| Dietericambria Temporal range: | |
|---|---|
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | Ichthyostraca |
| Subclass: | Pentastomida |
| Genus: | † Dietericambria Peel 2022 |
| Species: | †D. hensoniensis |
| Binomial name | |
| †Dietericambria hensoniensis Peel 2022 | |
Dietericambria hensoniensis is a Cambrian pentastomid from the Henson Gletscher Formation of Greenland. It is the oldest known pentastomid, being at least 15 million years older than the forms recorded from the Orsten. [1]
Dietericambria was at least 1.2 mm long, with cylindrical segments. (Due to it only being known from fragmentary specimens, any lengths are purely estimates.) It resembles Aengapentastomum , however it has much smaller, unsegmented head limbs. Dietericambria also has an unusual complex of flanges on the ventral surface of the head. The trunk seems to have had limbs, with their sockets being preserved, however their shape is unknown. Unusually, instead of the lateral position of Orsten pentastomids, these limbs are positioned ventrally, similar to that of tardigrades. While hooks similar to the cephalic hooks of modern pentastomids are known from the same formation, they were likely from much larger forms, possibly adults of the species. The position of the mouth is unknown, and while the circular pillar within the flange complex does appear to be a mouth, further examination shows it has the same papillae as the rest of the integument. Dietericambria seems to have been parasitic, as suggested by the flange complex and cephalic limbs, alongside the possible hooks, however what it parasitised is unclear, with both conodonts and dinocaridids being proposed due to their abundant nature and soft bodies. Whether it was endoparasitic or ectoparasitic is also unclear. [1]
Dietericambria honours Dieter Walossek, who helped describe numerous Orsten fossils including stem-pentastomids, alongside acknowledging the age of the fossil. The species name hensoniensis reflects its origin from the Henson Gletscher Formation. [1]
Lobopodians are members of the informal group Lobopodia, or the formally erected phylum Lobopoda Cavalier-Smith (1998). They are panarthropods with stubby legs called lobopods, a term which may also be used as a common name of this group as well. While the definition of lobopodians may differ between literatures, it usually refers to a group of soft-bodied, marine worm-like fossil panarthropods such as Aysheaia and Hallucigenia. However, other genera like Kerygmachela and Pambdelurion are often referred to as “gilled lobopodians”.
The Orsten fauna are fossilized organisms preserved in the Orsten lagerstätte of Cambrian rocks, notably at Kinnekulle and on the island of Öland, all in Sweden.
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.
Fuxianhuia is a genus of Lower Cambrian fossil arthropod known from the Chengjiang fauna in China. Its purportedly primitive features have led to its playing a pivotal role in discussions about the euarthropod stem group. Nevertheless, despite being known from many specimens, disputes about its morphology, in particular its head appendages, have made it one of the most controversial of the Chengjiang taxa, and it has been discussed extensively in the context of the arthropod head problem.
Megacheira is an extinct class of predatory arthropods defined by their possession of spined "great appendages". Their taxonomic position is controversial, with studies either considering them stem-group euarthropods, or stem-group chelicerates. The homology of the great appendages to the cephalic appendages of other arthropods is also controversial. Uncontested members of the group were present in marine environments worldwide from the lower Cambrian to the upper Ordovician.
Radiodonta is an extinct order of stem-group arthropods that was successful worldwide during the Cambrian period. Radiodonts are distinguished by their distinctive frontal appendages, which are morphologically diverse and were used for a variety of functions. Radiodonts were among the earliest large predators, but they also included sediment sifters and filter feeders. Some of the most famous species of radiodonts are the Cambrian taxa Anomalocaris canadensis, Hurdia victoria, Peytoia nathorsti, Titanokorys gainesi, Cambroraster falcatus and Amplectobelua symbrachiata. The later surviving members include the subfamily Aegirocassisinae from the Early Ordovician of Morocco and the Early Devonian member Schinderhannes bartelsi from Germany.
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.
Fritzolenellus is an extinct genus from a well-known class of fossil marine arthropods, the trilobites, with three known species. It lived during the early part of the Botomian stage, which lasted from approximately 524 to 518.5 million years ago. This faunal stage was part of the Cambrian Period. Fritzolenellus occurred in parts of the paleocontinent Laurentia in what are now Northwestern Canada, Northwestern Scotland, and North-Greenland.
The Henson Gletscher Formation is a geologic formation in Greenland. It preserves fossils dating back to the Cambrian period. It is named after the Henson Glacier (Greenland). It preserves numerous phosphatocopines and bradoriids, alongside priapulid larvae such as Inuitiphlaskus and pentastomids like Dietericambria.
The Buen Formation is a geologic formation and Lagerstätte in Peary Land, North Greenland. The shale preserves fossils dating back to the Early Cambrian period.
Henson Glacier, is one of the major glaciers in northern Greenland.
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.
Cambrocaris baltica is an Upper Cambrian arthropod from Poland.
Rehbachiella is a genus of Cambrian crustacean comprising the only species Rehbachiella kinnekullensis. It is a possible branchiopod from the Orsten of Sweden.
Aengapentastomum is a Cambrian genus of pentastomid from the Orsten of Sweden, containing one species, Aengapentastomum andresi.
Boeckelericambria is a Cambrian genus of pentastomid from the Orsten of Sweden, containing one species, Boeckelericambria pelturae.
Haffnericambria is a Cambrian genus of pentastomid from the Orsten of Sweden, containing one species, H. trolmeniensis.
Heymonsicambria is a Cambrian genus of pentastomid from the Orsten of Sweden, containing five species, H. kinnekullensis, H. scandica, H. repetskii, H. taylori and H. gossmannae.