Chelicerate Fossils | Darwin and Wallace: A Nature & Fossil Store

Chelicerate Fossils



            The Chelicerates are arthropods that consist of arachnids (spiders, scorpions, and kin), merostomates (horseshoe crabs and the extinct “sea scorpions”), and possibly the pycnogonids (“sea spiders”). The main feature that unite these animals are their chelicerae (meaning “claw horn”), which are a pair of appendages positioned in front of the mouth that are primarily used in feeding (though the fang-like chelicerae of spiders are used to inject venom). Another feature of chelicerates are a pair of appendages called pedipalps, which are located in front of the first pair of legs and primarily used as sensors (though scorpions’ pedipalps are in the form of large, prey-grabbing claws). Though most chelicerates are predators, a number of species have adapted herbivory, scavenging, and parasitism. Chelicerates have an ancient origin with the oldest possible chelicerate species known being Sanctacaris uncata of the middle Cambrian period, approximately 505 million years ago. Horseshoe crabs and “sea scorpions” have their origin in the later Ordovician period, while the arachnids would evolve even later in the Silurian period (of which the first scorpions would start out as marine animals). Despite the numerous varieties that have come and gone, chelicerates today number over 113,000 known species and counting.

Click on the images below to see the incredible specimens we offer in our chelicerate fossil selection: