Opiliones in the context of Dyspnoi

The subphylum Chelicerata (from Neo-Latin, from French chélicère, from Ancient Greek χηλή (khēlḗ) 'claw, chela' and κέρας (kéras) 'horn') constitutes one of the major subdivisions of the phylum Arthropoda. Chelicerates include the sea spiders, horseshoe crabs, and arachnids (including harvestmen, scorpions, spiders, solifuges, ticks, and mites, among many others), as well as a number of extinct lineages, such as the eurypterids (sea scorpions) and chasmataspidids.

Chelicerata split from Mandibulata by the mid-Cambrian, as evidenced by stem-group chelicerates like Habeliida and Mollisonia present by this time. The surviving marine species include the four species of xiphosurans (horseshoe crabs), and possibly the 1,300 species of pycnogonids (sea spiders), if the latter are indeed chelicerates. On the other hand, there are over 77,000 well-identified species of air-breathing chelicerates, and there may be about 500,000 unidentified species.

Arachnids are arthropods in the class Arachnida (/əˈræknɪdə/) of the subphylum Chelicerata. Arachnida includes, among others, spiders, scorpions, ticks, mites, pseudoscorpions, harvestmen, camel spiders, whip spiders and vinegaroons.

Adult arachnids have eight legs attached to the cephalothorax. In some species the frontmost pair of legs has converted to a sensory function, while in others, different appendages can grow large enough to take on the appearance of extra pairs of legs.

The chelicerae (/kəˈlɪsəriː/) are the mouthparts of the subphylum Chelicerata, an arthropod group that includes arachnids, horseshoe crabs, and sea spiders. Commonly referred to as "jaws", chelicerae may be shaped as either articulated fangs, or as a type of pincers. Some chelicerae, such as those found on nearly all spiders, are hollow and contain (or are connected to) venom glands, used to inject venom into prey or a perceived threat. Both pseudoscorpions and harvestmen — neither of which have that venom channel — have additional structures on their chelicerae that are used for grooming (papillae in pseudoscorpions, cheliceral teeth in Opiliones). In many spider species, males and females have sexually dimorphic chelicerae.

Arachnology, from Ancient Greek ἀράχνη (arákhnē), meaning "spider", and λόγος (lógos), meaning "study", is the scientific study of arachnids, which comprise spiders and related invertebrates such as scorpions, pseudoscorpions, harvestmen, ticks, and mites. Those who study spiders and other arachnids are arachnologists. More narrowly, the study of spiders alone (order Araneae) is known as araneology.

The word "arachnology" from Ancient Greek ἀράχνη (arákhnē), meaning "spider", and λόγος (lógos), meaning "study". The Ancient Greek word for "spider" itself refers to Arachne, the female protagonist of an ancient tale of the Greek Mythology.

Bitterfeld amber is amber found near the town of Bitterfeld in Saxony-Anhalt, Germany. While visually similar to the better known Baltic amber and often historically considered to be redeposited Baltic amber, chemical analysis shows that it is distinct from Baltic amber. The amber is thought to originate Eocene epoch, around the same time as Baltic amber. Like Baltic amber, the amber is renowned for its fossil inclusions such as those of arachnids and insects. The amber is found deposited in sands and silts of the Cottbus Formation, which is thought to be of late Oligocene age, considerably younger than the amber itself. Some fossil animal species are shared between Baltic and Bitterfeld ambers, supporting the idea that they were deposited at the same time, while both ambers have species apparently unique to them. The amber bearing deposit was excavated as part of a lignite coal mining operation active from 1975 to 1993, which resulted in over 400 tonnes of amber being unearthed. Compared to Baltic amber, the Bittefeld amber has been subject to considerably less research. The amber likely originated from a forested environment, perhaps a swamp forest. The source tree is suggested to have either belonged to Sciadopityaceae or to Pinaceae.