Phylum | Class | Order | Family | Chordata | Reptilia | Ornithischia | Ceratopsidae | Age | Geologic time | 80.1 - 77 Ma | | Cretaceous | |
Machairoceratops cronusiIt is named after the Greek word machairis meaning "bent sword" and the sickle or scythe-wielding Greek titan Cronus. In life, it likely reached 6-8 m (20-26 ft) in length and weighed 1-2 tons, half the weight of Triceratops. | Phylum | Class | Order | Family | Chordata | Sauropsida | ? | Teleosauridae | Age | Geologic time | 154 - 130 Ma | | Jurassic | Cretaceous | |
Machimosaurus rexAround 120 million years ago, there lived a monstrous marine crocodile relative named Machimosaurus rex. Its massive jaws could crush turtle shells and it terrorized the warm seas that covered what are now the deserts of Tunisia. |
Phylum | Class | Order | Family | Chordata | Mammalia | Litopterna | Macraucheniidae | Age | Geologic time | 7 Ma - 10,000 | | Neogene | Quaternary | |
Macrauchenia patachonicaMacrauchenia (name meaning "long llama") was a long-necked and long-limbed, three-toed South American ungulate mammal, typifying the order Litopterna. In life, Macrauchenia resembled a humpless camel with a short trunk, though it is not closely related to either camels or proboscideans. | Phylum | Class | Order | Family | Chordata | Reptilia | Ornithischia | Hadrosauridae | Age | Geologic time | 80 - 75 Ma | | Cretaceous | |
Maiasaura peeblesorum |
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Phylum | Class | Order | Family | Chordata | Mammalia | Proboscidea | Mammutidae | Age | Geologic time | 4 Ma - 10,000 | | Neogene | Quaternary | | Mammut americanum | Phylum | Class | Order | Family | Chordata | Mammalia | Proboscidea | Elephantidae | Age | Geologic time | 1.5 Ma - 11,000 | | Quaternary | | Mammuthus columbi |
Phylum | Class | Order | Family | Chordata | Mammalia | Proboscidea | Elephantidae | Age | Geologic time | 250,000 - 10,000 | | Quaternary | |
Mammuthus primigenius | Phylum | Class | Order | Family | Chordata | Placodermi | Ptyctodontida | Ptyctodontidae | Age | Geologic time | 380 Ma | | Devonian | |
Materpiscis attenboroughiArmored fish called placoderms like Materpiscis lived in the waters of the Devonian Period. They were among the first creatures to have had jaws, structures modified from their gill arches. |
Phylum | Class | Order | Family | Chordata | Reptilia | Squamata | Varanidae | Age | Geologic time | 1.8 Ma - 50,000 | | Quaternary | | Megalania prisca | Phylum | Class | Order | Family | Chordata | Mammalia | Artiodactyla | Cervidae | Age | Geologic time | 400,000 - 10,000 | | Quaternary | | Megaloceros giganteus |
Phylum | Class | Order | Family | Chordata | Mammalia | Artiodactyla | Cervidae | Age | Geologic time | 3 Ma - 8,000 | | Neogene | Quaternary | |
MegalocerosCommonly known as Irish Elk, Megaloceros is actually more closely related to the fallow deer. The largest members of this genus could grow nearly 2 m (6.5 ft) at its shoulders. | Phylum | Class | Order | Family | Chordata | Mammalia | Pilosa | Megalonychidae | Age | Geologic time | 10.3 Ma - 11,000 | | Neogene | Quaternary | |
Megalonyx jeffersoniiThis medium-sized ground sloth could grow to more than twice the size of a polar bear. It appeared in North America 10 million years ago and only went extinct 11,000 before present. Its species name is a tribute to President Thomas Jefferson, who coined the name Megalonyx which means "Large Claw" in 1797. |
Phylum | Class | Order | Family | Chordata | Reptilia | Saurischia | Megalosauridae | Age | Geologic time | 170 - 155 Ma | | Jurassic | | Megalosaurus bucklandi | Phylum | Class | Order | Family | Arthropoda | Insecta | Meganisoptera | Meganeuridae | Age | Geologic time | 280 Ma | | Permian | |
Meganeuropsis permianaThe largest known insect of all time belongs to a group of Paleozoic flyers called Griffinflies. With a wingspan reaching more than two feet across, these predators controlled the skies of the late Paleozoic. |
Phylum | Class | Order | Family | Arthropoda | Insecta | Meganisoptera | Meganeuridae | Age | Geologic time | 280 Ma | | Permian | |
MeganeuropsisThe largest known insect of all time belongs to a group of Paleozoic flyers called Griffinflies. With a wingspan reaching more than two feet across, these predators controlled the skies of the late Paleozoic. | Phylum | Class | Order | Family | Arthropoda | Insecta | Meganisoptera | | Age | Geologic time | 300 - 240 Ma | | Carboniferous | Permian | Triassic | | Meganisoptera |
Phylum | Class | Order | Family | Arthropoda | Merostomata | Eurypterida | Mycteroptidae | Age | Geologic time | 300 Ma | | Carboniferous | | Megarachne servinei | Phylum | Class | Order | Family | Chordata | Mammalia | Pilosa | Megatheriidae | Age | Geologic time | 30 Ma - 10,000 | | Paleogene | Neogene | Quaternary | | Megatherium americanum |
Phylum | Class | Order | Family | Chordata | Mammalia | Artiodactyla | Camelidae | Age | Geologic time | 13.6 - 1.8 Ma | | Neogene | Quaternary | |
MegatylopusGrowing as tall as 4.20 m (14 ft) tall, the giant camel Megatylopus is only slightly shorter than today’s fully-grown giraffes. It lived in North America 13.6 to 1.8 million years ago and its fossils have been found from North Carolina to California. | Phylum | Class | Order | Family | Chordata | Reptilia | Saurischia | Metriacanthosauridae | Age | Geologic time | 160 Ma | | Jurassic | |
Metriacanthosaurus parkeriThis Jurassic predator lived 160 million years ago in what is now England. It is a close relative of the better known Allosaurus, which was mostly found in North America. |
Phylum | Class | Order | Family | Chordata | Reptilia | Saurischia | Alvarezsauridae | Age | Geologic time | 80 - 72 Ma | | Cretaceous | | Mononykus olecranus | Phylum | Class | Order | Family | Chordata | Reptilia | Squamata | Mosasauridae | Age | Geologic time | 100 - 65 Ma | | Cretaceous | | Mosasauridae |
Phylum | Class | Order | Family | Chordata | Reptilia | Squamata | Mosasauridae | Age | Geologic time | 92 - 66 Ma | | Cretaceous | |
MosasaurusParapuzosia was a large Cretaceous ammonite which could grow up to 3 m (9.8 ft) in diameter. It lived in a sea full of predators like the monitor lizard-like Mosasaurus. | Phylum | Class | Order | Family | Chordata | Reptilia | Saurischia | Neovenatoridae | Age | Geologic time | 93 - 89 Ma | | Cretaceous | |
Murusraptor barrosaensisMurusraptor, or "wall robber" is named after the Argentinian ravine wall it was discovered in. For a 7.5 meter (25 ft) long animal, its teeth are unusually small at less than 3 cm (1 in) tall. |
Phylum | Class | Order | Family | Chordata | Reptilia | Saurischia | Mussauridae | Age | Geologic time | 220 Ma | | Triassic | | Mussaurus patagonicus | Phylum | Class | Order | Family | Chordata | Reptilia | Ornithischia | Rhabdodontidae | Age | Geologic time | 112 - 99.6 Ma | | Cretaceous | |
MuttaburrasaurusThe Wollemi Pine is a critically endangered Australian plant which has been around since the beginning of the Jurassic. Back in the day, it would have lived with large herbivorous dinosaurs such as Muttaburrasaurus. |
Phylum | Class | Order | Family | Chordata | Reptilia | Phytosauria | Phytosauridae | Age | Geologic time | | | Triassic | |
MystriosuchusMystriosuchus was a phytosaur, a lineage of aquatic reptiles very similar but not closely related to true crocodilians. This species lived in the Late Triassic of Europe and show signs of being much more dedicated to an aquatic lifestyle than most of its relatives. Somewhat speculative details are a caudal fin like the later metriorynchid crocodiles and a soft tissue crest like some pterosaurs. |   |