The Late Cretaceous Sea

from the Dinosaur Collector

Kronosaurus  is extinct from  about the Middle Turonian stage of the Late Cretaceous.  The pliosaurs that remain are the smaller Dolichorhynchops   A branch of the monitor lizard family went to sea; their descendants are snakes. Mosasaurs were extremely successful, and may have contributed to the disappearance of the ichthyosaurs and the decline of the plesiosaurs.  In the Late Cretaceous, the Western Interior Seaway reached as far north as the Arctic Sea and as far south as the Gulf of Mexico; completely dividing the eastern and western landmasses of what we now call North America. Generally shallow, the waterway is estimated to have been less than 600 feet deep, with a flat, muddy bottom.  Turtles, fish, mosasaurs, pleisosaurs, and aquatic birds swam the shallow seas and invertebrates, such as crinoids, echinoids, crabs, lobsters, ammonites, snails and clams were common.

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Dolichorhynchops a short-necked plesiosaur that used long, paddle-like flippers to fly through the water like a penguin. 12 to 15 feet  long a Smithsonian fossil  Tylosaurus contains the remains of a juvenile .Dolichorhynchops fossils have been found with unborn babies inside, strong evidence they gave birth to live young.

K&M Wild Republic Sea Monsters Collectables done in conjunction with National Geographic.

 Elasmosaurid plesiosaurs were an important part of Cretaceous marine reptile communities and are generally considered to have been predators of small, agile, free-swimming fish and cephalopods. Professor Bob Bakker has speculated based on skull comparisons that the elasmosaurid plesiosaurs of the Cretaceous are not directly descended from the Jurassic plesiosaurs.  Instead he has proposed that they re-evolved from the short-necked pliosaurs.

Elasmosaurus, (Thin plated Lizard) size: 46 feet long. It is thought that Elasmosaurus used its flippers to fly through the water like a penguin.  Since no evidence of live birth has been found they are assumed to have returned to land to lay their eggs.  Mosasaurus (Meuse-River lizard) size 59 feet long. A full-grown Mosasaurus had a 6-foot long skull with 4-foot jaws, capable of opening 3 feet apart.  Like modern constrictors and other types of mosasaurs, the lower jaws were two separate units and could spread apart at the anterior end, stretching to give this amazing creature the ability to swallow huge prey.		Hydrotherosaurus (meaning "water beast lizard") is an elasmosaurid plesiosaur from the Late Cretaceous. Hydrotherosaurus is primarily from a complete fossil found in California. Along with the creature's last meal were gastroliths ("stomach stones"), which could have helped anchor Hydrotherosaurus to the sea bottom, where the food was.
Original Elasmosaurus with downward pointing head, and retired Mosasaurus from Carnegie Safari series.		Hydrotherosaurus is from Procon CollectA . Dino Horizon Panorama series from Cog Ltd Ammonite.

Elasmosaurus had the longest neck of all the swan necked plesiosaurs, with over 1/2 of its length made up of neck.  It ate fish, mollusks, and soft-bodied invertebrates.  While often pictured with head rearing from the water this does not seem likely given the length of the neck.  It seems to have been more flexible side to side than up and down.		The long neck must have offered an advantage ambushing small faster prey, while limiting its speed and perhaps making it vulnerable to the newly evolving sharks and mosasaurs.  The large size and extreme adaptations of the last plesiosaurs may be a sign they were under some kind of evolutionary stress. One idea is that plesiosaurs declined as modern types of sharks appear.
Original Carnegie Safari Elasmosaurus is in the front, and the recent version looking forward in the back. Safari often seems to make unpublished changes to figures.  This change could be a result of differences in the manufacturing process.		Carnegie Safari series repaint.

Futabasaurus suzukii,a partial skeleton found in Japan expands the know range of elasmosaurid plesiosaurs.

Futabasaurus form Colorata in Japan.

Tylosaurus (Swollen Lizard) was, at over 45 feet, one of the largest of the three types of mosasaurs.  It lived in the vast Western Interior Seaway alongside several other species of mosasaurs, including the familiar Platecarpus and Plioplatecarpus, while other relatives of Tylosaurus, such as Mosasaurus, lived in Europe.

Ammonites, with their curled shells, and Belemnites were characteristic of the Late Cretaceous Seas, and their disappearance marks the end of the Mesozoic.    Several sea going turtles existed in the Cretaceous. The giant sea turtle Archelon had a life style much like the present-day green back turtle. Archelon ischyros lived about 70 million years ago in the Mid-American Seaway, during the Cretaceous period. At least occasionally they were food for the giant Mosasasurus; fossils of Archelon with teeth marks that match the bite of mosasaurs have been found.  The shell of this turtle was reduced to a framework of struts made from bony ribs that grew from the backbone. It had weak jaws, a toothless beak, and probably fed on jellyfish.

Ammonites and a Belemnite from Bullyland, and a Plesiosaurus from the Laramie play set, strongly reminiscent of the Invicta figure.

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