using the force: forelimb robustness of thylacosmilus atrox and other saber-toothed carnivores
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Using the Force: Forelimb robustness of Thylacosmilus atrox and other saber-toothed carnivores. Laurel Perper and John Orcutt. Cornell College laurelsperper @ gmail.com. What is Thylacosmilus ?. Extinct saber-toothed marsupial from South America “Pouch saber” - PowerPoint PPT PresentationTRANSCRIPT
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Using the Force: Forelimb robustness of
Thylacosmilus atrox and other saber-toothed
carnivoresLaurel Perper and John Orcutt
Cornell [email protected]
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What is Thylacosmilus?• Extinct saber-toothed
marsupial from South America
• “Pouch saber”• Late Miocene to Late
Pliocene• “Cat-like,” but not a felid• Peculiar morphology
Cast of Thylacosmilus skull at the American Museum of Natural History (type specimen at the Field Museum of Natural History)
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Types of SabersDirk Scimitar Conical
Homotherium skullSmilodon skull Clouded leopard skull
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Prey-Killing Strategies of Feliforms
• Meachen-Samuels and Van Valkenburgh (2009)• Extant feliforms• Ambush vs. pursuit predators• Prey size
• Meachen-Samuels (2012)• “Functional link between canine shape and
forelimb morphology”• Modern and extinct feliforms• Bivariate analysis of canine indices vs. forelimb
measurements
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Questions• Since it is a marsupial, why is Thylacosmilus so cat-
like?• What could have caused such peculiar morphology?• Why is it the only known saber-tooth member of the
marsupials?
• How did it hunt and kill its prey?• Hypothesis: Thylacosmilus was an ambush predator
• How does it compare with other saber-toothed predators?
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Methods• Forelimb
measurements define whether animal is ambush predator or pursuit predator
• Measurements of paratype/holotype at FMNH
• Bivariate analysis of canine index vs forelimb measurements of cats (Meachen-Samuels, et al)
Humerus of Thylacosmilus atrox
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PAW
0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.40
2
4
6
8
10
12
Barbourofelis loveo-rum
Thylacosmilus atrox
Smilodon gracilis
Hoplophoneus primae-vus
Smilodon fatalis
Cani
ne In
dex
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HEI
0.16 0.18 0.2 0.22 0.24 0.26 0.28 0.3 0.32 0.340
2
4
6
8
10
12
Thylacosmilus atrox
Barbourofelis loveorum
Smilodon fatalis
Smilodon gracilis
Cani
ne In
dex
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HRI
0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.20
2
4
6
8
10
12
Smilodon fatalis
Barbourofelis loveorum
Thylacosmilus atrox
Smilodon gracilis
Cani
ne In
dex
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Artist Carl Buell’s interpretation of side-by-side comparison of Smilodon and Thylacosmilus
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Results
• Plots closely with Smilodon and Barbourofelis
• Likely an ambush predator• Robust arms for anchoring prey, preventing
struggle• Long, flattened dirk teeth to deliver swift blow
to critical veins• Larger prey
Illustration of Thylacosmilus by Mauricio Antón
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Further Research• Why is Thylacosmilus so cat-like?• What could have driven the evolution of such a
peculiar morphology?• Environment• Open woodlands/grasslands
• Prey selection• Larger prey such as toxodonts, rodents, other ungulates
• Phylogenetic constraints• Evolution from earlier form
• Competition with other predators
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Acknowledgments
Julie Meachen with Des Moines Universityand
Susumu Tomiya and Bill Simpson with the Field Museum of Natural History
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Bibliography• Argot, Christine. Functional-adaptive features and palaeobiologic
implications of the postcranial skeleton of the late Miocene sabretooth borhyaenoid Thylacosmilus atrox (Metatheria). Alcheringa: An Australian Journal of Palaeontology. 29, 2 (2009): 229-266.
• Meachen-Samuels, Julie, et al. Forelimb indicators of prey-size preference in the Felidae. Journal of Morphology. 270 (2009): 729-274.
• Meachen-Samuels, Julie. Morphological convergence of the prey-killing arsenal of saber-tooth predators. Paleobiology. 38, 1 (2012): 1-14.