''Haliestes'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

sea spider Sea spiders are marine arthropods of the class (biology), class Pycnogonida, hence they are also called pycnogonids (; named after ''Pycnogonum'', the type genus; with the suffix '). The class includes the only now-living order (biology), order P ...

(pycnogonid) from the

Silurian The Silurian ( ) is a geologic period and system spanning 23.5 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the third and shortest period of t ...

aged

Coalbrookdale Formation Coalbrookdale Formation, earlier known as Wenlock Shale or Wenlock Shale Formation and also referred to as Herefordshire Lagerstätte in palaeontology, is a fossil-rich deposit ('' Konservat-Lagerstätte'') in Powys and Herefordshire at the Engl ...

England England is a Countries of the United Kingdom, country that is part of the United Kingdom. It is located on the island of Great Britain, of which it covers about 62%, and List of islands of England, more than 100 smaller adjacent islands. It ...

. It contains a single

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

, ''Haliestes dasos''. The species was first described by David Siveter et al. in 2004.

Morphology

''Haliestes'' is a tiny sea spider measured only up to 5.7 mm in body length. Ocular tubercle is evident at the front, but it is unknown if it bore eyes or not. The tubular

proboscis A proboscis () is an elongated appendage from the head of an animal, either a vertebrate or an invertebrate. In invertebrates, the term usually refers to tubular arthropod mouthparts, mouthparts used for feeding and sucking. In vertebrates, a pr ...

facing ventrally below its cephalon. The trunk segments are narrowed. The reduced abdomen was divided by 3 tiny segments. All appendages are well developed. The chelifores featured a robust, upward-facing

pincer Pincer may refer to: *Pincers (tool) *Pincer (biology), part of an animal *Pincer ligand, a terdentate, often planar molecule that tightly binds a variety of metal ions *Pincer (Go), a move in the game of Go *"Pincers!", an episode of the TV series ...

, connected to the front by a 2-segmented scape. The

palp Pedipalps (commonly shortened to palps or palpi) are the secondary pair of forward appendages among chelicerates – a group of arthropods including spiders, scorpions, horseshoe crabs, and sea spiders. The pedipalps are lateral to the chelicera ...

s and ovigers are subequal to each other, each possess 9 segments and a hooked terminal claw. The 8 legs are over twice of its body length, sharing some traits with the younger

Hunsrück The Hunsrück () is a long, triangular, pronounced mountain range, upland in Rhineland-Palatinate, Germany. It is bounded by the valleys of the Moselle (river), Moselle-Saar (north-to-west), the Nahe (south), and the Rhine (east). It is continued ...

pycnogonids (e.g. ''

Palaeoisopus ''Palaeoisopus'' is a genus of fossil pycnogonid (sea spider). The only known species is ''Palaeoisopus problematicus'' from the Lower Devonian Hunsrück Slate of Germany. It is characterized by several features unusual for a pycnogonid, such as ...

'', '' Pentapantopus'') such as annulated coxa 1, paddle-like segments lined with long setae and hooked, robust terminal claw. The first leg pair have less annulations (3) and segments (8) than the other leg pairs (5 annulations and 9 total segment count).

Paleoecology

''Haliestes'' is considered to be a

nektonic Nekton or necton (from the ) is any aquatic organism that can actively and persistently propel itself through a water column (i.e. swimming) without touching the bottom. Nektons generally have powerful tails and appendages (e.g. fins, pleopods ...

predator Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common List of feeding behaviours, feeding behaviours that includes parasitism and micropredation ...

, swimming by using its legs and hunting with its cephalic appendages.

References

Pycnogonid genera Silurian arthropods of Europe Fossils of England Monotypic chelicerate genera Prehistoric chelicerate genera {{chelicerata-stub