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”.
Dinocaridida is a proposed fossil taxon of basal arthropods, which flourished during the Cambrian period and survived up to Early Devonian. Characterized by a pair of frontal appendages and series of body flaps, the name of Dinocaridids refers to the suggested role of some of these members as the largest marine predators of their time. Dinocaridids are occasionally referred to as the 'AOPK group' by some literatures, as the group compose of Radiodonta, Opabiniidae, and the "gilled lobopodians" Pambdelurion and Kerygmachelidae. It is most likely paraphyletic, with Kerygmachelidae and Pambdelurion more basal than the clade compose of Opabiniidae, Radiodonta and other arthropods.
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.
Parapeytoia is a genus of Cambrian arthropod. The type and only described species is Parapeytoia yunnanensis, lived over 518 million years ago in the Maotianshan shales of Yunnan, China. Unidentified fossils from the same genus also had been discovered from the nearby Wulongqing Formation.
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.
Saperion is an extinct genus of trilobite-like arthropod. It lived during the late Atdabanian stage, which lasted from 521 to 514 million years ago during the early part of the Cambrian Period. It was found in the Maotianshan Shales of Yunnan, China. Similar to the closely-related Skioldia and Tegopelte, the head shield and trunk tergites were fused into a single plate. There are about 19 furrows indicating the original trunk segments. a small anterior sclerite articulated to the front of its head. A pair of antennae and lateral eyes located ventrally behind the anterior sclerite, lateral to the hypostome. Saperion reached 151 mm in length and had nearly 25 pairs of biramous limbs for walking.
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 to middle Cambrian.
Schinderhannes bartelsi is a species of hurdiid radiodont (anomalocaridid), known from one specimen from the Lower Devonian Hunsrück Slates. Its discovery was astonishing because the latest definitive radiodonts were known only from the Early Ordovician, at least 66 million years earlier than this taxon.
Haikoucaris is a genus of megacheiran arthropod that contains the single species Haikoucaris ercaiensis. It was discovered in the Cambrian Chengjiang biota of China.
Radiodonta is an extinct order of stem-group arthropods that was successful worldwide during the Cambrian period. They may be referred to as radiodonts, radiodontans, radiodontids, anomalocarids, or anomalocaridids, although the last two originally refer to the family Anomalocarididae, which previously included all species of this order but is now restricted to only a few species. Radiodonts are distinguished by their distinctive frontal appendages, which are morphologically diverse and used for a variety of functions. Radiodonts included the earliest large predators known, 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 gainessii, 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.
Cucumericrus ("cucumber-leg") is an extinct genus of stem-arthropod. The type and only species is Cucumericrus decoratus, with fossils discovered from the Maotianshan Shales of Yunnan, China.
Cardiodictyon is a genus of lobopodian known from 518 millions years old Chengjiang Lagerstätte. 525 millions years old partial fossil is also reported. It has ~25 pairs of legs, each associated with a pair of dorsal plates.
Amplectobeluidae is a clade of Cambrian radiodonts. It currently includes five definitive genera, Amplectobelua, Lyrarapax, Ramskoeldia, Guanshancaris and a currently unnamed genus from the lower Cambrian aged Sirius Passet site in Greenland. There is also a potential fifth genus, Houcaris, but that genus has become problematic in terms of its taxonomic placement.
Lyrarapax is a radiodont genus of the family Amplectobeluidae that lived in the early Cambrian period 520 million years ago. Its neural tissue indicates that the radiodont frontal appendage is protocerebral, resolving parts of the arthropod head problem and showing that the frontal appendage is homologous to the antennae of Onychophorans and labrum of euarthropods. Its fossilized remains were found in Yunnan in southwestern China. A second species was described in 2016, differing principally in the morphology of its frontal appendages. It is a small animal, with L. unguispinus and L. trilobus measuring up to 8.3 cm (3.3 in) and 3.9 cm (1.5 in) in body length respectively.
Hurdiidae is an extinct cosmopolitan family of radiodonts, a group of stem-group arthropods, which lived during the Paleozoic Era. It is the most long-lived radiodont clade, lasting from the Cambrian period to the Devonian period.
The Artiopoda is a grouping of extinct arthropods that includes trilobites and their close relatives. It was erected by Hou and Bergström in 1997 to encompass a wide diversity of arthropods that would traditionally have been assigned to the Trilobitomorpha. Trilobites, in part due to abundance of findings owing to their mineralized exoskeletons, are by far the best recorded, diverse, and long lived members of the clade. Other members, which lack mineralised exoskeletons, are known mostly from Cambrian deposits.
Retifacies abnormalis is an extinct arthropod that lived in the lower Cambrian. Its fossil remains have been found in the Maotianshan Shales of Yunnan, China. It is a member of the Artiopoda, and closely related to Pygmaclypeatus.
Fuxianhuiida is an extinct clade of arthropods from the Cambrian of China. All currently known species are from Cambrian Series 2 aged deposits in Yunnan Province, including the Chengjiang biota. Although historically suggested to be members of the arthropod stem group recent research has suggested that they may be closely related to mandibulates. Many specimens are known with exceptional soft tissue preservation, including preserved guts and neural tissue, which given their basal phylogenetic position makes them important in understanding the evolution of Arthropoda as a whole. They reach a size of up to 15 cm, and are interpreted as benthic predators and scavengers. The Fuxianhuiid exoskeleton is unmineralised, and the number of tergites ranges from 15 to over 40. The cephalon is covered by a head shield and contains stalked eyes connected by the anterior sclerite, antennae, a butterfly shaped hyposome and a posterior facing mouth. Fuxianhuiids possess specialized post-antennal appendages with serrated edges used for food processing. The presence of gnathobases in members of Chengjiangocardidae suggests that they were capable of durophagy. In most Fuxianhuiids, the thorax tergites narrow posteriorly, terminating in either a swimming paddle or paired flukes with a tail spine. In members of Fuxianhuiidae the thorax is divided into two sections, the anterior wide opisthothorax and the posterior narrow limbless tail-like abdomen.
Kylinxia is a genus of extinct arthropod described in 2020. It was described from six specimens discovered in Yu'anshan Formation in southern China. The specimens are assigned to one species Kylinxia zhangi. Dated to 518 million years, the fossils falls under the Cambrian period. Announcing the discovery on 4 November 2020 at a press conference, Zeng Han of the Nanjing Institute of Geology and Paleontology, said that the animal "bridges the evolutionary gap from Anomalocaris to true arthropods and forms a key ‘missing link’ in the origin of arthropods," which was "predicted by Darwin’s evolutionary theory." The same day the formal description was published in Nature.
Luolishania is an extinct genus of lobopodian panarthropod and known from the Lower Cambrian Chiungchussu Formation of the Chengjiang County, Yunnan Province, China. A monotypic genus, it contains one species Luolishania longicruris. It was discovered and described by Hou Xian-Guang and Chen Jun-Yuan in 1989. It is one of the superarmoured Cambrian lobopodians suspected to be either an intermediate form in the origin of velvet worms (Onychophora) or basal to at least Tardigrada and Arthropoda. It is the basis of the family name Luolishaniidae, which also include other related lobopods such as Acinocricus, Collinsium, Facivermis, and Ovatiovermis. Along with Microdictyon, it is the first lobopodian fossil discovered from China.
