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The Maastrichtian age was the last part of the Cretaceous Period. It lasted from about 71 to 65 million years ago, at the very end of the Mesozoic Era. Many dinosuars existed during this age, but it ended with a major mass extinction (the K-T extinction).

Machairodus (meaning: "knife tooth") was a common saber-toothed cat that lived from about 15 million years ago until about 2 million years ago. Species of this scimitar cat have been found in Africa, Europe, Asia, and North America. This lion-sized meat-eating mammal had slender limbs and a short tail; the upper jaw canine teeth were large. Machairodus was named by Kaup in 1833. Classification: Family Felidae, Subfamily Machairodontinae, Genus Machairodus, many species.

(pronounced ma-KEER-oh-pro-SOH-pus) Machaeroprosopus (meaning: "knife face") was a phytosaur (not a dinosaur). This marine reptile had a thin, knife-like crest of its skull (hence its name). This crocodile-like animal had four short legs, a long tail, armored skin, sharp teeth in elongated jaws, and nostrils near the eyes. It lived during the late Triassic period. Fossils have been found in North America. Machaeroprosopus was named by Mehl in 1916; the type species is Machaeroprosopus validus (but the orginial speciemen has been lost).

Macroplata was a plesiosaur 15 feet (4.5 m) long with long, toothed jaws and a long neck. From England during the early Jurassic Period. It was not a dinosaur, but another type of extinct reptile.

Macrauchenia was an early hoofed mammal with a long neck; it may have had a long trunk. Macrauchenia was 10 feet ( 3 m) long; it had long legs, three-toed, rhino-like feet, and nostrils located between the eyes. This quadruped was an herbivore (a plant-eater). Macrauchenia lived during the Pleistocene. Fossils have been found in Argentina, South America. Classification: Class Mammalia (mammals), Order Litopterna (horse-like and camel-like mammals), Family Macraucheniidae.

The Earth's magnetic field is aligned with the north and south poles, and has reversed many times during geologic history. A fossil's magnetic orientation can give clues to its date.

Magyarosaurus was a dwarf titanosaurid sauropod, a long-necked, long-tailed, plant-eating dinosaur. It was 5 to 6 m long. Fossils have been found in Hungary and Romania. Magyarosaurus lived during the late Cretaceous Period. Magyarosaurus was named by the paleontologist von Huene in 1932; the type species is M. dacus (Nopcsa, 1915 - originally called Titanosaurus).

(pronounced MY-yah-SAWR-ah) Maiasaura (meaning: "good mother lizard") was a duck-billed dinosaur (a hadrosaur) that cared for its young. This plant-eater lived in herds during the late Cretaceous period, about 77 to 73 million years ago. Fossils of adults, juveniles, hatchlings, eggs, and nests have been found in Montana, USA. Maiasaura was named by paleontologists Jack Horner and R. Makela in 1979. The first dinosaur in space was Maiasaura peeblesaurum (the type species). A piece of bone from a baby Maiasaura and a Maiasaura eggshell were taken into space by astronaut Loren Acton on an 8-day NASA mission (Spacelab 2) in 1985. The historic Maiasaura fossils now reside at the Museum of the Rockies in Bozeman, Montana, USA.

(pronounced mah-JOONG-ah-SAWR-us) Majungasaurus (meaning: "Majunga [Madagascar] lizard") was a large, meat-eating dinosaur from the late Cretaceous Period, about 83-73 million years ago. Only a few fossils (some teeth and tail vertebrae) of this theropod have been found on the island of Madagascar. The type species is M. crenatissimus. Majungasaurus was named by Lavocat in 1955. This is a dubious genus; it may be the same as Majungatholus.

(pronounced mah-JOONG-ah-THOL-us) Majungatholus (meaning: "Majunga (Madagascar) dome" ) was a large, meat-eating dinosaur up to 30 feet (9 m) long with a small horn above its eyes. The skull was nearly 2.5 feet (60 cm) long. It was a theropod but its classification is not certain; it's possibly an abelisaurid. It was at the top of its local food chain 70 to 65 million years ago, during the late Cretaceous Period. Its fossil was found on the island of Madagascar, off the east coast of Africa. It is known from an incomplete adult specimen (skull and tail vertebrae) and an incomplete juvenile (partial skull, partial spine). It was named by Piveteau in 1926. Further work on Majungatholus was done by Sues and Taquet in 1979. The type species is M. atopus. It used to be thought to a pachycephalosaurid.

(pronounced mah-LAA-we-SAWR-us) Malawisaurus (meaning: "Malawi lizard") was a huge, plant-eating dinosaur that lived during the early Cretaceous period (roughly 140 million to 100 million years ago). This moderately-sized titanosaurid sauropod was about 35 feet (10.5 m) long. It had a long neck, a long tail, bulky body, and a small head (it was closely related to Janenschia). It may have had some armored plates on its back. An incomplete fossils was found in the Zambesi Valley, Malawi, Africa (Malawisaurus is the oldest-known titanosaur from Africa). Malawisaurus was named by paleontologists Louis L. Jacobs, Winkler, Downs, and Elizaneth M. Gomani in 1993. The type species is M. dixeyi, (Haughton, 1928), and was originally called Gigantosaurus dixeyi.

Evgenii Aleksandrovich Maleev (1915-1966) was a Russian paleontologist who named the dinosaur genera Talirurus (1952), Tarbosaurus (1955), and Therizinosaurus (1954); he also named the family Therizinosauridae. The dinosaurs Maleevosaurus (Pickering, 1984) and Maleevus (Tumanova, 1987) were named by to honor Maleev.

(pronounded mahl-YAY-ev-oh-SAWR-us) Maleevosaurus (meaning: "Maleev's lizard" named to honor the Russian paleontologist E. A. Maleev) was a large meat-eating dinosaur, a tyrannosaurid that lived during the late Cretaceous period. Maleevosaurus was found in Mongolia and named by Pickering in 1984. The type species is M. novojilovi. Maleevosaurus may be the the same as Tyrannosaurus bataar.

(pronounded mahl-YAY-ev--us) Maleevus (meaning: "Maleev's one" named to honor the Russian paleontologist E. A. Maleev) was a large plant-eating dinosaur, an ankylosaurid ankylosaur that lived during the late Cretaceous period, about 99 to 90 million years ago. Maleevus (only a partial skull) was found in Mongolia and named by Tumanova in 1987. The type species is M. disparoserratus (originally called Syrmosaurus, and named by Maleev, in 1952).

The Malm epoch was the late (or upper) part of the Jurassic Period, about 159 to 144 million years

(pronounced mah-MEHN-chee-SAWR-us) Mamenchisaurus (meaning: "Mamenchi (China) lizard" ) was a long-necked, long-tailed, quadrupedal, plant-eating sauropod from the late Jurassic Period, about 156 million to 145 million years ago. It was about 70 feet (21 m) long. Mamenchisaurus had the longest neck of any known dinosaur, about 46 feet (14 m). It had 19 vertebrae in its neck, more than any other known dinosaur. Mamenchisaurus was named by Chung Chien Young in 1954. Fossils have been found in China. Mamenchisaurus may be closely related to Diplodocus or Camarasaurus. The type species is M. constructus.

A mammal is a vertebrate which can regulate its body temperature, has hair on its body, and mostly bears live young. It provide these with milk from mammary glands.

Mammoths (genus name Mammuthus) are extinct herbivore mammals that had long, dense hair and underfur, long tusks, a long proboscis (nose), large ears. They lived throughout the world. They lived from about 2 million years ago to 9,000 years ago, millions of years after the dinosaurs went extinct. They are closely related to modern-day Indian elephants. Some tusks were straight, some were curved; the longest were up to 13 feet (4 m) long. The tusks were used in mating rituals, for protection, and for digging in the snow for food. Much of our knowledge of mammoths is from cave drawings and from mummified mammoths found in Siberian ice.

(pronounced MAN-dah-SOOK-us) Mandasuchus (meaning: "Manda crocodile" the Manda Formation, Tanzania, is where the fossil was found) was a rauisuchian (large-skulled archosaurs that may have been ancestors of dinosaurs) It was not a dinosaur. It lived during the middle Triassic Period, roughly 220 million years ago. Fossils have been found in Tanzania, in east Africa. This fast-runner was a quadruped about 8 feet (2.5 m) long; the rear legs were slightly longer than the front legs. It may have been the fastest reptile of its time. This meat-eater had a long tail, strong back (with 24 vertebrae between the head and hips), large, powerful jaws and sharp teeth. Mandasuchus was named by Charig in 1976.

(pronounced MAN-dah-bul) The mandible is the lower jaw.

The Manicouagan impact structure is the remnants of an impact that occurred about 200 million years ago. It is a ring of shattered rock (70 km across) thats surrounds an area of rock that was melted by the tremendous impact (and then solidified). The Manicouagan impact structure is located in northern Quebec, Canada. This impact resulted from a 10 km diameter asteroid and may have been responsible for the mass extinction that occurred at the end of the Triassic Period.

Maniraptors are a group of bird-like animals, including Dromaeosaurs, Oviraptors, Troodontids, Therizinosaurs, and Aves (birds). Maniraptors are closer to birds than to Ornithomimus. Manirators have birds as a more recent ancestor than Ornithomimus.

Gideon A. Mantell (1790-1852) was a British fossil hunter, one of the first in the world. He named Hylaeosaurus (1833), Iguanodon (1825), and Pelorosaurus (1850). Mary Ann Mantell, his wife, is commonly thought to have found the first Iguanodon tooth in 1822; there is no substantiation to this story, however.

Manus is the scientific term for the hand (or forefoot) of a vertebrate animal.