Cyclocosmia or hatch spider or seal spider, is a genus of spiders in the family Ctenizidae. A unique feature of these arthropods is a sharply truncated abdomen, which ends in a chitinous disc. The disk, reinforced by a system of ribs and grooves, resembles a patterned ancient seal. There are many small, sharp spines on the edges of the disk.
The amazing structure of the abdomen helps cyclocosmids to hide from danger. Sensing trouble, hatchling spiders dig a vertical hole 7 to 15 cm deep in the sand. Then they crawl into their hiding place. They block the entrance to it with their truncated abdomen, creating a kind of "trapdoor".
You can meet unusual spiders in China, Thailand, Guatemala and the southern states of America. Cyclocosmia are one of the oldest arachnids on our planet. According to paleontologists' estimates, the ancestors of modern seal spiders appeared on Earth as early as 100 million years ago.