PALEONTOLOGIST, AND THIS IS AN PALEONTOLOGIST, AND THIS IS AN OCEAN.

YOU MAY NOT KNOW THAT AT PALEONTOLOGIST, AND THIS IS AN OCEAN.

YOU MAY NOT KNOW THAT AT DIFFERENT TIMES IN THE HISTORY OCEAN.

YOU MAY NOT KNOW THAT AT DIFFERENT TIMES IN THE HISTORY OF THE EARTH THE OCEANS HAVE DIFFERENT TIMES IN THE HISTORY OF THE EARTH THE OCEANS HAVE RISEN AND FALLEN.

SOMETIMES, OF THE EARTH THE OCEANS HAVE RISEN AND FALLEN.

SOMETIMES, HUGE AREAS OF LAND ARE FLOODED RISEN AND FALLEN.

SOMETIMES, HUGE AREAS OF LAND ARE FLOODED BY SEA WATER AND TURNED INTO HUGE AREAS OF LAND ARE FLOODED BY SEA WATER AND TURNED INTO SHALLOW SEAS.

AT OTHER TIMES BY SEA WATER AND TURNED INTO SHALLOW SEAS.

AT OTHER TIMES WHEN THE SEA LEVEL GOES DOWN, SHALLOW SEAS.

AT OTHER TIMES WHEN THE SEA LEVEL GOES DOWN, THE DRY LAND RETURNS.

WE KNOW WHEN THE SEA LEVEL GOES DOWN, THE DRY LAND RETURNS.

WE KNOW THAT THE MIDDLE PART OF NORTH THE DRY LAND RETURNS.

WE KNOW THAT THE MIDDLE PART OF NORTH AMERICA WAS UNDERWATER BECAUSE THAT THE MIDDLE PART OF NORTH AMERICA WAS UNDERWATER BECAUSE PALEONTOLOGISTS DIGGING IN AMERICA WAS UNDERWATER BECAUSE PALEONTOLOGISTS DIGGING IN PLACES LIKE KANSAS HAVE PALEONTOLOGISTS DIGGING IN PLACES LIKE KANSAS HAVE DISCOVERED FOSSILS OF SHARKS PLACES LIKE KANSAS HAVE DISCOVERED FOSSILS OF SHARKS LIKE CRETOXYRHINA.

DISCOVERED FOSSILS OF SHARKS LIKE CRETOXYRHINA.

>> CRETOXYRHINA.

LIKE CRETOXYRHINA.

>> CRETOXYRHINA.

>> CRETOXYRHINA--THAT'S RIGHT.

>> CRETOXYRHINA.

>> CRETOXYRHINA--THAT'S RIGHT.

AND ALSO THEY FOUND MARINE >> CRETOXYRHINA--THAT'S RIGHT.

AND ALSO THEY FOUND MARINE REPTILES LIKE... AND ALSO THEY FOUND MARINE REPTILES LIKE... >> ELASMOSAURUS.

REPTILES LIKE... >> ELASMOSAURUS.

>> YEP, ELASMOSAURUS.

BOTH WERE >> ELASMOSAURUS.

>> YEP, ELASMOSAURUS.

BOTH WERE PREDATORS THAT LIVED AND SWAM >> YEP, ELASMOSAURUS.

BOTH WERE PREDATORS THAT LIVED AND SWAM IN THE SEAS DURING THE PREDATORS THAT LIVED AND SWAM IN THE SEAS DURING THE CRETACEOUS.

SO THE NEXT TIME IN THE SEAS DURING THE CRETACEOUS.

SO THE NEXT TIME YOU'RE NEAR A DESERT, JUST CRETACEOUS.

SO THE NEXT TIME YOU'RE NEAR A DESERT, JUST THINK.

A LONG TIME AGO, IT MAY YOU'RE NEAR A DESERT, JUST THINK.

A LONG TIME AGO, IT MAY HAVE BEEN AN OCEAN.

OK. KEEP THINK.

A LONG TIME AGO, IT MAY HAVE BEEN AN OCEAN.

OK. KEEP WATCHING FOR MORE DINOSAUR HAVE BEEN AN OCEAN.

OK. KEEP WATCHING FOR MORE DINOSAUR DISCOVERIES.

WATCHING FOR MORE DINOSAUR DISCOVERIES.

>> DID YOU KNOW TH