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Glossary L

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Lava is molten rock. It usually comes out of erupting volcanoes.

The Law of Superposition states that in a sequence of sedimentary rocks, the lowest layers are the oldest and the uppermost layers are the youngest.

This small two legged herbivore lived in the Early Cretaceous period. It could have been a sociable and lived in the forests of polar Australia. It is likely that it developed huge eyes to cope with the six month Antarctic darkness. It grew up to about 2 metres long, and weighed up to 10 kg.

Leedsichthys was a huge Jurassic fish up to 20 metres long, which used its large mouth to sift plankton from the water. It is named after Alfred Leeds, an amateur fossil collector who found its remains in clay quarries around Peterborough, England.

Joseph Leidy (1823-1891) was a US anatomist who named the first dinosaurs found in the U.S.A. He excavated the first American dinosaur, Hadrosaurus, in 1858. Leidy named Antrodemus (1870, perhaps Allosaurus), Aublysodon (1868), Deinodon (1856), Diplotomodon (1868), Hadrosaurus (the first nearly-complete dinosaur skeleton and first-known duck-billed dinosaur, 1858), Palaeoscincus (1856), Thespesius (1856), Trachodon (1856), and Troodon (1856). Leidy was also the first scientist to identify many extinct species of camels, horses, sloths, tigers, and rhinoceroses.

Leidysuchus (meaning: "Leidy's crocodile;" Leidy was a paleontologist) was a long-snouted crocodile that lived during the late Cretaceous Period. Fossils of this swamp-dwelling reptile have been found in North America.

Lemurs are large-eyed primates from Madagascar (an island off the eastern coast of Africa). Lemurs evolved about 50 million years ago.

Lepidodendron (also known as the "scale tree") was a giant club moss (a tree-like plant) whose long trunk had bark with a diamond-shaped pattern (the scars of old, dead branches that fell off). This ancient lycopod was over 130 ft (40 m) tall; the trunk was over 6 ft (1.8 m) in diameter. Lepidodendron lived in swampy areas during the Carboniferous Period (about 360 to 286 million years ago). It has spirally-arranged leaves that ended in cones. By the time the dinosaurs lived, the giant club mosses had died out and were replaced by smaller club mosses.

Lepidosaurs are a subgroup of reptiles which includes snakes and lizards.

Lepospondyls were small, common amphibians with very long, slim bodies (Lepospondyls superficially resembled salamanders or snakes). These extinct insectivores had a long skull with sharp teeth and weak limbs. They lived during the Middle Pennsylvanian (=late Carboniferous) through the late Permian period. Lepospondyls probably lived near the water so they could return to it to lay eggs. Lepospondyls included: the snake-likeAïstopods (e.g., Ophiderpeton and Phlegethontia), the newt-like Nectrideans (e.g., Diplocaulus and Keraterpeton), the varied Microsaurs (e.g., Microbranchis and Pantylus), Adelogyrinids, and Lysorophids.

Leptauchenia was a large, rare, herbivore mammal that browsed grasslands and woodlands. This extinct artiodactyl (even-toed hoofed mammal) lived during the Oligocene epoch in North America. It was a close relative of the more numerous oreodonts (the most common large hoofed herbivore mammal in North America during the Oligocene) and competed with them. Anatomically, Leptauchenia was similar to the oreodont Merycoidodon (which looked like a long-legged, long-bodied pig about 4.5 ft = 1.4 m long). Classification: Superorder Ungulata (hoofed mammals), Order Artiodactyla (even-toed ungulates), Suborder Tylopoda (oreodonts and camels)

(pronounced LEP-to-SER-ah-tops) Leptoceratops (meaning: "slim-horned face") was a primitive ceratopsian, a frilled, herding, quadrupedal, herbivore dinosaur. It was about 6 feet (1.8 m) long and had a horn on its beaked snout. It lived in what is now western North America during the late Cretaceous (68-65 million years ago). It was named by the fossil hunter Barnum Brown in 1914.

Leptocycas gracilis was a cycad (a primitive seed plant) that lived during the late Triassic Period. It was a palm-like tree with a long, woody trunk that lived in warm climates. This tree was about 4.8 ft (1.5 m) tall. Separate male and female plants exist (they are dioecious). This gymnosperm had long, divided leaves and produced large seed cones.

Herring-like in size and appearance, this fish lived in the Late Jurassic period, although fragmentary remains indicate earlier origins than this.

Leptopterygius (also known as Temnodontosaurus) was a late Ichthyosaur, an extinct marine reptile, not a dinosaur. It was about 30 feet (9 m) long and looked a bit like a modern-day dolphin (but it is not at all related to the dolphins). It had a torpedo-shaped body, a long, narrow, toothed snout, 4 long, narrow paddles, a fish-like tail, and a triangular dorsal fin. They were viviparous (they gave birth to live young). These fish-eaters lived in shallow seas over what is now Europe (Germany and England) during the late Jurassic Period. (Order Ichthyosauria, Family Leptopterygiidae)

(pronounced le-SOH-toh-SAWR-us) Lesothosaurus (meaning: "Lesotho (South Africa) lizard") was a very early ornithopod, a small, fast, bipedal, plant eating dinosaur. It lived during the early Jurassic Period.

Lewisuchus was a small, fast-moving genus of archosauromorphs (not a dinosaur, but another type of reptile, a thecodont). This quadruped had a four-chambered heart, large, powerful jaws and a long tail. Its legs were not sprawling (like those of most reptiles) but were columnar, like the dinosaurs. Lewisuchus lived during the Triassic Period. The type species is L. admixtus. Lewisuchus was named by Romer in 1972.

(pronounced lek-SOH-vee-SAWR-us) Lexovisaurus (meaning: "Lexovian lizard," for ancient Celtic people) was a plant-eating, stegosaurid dinosaur that was about 17 feet (5 m) long and weighed about 2000 kg. It has tall, thin armored plates along its back that may have been used for protection, as a display, or for temperature regulation. For protection, it also had 2 shoulder spines (3.75 feet = 1.1 m long and 10.5 inches = .275 m wide), and spikes on its tail (at least one pair, maybe more). This quadruped lived during the middle Jurassic Period, about 169 to 156 million years ago. Incomplete fossils have been found in England and France. The type species is L. durobrivenses. Lexovisaurus was named by Hoffstetter in 1957. Its name means "Lexovix lizard;" it was named after the Gallic people of Lyons, France.

The Lias epoch was the early part of the Jurassic Period, about 206 to 180 million years ago.

Libellulium was a large, ancient dragonfly that lived during the Jurassic period, roughly 150 million years ago. Libellulium body was about 57 mm long; it had a wingspan of 145 mm. Fossils of this long-extinct flying insect have been found in Solenhofen Limestone in Bavaria, Germany, Europe. Libellulium longilatum (the type species) was named by Germar in 1837.

Ligaments are tough threads or sheets of collagen (a protein) that support the joints between bones and muscles.

(pronounced LICK-hoh-lih-SAWR-us) Likhoelesaurus (named for the South African town Li Khole, South Africa, where the fossils were found) was a theropod dinosaur from the late Triassic Period, roughly 225 to 208 million years ago. This size of this meat-eater is unknown. It is known from only some 2.7 inch (70 mm) long teeth which were found in South Africa. Likhoelesaurus was named by Ellenberger in 1972. The type species is L. ingens. This genus is a nomen nudum, a genus which has been insufficiently described. Likhoelesaurus may be the same as Basutodon, whose teeth are similar.

(pronounced LIL-ee-en-STER-nus) Liliensternus (named to honor German paleontologist Hugo Rühle von Lilienstern (1882-1946)) was a meat-eating dinosaur, a theropod from the late Triassic Period, about 222 - 219 million years ago. This speedy, bipedal dinosaur had long, strong legs, short arms, a long neck, and ahead with a triangular hole in front of the eyes. It was about 16 ft (5 m) long. It had five-fingered hands; the 1st and 5th fingers were small. Liliensternus may have had a crest on its head (like its close relative, Dilophosaurus). Fossils have been found in Germany and France. The type species is L. liliensterni. Liliensternus was named by Welles in 1984.

A sedimentary rock composed primarily of calcium carbonate usually formed from the skeletons of marine micro-organisms and corals.