I'm not sure if this one is going to appear in the Pathfinder Bestiary or not; I didn't see it on the index. But it is in the 3.5 SRD, so there is a pretty good chance that a 'canon' version will be out sooner or later. But in the meantime...
HIPPOGRIFF
CR 2 (600 XP)
N LARGE MAGICAL BEAST
Init +2; Senses Darkvision 60 ft., low-light vision, scent; Perception +10
DEFENSE
AC 15; touch 11, flat-footed 13 (+2 Dex, -1 size, +4 natural)
hp 25 (3d10+9)
Fort +6, Ref +5, Will +2
OFFENSE
Speed 50 ft., Fy 100 ft. (average)
Melee 2 claw +6 (1d4+4), bite +1 (1d8+2)
Space 10 ft.; Reach 5 ft.
Special Attacks -
STATISTICS
Str 18, Dex 15, Con 16, Int 2, Wis 13, Cha 8
Base Atk +3; CMB +11; CMD 23
Feats: Dodge, Wingover
Skills: Fly +8, Perception +10; Racial Modifiers Perception +4
Languages: none
ECOLOGY
Environment Temperate hills
Organization Solitary, pair, or flight (7-12)
Treasure None
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A hippogriff is a fantastic creature with the foreparts and head of a giant eagle and the hindquarters of a horse. Hippogriffs can be ridden if tamed. They will usually attack pegasi, who are their natural enemies. Hippogriffs nest in rocky crags, and may swoop down on prey, carrying off a man-sized or smaller victim.1
Hippogriffs dive at their prey and strike with their clawed forelegs. When they cannot dive, they slash with claws and beak. Mated pairs and flights of these creatures attack in concert, diving repeatedly to drive away or kill intruders. Hippogriffs fight to the death to defend their nests and their hatchlings, which are prized as aerial mounts and fetch a handsome price in many civilized areas.
HIPPOGRIFF MOUNTS
A hippogriff requires training before it can bear a rider in combat.
Training a hippogriff requires six weeks of work and a DC 25 Handle Animal check. Riding a hippogriff requires an exotic saddle. A hippogriff can fight while carrying a rider, but the rider cannot also attack unless he or she succeeds on a Ride check.
Hippogriff eggs are worth 2,000 gp apiece on the open market, while young are worth 3,000 gp each. Professional trainers charge 1,000 gp to rear or train a hippogriff.
Carrying Capacity: A light load for a hippogriff is up to 300 pounds; a medium load, 301–600 pounds; and a heavy load, 601–900 pounds.
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1. Gygax, G. and Arneson, D. 1983. Dungeons and Dragons Expert Rulebook. Random House, Inc.