TRILOBITE: Asaphus kowalewskii
This is a very good specimen of Asaphus kowalewskii, a stalk-eyed, Ordovician period trilobite from the St. Petersburg region in Russia, some 470 million years old.
Trilobites are a type of extinct arthropod probably most closely related
to modern Horseshoe crabs. With a growing number of predators and
adapted to diverse habitats, various species of trilobites developed
complex eyes, retractable antennae, and even protective spines. Their
exoskeletons were composed of extremely hard calcite and calcium
phosphate minerals to protect the soft internal organs, and as a result
they are quite well represented in the fossil record.
Trilobite fossils range in size from a fraction of an inch to over two feet in length, and are found all over the world.