| Cambropycnogon Temporal range: Cambrian, | |
|---|---|
 | |
| Reconstruction | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Subphylum: | Chelicerata |
| Class: | Pycnogonida |
| Genus: | † Cambropycnogon Waloszek and Dunlop, 2002 |
| Species: | †C. klausmuelleri |
| Binomial name | |
| †Cambropycnogon klausmuelleri Waloszek and Dunlop, 2002 | |
Cambropycnogon klausmuelleri is a presumed pycnogonid larva from the Upper Cambrian Orsten, having been referred to before description as "Larva D". [1]
Cambropycnogon is an early-stage pycnogonid larva (although this classification has been disputed [2] ) around 270 micrometers long, with three pairs of post-cheliceral appendages as well as the chelicerae that mark it as a possible pycnogonid. It also has two large caudal growths from its posterior end, the purpose of which is unknown. Cambropycnogon is covered in small spines roughly 1 micrometer long, as well as larger thorns behind its gnathobases. Its chelicerae are short and stout, resembling pincers, and the larva has a relatively large head shield. Cambropycnogon's morphology matches that of early sea spider larvae such as the protonymph and semaphoront, with it being markedly distinct from all other Orsten fossils. [1]
Cambropycnogon derives from its assumed position within Pycnogonida, as well as the fact that it dates from the Cambrian. Its specific name, klausmuelleri honours the discoverer of the Orsten, Dr. Klaus Müller. [1]
Cambropycnogon is known from six specimens, all found in Kinnekulle. [1]
The subphylum Chelicerata constitutes one of the major subdivisions of the phylum Arthropoda. Chelicerates include the sea spiders, horseshoe crabs, and arachnids, as well as a number of extinct lineages, such as the eurypterids and chasmataspidids.
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 as a type of pincers. Some chelicerae, such as those found on nearly all spiders, are hollow and contain venom glands, used to inject venom into prey or a perceived threat. Both pseudoscorpions and harvestmen have additional structures on their chelicerae that are used for grooming. In Paratrechalea, males and females have shown to have a chelicerae dimorphism, because the chelicerae is used as a mating signal for females.
Sea spiders are marine arthropods of the order Pantopoda, belonging to the class Pycnogonida, hence they are also called pycnogonids. They are cosmopolitan, found in oceans around the world. The over 1,300 known species have leg spans ranging from 1 mm (0.04 in) to over 70 cm (2.3 ft). Most are toward the smaller end of this range in relatively shallow depths; however, they can grow to be quite large in Antarctic and deep waters.
Cheloniellida is a taxon of extinct Paleozoic arthropods. As of 2018, 7 monotypic genera of cheloniellids had been formally described, whose fossils are found in marine strata ranging from Ordovician to Devonian in age. Cheloniellida has a controversial phylogenetic position, with previous studies associated it as either a member or relative of various fossil and extant arthropod taxa. It was later accepted as a member of Vicissicaudata within Artiopoda.
Nymphonidae is a family of sea spiders which has representatives in all the oceans. This family contains some 250 species, most of which are found in the genus Nymphon. Nymphonid bodies are between 1 and 15 mm long, the extent between the points of the legs reaching 150 mm. Most species are predators of hydroids. Like most sea spiders, species in this family have four pairs of legs, except for Pentanymphon antarcticum, which has five pairs, and Sexanymphon mirabilis, which has six pairs.
The (pan)arthropod head problem is a long-standing zoological dispute concerning the segmental composition of the heads of the various arthropod groups, and how they are evolutionarily related to each other. While the dispute has historically centered on the exact make-up of the insect head, it has been widened to include other living arthropods, such as chelicerates, myriapods, and crustaceans, as well as fossil forms, such as the many arthropods known from exceptionally preserved Cambrian faunas. While the topic has classically been based on insect embryology, in recent years a great deal of developmental molecular data has become available. Dozens of more or less distinct solutions to the problem, dating back to at least 1897, have been published, including several in the 2000s.
Marrellomorpha are an extinct group of arthropods known from the Cambrian to the Early Devonian. They lacked mineralised hard parts, so are only known from areas of exceptional preservation, limiting their fossil distribution. The best known member is Marrella, with thousands of specimens found in the Cambrian aged Burgess Shale of Canada. The group is divided up into two major orders, Marrellida and Acercostraca. Marrellida is recognised by the possession of head shields with two or three pairs of elongate spine-like projections, and three pairs of uniramous appendages on the cephalon, while Acercostraca generally have large ovoid carapaces that cover the entire upper half of the body, and five pairs of uniramous cephalic appendages. Both groups have unbranched antennules and a segmented trunk with biramous appendages. Recent research has suggested the previously enigmatic Cambrian trilobite-like arthropods Skania and Primicaris belong to this group. Their phylogenetic position is uncertain, various studies have alternatively placed them in the Arachnomorpha as relatives of Artiopoda, as related to Mandibulata, or as stem group euarthropods. Some authors have proposed that they may be closely related to sea spiders (Pycnogonida) within Chelicerata though the cladistical support for such a relationship is relatively weak.
Liponema brevicorne, commonly known as pom-pom anemone or tentacle shedding anemone, is a species of sea anemone in the family Actiniidae. It is a deep water species and has been relatively little observed. It often remains unattached to a substrate and can roll across the ocean floor propelled by water currents.
Pycnogonum is a genus of sea spiders in the family Pycnogonidae. It is the type genus of the family.
Colossendeis is a genus of sea spider belonging to the family Colossendeidae. These sea spiders are typically found in the deep sea. This genus includes the largest pycnogonids, with leg spans frequently ranging from 40 to 50 cm. The largest sea spider, Colossendeis colossea, can reach a leg span of 70 cm. This genus also includes some bioluminescent sea spiders.
Palaeoisopus is a monotypic genus of fossil pycnogonid, known only by one species, Palaeoisopus problematicus, discovered from the Lower Devonian Hunsrück Slate of Germany. It have several characters unusual for a pycnogonid, such as swimming legs with alternating size, medially-arranged eyes, and most significantly, a long, segmented abdomen, which were highly reduced in modern counterparts.
Cambropachycope is a genus of small extinct Cambrian arthropods, known from the Orsten lagerstätten in southern Sweden. It appears to have several apomorphic features, notably including a single large compound eye.
Phosphatocopina is an extinct group of bivalved arthropods known from the Cambrian period. They are generally sub-milimetric to a few millimetres in size. They are typically only known from isolated carapaces, but some found in Orsten-type phosphatized preservation have their bodies preserved in high fidelity in three dimensions.
Dodecolopoda is a monotypic genus of sea spider in the family Colossendeidae. The only species in this genus is Dodecolopoda mawsoni. This species is notable as one of only two species of sea spider with six pairs of legs and the first such species to be discovered.
Decolopoda is a genus of sea spider belonging to the family Colossendeidae. This genus includes two valid species, D. australis and D. qasimi. As the name of this genus implies, these two species are among the seven species of sea spider with five pairs of legs instead of the usual four leg pairs. The species D. australis is notable as the first polymerous sea spider to be discovered.
Flagellopantopus is an extinct genus of pycnogonid arthropod known from the lower Devonian aged Hunsrück Slate. A single species is currently known, Flagellopantopus blocki, which was described from the Emsian aged Kaub Formation in Germany.
Henningsmoenicaris scutula is a Cambrian genus of arthropod from the Orsten of Sweden. It was formerly named Henningsmoenia, however this name was preoccupied by an ostracod, therefore it was renamed. Its genus name translates to "Henningsmoen's shrimp" after G. Henningsmoen. The species name, scutula is in reference to the large, bowl-shaped carapace.
Sandtorpia vestrogothiensis is a Cambrian arthropod from the Orsten of Sweden. It is known from a single specimen.
Aengapentastomum is a Cambrian genus of pentastomid from the Orsten of Sweden, containing one species, Aengapentastomum andresi.
Colossendeis megalonyx is a species of pycnogonids, also known as sea spiders, in the famly Colossendeidae. The species was first described by Dutch zoologist Dr. Paulus Peronius Cato Hoek after his voyage on the HMS Challenger from 1873-1876.