Fossilized psuedomorph of calcite after ammonite halve to reveal the internal chambers lined with calcite crystals. The ammonite has been internall...

Fossilized psuedomorph of calcite after ammonite halve to reveal the internal chambers lined with calcite crystals. The ammonite has been internall...

Fossilized psuedomorph of calcite after ammonite halve to reveal the internal chambers lined with calcite crystals. The ammonite has been internall...

Fossilized psuedomorph of calcite after ammonite halve to reveal the internal chambers lined with calcite crystals. The ammonite has been internall...

Ptychopariida is a large, heterogeneous order of trilobite containing some of the most primitive species known. The earliest species occurred in th...

Brittle stars, or ophiuroids, are echinoderms in the class Ophiuroidea, closely related to starfish. They crawl across the sea floor using their fl...

Brittle stars, or ophiuroids, are echinoderms in the class Ophiuroidea, closely related to starfish. They crawl across the sea floor using their fl...

Brittle stars, or ophiuroids, are echinoderms in the class Ophiuroidea, closely related to starfish. They crawl across the sea floor using their fl...

Brittle stars, or ophiuroids, are echinoderms in the class Ophiuroidea, closely related to starfish. They crawl across the sea floor using their fl...

Brittle stars, or ophiuroids, are echinoderms in the class Ophiuroidea, closely related to starfish. They crawl across the sea floor using their fl...

Brittle stars, or ophiuroids, are echinoderms in the class Ophiuroidea, closely related to starfish. They crawl across the sea floor using their fl...

Brittle stars, or ophiuroids, are echinoderms in the class Ophiuroidea, closely related to starfish. They crawl across the sea floor using their fl...