1. Chelicerates are now predominently terrestrial animals, with most marine Chelicerates, including all of the eurypterids, now extinct

2. The first confirmed Chelicerate fossils, the eurypterids, date from 445 million years ago in the late Ordovician period

3. Chelicerate arthropods are an ancient group that includes eurypterids (extinct), horseshoe crabs, spiders, ticks and mites, scorpions, and sea spiders

4. Definition of Chelicerata : a subphylum or other division of the phylum Arthropoda comprising forms having chelicerae and lacking antennae and including the horseshoe crabs and eurypterids, spiders, scorpions, and sea spiders A fossil eurypterid, representing the Chelicerata.

5. Animals: Arthropods-Chelicerates Ziser Lecture Notes, 2012.10 1 Arthropods - Chelicerates an ancient group with good fossil record include horse shoe crabs, sea spiders, scorpions, spiders, ticks, mites, sea scorpions most living species are fairly small but some fossil sea scorpions (eurypterids) were 5-6’long; a …

6. The subphylum Chelicerata (New Latin, from French chélicère, from Greek χηλή, khēlē "claw, chela" and κέρας, kéras "horn") constitutes one of the major subdivisions of the phylum Arthropoda.It contains the sea spiders, arachnids (including scorpions, spiders, and potentially horseshoe crabs), and several extinct lineages, such as the eurypterids and chasmataspidids.