Literaturdatenbank
Literaturdatenbank |
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Benson, R. B. J., Domokos, G., Várkonyi, P. L., & Reisz, R. R. (2011). Shell geometry and habitat determination in extinct and extant turtles (reptilia: Testudinata). Paleobiology, 37(4), 547–562.
Added by: Admin (06 Jan 2014 18:24:03 UTC) |
| Resource type: Journal Article DOI: http://dx.doi.org/10.1666/10052.1 BibTeX citation key: Benson2011 View all bibliographic details  |
Categories: General Keywords: Chersina angulata, Morphologie - morphology, Schildkröten - turtles + tortoises, Testudinidae, Testudo graeca, Testudo hermanni, Testudo horsfieldii, Testudo marginata Creators: Benson, Domokos, Reisz, Várkonyi Collection: Paleobiology |
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| Abstract |
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variety of means, including forelimb proportions and shell bone histology have been used to infer the paleoecology of extinct turtles. However, the height-to-width ratio of the shell (as a one-parameter shell model) has been dismissed because of its unreliability, and more complex aspects of shell geometry have generally been overlooked. Here we use a more reliable, three-parameter geometric model of the shell outline in anterior view as a means to assess turtle paleoecology. The accuracy of predictions of extant turtle ecology based on our three-parameter shell model is comparable to that derived from forelimb proportions when distinguishing between three ecological classes (terrestrial, semiaquatic, and aquatic). Higher accuracy is obtained when distinguishing between two classes (terrestrial and non-terrestrial), because the contours of aquatic and semiaquatic turtles are often very similar. Our model classifies Proterochersis robusta, a stem turtle from the Late Triassic of Germany, as non-terrestrial, and likely semiaquatic. Our method, combined with inferences based on limb proportions, indicates a diverse range of ecotypes represented by Late Triassic stem turtles. This implies that the ecological diversification of stem-group turtles may have been rapid, or that a substantial period of currently cryptic diversification preceded the first fossil appearance of the turtle stem lineage during the Late Triassic. Testudinidae For instance, in Testudo horsfieldii males engage in combat in competition for mates. This often results in overturning. Although females may have taller shells for a given body length, males have a highly domed carapace, whereas females had a taller plastron. Experiments show that male T. horsfieldii almost always succeeded in self-righting, whereas females succeeded less than half the time (Bonnett et al. 2001). A similar pattern of shape dimorphism is evident in Chersina angulata (Mann et al. 2006), Testudo graeca, and Testudo hermanni, but not Testudo marginata (Willemsen and Hailey 2003). All dimorphic taxa studied by Willemsen and Hailey (2003) were more strongly dimorphic than T. horsfieldii, suggesting that the specialized burrowing lifestyle of T. horsfieldii also imposes constraints on body shape.
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