Xiphactinus
by Owen N.
The Xiphactinus is a 20-foot long fish that swam in the early North American Sea millions of years ago. He was a ferocious predator that had an enormous head and a very long tail. The Xiphactinus was one of the first fish with fin-rays, which are fins that help it swim faster. It belongs to the group of Teleoths. Teleoths are a group of fish that is different from other types.
The first adaptation that the Xiphactinus evolved was a vertebral column & brain case. This made it a vertebrate. After this it evolved a jaw. This jaw made it a gnathostome.
In our cladogram, the Xiphactinus is most closely related to the lungfish, the salamander, the turtle, the cryptocleidus, the crocodile, the rhamphorhynchus, the apatosaurus, the dilophosaurus, the tyrannosaurus, the struthiomimus, the deinonychus, the archaeopteryx, the seagull, the stegosaurus, the shamosaurus, the sauropelta, the saurolophus, the corythosaurus, the stegoceras, the psittacosaurus, the protoceratops, the triceratops, the dimetrodon, the thylacosmilus, the anteater, the rabbit, the bat, the lemur, the whale, the horse, the mammoth, the hylochoerus meinertzhageni, and the Irish elk. The most advanced trait that they share is jaws. The most important difference is that the Xiphactinus doesn’t have lungs, but all of the other things do. I used the cladogram to answer these questions by looking to what node they most recently met up at, and checking what the trait of that node was. I determined the closest relatives to the Xiphactinus by looking at the most recent node it branched off of and looked at the other animals that branched off of the node. These animals were the Xiphactinus’ closest relatives. At the AMNH, the cladogram there said that the Xiphactinus was more closely related to Gars than anything else. Some traits they share are jaws, a vertebral column and brain case, gills, and fins.
Last updated April 11, 2007.