Shamosaurus
by Emily O.
Ever heard of a six meter-long dinosaur with armored plates on its back and a club tail? That would be a shamosaurus. A shamosaurus is an extinct dinosaur that had evolved eight distinct and important traits according to our cladogram.
First, the shamosaurus became a vertebrate, which means it evolved a backbone and a skull. This is key to the shamosaurus line of evolution, because without a backbone, it would not have its armor. Next, the shamosaurus evolved a jaw, a necessity for eating, making it a gnathostome. It then evolved to become a tetrapod, which is an animal with four limbs. A shamosaurus then evolved a watertight egg and became an amniote. A watertight egg meant that they could now lay eggs on land instead of in the water. Fourth, the shamosaurus evolved a pair of holes in the palate, which means it was called a sauropsid. Then, it became a dinosaur. The trait that all dinosaurs have is a hole in the hip socket. This hole made it possible to walk upright, instead of having their limbs bending out to the side, like crocodiles do. The shamosaurus now evolved a backward-pointed protrusion of its pubis bone, making it an ornithischian. Then, along with two other ornithischian dinosaurs, the shamosaurus evolved bony body armor, making it a thyreophoran. This was a major defense for the shamosaurus, as it was prey to carnivores. These eight traits are the most important in the evolution of the shamosaurus.
Though the shamosaurus was distinctly different from other dinosaurs, it still was related to other animals as well. Its closest relative, according to this cladogram, is the sauropelta. They are extremely similar, as they share the heavy body armor. In fact, the only major difference between them is that the shamosaurus evolved a tail with a rounded bone at the end; a club tail! This is the closest node to both the sauropelta and the shamosaurus. Even at the American Museum of Natural History, the sauropelta is still the closest to shamosaurus, even though they have many more animals on their cladogram. It is easy to see this on the cladogram if specific attention is paid to the nodes. In order to read a cladogram, the reader must go backwards down the evolutionary tree, starting with their animal. Tracing your animal’s line of descent, you can see what other animal or animals are connected to its most advanced node. By following the nodes your animal is connected to, it is easy to see what animals it is closely related to, what traits they share, and what differences they have. In conclusion, the shamosaurus is an amazing dinosaur that has undergone many evolutionary changes.
Last updated April 7, 2007.