CAMBRIAN PERIOD to PRESENT: 525 million years ago to present day
Ancient legends abound with "sea monsters" but the most far-fetched imagination can't compare to the terrifying truth of what really lived in the prehistoric seas as evidenced by numerous marine vertebrate fossils discovered over the past years. Huge 50 foot sharks that had teeth the size of dinner plates and jaws in excess of 7 feet. Snake-like Mosasaurs over 40 feet in length that possessed ferocious appetites and 6 foot tooth-filled jaws. There were schools of fish larger than a man that had sabre-toothed fangs longer than your index finger able to pierce and devour anything that would get in their way. If I lived in those days, I wouldn't even put a boat on the ocean! When you start to envision the sizes of so many of these creatures it becomes almost impossible to believe how terrifying the prehistoric oceans must have been and just how dangerous it would have been to swim in them. EVERYTHING seemed to have quite an abundance of LARGE teeth!
Could any of these beasts have survived up to the last few hundred years? With so many cultures scattered across the globe sharing their own versions of tales of "sea monsters", one has to wonder what was the source of these legends' origins? According to scientific terminology, these large dinosaur-like creatures that lived in the prehistoric seas are not considered dinosaurs but are classified as "marine reptiles" and therefore, are listed here in this section apart from the DINOSAUR section.
The first marine vertebrates are known from the fossil record dating back to the Cambrian Period and the Cambrian Explosion. Here we have jawless fish that were filter feeders, swimming amongst a plethora of more numerous invertebrates. By the Ordovician Period, fishes with jaws arrived on the scene and by the Devonian Period, nearly all jawless fishes gave way to the rise of jawed fish. It is during the Carboniferous Period that the first true amphibians appear in the fossil record. By the Permian Period, amphibians rise in numbers with some achieving great proportions to share the throne as apex predators along with other aquatic vertebrates. Probably the most successful marine vertebrates are sharks. Fossil shark scales dating back to the Silurian Period, 420 million years ago, demonstrate just how old they are. Their fossils reveal that sharks have remained relatively unchanged for hundreds of millions of years, right up to the present day.
In this section we include not only large marine reptiles but a variety of other marine vertebrates. Sharks of all types along with skates and rays, fish, tortoises, turtles and anything else that possessed a spine and lived in an aquatic environment can be found below. While we have labeled this category "marine" vertebrates, we also have included many prehistoric creatures that had once lived in freshwater such as amphibians and freshwater bony fish.
- text copyright Paleo Direct, Inc., art by Frank Denota / Todd Marshall