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{{Short description|Extinct genus of marine invertebrates}} |
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{{Taxobox |
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| fossil_range = {{Fossil range|Lower Cambrian|Lower Cambrian|[[Early Cambrian]]|ref=<ref name="dk">{{cite book | title=Prehistoric Life: The Definitive Visual History of Life on Earth | publisher=[[Dorling Kindersley]] | year=2009 | location=New York | isbn=978-0-7566-5573-0 | last=Douglas | first=Palmer | page=72 | edition=1st American|display-authors=etal}}</ref>}} |
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| fossil_range = {{Fossil range|prefix = ~ | 516 | PS = (Cambrian Stage 3) | ref=<ref name="Zamora2013"/>}} |
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| image = Helicoplacus.jpg |
| image = Helicoplacus USNM.jpg |
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| image_caption = ''Helicoplacus guthi''<ref name="Type1963">{{cite journal |last= Durham, J.W. |first= & Caster, K. E. |title= Helicoplacoidea: A New Class of Echinoderms |journal= Science |volume= 140 |issue= 3568 |pages= 820–822 |date= 17 May 1963 |pmid=17746435 |last2= Caster |first2= KE |doi= 10.1126/science.140.3568.820}}</ref> |
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| image_caption = ''H. gilberti'' [[hypotype]] (USNM 6063), [[National Museum of Natural History]] |
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| regnum = [[Animal]]ia |
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| phylum = [[Echinodermata]] |
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* ''Helicoplacus guthi'' |
* ''Helicoplacus guthi'' |
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|range_map=Helicoplacus finds.svg |
| range_map = Helicoplacus finds.svg |
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|range_map_caption={{legend|blue|Areas where ''Helicoplacus'' has been found<ref name=" |
| range_map_caption = {{legend|blue|Areas where ''Helicoplacus'' has been found<ref name="Smith2013nc" />}} |
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|range_map_alt=The contiguous United States are shaded in blue on this map of northern North America |
| range_map_alt = The contiguous United States are shaded in blue on this map of northern North America |
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'''''Helicoplacus''''' (often misspelled '''''Helioplacus''''') is the earliest well-studied [[fossil]] [[echinodermata|echinoderm]]. Fossil plates are known from several regions. Complete specimens were found in Lower [[Cambrian]] [[Stratum|strata]] of the White Mountains of [[California]]. |
'''''Helicoplacus''''' (often misspelled '''''Helioplacus''''') is the earliest well-studied [[fossil]] [[echinodermata|echinoderm]]. Fossil plates are known from several regions. Complete specimens were found in Lower [[Cambrian]] [[Stratum|strata]] of the White Mountains of [[California]]. |
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The animal was a cigar-shaped creature up to {{convert|7|cm|in}} long that stood upright on one end. Unlike more typical echinoderms such as [[sea star]]s, ''Helicoplacus'' does not have fivefold symmetry. Instead, there is a spiral food groove on the outside along which food was moved to a mouth that is thought to be on the side. The respiratory system appears to be primitive. Although the animal does not look like a typical echinoderm, the plates are composed of the characteristic calcareous plates known as ''[[stereom]]'' that are common to all echinoderms. The ambulacrum is similar to that of the [[Edrioasteroidea]]; as a result, |
The animal was a cigar-shaped creature up to {{convert|7|cm|in}} long that stood upright on one end. Unlike more typical echinoderms such as [[sea star]]s, ''Helicoplacus'' does not have fivefold symmetry. Instead, there is a spiral food groove on the outside along which food was moved to a mouth that is thought to be on the side. The respiratory system appears to be primitive. Although the animal does not look like a typical echinoderm, the plates are composed of the characteristic calcareous plates known as ''[[stereom]]'' that are common to all echinoderms. The ambulacrum is similar to that of the [[Edrioasteroidea]]; as a result, ''Helicoplacus'' may belong to [[Pelmatozoa]]. |
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Other contemporaneous echinoderms are known to have existed from their dissociated plates, but other than a few possible edrioasteroids, ''Helicoplacus'' is the earliest echinoderm that is well enough preserved to analyze its characteristics. One much earlier form called ''[[Arkarua]]'' has been hypothesized to be an [[stem group|ancestral]] echinoderm because of its fivefold symmetry |
Other contemporaneous echinoderms are known to have existed from their dissociated plates, but other than a few possible edrioasteroids, ''Helicoplacus'' is the earliest echinoderm that is well enough preserved to analyze its characteristics. One much earlier form called ''[[Arkarua]]'' has been hypothesized to be an [[stem group|ancestral]] echinoderm because of its fivefold symmetry, though it appears to lack stereoms and a mouth. |
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Helicoplacoids seem to have existed for about 15 million years{{Citation needed|date=June 2007}} in the Lower Cambrian, around {{mya|525}}.{{Citation needed|date=June 2007}} |
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{{Early Echinoderms graphical timeline}} |
{{Early Echinoderms graphical timeline}} |
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'' |
''Helicoplacus'' is thought to have been a suspension feeder living at moderate depths in highly oxygenated water with strong enough currents to ensure a steady food supply. It is typically found in greenish [[shale]]s and, rarely found in shallow water [[sandstone]]s and [[limestone]]s. The helically spiraling rows of plates radiating from the base, which in life probably was anchored in the muddy substrate.<ref>{{cite web| url = http://www.usna.edu/Users/oceano/pguth/website/pl00001.htm| url-status = dead| archive-url = https://web.archive.org/web/19990203180851/http://www.usna.edu/Users/oceano/pguth/website/pl00001.htm| archive-date = 1999-02-03| title = Associate Professor Peter L. Guth Home Page}}</ref> |
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== Stratigraphic distribution == |
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''Helicoplacus'' is one of the earliest mineralizing echinoderms, appearing alongside close relatives ''Polyplacus'' and ''Waucobella'' in the [[Poleta formation]], among strata notable for an exceptional abundance of echinoderm fossils (including also edrioasteroid fragments).<ref name="Smith2013nc">{{Cite journal | title = Figure 3: Stratigraphic distribution of early to middle Cambrian echinoderms. | journal = Nature Communications | date = 2013 | doi = 10.1038/ncomms2391| pmid = 23340425 | doi-access = free | last1 = Smith | first1 = A. B. | last2 = Zamora | first2 = S. | last3 = Álvaro | first3 = J. J. | volume = 4 | page = 1385 }}</ref><ref name="Zamora2013">Zamora, S. ''et al.'' (2013). Cambrian echinoderm diversity and palaeobiogeography. In: Harper, D. A. T. & Servais, T. (eds). ''Early Palaeozoic Biogeography and Palaeogeography''. Geological Society, London, Memoirs, '''38''': 157-173.</ref> |
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The Poleta Formation is correlated with the as-yet unratified Cambrian Stage 3 (Series 2), giving it a provisional date of ~{{Ma|516}}.<ref>{{Cite book | |
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chapter = Chapter 19 – The Cambrian Period | |
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title = Geologic Time Scale 2020| |
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author = Peng, S.C. | author2 = Babcock, L.E. | author3 = Ahlberg, P.| |
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year = 2020| |
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pages = 565–629| |
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publisher = Elsevier |
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| doi = 10.1016/B978-0-12-824360-2.00019-X| |
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s2cid = 242177216}} |
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</ref> |
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{{reflist}} |
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==See also== |
==See also== |
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* ''[[Helicocystis]]'' |
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*[[List of prehistoric echinoderms]] |
*[[List of prehistoric echinoderms]] |
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*[[List of echinodermata orders]] |
*[[List of echinodermata orders]] |
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{{Reflist}} |
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== External links == |
== External links == |
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* Pictures of 'Helicoplacus' can be found at http://www.usna.edu/Users/oceano/pguth/website/pl00001.htm |
* Pictures of 'Helicoplacus' can be found at http://www.usna.edu/Users/oceano/pguth/website/pl00001.htm |
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{{Taxonbar|from=Q143851}} |
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[[Category:Prehistoric Echinozoa genera]] |
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[[Category:Cambrian echinoderms]] |
[[Category:Cambrian echinoderms]] |
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[[Category: |
[[Category:Paleozoic echinoderms of North America]] |
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[[Category:Cambrian genus extinctions]] |
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{{paleo-echinoderm-stub}} |
{{paleo-echinoderm-stub}} |
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Latest revision as of 00:29, 4 September 2024
| Helicoplacus Temporal range:
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| H. gilberti hypotype (USNM 6063), National Museum of Natural History | |
Scientific classification 
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Echinodermata |
| Class: | †Helicoplacoidea |
| Genus: | †Helicoplacus |
| Species | |
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Areas where Helicoplacus has been found[2]
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Helicoplacus (often misspelled Helioplacus) is the earliest well-studied fossil echinoderm. Fossil plates are known from several regions. Complete specimens were found in Lower Cambrian strata of the White Mountains of California.
The animal was a cigar-shaped creature up to 7 centimetres (2.8 in) long that stood upright on one end. Unlike more typical echinoderms such as sea stars, Helicoplacus does not have fivefold symmetry. Instead, there is a spiral food groove on the outside along which food was moved to a mouth that is thought to be on the side. The respiratory system appears to be primitive. Although the animal does not look like a typical echinoderm, the plates are composed of the characteristic calcareous plates known as stereom that are common to all echinoderms. The ambulacrum is similar to that of the Edrioasteroidea; as a result, Helicoplacus may belong to Pelmatozoa.
Other contemporaneous echinoderms are known to have existed from their dissociated plates, but other than a few possible edrioasteroids, Helicoplacus is the earliest echinoderm that is well enough preserved to analyze its characteristics. One much earlier form called Arkarua has been hypothesized to be an ancestral echinoderm because of its fivefold symmetry, though it appears to lack stereoms and a mouth.
Early Echinoderms (?) | ||||||
−570 — – −565 — – −560 — – −555 — – −550 — – −545 — – −540 — – −535 — – −530 — – −525 — – −520 — – −515 — – −510 — – −505 — – −500 — – −495 — – | Ter Se. 2 Miao Fur | |||||
Axis scale: millions of years ago. | ||||||
Helicoplacus is thought to have been a suspension feeder living at moderate depths in highly oxygenated water with strong enough currents to ensure a steady food supply. It is typically found in greenish shales and, rarely found in shallow water sandstones and limestones. The helically spiraling rows of plates radiating from the base, which in life probably was anchored in the muddy substrate.[3]
Stratigraphic distribution
[edit]Helicoplacus is one of the earliest mineralizing echinoderms, appearing alongside close relatives Polyplacus and Waucobella in the Poleta formation, among strata notable for an exceptional abundance of echinoderm fossils (including also edrioasteroid fragments).[2][1]
The Poleta Formation is correlated with the as-yet unratified Cambrian Stage 3 (Series 2), giving it a provisional date of ~516 million years ago.[4]
See also
[edit]References
[edit]- ^ a b Zamora, S. et al. (2013). Cambrian echinoderm diversity and palaeobiogeography. In: Harper, D. A. T. & Servais, T. (eds). Early Palaeozoic Biogeography and Palaeogeography. Geological Society, London, Memoirs, 38: 157-173.
- ^ a b Smith, A. B.; Zamora, S.; Álvaro, J. J. (2013). "Figure 3: Stratigraphic distribution of early to middle Cambrian echinoderms". Nature Communications. 4: 1385. doi:10.1038/ncomms2391. PMID 23340425.
- ^ "Associate Professor Peter L. Guth Home Page". Archived from the original on 1999-02-03.
- ^ Peng, S.C.; Babcock, L.E.; Ahlberg, P. (2020). "Chapter 19 – The Cambrian Period". Geologic Time Scale 2020. Elsevier. pp. 565–629. doi:10.1016/B978-0-12-824360-2.00019-X. S2CID 242177216.
External links
[edit]- Pictures of 'Helicoplacus' can be found at http://www.usna.edu/Users/oceano/pguth/website/pl00001.htm
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