Canis Dirus Research Articles

Mandibular shape correlates of tooth fracture in extant Carnivora: implications to inferring feeding behaviour of Pleistocene predators

Percentages of tooth fracture and mandible shape are robust predictors of feeding habits in Carnivora. If these parameters co-vary above the species level, more robust palaeobiological inferences could be made on fossil species. A test of association is presented between mandible shape and tooth fracture in a subset of extant carnivorans together with large Pleistocene fossil predators from Rancho La Brea (Canis dirus, Panthera atrox, and Smilodon fatalis). Partial least square (PLS) and comparative methods are employed to validate co-variation of these two parameters in extant carnivorans. Association between mandible shape and percentage of tooth fracture is strongly supported, even if both blocks of data exhibit a phylogenetic signal to a different degree. Dietary adaptations drive shape/fracture co-variation in extant species, although no significant differences occur in the PLS scores between carnivores and bone/hard food consumers. The fossil species project into PLS morphospace as outliers. Their position suggests a unique feeding behaviour. The increase in the size of prey, together with consumption of skin and hair from carcasses in a cold environment, might have generated unusual tooth breakage patterns in large predators from Rancho La Brea. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 106, 70–80.

The carnivoran fauna of Rancho La Brea: Average or aberrant?

The late Pleistocene asphalt seeps of Rancho La Brea are well-known for their impressive assemblage of carnivorans, which make up the vast majority of the preserved fauna. Of particular interest is the large number of dire wolf and sabertooth cat specimens. Carcass domination, the hypothesis that predators engaged in intense competition for trapped prey, may explain the mechanism of this predator trap. Large and social animals would have fared best during competition over carcasses, so the preponderance of Canis dirus and Smilodon fatalis has been seen as evidence of their sociality. However, no studies have quantitatively determined whether the relative carnivoran species abundances in Rancho La Brea differ significantly from those in California or North America at large. We compare numbers of identified specimens (NISP) from the Rancho La Brea fauna to regional and continental faunal data compiled from the FAUNMAP II database to test this hypothesis. Our results confirm that the carnivoran fauna in Rancho La Brea is unique, with preservation patterns generally supporting the carcass domination hypothesis as well as the sociality of S. fatalis.

Analysis of the upper forelimb of Canis dirus to determine physical characteristics that might suggest sociality

Canis dirus guildayi, or the Western Dire wolf, was the most common predator at Rancho La Brea and is believed to be social as are modern wolves. In this study, the upper forelimb, specifically the scapula, humerus, and ulna of C. dirus were examined. Maps determined from examination of ridges, rugosities and other features reflecting alteration of bone surfaces by muscle attachments were created. Interpretation of significance of muscle scars on these bones was made possible by comparison to dissections of the forelimb musculature of Canis latrans (American coyote) and Urocyon cinereagenteus (Red Fox). The dire wolf is considered a social predator, in part from previous studies that characterized specific healed or partially healed skeletal injuries that parallel those in social modern wolves hunting large prey in groups. Further support for sociality in Dire wolves that also specialized in capture of large prey is suggested by anteroposterior scapular lengthening in some larger individuals. This shape, surface area and muscle scar position allowed for a relatively larger origin of the M. serratus ventralis, a muscle that supports the trunk, assists with inspiration and moves the trunk and the scapular region anteroposteriorly. This capability would allow for increased anteroposterior movement of the limb, an advantage for a pursuit predator cursor hunting in cooperation with conspecifics to capture large prey.Grant Funding Source: Northern Illinois University

Morphometric pelvic muscle map analysis in extant and pleistocene carnivores

Recent studies in our laboratory have developed maps of pelvic musculature attachment sites (muscle maps) for Neofelis nebulosa (clouded leopard), Felis catis (domestic cat) and >Canis latrans (coyote). Correlations were made between actual muscle attachments and bone morphology at the attachment site. Based on this information we can map muscle attachment sites on bones from extinct closely related species. Pleistocene pelvis specimens were examined for bony muscle attachment sites, measured and photographed at the George C. Page Museum in Los Angeles, California. Specimens included Smilodon fatalis (n=9), Panthera atrox (n=4), Canis dirus (n=6), Canis latrans (n=5), and Arctodus simus (n=2). Muscle map surface areas for eight pelvic muscles were determined for each specimen along with pelvic measurements (ilium/ischium: width/length). The measurements were then compared between and within extant and extinct species listed above. Mm. gluteus medius, quadratus femoris, cranial and caudal gemellus surface areas differed significantly in comparisons between the felids, and between felids and non‐felid species in both extinct and extant groups. Pelvic measurements differed primarily between felid and non‐felids. These results suggest that muscle map surface area analysis may be useful for both phylogenetic and morphometric analysis.

Constraining the time of extinction of the South American fox Dusicyon avus (Carnivora, Canidae) during the late Holocene

A mass extinction affected South America during the late Pleistocene and early Holocene, when megamammals and large mammals disappeared. Several carnivores became extinct, including the sabretooth ( Smilodon), the short-faced bear ( Arctotherium), and some large canids ( i.e., Protocyon, Canis dirus). After this mass event, virtually no carnivores became extinct in South America. The only exception is the fox Dusicyon avus, a medium-sized canid (estimated body mass between 10 and 15 kg) with a more carnivorous diet than the living South American foxes ( Lycalopex culpaeus). The last record of the species comes from middle-late Holocene archaeological sites in the Pampean Region (Argentina) and Patagonia (Argentina and Chile). During the late Pleistocene, D. avus had a wide distribution, which covered part of Uruguay, Argentina (Buenos Aires province) and southern Patagonia. Although some remains from late Holocene sites have been published, these remains are still lacking numerical dating to determine the approximate date of extinction of this fox. This paper presents several new records from the Pampean and Patagonia regions, and several taxon dates. The new records indicate that D. avus survived in the late Holocene at least until ≈ 3000 BP in the Isla Grande de Tierra del Fuego (Patagonia) and the continent. Since at this time humans were occupying most of the Pampas and Patagonia, a revision of the causes behind the extinction of this fox is needed.

Phylogeny of the large extinct South American Canids (Mammalia, Carnivora, Canidae) using a "total evidence" approach.

South America currently possesses a high diversity of canids, comprising mainly small to medium-sized omnivorous species, but in the Pleistocene there were large hypercarnivorous taxa that were assigned to Protocyon spp., Theriodictis spp., Canis gezi, Canis nehringi and Canis dirus. These fossils have never been included in phylogenies based on quantitative cladistics, but hand-constructed cladograms published in the 1980s included some of them in the South American canine clade and others in the Canis clade. In this work, the phylogenetic position of the large extinct South American canids was studied using a large sample of living and extinct canids, as well as different sources of characters (e.g. DNA and 133 osteological characters). The phylogenetic analysis corroborates the inclusion of Theriodictis and Protocyon in the "South American clade", where C.gezi is also included. In addition, the position of C.dirus as a highly derived Canis species is confirmed. The simultaneous analysis supports hypercarnivory having arisen at least three times in Caninae and once in the "South American clade". The combination of the phylogenetic analyses, the fossil record and divergence dates estimated in previous works suggests that at least three or four independent lineages of the "South American clade" invaded South America after the establishment of the Panama bridge around 3 million years ago, plus other events corresponding to the immigration of Urocyon and Canis dirus. © The Willi Hennig Society 2009.

The Yucatan peninsula: biogeographical history 65 million years in the making

The fourth biennial meeting of the International Biogeography Society (IBS) in Merida, Yucatan in January 2009 represented a double opportunity for Mexican biologists. First, it fostered the integration of the large community of Mexican biogeographers with the activities of the IBS. Second, the meeting allowed us to welcome a large number of delegates from distant parts of the world who were able to visit what has been considered an obligate destination for nature lovers and cultural tourists alike: the Yucatan peninsula. As Edward O. Wilson pointed out, besides economic power every country has two additional and important types of wealth: cultural and natural. Cultural richness is a naturally embedded component of the Mexican way of life.

A comparison of tooth wear and breakage in Rancho La Brea sabertooth cats and dire wolves across time

ABSTRACT The carnivores preserved in the late Pleistocene Rancho La Brea tar seep deposits display a remarkably high incidence of teeth broken in life as compared with modern species. In a previous study examining tooth breakage, tooth wear and individual age of Canis dirus over different periods in time, we found that Pit 13 C. dirus (about 15,000 years before present [ybp]) exhibited heavier tooth wear and fractured their teeth about three times more often than those of the younger Pit 61/67 (about 12,000 ybp). No significant difference was found in the age structure of the population, suggesting this came from differences in feeding behavior, likely bone consumption, at these two times. In this study, we extend this work to the Rancho La Brea sabertooth cat, Smilodon fatalis, a hypercarnivore with more specialized teeth and feeding behavior. We looked at tooth breakage, tooth wear, and individual age of S. fatalis compared with C. dirus from similar time intervals. As in the previous study, the age structure of the Smilodon samples did not differ between different time intervals. Interestingly, S. fatalis had consistent and higher levels of tooth breakage and apparent average age than C. dirus in either location, and tooth wear was similar to that observed in the more worn Pit 13 sample of C. dirus. This may demonstrate that S. fatalis was consuming more bone, and/or that S. fatalis individuals were older, had different relative dentine deposition rates, or might reflect the greater vulnerability of the sabercats’ narrow teeth to wear and fracture.

Stratigraphic range of the large canids (Carnivora, Canidae) in South America, and its relevance to quaternary biostratigraphy

The fossil record of large canids is reviewed in order to improve the current South American biostratigraphic chart. This analysis is based on the recent systematic revision of those taxa performed by one of the authors and new field and paleomagnetic works. The first occurrences of large canids are limited to the Early–Middle Pleistocene (Ensenadan stage/age). Theriodictis platensis, “ Canis” gezi, and Protocyon scagliorum are restricted to the Ensenadan. Most T. platensis specimens came from late Ensenadan levels (0.78–≈0.5 Ma), but the oldest one is between 0.78 Ma and 1 Ma old. The biochron of Protocyon troglodytes spans the Ensenadan–Lujanian interval, and its youngest remains are associated with 14C dates of 25–27/20–10 ka BP. Most individuals of Protocyon tarijensis could be between 1 Ma and 10 ka, but one specimen comes from a level surely younger than 0.78 Ma, and probably younger than 28 ka. The oldest records of the living species Chrysocyon brachyurus are between ca. 0.3 Ma–9 ka BP. The first record of Canis dirus (and Canis by extension) in South America is limited to the latest Pleistocene (<25–27 ka).

Dire Wolf, Canis dirus (Mammalia; Carnivora; Canidae), from the Late Pleistocene (Rancholabrean) of East-Central Sonora, Mexico

Abstract We describe the first occurrence of the extinct dire wolf, Canis dirus, from the late Pleistocene deposits of east-central Sonora, Mexico. Remains include a partially complete left mandible and a left distal fragment of humerus collected from the deposits at Terapa. Local environments are interpreted to have been a tropical marsh with thorn-scrub to deciduous forest including some component of a nearby grassland. Although the mandible is nearer to the size of other large species of Canis known to occur in Mexico, the deep and robust mandible, presence of an accessory cuspid on the p2, an enlarged and robust p4, and accessory cuspids on the posterior margin of the trigonid ally the Canis from Terapa with C. dirus. Length of p4 suggests a possible closer affiliation to C. d. guildayi than to C. d. dirus.

Large extinct canids from the Pleistocene of Uruguay: systematic, biogeographic and paleoecological remarks

The fossil record of Canidae in South America begins in the Late Pliocene. During the Pleistocene large hypercarnivore canids (Theriodictis, Protocyon, Canis dirus) and also large species of Neotropical foxes (Dusicyon avus) evolved. Most fossil canids were found in Chile, Ecuador, Bolivia, Brazil, Venezuela and Argentina and are scarce or absent in other countries. From Uruguay only fossils referred to Dusicyon gymnocercus, ‘Pseudalopex’ and ‘Canis’ are currently known. We describe new records that belong to large canids from the Sopas Fm. (Late Pleistocene) of Uruguay and discuss their biogeographic and paleoecologic relevance. These specimens are referred to Protocyon troglodytes and D. avus by means of descriptive and multivariate analysis and constitute the first records of these taxa for Uruguay, expanding and completing their distribution in the Late Pleistocene of South America. Both species could have been occupied ‘niches’ not represented by the carnivores previously registered in the Sopas Fm. (Puma concolor, Panthera onca, Lontra longicaudis, etc.) suggesting more complex biotic interactions in the mammalian assemblages than previously assumed. The large hypercarnivorous canid P. troglodytes could hunt medium-large sized mammals, pursuing their prey in packs over long distances, while the medium canid D. avus could prey on small and middle mammals.

Parallels between playbacks and Pleistocene tar seeps suggest sociality in an extinct sabretooth cat,Smilodon

Inferences concerning the lives of extinct animals are difficult to obtain from the fossil record. Here we present a novel approach to the study of extinct carnivores, using a comparison between fossil records (n=3324) found in Late Pleistocene tar seeps at Rancho La Brea in North America and counts (n=4491) from playback experiments used to estimate carnivore abundance in Africa. Playbacks and tar seep deposits represent competitive, potentially dangerous encounters where multiple predators are lured by dying herbivores. Consequently, in both records predatory mammals and birds far outnumber herbivores. In playbacks, two large social species, lions, Panthera leo, and spotted hyenas, Crocuta crocuta, actively moved towards the sounds of distressed prey and made up 84 per cent of individuals attending. Small social species (jackals) were next most common and solitary species of all sizes were rare. In the La Brea record, two species dominated, the presumably social dire wolf Canis dirus (51%), and the sabretooth cat Smilodon fatalis (33%). As in the playbacks, a smaller social canid, the coyote Canis latrans, was third most common (8%), and known solitary species were rare (<4%). The predominance of Smilodon and other striking similarities between playbacks and the fossil record support the conclusion that Smilodon was social.

A NEW FOSSIL CANID ASSEMBLAGE FROM THE LATE PLEISTOCENE OF NORTHERN SOUTH AMERICA: THE CANIDS OF THE INCIARTE ASPHALT PIT (ZULIA, VENEZUELA), FOSSIL RECORD AND BIOGEOGRAPHY

Canids invaded South American during the Pliocene (2.8–3.1 Ma BP) as part of the Great American Biotic Interchange, but their record on the continent is relatively poor until the Pleistocene. However, even the Pleistocene record of the group is patchy and biased, with few records for the northern part of South America. In this paper we describe a new assemblage of canids found at the Inciarte asphalt pits (Zulia, Venezuela). These remains are associated with a variety of extinct Pleistocene mammals dated between 25–27 Ka BP. Canids in this assemblage include Protocyon troglodytes (Lund 1838), Protocyon sp., Canis dirus Leidy, 1858, Urocyon cf. U. cinereoargenteus (Schreber, 1775), and an indeterminate canid. This is the first record of Urocyon Baird, 1758 from the Late Pleistocene in South America and constrains the timing of its dispersal to South America. The distributional record of Protocyon Giebel, 1855 and P. troglodytes is expanded 1,500 km north of previous records and constitutes the first record of these taxa in Venezuela. The presence of C. dirus at Inciarte constitutes the fourth locality for this species in South America.

Stable isotopes, ecological integration and environmental change: wolves record atmospheric carbon isotope trend better than tree rings

Large-scale patterns of isotope ratios are detectable in the tissues of organisms, but the variability in these patterns often obscures detection of environmental trends. We show that plants and animals at lower trophic levels are relatively poor indicators of the temporal trend in atmospheric carbon isotope ratios (delta13C) when compared with animals at higher trophic levels. First, we tested how differences in atmospheric delta13C values were transferred across three trophic levels. Second, we compared contemporary delta13C trends (1961-2004) in atmospheric CO2 to delta13C patterns in a tree species (jack pine, Pinus banksiana), large herbivore (moose, Alces alces) and large carnivore (grey wolf, Canis lupus) from North America. Third, we compared palaeontological (approx. 30000 to 12000 14C years before present) atmospheric CO2 trends to delta13C patterns in a tree species (Pinus flexilis, Juniperus sp.), a megaherbivore (bison, Bison antiquus) and a large carnivore (dire wolf, Canis dirus) from the La Brea tar pits (southern California, USA) and Great Basin (western USA). Contrary to previous expectations, we found that the environmental isotope pattern is better represented with increasing trophic level. Our results indicate that museum specimens of large carnivores would best reflect large-scale spatial and temporal patterns of carbon isotopes in the palaeontological record because top predators can act as ecological integrators of environmental change.

Carnivore-specific stable isotope variables and variation in the foraging ecology of modern and ancient wolf populations: case studies from Isle Royale, Minnesota, and La Brea

We use carbon and nitrogen isotope data collected from two North American gray wolf ( Canis lupus L., 1758) populations (Isle Royale and northern Minnesota) to both calculate carnivore-specific isotopic variables and investigate wolf foraging ecology. The isotopic enrichments of13C and15N that occur between mammalian carnivores and their prey have not been well defined in modern populations. We use bone collagen from the Isle Royale National Park wolf, moose ( Alces alces (L., 1758)), and beaver ( Castor canadensis Kuhl, 1820) populations to determine trophic enrichment factors of 1.3‰ ± 0.6‰ for δ13C and 4.6‰ ± 0.7‰ for δ15N. We apply these carnivore-specific fractionation factors to a case study from the fossil record, and reconstruct the diets of late-Pleistocene dire wolves ( Canis dirus (Leidy, 1858)) from the La Brea tar pits. We use the Minnesota wolf tissue (collagen, hair, muscle) isotopic data to estimate carnivore population subsample sizes needed to replicate the mean values of the whole population within one standard deviation. Finally, we compare the Isle Royale and Minnesota collagen and hair isotopic data to published δ13C and δ15N values for North American gray wolf populations. We find that interpopulation differences in isotope variances provide insight into wolf foraging ecology.

Craniofacial morphology and feeding behavior inCanis dirus, the extinct Pleistocene dire wolf

AbstractThe craniofacial morphology of the extinct late Pleistocene dire wolfCanis diruswas compared with that of the living gray wolfCanis lupus, the spotted hyaenaCrocuta crocutaand the extinct late Miocene bone‐cracking canidBorophagus secundus. Fifteen indices that have previously been shown to reflect functional significance in the skull, jaws and related musculature of carnivorans were computed from a series of measurements made on the skulls of the four species and subjected to an analysis of variance and a principal components analysis. The results indicated that the extinct dire wolf was similar to the living gray wolf in 11 of the 15 indices. The dire wolf did not differ significantly from the gray wolf in the relative length of resistance arms to various tooth positions in the lower jaw or in the relative size, mechanical advantage and moment arm of the masseter muscle. The dire wolf was characterized by a relatively larger temporalis muscle that was capable of generating more force than that in the gray wolf. The extinct late Miocene borophagine dogB. secunduswas intermediate between the two wolves and the spotted hyaena in most of the cranial and jaw indices, but displayed more similarity to the latter in several key features that can be attributed to their specialization for bone cracking.Borophagus secundusand the spotted hyaena tended to have short resistance arms and large jaw muscles with increased mechanical advantage for bites at various teeth. It is inferred that the dire wolf exhibited feeding behavior that approached that of the living gray wolf, but may have differed in killing technique, where it held longer to its struggling prey.

Mandibular force profiles of extant carnivorans and implications for the feeding behaviour of extinct predators

AbstractA biomechanical approach is used to model the mandibles of extant carnivoran predators (felids, canids, and hyaenids) as beams to gain insight into feeding behaviours. Because bite force applied at any given point along the mandible should be proportional to external dimensions at an analogous location (interdental gaps) on the mandible, patterns of variation in these dimensions will reflect the adaptation of the jaw to specific loads. The mandibular force profiles of extant carnivorans closely reflect particular feeding behaviours. Solitary hunters relying on a powerful canine bite to subdue their prey have a strong mandibular symphysis, while pack hunters delivering shallow bites have a relatively weaker one. Symphyseal shape also gives insight into the feeding behaviour of a predator: (1) a deeper‐than‐long symphysis indicates that stresses induced by the canine bite (or while cracking bones with the anterior dentition) are more important than those induced by struggling prey; (2) an equidimensional symphysis indicates that the symphyseal region is optimally designed to resist torsional stresses induced during prey capture and/or bone cracking; (3) a longer‐than‐deep symphysis indicates that stresses related to prey capture are predominant over those induced by the canine bite or while cracking bone. Mandibular force profiles of juvenile carnivorans also reflect documented ontogenetic changes in feeding behaviour. Because variation in mandibular cross‐sectional properties are interpretable in terms of documented behaviours among extant predators, mandibular force profiles are developed to gain insight into the feeding behaviour of two extinct predators, Panthera atrox and Canis dirus. Results indicate that the feeding behaviour of P. atrox differed slightly from that of modern lions, as the powerful paws restrained prey more efficiently, while C. dirus hunted in a similar fashion to the gray wolf, although it may not have been an efficient bone cracker. Both extinct predators are inferred to have had a more powerful bite than their extant relatives.

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

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.

The last giant of Beringia: the mystery of the Bering Land Bridge

The captivating story of how geologist Dave Hopkins led the scientific world in proving the existence of the vanished land bridge that once connected Siberia to the New World during the Ice Ages. The intriguing theory of a land bridge periodically linking Siberia and Alaska during the coldest pulsations of the Ice Ages had been much debated since Jos de Acosta, a Spanish missionary working in Mexico and Peru, first proposed the idea of a connection between the continents in 1589. But proof of the land bridge - now named Beringia after eighteenth-century Danish explorer Vitus Bering - eluded scientists until an inquiring geologist named Dave Hopkins emerged from rural New England and set himself to the task of solving the mystery. Through the life story of Hopkins, The Last Giant of Beringia reveals the fascinating science detective story that at last confirmed the existence of the land bridge that served as the intercontinental migration route for such massive Ice Age beasts as woolly mammoths, steppe bison, giant stag-moose, dire wolves, short-faced bears, and saber-toothed cats - and for the first humans to enter the New World from Asia. After proving unambiguously that the land

Rancho La Brea stable isotope biogeochemistry and its implications for the palaeoecology of late Pleistocene, coastal southern California

We sampled 143 individuals from Rancho La Brea (RLB) large faunal collections for bone collagen stable carbon ( δ 13C) and nitrogen ( δ 15N) isotope ratios. These collections were recovered from asphalt seeps in the Los Angeles Basin, California, USA, and date from ∼40 to 12 ka. Our findings indicate that despite a slight reduction in collagen nitrogen content, RLB skeletal remains are relatively well preserved and most yield proteins diagnostic of diet. Herbivore δ 13C and δ 15N values covary with rumination and are consistent with changes in late Pleistocene vegetation reconstructed from pollen profiles. We find no evidence for reliance on C 4 grasses at RLB, despite low atmospheric CO 2 concentrations. Carnivore δ 15N values indicate Canis dirus, Smilodon fatalis and Panthera leo atrox competed for similar prey sets and were equally reliant on ruminant and nonruminant prey types. The δ 15N values of Mammut americanum indicate partial reliance on vegetation with lower δ 15N values (such as nitrogen-fixing taxa), distinguishing them from the remainder of the study population. A comparison of RLB and European faunal δ 15N values from the late Pleistocene suggests that coastal southern California experienced greater aridity.