Here's what I've come up with.
Sarkastodon
Large Animal
Hit Dice: 15d8+75 (142 hp)
Initiative: +1
Speed: 40 ft. (8 squares)
Armor Class: 17 (-1 size, +1 Dex, +7 natural), touch 10, flat-footed 16
Base Attack/Grapple: +11/+26
Attack: Claw +21 melee (xdx+11)
Full Attack: 2 claws +21 melee (xdx+11) and bite +x melee (xdx+5)
Space/Reach: 10 ft./5 ft.
Special Attacks: Trip?
Special Qualities: Low-light vision, scent
Saves: Fort +14, Ref +10, Will +x
Abilities: Str 33, Dex 13, Con 21, Int 2, Wis 12, Cha 10
Skills: 18 points
Feats: 6
Environment: Temperate plains
Organization: Solitary or pair
Challenge Rating: x
Treasure: None
Alignment: Always neutral
Advancement: x
Level Adjustment: -
This brown-furred predatory beast is nearly the size of a rhinoceros. It resembles a melding of bear and cat, with a leonine face and a bear-like body terminating in a long, furry tail.
The bear-like sarkastodon is a creodont, the creodonts being the dominant mammalian land predators prior to the carnivorans. Larger than a grizzly bear, the sarkastodon preys upon Large herbivores like brontotheres, though it may occasionally eat plant matter (and the unlucky adventurer) as well. Sarkastodons are an ever-present danger in lost lands, attracted to travelers' food and garbage and attacking without provocation or warning when confronted.
A sarkastodon is 10 feet long (excluding the tail, which is about one-half to two-thirds as long as the body) and 6 feet tall at the shoulder, weighing around 1-½ tons.
Combat
A sarkastodon begins combat by swatting its foe with its forepaws, moving in to bite after knocking its foe down.
?(Trip (Ex): A sarkastodon that hits with a bite attack can attempt to trip its opponent (+16 check modifier) as a free action without making a touch attack or provoking an attack of opportunity. If the attempt fails, the opponent cannot react to trip the sarkastodon.)
I improved the land speed to 40 feet and the AC to 17 to match the dire bear. Are we going to give it a good Will save like a dire animal?
Base damage for the attacks?
Feat suggestions: Alertness, Endurance, INA bite, INA claw, Iron Will, Multiattack
(Drop Iron Will if we give it saves like a dire animal, and instead give something like Power Attack)