Smilodon (Sabre Toothed Tiger) Lived on the Plains in South America During the Pleistocene Quaternary

Paleobiology of sabretooth cat Smilodon populator in the Pampean Region (Buenos Aires Province, Argentina) around the Last Glacial Maximum: Insights from carbon and nitrogen stable isotopes in bone collagen

Authors:

Bocherens et al

Abstract:

The sabretooth cat Smilodon populator was the largest felid in South America. It appears in the fossil record in the Early Pleistocene, as an immigrant from North America, and becomes extinct around the Pleistocene–Holocene boundary. The carbon and nitrogen stable isotopic values of collagen were measured for skeletal remains from Smilodon specimens ranging in age from 25 to 10 kyr BP, for the first time in the Pampas region of Argentina. By comparison with similar values obtained on co-eval predators such as Protocyon (large canid) and Panthera onca (jaguar) and a range of potential prey, such as giant ground sloths, glyptodontids, Macrauchenia, Toxodon, equids, cervids, and rodents, it could be established that Smilodon consumed essentially large prey from open landscape, such as Macrauchenia and giant ground sloths during the last 15,000 years of the Late Pleistocene in the Pampa region. It was possibly competing with the large canid Protocyon but the jaguar was apparently feeding on smaller size prey. A more humid climate at the beginning of the Holocene might have been unfavorable to this large predator and could have contributed to its extinction. These results also provide an important insight to understand the ecological processes involved in the Great American Biotic Interchange.

Cheetahs Originated in North America, Suffered two Population Bottlenecks

The cheetah (Acinonyx jubatus) is now at home on the African plains, but it started a migration 100, 000 years ago from North America towards its current habitat. The research, published in the open access journal Genome Biology, found that the migration from North America was costly for the species, triggering the first major reduction in their gene pool.

The modern African cheetah is found across eastern and southern Africa, but it is highly endangered because of their small free ranging population and inbreeding. Researchers from St. Petersburg State University, Russia, in collaboration with BGI, China and CCF, Namibia, sequenced the genome from a male Namibian cheetah, called 'Chewbaaka', and six other wild cheetahs from Tanzania and Namibia. This gave further insight into the species evolutionary history and the breadth of genome impoverishment, which elevates juvenile mortality, causes extreme abnormalities in sperm development and increases vulnerability to infectious disease outbreaks.

A total of 18 cheetah genes showed damaging mutations and one gene in particular, AKAP4, showed a large number of mutations, which could harm sperm development and may explain why cheetah have a large proportion of defective sperm, and hence their low reproductive success.

The cheetah is descended from a relative of American pumas and their fossil record extends across the Americas, Europe and Asia. The species has suffered two population bottlenecks - an event whereby the population is rapidly reduced due to environmental factors.

The first of these took place 100, 000 years ago, around the late Pleistocene - a geological period shaped by repeated glaciations, when cheetahs started to move towards Asia across the Beringian landbridge and then travelled south to Africa. This migration was punctuated with dwindling populations and limited gene flow due to the individuals' own vast territory boundaries, measuring 300-800 square miles, thereby increasing incestuous mating.

The second bottleneck around 10- 12, 000 years ago, further reduced numbers, leading to further loss of endemic variability observed in modern cheetahs.

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Jaw Function in Smilodon fatalis

Jaw Function in Smilodon fatalis: A Reevaluation of the Canine Shear-Bite and a Proposal for a New Forelimb-Powered Class 1 Lever Model

Author:

Brown

Abstract:

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.

Cat Genome Decoded, Gives Clues to Domestication

Cats and humans have shared the same households for at least 9,000 years, but we still know very little about how our feline friends became domesticated. An analysis of the cat genome by researchers at Washington University School of Medicine in St. Louis reveals some surprising clues.

The research appears Nov. 10 in the Proceedings of the National Academy of Sciences Early Edition.

Cats have a relatively recent history of domestication compared with dogs; canines arose from wolves over 30,000 years ago.

"Cats, unlike dogs, are really only semidomesticated," said senior author Wes Warren, PhD, associate professor of genetics at The Genome Institute at Washington University​. "They only recently split off from wild cats, and some even still breed with their wild relatives. So we were surprised to find DNA evidence of their domestication."

One way scientists can understand the genetics of domestication is to look at what parts of the genome are altered in response to living together with humans, Warren added.

The researchers compared the genomes of domestic cats and wild cats, finding specific regions of the domestic cat genome that differed significantly.

The scientists found changes in the domestic cat's genes that other studies have shown are involved in behaviors such as memory, fear and reward-seeking. These types of behaviors -- particularly those when an animal seeks a reward -- generally are thought to be important in the domestication process.

"Humans most likely welcomed cats because they controlled rodents that consumed their grain harvests," said Warren. "We hypothesized that humans would offer cats food as a reward to stick around."

This meant that certain cats that would normally prefer to lead solitary lives in the wild had an additional incentive to stay with humans. Over time, humans preferred to keep cats that were more docile.

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Cougars Survived the Beginning Holocene Megafaunal Extinction due to Dietary Generalism

Cougars may have survived the mass extinction that took place about 12,000 years ago because they were not particular about what they ate, unlike their more finicky cousins—the saber-tooth cat and American lion. Both perished along with the woolly mammoth and many of the other supersized mammals that walked the Earth during the late Pleistocene.

That is the conclusion of a new analysis of the microscopic wear marks on the teeth of cougars, saber-tooth cats and American lions described in the April 23 issue of the journal Biology Letters.

"Before the Late Pleistocene extinction six species of large cats roamed the plains and forests of North America. Only two – the cougar and jaguar – survived. The goal of our study was to examine the possibility that dietary factors can explain the cougar's survival," said Larisa R.G. DeSantis, assistant professor of earth and environmental sciences at Vanderbilt University, who co-authored the study with Ryan Haupt at the University of Wyoming.

For their investigation, DeSantis and Haupt employed a new technique called dental microwear texture analysis. DMTA uses a confocal microscope to produce a three-dimensional image of the surface of a tooth. The image is then analyzed for microscopic wear patterns. The analysis of the teeth of modern carnivores, including hyenas, cheetahs and lions has established that the meals an animal consumes during the last few weeks of its life leave telltale marks. Chowing down on red meat, for example, produces small parallel scratches while chomping on bones adds larger, deeper pits.

The researchers analyzed the teeth of 50 fossil and modern cougars, and compared them with the teeth of saber-tooth cats and American lions excavated from the La Brea Tar Pits in Los Angeles and the teeth of modern African carnivores including cheetahs, lions and hyenas.

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Promegantereon ogygia: a Miocene Neogene Machairodont Sabre Tooth Cat

Promegantereon ogygia (Felidae, Machairodontinae, Smilodontini) from the Vallesian (late Miocene, MN 10) of Spain: morphological and functional differences in two noncontemporary populations

Authors:

Siliceo et al

Abstract:

We compare two populations of the primitive saber-toothed felid Promegantereon ogygia from the late Miocene (Vallesian, MN 10) of Spain. These populations come from two fossil sites, Batallones-1 and Batallones-3, located very close to each other, within the Cerro de los Batallones complex. The sites show differences in age and in their faunal assemblages, with Batallones-1 being older than Batallones-3. We find that the population from this latter site shows slightly derived characters in both dentition and postcranial elements, which clearly indicate evolution within the Promegantereon lineage, but are not strong enough to support a separation at the species level.

Panthera blytheae: The Old Known Great Cat Originates in Plioecene Neocene Tibet

The oldest big cat fossil ever found – which fills in a significant gap in the fossil record – was discovered on a paleontological dig in Tibet, scientists announced today.

A skull from the new species, named Panthera blytheae, was excavated and described by a team led by Jack Tseng – a PhD student at the USC Dornsife College of Letters, Arts and Sciences at the time of the discovery, and now a postdoctoral fellow at the American Museum of Natural History (AMNH) in New York.

"This find suggests that big cats have a deeper evolutionary origin than previously suspected," Tseng said.

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Tiger Genome Mapped

The first sequenced tiger genome shows that big cats evolved to kill.

Genes for strong muscle fibers and for meat-eating appear narrowly shared, researchers reported, among species as distinct as the African lion and Asia's snow leopard.

Scientists mapped the genes of the endangered Siberian tiger (or Amur tiger), both to understand the genes that make big cat species distinct from one another and to aid efforts to preserve genetic diversity in wild tiger populations.

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Therapsid-Archosaur Wars Continue: See a Jaguar Kill a Caiman

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How Late Did the Barbary Lion Survive?

Examining the Extinction of the Barbary Lion and Its Implications for Felid Conservation

Authors:

1. Simon A. Black (a)
2. Amina Fellous (b)
3. Nobuyuki Yamaguchi (c)
4. David L. Roberts (a)

Affiliations:

a. Durrell Institute of Conservation and Ecology, School of Anthropology and Conservation, University of Kent, Canterbury, Kent, United Kingdom

b. Agence Nationale pour la Conservation de la Nature, Algiers, Algeria

c. Department of Biological and Environmental Sciences, University of Qatar, Doha, Qatar

Abstract:

Estimations of species extinction dates are rarely definitive, yet declarations of extinction or extirpation are important as they define when conservation efforts may cease. Erroneous declarations of extinctions not only destabilize conservation efforts but also corrode local community support. Mismatches in perceptions by the scientific and local communities risk undermining sensitive, but important partnerships. We examine observations relating to the decline and extinction of Barbary lions in North Africa. Whilst the extinction predates the era of the scientific conservation movement, the decline is relatively well documented in historical records. Recently unearthed accounts suggest Barbary lions survived later than previously assumed. We use probabilistic methods to estimate a more recent extinction date for the subspecies. The evidence presented for a much later persistence of lions in North Africa, including generations when sightings were nil, suggests caution when considering felid populations as extinct in the wild. The case raises the possibility that captive animals descended from the Moroccan royal collection are closer contemporaries to wild Barbary lions. Furthermore, our results highlight the vulnerability of very small lion populations and the significance of continued conservation of remnant lion populations in Central and West Africa.

No Evidence of Dietary Change for American Lions and NorAm Smilodon Prior to Extinction

In the period just before they went extinct, the American lions and saber-toothed cats that roamed North America in the late Pleistocene were living well off the fat of the land.

That is the conclusion of the latest study of the microscopic wear patterns on the teeth of these great cats recovered from the La Brea tar pits in southern California. Contrary to previous studies, the analysis did not find any indications that the giant carnivores were having increased trouble finding prey in the period before they went extinct 12,000 years ago.

The results, published on Dec. 26 in the scientific journal PLOS ONE, contradicts previous dental studies and presents a problem for the most popular explanations for the Megafaunal (or Quaternary) extinction when the great cats, mammoths and a number of the largest mammals that existed around the world disappeared.

"The popular theory for the Megafaunal extinction is that either the changing climate at the end of the last Ice Age or human activity – or some combination of the two – killed off most of the large mammals," said Larisa DeSantis, assistant professor of earth and environmental sciences at Vanderbilt, who headed the study. "In the case of the great cats, we expect that it would have been increasingly difficult for them to find prey, especially if had to compete with humans. We know that when food becomes scarce, carnivores like the great cats tend to consume more of the carcasses they kill. If they spent more time chomping on bones, it should cause detectable changes in the wear patterns on their teeth."

In 1993, Blaire Van Valkenburgh at UCLA published a paper on tooth breakage in large carnivores in the late Pleistocene. Analyzing teeth of American lions, saber-tooth cats, dire wolves and coyotes from La Brea, she found that they had approximately three times the number of broken teeth of contemporary predators and concluded, "...these findings suggest that these species utilized carcasses more fully and likely competed more intensely for food than present-day large carnivores."

The latest study uses a new technique, called dental microwear texture analysis (DMTA), developed by co-authorPeter Ungar at the University of Arkansas. It uses a confocal microscope to produce a three-dimensional image of the surface of a tooth. The image is then analyzed for microscopic wear patterns. Chowing down on red meat produces small parallel scratches. Chomping on bones adds larger, deeper pits. Previous methods of dental wear analysis relied on researchers to identify and count these different types of features. DMTA relies on automated software and is considered more accurate because it reduces the possibility of observer bias.

DeSantis and Ungar, with the assistance of Blaine Schubert from East Tennessee State University and Jessica Scott from the University of Arkansas, applied DMTA to the fossil teeth of 15 American lions (Panthera atrox) and 15 saber-tooth cats (Smilodon fatalis) recovered from the La Brea tar pits in Los Angeles.

Their analysis revealed that the wear pattern on the teeth of the American lion most closely resembled those of the present-day cheetah, which actively avoids bones when it feeds. Similarly, the saber-tooth cat's wear pattern most closely resembled those of the present-day African lion, which indulges in some bone crushing when it eats. (This differs from a previous microwear study using a different technique that concluded saber-tooth cats avoided bone to a far greater extent.)

The researchers examined how these patterns changed over time by selecting specimens from tar pits of different ages, ranging from about 35,000 to 11,500 years ago. They did not find any evidence that the two carnivores increased their "utilization" of carcasses throughout this period. If anything, their analysis suggests that the proportion of the carcasses that both kinds of cats consumed actually declined toward the end.

The researchers acknowledge the high rate of tooth breakage reported in the previous study, but they argue that it is more likely the result of increased breakage when taking down prey instead of when feeding.

"Teeth can break from the stress of chewing bone but they can also break when the carnivores take down prey," DeSantis pointed out. Species like hyenas that regularly chew and crack bones of their kills are as likely to break the rear teeth they use for chewing as their front canines. Species like the cheetah, however, which avoid bones during feeding are twice as likely to break canines than rear teeth. This suggests that they are more likely to break canines when pulling down prey.

The researchers report that previous examinations of the jaws of the American lions and saber-tooth cats from this period found that they have more than three times as many broken canines and interpret this as additional evidence that supports their conclusion that most of the excess tooth breakage occurred during capture instead of feeding.

In addition, the researchers argue that the large size of the extinct carnivores and their prey can help explain the large number of broken teeth. The saber-toothed cats were about the size of today's African lion and the American lion was about 25 percent larger. The animals that they preyed upon likely included mammoths, four-ton giant ground sloths and 3,500-pound bison.

How Miocene Sabre Tooths and Bear Dogs Got Along? Niche Partitioning

(Miocene carnivores of Florida, similar, but not the same as below.  img credit)

The fossilized fangs of saber-toothed cats hold clues to how the extinct mammals shared space and food with other large predators 9 million years ago.

Led by the University of Michigan and the Museo Nacional de Ciencias Naturales in Madrid, a team of paleontologists has analyzed the tooth enamel of two species of saber-toothed cats and a bear dog unearthed in geological pits near Madrid. Bear dogs, also extinct, had dog-like teeth and a bear-like body and gait.

The researchers found that the cat species—a leopard-sized Promegantereon ogygia and a much larger, lion-sized Machairodus aphanistus—lived together in a woodland area. They likely hunted the same prey—horses and wild boar. In this habitat, the small saber-toothed cats could have used tree cover to avoid encountering the larger ones. The bear dog hunted antelope in a more open area that overlapped the cats' territory, but was slightly separated.

"These three animals were sympatric—they inhabited the same geographic area at the same time. What they did to coexist was to avoid each other and partition the resources," said Soledad Domingo, a postdoctoral fellow at the U-M Museum of Paleontology and the first author of a paper on the findings published in the Nov. 7 edition of Proceedings of the Royal Society B.

Millions of years before the first humans, the predators lived during the late Miocene Period in a forested area that had patches of grassland. Large carnivores such as these are rare in the fossil record, primarily because plant-eating animals lower on the food chain have outnumbered meat-eaters throughout history.

Cerro de los Batallones, where Domingo has been excavating for the past eight years, is special. Of its nine sites, two are ancient pits with an abundance of meat-eating mammal bones. Agile predators, the researchers say, likely leapt into the natural traps in search of trapped prey.

"These sites offer a unique window to understand life in the past," Domingo said.

To arrive at their findings, the researchers conducted what's called a stable carbon isotope analysis on the animals' teeth. Using a dentist's drill with a diamond bit, they sampled teeth from 69 specimens, including 27 saber-toothed cats and bear dogs. The rest were plant-eaters. They isolated the carbon from the tooth enamel. Using a mass spectrometer, which you could think of as a type of scale, they measured the ratio of the more massive carbon 13 molecules to the less-massive carbon 12. An isotope is a version of an element that contains a different number of neutrons in its nucleus.

[..]

Because the researchers can tell what the herbivores ate, they can surmise what their habitat was like. They believe the animals in this study lived in a wooded area that contained patches of grassland.

The cats showed no significant difference in their stable carbon isotope ratios. That means they likely fed on the same prey and lived in the same habitat, but the posits that the species each fed on different-sized prey.

[...]

"The three largest mammalian predators captured prey in different portions of the habitat, as do coexisting large predators today. So even though none of the species in this 9-million year old ecosystem are still alive today (some of their descendants are), we found evidence for similar ecological interactions as in modern ecosystems," said Catherine Badgley, co-author of the new study and assistant professor of ecology and evolutionary biology.

Smilodon: Pack Cat?

The sabertooth cat (Smilodon fatalis), one of the most iconic extinct mammal species, was likely to be a social animal, living and hunting like lions today, according to new scientific research. The species is famous for its extremely long canine teeth, which reached up to seven inches in length and extended below the lower jaw.

Instead of relying on the bones and teeth of the sabertooths to make their findings, scientists from UCLA and the Zoological Society of London concluded that the sabertooth cat was social by using a novel technique: They compared numbers of present-day carnivores competing for kills in Africa with those of mainly extinct species found in a North American fossil deposit.

The research is published in the current issue of the Royal Society's journal Biology Letters (Oct. 28). Co-authors also included scientists from South Africa's Tshwane University of Technology and University of Pretoria.

Smilodon existed in North and South America between 1.8 million and 10,000 years ago and is one of the most common species preserved at the Rancho La Brea tar pits of Los Angeles, a fossil deposit in which dying herbivores trapped in sticky asphalt attracted numerous dire wolves and sabertooth cats, some of which also died there.

Because most living cats are solitary, controversy has persisted over the social life of Smilodon.

The study reported in Biology Letters took a new approach to the question by comparing data from the La Brea fossil record and data obtained from "playbacks" used in Africa, in which the recorded calls of distressed prey and the sounds of lions and hyenas are used to attract carnivores. This technique has been used by scientists to estimate carnivore densities in eastern and southern Africa.

hrmmm.

Cat Skull Functional Evolution

In a new study published in the online-open access journal PLoS ONE, Per Christiansen at the Zoological Museum in Copenhagen, Denmark, reports the finding that the evolution of skull and mandible shape in sabercats and modern cats were governed by different selective forces, and the two groups evolved very different adaptations to killing.

The cat family comprises some of the most specialised carnivores in the history of mammals, all exclusively eating flesh. The cat family consists of two major sub-groups: the feline cats (including all modern species) and the sabertoothed cats (which are all extinct). Skeletons from the two groups look broadly similar, but their skulls are often remarkably different, and suggest that members of the two groups underwent radically different adaptations to predation during the course of evolution.

Sabertoothed cats have been a particularly difficult group to understand because their anatomical features are often radically different from those of modern cats. However, new techniques for anatomical comparison using digital methods have facilitated a more detailed comparison of the anatomy of the entire skull and mandible, and the new results add significantly to our understanding of the evolution of the cat family.

Maybe Manabu can comment a little more. This seems right up his alley.