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Dinosaur and Paleontology Dictionary
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

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R


RADIOISOTOPE DATING

Radioisotope dating of igneous rock layers is used to find out how old the rock is (when the igneous rock formed). One way of dating fossils is by dating bracketing layers of igneous rock.


RADIUS

The radius is one of the two arm bones (the other is the ulna).


RAHONAVIS

(pronounced rah-hoo-NAY-vis) Rahonavis (meaning "Cloud-menace bird") was a primitive bird/dinosaur with sickle-like claws on its feet. It was half-way between a dromaeosaurid dinosaur and a bird. It lived during the late Cretaceous period. This carnivore was about the size of a raven. Fossils have been found in Madagascar. The type species is R. ostromi. Rahonavis was named by Forster, Sampson, Chiappe, and Krause in 1998.


RAJASAURUS

(pronounced rah-hoo-NAY-vis) Rajasaurus narmadensis (meaning "regal dinosaur from the Narmada") was a heavy-boned meat-eating dinosaur (an abelisaur) that lived during the late Cretaceous period. This carnivore was about 9 meters long. Fossils have been found in the Narmada River region of India. The type species is R. narmadensis. Rahonavis was named by Wilson, Sereno, Srivastava, Bhatt, Khosla & Sahni in 2003; the fossils were found in 1983 by Suresh Srivastava and Ashok Sahni.


RAMAPITHECUS

Ramapithecus (meaning "Rama's ape") was an arboreal (tree-living) primate that was probably an ancestor of modern-day orangutans. This extinct ape lived roughly 14 to 8 million years ago, during the Miocene epoch. The first fossils were found in 1932 by Edward G. Lewis. Fossils have been discovered in northern India, Pakistan, and eastern Africa. Until a very primitive, complete jaw was found in 1976, Ramapithecus was thought to have been an ancestor of man.
RANCHO LA BREA TAR PITS
The Rancho La Brea Tar Pits are a series of over 100 asphalt pits located in southern California, USA ("brea" means "tar" in Spanish). These tar pits contain many animal bones, including Ice Age fossils. Over 650 species of Pleistocene Epoch plants and animals have been found and identified at La Brea (dating from about 10,000 to 40,000 years ago), including many mammoths, mastodons, saber-toothed cats (including Smilodon fatalis), dire wolves (Canis dirus), giant sloths (Glossotherium harlani), ground sloths, bison, a western horse, the short-faced bear (Arctodus simus), rodents, rabbits, birds, turtles, lizards, insects, mollusks, and many other animals and plants. One ancient human skeleton was found in the La Brea pits (about 17 bones from a woman who dates from about 9,000 years ago). Tar pits are pools of gooey asphalt that are created when crude oil seeps up from deep inside the Earth through a crack (called a fissure). The less dense elements of the crude oil evaporate, leaving a deep, conical deposit of asphalt (a very sticky mess). Water pools on the tar, attracting thirsty animals. As animals get stuck in the tar, predators are attracted to the trapped animal, and then they get stuck in the asphalt too. The animals' bones, teeth, and other hard parts are well-preserved in this environment (but they turn brown from the asphalt).


RAPATOR

(pronounced ruh-PAY-tor) Rapator (meaning "plunderer") was a theropod dinosaur that lived during the early Cretaceous period, from 113 -97.5 million years ago. This bipedal carnivore was very roughly 30 ft (9 m) long. Fossils have been found in Australia. The type species is R. ornitholestoides. Rapator was named by von Huene in 1932. This is a doubtful genus since so little fossils material was found (just a toe bone); it may be the same as Walgettosuchus.


RAPETOSAURUS

Rapetosaurus (meaning "mischievous giant lizard") was a sauropod long-necked, plant-eating dinosaur that lived during the late Cretaceous period, about 70-65 million years ago. This quadruped was roughly 50 ft (15 m) long. Fossils have been found in Madagascar, off the southeastern coast of Africa. The type species is R. krausei. Rapetosaurus was named by Rogers and Forster, 2001.

"RAPTOR"

(pronounced RAP-tor) "Raptor" is an informal term that some people use to refer to the Dromaeosaurid dinosaurs, like Velociraptor, Utahraptor, Deinonychus, and others. These speedy, intelligent, bird-like theropods were fierce killers that had a long, sickle-like claw on each foot. They lived during the Cretaceous period.

Raptorex

(pronounced RAP-tor-ex) Raptorex kriegsteini was a small, meat-eating dinosaur, a 3 m long version of T. rex. This dinosaur weighed about as much as an adult human. Fossils were found in northeastern northeastern China. Like T. rex, Raptorex has a large skull, powerful jaws and teeth, small arms, big, clawed feet, and strong, muscular legs. This theropod dinosaur lived during the Cretaceous period, roughly 130 million years ago and long before T. rex evolved (T. rex lived roughly 68-65 mya).


RAUISUCHIAN

Rauisuchians (meaning "Rau's crocodiles") were large-skulled archosaurs (not dinosaurs) from the mid to late Triassic period. These meat-eating reptiles had powerful jaws and were the top predators of their time, but went extinct at the end of the Triassic. They are frequently described as animals "trying to become dinosaurs." They were generally from 7 to 15 ft (2 to 5 m) long, but a few were larger. Rauisuchians were mostly quadrupedal, but some may have been bipedal. Some had armored plates. Fossils have been found in North and South America, Europe, India, China and Africa. Some Rauisuchians include Saurosuchus (the biggest), Ticinosuchus, Dongusuchus, Energosuchus, Fasolasuchus, Mandasuchus, and many others.


RAY-FINNED FISH

Ray-finned fish (class Actinopterygii) are the largest group of fish. These bony fish evolved during the very end of the Silurian, about 408 million years ago. These fish dominate the seas today. Sharks are not ray-finned fish.


RAYOSOSAURUS

(pronounced rie-YOH-so-SAWR-us) Rayososaurus (meaning "Rayoso [A Formation in Argentina] lizard") was a large, diplodocid sauropod dinosaur from the early Cretaceous period, about 99 million years ago. This quadrupedal plant-eater had a whip-like tail, a long neck, a small head, clawed hind legs, a high-arched back, and a bulky body. Fossils have been found in Argentina. The type species is R. agrionensis. Rayososaurus was named by Bonaparte in 1995. This is a doubtful genus


REBBACHISAURUS

(pronounced re-BASH-eh-SAWR-us ) Rebbachisaurus (meaning "Rebbach-territory {in Morocco} lizard") was a large, diplodocid sauropod dinosaur from the early Cretaceous period, about 113 to 97.5 million years ago. This quadrupedal plant-eater had a whip-like tail, a long neck, a small head, clawed hind legs, a high-arched back, and a bulky body. It may have had a sail on its back. Rebbachisaurus was about 68 ft (20 m) long. Fossils have been found in Morocco and Niger, Africa. The type species is R. garasbae. Rebbachisaurus was named by Lavocat in 1954.


RECURVED TEETH

Recurved teeth are teeth that curve back towards the animal. This type of teeth make it very hard for prey to escape.

REGRESSION

Regression is the exposure of continental land as the sea level decreases, usually caused by increasing polar ice and glacier formation. Another causes is the local uplift of the continental land.

RELATIVE AGE DATING

Relative age dating seeks to determine the order in which events occurred. Compare with absolute age dating.
A cladogram of reptilia

Reptilia cladogram


REPTILE

Reptiles (meaning"to creep") are a group of animals that have scales (or modified scales), breathe air, and usually lay eggs. The term reptile is loosely defined in everyday English to mean scaly, cold-blooded, egg-laying animals. In cladistics (a way of classifying life forms), the reptiles are more stictly defined and include the descendants of the most recent common ancestor of the turtles, lepidosaurs (lizards, snakes, tuataras), and archosaurs (crocodilians, dinosaurs, and birds). The maintenance of body temperature (cold- vs. warm-blooded) is not a factor in this classification, but skull and egg structure are.


REVUELTOSAURUS

(pronounced re-VWELL-to-SAWR-us) Revueltosaurus (meaning "Revuelto ]Creek] lizard") is a poorly-known ornithischian dinosaur that lived during the late Triassic period, about 220 million years ago. Only fossil teeth of this bipedal plant-eater have been found in New Mexico and Arizona, USA. The type species is R. callenderi . Revueltosaurus was named by K. Padian in 1990; it was named for the Revuelto Creek in New Mexico, USA. This is a duious genus of dinosuar due to the sparsity of fossils.


RHABDODON

(pronounced RAB-doe-don) Rhabdodon (meaning "rod or fluted tooth") was a small, iguanodontid ornithopod dinosaur from the early Cretaceous period, about 83 to 65 million years ago. This bipedal plant-eater had a long tail, a short neck, a beaked head, and a bulky body. Rhabdodon was about 14.5 ft (4 m) long. Fossils have been found in Austria, France, Hungary, and Romania. The type species is R. priscus. Rhabdodon was named by Matheron in 1869.

RHAMPHORHYNCHUS

(pronounced (RAM-fo-RING-khus) Rhamphorhynchus (meaning "beak snout") was a pterosaur with a 5.75 feet (1.75 m) wide wingspan with long, narrow jaws, sharp teeth pointing outwards, and a diamond-shaped flap of skin at the end of the very long, pointed tail. This carnivore probably ate fish. It lived during the late Jurassic period and was not a dinosaur, but another type of extinct, flying reptile.


RHOETOSAURUS

(pronounced REET-oh-SAWR-us) Rhoetosaurus (meaning "Rhoetos' (mythological Greek giant) lizard") was a sauropod dinosaur from the middle Jurassic period, about 181 to 175 million years ago. This quadrupedal plant-eater had a long tail, a long neck, a small, box-like head, and a bulky body. Rhoetosaurus was about 40 ft (12 m) long. Fossils have been found in Queensland, Australia. The type species is R. brownei. Rhoetosaurus was named by Longman in 1925.


RHYNCHOSAURS

Rhynchosaurs (meaning "beaked lizard") were common quadrupedal, herbivorous, land-dwelling, archosauriform reptiles from the late Triassic period. These short, pig-like reptiles had tusks and beaks and were about 3.3 to 6.5 ft (1-2 m) long. Scaphonyx was a rhynchosaur.


RICARDOESTESIA

(pronounced ri-KARD-o-es-TEE-zee-ah) Ricardoestesia (named for Richard Estes) was a small coelurosaurid dinosaur from the late Cretaceous period, about 83 to 70 million years ago. This bipedal carnivore was about 6.5 ft (2 m) long and had a long, thin lower jaw. Fossils (mostly teeth and jaw) have been found in Alberta, Saskatchewan, Montana, and Wyoming. The type species is R. gilmorei. Rahonavis was named by Currie, Rigby, and Sloan in 1990.

RICH, THOMAS H.

Dr. Thomas H. Rich is an Australian paleontologist and author. Rich has unearthed many important finds in Victoria, Australia, Alaska, USA, and Patagonia, South America. He co-named (with his wife P. Vickers-Rich) the dinosaurs Leaellynasaura (1989) and Timimus(1994) (both named for his children), Atlascopcosaurus (1989), Qantassaurus (1999), Tehuelchesaurus (1999, also with Gimenez, Candúneo, Puerta, and Vacca), the important early Australian mammal Ausktribosphenos, and others.


RILEYASUCHUS

(pronounced RIE-lee-ah-SOOK-us) Rileyasuchus (meaning "H. Riley's crocodile") was an early theropod dinosaur from the late Triassic period. Fossils of this bipedal carnivore have been found in Europe. The type species is R. bristolensis. Rileyasuchus was named by Kuhn in 1961. It was originally known as Rileya, named by paleontologist von Huene in 1902.


RIOARRIBASAURUS

(pronounced REE-oh-ah-REE-bah-SAWR-us) Rioarribasaurus was a lightly-built, fast, theropod dinosaur. This bipedal, carnivore lived during the late Triassic period. This small ceratosaurian was about 10 feet (3 m) long. Hundreds of fossils were found at the Ghost Ranch in New Mexico, USA in 1947 by paleontologist Edwin H. Colbert. Rioarribasaurus and Coelophysis are similar dinosaurs (they may be the same).


RIOJASAURUS

(pronounced ree-OH-ha-SAWR-us) Riojasaurus was a prosauropod dinosaur, a quadrupedal, long-necked herbivore from the late Triassic and early Jurassic periods.


ROSTRAL BONE

The rostral bone is a bone found only in ceratopsian dinosaurs (like Triceratops, Styracosaurus, and Protoceratops). This bone was located at the tip of the upper jaw.


RUEHLEIA

Ruehleia (named to honor the German paleontologist Hugo Ruehle von Lilienstern (1882-1946)) was an early plant-eating dinosaur that lived during the late Triassic period (the late Norian). This plateosaurid prosauropod was found in Germany. Ruehleia was named by Galton in 2001; the type species is R. bedheimensis.


RUGOSE

Rugose means ridged, rough, or wrinkled.


RUMINANT

A ruminant is an animal that digests its food many times. This food is usually tough plant material like grasses. Ruminants include cows, sheep, antelopes, and camels.
RUSSELL, DALE A.
Dr. Dale Alan Russell is a vertebrate paleontologist and author. He is a Research Professor at North Carolina State University and Senior Curator of Paleontology at the North Carolina Museum of Natural Sciences. Russel has named the following dinosaurs: Alxasaurus (Russell and Dong, 1994), Archaeornithomimus (1972), Atlasaurus (Monbaron, Russell and Taquet, 1999), Cristatusaurus (Taquet and Russell, 1998), Daspletosaurus (1970), Dromiceiomimus (1972), Dyslocosaurus (McIntosh, Coombs and Russell, 1992), Lurdusaurus (Taquet and Russell, 1999), Sigilmassasaurus (Russell, 1996), and Sinornithoides (Russell and Dong, 1994). Russell has written many papers and books, including, "Odyssey in Time: The Dinosaurs of North America" 1989 and "Systematics and Morphology of American Mosasaurs" (1967). In 1971, Russell and the physicist Wallace Tucker published a paper (in the journal Nature) called "Supernovae and the extinction of the dinosaurs," which theorized that a supernova caused the K-T Extinction. This was the first theory to put the blame on an extra-terrestrial phenomenon.

RUTIODON

(pronounced ROO-tee-oh-don) Rutiodon (meaning "wrinkled tooth") was a phytosaur (not a dinosaur). This aquatic reptile had a long snout, four short legs, and a long tail; it looked a bit like a crocodile, but had nostrils near the eyes. This meat-eater went extinct at the end of the Triassic period. Like other phytosaurs, Rutiodon may have built nests and protected their eggs. Fossils (an incomplete skull whose teeth have strong vertical striations) have been found in North America. Rutiodon was named by Emmons in 1856.

ZoomDinosaurs.com
Dinosaur and Paleontology Dictionary
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

Click on an underlined word for more information on that subject.
If the dinosaur or paleontology term you are looking for is not in the dictionary, please e-mail us.

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