They are not true spiders. One important difference is that phalangids have only one oval shaped body segment. They have two eyes. They have scent glands that secrete a peculiar smelling fluid when disturbed. Some are predators and some are scavengers or plant eaters.
Most species live for a year or two.
This extinct group of arthropods lived in the Paleozoic era. They were flattened like isopods and had three distinct divisions of the body. They had a pair of antennae and their appendages were all similar and leglike. Trilobites were marine animals. Most have 30 or more legs with most body segments having two pairs per segment.