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Bite club: Comparative bite force in big biting mammals and the prediction of predatory behaviour in fossil taxa


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We provide the first predictions of bite force (BS) in a wide sample of living and fossil mammalian predators. To compare between taxa, we calculated an estimated bite force quotient (BFQ) as the residual of BS regressed on body mass. Estimated BS adjusted for body mass was higher for marsupials than placentals and the Tasmanian devil (Sarcophilus harrisii) had the highest relative BS among extant taxa. The highest overall BS was in two extinct marsupial lions. BFQ in hyaenas were similar to those of related, non-osteophagous taxa challenging the common assumption that osteophagy necessitates extreme jaw muscle forces. High BFQ in living carnivores was associated with greater maximal prey size and hypercarnivory. For fossil taxa anatomically similar to living relatives, BFQ can be directly compared, and high values in the dire wolf (Canis dirus) and thylacine (Thylacinus cynocephalus) suggest that they took relatively large prey. Direct inference may not be appropriate where morphologies depart widely from biomechanical models evident in living predators and must be considered together with evidence from other morphological indicators. Relatively low BFQ values in two extinct carnivores with morphologies not represented among extant species, the sabrecat, Smilodon fatalis, and marsupial sabretooth, Thylacosmilus atrox, support arguments that their killing techniques also differed from extant species and are consistent with 'canine-shear bite' and 'stabbing' models, respectively. Extremely high BFQ in the marsupial lion, Thylacoleo carnifex, indicates that it filled a large-prey hunting niche.
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Bite club: comparative bite force in big biting
mammals and the prediction of predatory
behaviour in fossil taxa
Stephen Wroe
, Colin McHenry
and Jeffrey Thomason
School of Biological Sciences (A08), University of Sydney, NSW, Australia 2006
School of Environmental and Life Sciences (Earth Sciences), University of Newcastle, NSW, Australia 2308
Department of Biomedical Sciences, University of Guelph, Ontario, Canada N1G 2W1
We provide the first predictions of bite force (B
) in a wide sample of living and fossil mammalian
predators. To compare between taxa, we calculated an estimated bite force quotient (BFQ) as the residual
of B
regressed on body mass. Estimated B
adjusted for body mass was higher for marsupials than
placentals and the Tasmanian devil (Sarcophilus harrisii) had the highest relative B
among extant taxa. The
highest overall B
was in two extinct marsupial lions. BFQ in hyaenas were similar to those of related, non-
osteophagous taxa challenging the common assumption that osteophagy necessitates extreme jaw muscle
forces. High BFQ in living carnivores was associated with greater maximal prey size and hypercarnivory.
For fossil taxa anatomically similar to living relatives, BFQ can be directly compared, and high values in the
dire wolf (Canis dirus) and thylacine (Thylacinus cynocephalus) suggest that they took relatively large prey.
Direct inference may not be appropriate where morphologies depart widely from biomechanical models
evident in living predators and must be considered together with evidence from other morphological
indicators. Relatively low BFQ values in two extinct carnivores with morphologies not represented among
extant species, the sabrecat, Smilodon fatalis, and marsupial sabretooth, Thylacosmilus atrox, support
arguments that their killing techniques also differed from extant species and are consistent with ‘canine-
shear bite’ and ‘stabbing’ models, respectively. Extremely high BFQ in the marsupial lion, Thylacoleo
carnifex, indicates that it filled a large-prey hunting niche.
Keywords: bite force; prey size; osteophagy; Carnivora; Dasyuromorphia; Thylacoleonidae
Bite force (B
) is an important aspect of carnivore ecology,
with the potential to shed light on the evolution of
community structure and prey size in fossil taxa (Meers
2002; Vizcaı
no & de Iuliis 2003; Rayfield 2004). However,
empirical data are not easily obtained; B
has been
measured in only three mammalian carnivore species
(Thomason 1991; Dessem & Druzinsky 1992; Binder &
Van Valkenburgh 2000) and the comparative biology of B
in mammals has remained largely unexplored. Important
unanswered questions are: is bite force (i) allometrically
related to body mass, (ii) phylogenetically constrained,
(iii) more strongly influenced by skull length or skull
width, (iv) relatively higher in bone-cracking specialists
and (v) related to prey size in extant taxa? Answers will
define the limits of using B
estimate as a predictor of
behaviour and prey size in fossil species.
We calculated theoretical maximum bite forces using the ‘dry
skull’ method (Thomason 1 991; Electronic Appendices,
sections A and B). Our sample comprised 49 specimens
representing 39 taxa (31 extant and eight extinct). The dry
skull method, derived from relationships between skull
dimensions and jaw muscle cross-sectional areas, models the
jaw as a simple lever. It is most applicable to the anterior-most
portion of the jaw, where the caniniform teeth are located
(Electronic Appendix, section A). Consequently, and
because morphology of the canines has long been considered
a significant predictor of predatory behaviour in mammalian
carnivores (Wroe et al. 1998; Farlow & Pianka 2002), we
have largely restricted our discussion to estimates of force for
static bites at the canines (CB
). However, analyses of B
the carnassial showed the same qualitative trends as for CB
(Electronic Appendix, section C). A further advantage of the
‘dry skull’ method is that because results are derived solely
from skull morphology, comparisons can be made between
fossil and extant taxa.
The relationship between CB
and body mass between
species is allometri c (figure 1; Meers 2002; r
Z0.85). To
compare bite forces in taxa of greatly differing body masses an
estimated bite force quotient (BFQ) was calculated using the
residuals of regression (table 1; Electronic Appendix, section
A). ‘Average’ BFQ was set at 100. Variance in allometry
adjusted bite force is small relative to that for absolute B
(Thomason 1991; Electronic Appendix, section D) and a
second advantage of using BFQ is that it allows more
meaningful comparisons based on small datasets. This quality
is particularly valuable in analyses incorporating fossil taxa
where sample sizes are limited.
The highest B
estimate adjusted for body mass were
Proc. R. Soc. B
Published online
* Author for correspondence (
Received 28 July 2004
Accepted 16 October 2004
1 q 2005 The Royal Society
in two extinct marsupial lions, Thylacoleo carnifex (194)
and Priscileo roskellyae (196). The lowest was also in a fossil
marsupial, Thylacosmilus atrox (41). Among extant carni-
vorous mammals the highest BFQ was in the Tasmanian
devil, Sarcophilus harrisii (181). For placentals, BFQ was
greatest in the Pleistocene dire wolf, Canis dirus (163).
Another canid, the African hunting dog, Lycaon pictus, had
the highest BFQ for living Carnivora (142).
Mean BFQ was higher in marsupials than placentals
(158 versus 98), although marsupials do not have larger
heads—relationships between head lengths and body
masses in dasyuromorphians were similar to those of
canids, and thylacoleonids were similar to felids (figure 2).
However, relative to body mass, CB
was significantly
higher in dasyuromorphians than in canids (F
p!0.01) and significantly higher in thylacoleonids than in
cats (F
Z11.84, p!0.01).
The average BFQ for Felidae (104) was slightly less
than in Canidae (110) and dogs had greater head to body
size (figure 2), but the difference in this instance was not
significant. Across all taxa, skull width was a better
predictor of CB
than skull length (r
Z0.92 and 0.78,
respectively; Thomason 1991).
was considerable for specialist bone-crackers
included in our study, the spotted and brown hyaenas
(Crocuta crocuta and Hyaena hyaena) and the Tasmanian
devil (S. harrisii). However, in the two hyaenids, BFQ at
the canine was exceeded by several non-osteophagous
carnivorans (figure 1; table 1) and BFQ for the Tasmanian
devil was not much above average for dasyuromorphians
and less than in two marsupial lions. BFQ at the carnassial
teeth followed a similar pattern (Electronic Appendix,
section C), an expected result because the position of the
carnassial varies little among mammalian predators
(Greaves 1983).
As an upper restriction on niche, a predator’s maximal
prey size is an important component of its ecology and is
likely to be strongly influenced by its biomechanical limits.
Predator body mass has been shown to correlate with
maximal prey size in mammals (Meers 2002).
Amo ng extant canids, the four hypercarnivores that
often prey on animals larger than themselves, the grey
wolf (Canis lupus lupus), dingo (C. l. dingo), African
hunting dog (L. pictus) and the dhole (Canis alpinus), have
the highest BFQ (108–142). BFQ was consistently lower
in the five more solitary, omnivorous foxes, jackals and
coyote characterized by relatively low maximal prey sizes
(80–97). Thus, although the ability to bring down large
prey in canids is related to cooperative hunting, it is still
reflected in a higher BFQ. Within living Felidae, BFQ
values were 57 and 75 for the two species that specialize in
relatively small prey, while BFQ was 94 or greater for the
seven known to take relatively la rge prey (table 2).
adjusted for body mass was also low in bears
(44–78), which are restricted to relatively small prey
(Meers 2002). BFQ was higher in extant dasyuromor-
phian marsupials, but the same trends were evident. The
lowest BFQ was in the eastern quoll (Dasyurus viverrinus),
which takes comparatively smaller p rey and is less
carnivorous than the other marsupials considered (see
below). Overall, BFQ was 100 or higher in 15 of the 16
extant placental and marsupial carnivores sampled that
take prey larger than their own maximal body masses. In
12 of the 14 extant species where maximal prey size was
less than the species’ mean body mass, BFQ was less than
100 (table 2). The difference between large and small prey
specialists was significant (t(28)ZK4.92, p!0.01) and
hypercarnivores had significantly higher values for
BFQ than more o mnivorous species (t(28)ZK3.33,
p!0.02; table 2).
(a) Comparisons between extant taxa
Results suggest that, relative to body mass, calculated
canine B
is considerably higher in marsupials than in
0 0.5 1.0 1.5 2.0 2.5 3.0
log10 BoM (kg)
log10 CBs (N)
Figure 1. Log predicted canine bite force (CB
) plotted against log body mass (BoM). Reg ression for all extant taxa Z solid
black line. Individual data points are: for felids (open triangles), canids (grey filled triangles), dasyuromorphians, grey filled
squares, thylacoleonids (black filled squares), hyaenids (grey filled diamonds), ursids, a mustelid and a viverrid (g rey crosses),
and a thylacosmilid (open squares). Species abbreviations as in table 1.
2 S. Wroe and others Bite force and predatory behaviour
Proc. R. Soc. B
placentals and this cannot simply be explained by
differences in head size. The presence of the superfast
myosin isoform in both carnivorans and dasyuromor-
phians suggests that their muscle microphysiology is
similar (Hoh et al. 2001). Differences between these two
groups may relate to brain volumes, which, in carnivor-
ans, are around two and a half times that of marsupial
carnivores (Wroe et al. 2003). Within the temporal
region of the skull, cross-sectional area places limits on
the maximal force that can be generated by muscle
(Thomason 1991), and expansion of brain volume
impinges on available muscle area within the zygoma.
Consequently, within a skull of given length and width,
greater brain size impinges on maximal B
. Extant
carnivorans may have more precisely targeted killing
behaviours than marsupial counterparts (Ewer 1969)
and through greater efficiency may be able to accom-
plish similar results with less B
. Because mean BFQ in
marsupials is much high er than in placentals, our
finding that the relatively omnivorous D. viverrinus has
a BFQ well within the range of hypercarnivorous
placentals is consistent with this interpretation. If in
vivo testing shows that placentals produce bite
forces that are similar, after adjustment for body mass,
to marsupials, it will probably be a result of differences
in jaw muscle anatomy, such as muscle pennation or
microphysiology, although none have been clearly
identified to date.
Mean BFQ was lower in cats than canids, reflecting the
smaller head size of cats relative to body mass, but relative
to skull length, CB
in felids was greater, possibly because
of their greater skull width relative to length (Electronic
Appendices, sections E and F). Although extant canids
and dasyuromorphians have higher mean BFQ than felids,
the shorter skull of cats may confer greater resistance to
forces produced by struggling prey. Cats also have more
powerful, flexible forelimbs, of critical utility in violent,
close quarter interactions and may recruit ventral cervical
Table 1. Measurements of basal skull length (BSL) and maximum skull width at the zygoma (SWZ); and estimates of body mass
(BoM), canine bite force (CB
), and bite force quotient (BFQ), for 39 taxa of recent and fossil mammals.
(Measurements and calculations were taken from prepared skulls. Methods for body mass estimations given in Electronic
Appendix, section A. Fossil taxa indicated with †.)
species family BSL (cm) SWZ (cm) BoM (kg) CB
Alopex lagopus Canidae 13.86 8.05 8.2 178 97
Canis alpinus Canidae 17.69 10.78 16.5 314 112
Canis aureus Canidae 13.53 8.12 7.7 165 94
Canis lupus dingo (C l.d) Canidae 18.04 9.97 17.5 313 108
Canis lupus hallstromi Canidae 15.95 9.41 12.3 235 100
Lycaon pictus (L.p) Canidae 18.52 13.18 18.9 428 142
Vulpes vulpes (V.v) Canidae 13.79 7.35 8.1 164 92
Urocyon cineroargentus Canidae 11.91 6.14 5.3 114 80
Canis latrans ( Canidae 18.85 9.86 19.8 275 88
Canis lupus lupus (C.l.l) Canidae 22.92 13.22 34.7 593 136
Canis dirus Canidae 26.19 17.58 50.8 893 163
Ursus americanus Ursidae 24.39 17.2 105.2 541 64
Ursus arctos Ursidae 26.96 16.28 128.8 751 78
Ursus thibetanus Ursidae 20.92 11.07 77.2 312 44
Meles meles Mustelidae 12.31 8.05 11.4 244 109
Gennetta tigrinus Viverridae 10.93 5.19 6.2 73 48
Crocuta crocuta (Cr.c) Hyaenidae 23.64 16.73 69.1 773 117
Hyaena hyaena Hyaenidae 19.98 15.18 40.8 545 113
Proteles cristatus Hyaenidae 12.46 7.22 9.3 151 77
Panthera onca (P. o ) Felidae 22.25 18.63 83.2 1014 137
Panthera tig ris Felidae 28.86 22.73 186.9 1525 127
Acinonyx jubatus Felidae 15.93 12.30 29.5 472 119
Felis yagouaroundi Felidae 10.09 6.94 7.1 127 75
Lynx rufus Felidae 7.58 5.93 2.9 98 100
Felis concolor (F. c ) Felidae 16.77 12.92 34.5 472 108
Felis sylvestris (F. s ) Felidae 7.51 5.39 2.8 56 58
Neofelis nebulosa Felidae 16.74 11.88 34.4 595 137
Panthera leo (P. l ) Felidae 33.41 24.81 294.6 1768 112
Panthera pardus Felidae 18.01 13.02 43.1 467 94
Smilodon fatalis †(Sm.f) Felidae 29.48 19.53 199.6 976 78
Dasyurus maculatus (D.m) Dasyuridae 10.09 6.01 3.0 153 179
Dasyurus viverrinus Dasyuridae 7.27 4.15 0.87 65 137
Sarcophilus harrisii (S.h) Dasyuridae 13.96 11.17 12.0 418 181
Nimbacinus dicksoni Thylacinidae 13.24 8.08 5.3 267 189
Thylacinus cynocephalus (T. c) Thylacinidae 25.04 14.83 41.7 808 166
Priscileo roskellyae Thylacoleonidae 8.34 6.34 2.7 184 196
Wakaleo vanderleurei Thylacoleonidae 18.53 12.58 41.4 673 139
Thylacoleo carnifex †(Th.c) Thylacoleonidae 24.04 20.15 109.4 1692 194
Thylacosmilus atrox †(Thy.a ) Thylacosmilidae 257.71 139.65 106 353 41
Bite force and predatory behaviour S. Wroe and others 3
Proc. R. Soc. B
musculature to assist in jaw closure (Van Valkenburgh
et al. 2003; Anto
n et al. 2004).
(b) Bite force and osteophagy
Our finding that BFQ at both the canine and carnassial in
osteophages were often comparable to, and sometimes less
than, many non-osteophagous relatives was unexpected.
This may have important implications re garding the
biomechanics of osteophagy.
In most carnivores, maximal bite forces are used in the
killing bite at the canines where maximal loads will be
distributed between adjacent teeth in the anterior region of
1 10 100 1000
BoM (kg)
BSL (cm)
Figure 2. Basal skull length (BSL) plotted against body mass (BoM). Power regressions are shown for felids (black dashed line),
canids (grey solid line), dasyuromorphians (grey dashed line), thylacoleonids (black solid line). Symbols as in figure 1.
Table 2. Bite force adjusted for body mass allometry (BFQ), maximal prey size and feeding category in 31 extant mammalian
(RMPS, maximal prey size (1, greater than maximal body mass of predator; 2, less than maximal body mass of predator); FC,
feeding category (1, hypercarnivore; 2, other); ‘—’, insufficient data. Maximal body mass data largely from Meers (2002).For
additional data see Electronic Appendix, section A.)
species common name family BFQ RMPS FC
Alopex lagopus Arctic fox Canidae 97 2 2
Canis alpinus Dhole Canidae 112 1 1
Canis aureus golden jackal Canidae 94 2 2
Urocyon cineroargentus grey fox Canidae 80 2 2
Canis lupus dingo Dingo Canidae 108 1 2
Canis lupus hallstromi singing dog Canidae 100
Lycaon pictus African hunting dog Canidae 142 1 1
Vulpes vulpes red fox Canidae 92 2 2
Canis latrans Coyote Canidae 88 2 2
Canis lupus lupus grey wolf Canidae 136 1 1
Ursus americanus black bear Ursidae 64 2 2
Ursus arctos brown bear Ursidae 78 2 2
Ursus thibetanus Asiatic bear Ursidae 44 2 2
Gennetta tigrinus striped genet Viverridae 48 2 2
Meles meles European badger Mustelidae 109 2 2
Crocuta crocuta spotted hyaena Hyaenidae 117 1 1
Hyaena hyaena brown hyaena Hyaenidae 113 1 1
Proteles cristatus Aardwolf Hyaenidae 77 2 2
Panthera onca jaguar Felidae 137 1 1
Panthera tigris tiger Felidae 127 1 1
Felis concolor cougar Felidae 108 1 1
Acinonyx jubatus cheetah Felidae 119 1 1
Felis yagouaroundi jaguarundi Felidae 75 2 1
Lynx rufus bobcat Felidae 100 1 1
Felis sylvestris catus cat Felidae 58 2 1
Neofelis nebulosa clouded leopard Felidae 137 1 1
Panthera leo lion Felidae 112 1 1
Panthera pardus leopard Felidae 94 1 1
Dasyurus maculatus spotted-tailed quoll Dasyuridae 179 1 1
Dasyurus viverrinus eastern quoll Dasyuridae 137 2 2
Sarcophilus harrisii Tasmanian devil Dasyuridae 181 1 1
4 S. Wroe and others Bite force and predatory behaviour
Proc. R. Soc. B
the jaw. In contrast, osteophagy requires the concentration
of high loads on a limited part of the food item in order to
produce material failure. The highest bite forces are
typically achievable in carnassial biting, which is restricted
to one side of the mandible rather than distributed between
left and right jaws (Greaves 1983). In hyaenids, maximum
forces may be generated immediat ely anterior to the
carnassial (Werdelin 1989). Moreover, from observation,
osteophages may use kinetic, rather than static bites to
crack bones, fur ther increasing loads. Consequently,
theoretical forces that can be achieved are far greater than
those experienced during a canine bite. The application of
maximal bite forces at post-canine teeth on hard materials
requires very robust dentitions, as evidenced in specialized
bone-crackers such C. crocuta, H. hyaena and S. harrisii.
Our results suggest that although the capacity of teeth (and
probably crania) to resist high stresses on hard substances in
the cheek–tooth row is an essential adaptation to specialized
osteophagy in mammals, particularly high bite strength
relative to body size is not. The flipside of this argument is
that many felids and canids could theoretically apply
relatively greater bite forces at a single point in the cheek–
tooth row than could a same-sized hyaenid. However, we
posit that in practice, non-osteophageous taxa will not
voluntarily develop maximal bite forces in a post-canine
bite because neither their dentitia nor their crania are
optimized to resist such high stresses in this region. Unused
capacity at the carnassial in non-osteophages may be an
incidental product of the requirement for high B
at the
canines as part of their killing strategy.
(c) Bite force and the prediction of feeding ecology
(i) Extant carnivores
Our results demonstrate that among living mammalian
carnivores, BFQ is a broad indicator of relative prey size
and feeding ecology. However, considered in isolation, B
adjusted for body mass is not an infallible predictor. In
the aardwolf (Proteles cristatus), BFQ is low (77), but
higher than in some bears, a viverr id and two small cat
species (table 2). Although this finding is consistent in
that all take relatively small prey, it does not reflect the
fact that P. cristatus subsists largely on termites. Interest-
ingly, the unusual, hypotrophied post-canine morphology
of the aardwolf unambiguously suggests that vertebrates
are rarely taken, but the canines are quite well developed.
Together with moderate BFQ, this indicates that it is
physically capable of killing much larger prey than it does.
The retention of functional canines and moderate BFQ
in P. cristatus may be related to intra and/or interspecific
defence. Either way, the aardwolf clearly lies outside
generalized biomechanical subcategories, such as the cat
and dog types, which themselves differ in details
including head shape, canine cross-sectional mor-
phologies and killing behaviour. This example demon-
strates well that BFQ may not directly reflect feeding
ecology for morphologically atypical taxa that do not fit
within generalized biomechanical models. Consequently,
in the reconstruction of ecology for fossil carnivores,
BFQ must be qualified against the type and extent
of morphological departure from biomechanical sub-
categories observable in living species. For example,
predictions incorporating BFQ for fossil cats, or taxa with
cat-like morphologies, are best made on the basis of
comparisons with extant felids.
(ii) Extinct taxa with morphologically similar
extant relatives
Neither cranial, nor post-cranial morphology of the
thylac ine, Thylacinus cynocephalus, differ greatly from
those of living dasyuromorphians (Wroe 2003). Based
on low rates of canine tooth breakage and snout
morphology, it has been argued that thylacines may have
been restricted to small or medium sized prey (Jones 2003;
Johnson & Wroe 2003). Our finding that BFQ was
comparable to extant dasyuromor phians known t o
take relatively large prey is contra these interpretations
(table 1). Similarly, high BFQ in the Miocene thylacinid,
Nimbacinus dicksoni, suggests that relatively large prey
were accessible to this anatomically conservative species.
Likewise, among fossil placentals, morphology of the
dire wolf (C. dirus) is similar to that of living relatives. If
C. dirus was a social hunter, then its high BFQ (163)
relative to extant canids su ggests that it preyed on
relatively large animals.
(iii) Extinct taxa without morphologically similar
living relatives
Some fossil taxa included in our analyses clearly fell well
outside extant morphotypes. Major differences between
the sabrecat Smilodon fatalis and all extant felids,
including extreme hypertr ophy of the canine s, very
powerful forelimbs, lengthening of the neck and short-
ening of the lumbar region, leave little doubt that it used
killing techniques not represented among living carni-
vores and regularly took large prey (Janis 1994; Anto
Galobar t 1999; Anto
n et al. 2004; Argot 2004).
Notwithstanding its high absolute CB
compared with
large living felids, BFQ in S. fatalis was low (78). Having
secured large prey with its muscular forelimbs, S. fatalis
used its hypertrophied canines to effect fatal trauma
n et al. 2004; Argot 2004). The reduced cross-
sectional area of the canines in sabrecats may require
relatively less bite force than that used by living Panthera
(M. Meers, personal communication). In the marsupial
sabretooth, T. atrox, both BFQ (41) and absolute B
extremely low, but as with S. fatalis,post-cranial
adaptations and canine morphology indicate a killing
technique without present day analogy and systematic
predation on relatively large taxa (Argot 2004).
Current functional models of sabretooth killing be-
haviour include: (i) the ‘stabbing’ model in which the
force applied to the canines is primarily neck-driven
n & Galobart 1999; Argot 2004) and (ii) a ‘canine-
shear bite’, in which significant absolute force is required
of the jaw adductors in conjunction with input from neck
muscles (Akersten 1985). Because absolute CB
S. fatalis is high, and BFQ is considerably higher than
in T. atrox, our results are consistent with the ‘canine
shear-bite’ model for the sabrecat, with significant force
required of the jaw adductors in conjunction with cervical
musculature. From estimates of bending strength in the
mandibular cor pus, Bickne vicus & Van Valkenburgh
(1996) posit that S. fatalis may have applied a sustained
throat clamping bite. Our results do not rule out
this possibility, but are contra the conclusion that bite
Bite force and predatory behaviour S. Wroe and others 5
Proc. R. Soc. B
force in S. fatalis was comparable to that of similar sized
pantherines. However, in the marsupial sabretooth, CB
and BFQ are both so low that we consider our result
supportive of a primarily neck-driven use of the canines
and strongly contra the possibility that T. atrox applied a
sustained throat bite to dispatch large prey.
For the marsupial lion, T. carnifex, BFQ was the highest
of any large predator and its CB
approached that of a lion
(Panthera leo ) more than twice its size (table 1). If the
killing mechanism of T. carnifex was functionally equival-
ent to that of extant felids, our results suggest that it could
take prey much larger than itself. However, although cat-
like in many respects, its dentition is unusual and
interpretation of feeding ecology in the marsupial lion
has long attracted controversy (Wells et al. 1982; Wroe et
al. 2004a). Our findings confirm that short outlever arms
and anteriorly placed muscle resultants conferred high
mechanical efficiency (Wells et al. 1982). The marsupial
lion’s vertical shearing ‘carnassial’ cheek–teeth are rela-
tively larger than in any other mammalian carnivore (Wells
et al. 1982; Werdelin 1988). Brought together with a very
high B
, these carnassials may have enabled T. carnifex to
rapidly slice through tracheas or vital blood vessels and
quickly dispatch large, potentially dangerous prey,
although mechanical simulation will be required to
confirm this. When CB
and BFQ are considered together
with forelimb, cervical and lumbar morphology that
converges on that of marsupial and placental sabretooths,
as well as taphonomic data (Janis 1994; Wroe 2003; Argot
2004), the marsupial lion may have been capable of taking
sub-adults of the heaviest available prey (Wroe et al.
The dry skull method, because it takes into account subtle
changes in the shape of the skull and jaws, provides
estimates of B
that can be applied across unrelated taxa
and thus allows quantitative comparisons of this import-
ant component of a predator’s biomechanical perform-
ance. Adjusted for body mass, our estimates of B
(i) show
variations that are broadly consistent with patterns of
predatory behaviour and diet obser ved in extant carni-
vores, (ii) provide a basis for predicting maximal prey size
in extinct mammalian predators that are morpholog ically
similar to extant predators, (iii) allow quantifiable
comparisons of biomechanics within ecomorphs, where
there are no living analogues, such as sabretooths and (iv)
challenge the widely held assumption that osteophagy
requires relatively higher B
than that seen in non-
osteophagous relatives. Mechanical simulations a nd
further investigations of jaw muscle anatomies and the
mechanics of the skull, using FEA modelling (Daniel &
McHenr y 2001; Snively & Russell 2002; Rayfield 2004)
and in vivo force measurement, will fur ther clarify these
patterns and permit examination of the following predic-
tions inferred from our analyses: (i) the biomechanics of
osteophagy are more tightly constrained by the structural
properties of the carnivore’s skull and dentition than by
muscle force, (ii) non-osteophagous large prey specialists
should be reluctant to apply all available muscle force in a
post-canine bite, because of the threat of material failure
(moreover, their crania will be optimized to resist stress
at the canines, while in specialist bone-crackers skulls will
be optimized to resist stress near the carnassial) and (iii) if
in vivo testing shows that placentals produce bite forces
that are similar after allometric adjustment to marsupials,
it will be because of differences in muscle anatomy and
We are much indebted to M. Meers, J. Farlow, A. Herrel,
G. Erickson, B. Van Valkenburgh, L. Werdelin, E. Rayfield,
E. Snively, D. Hu ber, C. Vineyard, M. Crowther,
P. Christiansen and M. Jones for advice on previous versions
and the provision of unpublished data. We also thank
D. Wroe, P. Adam, P. Clausen, I. Johnston, S. Johnston,
D. Hochuli and K. Wyatt. Work was funded by a University of
Sydney Research Fellowship (to S.W.).
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Wroe, S., Crowther, M., Dortch, J. & Chong, J. 2004b
The size of the largest marsupial and why it matters.
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The supplementary Electronic Appendix is available at http://dx.doi.
org/10.1098/rspb.2004.2986 or via
As this paper exceeds the maximum length normally permitted, the
authors have agreed to contribute to production costs.
Bite force and predatory behaviour S. Wroe and others 7
Proc. R. Soc. B
... pairs of teeth in contact during the bite, and only one of them is modelled here. Hence, the sphere is assigned a mass of m = 3 kg, being one fourth of the mass of a lion's head [121]. ...
... Additionally, a downwards force of F = 442 N is applied to the sphere as one fourth of a lion's bite strength [121]. The sphere is also assigned an initial velocity of v i = 2 m/s. ...
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Many natural protective structures, such as alligator armour, turtle shells, and the skulls of many animals including humans, contain networks of sutures; those are, soft tissue that bonds adjacent stiff plates typically made of bone. Such protective structures ought to withstand large loads associated with predator attacks. If one considers the optimization process of evolution and the ubiquity of suture networks in natural protective structures, it is reasonable to hypothesize that sutures improve the mechanical behaviour of protective structures during predator attacks. However, the effect of sutures in such loading scenarios is not well understood. We address this by using computational models of turtle shells where special attention is paid to the influence of the network of sutures. Additionally, we elucidate the structure-function relationship using parametric studies varying the suture geometry. Computational experiments are carried out at the suture scale to elucidate its mechanical behaviour and at the shell scale to elucidate the effect that sutures have on the shell. Among other insights, we show that: the compliance of the shell during small deformations can be increased by increasing the height of the interlocking bone protrusions and suture thickness; the bone plates interlock for sufficiently large deformations of sutures with sufficiently long protrusions; suture geometry can be used to tailor stress-wave propagation; and the presence of sutures can reduce the maximum strain energy density, a key indicator for a material failure, during a predator attack by 31 times. The work presented paves the way for the inclusion of sutures in biomimetic protective structures such as helmets and body armour. Computational solid mechanics aspects include multiscale modelling, model order reduction, and finite strain constitutive modelling aspects, such as viscoelasticity, hyperelasticity, and anisotropy.
... One of the most used ways to calculate bite force is the dry-skull method developed by Thomason (1991), which reconstructs the adductor musculature to estimate the muscle forces solely using the skull morphology, modelling the jaws as simple levers. It has been applied in analyses of muscular and bite force in many organisms, including canids TA B L E 2 Total force inferred for the bites in the intrinsic scenarios (Christiansen & Wroe, 2007;Ellis et al., 2008;Nanova et al., 2017;Penrose et al., 2020;Wroe et al., 2005). ...
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Cerdocyonina is a clade composed by the South‐American canids in which the bush dog (Speothos venaticus) is one of the most elusive species. Known for its unique morphology within the group, this small, bear‐like faced canid is the only member of the clade adapted to hypercarnivory, an almost exclusively meat‐based diet currently present only in usually large, pack‐hunting canids such as the grey wolf (Canis lupus). However, much of the biology of the bush dog is poorly understood, and inferences about its ecology, hunting strategies and diet are usually based on observation of captive individuals and anecdotal records, with reduced quantitative data to offer support. Here, we investigated the craniomandibular functional morphology of the bush dog through finite element analysis (FEA). FEA was employed to model the biting behaviour and to create extrinsic and intrinsic functional scenarios with different loads, corresponding to different bites used to subdue and process the prey. For comparison, the same modelling was applied to the skull of a grey wolf and a grey fox (Urocyon cinereoargenteus). Our analysis showed that the bush dog's responses to loading are more similar to the wolf's than to the fox's in most scenarios, suggesting a convergent craniomandibular functional morphology between these two hypercarnivorous species, despite their distinct phylogenetic positions and body sizes. Differences between the three taxa are noteworthy and suggested to be related to the size of the usual prey. The modelled bite force for the bush dog is relatively strong, about half of that estimated for the wolf and about 40% stronger than the fox's bite. The results strengthen with quantitative data the inferences of the bush dog as a pack‐hunting predator with prey size similar to its own, such as large rodents and armadillos, being specialised in subduing and killing its prey using multiple bites. Its similarity to the wolf also confirms anecdotal accounts of predation on mammals that are much larger than itself, such as peccaries and tapirs. These data highlight the ecological specialisation of this small canid in a continent where large, pack‐hunting canids are absent. Von Mises stress contour plots from finite element analysis of the intrinsic scenarios modelled to the mandibles of the bush dog (Speothos venaticus), grey wolf (Canis lupus) and grey fox (Urocyon cinereoargenteus). Asterisks indicate the placement of the tooth bite. The mean von Mises stress of each scenario is shown in the bottom right. CanU: unilateral canine‐driven bite; CarU: unilateral carnassial‐driven bite; CanB: bilateral canine‐driven bite; CarB: bilateral carnassial‐driven bite.
... To estimate the forces (Newtons) pulling each muscle insertion, the insertion area (mm 2 ) was multiplied by 0.3N/mm² based on the maximum tension produced by mammalian muscle fibres [30]. All biting simulations were unilateral (left and right side were simulated in different scenarios) so to compensate the balancing side muscle forces were multiplied by 0.6 of working side muscles, following [31]. ...
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Cat-like carnivorans are a textbook example of convergent evolution with distinct morphological differences between taxa with short or elongated upper canines, the latest being often interpreted as an adaptation to bite at large angles and subdue large prey. This interpretation of the sabretooth condition is reinforced by a reduced taxonomic sampling in some studies, often focusing on highly derived taxa or using simplified morphological models. Moreover, most biomechanical analyses focus on biting scenarios at small gapes, ideal for modern carnivora but ill-suited to test for subduction of large prey by sabre-toothed taxa. In this contribution we present the largest 3D collection-based muscle-induced biting simulations on cat like carnivorans by running a total of 1,074 analyses on 17 different taxa at three different biting angles (30°, 60° and 90°) including both morphologies. While our results show a clear adaptation of extreme sabre-toothed taxa to bite at larger angles in terms of stress distribution, other performance variables display surprising similarities between all forms at the different angles tested, highlighting a continuous rather than bipolar spectrum of hunting methods in cat-like carnivorans and demonstrating a wide functional disparity and nuances of the sabretooth condition that cannot simply be characterized by specialized feeding biomechanics.
... These taxa also have the least optimized out-lever in the lower jaw. The anterior jaw is where maximal loads are dealt with (Wroe et al., 2005) and is therefore important when processing prey items. Plagiophthalmosuchus, most teleosaurids, and smaller individuals of Macrospondylus and ...
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Throughout the Jurassic, a plethora of marine reptiles dominated ocean waters, including ichthyosaurs, plesiosaurs and thalattosuchian crocodylomorphs. These Jurassic ecosystems were characterized by high niche partitioning and spatial variation in dietary ecology. However, while the ecological diversity of many marine reptile lineages is well known, the overall ecological diversification of Teleosauroidea (one of the two major groups within thalattosuchian crocodylomorphs) has never been explored. Teleosauroids were previously deemed to have a morphologically conservative body plan; however, they were in actuality morphofunctionally more diverse than previously thought. Here we investigate the ecology and feeding specializations of teleosauroids, using morphological and functional cranio‐dental characteristics. We assembled the most comprehensive dataset to date of teleosauroid taxa (approximately 20 species) and ran a series of principal component analyses (PC) to categorize them into various feeding ecomorphotypes based on 17 dental characteristics (38 specimens) and 16 functionally significant mandibular characters (18 specimens). The results were examined in conjunction with a comprehensive thalattosuchian phylogeny (153 taxa and 502 characters) to evaluate macroevolutionary patterns and significant ecological shifts. Machimosaurids display a well‐developed ecological shift from: (1) slender, pointed tooth apices and an elongate gracile mandible; to (2) more robust, pointed teeth with a slightly deeper mandible; and finally, (3) rounded teeth and a deep‐set, shortened mandible with enlarged musculature. Overall, there is limited mandibular functional variability in teleosaurids and machimosaurids, despite differing cranial morphologies and habitat preferences in certain taxa. This suggests a narrow feeding ecological divide between teleosaurids and machimosaurids. Resource partitioning was primarily related to snout and skull length as well as habitat; only twice did teleosauroids manage to make a major evolutionary leap to feed distinctly differently, with only the derived machimosaurines successfully radiating into new feeding ecologies. An investigation into teleosauroid functional morphology and ecological diversification. Using dental and mandibular characteristics, results suggest that teleosauroids displayed limited mandibular functional variability, aside from certain subgroups which exploited larger/harder prey items.
... Devils are scavengers that regularly consume hard bone and employ a range of prey-processing techniques that expose their teeth to unpredictable loads [40,[58][59][60]. In addition to having the highest predicted bite force of any extant mammal when scaled for body size [61], Van Valkenburgh & Ruff [4] also proposed that the relatively circular cross-sections of hyaenas were an adaptation to scavenging, and our observations of devil canines support this. ...
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Canine teeth are vital to carnivore feeding ecology, facilitating behaviours related to prey capture and consumption. Forms vary with specific feeding ecologies; however, the biomechanics that drive these relationships have not been comprehensively investigated. Using a combination of beam theory analysis (BTA) and finite-element analysis (FEA) we assessed how aspects of canine shape impact tooth stress, relating this to feeding ecology. The degree of tooth lateral compression influenced tolerance of multidirectional loads, whereby canines with more circular cross-sections experienced similar maximum stresses under pulling and shaking loads, while more ellipsoid canines experienced higher stresses under shaking loads. Robusticity impacted a tooth's ability to tolerate stress and appears to be related to prey materials. Robust canines experience lower stresses and are found in carnivores regularly encountering hard foods. Slender canines experience higher stresses and are associated with carnivores biting into muscle and flesh. Curvature did not correlate with tooth stress; however, it did impact bending during biting. Our simulations help identify scenarios where canine forms are likely to break and pinpoint areas where this breakage may occur. These patterns demonstrate how canine shape relates to tolerating the stresses experienced when killing and feeding, revealing some of the form–function relationships that underpin mammalian carnivore ecologies.
... Hogue (2008) found that marsupial folivores show an increase in the vertical bending strength of the mandibular corpus, as described for primates (e.g., Anapol and Lee 1994;Daegling 1992;Anton 1996). The mandibular morphology of carnivorous marsupials shows characters aimed at an improvement in the mechanical advantages in the bite system, convergent with that of carnivorans among placentals (e.g., Wroe et al. 2005;Wroe and Milne 2007;Prevosti et al. 2012; see above). However, despite the strong morphological differences in the great diversity of living marsupials, jaw growth patterns are conservative (Table 2). ...
Researchers have sought to infer the relationships between animal form and function for centuries. The study of biomechanics has become an increasingly important tool with which to quantify such relationships. Together analyses of shape and biomechanics can greatly inform our understanding of how animals interact with their environments and allow us to predict ecology in extinct species. They can also provide a sound basis from which we can gain insight into broader macroevolutionary processes. Because the acquisition and processing of food is clearly key to survival, the vertebrate feeding apparatus has received particular attention. Although clearly far less speciose than placental mammals, marsupials, and the broader metatherian clade to which they belong, are characterized by a long fossil history and considerable diversity. Consequently, they have been of critical importance in the study of evolutionary convergence. Assessments of convergence with placentals and predictions of feeding behavior in extinct species, such as the Thylacine (Thylacinus cynocephalus), Marsupial Lion (Thylacoleo carnifex), and the metatherian sabertooth (Thylacosmilus atrox), have generated particularly long-run controversy and debate. Here the study of form, function, and biomechanics in the feeding ecology of marsupials is reviewed, from nineteenth-century observation-based inference, through increasingly quantitatively founded studies incorporating two-dimensional shape analysis, lever mechanics, and beam theory in the twentieth century, to increasingly sophisticated recent investigations based on finite element analysis and three-dimensional morphometrics.
Muscle is a complex tissue that has been studied on numerous hierarchical levels: from gross descriptions of muscle organization to cellular analyses of fiber profiles. In the middle of this space between organismal and cellular biology lies muscle architecture, the level at which functional correlations between a muscle's internal fiber organization and contractile abilities are explored. In this review, we summarize this relationship, detail recent advances in our understanding of this form-function paradigm, and highlight the role played by The Anatomical Record in advancing our understanding of functional morphology within muscle over the past two decades. In so doing, we honor the legacy of Editor-in-Chief Kurt Albertine, whose stewardship of the journal from 2006 through 2020 oversaw the flourishing of myological research, including numerous special issues dedicated to exploring the behavioral correlates of myology across diverse taxa. This legacy has seen the The Anatomical Record establish itself as a preeminent source of myological research, and a true leader within the field of comparative anatomy and functional morphology.
The aim of this chapter is to discuss the evolution of the shape of the sacroiliac joint in two carnivoran lineages (Felidae and Canidae) and their large prey (Ungulata) in the context of divergent and convergent evolution. The significant difference in the angle between the iliac wings of the pelvic girdle in the transverse plane (the interiliac angle) between the Ungulata (>100°) and both carnivoran lineages (30–40°) suggests a divergence in form that relates to the evolution of their feeding behavior over at least 75 Myrs. In the Canidae, the interiliac angle of around 40° and the inner C-shape of the iliac auricular surface congruent with the sacral auricular surface are not influenced either by locomotor nor predatory behavior. Hunting on small or large prey has had no impact on the sacroiliac joint of canids, even though solitary hunting of small prey switches to pack hunting of big prey. A hunting strategy based upon the harassment of large prey individuals could explain why the locking properties of the sacroiliac joint, determined by the interiliac angle, and the inner shape of the articular surface have not been influenced by prey selection. These joint properties are similar to those of felids that select prey with body-mass lower than their own. We suggest that the similarities recorded in canids and these felids result from convergent evolution due to prey selection even though their hunting strategies are different. In contrast, the interiliac angle is significantly smaller, and the locking properties of the joint are increased through a strong congruency of the W-shaped inner surface and the outer ridge in solitary big cats that are able to exploit prey with body mass greater than their own, These traits, resulting in a stiff sacroiliac joint, especially during recoil, are probably explained by attributes of the feeding behavior that require a sustained bite during the killing of prey. In lions, the interiliac angle is similar to that of canids, suggesting a relaxation of functional constraints relating to feeding behavior in a species in which individuals organize into social groups for pack-hunting of large prey. This chapter considers the role of divergent and convergent functional evolution of feeding strategies on the morphological traits of the sacroiliac joint that permit us to discuss the “form-function” relationship of this key articulation of the pelvic girdle in the Carnivora.
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Eurypterids (sea scorpions) are extinct aquatic chelicerates. Within this group, members of Pterygotidae represent some of the largest known marine arthropods. Representatives of this family all have hypertrophied, anteriorly-directed chelicerae and are commonly considered Silurian and Devonian apex predators. Despite a long history of research interest in these appendages, pterygotids have been subject to limited biomechanical investigation. Here, we present finite element analysis (FEA) models of four different pterygotid chelicerae-those of Acutiramus bohemicus, Erettopterus bilobus, Jaekelopterus rhenaniae, and Pterygotus anglicus-informed through muscle data and finite element models (FEMs) of chelae from 16 extant scorpion taxa. We find that Er. bilobus and Pt. anglicus have comparable stress patterns to modern scorpions, suggesting a generalised diet that probably included other eurypterids and, in the Devonian species, armoured fishes, as indicated by co-occurring fauna. Acutiramus bohemicus is markedly different, with the stress being concentrated in the proximal free ramus and the serrated denticles. This indicates a morphology better suited for targeting softer prey. Jaekelopterus rhenaniae exhibits much lower stress across the entire model. This, combined with an extremely large body size, suggests that the species likely fed on larger and harder prey, including heavily armoured fishes. The range of cheliceral morphologies and stress patterns within Pterygotidae demonstrate that members of this family had variable diets, with only the most derived species likely to feed on armoured prey, such as placoderms. Indeed, increased sizes of these forms throughout the mid-Palaeozoic may represent an 'arms race' between eurypterids and armoured fishes, with Devonian pterygotids adapting to the rapid diversification of placoderms.
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It has been suggested that the large theropod dinosaur Tyrannosaurus rex was capable of producing extremely powerful bite forces and resisting multi-directional loading generated during feeding. Contrary to this suggestion is the observation that the cranium is composed of often loosely articulated facial bones, although these bones may have performed a shock-absorption role. The structural analysis technique finite element analysis (FEA) is employed here to investigate the functional morphology and cranial mechanics of the T. rex skull. In particular, I test whether the skull is optimized for the resistance of large bi-directional feeding loads, whether mobile joints are adapted for the localized resistance of feeding-induced stress and strain, and whether mobile joints act to weaken or strengthen the skull overall. The results demonstrate that the cranium is equally adapted to resist biting or tearing forces and therefore the 'puncture-pull' feeding hypothesis is well supported. Finite-element-generated stress-strain patterns are consistent with T. rex cranial morphology: the maxilla-jugal suture provides a tensile shock-absorbing function that reduces localized tension yet 'weakens' the skull overall. Furthermore, peak compressive and shear stresses localize in the nasals rather than the fronto-parietal region as seen in Allosaurus, offering a reason why robusticity is commonplace in tyrannosaurid nasals.
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Borophaginae is the largest of the three subfamilies of the dog family Canidae, with some 66 species, spanning approximately 34 m.y. (Orellan to Blancan). Not surprisingly, this extensive radiation of canids includes a diverse array of dietary types, ranging from hypocarnivorous to hypercarnivorous and durophagous. The last 16 m.y. of borophagine history is dominated by hypercarnivorous forms that were the dominant doglike predators within their faunas. Because of their relatively robust skeletons and their resemblance to extant hyenas in craniodental morphology, many or most of these hypercarnivorous species, particularly those of the late Miocene and Pliocene, have been assumed as primarily scavengers rather than hunters. The classification of most hypercarnivorous borophagines as scavengers relegates them to much less important roles in the ecology and evolution of their respective communities than does a classification as hunters. Unlike hunters, scavengers are unlikely to influence the evolution of the animals they eat, and are expected to exist at relatively low densities as do the only extant scavenging carnivorans, brown (Parahyaena brunnea) and striped hyenas (Hyaena hyaena). Given the substantial fossil record of the Borophaginae, it seems unlikely that all or most of the hypercarnivorous forms were primarily scavengers. Moreover, if some hunted, the larger species might be expected to have done so in groups, as large canids hunt in packs today. Here we examine possible foraging modes within the Borophaginae using morphometrics and two new approaches to estimating the typical prey size of extinct carnivores. The craniodental morphology of the Borophaginae is compared with that of the living Caninae and Hyaeninae (hyaenids exclusive of Proteles cristata, the aardwolf) based on measurements that reflect relative tooth size, jaw muscle leverage, rigidity of the dentary, and grinding versus slicing function of the teeth. The Borophaginae are found to be intermediate in morphology between the Caninae and Hyaeninae. Unlike hyaenids and like canines, they retain substantial postcarnassial molars. However, like hyaenids, the borophagines had significantly stronger jaws and enhanced jaw muscle leverage compared to other canids. Prey size is estimated for borophagines based on correlation between dentary height and typical prey size in living canids. These results are compared with those produced using a recently published energetic model that predicts that all carnivores larger than about 21 kg feed on prey as large or larger than themselves. The methods provide similar predictions, resulting in a list of 11 borophagines (all subtribes Aelurodontina and Borophagina) that probably consumed large prey. Comparisons with extant hyaenids reveal that the sole hunter of large prey, the spotted hyena (Crocuta), differs from the two mainly scavenging species, the brown and striped hyenas, in being significantly larger, more abundant, and widespread. Moreover, morphometric comparisons indicate that spotted hyenas have a more hypercarnivorous dentition. Given this, it is expected that the largest, most common borophagines with the most reduced dental grinding areas hunted most of their food. Based on their craniodental morphology and abundance in the record, Epicyon saevus, E. haydeni, Borophagus secundus, Aelurodon ferox, and A. taxoides were hunters. Although it is clear that Aelurodon and Borophagus were more capable of grasping prey than are extant canids, no borophagine evolved sharp, curved claws as in felids. Consequently, their ability to grapple with prey seems to have been limited, and packs were probably more successful at making a kill than individuals. Previous workers have argued against hunting in borophagines based on heavy dental wear, robust skeletal morphology, and external brain features. None of these precludes either hunting or hunting in packs in our view, and sharp teeth are not required for making a kill. While limb morphology and skeletal proportions of most or all borophagines do not appear adapted for the kind of hunts observed today in the African wild dog Lycaon pictus, long-distance, high-speed pursuits over shorter distances would have been possible for borophagines. The association between external brain morphology and social behavior in living carnivorans has not been fully explored, and seems a weak criterion for sociality in extinct species.
Predators with Pouches provides a unique synthesis of current knowledge of the world’s carnivorous marsupials—from Patagonia to New Guinea and North America to Tasmania. Written by 63 experts in each field, the book covers a comprehensive range of disciplines including evolution and systematics, reproductive biology, physiology, ecology, behaviour and conservation. Predators with Pouches reveals the relationships between the American didelphids and the Australian dasyurids, and explores the role of the marsupial fauna in the mammal community. It introduces the geologically oldest marsupials, from the Americas, and examines the fall from former diversity of the larger marsupial carnivores and their convergent evolution with placental forms. The book covers all aspects of carnivorous marsupials, including interesting features of life history, their unique reproduction, the physiological basis for early senescence in semelparous dasyurids, sex ratio variation and juvenile dispersal. It looks at gradients in nutrition—from omnivory to insectivory to carnivory—as well as distributional ecology, social structure and conservation dilemmas.
The borophagine canids were bone-cracking scavengers in the Miocene-Pleistocene of North America. In this they parallel the Recent hyenas. This paper analyzes the borophagine adaptation in relation to that of hyaenids, using Osteoborus cyonoides as an example. The emphasis during canid evolution on the posterior molars, which is a derived condition, created a constraint on the adaptation of borophagines. This constraint meant that the borophagines used P4/4 as bone-cracking teeth, whereas hyaenids use P3/3. Other than the evolution of a specialized bone-cracking tooth, the borophagines adapted to bone cracking by evolving a vaulted and strengthened skull for the dissipation of the strong forces generated during bone cracking. -from Author
The feeding behavior of the theropod dinosaur Tyrannosaurus rex is investigated through analysis of two variables that are critical to successful predation, bite force and prey body mass, as they scale with the size of the predator. These size-related variables have important deterministic effects on the predator's feeding strategy, through their effects on lethal capacity and choice of prey. Bite force data compiled for extant predators (crocodylians, carnivorans, chelonians and squamates) are used to establish a relationship between bite force and body mass among extant predators. These data are used to estimate the maximum potential bite force of T. rex, which is between about 183,000 and 235,000 N for a bilateral bite. The relationship between maximum prey body mass and predator body mass among the same living vertebrates is used to infer the likely maximum size of prey taken by T. rex in the Late Cretaceous. This makes it possible to arrive at a more rigorous assessment of the role of T. rex as an active predator and/or scavenger than has hitherto been possible. The results of this analysis show that adult Triceratops horridus fall well within the size range of potential prey that are predicted to be available to a solitary, predaceous T. rex. This analysis establishes boundary conditions for possible predator/prey relationships among other dinosaurs, as well as between these two taxa.
The morphology of the cervical vertebrae and skull structures associated with the neck musculature was studied in the felid sabertooth Homotherium latidens from the Spanish early Pleistocene site of Incarcal. Cervical anatomy of Homotherium was compared to that of modern pantherine cats, Smilodon, and other sabertoothed carnivores, and the relationship between neck function and killing behavior was investigated. Homotherium latidens possesses the structures associated with the canine shear-bite, as described in Smilodon. Our study of muscle insertion areas in the cervical vertebrae of Homotherium does not support previous statements about unusually strong scalenes and their role in stabbing. Instead, we see evidence of increased muscular control of various movements of the neck, including lateral flexion, depression and extension. These features, and the greater relative length of the neck in Homotherium and other machairodonts, are interpreted as adaptations for delivering a canine shear-bite in precise areas of the body of relatively large prey.