The Palpimanoidea or palpimanoids, also known as assassin spiders, are a group of

araneomorph The Araneomorphae (also called the Labidognatha) are an infraorder of spiders. They are distinguishable by chelicerae (fangs) that point diagonally forward and cross in a pinching action, in contrast to the Mygalomorphae (tarantulas and their cl ...

spiders, originally treated as a superfamily. As with many such groups, its

circumscription Circumscription may refer to: *Circumscribed circle * Circumscription (logic) *Circumscription (taxonomy) *Circumscription theory, a theory about the origins of the political state in the history of human evolution proposed by the American anthrop ...

has varied. , the following five families were included: *

Archaeidae Archaeidae, also known as assassin spiders and pelican spiders, is a spider family with about ninety described species in five genera. It contains small spiders, ranging from long, that prey exclusively on other spiders. They are unusual in that ...

Huttoniidae Huttoniidae is a family of ecribellate araneomorph spiders containing a single genus, ''Huttonia'', itself containing a single described species, ''Huttonia palpimanoides''. It is known only from New Zealand. Very few specimens of the genus were ...

* Mecysmaucheniidae *

Palpimanidae Palpimanidae, also known as palp-footed spiders, is a family of araneomorph spiders first described by Tamerlan Thorell in 1890. They are widely distributed throughout the tropical and subtropical regions of the world, the Mediterranean and one in ...

* Stenochilidae Many palpimanoids specialize in preying on other spiders, hence the name "assassin spiders". They have various adaptations for catching prey, including enlarged spade-like front legs, and heads raised up on a "neck" with long

chelicerae The chelicerae () 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 similarly ...

("jaws"). Fossils suggest that the group was once widespread, but most species are now found in the Southern Hemisphere. Morphological studies support the

monophyly In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic grou ...

of the group, although molecular studies have produced different results.

Description

Many palpimanoids, particularly members of the families Archaeidae, Huttoniidae and Stenochilidae, specialize in preying on other spiders, hence the description "assassin spiders". They enter the retreats and webs of other spiders and seize them. Members of the families Huttoniidae, Palpimanidae and Stenochilidae have extensive

scopulae Scopulae, or scopula pads, are dense tufts of hair at the end of a spiders's legs. They are found mostly on hunting spiders, especially Lycosidae and Salticidae. Scopulae consist of microscopic hairs, known as setae, which are each covered in even ...

on the sides of their often enlarged front legs, which enable them to both seize and manipulate prey. Members of the family Archaeidae have much smaller scopulae, but have a highly modified

prosoma The cephalothorax, also called prosoma in some groups, is a tagma of various arthropods, comprising the head and the thorax fused together, as distinct from the abdomen behind. (The terms ''prosoma'' and ''opisthosoma'' are equivalent to ''cepha ...

(cephalothorax), in which a long narrow "neck" separates a "head" portion from the rest of the prosoma. The long neck is matched by long

. Members of the Mecysmaucheniidae also have an elongated prosoma and chelicerae, although less so than archaeids. When hunting prey, mecysmaucheniids hold their chelicerae widely open. Long, forward directed hairs (setae) appear to act as triggers; when these are touched by prey, the chelicerae rapidly snap shut, enabling mecysmaucheniids to catch fast-moving prey, such as

springtail Springtails (Collembola) form the largest of the three lineages of modern hexapods that are no longer considered insects (the other two are the Protura and Diplura). Although the three orders are sometimes grouped together in a class called Ento ...

s. Zephyrarchaea grayi anatomy.jpg, '' Zephyrarchaea grayi'' (Archaeidae), showing the "neck" and long chelicerae (bar = 1 mm) Zearchaea clypeata female.jpg, '' Zearchaea clypeata'' (Mecysmaucheniidae), showing the less long "neck" and chelicerae Boagrius sp.jpg, ''

Boagrius ''Boagrius'' is a genus of palp-footed spiders that was first described by Eugène Louis Simon in 1893. it contains only two species, found only in Indonesia, Malaysia, and Tanzania: '' B. incisus'' and '' B. pumilus''. See also * List of Pal ...

'' sp. (Palpimanidae), showing the enlarged front legs (bar = 1 mm)

Phylogeny

In 1984, Raymond R. Forster and Norman I. Platnick proposed that some groups previously considered araneoid actually belonged in the distantly related Palpimanoidea, including the then families Holarchaeidae, Micropholcommatidae,

Mimetidae Pirate spiders, members of the family Mimetidae, are araneomorph spiders which typically feed on other spiders. The family Mimetidae contains roughly 200 species divided among 12 genera, of which ''Mimetus'' and ''Ero'' are the most common. Mim ...

and

Pararchaeidae Malkaridae is a small family of araneomorph spiders first described by Valerie Todd Davies in 1980. In 2017, the family Pararchaeidae was brought into synonymy with Malkaridae. Genera , the World Spider Catalog accepts the following genera: *'' ...

. Subsequent phylogenetic studies have rejected this proposal, firmly placing them in Araneoidea. Studies published in 2012 and 2013, using morphological, molecular and fossil evidence, agreed that Palpimanoidea is monophyletic. Molecular data suggested the following relationship between the five families comprising the Palpimanoidea, although three of the families were represented by only one species each: Using only morphological data produced a different arrangement of the families: A large molecular phylogenetic study, first published online in 2016, grouped the five families in the same way, but suggested that the Palpimanoidea, together with part of the non-monophyletic

Leptonetidae Leptonetidae is a relatively primitive family of spiders first described by Eugène Simon in 1890. It is made up of tiny haplogyne spiders, meaning they lack the hardened external female genitalia. Their six eyes are arranged in a semicircle of f ...

, were a

paraphyletic In taxonomy (general), taxonomy, a group is paraphyletic if it consists of the group's most recent common ancestor, last common ancestor and most of its descendants, excluding a few Monophyly, monophyletic subgroups. The group is said to be pa ...

group basal to the large

Entelegynae The Entelegynae or entelegynes are a subgroup of araneomorph spiders, the largest of the two main groups into which the araneomorphs were traditionally divided. Females have a genital plate ( epigynum) and a "flow through" fertilization system; m ...

clade: Nevertheless, the authors preferred to accept the earlier conclusion based on multiple lines of evidence that the Palpimanoidea are a monophyletic group. Although the morphological data suggests that the two families with "necks" in the prosoma, Archaeidae and Mecysmaucheniidae, are sisters, molecular data suggests otherwise. It is now believed that the elongated and elevated "neck" has evolved independently in these two families, as well as in the more distantly related

Malkaridae Malkaridae is a small family of araneomorph spiders first described by Valerie Todd Davies in 1980. In 2017, the family Pararchaeidae was brought into synonymy with Malkaridae. Genera , the World Spider Catalog accepts the following genera: *'' ...

(Pararchaeidae).

Distribution

The Palpimanoidea are mainly found in the Southern Hemisphere. Archaeidae, Huttoniidae and Mecysmaucheniidae have a

Gondwana Gondwana () was a large landmass, often referred to as a supercontinent, that formed during the late Neoproterozoic (about 550 million years ago) and began to break up during the Jurassic period (about 180 million years ago). The final stages ...

n distribution, with species native to South America, South Africa, Madagascar, Australia and New Zealand. The Stenochilidae are found in South-east Asia. Only the Palpimanidae cross into the

Northern Hemisphere The Northern Hemisphere is the half of Earth that is north of the Equator. For other planets in the Solar System, north is defined as being in the same celestial hemisphere relative to the invariable plane of the solar system as Earth's Nort ...

, with a few species reaching Central Asia and China. Palpimanoids were once more widely distributed; thus 12 fossil genera of Archaeidae have been found in the Northern Hemisphere.

References

{{Taxonbar, from=Q54905 Araneomorphae Arachnid superfamilies