Here's the "desert lizard mount" I have IMC, you might want to use or adapt it:
ZEERESHI
Large Animal
Hit Dice: 4d8+8 (26 hp)
Initiative: +2
Speed: 60 ft. (12 squares)
Armor Class: 16 (–1 size, +2 Dex, +5 natural), touch 11, flat-footed 14
Base Attack/Grapple: +3/+11
Attack: Bite +6 melee (2d6+4)
Full Attack: Bite +6 melee (2d6+4) and 2 foreclaws +1 melee (1d6+2)
Space/Reach: 10 ft./5 ft.
Special Attacks: None
Special Qualities: scent
Saves: Fort +7, Ref +6, Will +2
Abilities: Str 19, Dex 15, Con 14, Int 2, Wis 12, Cha 10
Skills: Hide +8, Jump +26, Listen +10, Spot +10, Survival +10
Feats: Run, Track
Environment: Warm desert
Organization: Pack (3–6)
Challenge Rating: 2
Treasure: None
Alignment: Always neutral
Advancement: 5–8 HD (Large)
Level Adjustment: —
A Zeereshi, or Marrakeen War Lizard is a quadrepedal reptile, 6' at shoulder, dull tan along its back and flanks, with a much lighter shade of the same color on its underside. The body often has darker spots or stripes. Its tail extends straight out behind itself, held aloft by an intricate structure of bony supports, thus allowing it to run quickly. It weighs about 800 pounds.
Combat
A Zeeeshi uses a combination of speed, large teeth, and fore legs with ripping talons. In the wild it hunts in packs by running at prey (+2 charge bonus) and biting them, then biting & clawing with talons. A Zeereshi has a relatively large brain for a dinosaur, and wild packs hunt with cunning tactics. Most Zeereshi are domesticated, though.
Skills: A Zeereshi has a +8 racial bonus on Hide, Jump, Listen, Spot, and Survival checks.