Dire Wolf (Canis dirus)

The genus Canis includes wolves, coyotes, jackals, and the domestic dogs. In the midwestern U.S. at least three members of the genus are found in sites that date from the last Ice Age. These three members are the dire wolf (Canis dirus), the gray wolf (Canis lupus) and the coyote (Canis latrans). One additional species, the domestic dog (Canis familiaris), was almost certainly also present at the very end of the Pleistocene (after about 12,000 years ago).

The gray wolves and coyotes of the last Ice Age were probably very similar in look and behavior to their modern relatives. The dire wolf was not quite like any animal surviving today. It was similar in overall size and mass to a large modern gray wolf. This means it was about 1.5 meters (5 feet) long and weighed about 50 kilograms (110 pounds) on average.

The dire wolf looked fairly similar to the modern gray wolf; however, there were several important differences. The dire wolf had a larger, broader head and shorter, more sturdy legs than its modern relative.

The teeth of dire wolf were much larger and more massive than those of the gray wolf.  They may have been used to crush bones.

The braincase of the dire wolf was also smaller than that of a similarly-sized gray wolf. The jaws of the dire wolf and grey wolf also show the larger size of the dire wolf’s teeth.

Many paleontologists think that the dire wolf may have used its relatively large, massive teeth to crush bone. This idea is supported by the fact that dire wolf teeth frequently have large amounts of wear on their crowns. Several people have suggested that dire wolves may have made their living in similar ways to modern hyenas.

Wolves and coyotes are relatively common large carnivores found in Ice Age sites. In fact, several thousand dire wolves have been found in the asphalt pits at Rancho La Brea in Los Angeles, California. The coyote, gray wolf, and dire wolf have all been found in paleontological sites in the midwestern U.S.

The fact that the lower parts of the legs of the dire wolf are proportionally shorter than those of the gray wolf indicates that the dire wolf was probably not as good a runner as the gray wolf.

The genus Canis underwent a mixed fate at the end of the Pleistocene. The gray wolf and coyote survived the extinction that occurred approximately 11,500 years ago. The dire wolf, however, was one of the animals that did not survive. Perhaps the dire wolf depended on scavanging the remains of the large herbivores of the last Ice Age. The extinction of these herbivores may have then led to the extinction of the dire wolf. Scientists do not know if this is the case; however, they continue to search for the reason that many kinds of mammals went extinct about 11,500 years ago.

 

 

Sources:

 La Brea Tar Pits
Wikipedia
Natural Worlds

Saber-toothed Cat (Smilodon californicus)

Despite the popular nickname Saber Tooth Tiger, these ancient felines were not tigers at all. Evidence suggests that unlike tigers, Simlodons were social animals that hunted in packs, much like today’s lions. They also had the muscle mass and physical bulk that’s more comparable to a bear today than that of a tiger. It’s also very unlikely that their coat was striped like a tiger, but rather probably dappled like a bobcat or plain like a today’s lions given the habitat in which they lived. They would not have needed to blend in with thick forest or jungle like a tiger, but rather blend in with open tundra and grasses.

from How Stuff Works:

Naturally, saber-tooth cats are known for their distinctive teeth — two very long canines that extended well past the bottom of the jaw. These canines were about twice as thick from front to back as from side to side, so they resembled very thick, somewhat curved knife blades. In Smilodon fatalis, adults’ saber teeth could measure up to 7 inches (18 centimeters) long. That’s about as long as the average man’s hand from the wrist to the end of the middle finger.
But the cats’ teeth weren’t always so big. Saber-tooth cats had deciduous baby teeth, just like people and many other mammals do. The cats lost their baby teeth, including a set of miniature saber canines, before they entered adolescence. In order to reach the necessary length, their adult canines grew at a rate of about 8 millimeters a month for more than 18 months. Today’s tigers’ teeth grow about this fast, but the canines of saber-tooth cats grew for a longer period of time than tiger teeth do.

The sheer size of a saber-tooth cat’s canines can make it seem like eating or attacking prey would be a problem. But saber-tooth cats had the ability to open their mouths very wide to make up for the extreme length of their teeth. Smilodon fatalis could open its mouth up to 120 degrees wide. This let the cats take big bites, although, according to computerized tomography (CT) scans, they used those big bites for soft flesh, not thick bones. The cats’ skulls weren’t designed to handle the pressure of biting through bone. They also weren’t designed to provide anchors for the amount of muscle needed to hang on to struggling prey for a long time. That’s one reason why saber-tooth cats tended to aim for the throat or abdomen instead of the bonier parts of their prey.

The legs and bodies of this carnivore were short and squat, made up of muscle mass. This cat would have weighed between 600 and 700lbs, while the modern lion only weighs up to 500. Saber-tooth cats also lacked the long tail that today’s lions use for balance. This may have made saber-tooth cats stronger but less agile than most of today’s big cats.The lack of a long tail is also one reason why scientists don’t call them saber-tooth tigers or saber-tooth lions.

The social patterns of this cat aren’t quite known. Scientists believe they hunted in packs and were drawn to prey by the distress calls of dying animals in the La Brea Tar Pits. Smilodon Californicus is one of the most common specimens found in the pits. Also, several specimens have been found that had severe injuries, however the animal seemed to have lived for a long time with the injury. This suggests Simlodons may have lived in packs and cared for their injured peers – sharing food with those unable to hunt. Living in groups also may have aided the cats in defense against Short-Faced Bears and Dire Wolves. Smilodon Californicus probably preyed on a wide variety of animals including wild bison, ground sloths, camels, horses, and deer.

from Wikipedia:

Modern big cats kill mainly by crushing the windpipe of their victims, which may take a few minutes. Smilodon’s jaw muscles were probably too weak for this and its long canines and fragile skull would have been vulnerable to snapping in a prolonged struggle or when biting a running prey. Research in 2007 concluded that Smilodon more probably used its great upper-body strength to wrestle prey to the ground, where its long canines could deliver a deep stabbing bite to the throat which would generally cut through the jugular vein and / or the trachea and thus kill the prey very quickly.

Sources:
How Stuff Works
Wikipedia
University of California Museum of Palentology

Merriam’s Teratorn (Teratornis merriami)

Teratorn and coyote Mark Hallett illusration

Teratorns, (from the greek Teratornis “Monster Bird”) were massive Pleistocene birds. Merriam’s Teratorn lived in Northern America. Over 100 of this species have been found at the Rancho La Brea Tar Pits. While these birds have a skeletal structure that is similar to a condor, research indicates that these birds were active predators that stalked their prey from the air – and did not solely survive on carrion. It’s wingspan was 11-12 feet in length, and it’s body weighed about twice as much as the modern day California Condor. The legs were similar to an Andean Condor’s, but more stout, and the feet were able to hold prey for tear off pieces, but did not have the forceful grip of birds of prey. It’s lifestyle was similar to that of a condor, but it’s beak does suggest it ate some small prey whole (such as rabbits) and also hunted aquatic prey in a manner similar to an Osprey. It fed on carrion in a way similar to a vulture, and it’s believed that so many of these specimens have been found in the tar pits because they were attracted to dead and dying animals already trapped, and then became trapped in the tar as well.

A closely related genus, the Aiolornis, was about 40% larger and lived at an earlier time in Argentina; it was formerly known as Teratornis incredibilis, but is distinct enough to be placed in its own genus.

All skeletal remains but one early Pleistocene exception of a partial skeleton from the Leisey Shell Pit near Charlotte Harbor, Florida (which may represent a different species or a subspecies), date from the late Pleistocene with the youngest remains dating from the Pleistocene-Holocene boundary.

 

Sources:
La Brea Tar Pits
Wikipedia
Carnivora Forum

Harlan’s Ground Sloth (Paramylodon harlani)

Harlan's Ground Sloth Illustration William Stout

From La Brea Tar Pits Website:

Evolving from the tree sloths in South America, ground sloths are very distantly related to anteaters and armadillos. As this animal adapted from a tree dweller to being ground-based, its limbs still showed a relationship to its ancestors. Typically, ground sloths walked on the sides of their hind feet and the backs of their forefeet.

Harlan’s ground sloth was the largest and most common of the ground sloths found at Rancho La Brea. It stood over six feet tall and weighed almost 3,500 pounds. This animal had flat grinding teeth that suggest a diet of grasses, but may have also fed on leaves, tree roots, and twigs. One of the most interesting features of the Harlan’s ground sloth were its skin bones, or dermal ossicles. These small bones were deep under the skin around the neck, shoulders and back and may have served as armor against attacking predators. They were not connected to the main skeleton and were unique to this type of ground sloth.

The skeletal structure of these ground sloths indicates that the animals were massive. Their thick bones and even thicker joints (especially those on the hind legs) gave their appendages tremendous power that combined with their size and fearsome claws, provided a formidable defense against predators.

These ground sloths had a massive skeletal structure. Their thick joints and bones gave them tremendous power in their arms and legs, as well as their long tail. Combined with their huge size and massive claws, the strength of this creature provided a strong defense against predators. On hind legs, Paramylodon was roughly the same size as the Giant Short-Faced Bear, and could most likely wrestle one to the ground in a fight for it’s life.

Sources:
La Brea Tar Pits
Wikipedia
Illinois State Museum

Giant Short-Faced Bear (Arctodus simus)

Reconstruction of the Giant Short-faced Bear, Arctodus

From Carnivora Forum:

Arctodus simus stood as high as two meters (seven feet) at the shoulder on all four legs. When standing bipedally, the animal was over 3.4 meters (11 ft) in total height. It is estimated to have an average weight of 860-940 kg (1900-2500 pounds), around 42% larger than its contemporary the grizzly bear. The largest specimens were found in Alaska and the Yukon Territory. Males were 20% bigger than females. It was the largest land predator during the Ice Age in North America. The skull was unusual due to its lack of a well-defined forehead and the presence of a short broad muzzle, resembling that of Panthera rather than that of any modern bears. The muscles which passed between the broad cheek bones to power the lower jaws were extremely well-developed and are thought to be adapted for bone crushing in order to obtain the rich marrow. An Arctodus lower jaw can be distinguished from those of the genus Ursus by the slanting ridge dividing muscle attachment areas. Rather than having a waddling gait like modern bear species, Arctodus had toes extending straight forward, presumably being able to move with greater ease. In addition, unlike Ursus, Arctodus had a passage on the lower inside portion of the humerus for a slip of muscle (entepicondylar foramen).

Analysis of Arctodus bones showed high concentrations of nitrogen-15, a stable nitrogen isotope accumulated by meat-eaters, with no evidence of ingestion of vegetation. Based upon this evidence Arctodus simus was highly carnivorous, and as an adult would have required over 35 lbs of flesh per day to survive.

The monstrous Arctodus Bear was six feet tall on all fours, yet it could out-run a horse. It was twice the size, and much more powerful than a modern grizzly bear. It’s long legs and ability to reach fast speeds (up to 30 or 40 miles an hour) may have allowed it to run down Pleistocene prey much like a hunting feline. However in this scenario, Arctodus’s size would have been a handicap – it’s skeleton was not built for making the sharp turns characteristic of any predator who hunts agile prey to survive. Rather, scientists think Arctodus moved in a pacing motion like modern bears, with a body built more for endurance than speed. It’s also thought that Arctodus simus used it’s great size and power to intimidate it’s Pleistocene peers like the Dire Wolf and American Lion away from their kills.

Sources:
La Brea Tar Pits
Wikipedia