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Giant Cheetah - Acinonyx pardinensis
Topic Started: Apr 6 2012, 03:05 PM (3,849 Views)
Taipan
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Giant Cheetah - Acinonyx pardinensis

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Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Family: Felidae
Genus: Acinonyx
Species:Acinonyx pardinensis

The Giant Cheetah (Acinonyx pardinensis) is an extinct species of big cat; its closest living relative is the modern Cheetah.

Morphology
The lifestyle and physical characteristics of the giant cheetah were probably similar to those of its modern relative, except the giant cheetah was the height of a Lion at the shoulder (but, due to its light build, it weighed considerably less than a http://wild-cats.net/topic/7627291/1/). It was roughly twice the size of today's Cheetahs, putting it at around 79.37–100 kg (175.0–220.5 lb), and about 200 cm (79 in) from head to rump, not including a 140 cm (55 in) tail. Its reconstructed shoulder height was at 90 cm (35 in). Like the modern Cheetah, the giant cheetah was likely a sprinter, but based on its proportions, was probably slower than the modern Cheetah species.

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Just as with the modern Cheetah, almost every aspect of Acinonyx pardinesis is specialized for running. The muzzle is short, nasal passage large for increased air intake during a strenuous sprint. To make room for the enlarged nasal passage, the maxilla was reduced and the anchorage for the canine roots was less, resulting in shorter canine roots and a shorter, more stout external canine, a characteristic seen in the modern Cheetah. To lighten the weight of the animal, bone girth is reduced and the skeleton is lean and light, excellent for running but not fighting or coping with injuries, severe or minor. Its thoracic cavity was consumed by large lungs and a powerful heart. The intestines were probably shorter to lighten the animal and muscles not used for running were reduced. The diaphragm was connected to the movement of its gate and with the stretching phase of a stride, the expansion of space in the abdominal cavity pulled the diaphragm down and forced the animal to inhale, while the contractile phase compressed the lungs and forced air out, so it had no control over its breathing while running, a commonality of most quadruped sprinters. It was a fragile animal who could be killed by a simple sprain if it meant the individual could not run well enough to hunt. Its tail was long, probably thickly furred, and relatively heavy to be used for balance as a counterweight to aid in quick directional changes when chasing prey.

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the skull of modern Acinonyx jubatus. The similarities between the two species are strong (note the small canines and domed frontal bone over large nasal passages).

One of the most complete skulls of this species is from the well-known French site of Saint-Vallier, but the best collection of postcranial bones comes from the older site of Perrier in the Massif Central, including vertebral column and long bones of one individual were found. Unfortunately, the metacarpals were not recovered and so subsequent reconstructions depict them at the same length as the modern Acinonyx.

Distribution and habitat
Giant Cheetahs were present in Europe during the Early and Middle Pleistocene. The Giant Cheetah was found in Germany, France, and also in China and India. European cheetahs occurred alongside Jaguars and Leopards at some Middle Pleistocene localities, and it is possible that competition among the three contributed to the cheetah's decline. Its large mass and more worn claws (when compared to modern Cheetahs) suggest it was less adapted to climbing, an ability which would continue to evolve until modern-day Cheetahs appeared.

Hunting
It could have preyed upon anything from small, contemporary muntjac deer, mountainous ibex and bighorn sheep, to elk and possibly Sambar, prey that was considerably larger than the modern Cheetah's ideal prey, the thomson's gazelle. The modern Cheetah utilizes a specific hunting style seen nowhere else in the cat family: on open plains, it locates prey and walks directly towards a group or individual, without crouching, with head and tail down. When it comes within suitable distance (usually 50 yards), it sprints forward. The chase is fast and takes many turns until the Cheetah uses an enlarged dew claw to hook the hind leg of the prey or smack its flanks to either knock it off balance or damage its Achilles tendon. When the prey falls to the ground, the Cheetah suffocates it with a throat clamp, and after resting, eats as much as it can on the spot before being chased off by larger predators or occasionally having eaten all it can. This sequence of a chase over an open area and the hooking of the back leg is very unique and often necessary for the Cheetah: prey that does not flee is addressed with a great deal of confusion on the Cheetah's part and is often left unharmed if it cannot be coaxed to flee.

Due to the skeletal structure of Acinonyx pardinensis, it is very likely that the larger species used a similar approach to hunting: it, too, bore a large dew claw and the lean form was definitely built for running. A stalk, sprint, trip, and kill was probably a commonality of the large species' hunting tactics. The modern Cheetah almost always uses a throat clamp to suffocate prey and it is likely that this species of Acinonyx used this method of killing. Due to the small canines and weaker jaw muscles of both species, a muzzle clamp (seen in Lions) or severing of the spinal cord (seen in Jaguars) is generally not an option, so a throat clamp would have been used most prominently.

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depicting the forced inhalation and exhalation of Acinonyx while sprinting by shifting of abdominal (green) and Thoracic (red) cavities beneath the skeleton (blue)

Lifestyle and behavior
Within the same species, as shown in the modern species Panthera onca, the South American jaguar and Panthera tigris, the Asian tiger, individuals in higher and colder areas acquire larger sizes. The fossil record for cheetahs is scarce. In contrast to Smilodon fatalis, severe injuries lead to death and there is no sign of cooperation as seen in the latter species of machairodont. Fossils suggest a lifestyle similar to the modern Cheetah species: solitary, except for mothers a cubs and possibly siblings as seen with cheetah brothers, more specialized hunting tactics that narrow the number of species being hunted and therefore increasing the size of a territory and causing the species to be spread out more thinly than the much more adaptable modern Panthera pardus, or Leopard. Vertebrate paleontologist Alan Turner suggests that "since it had the bodily proportions of the living Cheetah, and sinec running speed is a reflections of stride length for a given stride frequency, such large animals may also have been capable of running somewhat faster than their living relatives, although greater weight may have countered any advantage of greater size. Whether they needed to run faster is less clear." The motivation for Acinonyx pardinensis achieving large size could be to keep warm, to move faster, to subdue larger prey, or a combination of the three.

If it was on the same field as the modern Cheetah, it would have been a relatively successful hunter and very wary of injuries and rarely came into contact with others of its species. It would have been cautious, preferred fleeing to fighting and would have been wary of prey that is too large resulting in injuries. Cooperative hunting would generally been out of the question and mortality rates in young would have been high. The modern Cheetah must stop running after about 60 seconds, or when its body temperature rises over 104 degrees Fahrenheit and this large species would have had these confines as well.

Edited by Taipan, Feb 3 2018, 02:33 PM.
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Largest Cheetah Lived, and Killed, Among Ancient Humans

Charles Q. Choi, LiveScience Contributor
Date: 15 August 2011 Time: 09:23 AM

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The extinct cheetah, Acinonyx pardinensis would have weighed double what its modern cousin weighs (shown here in a reconstruction).

Cheetahs might have been the bloodiest killers at one of the oldest known sites for humans, leaving behind more carcasses than any other predator there, scientists find.

That evidence comes from the discovery of the remains of what is now billed as the largest cheetah known, and is now extinct.

The only remaining species of cheetah (Acinonyx jubatus) represents the fastest creatures on land alive, long, sleek cats able to run up to 70 mph (113 kph). However, fossils suggest other species of cheetah, including burlier varieties, once stalked the planet.

Scientists found the fossils at a 1.8-million-year-old site at Dmanisi in the Republic of Georgia, one of the oldest known sites for ancient human species out of Africa. Researchers had discovered fossils of a dirk-toothed cat (Megantereon cultridens) and a similar scimitar cat (Homotherium crenatidens) in the area before.

Based on its arm and paw bones, the stoutly built cheetah (Acinonyx pardinensis) weighed about 220 pounds (110 kilograms), or about double the weight of its modern cousin. (The oldest cheetah fossil known was a skull of Acinonyx kurteni found in China; the animal lived between 2.2 million and 2.5 million years ago.)

The area was once a forested valley floor whose edges blurred into savanna and grasslands, the kind of open ground needed for cheetahs to run down prey, researchers said. In this area, the extinct predator likely preyed on antelope- to horse-size game, probably hunting as a sprinter and suffocating victims by clenching their jaws around the preys' throats. [Top 10 Deadliest Animals]

Given these findings, the researchers said this extinct cheetah likely thrived as a killer, with each cat downing an estimated 16,500 lbs. (7,500 kg) of prey a year, more than any other predator within its community.

"I was really astonished by how much meat it could bring down," said researcher Ralf-Dietrich Kahlke, a paleontologist at the Senckenberg Research Institute in Weimar, Germany.

This bounty of meat would have helped provide others plenty of leftovers, including perhaps humans, who could have either driven the cats away from fresh kills or scavenged the remains after the cheetahs finished dining.

"We don't have any proof of such interactions yet, but we can't exclude them either," Kahlke said.

As to whether cheetahs might have hunted the ancient humans that lived at Dmanisi, "I don't think they really belonged to the spectrum of prey of these cheetahs, but you never know if there were confrontations over kills," Kahlke told LiveScience. All in all, these findings help shed light "on the context of the landscape our ancient relatives interacted with."

Kahlke and colleagues Helmut Hemmera and Abesalom Vekua detailed their findings online July 27 in the journal Quaternary Science Reviews.

http://www.livescience.com/15558-largest-cheetah-lived-killed-ancient-humans.html
Edited by Taipan, Feb 3 2018, 02:35 PM.
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Cheetahs' inner ear is one-of-a-kind, vital to high-speed hunting

February 2, 2018, American Museum of Natural History

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This illustration shows the location of the inner ear in a modern cheetah skull. Credit: © AMNH/N. Wong

The world's fastest land animal, the cheetah, is a successful hunter not only because it is quick, but also because it can hold an incredibly still gaze while pursuing prey. For the first time, researchers have investigated the cheetah's extraordinary sensory abilities by analyzing the speedy animal's inner ear, an organ that is essential for maintaining body balance and adapting head posture during movement in most vertebrates. The study, published today in the journal Scientific Reports and led by researchers at the American Museum of Natural History, finds that the inner ear of modern cheetahs is unique and likely evolved relatively recently.

"If you watch a cheetah run in slow motion, you'll see incredible feats of movement: its legs, its back, its muscles all move with such coordinated power. But its head hardly moves at all," said lead author Camille Grohé, who conducted this work during a National Science Foundation and Frick Postdoctoral Fellowship in the Museum's Division of Paleontology. "The inner ear facilitates the cheetah's remarkable ability to maintain visual and postural stability while running and capturing prey at speeds of up to 65 miles per hour. Until now, no one has investigated the inner ear's role in this incredible hunting specialization."

In the inner ear of vertebrates, the balance system consists of three semicircular canals that contain fluid and sensory hair cells that detect movement of the head. Each of the semicircular canals is positioned at a different angle and is especially sensitive to different movements: up and down, side-to-side, and tilting from one side to the other.

The researchers used high-resolution X-ray computed tomography (CT) at the Museum's Microscopy and Imaging Facility, the National Museum of Natural History in Paris, and the Biomaterials Science Center of the University of Basel in Switzerland to scan the skulls of 21 felid specimens, including seven modern cheetahs (Acinonyx jubatus) from distinct populations, a closely related extinct cheetah (Acinonyx pardinensis) that lived in the Pleistocene between about 2.6 million and 126,000 years ago, and more than a dozen other living felid species. With those data, they created detailed 3-D virtual images of each species' inner ear shape and dimensions.

They found that the inner ears of living cheetahs differ markedly from those of all other felids alive today, with a greater overall volume of the vestibular system and longer anterior and posterior semicircular canals.

"This distinctive inner ear anatomy reflects enhanced sensitivity and more rapid responses to head motions, explaining the cheetah's extraordinary ability to maintain visual stability and to keep their gaze locked in on prey even during incredibly high-speed hunting," said coauthor John Flynn, the Frick Curator of Fossil Mammals in the Museum's Division of Paleontology.

These traits were not present in Acinonyx pardinensis, the extinct species examined by the researchers, emphasizing the recent evolution of the highly specialized inner ear of modern cheetah.

https://phys.org/news/2018-02-cheetahs-ear-one-of-a-kind-vital-high-speed.html




Journal Reference:
Camille Grohé et al, Recent inner ear specialization for high-speed hunting in cheetahs, Scientific Reports (2018). DOI: 10.1038/s41598-018-20198-3

Abstract
The cheetah, Acinonyx jubatus, is the fastest living land mammal. Because of its specialized hunting strategy, this species evolved a series of specialized morphological and functional body features to increase its exceptional predatory performance during high-speed hunting. Using high-resolution X-ray computed micro-tomography (μCT), we provide the first analyses of the size and shape of the vestibular system of the inner ear in cats, an organ essential for maintaining body balance and adapting head posture and gaze direction during movement in most vertebrates. We demonstrate that the vestibular system of modern cheetahs is extremely different in shape and proportions relative to other cats analysed (12 modern and two fossil felid species), including a closely-related fossil cheetah species. These distinctive attributes (i.e., one of the greatest volumes of the vestibular system, dorsal extension of the anterior and posterior semicircular canals) correlate with a greater afferent sensitivity of the inner ear to head motions, facilitating postural and visual stability during high-speed prey pursuit and capture. These features are not present in the fossil cheetah A. pardinensis, that went extinct about 126,000 years ago, demonstrating that the unique and highly specialized inner ear of the sole living species of cheetah likely evolved extremely recently, possibly later than the middle Pleistocene.

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Shape differences of the Vestibular System (VS, highlighted in blue) between the fossil and extant cheetah species. VS in lateral, anterolateral, and dorsal views from top to bottom. Black points = extinct Acinonyx pardinensis Procrustes coordinates; grey points = extant Acinonyx jubatus mean Procrustes coordinates. Numbers correspond to main regions of shape differences: 1, length of the common crus; 2, out-of-plane curvature of the lateral semicircular canal (SC); 3, shape of the anterior SC; 4, shape of the posterior SC; 5, angle between the anterior and posterior SC; 6, width of the lateral SC; 7, position of the bifurcation between the lateral and posterior SC.

https://www.nature.com/articles/s41598-018-20198-3.pdf
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