ZoomDinosaurs.com Dinosaur and Paleontology Dictionary

DEATH STAR THEORY The Death Star Theory refers to the fact that mass extinctions are periodic, and may be caused by the Earth's passing through a cloud of comets (the Oort cloud) every 26 million years. Some people have hypothesized that there is a yet-to-be-discovered dark star or perhaps a planet (called, appropriately enough, Nemesis) orbiting in the outer reaches of our solar system. This body disrupts the Oort cloud (once every 26 million years), sending comets into the inner parts of the solar system, some of which hit Earth and cause mass extinctions.

DEINOCHEIRUS (pronounced DINE-oh-KIE-rus) Deinocheirus (meaning "terrible hand") was a large, long-legged, bipedal, meat-eating, big-eyed, bird-like dinosaur from the late Cretaceous period, about 70 million years ago. This Coelurosaurid Ornithomimosaur (ostrich-mimic) theropod was among the fastest of the dinosaurs, perhaps runing at 40-50 mph. Deinocheirus was about 23-38 ft (7-12 m) long, weighing reoughly 9000 kg. It had a toothless, beaked mouth. An incomplete fossil was found in Mongolia. Only two huge arm bones were found. These arms were 8 ft (2.5m) long and had 10-inch (25.5-cm) long claws. The type species is D. mirificus. Deinocheirus was named by Osmólska & Roniewicz in 1970.

DEINODON (pronounced DINE-oh-don ) Deinodon (meaning "terrible tooth") was a meat-eating dinosaur from the late Cretaceous period. This Coelurosaurid theropod is only known from a dozen large, fossilized teeth collected by Dr. F. V. Hayden by the Judith River in Montana, USA. Deinodon was named by paleontologist J. Leidy in 1856. Deinodon is a dubious genus [nomen dubium]. It may be the same genus as Gorgosaurus or Albertosaurus.

DEINOGALERIX Deinogalerix (meaning "terrible hedgehog") was an ancient hedgehog that lived during the middle Mocene period (about 15 million years ago). This insect-eater had hair on its body, unlike modern hedgehogs, which have modified hairs that form spines. Deinogalerix is the largest-known hedgehog; it was about 2 feet (60 cm) long and had jaws about 8 inches (20 cm) long. This long-extinct mammal had a long snout, sharp teeth, short legs, and a long tail. Fossils have been found in caves in Italy. Deinogalerix was named by M. Freudenthal in 1973.

DEINONYCHOSAURS Deinonychosaurs (also called "raptors") were advanced theropod dinosaurs. These fierce predators had a long, sharp, sickle-shaped claw on each foot (on the second toe). Some of the Deinonychosauria included Deinonychus, Utahraptor, Velociraptor, Pyroraptor, Saurornitholestes, etc.

DEINONYCHUS (pronounced die-NON-ni-kus) Deinonychus was a killer dinosaur, a dromaeosaurid, from the Cretaceous period, about 119 to 93 million years ago. This intelligent, bipedal, meat-eater was about 10 feet (3 m) long, weighed up to 175 pounds (80 kg), and had a 5 inch (13 cm) long, retractible, sickle-shaped claw on each middle toe. Its femur (thigh bone) was 31 cm long. It may have weighed 110-165 pounds (50-75 kg). Fossils (8 skeletons) have been found in Montana, Utah, and Wyoming, USA. It was named by paleontologist J. Ostrom in 1969. The type species is D. antirrhopus.

DEINOS Deinos is Greek for "fearfully great or terrible."

DEINOSUCHUS (pronounced die-no-SUE-kus) Deinosuchus (meaning "terrible crocodile") was the largest crocodylian (a reptile but not a dinosaur), growing up to 30 feet (9 meters) long and weighing perhaps 5,500 - 11,000 pounds (2,500 - 5,000 kg). It lived during the late Cretaceous period (about 85 to 66 million years ago). This carnivore (meat-eater) lived on the shores of the large shallow sea (the Tethys Sea) that covered much of North America, eating fish and perhaps some dinosaurs. Very few Deinosuchus fossils have been found.

DELTADROMEUS (pronounced DEL-ta-DROME-ee-us) Deltadromeus (meaning "delta runner" ) was a speedy, bipedal, meat-eating dinosaur (an early coelurosaur). This theropod was about 26 feet (8 m) long and dates from the late Cretaceous period. A partial skeleton was found in the Kem Kem region of Morocco, North Africa, by Gabrielle Lyon in 1995. It was named by paleontologists Sereno, Duthiel, Iarochene, Larsson, Lyon, Magwene, Sidor, Varicchio, and Wilson in 1996. The type species is Deltadromeus agilis.

DELTASAURUS (pronounced DEL-tah-SAWR-us) Deltasaurus (meaning "river delta lizard") was an early amphibian (NOT a dinosaur). This extinct quadrupedal carnivore had very good hearing in the air. Deltasaurus was named by Cosgriff in 1965. Fossils have been found in Australia. Classification: Order Temnospondyli, Superfamily Rhytidosteoidea, Family Rhytidosteidae.

DELTATHERIDIUM (pronounced DEL-tah-ther-ID-ee-um) Deltatheridium was an early mammal from the late Cretaceous period, about 80 million years ago. This opossum-like quadruped was about 6 inches (15 cm) long and had a long tail. Its had sharp canine teeth and its cheek teeth were wide with triangular crowns. Deltatheridium was an insectivore that may have also eaten small reptiles and perhaps scavenged. Deltatheridium had characteristics of a very early marsupial (pouched mammal), and was a possible kangaroo ancestor. Fossils have been found in Mongolia.

DENTARY The dentary is the main bone of the lower jaw; it holds the lower teeth.

DENTICLES Denticles are small, pointed projections on the teeth of some dinosaurs.

DENVERSAURUS (pronounced DEN-ver-SAWR-us) Denversaurus (meaning "Denver lizard") is a doubtful genus; this plated, quadrupedal plant-eater (an ankylosaur) is probably probably Edmontonia. Denver refers to the Denver Museum of Natural History, where the fossil specimen was stored before it was identified. It was named by Robert Bakker in 1988.

DEPOSIT A deposit is a natural accumulation of something, like minerals or fossils.

DERMAL BONE A dermal bone is a bone that forms within an organism's skin. These bones function as protective armor.

DERMODACTYLUS (pronounced DER-mo-DAK-til-us) Dermodactylus (meaning "skin finger") was a pterodactyloid pterosaur, a flying reptile from the late Jurassic period, about 153 to 144 million years ago. Dermodactylus was about 3 feet ( 1m) long. Dermodactylus was named by Othniel Marsh in 1881; the type species is D. montanus. Dermodactylus is a dubious genus. Fragmentary fossils, only wing metacarpal (finger) fragments, have been found in Wyoming, USA.

DESMATOSUCHUS (pronounced des-mat-oh-SUE-kus) Desmatosuchus (meaning "link crocodile") was a ancient armored aetosaur (it was a reptile but not a dinosaur) that had spines running along its body. The spines were up to 18 inches (45 cm) long (the longest spines were on the shoulders). It superficially resembled a crocodile with spikes, but had a much shorter, beak-like snout. It was about 16 feet (5 meters) long. This armadillo-like animal had a bulky body, four short legs, a long tail, and bony armor on its back, tail, and part of its belly. It was an herbivore (plant-eater) that had weak, peg-shaped teeth. Desmatosuchus lived during the late Triassic period (roughly 230 million years ago). Fossils have been found in Texas, USA. Desmatosuchus was named by Case in 1920. Classification: class Reptilia (reptiles), infraclass Archosauromorpha, family Stagenolepididae, genus Desmatosuchus, type species D. haploceros.

DEUTEROSAUROPODOPUS (pronounced DOOT-er-oh-sawr-oh-POD-oh-pus) Deuterosauropodopus (meaning "Second sauropod foot") was a sauropod dinosaur from the early Jurassic period known only from fossilized footprints. It was a long-necked, long-tailed plant-eater. It had nail-like claws on its feet and and an enlarged claw on each big toe. The fossil footprints were found near Lesotho, South Africa may belong to the sauropod Vulcanodon.

DEVONIAN PERIOD The Devonian Period is sometimes called the "Age of Fishes" because fish became adundant and diverse during this time, 408 to 360 million years ago (mya). Land plants were also doing very well. The first amphibians appeared during the Devonian. The first tetrapods appeared toward the end of this period. The first sharks, bony fish, and ammonoids also evolved. Coral reefs, brachiopods, and crinoids were abundant. New insects, like springtails, appeared. Towards the end of this period was a mass extinction (345 mya) that wiped out 30% of all animal families); it was probably caused by glaciation or meteorite impact.

DEWCLAW A dewclaw is a functionless claw that doesn't hit the ground. Some dinosaurs had dewclaws.

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