black circles. h. Detail of the broken and healed right dorsal ribs.
Fig 6
Fig 6. Temnodontosaurus trigonodon (GPIT/RE/9395).
Posidonienschiefer Formation, ?lower Toarcian. a. Skull exposed in left lateral view showing pathologies on the premaxilla, nasal and dentary in b-g. b. Rugose area with fibre remodeling on the lateral surface of the premaxilla. c. Fibre remodeling on the ventrolateral margin of the premaxilla indicated with white arrows. d. Rugose-textured remodeled area on the posterodorsal surface of the premaxilla. e. Tissue remodeling on the dorsal surface of the nasal. f-g. Fibre remodeling on the lateral surface of the left dentary: f. at the level of the symphysis; g. at the dorsolateral margin.
Fig 7
Fig 7. Temnodontosaurus sp. (UMH).
Posidonienschiefer Formation, middle Toarcian. a. Skull in right lateral view indicating the pathological areas of the lower jaw illustrated in b-e. b. Concavities observed at the ventrolateral margin of the dentary and surangular. c. Bony overgrowth at the anterior end of the right angular. d. Tissue remodeling observed at the dorsal margin of the angular. e. Fibre remodeling on the lateral surface of the dentary, dorsal to the concavity.
Fig 8
Fig 8. Temnodontosaurus trigonodon. (GPIT/RE/1491/13).
Posidonienschiefer Formation, lower Toarcian. a. Complete skeleton in dorsal (skull) and ventral view (postcranium). b. Left forefin indicating the pathological elements in the black circle. c. Arrow indicating the complete occlusion of the anterior notch of the radiale. Partial occlusion is also observed in the anterior notch of the radius, distal carpal two and metarcarpal two. Abbreviations: R: radius. ra: radiale. dc2: distal carpal two. mc2: metacarpal two.
Fig 9
Fig 9. Temnodontosaurus trigonodon, Jurensismergel Formation, upper Toarcian.
Rabold & Eggmaier (2013) U-MO specimen no. 4. a. Right lateral view of the skull; b. Anteriormost part of the premaxilla and dentary indicating the pathological areas in the right lateral premaxilla and dentary in c, d, e and f. c-e. Irregular tissue overgrowth at the ventral margin of the premaxilla. f. Tissue overgrowth with fibre remodeling at the dorsal margin of the dentary.
Fig 10
Fig 10. Temnodontosaurus sp. (UMH 454) Posidonienschiefer Formation.
a. Skull exposed in left lateral view indicating the pathological areas in b and c. d. Right lateral view of the premaxilla indicating the pathological areas in e and f. b-c. Two areas with fibre remodeling at the dorsal margin of the left premaxilla. e-f. Two areas with fibre remodeling at the right lateral surface of the premaxilla.
Fig 11
Fig 11. Graphic showing the relative frequency of pathologies by anatomical unit (a) and frequency of the types of pathologies observed in Temnodontosaurus (b).

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Grant support

This research was funded by the Deutsche Forschungsgemeinschaft (MA 4693/4-1 DFG). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
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