Phylum: Chordata
Simply put, chordate animals have a spinal cord. The sub-phylum Vertebrata is comprised of those animals who have skulls and backbones, or vertebrae. The backbones consist of either bone or cartilage.
There are eight classes of vertebrate fossils.
Class Agnatha
These are the jawless fish and are the most primitive of the vertebrate animals. They were first known in the Lower Ordovician, and there are two groups still alive today: lampreys and hagfish.
Class Placodermi
This group of fishes includes the first jawed vertebrates. They appeared during the Upper Silurian and became extinct during the Lower Permian.
Class Aves
Birds emerged from theropod dinosaurs during the Jurassic Period, about 160 million years ago. Hesperornis is known from the Upper Cretaceous chalk beds of western Kansas.
Class Amphibia
Amphibians lay eggs and generally begin their lives as larvae in the water. They undergo a metamorphosis from animals with gills to air-breathing animals that their adult lives on land. Frogs and salamanders are common living amphibians.
Class Chondrichthyes
These are cartiliginous marine animals and include sharks and rays. They appeared during the Devonian Period, and there are many genera alive today. Cartilage is rarely fossilized, so paleontologists have to rely on the teeth and occasional fossilized vertebrae for clues about how ancient sharks lived and what they looked like.
Sharks shed teeth as they grow. Many, if not most, of the sharks' teeth we collect in Kansas are these shed teeth. On occasion, a collector is fortunate enough to find a jaw plate intact.
They were, and are, very successful predators.
There are eight classes of vertebrate fossils.
Class Agnatha
These are the jawless fish and are the most primitive of the vertebrate animals. They were first known in the Lower Ordovician, and there are two groups still alive today: lampreys and hagfish.
Class Placodermi
This group of fishes includes the first jawed vertebrates. They appeared during the Upper Silurian and became extinct during the Lower Permian.
Class Aves
Birds emerged from theropod dinosaurs during the Jurassic Period, about 160 million years ago. Hesperornis is known from the Upper Cretaceous chalk beds of western Kansas.
Class Amphibia
Amphibians lay eggs and generally begin their lives as larvae in the water. They undergo a metamorphosis from animals with gills to air-breathing animals that their adult lives on land. Frogs and salamanders are common living amphibians.
Class Chondrichthyes
These are cartiliginous marine animals and include sharks and rays. They appeared during the Devonian Period, and there are many genera alive today. Cartilage is rarely fossilized, so paleontologists have to rely on the teeth and occasional fossilized vertebrae for clues about how ancient sharks lived and what they looked like.
Sharks shed teeth as they grow. Many, if not most, of the sharks' teeth we collect in Kansas are these shed teeth. On occasion, a collector is fortunate enough to find a jaw plate intact.
They were, and are, very successful predators.
Class Mammalia
Mammals are warm-blooded animals with hair and milk glands. Humans are mammals, as are dogs and cats. Fossil mammals found in Kansas include mammoths, horses, camels, and beavers.
Class Osteichthyes
This class is the bony fish. They first appeared during the Devonian Period, and are the most successful of all aquatic animals. Their skin is usually covered with thin, bony scales. Their skeletons, unlike sharks' skeletons, have been well-preserved.
The most famous bony fish in the Kansas fossil record is the "fish within a fish" on display at the Sternberg Museum in Hays. A large Xiphactinus did not survive its final meal of a much smaller Gillicus.
It is common to find vertebrae, tails, fins, and teeth in the chalk beds of western Kansas.
Class Reptilia
Reptiles are cold-blooded vertebrate animals that lay eggs and breath air. They evolved from amphibians during the Pennsylvanian Period and were the dominant land vertebrates during the late Paleozoic and Mesozoic Eras. This class includes turtles, snakes, and lizards, and the extinct plesiosaurs, mosasurs, pteranodons, and dinosaurs.