Elasmosaurus

Introduction and Classification

Discovery and Naming

The Holotype and Additional Finds

The holotype specimen of Elasmosaurus, cataloged as ANSP 10081, is incomplete but still substantial; it includes skull fragments, jaw parts, 72 neck (cervical) vertebrae, a few pectoral, back, sacral, and tail vertebrae, and rib fragments. Some elements, such as the pectoral and pelvic girdles, were described and illustrated by Cope in the 1800s but were later lost, likely destroyed in a vandalized New York workshop where they had been loaned for preparation.

Over the years, additional plesiosaur fossils were found near the original discovery site, but it is debated whether these belong to the original Elasmosaurus specimen or even to the same species. The holotype's neck vertebrae have been distorted by fossilization processes, and some bones have gone missing or may have been lost or damaged during collection and transport. In 1986, a three-dimensional reconstruction of the holotype was completed and is now displayed at the ANSP, with replicas in other museums, including Fort Wallace.

Some researchers have proposed that a fragmentary elasmosaurid skeleton found in Germany could possibly belong to Elasmosaurus, but this is not confirmed.

Body Structure and Size

Although we are still missing several parts of Elasmosaurus, scientists can make educated guesses based on looking at what we do have as well as fossils from other closely related species. Based on this, Elasmosaurus would have had a long, streamlined body - well adapted for marine life - and four paddles to move through the water. It had a very long neck and proportionally short head, and a long, slender, triangular-shaped skull with a rounded snout; both characteristic features of elasmosaurs (the group that includes Elasmosaurus and its close relatives).

Current estimates place Elasmosaurus at around 10 m long, with around 70% of that length (7 m) being just its neck - making it one of the longest-necked animals known! We know that it had at least 72 neck vertebrae.

There is no direct universally agreed-upon weight estimate for Elasmosaurus. The original specimen is incomplete and missing limb bones and much of the body, making mass estimates uncertain, and its unusual body proportions (especially the long neck) make estimating weight more complicated.

Teeth and Feeding

Elasmosaurus' jaws were lined with large, fang-like teeth at the front, which became smaller toward the back of the mouth. The upper jaw likely had around six teeth at the very front, with more teeth along the sides (up to 14 in each upper jaw bone). The lower jaw probably had between 17 and 19 teeth on each side. Overall, Elasmosaurus had a mouth full of sharp teeth that fit together like interlocking fingers. The front teeth were designed to grab slippery prey, like fish, while the back teeth were smaller. The exact number of teeth is uncertain because the fossil skull is incomplete, but it's clear Elasmosaurus had a lot of teeth! The bones of the lower jaw were tightly joined together at the front, giving the jaw extra strength.

Swimming and Reproduction

The streamlined body of Elasmosaurus and the four long paddles show it was well-adapted for swimming through the Mesozoic oceans, though it is not clear exactly what kind of speed Elasmosaurus could reach; its long neck would have created extra drag in the water except when completely straight. Plesiosaurs, including Elasmosaurus, likely swam mainly using their powerful front flippers, while the back flippers helped them steer and stay stable in the water. Their stiff, paddle-shaped limbs meant they couldn't come onto land, so they likely gave birth to live young in the water, as shown by fossils of other plesiosaurs with unborn babies inside.

Fossil evidence shows that elasmosaurs could be hunted by large predators of their time, such as sharks and bigger marine reptiles.

The Function of the Long Neck

Research suggests Elasmosaurus couldn't raise its neck out of the water like a swan because its extremely long, heavy neck was too weakly muscled to lift high, and its vertebrae only allowed gentle curves, not sharp upward bends. Most of its weight was centered behind the front flippers, making it hard to balance or lift the neck when floating. As a result, it could only lift its head above the surface in shallow water, where its body could rest on the bottom.

The exact role of the long neck in elasmosaurids is still uncertain - it wasn't a snorkel, since breathing through such a long neck underwater would create pressure issues, require much larger lungs, and make swimming energetically costly. Some have suggested the long neck was likely used for stealth hunting - Elasmosaurus could float calmly with its body concealed below while slowly extending its head toward prey, allowing a surprise strike. It could also have used its long neck to pluck prey from the sea floor without moving its whole body.

Diet and Hunting Strategies

Fossils found beneath the original Elasmosaurus skeleton included the scales and teeth of several fish species, suggesting that fish were a major part of its diet. The neck's range of motion would have let Elasmosaurus hunt in different ways, such as benthic grazing (scooping prey from the sea floor), chasing prey in open water, or possibly even stunning prey with sideways movements of its head and teeth.

Evidence suggests Elasmosaurus could prey on animals ranging from about 30 cm to 2 m long, including fish and cephalopods. Elasmosaurus likely swallowed its prey whole because its long, slender teeth were shaped for gripping slippery fish, not for cutting or chewing. Its jaws and teeth could seize and hold onto prey, but they weren't strong enough for biting chunks off or tearing flesh - so once caught, the animal would simply gulp the prey down whole.

It may have hunted by sneaking up from below schools of fish, using upward-facing eyes to spot prey silhouetted against the sunlight. While other elasmosaurs are often found with many gastroliths (stomach stones), Elasmosaurus itself has only one confirmed stone; these stones may have helped with digestion or buoyancy.

Habitat and Ecosystem