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Macroplata it was a plesiosaur 15 feet (4.5 m) long with long, toothed jaws and a stretched neck.

Magnetic Field it is aligned with the north and south poles, and has inverted many times throughout geologic history. A fossil's magnetic direction can give clues to its date.

Magyarosaurus it was a dwarf titanosaurid sauropod, a long-necked, long-tailed, plant-eating dinosaur.

Maiasaura was a duck-billed dinosaur (a hadrosaur) that cared for its young.

Majungasaurus was a big, meat-eating dinosaur from the late Cretaceous era, about 83-73 million years before.

Majungatholus was a bulky, meat-eating dinosaur up to 30 feet (9 m) long with a small horn above its eyes.

Majungatholus Dinosaur of the infraorder Pachycephalosauria, that go down in history as the ugliest dinosaur always to walk the Earth (Cretaeceous).
Malawisaurus was a enormous, plant-eating dinosaur that lived during the early Cretaceous period (approximately 140 million to 100 million years ago).

Maleevus was a large plant-eating dinosaur, an ankylosaurid ankylosaur that lived during the late Cretaceous period

Mamenchisaurus the longest-necked dinosaur that eternally lived.

Mammals are furry warm-blooded animals that feed their young with milk. Mammals evolved throughout the Triassic period.

Mammoths are extinct herbivorous mammals that had long, thick hair and under fur, long tusk, a long proboscis (nose), and large ears.

Marasuchus was a dinosaur-like reptile that was an ancestor of the dinosaurs) that lived during the middle Triassic era, about 230 million years back.

Marginocephalia Suborder which is classified addicted to ceratopsians and pachycephalosaurs (Cretaecous).

Marginocephalians  are a group of Ornithischian (bird-hipped) dinosaurs that have a characteristic skull structure

Mass extinction it is the process in which large numbers of species die out rapidly. The dinosaurs (and many other species) became destroyed, perhaps because of an asteroid that hit the Earth.

Massospondylus was an herbivorous dinosaur from the early Jurassic period, about 205-194 million years before.

Megalancosaurus was a reptile (a prolacertiform archosauromorph, not a dinosaur) from the late Triassic era

Megalosauripus is a dinosaur which is recognized only from its fossilized, three-toed footprints; it is an ichnogenus

Megalosaurus it was a large dinosaur that lived throughout the Jurassic period. This bipedal meat eater was upto about 26 ft (8 m) long.

Megaraptor  is a newly revealed, 90 million year old dinosaur that had a 14 inch (34 cm) long sickle-like claw on the second toe of each long, thin foot.

Mesozoic Era occurred from 248-65 million years ago. It is classified into the Triassic, Jurassic, and Cretaceous Periods. Dinosaurs, mammals and flowering plants evolved throughout the Mesozoic Era.

Mesozoic period among 248 and 65 MYA, to which the Triassic, the Jurassic and the Cretaecous belong.

Meteor an interplanetary rock or dust particles form a band of light in the night sky sometimes called a shooting star. Most burn up before beating the Earth.

Microceratops was a very little, frilled, plant-eating dinosaur only 30 inches long (76 cm).

Microvenator was a minute, fast-moving, long-legged, meat-eating, bipedal dinosaur about 4 ft. (1.2 m) long, weighing possibly 6.5-14 pounds (3-6.4 kg)

Mononvkus this dinosaur may have dug addicted to termite mounds for its lunch.

Mussaurus it was a prosauropod dinosaur, a plant-eating dinosaur that lived throughout the late Triassic period, about 215 million years past.

Muttaburrasaurus it is an ornithopod, a plant-eating dinosaur about 24 feet (7 m) long, dating from the middle Cretaceous era, about 113-97.5 million years before

Mutualism is an relationship between two different species of organisms in which both benefit from the association

MYA is a abbreviation of Million Years Ago