Mosasaurs are an extinct group of large marine reptiles. Their first fossil remains were discovered in a limestone quarry at Maastricht on the Meuse in 1764. Mosasaurs probably evolved from an extinct group of aquatic lizards known as aigialosaurs in the Early Cretaceous. During the last 20 million years of...

Mosasaurs are an extinct group of large marine reptiles. Their first fossil remains were discovered in a limestone quarry at Maastricht on the Meuse in 1764. Mosasaurs probably evolved from an extinct group of aquatic lizards known as aigialosaurs in the Early Cretaceous. During the last 20 million years of...

Mosasaurs are an extinct group of large marine reptiles. Their first fossil remains were discovered in a limestone quarry at Maastricht on the Meuse in 1764. Mosasaurs probably evolved from an extinct group of aquatic lizards known as aigialosaurs in the Early Cretaceous. During the last 20 million years of...

Megalodon was an prehistoric shark that may have been 40 feet (12m) long or more. (There are a few scientists who estimate it could have been up to 50 to 100 feet long -15.5 to 31m long) This is at least two or three times as long as the Great White...

Megalodon was an prehistoric shark that may have been 40 feet (12m) long or more. (There are a few scientists who estimate it could have been up to 50 to 100 feet long -15.5 to 31m long) This is at least two or three times as long as the Great White...

Megalodon was an prehistoric shark that may have been 40 feet (12m) long or more. (There are a few scientists who estimate it could have been up to 50 to 100 feet long -15.5 to 31m long) This is at least two or three times as long as the Great White...

Megalodon was an prehistoric shark that may have been 40 feet (12m) long or more. (There are a few scientists who estimate it could have been up to 50 to 100 feet long -15.5 to 31m long) This is at least two or three times as long as the Great White...

Megalodon was an prehistoric shark that may have been 40 feet (12m) long or more. (There are a few scientists who estimate it could have been up to 50 to 100 feet long -15.5 to 31m long) This is at least two or three times as long as the Great White...

Megalodon was an prehistoric shark that may have been 40 feet (12m) long or more. (There are a few scientists who estimate it could have been up to 50 to 100 feet long -15.5 to 31m long) This is at least two or three times as long as the Great White...

Megalodon was an prehistoric shark that may have been 40 feet (12m) long or more. (There are a few scientists who estimate it could have been up to 50 to 100 feet long -15.5 to 31m long) This is at least two or three times as long as the Great White...

Megalodon was an prehistoric shark that may have been 40 feet (12m) long or more. (There are a few scientists who estimate it could have been up to 50 to 100 feet long -15.5 to 31m long) This is at least two or three times as long as the Great White...

Megalodon was an prehistoric shark that may have been 40 feet (12m) long or more. (There are a few scientists who estimate it could have been up to 50 to 100 feet long -15.5 to 31m long) This is at least two or three times as long as the Great White...

Megalodon was an prehistoric shark that may have been 40 feet (12m) long or more. (There are a few scientists who estimate it could have been up to 50 to 100 feet long -15.5 to 31m long) This is at least two or three times as long as the Great White...

Mosasaurs are an extinct group of large marine reptiles. Their first fossil remains were discovered in a limestone quarry at Maastricht on the Meuse in 1764. Mosasaurs probably evolved from an extinct group of aquatic lizards known as aigialosaurs in the Early Cretaceous. During the last 20 million years of...

Mosasaurs are an extinct group of large marine reptiles. Their first fossil remains were discovered in a limestone quarry at Maastricht on the Meuse in 1764. Mosasaurs probably evolved from an extinct group of aquatic lizards known as aigialosaurs in the Early Cretaceous. During the last 20 million years of...

Mosasaurs are an extinct group of large marine reptiles. Their first fossil remains were discovered in a limestone quarry at Maastricht on the Meuse in 1764. Mosasaurs probably evolved from an extinct group of aquatic lizards known as aigialosaurs in the Early Cretaceous. During the last 20 million years of...

Megalodon was an prehistoric shark that may have been 40 feet (12m) long or more. (There are a few scientists who estimate it could have been up to 50 to 100 feet long -15.5 to 31m long) This is at least two or three times as long as the Great White...

Megalodon was an prehistoric shark that may have been 40 feet (12m) long or more. (There are a few scientists who estimate it could have been up to 50 to 100 feet long -15.5 to 31m long) This is at least two or three times as long as the Great White...

Megalodon was an prehistoric shark that may have been 40 feet (12m) long or more. (There are a few scientists who estimate it could have been up to 50 to 100 feet long -15.5 to 31m long) This is at least two or three times as long as the Great White...

Megalodon was an prehistoric shark that may have been 40 feet (12m) long or more. (There are a few scientists who estimate it could have been up to 50 to 100 feet long -15.5 to 31m long) This is at least two or three times as long as the Great White...

Megalodon was an prehistoric shark that may have been 40 feet (12m) long or more. (There are a few scientists who estimate it could have been up to 50 to 100 feet long -15.5 to 31m long) This is at least two or three times as long as the Great White...

Mastodon Tooth and Roots, Pleistocene Epoch 2.6 million years old. Tulsa, Oklahoma Mastodons were large elephant-like mammals that lived 33 million years ago until 10,000 years ago. Mastodon fossils have been found on every continent except Antarctica and Australia. Although not closely related, mastodons were similar in appearance to mammoth species,...

Mastodon Tooth and Roots, Pleistocene Epoch 2.6 million years old. Tulsa, Oklahoma Mastodons were large elephant-like mammals that lived 33 million years ago until 10,000 years ago. Mastodon fossils have been found on every continent except Antarctica and Australia. Although not closely related, mastodons were similar in appearance to mammoth species,...

Mastodon Tooth and Roots, Pleistocene Epoch 2.6 million years old. Tulsa, Oklahoma Mastodons were large elephant-like mammals that lived 33 million years ago until 10,000 years ago. Mastodon fossils have been found on every continent except Antarctica and Australia. Although not closely related, mastodons were similar in appearance to mammoth species,...

Museum quality, 30 million years old, Oligocene age Oreodont Skeleton from Blue Formation Pennington County, South Dakota, USA  Oreodonts are fossil mammals and are one of the most common fossils found in the Badlands. Oreodonts lived from the Middle Eocene through the end of the Miocene (from about 40 million...

Museum quality, Oligocene age Oreodont Skeleton from Blue Formation Pennington County, South Dakota, USA  Oreodonts are fossil mammals and are one of the most common fossils found in the Badlands. Oreodonts lived from the Middle Eocene through the end of the Miocene (from about 40 million to 5 million years...

Mastodon Tooth and Roots, Pleistocene Epoch 2.6 million years old. Tulsa, Oklahoma   Mastodons were large elephant-like mammals that lived 33 million years ago until 10,000 years ago. Mastodon fossils have been found on every continent except Antarctica and Australia. Although not closely related, mastodons were similar in appearance to mammoth...