Among the most famous fossils in the world, The "fish within a fish" was discovered and excavated by George F. Sternberg just Southwest of Hays. The most complete specimen off its kind, the fossil comprises of two sepereate fish species, a 14-foot Xiphactinus audax and a 6-foot Gillicus. The larger Xiphactinus audax died shortly after consuming the much smaller Gilicus and are preserved together in a single fossil
Xiphactinus auddax was one of the largest bony fish of the Late Cretaceous and is considered one of the fiercest creatures in the sea. A powerful tail and winglike pectoral fins shot the 14-foot-long monster through the surface waters of the ocean. Unlucky fish and unsuspecting seabirds were snared inside it's upturned jaw, which was lined with giant, fanglike teeth, giving it an expression of a bulldog. A 14-foot-long Xiphactinus could open its jaw wide enough to swallow a six-foot-long fish whole, but it itself was occasionally prey to the shark Cretoxyrhina. Xiphactinus trolled an ancient ocean called the Western Interior Seaway, which covered much of central North America during the Cretaceous. Though long extinct, if alive today the bony fish would look like a giant, fanged tarpon.
Gillicus was a relatively small, 6-foot ichthyodectid fish that lived in the Western Interior Seaway. Gillicus had numerous small teeth lining its jaws, and ate smaller fish by sucking them into its mouth. Gillicus would also filter feed and was also prey to its much large relative, the Xiphactinus auddax.
What is a Fossil?
Fossils are the preserved remains or traces of animals, plants, and other organisms from the remote past. There are two major types of fossils - body fossils and trace fossils. Both are the remains of living organisms. Body fossils reveal the body structure of the organism and are the most common type of fossil found across the world. They are formed from the remains of dead animals and plants. Most body fossils are of hard parts such as teeth, bones, shells, or woody trunks, branches, and stems. Trace fossils show indirect evidence of life in the past and consist of a footprint, trail, burrow, or other trace of an animal rather than of the animal itself.
Formation of Fossils
Fossils are formed in a number of different ways, but most are formed when a plant or animal dies in a watery environment and is buried in mud and silt. Soft tissues quickly decompose leaving the hard bones or shells behind. Over time sediment builds over the top and hardens into rock. As the encased bones decay, minerals seep in replacing the organic material cell by cell in a process called "petrification". Alternatively the bones may completely decay leaving a cast of the organism. The void left behind may then fill with minerals making a stone replica of the organism.
Some fossils can form in unusual ways. Small bugs or insects can become trapped in tree sap. Eventually the sap hardens and forms the semiprecious material called amber. In some pieces of amber the entombed remains of organisms can be found. Volcanic eruptions can form fossils when animals get trapped in the hot ash flows. In this case, the fossil is a hole in the shape of the animal.
By far the most common fossil remains are those of shelled invertebrate sea loving creatures such as snails, corrals, and clams and make up most of the fossil record. Fossils of land animals are scarcer than those of sea creatures. In order to become fossilized, animals must die in a watery environment and become buried in the mud and silt. Because of this requirement most land creatures never get the chance to become fossilized unless they die next to a lake or stream. Indeed there may be whole species of land animals in which no fossil record has been discovered. We may never know how many and diverse these animals were.
Logging Requirements
Please Email your answers to ottie18@hotmail.com
1.) Based on the information above, is the fossil a body fossil or a trace fossil?
2.) Since the two fish were fossilized together and the gillicus was never digested, this likely means that the Xiphactinus auddax died shortly after consuming the gillicus. what do you think caused the death of the Xiphactinus auddax?
3.) Take a photo of either yourself or a member(s) of your geocaching party next to the display and post it with your log. (optional, but will help if there's something fishy about your log)