Skull Comparison

Click each skull to learn more.

Skull Comparison
Short-faced bear Dire wolf Coyote Bobcat American lion Llama Jack rabbit Brush rabbit Pocket gopher Giant ground sloth Horse Mastodon

Short-faced bear

Fragment of Short faced bear lower jaw

Short-faced bear (Arctodus simus)

A very large extinct bear that had long legs and a short face

Dire wolf

Dire wolf (Canis dirus)

Unlike popular media depictions, dire wolves were only slightly larger than most grey wolves (Canis lupus). Limb bone ratios indicate that they would not have been as fleet as modern wolves, which may have contributed to their extinction following the last glacial maximum.


Coyote (Canis latrans).

In the Pleistocene coyotes varied widely in size, from about the same as modern coyotes to the size of very large grey wolves. Unlike grey wolves, which immigrated here from Eurasia, coyotes are endemic to North America.



Fossil lower jaw of Lynx rufus (bobcat)

Bobcat (Lynx rufus)

The bobcat is an extant wild cat that is found throughout much of Mexico, the United States and Southern Canada. They are about 2.7 feet (82.7 cm) long and weigh 15-21 pounds (6.8-9.5 kg) making them a medium-sized wild cat. Bobcats are carnivores that eat rabbits, hares, rodents, birds (along with fledglings and eggs), fish, insects and even small sharks. They will also feed on larger animals such as young ungulates like sheep, deer and goats and other carnivores like foxes, minks, and skunks. Predators of the bobcat include humans, wolves, mountain lions, and coyotes.


American lion

American lion (Panthera atrox)

The American lion was a big cat that was just a little larger than a modern African lion. They are relatively more common at McKittrick than at other California tar seeps.



Llama (Hemiauchenia macrocephala).

These llamas and their camel cousins were once native to North America and are common in ice age deposits throughout the country. Isotope tests of their tooth enamel have shown that they often ate plants that were adapted to arid environments, much like modern llamas.


Jack rabbit

Fossil of rabbit lower jaw

Jackrabbit (Lepus californicus).

The black-tailed jackrabbit is an extant hare found in the Western United States and Mexico. It is the third-largest North American jackrabbit at about 2 feet (61 cm) long, and weighs 3-6 pounds (1.4-2.7 kg). Jackrabbits are herbivores that eat grasses, leaves, alfalfa, seeds, beans, cacti, winter wheat, dandelions, blue grama grass, clovers, grains, roots, twigs, forms, shrubs, small trees and buds of fruit trees. Predators of jackrabbits include coyotes, wolves, bobcats, mountain lions, eagles, hawks, owls, foxes, badgers and humans.


Brush rabbit

Fossil of cottontail rabbit jaw fragment

Brush rabbit (Sylvilagus bachmani).

The brush rabbit (Sylvilagus bachmani) is an extant rabbit found along the Pacific coast of the United States down to Baja, Mexico. They are 12-14.5 inches (30.5-36.8 cm) long and weigh 1.1-2.0 pounds (511-917 g).

Brush rabbits are herbivores that live in dense brushy habitats. Their diet varies with the season, but they mainly feed on grasses. They also eat forbs, leaves, wild rose, woody vegetation and berries. Their favorite food is green clover. Almost all predators prey on the brush rabbit including humans, snakes, coyotes, mountain lions, foxes, and birds of prey.


Pocket gopher

Pocket gopher (Thomomys spp.).

Botta's pocket gopher is an extant gopher found in the South Western United States and parts of Mexico. They are 6-10 inches (15.2-25.4 cm) long, and weigh 4.2-8.8 oz (120-250 g). Pocket gophers are herbivores with shoots and grasses being an important part of their diet, supplemented by forbs, alfalfa roots, tubers, acorns, seedlings, trees, and bulbs. Some of their favorite foods are carrots, wheat plants, alfalfa and dandelions. Predators of pocket gophers include badgers, coyotes, weasels, snakes, owls, bobcats, skunks, hawks.


Giant ground sloth

Fossil of giant sloth jaw

Ground sloths (Paramylodon harlani).

Ground sloths once roamed North and South America, though only their small tree-dwelling relatives exist today. They were larger than modern cows, about the same size as a very large American bison, and had long claws on their front feet.



Horse (Equus).

The Western horse is an extinct species of horse and one of the most common mammals at the McKittrick Tar Seeps. It was a stocky and robustly built horse about the size of a modern mustang, but weighing up to 1,144 pounds (519 kg). The Western horse was an herbivore that mostly grazed and did some foraging. They ate some grasses and shrubs, but focused on woody browse. They occupied a different dietary niche than modern horses which primarily browse on grasses while the Western horse was an opportunistic feeder that consumed a higher percentage of leaves and shrubs.Common predators of the Western horse were dire wolves and the American lion.



Mastodon (Mammut americanum).

Mastodons are uncommon at McKittrick, and were likely seasonal visitors. They were browsers, and would have found food plentiful in the uplands following the spring rains.