Found 'em! Judging by the stats, I wrote up the dire rhea back in the 3.0 days. They appeared in
Bride of a Portable Hole Full of Beer.
DIRE RHEA
Large Animal
Hit Dice: ..................3d8+6 (19 hp)
Initiative: ................+4 (Dex)
Speed: .....................50 ft.
AC: ........................17 (-1 size, +4 Dex, +4 natural)
Attacks: ...................Claw +5 melee, beak peck +0 melee
Damage: ....................Claw 1d6+2, beak peck 1d3+1
Face/Reach: ................5 ft. by 5 ft./10 ft.
Special Qualities: .........Sprint
Saves: .....................Fort +3, Ref +7, Will +2
Abilities: .................Str 15, Dex 19, Con 14, Int 2, Wis 12, Cha 10
Skills: ....................Jump +3, Listen +6, Spot +7
Feats: .....................Weapon Finesse (claw, beak peck)
Climate/Terrain: ...........Warm and temperate grasslands
Organization: ..............Solitary or flock (2-6)
Challenge Rating: ..........2
Treasure: ..................Nil
Alignment: .................Always neutral
Advancement Range: .........4-6 HD (Large); 7-9 HD (Huge)
Ostrich-like in build, dire rheas are large, flightless birds that stand some 10-12 feet tall. They are known for their drab brown coloration, although it isn't unknown for a dire rhea to have streaks of green running through its drooping feathers.
Dire rheas have three clawed toes on each powerful, armor-plated leg.
These creatures are known for their sudden bursts of speed, but can also maintain a healthy pace for quite a long time. One could say that while dire rheas have mastered "the runs," they are quite adept at "the trots" as well.
Dire rheas are omnivorous, supplementing their largely vegetarian diet with the occasional small mammal or lizard. Oddly, many seem to have a craving for fish, crustaceans, and other river creatures, and often go splashing around along riverbanks attacking such prey. In fact, it's often "something in the water" that directly results in a dire
rhea attack.
During the mating season, the males - often much larger than the females - become very aggressive, and may attack creatures significantly larger than their standard prey. When conditions are right, nobody's safe from the dire rhea!
Combat
A dire rhea frequently strikes without warning, often at the most inopportune time. After chasing down its intended victim, it strikes out with a clawed foot and pecks with its sharp beak. After it has slain and devoured its prey, the dire rhea spends considerable effort grooming itself, wiping any traces of blood and viscera from its beak by rubbing its face against its feathery wings. Immediately after a dire rhea attack, there is often quite a bit of wiping!
Sprint (Ex): Once an hour, a dire rhea can take a charge action to move ten times its normal speed (500 feet). Such violent surges forward prompt some sages to refer to these creatures as "explosive dire rheas."
Training a Dire Rhea
Training a dire rhea as a riding mount requires a successful Handle Animal check (DC 18 for a young creature - called a "squirt" - or DC 25 for an adult) and that the creature be willing. Dire rheas mature in about two years.
Trainers can reduce the DC by 5 and the rearing time by one-half by using a magical bridle enchanted for this purpose.
Dire rhea eggs are worth 100 gp apiece on the open market, while squirts are valued at 300 gp each. Professional trainers (those willing to muck about with dire rheas in the first place) charge 500 gp to rear or train a dire rhea.
Riding a trained dire rhea requires an exotic saddle, and most people dislike sitting on a dire rhea without one in any case. A dire rhea can fight while carrying a rider, but the rider cannot also attack unless he or she succeeds at a Ride check (see the Ride skill in Core Rulebook I).
Carrying Capacity: A light load for a dire rhea is up to 132 pounds; a medium load, 133-266 pounds; and a heavy load, 267-400 pounds.
(Incidentally, I was also responsible for the Cyclopean Breech Serpent entry and the "Magic WeaPuns" article in the PDF.)
Johnathan