| Caryosyntrips Temporal range: | |
|---|---|
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| Frontal appendages of Caryosyntrips | |
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| Speculative life restoration as a radiodont | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Stem group: | Arthropoda |
| Genus: | † Caryosyntrips Daley & Budd, 2010 |
| Type species | |
| Caryosyntrips serratus Daley & Budd, 2010 | |
| species | |
Caryosyntrips ("nutcracker") is an extinct genus of stem-arthropod which known from Canada, United States and Spain during the middle Cambrian. [1]
Caryosyntrips was first named by Allison C. Daley, Graham E. Budd in 2010 and the type species is Caryosyntrips serratus. [3] Multiple species had been recovered from the Burgess Shale Formation, Canada, Wheeler Shale and Marjum Formation, United States, and Valdemiedes Formation, Spain. [1] [4] The latter contain a large specimen, which was initially misidentified as a body remain of lobopodian (" Mureropodia apae"). [5] [1] [6] [2]
Caryosyntrips is known only from its 14-segmented frontal appendages, which resemble nutcrackers, with the endite (ventral spine)-bearing margin facing each other, and the bell-shaped bases might represent movable articulations with the animal's head. [1] Details of the endites, terminal spines, segmental boundaries and outer margins differ between species. [1] It is thought to have used their frontal appendages in a scissor-like grasping or slicing motion, and were probably durophagous, feeding on hard-shelled organisms. [1] Other structures remain unknown, although a specimen with paired appendages possibly contain other fragmental head sclerites as well. [3] [4]
The size of Caryosyntrips differed between each species. The largest species is C. serratus which is estimated around 20.5–30.2 cm (8.1–11.9 in) long. Other species are much smaller, with the body lengths of C. camurus and C. durus estimated up to 13.7–20.2 cm (5.4–8.0 in) and 12.2–17.9 cm (4.8–7.0 in) respectively. The largest possible specimen (MPZ 2009/1241), identified as C. cf. camurus, would have belonged to an individual measuring between 36.7–54 cm (1.20–1.77 ft) long. [7]
As of 2010s, Caryosyntrips was long considered to be a basal radiodont of uncertain position, usually resolved in a polytomy between euarthropod and radiodont branches. [8] [9] [10] [2] [11] [12] however more recent papers have found that it may sit outside of the monophyletic Radiodonta all together. [12] [13] Due to the unusual morphology of the frontal appendages and the limited extent of known remains, its position within the arthropod stem-group remains uncertain. [1] [13]
| Panarthropoda |
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Dinocaridida is a proposed fossil taxon of basal arthropods, which flourished during the Cambrian period and survived up to the Early to Middle Ordovician. The putative Early Devonian member Schinderhannes bartelsi has been considered questionable by some researchers.
Anomalocaris is an extinct genus of radiodont, an order of early-diverging stem-group arthropods.
Peytoia is a genus of hurdiid radiodont, an early diverging order of stem-group arthropods, that lived in the Cambrian period, containing two species, Peytoia nathorsti from the Miaolingian of Canada and Peytoia infercambriensis from Poland, dating to Cambrian Stage 3. Its two frontal appendages had long bristle-like spines, it had no fan tail, and its short stalked eyes were behind its large head.
Amplectobelua is an extinct genus of late Early Cambrian amplectobeluid radiodont, a group of stem arthropods that mostly lived as free-swimming predators during the first half of the Paleozoic Era.
Anomalocarididae is an extinct family of Cambrian radiodonts, a group of stem-group arthropods.
Pambdelurion is an extinct genus of panarthropod from the Cambrian aged Sirius Passet site in northern Greenland. Like the morphologically similar Kerygmachela from the same locality, Pambdelurion is thought to be closely related to arthropods, combining characteristics of "lobopodians" with those of primitive arthropods.
Jianshanopodia is a monotypic genus of Cambrian lobopodian, discovered from Maotianshan Shales of Yunnan, China.
Schinderhannes bartelsi is a species of stem-group arthropod, possibly a 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. Although some phylogenetic analyses found support for its taxonomic placement as a hurdiid radiodont, other researchers have questioned these assignments.
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 latest surviving members include the Aegirocassisinae from the Early Ordovician of Morocco. The putative Early Devonian member Schinderhannes bartelsi from Germany has been considered questionable by some researchers.
Hurdia is an extinct genus of hurdiid radiodont that lived 505 million years ago during the Cambrian Period. Fossils have been found in North America, China and the Czech Republic.
Stanleycaris is an extinct, monotypic genus of hurdiid radiodont from the middle Cambrian (Miaolingian). The type species is Stanleycaris hirpex. Stanleycaris was described from the Stephen Formation near the Stanley Glacier and Burgess Shale locality of Canada, as well as Wheeler Formation of United States. The genus was characterized by the rake-like frontal appendages with robust inner spines.
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.
Tamisiocaris is a radiodont genus initially only known from frontal appendages from the Cambrian Sirius Passet lagerstatte in northern Greenland. It was initially described initially in 2010. Further study in 2014 revealed that the frontal appendages were segmented and bore densely packed auxiliary spines, which were adapted to suspension feeding in a manner analogous to modern baleen whales. It is assigned to the family Tamisiocarididae, and is measured about 22.8–33.6 cm (0.75–1.10 ft) long.
Mureropodia is an animal that existed in what is now the Valdemiedes Formation of Spain during the early Cambrian period. It was described by José Antonio Gámez Vintaned, Eladio Liñán and Andrey Yu. Zhuravlev in 2011, and the type and only species is M. apae.
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, measuring up to 8 cm (3.1 in) in total body length.
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, with definitive members lasting from the Cambrian to the earliest Ordovician period. The putative Early Devonian member Schinderhannes bartelsi has been considered questionable by some researchers.
Ramskoeldia is a genus of amplectobeluid radiodont described in 2018. It was the second genus of radiodont found to possess gnathobase-like structures and an atypical oral cone after Amplectobelua. The type species, Ramskoeldia platyacantha, was discovered in the Chengjiang biota of China, the home of numerous radiodontids such as Amplectobelua and Lyrarapax.
Houcaris is a possibly paraphyletic radiodont genus, tentatively assigned to either Amplectobeluidae, Anomalocarididae or Tamisiocarididae, known from Cambrian Series 2 of China and the United States. The type species is Houcaris saron which was originally described as a species of the related genus Anomalocaris. Other possible species include H. magnabasis and H. consimilis. The genus Houcaris was established for the two species in 2021 and honors Hou Xianguang, who had discovered and named the type species Anomalocaris saron in 1995 along with his colleagues Jan Bergström and Per E. Ahlberg.
Buccaspinea is an extinct genus of Cambrian hurdiid radiodont from the Marjum Formation, known from frontal appendages and a nearly complete albeit headless specimen with a preserved oral cone. Buccaspinea was described in January 2021, being the second-most recent hurdiid genus to be described.
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