Hurdiidae

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Hurdiidae
Temporal range: Cambrian Stage 4–Lower Devonian
20220724 Hurdiidae.png
Stanleycaris (top left), Hurdia (top right), Aegirocassis (middle), Peytoia (bottom left), Cambroraster (bottom right)
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Class:† Dinocaridida
Order:† Radiodonta
Family:† Hurdiidae
Vinther et al., 2014
Genera

See text

Hurdiidae (synonymous with the previously named Peytoiidae [1] ) 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.

Contents

Description

Hurdiidae is characterized by frontal appendages with distal region composed of 5 subequal blade-like endites, alongside the enlarged head carapaces and tetraradial mouthpart (oral cone). [2]

The frontal appendages of hurdiids have a distinctive morphology, with the appendage of most species bearing five equally-sized elongate blade-like ventral spines known as endites. [3] Subsequent podomeres were reduced in size and with only small endites or none. Each podomere bore only a single endite, unlike other radiodonts, in which the endites were paired. [3] In most species, the endites were curved medially, so that the appendages formed a basket-like structure. [2] Some hurdiids had greater numbers of endites, with Cordaticaris bearing seven endites of equal length. [4] Ursulinacaris is unique among hurdiids in bearing paired endites, which is likely a transitional form between the appendage of other radiodonts and that of hurdiids. [3]

Hurdiids exhibited a wide range of body size. The smallest known hurdiid specimen, of an unnamed species, is estimated to have had a body length of 6–15 millimetres (0.24–0.59 in), but it is not known whether this specimen was juvenile or adult. [5] Aegirocassis , the largest known hurdiid, was over 2 metres (6.6 ft) long, comparable in size to the largest known arthropods. [6]

Paleobiology

The majority of hurdiids appear to have been predators that fed by sifting sediment with their frontal appendages, but some members, like Aegirocassis , Pseudoangustidontus , and possibly Cambroraster were suspension feeders. [2] [7] [8]

Distribution

Hurdiids had a global distribution. [4] The earliest known hurdiid in the fossil record is Peytoia infercambriensis , which lived during the third age of the Cambrian in what is now the country of Poland. [9] The group increased in diversity during the Miaolingian epoch. [4] Post-Cambrian records of the group are rare, but the group lasted into the Devonian period, with the last known taxon being the Emsian Schinderhannes bartelsi from what is now Germany. [9] [5]

Classification

Hurdiidae is classified within Radiodonta, a clade of stem-group arthropods. Hurdiidae is defined phylogenetically as the most inclusive clade containing Hurdia victoria but not Amplectobelua symbrachiata , Anomalocaris canadensis , or Tamisiocaris borealis . [10] Some authors have argued that Peytoiidae, which was named by Conway Morris and Robison, 1982, has priority over Hurdiidae, and that Hurdiidae has "yet to be properly established following ICZN standards". [1]

The phylogeny of hurdiids, accompanying the description of the hurdiids Aegirocassis benmoulae , Titanokorys gainesii, and the analyzation of Stanleycaris hirpex as follows: [6]

Radiodonta
Phylogenetic position of hurdiid radiodonts after Moysiuk & Caron 2022. [11]

Species include

Tauricornicaris was previously considered as a member of hurdiid, but later reinterpreted as euarthropod tergites. [14] [15]

Zhenghecaris is originally described as a thylacocephalan, but it is later considered as hurdiid dorsal carapace. [16] [17] However, placement is questioned by some researchers, because classification as radiodont is majorly based on characters of Tauricornicaris. [12]

Schinderhannes was originally described as stem-arthropod which have both characters of euarthropods and radiodonts, this interpretation was denied and most researchers agree that is hurdiid radiodont. [18] [19] [20] [21] [17] [22] [23] [24] [25] There are some researchers question its classification as hurdiid. [26] [27]

Huangshandongia yichangensis , Liantuoia inflata [28] and Proboscicaris hospes [29] may represent species of Hurdia. [30] [31]

Related Research Articles

<span class="mw-page-title-main">Dinocaridida</span> Extinct class of basal arthropods

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.

<i>Anomalocaris</i> Extinct genus of cambrian radiodont

Anomalocaris is an extinct genus of radiodont, an order of early-diverging stem-group arthropods.

<i>Peytoia</i> Extinct genus of radiodont

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.

<span class="mw-page-title-main">Anomalocarididae</span> Clade of extinct arthropods

Anomalocarididae is an extinct family of Cambrian radiodonts, a group of stem-group arthropods.

<i>Schinderhannes bartelsi</i> Extinct species of radiodont

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.

<span class="mw-page-title-main">Radiodonta</span> Extinct order of basal arthropods

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.

<i>Hurdia</i> Extinct genus of radiodonts

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.

<i>Stanleycaris</i> Extinct genus of basal hurdiid radiodonts

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.

<i>Caryosyntrips</i> Extinct genus of arthropod

Caryosyntrips ("nutcracker") is an extinct genus of stem-arthropod which known from Canada, United States and Spain during the middle Cambrian.

<span class="mw-page-title-main">Amplectobeluidae</span> Extinct clade of Cambrian organisms

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.

<i>Aegirocassis</i> Extinct genus of radiodonts

Aegirocassis is an extinct genus of giant radiodont arthropod belonging to the family Hurdiidae that lived 480 million years ago during the early Ordovician in the Fezouata Formation of Morocco. It is known by a single species, Aegirocassis benmoulai. Van Roy initiated scientific study of the fossil, the earliest known of a "giant" filter-feeder discovered to date. Aegirocassis is considered to have evolved from early predatory radiodonts. This animal is characterized by its long, forward facing head sclerite, and the endites on its frontal appendages that bore copious amounts of baleen-like auxiliary spines. This animal evolving filter-feeding traits was most likely a result of the Great Ordovician Biodiversification Event, when environmental changes caused a diversification of plankton, which in turn allowed for the evolution of new suspension feeding lifeforms. Alongside the closely related Pseudoangustidontus, an unnamed hurdiid from Wales, the middle Ordovician dinocaridid Mieridduryn, and the Devonian hurdiid Schinderhannes this radiodont is one of the few dinocaridids known from post-Cambrian rocks.

<i>Ramskoeldia</i> Extinct genus of Amplectobeluid radiodont

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.

<i>Ursulinacaris</i> Extinct genus of hurdiid radiodonts

Ursulinacaris is a genus of hurdiid radiodont from the Cambrian of North America. It contains one known species, Ursulinacaris grallae. It was described in 2019, based on fossils of the frontal appendages discovered in the 1990s and thereafter. The endites of Ursulinacaris were very slender, unlike other hurdiids such as Peytoia or Hurdia. It was initially reported as the first hurdiid with paired endites, but Moysiuk & Caron (2021) suggested that it is actually the preservation of the fossils and thus no paired endites.

<i>Houcaris</i> Genus of radiodonts

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.

<i>Titanokorys</i> Extinct genus of giant hurdiid radiodont

Titanokorys is a genus of extinct hurdiid (peytoiid) radiodont that existed during the mid Cambrian. It is the largest member of its family from the Cambrian, with a body length of 50 cm (20 in) long, making it one of the largest animals of the time. It bears a resemblance to the related genus Cambroraster. Fossils of T. gainesi were first found within Marble Canyon in 2018. The fossils were not named until 2021 because they were assumed to be giant specimens of Cambroraster.

<i>Laminacaris</i> Genus of extinct arthropods

Laminacaris is a genus of extinct stem-group arthropods (Radiodonta) that lived during the Cambrian period. It is monotypic with a single species Laminacaris chimera, the fossil of which was described from the Chengjiang biota of China in 2018. Around the same time, two specimens that were similar or of the same species were discovered at the Kinzers Formation in Pennsylvania, USA. The first specimens from China were three frontal appendages, without the other body parts.

<i>Pahvantia</i> Extinct genus of radiodonts

Pahvantia is an extinct genus of hurdiid radiodont from the Cambrian. It is known by a single species, Pahvantia hastata, described from Wheeler Shale and Marjum Formation in Utah. Although it was once considered as filter feeder using large number of putative setae, this structures are later considered as misidentification of trunk materials.

<i>Cordaticaris</i> Genus of extinct stem-group arthropods

Cordaticaris is a genus of extinct hurdiid (peytoiid) radiodont that lived in what is now northern China during the middle Cambrian period. This animal was described in 2020 based on remains found in the Zhangxia Formation, located in the Shandong Province. It is differentiated from other members of its family by its unique heart-shaped frontal sclerite, and its frontal appendages bearing nine endites and seven more elongated subequal endites. This animal was important as it was the first Miaolingian aged hurdiid known from rock layers outside of laurentia, allowing paleontologists to get a better grasp of this families geographic range in life.

<i>Buccaspinea</i> Extinct genus of radiodont

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.

<i>Zhenghecaris</i> Genus of enigmatic Cambrian arthropod

Zhenghecaris shankouensis is an enigmatic arthropod from the Lower Cambrian Maotianshan Shales, either classified as a hurdiid or thylacocephalan. It is known from several specimens mostly preserving the carapace and eyes measuring roughly 15 cm (5.9 in), which mark it as one of the largest thylacocephalans, behind Ostenocaris, Dollocaris and Ainiktozoon, as well as the earliest since all other thylacocephalans are Ordovician or younger. Since no appendages have been preserved, the fossil may not be a thylacocephalan, with a hurdiid affinity being suggested instead, due to its resemblance to the H-element of genera such as Cambroraster. It has also been suggested to be within Arthropoda incertae sedis, as the fragmentary remains cannot confidently be classified further.

References

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  15. ↑ Cong, Pei-Yun; Edgecombe, Gregory D.; Daley, Allison C.; Guo, Jin; Pates, Stephen; Hou, Xian-Guang (2018). Zhang, Xi-Guang (ed.). "New radiodonts with gnathobase-like structures from the Cambrian Chengjiang biota and implications for the systematics of Radiodonta". Papers in Palaeontology. 4 (4): 605–621. Bibcode:2018PPal....4..605C. doi:10.1002/spp2.1219. ISSN   2056-2799.
  16. ↑ Pates, Stephen; Daley, Allison C.; Butterfield, Nicholas J. (2019-06-11). "First report of paired ventral endites in a hurdiid radiodont". Zoological Letters. 5 (1): 18. doi: 10.1186/s40851-019-0132-4 . ISSN   2056-306X. PMC   6560863 . PMID   31210962.
  17. 1 2 Moysiuk, J.; Caron, J.-B. (2019-08-14). "A new hurdiid radiodont from the Burgess Shale evinces the exploitation of Cambrian infaunal food sources". Proceedings of the Royal Society B: Biological Sciences. 286 (1908): 20191079. doi:10.1098/rspb.2019.1079. ISSN   0962-8452. PMC   6710600 . PMID   31362637.
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  24. ↑ Moysiuk, Joseph; Caron, Jean-Bernard (2022). "A three-eyed radiodont with fossilized neuroanatomy informs the origin of the arthropod head and segmentation". Current Biology. 32 (15): 3302–3316.e2. Bibcode:2022CBio...32E3302M. doi:10.1016/j.cub.2022.06.027. ISSN   0960-9822. PMID   35809569.
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  29. ↑ Chlupač, Ivo; Kordule, Vratislav (2002). "Arthropods of Burgess Shale type from the Middle Cambrian of Bohemia (Czech Republic)". Bulletin of the Czech Geological Survey. 77 (3): 167–182.
  30. ↑ Daley, Allison C.; Budd, Graham E.; Caron, Jean-Bernard (2013). "Morphology and systematics of the anomalocaridid arthropod Hurdia from the Middle Cambrian of British Columbia and Utah". Journal of Systematic Palaeontology. 11 (7): 743–787. Bibcode:2013JSPal..11..743D. doi:10.1080/14772019.2012.732723. ISSN   1477-2019.
  31. ↑ Sun, Zhixin; Zeng, Han; Zhao, Fangchen (2020). "A new middle Cambrian radiodont from North China: Implications for morphological disparity and spatial distribution of hurdiids". Palaeogeography, Palaeoclimatology, Palaeoecology. 558: 109947. Bibcode:2020PPP...55809947S. doi:10.1016/j.palaeo.2020.109947. ISSN   0031-0182.
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