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Sabretoothed carnivores and the killing of large prey.

Andersson K, Norman D, Werdelin L - PLoS ONE (2011)

Bottom Line: For sabretooths, this size-reversed functional advantage suggests predation on species within a similar size range to those attacked by present-day carnivorans, rather than "megaherbivores" as previously believed.The development of the sabretooth condition appears to represent a shift in function and killing behaviour, rather than one in predator-prey relations.We anticipate this new insight to be a starting point for detailed study of the evolution of pathways that encompass extreme specialisation, for example, understanding how neck-powered biting shifts into shear-biting and its significance for predator-prey interactions.

View Article: PubMed Central - PubMed

Affiliation: Department of Earth Sciences, University of Cambridge, Cambridge, United Kingdom. andersson.ki@gmail.com

ABSTRACT
Sabre-like canines clearly have the potential to inflict grievous wounds leading to massive blood loss and rapid death. Hypotheses concerning sabretooth killing modes include attack to soft parts such as the belly or throat, where biting deep is essential to generate strikes reaching major blood vessels. Sabretoothed carnivorans are widely interpreted as hunters of larger and more powerful prey than that of their present-day nonsabretoothed relatives. However, the precise functional advantage of the sabretooth bite, particularly in relation to prey size, is unknown. Here, we present a new point-to-point bite model and show that, for sabretooths, depth of the killing bite decreases dramatically with increasing prey size. The extended gape of sabretooths only results in considerable increase in bite depth when biting into prey with a radius of less than ∼10 cm. For sabretooths, this size-reversed functional advantage suggests predation on species within a similar size range to those attacked by present-day carnivorans, rather than "megaherbivores" as previously believed. The development of the sabretooth condition appears to represent a shift in function and killing behaviour, rather than one in predator-prey relations. Furthermore, our results demonstrate how sabretoothed carnivorans are likely to have evolved along a functionally continuous trajectory: beginning as an extension of a jaw-powered killing bite, as adopted by present-day pantherine cats, followed by neck-powered biting and thereafter shifting to neck-powered shear-biting. We anticipate this new insight to be a starting point for detailed study of the evolution of pathways that encompass extreme specialisation, for example, understanding how neck-powered biting shifts into shear-biting and its significance for predator-prey interactions. We also expect that our model for point-to-point biting and bite depth estimations will yield new insights into the behaviours of a broad range of extinct predators including therocephalians (gorgonopsian + cynodont, sabretoothed mammal-like reptiles), sauropterygians (marine reptiles) and theropod dinosaurs.

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Canine size follows gape for carnivorans with canine killing bite habits.Measured gape plotted against gape predicted from canine size, for fossil sabretooths (white symbols and dash-dot regression line), present day non-sabretoothed carnivorans (Felidae, light gray symbols and dashed regression line; all other carnivoran families, dark grey symbols and dotted regression line). The solid line marks isometry (y = x) between measured and predicted gape and bubble diameters represent Rshift values (not to scale). Gape is measured as the angle formed between the craniomandibular-joint and the tips of the incisors. Gape is predicted assuming canine clearance equal to the combined height of the upper and lower canine and calculated as the sum thereof.
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pone-0024971-g002: Canine size follows gape for carnivorans with canine killing bite habits.Measured gape plotted against gape predicted from canine size, for fossil sabretooths (white symbols and dash-dot regression line), present day non-sabretoothed carnivorans (Felidae, light gray symbols and dashed regression line; all other carnivoran families, dark grey symbols and dotted regression line). The solid line marks isometry (y = x) between measured and predicted gape and bubble diameters represent Rshift values (not to scale). Gape is measured as the angle formed between the craniomandibular-joint and the tips of the incisors. Gape is predicted assuming canine clearance equal to the combined height of the upper and lower canine and calculated as the sum thereof.

Mentions: To test canine clearance and its assumptions for point-to-point biting we compared measured actual gape angle at maximum jaw extension to gape angles predicted for an optimal canine-height and gape configuration for a range of extant and extinct carnivorans (Fig. 2). Gape angles were predicted by assuming a one to one relationship between the combined crown height of the upper and lower canines and the distance or “clearance” between the tips at maximum jaw extension. For canids, which typically kill large prey with multiple bites [21], measured- and predicted gape were loosely correlated (Linear Regression (LR); y0 = 16.838, a = 1.141, R2 = 0.701, SEE = 2.973, P = 0.0013, n = 11) and they were completely decoupled for Viverridae-Herpestidae (LR; y0 = 43.386, a = 0.064, R2 = 0.003, SEE = 5.519, P = 0.802, n = 36), all frugivorous, omnivorous or carnivorous hunters of small prey. For Ursids (n = 4) and for Hyaenids (n = 3) there was a very low fit between measured and predicted gape, reflecting the back-molar crushing employed by bears and in hyenas bone-cracking using third premolars.


Sabretoothed carnivores and the killing of large prey.

Andersson K, Norman D, Werdelin L - PLoS ONE (2011)

Canine size follows gape for carnivorans with canine killing bite habits.Measured gape plotted against gape predicted from canine size, for fossil sabretooths (white symbols and dash-dot regression line), present day non-sabretoothed carnivorans (Felidae, light gray symbols and dashed regression line; all other carnivoran families, dark grey symbols and dotted regression line). The solid line marks isometry (y = x) between measured and predicted gape and bubble diameters represent Rshift values (not to scale). Gape is measured as the angle formed between the craniomandibular-joint and the tips of the incisors. Gape is predicted assuming canine clearance equal to the combined height of the upper and lower canine and calculated as the sum thereof.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3198467&req=5

pone-0024971-g002: Canine size follows gape for carnivorans with canine killing bite habits.Measured gape plotted against gape predicted from canine size, for fossil sabretooths (white symbols and dash-dot regression line), present day non-sabretoothed carnivorans (Felidae, light gray symbols and dashed regression line; all other carnivoran families, dark grey symbols and dotted regression line). The solid line marks isometry (y = x) between measured and predicted gape and bubble diameters represent Rshift values (not to scale). Gape is measured as the angle formed between the craniomandibular-joint and the tips of the incisors. Gape is predicted assuming canine clearance equal to the combined height of the upper and lower canine and calculated as the sum thereof.
Mentions: To test canine clearance and its assumptions for point-to-point biting we compared measured actual gape angle at maximum jaw extension to gape angles predicted for an optimal canine-height and gape configuration for a range of extant and extinct carnivorans (Fig. 2). Gape angles were predicted by assuming a one to one relationship between the combined crown height of the upper and lower canines and the distance or “clearance” between the tips at maximum jaw extension. For canids, which typically kill large prey with multiple bites [21], measured- and predicted gape were loosely correlated (Linear Regression (LR); y0 = 16.838, a = 1.141, R2 = 0.701, SEE = 2.973, P = 0.0013, n = 11) and they were completely decoupled for Viverridae-Herpestidae (LR; y0 = 43.386, a = 0.064, R2 = 0.003, SEE = 5.519, P = 0.802, n = 36), all frugivorous, omnivorous or carnivorous hunters of small prey. For Ursids (n = 4) and for Hyaenids (n = 3) there was a very low fit between measured and predicted gape, reflecting the back-molar crushing employed by bears and in hyenas bone-cracking using third premolars.

Bottom Line: For sabretooths, this size-reversed functional advantage suggests predation on species within a similar size range to those attacked by present-day carnivorans, rather than "megaherbivores" as previously believed.The development of the sabretooth condition appears to represent a shift in function and killing behaviour, rather than one in predator-prey relations.We anticipate this new insight to be a starting point for detailed study of the evolution of pathways that encompass extreme specialisation, for example, understanding how neck-powered biting shifts into shear-biting and its significance for predator-prey interactions.

View Article: PubMed Central - PubMed

Affiliation: Department of Earth Sciences, University of Cambridge, Cambridge, United Kingdom. andersson.ki@gmail.com

ABSTRACT
Sabre-like canines clearly have the potential to inflict grievous wounds leading to massive blood loss and rapid death. Hypotheses concerning sabretooth killing modes include attack to soft parts such as the belly or throat, where biting deep is essential to generate strikes reaching major blood vessels. Sabretoothed carnivorans are widely interpreted as hunters of larger and more powerful prey than that of their present-day nonsabretoothed relatives. However, the precise functional advantage of the sabretooth bite, particularly in relation to prey size, is unknown. Here, we present a new point-to-point bite model and show that, for sabretooths, depth of the killing bite decreases dramatically with increasing prey size. The extended gape of sabretooths only results in considerable increase in bite depth when biting into prey with a radius of less than ∼10 cm. For sabretooths, this size-reversed functional advantage suggests predation on species within a similar size range to those attacked by present-day carnivorans, rather than "megaherbivores" as previously believed. The development of the sabretooth condition appears to represent a shift in function and killing behaviour, rather than one in predator-prey relations. Furthermore, our results demonstrate how sabretoothed carnivorans are likely to have evolved along a functionally continuous trajectory: beginning as an extension of a jaw-powered killing bite, as adopted by present-day pantherine cats, followed by neck-powered biting and thereafter shifting to neck-powered shear-biting. We anticipate this new insight to be a starting point for detailed study of the evolution of pathways that encompass extreme specialisation, for example, understanding how neck-powered biting shifts into shear-biting and its significance for predator-prey interactions. We also expect that our model for point-to-point biting and bite depth estimations will yield new insights into the behaviours of a broad range of extinct predators including therocephalians (gorgonopsian + cynodont, sabretoothed mammal-like reptiles), sauropterygians (marine reptiles) and theropod dinosaurs.

Show MeSH
Related in: MedlinePlus