Top Ten: Extinct Sea Monsters (Part 3 of 5)

 5.  Elasmosaurus - Next up on our trip across time is Elasmosaurus.  One of the largest of the Plesiosaurs ever discovered, Elasmosaurus grew up to 46 feet long, which was about half neck.  Equipped with a fairly small head, Elasmosaurus would have been incapable of going after large prey, so it would have mostly stuck with fish.  Elasmosaurus lived during the Late Cretaceous, a time when much of North America was "Beneath the Waves," under something that we call the "Western Interior Seaway."   Remains of this animal were first uncovered in Kansas, but it almost certainly swam all over the seaway, including in Colorado.

6.  Dunkleosteus - Dunkleosteus, a creature we talked about a few weeks ago in our post about the Coelacanth, is another fascinating animal.  Almost thirty-five feet in length, Dunkleosteus was a member of the Placoderms, a group of armored fish that were only around for about 50 MYA.  A long time, to be sure, but not very long compared to the 400 million year reign of the sharks.  While the Placoderms themselves lived during the Silurian and Devonian Periods, they went extinct during the transition to the Carboniferous Period, at the end of the Devonian.  Dunkleosteus fossils have been discovered in North America, Poland, Belgium, and Morocco.

 COMING UP:

7.  Archelon
8.  Leedsichthys
9.  Tanystropheus
10. Tylosaurus

This post is part of the "Top Ten: Extinct Sea Monsters" series.  For the rest of the posts in this series, click HERE.  

Another Living Fossil: The Coelacanth

400 millions years ago (MYA), during the Devonian Period, life had already gained a foothold on land.  However, in the seas, unless you were at the top of the food chain, there were a lot of predators to contend with.  If you were a fish in the middle of the food chain during the Devonian, you not only had to deal with ancestors of the modern day shark, but a now-extinct group of armor-plated fish, called the Placoderms.  Some of these Placoderms, like Dunkleosteus, grew to simply enormous proportions, around 30 feet in length!  One type of fish that lived during the Devonian and was most likely preyed upon by the sharks and the Placoderms was a fish known as the Coelacanth.

The Coelacanth (SEE-lah-canth) was a relatively unassuming fish, its closest living relative being the lobe-finned fish.  Fossils of the Coelacanth have been discovered ranging from 400 MYA to around 65 MYA, coinciding with the death of the dinosaurs.  In 1938, however, when one was hauled in on a fishing net off the coast of South Africa, the temporal range of this animal was extended by 65 million years!  Today, by studying the living Coelacanth, scientists have found that the fish gives birth to live young, unlike other fish.  Further discoveries both in Africa (off the coasts of Mozambique, Madagascar, Kenya and Tanzania) as well as Asia, around Sulawesi, Indonesia, of living Coelacanth specimens have further widened the current geographical range of the Coelacanth.

A specimen of the Cretaceous coelacanth Coccoderma nudum from Germany.  On display at the Mace Brown Museum of Natural History on the campus of the College of Charleston in South Carolina.

Unfortunately for this living fossil, it is labeled "Critically Endangered" by the IUCN, much like yesterday's living fossil, the mountain pygmy possum.  Just like the mountain pygmy possum, conservationist groups are working towards it's protection, trying to keep fisherman from fishing in the Coelacanth's habitat.  Hopefully, humans won't be the final nail in the coffin, so to speak, for this 400 million year old fish.