A B C D E F G H I J K L M N O P Q R S T U V W X Y Z Appendix

Rahonavis
Taxon: possibly Theropoda
Name means: “menace from the clouds bird”
Pronounced: rah-HOON-a-vis
Length: Small
Time: Late Cretaceous, c. 83.5 mya
Place: Madagascar

Named in 1998, this mysterious creature demonstrates similarities to both prehistoric birds and the swift, deadly dromaosaurid dinosaurs. Some experts suggest that it was a predatory dromaeosaur, equipped with the infamous slashing claw on the second toe of its foot. Others point out its very birdlike qualities, including a pubis bone with skeletal elements similar to ones that aid modern birds in ventilating their lungs. What appear to be quill or feather attachment marks in the fossilized forearms further substantiate the theory that Rahonavis was an avian. About the size of a crow, Rahonavis was slightly larger than Archaeopteryx.

Rapator
Taxon: Theropoda
name means: “plunderer”
pronounced: ruh-PAY-tor
Length: about 30 ft (9 m)
time: Early Cretaceous
place: Australia

This large but little-known Australian carnivore is known only from a unusual, knobbed toe bone from the flat of the foot. Named in 1932, Rapator is estimated to have been about the size of the fierce Allosaurus.

Rayososaurus
Taxon: Sauropoda
Name means: “Rayoso lizard,” for the Rayoso Formation
Pronounced: rie-YOH-so-SAW-rus
Length: Large
Time: Early Cretaceous, 112 – 99 mya
Place: Argentina

This long-necked sauropod, named in 1996, may actually be a specimen of the very similar Rebachisaurus.

Rebbachisaurus
Taxon: Sauropoda
Name means: “Rebbach lizard” or “Ait Rebbach lizard”
Pronounced: re-BACH-i-SAW-rus
Length: 68 ft (20 m)
Time: Late Cretaceous, 113 – 97.5 mya
Place: Morocco, Niger (Africa)

This huge sauropod was found in Morocco, North Africa. A massive, four-legged plant-eating browser with a small head, a long, graceful neck and a whiplike tail, Rebbachisaurus is distinguished from other sauropods by its unusually arched back. Some scientists speculate that it may even have carried a sail or fin-like extension on its spine. The discovery of Rayososaurus, a South American sauropod which many paleontologists believe is actually another Rebbachisaurus specimen, supports the theory that there was a land-bridge connection between the two land masses during the Late Cretaceous. Rebbachisaurus was named in 1954.

Regnosaurus
Taxon: probably Stegosauridae
pronounced: REG-nuh-SAW-rus
Length: Moderate
time: Early Cretaceous
place: England

Named for an ancient tribe that lived in the County of Sussex in England where it was found, this poorly-preserved dinosaur was at first thought to be an armored ankylosaur. It was later reclassified as a sauropod. Recently, Regnosaurus has been redefined as a stegosaur with a short, boxy head and spoon-shaped teeth. Its front and hind legs were nearly equal in length. Regnosaurus was named by Mantell in 1848.

Revueltosaurus
Taxon: possibly Ornithischia
name means: “Revuelto Creek Lizard”
pronounced: REV-yoo-EL-tuh-SAW-rus
Length: Small
time: Late Triassic
place: New Mexico

Named in 1989 based only on fossilized teeth, this strange creature may be either an herbivorous ornithischian or a non-dinosaurian lizard of the Late Triassic. Without more to study than an inciscor-like tooth and several others to go on, it is tough to know for sure.

Rhabdodon
Taxon: Ornithopoda
Name means: “fluted tooth”
Pronounced: RAB-duh-don
Length: 14.5 ft (4 m)
Time: Late Cretaceous, 83 – 65 mya
Place: France, Romania, Austria, Hungary

This two-legged plant-eater was named for its grooved or fluted teeth in 1869. One of the latest iguanodontians, Rhabdodon seems to have been similar to Camptosaurus. Like other iguanodontids, this was an anatomically more primitive hadrosaur relative with powerful spikes on its thumbs.

Rhoetosaurus
Taxon: Sauropoda Cetiosauridae\
Name means: “Rhoetus’ lizard”
Pronounced: ROH-tuh-SAW-rus
Length: 39 ft (12 m)
Time: Early Jurassic, c. 181 – 175 mya
Place: Australia

Named for Rhoetus, a giant from Greek and Roman mythology, this long-necked, plant-eating sauropod had a boxy head, spoon-shaped teeth, and front and back legs of nearly the same length. Its tail was more rigid than those of most sauropods, especially at the base. Its thigh bone alone was about five feet long. Rhoetosaurus was named in 1925.

Ricardoestesia
Taxon: Theropoda
Name means: “For Richard Estes”
Pronounced: ri-KAHR-doh-es-TEE-zee-uh
Length: about 6.6 ft (2 m)
Time: Late Cretaceous, 83 – 70 mya
Place: Alberta, Wyoming

Only a long, slender section of lower jaw identifies this small meat-eating dinosaur from Alberta and Wyoming. Ricardoestesia, named for paleontologist Richard Estes in 1990, was originally thought to be the same animal as Chirostenotes, but is now a classification puzzle due to a lack of descriptive fossil material. Some baby teeth attributed to Paronychodon may, in fact, belong to Richardoestesia instead.

Rioarribasaurus
Taxon: Ceratosauria or Coelophysoidea
Name means: “Rio Arriba lizard”
Pronounced: REE-oh-uh-REE-buh-SAW-rus
Length: 8 – 10 ft (2.5 – 3 m)
Time: Triassic, c. 220 mya
Place: New Mexico

Because the original fossil material used to describe Coelophysis was so fragmentary and poorly-preserved, some paleontologists felt that the hundreds of skeletons found at Ghost Ranch in New Mexico could not be attributed to that slender, meat-eating species with certainty. The name “Rioarribasaurus” was proposed as an alternate genus name for the Ghost Ranch bonebed dinosaurs, which were discovered by Edwin H. Colbert in 1947. Although the debate over whether to rename those specimens continues, the International Code of Zoological Nomenclature recently ruled in favor of retaining the name Coelophysis for the Ghost Ranch theropods. “Rioarribasaurus,” therefore, is presently a scientifically invalid name.

Riojasaurus
Taxon: Prosauropoda
Name means: “La Rioja lizard”
Pronounced: ree-oh-hah-SAW-rus
Length: 36 ft (11 m)
Time: Late Triassic, 225 – 219 mya
Place: Argentina

One of the earliest large plant-eating dinosaurs, this prosauropod was found in Argentina's La Rioja Province. It walked on all fours, could probably stand on two to feed, and had a long, slender neck and a small skull. Its limbs and tail were large and robust. Riojasaurus was named in 1969.