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Experimental paleontology of the scimitar-tooth and dirk-tooth killing bites

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... The identification of the tooth fragments was reliant predominately upon Rawn-Schatzinger (1983, 1992, although several other sources (Antón et al. 2014;Biknevicius et al. 1996;Cope 1893;Martin et al. 2011aMartin et al. , 2011bMartin et al. , 2011cMartin et al. , 2011dWheeler 2011) and some comparisons to modern Felidae taxa (Felis concolor, Lynx canadensis, and Leopardus pardalis, Department of Anthropology and Archaeology, University of Calgary) were also utilized. ...
... The term finely serrate as used by Cope (1893) and Churcher (1966) refers to "the consistent and regular serration of H. serum's teeth" (Rawn-Schatzinger 1992). Within this specimen, serrations are most clearly pronounced on the upper canines ( Fig. 4), upon which they are present along the entire length of the anterior and posterior edges (Rawn-Schatzinger 1983, 1992Wheeler 2011). ...
... This corresponds with descriptions by Rawn-Schatzinger (1983, 1992 of H. serum upper canines, which are laterally compressed or flat as compared to conicaltooth cats. Also unique to Homotherium, and exhibited in this specimen, is that the canines are relatively short and broad in comparison to other saber-tooths (Martin et al. 2011a;Martin et al. 2011d;Wheeler 2011) and are more complex on their lingual surface (Rawn-Schatzinger 1983). Both teeth are relatively straight with a very slight posterior curvature. ...
Article
Skull and tooth fragments of Homotherium serum recently recovered from the Wally’s Beach site (DhPg-8) in southwestern Alberta provide the first indications that scimitar cat populated the area of the St. Mary Reservoir. Accelerator mass spectrometry radiocarbon dating provides a calibrated age (2σ) of 12 715 – 12 655 cal. years BP. This is the fourth known occurrence of the species in Canada, the first outside of Yukon, and currently the youngest precisely dated occurrence of the species in North America. Well-preserved dentition combined with the temporal and geographic context allows the sample to be identified as H. serum. The specimen is significant as it represents an extension of the geographic and chronological range of the species.
... obliquus capitis posterior [20,22]. Although Akersten originally positioned the strike on the abdomen of the prey, the currently accepted location is the prey's ventral neck, where the maxillary canines are hypothesized to cut the carotid, resulting in exsanguination of the prey [11,23,25,26,39]. ...
... In the proposed Class 1 Lever Model, the cat restrains the prey on the ground using a variation of the bulldogging model [ Fig. 5A] [13,44]. Wrestling the prey down to its side [39], the cat forces the prey's head into a laterally rotated position (rotated upward from the ground) ( [10]; Fig. 7). The cat then maintains the hold by using the force of its body to press the buccal aspect of its abducted mandible into the side of the prey's upturned throat. ...
... Small serrations along the edges of the teeth [20,56] may have helped to expand the point of entry as the teeth descended into the tissue [13,56,59]. Although the manner of death for the canine shear-bite, in which the maxillary canines cut the carotid, exsanguinating the prey [3,8,10,16,21,22,25,39,60], is vivid and intuitively satisfying, it is impractical to expect the dull edges of these teeth [20,39,56] to cut through the tough, fracture-resistant hide and connective tissue [39,[61][62][63] of the prey's neck. The use of the S. fatalis maxillary canines in this highly traumatic manner is contradicted by the lack of microwear features found on the teeth [56]. ...
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The jaw function of Smilodon fatalis has long been a source of debate. Although modern-day lions subdue large prey through the use of a suffocating throat bite, the dramatically elongated maxillary canines of S. fatalis suggest an alternative bite mechanism. The current literature favors a "canine shear-bite," in which the depression of the cranium by the ventral neck flexors assists the mandibular adductors in closing the jaws. Although the model makes intuitive sense and appears to be supported by scientific data, the mechanical feasibility of "neck-powered" biting has not been experimentally demonstrated. In the present study, the computer-assisted manipulation of digitized images of a high-quality replica of an S. fatalis neck and skull shows that a rotation of the cranium by the ventral neck flexors will not result in jaw closure. Instead, the cranium and mandible rotate ventrally together (at the atlantooccipital joint), and the jaws remain in an open configuration. The only manner by which rotation of the cranium can simultaneously result in jaw closure is by an anterior rotation at the temporomandibular joint. Based on this finding, the author proposes a new Class 1 lever mechanism for S. fatalis jaw function. In this model, the mandible is immobilized against the neck of the prey and a dorsally directed force from the extension of the forelimbs rotates the cranium anteriorly at the temporomandibular joint. The maxillary canines pierce the prey's neck and assist in clamping the ventral neck structures. The model is based on a maximum gape angle of approximately 90° and incorporates a secondary virtual point of rotation located slightly anteroventral to the temporomandibular joint. The Class 1 Lever Model is mechanically feasible, consistent with current data on S. fatalis anatomy and ecology, and may provide a basis for similar studies on other fossil taxa.
... One potential reason for the rarity of metatherian sabertooth lineages may be related to how their distinctive upper canines may have functioned. It has been argued that saber teeth would have required a considerable learning period to be used effectively (Emerson and Radinsky, 1980;Akersten, 1985;Antón and Galobart, 1999;Wheeler, 2011). Functional modeling of saber bites has shown that an imprecise bite can cause the canines to snag, can easily be be too shallow to be lethal, or can penetrate too deeply to be extracted from the prey (Wheeler, 2011). ...
... It has been argued that saber teeth would have required a considerable learning period to be used effectively (Emerson and Radinsky, 1980;Akersten, 1985;Antón and Galobart, 1999;Wheeler, 2011). Functional modeling of saber bites has shown that an imprecise bite can cause the canines to snag, can easily be be too shallow to be lethal, or can penetrate too deeply to be extracted from the prey (Wheeler, 2011). Elongate, labiolingually narrow upper canines are also vulnerable to breakage when subjected to sudden, unpredictable loads such as those produced by struggling prey (Van Valkenburgh and Ruff, 1987). ...
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Thylacosmiline sparassodonts (previously recognized as thylacosmilids) are among the most iconic groups of endemic South American Cenozoic mammals due to their distinctive morphology and convergent resemblance to saber-toothed placental carnivores. However, the early evolution of this group and its relationship to other sparassodonts remains poorly understood, primarily because only highly specialized Neogene taxa such as Thylacosmilus, Anachlysictis, and Patagosmilus are well known. Here, we describe a new Paleogene sparassodont, Eomakhaira molossus, from the Cachapoal locality of central Chile, the first sparassodont reported from early Oligocene strata of the Abanico Formation. Eomakhaira shares features with both Neogene thylacosmilines and Paleogene “proborhyaenids,” and phylogenetic analyses recover this taxon as sister to the clade of Patagosmilus + Thylacosmilus. This broader clade, in turn, is nested within the group conventionally termed Proborhyaenidae. Our analyses support prior hypotheses of a close relationship between thylacosmilines and traditionally recognized proborhyaenids and provide the strongest evidence to date that thylacosmilines are proborhyaenids (i.e, the latter name as conventionally used refers to a paraphyletic group). To reflect the internestedness of these taxa, we propose use of Riggs' (1933) original name Thylacosmilinae for the less inclusive grouping and Proborhyaenidae for the more inclusive one. Saber teeth arose just once among metatherians (among thylacosmilines), perhaps reflecting a developmental constraint related to nonreplacement of canines in metatherians; hypselodonty may have relaxed this potential constraint in thylacosmilines. The occurrence of Eomakhaira in strata of early Oligocene age from the Chilean Andes demonstrates that the stratigraphic range of thylacosmilines spanned almost 30 million years, far surpassing those of saber-toothed placental lineages.
... Conical canines are highly advantageous for ambush predators, because they can more easily withstand the highly erratic bending and torsional forces created by struggling prey (Meachen-Samuels and Van Valkenburgh, 2009). Predators with mediolaterally compressed canines, on the other hand, tend to favor hunting strategies that involve a minimal amount of contact between the prey and canine teeth, such as a series of shallow, slashing bites while chasing down prey (like macropredatory hyenas and dogs; see Van Valkenburgh and Ruff, 1987) or a single, highly precise throat bite (like sabertooth taxa; see Akersten, 1985;Andersson et al., 2011;Wheeler, 2011). ...
... Other morphological features of UF 27881 may be related to the large canines of this taxon. For example, the small foramina covering the surface of the canine alveolus might be evidence of an extensive mucoperiosteum and enlarged gingivae, similar to what has been proposed for nimravids (Wheeler, 2011) and the machairodontine felid Smilodon (Riviere and Wheeler, 2005). This interpretation is supported by the presence of small maxillary foramina in the sparassodonts Thylacosmilus, Patagosmilus, and Arminiheringia, which also have hypertrophied canines (see above). ...
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The Sparassodonta (Mammalia, Metatheria) are a group of carnivorous mammals that dominated the macropredatory guild of South America during the Cenozoic. Here, we describe a new sparassodont based on a single specimen from the middle Miocene Quebrada Honda local fauna of southern Bolivia. This specimen (UF 27881) does not clearly correspond to any major sparassodont group (e.g., Hathliacynidae, Borhyaenidae, etc.) and represents a morphotype previously unknown among the Sparassodonta. UF 27881 is distinguished from other sparassodonts by its short, broad, borhyaenid-like rostrum and small size, among other features. However, we decline to coin a new name for UF 27881 due to the fragmentary nature of this specimen and the absence of most of its dentition. This specimen suggests that the appearance of the Sparassocynidae and several hypercarnivorous didelphid taxa (including Thylophorops, Thylatheridium, Lutreolina, and Hyperdidelphys) represent an evolutionary response to the decline in small, predatory sparassodont taxa during the late Cenozoic. This study documents new morphological diversity among the Sparassodonta and highlights the value of fossils from traditionally undersampled parts of South America.SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at http://www.tandfonline.com/UJVP.
... Isotopic data from Beringia (Fox-Dobbs et al. 2008) and Rancho la Brea (Coltrain et al. 2004) suggest that H. serum diets were relatively generalized with regard to available large fauna. This is supported by reconstructions of H. serum bite behaviour (Wheeler 2011). Isotopic work hints that prey-choice in large felids may be strongly affected by other carnivores, especially large bears (Fox-Dobbs et al. 2008; Bocherens et al. 2011). ...
... Isotopic data from Beringia ( Fox-Dobbs et al. 2008) and Rancho la Brea ( Coltrain et al. 2004) suggest that H. serum diets were relatively generalized with regard to available large fauna. This is supported by reconstructions of H. serum bite behaviour ( Wheeler 2011). Isotopic work hints that prey-choice in large felids may be strongly affected by other carnivores, especially large bears ( Fox-Dobbs et al. 2008;Bocherens et al. 2011). ...
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A scimitar-toothed cat (Homotherium serum) and stag moose (Cervalces sp.) are described from Tyson Spring Cave, Fillmore County, Minnesota. These specimens represent the first records of both species in the state, and the first record for H. serum in the Great Lakes region. Although the Cervalces specimen remains undated, it shares features with pre-Wisconsin specimens from the eastern Great Plains. The H. serum individual dates to c. 26.9 ka, when the Wisconsin ice margin was less than 60 km away. Genetic analyses support the identity of the Homotherium specimen as conspecific with Homotherium serum found in older Beringian deposits, as well as both the early divergence of tribes Homotherini and Smilodontini within Machairodontinae and the early divergence of this Machairodontinae from the lineage that produced extant cats.
... Robocat's construction and use has been previously described in detail (Wheeler, 2011). This machine was attached to a Bobcat X-331 hydraulic trackhoe. ...
Chapter
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Introduction Among the various theories presented for the killing bite technique of the iconic hypercarnivore sabertooth cat, Smilodon, one is so comprehensive as to constitute a testable hypothesis, the canine shear-bite (Akersten, 1985). This chapter takes a different approach to this question, as an engineering experiment based on the morphology of the skull, upper canine, and mandible. I use a fabricated mechanical attachment based on casts of the upper and lower dentition of Smilodon from Rancho La Brea to measure the force required to bite a suitable prey proxy, using any desired sequence conforming to a chosen bite model. Discretion is required because, limited only by the original geometry, the device can easily exceed the force of the original and do the impossible. In this experiment Bison bison bison is used as a proxy for B. bison antiquus. Bison bison antiquus is the most abundant large herbivore at Rancho La Brea, and Coltrain et al. (2004) demonstrated that bison was one of the primary prey species for both and Panthera atrox at Rancho La Brea. Since both cats shared the same prey base the smaller size of Smilodon might suggest that it was a more efficient predator. The Rancho La Brea collection facilitated the experiment by providing an abundant, accessible sample of Smilodon from which to select representative individuals. Smilodon (referred to variously as S. fatalis, S. floridanus, and S. californicus) has been the primary taxon used to study canine function in sabertooth cats, and the leading work on the subject has been described with sufficient detail to present a testable hypothesis. The model tested has been labeled the canine shear-bite (Akersten, 1985). Using that work for the given conditions, a machine was constructed to the dimensions and parameters of the skull, mandible, and canines of Smilodon, capable of replicating any proposed biting action, using sabers of the same size and shape as those in Smilodon. Using the bite model theories proposed to reproduce saber movement through cadavers permitted the forces required to pierce the skin and determine the resultant injury by necropsy. This permitted the required force to be determined experimentally. Bites targeting both throat and abdomen were evaluated. Freeman and Lemen, (2007) also determined canine strength experimentally. The approach used by others, such as McHenry et al. (2007), has used sophisticated FEA analysis to determine the strength of the skull, but relies on the assumption that the bite theory is correct, and the available force is adequate. We found this was not the case. Our objective to verify this theory experimentally under real world conditions, would require that the necessary force required be a comfortable margin of safety less than that of the tooth strength. This chapter summarizes my observations based on the experimental mechanical device constructed. In addition, a summary of my observations on wear found on the upper canine is presented. My conclusion is that overall the canine shear-bite model proposed by Akersten (1985) is unworkable. It still remains the best study of the subject, however, and many insights presented in that paper are remarkably accurate. It was immediately obvious that we know a lot more about the fossil (and extant) cats than we do about the properties, elasticity, and strength of the prey and their soft tissues. The basic unanticipated experimental observation entails the extreme distortion of prey tissues as bite force is applied and the independent movement of hide and subcutaneous structures. In order to be successful, the sabertooth cat killing bite has to fatally injure an animal that is (figuratively) within an armor-like leather bag.
... One particular aspect of the paleobiology of the sabretooth cat Smilodon has received a high level of attention, i.e. the killing mechanism of this predator without analog in the modern world (e.g. Warren, 1853;Simpson, 1941;Akersten, 1985;Therrien, 2005;McHenry et al., 2007;Andersson et al., 2011;Wheeler, 2011;Wilson et al., 2013;Wroe et al., 2013;Brown, 2014). It must be kept in mind that most of these studies deal with the species S. fatalis, not with S. populator, the main species in South America, although numerous studies included S. populator recently (Christiansen 2008;Slater and Van Valkenburgh 2008;Prevosti and Vizcaíno, 2006;Prevosti et al. 2010;Prevosti and Martin, 2013). ...
Article
The Neogene Amphimachairodus coloradensis appears to be one of the most abundant species of Machairodontine in Mexico. However, its fossil record is composed of scarce, fragmented, and poorly studied material. New remains discovered in La Plegaria locality (late Hemphillian), in the State of Hidalgo, in Central Mexico, offers the opportunity to review some morphological aspects and phylogenetic relationships of this species within the subfamily Machairodontinae. Our observations allow us to recognize that the material from La Plegaria looks like the paratype of A. coloradensis (DMNH EPV 207, from the Ogallala Fm. in the western United States); this means, m1 with reduced talonid and paraconid almost as large as protoconid, and p4 with posterior cingulum. Phylogenetic analysis confirms the relationship of La Plegaria felid with A. coloradensis and A. alvarezi; although the last one presents autapomorphies that differentiate it from others Amphimachairodus: highly developed mandibular flange. We concluded that the material from La Plegaria corresponds to the southernmost record of an A. coloradensis. This work made it possible to review variation within this species and its morphological relationship with M. catocopis.
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In this field there has been an explosion of information generated by scientific research. One of the beneficiaries of this has been the study of morphology, where new techniques and analyses have led to insights into a wide range of topics. Advances in genetics, histology, microstructure, biomechanics and morphometrics have allowed researchers to view teeth from alternative perspectives. However, there has been little communication between researchers in the different fields of dental research. This book brings together overviews on a wide range of dental topics linking genes, molecules and developmental mechanisms within an evolutionary framework. Written by the leading experts in the field, this book will stimulate co-operative research in fields as diverse as paleontology, molecular biology, developmental biology and functional morphology.
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"Machairodus catocopis Cope" is shown to be a pseudaelurin cat belonging to the genus Nimravides Kitts. Nimravides thinobates (Macdonald) is a possible synonym of N. catocopis (Cope). Nimravides is compared with the Eurasian Machairodus-like cat, Dinofelis. Machairodus (Heterofelis) coloradensis is reported from the Kimball Formation, upper Pliocene (Kimballian) of Cheyenne County, Nebraska, and from the upper part of the Ash Hollow Formation, Pliocene (Hemphillian) of Sherman County, Nebraska. The Kimballian form is described as a new subspecies, Machairodus coloradensis tanneri. The genus Machairodus has long been associated with the Hemphillian of North America and the Pontian of Eurasia. It was first reported from North America when Cope, in 1887, described a partial symphysis of a mandible from the Pliocene of Kansas as Machairodus catocopis. He did not illustrate this specimen, and it has largely been ignored (see Fig. 3, C and E in the present paper). The concept of the species has rather been based on abundant material from Ogallala deposits (Hemphillian) of Yuma County, Colorado, described by Cook (1922) as M. (Heterofelis) coloradensis; later Burt (1931) published additional records from the Hemphillian of Texas. Matthew (1924) placed M. coloradensis in synonomy with M. catocopis and this concept has generally been followed. New material from Smith County, Kansas, which is near the type locality and horizon of M. Catocopis, permits a reevaluation of that species and shows that it is a pseudaelurin cat, Nimravides. Machairodus coloradensis is reported from the Upper Ash Hollow deposits (Hemphillian) of Sherman County, Nebraska, and is compared to a new subspecies of Machairodus described in this paper from the Kimball (Kimballian) Formation of Cheyenne County, Nebraska. This new subspecies demonstrates evolutionary trends which seem to be leading to Ischyrosmilus from the lower Quaternary (Blancan). We do not regard the pseudaelurin cats to be of subfamily rank, although they probably should be placed in a separate tribe, Pseudaelurini, which represents primitive felines.
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The claw equipped forelimbs have been shown to be an important hunting weapon for modern felids. In light of its functional importance, the claw retractile mechanism for modern felids was compared with that of the saber-toothed felids. In this regard, the functional anatomy of claw retraction for saber-toothed felids was found to be the same as that of modern forms. Body proportions of modern felids were also compared with saber-toothed felids and the relationship of their morphology to habitat structure and habitat utilization were studied. It was found that the relative body proportions for Hoplophoneus and Smilodon were similar to modern forest felids (dwellers of high structured dense forest), while Dinictis and Machairodus could probably compete in more open terrain (open woodland, meadow). It is postulated that saber-toothed felids used their claw equipped forelimbs to grasp and hold their prey as do modern felids. In this fashion, the enlarged upper canines could then be used to kill the victim, and this was probably done by a stab to the nape of the neck. It is also thought that Smilodon, like the modern lion, adapted to open habitats by forming prides.
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A new genus of Pliocene Saber-toothed felid, Barbourofelis, is proposed and two new species B. fricki and B. morrisi are described. These two forms and other described material represent an unusual lineage of felids with long sabers, shortened crania, and massive postorbital bars. The tribal name Barbourofelini is proposed for this lineage which is presently known in North America from deposits ranging in age from Clarendonian through Kimballian. The Barbourofelini apparently migrated from Eurasia to North America in the Late Miocene or Early Pliocene. Sansanosmilus of the French Vindobonian appears to represent the ancestral stock of these cats. The following genera of other saber-toothed felids are discussed: Hoplophoneus, Eusmilus, Dinictis, Nimravus, Ekgmoiteptecela, Ma.chairodus, Ischyrosmilus, Homotherium, H. (Dinobastis), Megantereon, and Smilodon. The two generic names Albanosmilus and Grivasmilus also are considered. The continued usage of the provincial age terms Valentinian and Kimballian is recommended, and a faunal list for these units in Nebraska is provided.
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Three basic morpho types are proposed for cats on the basis of their upper canines: 1) conical-toothed cats with short, unserrated canines having a round cross-section; 2) scimitar-toothed cats having short, broad canines, usually with very coarse serrations; and 3) dirktoothed cats having long, slender canines which usually have fine serrations. Commonly all three morphotypes occur together in the same fauna. The method of prey capture was probably different for each morphotype. Both types of saber-toothed cats appear to have specialized on large prey, but it seems unlikely that they utilized the same prey. Scimitar-toothed cats are long-limbed, and were probably pursuit predators. Dirk-toothed cats are short-limbed and must have ambushed their prey. The separation of cats into two families, Nimravidae and Felidae, is accepted. Felid cats have a septum bullae in the auditory bulla and a cruciate sulcus on the brain. Nimravid cats generally lack complete bullae, and when they are present there is no septum. Nimravid cats also lack the cruciate sulcus on the brain.