Training Module 5 – Cretaceous Creatures

To which category does your fossil belong?

1. Isolated teeth

2. Jaws and tooth plates

3. Vertebrae

4. Scales, shells, and plates

5. Bones and bone fragments

Try again! Scales, shells, and plates usually have broad surfaces that are flat or bumpy.

Try again! Jaws and tooth plates usually have rows of teeth or sockets for teeth that fell out.

Try again! Vertebrae usually circular cups at their ends and struts that stick out along the rim.

Try again! Bone fragments usually have broken cross sections that look like a hollow tube or like the end of a broken pencil.

ID Sheet 4

1. My tooth is shaped like a column.

2. My tooth has multiple cusps that look like big bumps.

3. My tooth is shaped like a diamond.

4. My tooth is flat and shaped like a triangle and may have tiny serrations along the edge.

5. My tooth is big at the top, shaped like a hexagon, and attached to two thick roots.

ID Sheet 4-A

1. My tooth is tall and pointy.

2. My tooth has a rounded top.

3. My tooth is shaped like a triangle, is clear at the tip, has small holes near the base, and does not have roots.

4. My tooth is flat with one raised point that is shiny and/or curved and it does not have roots.

Try again! Your fossil should have a single point and no roots.

Try again! Focus on the top of your fossil. It should have a sharp point on the end.

Try again! Look at your fossil from the bottom. The base should be shaped like a circle with small struts that stick out along the edges.

Try again! Your fossil should be wider at the base and pointed at the top.

You did it! You found a skin denticle from the ray Myledaphus!

A skin denticle from the rae Myledaphus with arrow

Fun Facts!

1. Skin denticles are teeth-like scales that cover the body of rays, skates, and sharks.
2. In modern sharks and rays, the skin denticles all point toward the tail. This causes the skin to feel smooth in one direction and rough like sandpaper in the other, which helps them swim faster.
3. The placoid scales of sharks and rays do not grow bigger as the fish grows bigger. Instead, new scales are created in between the old ones to cover the animal’s increased body size.

Place your fossil in the correct box on the Fossil Training Sheet.

Click here to identify another microfossil.

Try again! Spin the fossil around and note the shape of ridges running up and down. The ridges that run up and down should flare outward near the bottom.

Try again! The tip of your fossil should be pointy.

Try again! The tip of your fossil should be slightly hooked.