Willwerathia

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Willwerathia
Temporal range: Lower Devonian
20200928 Willwerathia laticeps.png
Reconstruction of Willwerathia laticeps
Scientific classification
Kingdom:
Animalia
Phylum:
Arthropoda
Subphylum:
?Chelicerata
Order:
?Xiphosura
Genus:
†Willwerathia
Størmer, 1969
Species
  • Willwerathia laticeps (Størmer, 1936a)

Willwerathia is a genus of Devonian arthropod. It is sometimes classified as synziphosurine, [1] [2] a paraphyletic group of horseshoe crab-like fossil chelicerate arthropods, [2] while some studies compare its morphology to an artiopod. [3] [4] Willwerathia known only by one species, Willwerathia laticeps, discovered in deposits of the Devonian period from the Klerf Formation, in the Rhenish Slate Mountains of Germany. [1] [5]

Contents

Morphology

Size comparison of Willwerathia (A) and other synziphosurines. 20200929 Synziphosurina Synziphosurine size comparison.png
Size comparison of Willwerathia (A) and other synziphosurines.

As a synziphosurine, Willwerathia is unusually large and so far the largest known synziphosurine, with largest carapace measured about 90mm in width. [1] Prosoma of Willwerathia covered by a vaulted carapace with pointed genal spines, recurved (M-shaped) ophthalmic ridges and pairs of dorsal nodes. [1] Tergites of the opisthosoma are either incomplete or disarticulated in available fossil materials, making it difficult to reveal the original number of opisthosomal segments. [1] The opisthosoma of Willwerathia most likely compose of 10 segments, each expressed by a tergite that bore a median dorsal spine and a pair of tergopleurae (lateral extensions). [1] The opisthosoma subdivided into a wider, most likely 7-segmented preabdomen and a narrower, 3-segmented postabdomen. [1] tergite of the first opisthosomal segment is reduced in length while the remaining segments possess well-developed tergites with lateral nodes and posteriorly curved tergopleurae. The final segment terminated with a short, teardrop-shaped telson. [1]

Paleoecology

Willwerathia was most likely a bottom-dwelling predator. [1] The marked articulation surfaces on each of the preabdominal segments suggest that Willwerathia capable to enroll itself in a way similar to Legrandella . [1] The environment in which Wilwerathia lived in was likely an estuarine to deltaic one, and other animals like the largest eurypterid, Jaekelopterus , are known from the same formation. [6]

Classification

Falcatamacaris Falcatamacaris.svg
Falcatamacaris

Willwerathia was originally thought to be an eurypterid (sea scorpion), with additional fossils described in 1998 reveal its synziphosurine affinities. [1] In the redescription done by Anderson et al. 1998, Willwerathia had been grouped under the synziphosurine family Weinberginidae alongside Weinbergina and Legrandella , [1] a classification which is not supported by phylogenetic analysis. [2] Willwerathia was regarded as part of the monophyletic Xiphosura sensu stricto (true horseshoe crab) by Lamsdell 2013, [2] [7] but further phylogenetic analysis repeatedly resolving it within a clade compose of Bunodids, Pseudoniscids and Dekatriatan (chasmataspidids, eurypterids and arachnids). [8] [9] [10] [11] Morphology of Silurian-Devonian arthropd Maldybulakia is sometimes compared to that of Willwerathia. [4] [12] However, in 2020, Lamsdell found that Willwerathia bears a strong resemblance to the Cambrian artiopod Falcatamacaris , while it does not bear resemblance to other chelicerates. [3]

Related Research Articles

<span class="mw-page-title-main">Chasmataspidida</span> Order of arthropods

Chasmataspidids, sometime referred to as chasmataspids, are a group of extinct chelicerate arthropods that form the order Chasmataspidida. Chasmataspidids are probably related to horseshoe crabs (Xiphosura) and/or sea scorpions (Eurypterida), with more recent studies suggest that they form a clade (Dekatriata) with Eurypterida and Arachnida. Chasmataspidids are known sporadically in the fossil record through to the mid-Devonian, with possible evidence suggesting that they were also present during the late Cambrian. Chasmataspidids are most easily recognised by having an opisthosoma divided into a wide forepart (preabdomen) and a narrow hindpart (postabdomen) each comprising 4 and 9 segments respectively. There is some debate about whether they form a natural group.

<i>Bembicosoma</i> Extinct genus of chelicerate

Bembicosoma is a genus of synziphosurine, a paraphyletic group of fossil chelicerate arthropods. Bembicosoma was regarded as part of the clade Planaterga. Fossils of the single and type species, B. pomphicus, have been discovered in deposits of the Silurian period in the Pentland Hills, Scotland. Bembicosoma had been tentatively assigned as an eurypterid before its synziphosurine affinities revealed.

<i>Bunodes</i> Genus of horseshoe crab relatives

Bunodes is a genus of synziphosurine, a paraphyletic group of fossil chelicerate arthropods. Bunodes was regarded as part of the clade Planaterga. Fossils of the single and type species, B. lunula, have been discovered in deposits of the Silurian period in Ludlow, England. Bunodes is the type genus of the family Bunodidae, the other genera of the same family being Limuloides.

<i>Cyamocephalus</i> Extinct genus of chelicerate

Cyamocephalus is a genus of synziphosurine, a paraphyletic group of fossil chelicerate arthropods. Cyamocephalus was regarded as part of the clade Planaterga. Fossils of the single and type species, C. loganensis, have been discovered in deposits of the Silurian period in Lesmahagow, Scotland. Cyamocephalus is one of the two members of the family Pseudoniscidae, the other being Pseudoniscus. Cyamocephalus differ from Pseudoniscus by the fused tergites of 6th and 7th opisthosomal segments.

<i>Legrandella</i> Extinct genus of chelicerate

Legrandella is a genus of synziphosurine, a paraphyletic group of fossil chelicerate arthropods. Legrandella was regarded as part of the clade Prosomapoda. Fossils of the single and type species, L. lombardii, have been discovered in deposits of the Devonian period in Cochabamba, Bolivia.

<i>Limuloides</i> Genus of horseshoe crab relatives

Limuloides is a genus of synziphosurine, a paraphyletic group of fossil chelicerate arthropods. Limuloides was regarded as part of the clade Planaterga. Fossils of the genus have been discovered in deposits of the Silurian period in the United Kingdom and potentially in the United States. Limuloides is one of the two genera of the family Bunodidae, the other being the type genus Bunodes. Limuloides is characterized by a carapace with radiated ridges and serrated lateral regions, and an opisthosoma with rows of nodes. Limuloides was once though to have lateral compound eyes on its carapace, but later investigation did not find any evidence of it.

<i>Pasternakevia</i> Extinct genus of chelicerate

Pasternakevia is a genus of synziphosurine, a paraphyletic group of fossil chelicerate arthropods. Pasternakevia was regarded as part of the clade Planaterga. Fossils of the single and type species, P. podolica, have been discovered in deposits of the Silurian period in Podolia, Ukraine.

<i>Pseudoniscus</i> Extinct genus of chelicerate

Pseudoniscus is a genus of synziphosurine, a paraphyletic group of fossil chelicerate arthropods. Pseudoniscus was regarded as part of the clade Planaterga. Fossils of the genus have been discovered in deposits of the Silurian period in the United Kingdom, the United States and Estonia. Pseudoniscus is one of the two members of the family Pseudoniscidae, the other being Cyamocephalus.

<i>Weinbergina</i> Extinct genus of chelicerate

Weinbergina is a genus of synziphosurine, a paraphyletic group of fossil chelicerate arthropods. Fossils of the single and type species, W. opitzi, have been discovered in deposits of the Devonian period in the Hunsrück Slate, Germany.

<span class="mw-page-title-main">Synziphosurina</span> Group of arthropods

Synziphosurina is a paraphyletic group of chelicerate arthropods previously thought to be basal horseshoe crabs (Xiphosura). It was later identified as a grade composed of various basal euchelicerates, eventually excluded form the monophyletic Xiphosura sensu stricto and only regarded as horseshoe crabs under a broader sense. Synziphosurines survived at least since early Ordovician to early Carboniferous in ages, with most species are known from the in-between Silurian strata.

<span class="mw-page-title-main">Pseudoniscidae</span> Extinct family of chelicerates

Pseudoniscidae is an extinct family of synziphosurine chelicerates that lived in the Silurian. Pseudoniscidae is classified inside the clade Planaterga, alongside Bunodidae and Dekatriata. Pseudoniscidae is composed by two genera, Cyamocephalus and Pseudoniscus.

<i>Wiedopterus</i> Extinct genus of Devonian eurypterids

Wiedopterus is a genus of eurypterid, an extinct group of aquatic arthropods. The type and only species of Wiedopterus, W. noctua, is known from deposits of Early Devonian age in Germany. The generic name derives from the Wied river, which runs near the site of the initial discovery, and the species name, noctua, derives from Latin noctua (owl) which refers to the superficial resemblance of the carapace to an owl.

<i>Borchgrevinkium</i> Extinct genus of arthropods

Borchgrevinkium is an extinct genus of chelicerate arthropod. A fossil of the single and type species, B. taimyrensis, has been discovered in deposits of the Early Devonian period in the Krasnoyarsk Krai, Siberia, Russia. The name of the genus honors Carsten Borchgrevink, an Anglo-Norwegian explorer who participated in many expeditions to Antarctica. Borchgrevinkium represents a poorly known genus whose affinities are uncertain.

<span class="mw-page-title-main">Metastoma</span>

The metastoma is a ventral single plate located in the opisthosoma of non-arachnid dekatriatan chelicerates such as eurypterids, chasmataspidids and the genus Houia. The metastoma located between the base of 6th prosomal appendage pair and may had functioned as part of the animal's feeding structures. It most likely represented a fused appendage pair originated from somite 7, thus homologous to the chilaria of horseshoe crab and 4th walking leg pair of sea spider. In eurypterids, the plate was typically cordate (heart-shaped) in shape, though differed in shape in some genera, such as Megalograptus.

<span class="mw-page-title-main">Dekatriata</span> Taxonomical clade

Dekatriata is a clade of planatergan chelicerates including the groups Arachnida, Chasmataspidida, Eurypterida and additionally two stem-genera Winneshiekia and Houia. Dekatriata is defined by an opisthosoma with 13 segments as groundplan and fused, plate-like appendages on the first opisthosomal segment.

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

Planaterga is a clade of prosomapod euchelicerates including several synziphosurid genera and the group Dekatriata. Planaterga is defined by the opisthosoma with tergites broadest at third or fourth and lacking enlarged axial nodes, carapace with reduced genal spines, as well as somite VII with reduced appendages and microtergite.

<i>Houia</i> Extinct genus of arthropods

Houia is an extinct genus of dekatriatan, a clade of chelicerate arthropods. Fossils of Houia have been discovered in deposits of the Early Devonian period in Guangxi and Yunnan, both in China. The genus contains two species: H. guangxiensis, from the Pragian to Emsian epoch of Guangxi; and H. yueya, the type species, from the Lochkovian epoch of Yunnan. The name of the genus is derived from the Chinese character 鲎 (hòu), meaning "horseshoe crab".

<i>Venustulus</i> Extinct genus of chelicerate from Wisconsin

Venustulus is a genus of synziphosurine, a paraphyletic group of fossil chelicerate arthropods. Venustulus was regarded as part of the clade Prosomapoda. Fossils of the single and type species, V. waukeshaensis, have been discovered in deposits of the Silurian period in Wisconsin, in the United States. Venustulus is one of the few synziphosurine genera with fossil showing evidence of appendages, the other ones being Weinbergina, Anderella and Camanchia. Despite often being aligned close to horseshoe crabs, it has been found that Venustulus and its relatives form a group made up of various basal euchelicerate arthropods more distant to the xiphosurans.

<i>Camanchia</i> Extinct genus of chelicerate

Camanchia is a genus of synziphosurine, a paraphyletic group of fossil chelicerate arthropods. Camanchia was regarded as part of the clade Prosomapoda. Fossils of the single and type species, C. grovensis, have been discovered in deposits of the Silurian period in Iowa, in the United States. Alongside Venustulus, Camanchia is one of the only Silurian synziphosurine with fossil showing evidence of appendages.

<i>Anderella</i> Extinct genus of chelicerate

Anderella is a genus of synziphosurine, a paraphyletic group of fossil chelicerate arthropods. Anderella was regarded as part of the clade Prosomapoda. Fossils of the single and type species, A. parva, have been discovered in deposits of the Carboniferous period in Montana, in the United States. Anderella is the first and so far the only Carboniferous synziphosurine being described, making it the youngest member of synziphosurines. Anderella is also one of the few synziphosurine genera with fossil showing evidence of appendages, but the details are obscure due to their poor preservation.

References

  1. 1 2 3 4 5 6 7 8 9 10 11 12 Anderson, Lyall I.; Poschmann, Markus; Brauckmann, Carsten (1998). "On the Emsian (Lower Devonian) arthropods of the Rhenish Slate Mountains: 2. The synziphosurine Willwerathia". Paläontologische Zeitschrift. 72 (3–4): 325–336. doi:10.1007/BF02988363. ISSN   0031-0220. S2CID   128464147.
  2. 1 2 3 4 Lamsdell, James C. (2013-01-01). "Revised systematics of Palaeozoic 'horseshoe crabs' and the myth of monophyletic Xiphosura". Zoological Journal of the Linnean Society. 167 (1): 1–27. doi: 10.1111/j.1096-3642.2012.00874.x . ISSN   0024-4082.
  3. 1 2 Lamsdell, James C. (2020-09-01). "A chasmataspidid affinity for the putative xiphosuran Kiaeria Størmer, 1934". PalZ. 94 (3): 449–453. doi:10.1007/s12542-019-00493-8. ISSN   1867-6812.
  4. 1 2 Zong, Ruiwen; Edgecombe, Gregory D.; Liu, Bingcai; Wang, Yi; Yin, Jiayi; Ma, Juan; Xu, Honghe (2023). Cherns, Lesley (ed.). "Silurian freshwater arthropod from northwest China". Papers in Palaeontology. 9 (2): e1488. doi:10.1002/spp2.1488. ISSN   2056-2799.
  5. ↑ Dunlop, J. A.; Penney, D.; Jekel, D. (2020). "A summary list of fossil spiders and their relatives" (PDF). World Spider Catalog. Natural History Museum Bern. pp. 1–296.
  6. ↑ Poschmann, Markus; Tetlie, O. Erik (2006-12-01). "On the Emsian (Lower Devonian) arthropods of the Rhenish Slate Mountains: 5. Rare and poorly known eurypterids from Willwerath, Germany". Paläontologische Zeitschrift. 80 (4): 325–343. doi:10.1007/BF02990208.
  7. ↑ Bicknell, Russell D. C.; Pates, Stephen (2020). "Pictorial Atlas of Fossil and Extant Horseshoe Crabs, With Focus on Xiphosurida". Frontiers in Earth Science. 8: 98. Bibcode:2020FrEaS...8...98B. doi: 10.3389/feart.2020.00098 . ISSN   2296-6463. S2CID   220405124.
  8. ↑ Selden, Paul A.; Lamsdell, James C.; Qi, Liu (2015). "An unusual euchelicerate linking horseshoe crabs and eurypterids, from the Lower Devonian (Lochkovian) of Yunnan, China". Zoologica Scripta. 44 (6): 645–652. doi:10.1111/zsc.12124. ISSN   0300-3256. S2CID   55264483.
  9. ↑ Lamsdell, James C.; Briggs, Derek E. G.; Liu, Huaibao P.; Witzke, Brian J.; McKay, Robert M. (2015). "A new Ordovician arthropod from the Winneshiek Lagerstätte of Iowa (USA) reveals the ground plan of eurypterids and chasmataspidids". The Science of Nature. 102 (9–10): 63. Bibcode:2015SciNa.102...63L. doi:10.1007/s00114-015-1312-5. ISSN   0028-1042. PMID   26391849. S2CID   8153035.
  10. ↑ Lamsdell, James C. (2016). "Horseshoe crab phylogeny and independent colonizations of fresh water: ecological invasion as a driver for morphological innovation". Palaeontology. 59 (2): 181–194. doi: 10.1111/pala.12220 . ISSN   1475-4983. S2CID   85553811.
  11. ↑ Bicknell, Russell D. C.; Lustri, Lorenzo; Brougham, Tom (2019-12-01). "Revision of "Bellinurus" carteri (Chelicerata: Xiphosura) from the Late Devonian of Pennsylvania, USA". Comptes Rendus Palevol. 18 (8): 967–976. doi: 10.1016/j.crpv.2019.08.002 . ISSN   1631-0683.
  12. ↑ Lamsdell, James C. (2013-01-01). "Revised systematics of Palaeozoic 'horseshoe crabs' and the myth of monophyletic Xiphosura". Zoological Journal of the Linnean Society. 167 (1): 1–27. doi: 10.1111/j.1096-3642.2012.00874.x . ISSN   0024-4082. S2CID   82434358.
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