Backbones Ahead

Animals like trilobites and scorpions that lived inside an exoskeleton had outer protection and support. Because they always outgrew their own skeletons, however, they had to shed their exoskeletons and grow new, larger ones.

About 500 million years ago the first vertebrates appeared. Vertebrates are animals with inside support from a jointed backbone. They can grow and move more easily than animals covered with an exoskeleton.

The first vertebrates were jawless fish covered with bony armor plates. Their mouths were open holes for sucking up bits of food. After about 50 million years, fish evolved jaws and swam about chasing other animals for food.

Fish continued to change, becoming more streamlined and developing fins and tails shaped for better movement. Sharks, which are fish with skeletons made of cartilage (softer than bone), first appeared some 380 million years ago. About 20 million years later, more advanced fish with skeletons and fins similar to many of today’s fish were common. The time from about 410 to 360 million years ago, when so much vertebrate evolution was happening, has been called the “Age of Fishes.”

Discover the mystery animal that goes with the backbone in the puzzle to the right. First solve the math problems. Then find the answers to all the math problems in the puzzle and color the shapes containing the answers. (Use only one color. But beware! Each answer may be found in more than one shape. And some shapes have wrong answers and should not be colored.) The answer page gives you this ancient creature’s scientific name.