Conulariida

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Conulariida
Temporal range: Ediacaran–Upper Triassic
Conulariid03.jpg
Conulariid from the Mississippian (c. 360 to 325 mya) of Indiana; scale in mm.
Conularia gratiosa (fossil conulariids) (Salem Limestone, Middle Mississippian; Spergen Hill, Indiana, USA) 3.jpg
Two Conularia gratiosa specimens from the Salem Limestone aged to the Middle Mississippian.
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Cnidaria
Class: Staurozoa
Order: Conulatae
Clade: Conulariida
Miller and Gurley, 1896
Genera

See text.

Conulariida are an extinct group of medusozoan cnidarians known from fossils spanning from the latest Ediacaran up until the Late Triassic. [1] [2] [3] They are almost exclusively known from their hard external structures (alternatively referred to as a theca, periderm or test), which were pyramidal in shape and made up of numerous lamellae.

Contents

Structure

The conulariids are fossils preserved as shell-like structures made up of rows of calcium phosphate rods, resembling an ice-cream cone with fourfold symmetry, usually four prominently-grooved corners. [4] New rods were added as the organism grew in length; the rod-based growth falsely gives the fossils a segmented appearance. Exceptional soft-part preservation has revealed that soft tentacles protruded from the wider end of the cone, and a holdfast from the pointed end attached the organisms to hard substrate. The prevailing reconstruction of the organism has it look superficially like a sea anemone sitting inside an angular, hard cone held perpendicular to the substrate. Conulariid shell is composed of francolite with carbonate ion concentration 8.1 wt%. The lattice parameters of conulariid apatite are a = 9.315(7) Å, c = 6.888(3) Å. [5] The fine structure of their shell comprises multiple lamellae of alternately organic-rich and organic-poor layers. [6]

Fossil record

Close-up of a conulariid from the Mississippian of Indiana; scale in mm. Conulariid01.jpg
Close-up of a conulariid from the Mississippian of Indiana; scale in mm.
Conularia milwaukeensis from the Middle Devonian of Wisconsin. Conularia milwaukeensis.jpg
Conularia milwaukeensis from the Middle Devonian of Wisconsin.
A pair of Conularia niagarensis specimens from the Lower Silurian Waukesha Biota site in Wisconsin. UWGM 2723---Conularia niagarensis.jpg
A pair of Conularia niagarensis specimens from the Lower Silurian Waukesha Biota site in Wisconsin.

With the inclusion of the possible Ediacaran conulariid Vendoconularia , which may or may not be a conulariid at all, [7] and the definite late Ediacaran conulariid Paraconularia ediacara , [2] the Conulata fossil record begins with undeniable specimens in the Upper Ediacaran and extends without significant break through numerous major mass extinctions. The Conulariids finally disappear from the fossil record during the Late Triassic, by which time they were very rare, with only 8 documented occurrences across the entire Triassic. Their extinction may have been due to the rise of durophagous organisms as part of the Mesozoic marine revolution. [8]

In North America, conulariids are generally more common in rocks of Ordovician and Carboniferous age.

Lifestyle

Life restoration of a conulariid, showing the soft-bodied anatomy Estonian Museum of Natural History - Conularia.png
Life restoration of a conulariid, showing the soft-bodied anatomy

Condulariids were benthic animals that were sessile and attached to a substrate at the base of the theca, older individuals may have become recumbent (tipped over). [9] They are generally proposed to have been predators, using tentacles to ensnare prey. [10]

Phylogeny

About 20 genera and 150 species are known, [11] but except for local occurrences, Conulariids are relatively uncommon.

The conulariids were originally thought to be anthozoan cnidarians. However, the lack of septa or other features diagnostic of anthozoans led researchers to abandon this hypothesis. Ivantsov and Fedonkin (2002) posit that the conulariids were ancestrally tri-radially symmetrical, as typified with Vendoconularia , typical of the structure seen in Vendozooans. [12] Conulariids are, however, technically a part of the Ediacaran biota as their fossil record starts at latest parts of that period. [2]

It is now also thought that the conulate trilobozoans derived their fourfold symmetry from a sixfold symmetry, as seen in Vendoconularia. This in turn, is thought to be originally derived from an ancestral disk-like trilobozoan three-fold symmetry.[ citation needed ]

Conulariids have generally been thought to be of Cnidarian affinity, occupying a position near the base of the Cnidarian family tree. However, since the 2010s, authors consider conulariids to be members of the subclade Medusozoa, though their exact placement within the clade is uncertain. [3]

Pearls

Conulariids produced pearls within their shells, similar to the way molluscs such as oysters, other pelecypods, and some gastropods do today. These pearls give a clue as to the internal anatomy of the conulariid animal. But due to their calcium phosphate composition, their crystal structure, and their extreme age, these pearls tend to be rather unattractive for use in or as decorative objects. [13]

List of genera

Related Research Articles

<i>Dickinsonia</i> Extinct genus of early animals

Dickinsonia is a genus of extinct organism, most likely an animal, that lived during the late Ediacaran period in what is now Australia, China, Russia and Ukraine. It is one of the best known members of the Ediacaran biota. The individual Dickinsonia typically resembles a bilaterally symmetrical ribbed oval. Its affinities are presently unknown; its mode of growth has been considered consistent with a stem-group bilaterian affinity, though various other affinities have been proposed. The discovery of cholesterol molecules in fossils of Dickinsonia lends support to the idea that Dickinsonia was an animal, though these results have been questioned.

<i>Ausia fenestrata</i> Genus of marine filter feeders

Ausia fenestrata is a curious Ediacaran period fossil represented by only one specimen 5 cm long from the Nama Group, a Vendian to Cambrian group of stratigraphic sequences deposited in the Nama foreland basin in central and southern Namibia. It has similarity to Burykhia from Ediacaran (Vendian) siliciclastic sediments exposed on the Syuzma River of Arkhangelsk Oblast, northwest Russia. This fossil is of the form of an elongate bag-like sandstone cast tapering to a cone on one end. The surface of the fossil is covered with oval depressions ("windows") regularly spaced over the surface in the manner of concentric/parallel rows. The taxonomic identity of Ausia is unresolved.

<span class="mw-page-title-main">Trace fossil</span> Geological record of biological activity

A trace fossil, also known as an ichnofossil, is a fossil record of biological activity by lifeforms but not the preserved remains of the organism itself. Trace fossils contrast with body fossils, which are the fossilized remains of parts of organisms' bodies, usually altered by later chemical activity or mineralization. The study of such trace fossils is ichnology and is the work of ichnologists.

<i>Kimberella</i> Primitive Mollusc-like organism

Kimberella is an extinct genus of bilaterian known only from rocks of the Ediacaran period. The slug-like organism fed by scratching the microbial surface on which it dwelt in a manner similar to the gastropods, although its affinity with this group is contentious.

<i>Tribrachidium</i> Extinct genus of invertebrates

Tribrachidium heraldicum is a tri-radially symmetric fossil animal that lived in the late Ediacaran (Vendian) seas. In life, it was hemispherical in form. T. heraldicum is the best known member of the extinct group Trilobozoa.

<span class="mw-page-title-main">Vendobionta</span> Group of extinct creatures that were part of the Ediacaran biota

Vendobionts or Vendozoans (Vendobionta) are a proposed very high-level, extinct clade of benthic organisms that made up of the majority of the organisms that were part of the Ediacaran biota. It is a hypothetical group and at the same time, it would be the oldest of the animals that populated the Earth about 580 million years ago, in the Ediacaran period. They became extinct shortly after the so-called Cambrian explosion, with the introduction of fauna formed by more recognizable groups and more related to modern animals. It is very likely that the whole Ediacaran biota is not a monophyletic clade and not every genus placed in its subtaxa is an animal.

<i>Yorgia</i> Extinct proarticulate of Russia

Yorgia waggoneri is a discoid Ediacaran organism. It has a low, segmented body consisting of a short wide "head", no appendages, and a long body region, reaching a maximum length of 25 cm (9.8 in). It is classified within the extinct animal phylum Proarticulata.

<span class="mw-page-title-main">Trilobozoa</span> Extinct phylum of triradially symmetrical animals

Trilobozoa is a phylum of extinct, sessile animals that were originally classified into the Cnidaria. The basic body plan of trilobozoans is often a tri-radial or radial sphere-shaped form with lobes radiating from its centre. Fossils of trilobozoans are restricted to marine strata of the Late Ediacaran period.

<i>Ovatoscutum</i> Extinct species of enigmatic organism

Ovatoscutum concentricum is one of many enigmatic organisms known from the Ediacaran deposits of the Flinders Ranges, Australia, and the White Sea area in Russia, dating around 555 Ma.

<i>Albumares</i> Extinct genus of soft-bodied Trilobozoan

Albumares brunsae is a tri-radially symmetrical fossil animal that lived in the late Ediacaran seafloor. It is a member of the extinct group Trilobozoa.

Anfesta stankovskii is a tri-radially symmetrical fossil animal that lived in the late Ediacaran (Vendian) seafloor. It is a member of the extinct group Trilobozoa.

<i>Rugoconites</i> Extinct genus of invertebrates

Rugoconites is a genus of Ediacaran biota found as fossils in the form of a circular or oval-like impression preserved in high relief, six or more centimeters in diameter. The fossils are surrounded by frills that have been interpreted as sets of tentacles. The bifurcating radial ribs, spreading from a central dome, serve to distinguish this genus from the sponge Palaeophragmodictya, and may represent the channels of the gastrovascular system. Fossils of Rugoconites have been interpreted as early sponges, although this is countered by Sepkoski et al. (2002), who interpreted the organism as a free-swimming jellyfish-like cnidarian; similar to Ovatoscutum. However, the fossil is consistently preserved as a neat circular form and its general morphology does not vary, therefore a benthic and perhaps slow-moving or sessile lifestyle is more likely. Ivantstov & Fedonkin (2002), suggest that Rugoconites may possess tri-radial symmetry and be a member of the Trilobozoa.

<span class="mw-page-title-main">Vendiamorpha</span> Extinct class of simple animals

Vendiamorpha is a class of extinct animals within the Ediacaran phylum Proarticulata.

Vendoconularia is a genus of Ediacaran organism consisting of a hexagonal cone, which is thought to have housed a tentaculate organism. Three longitudinal bands are interspersed between the six sides of the cone. The discovery of vendoconulariids in Proterozoic strata of Russia confirmed a 1987 prediction that conulariids constituted part of Ediacaran biota.

<i>Sphenothallus</i> Extinct genus of aquatic animals

Sphenothallus is a problematic extinct genus lately attributed to the conulariids. It was widespread in shallow marine environments during the Paleozoic.

<i>Ventogyrus</i> Extinct genus of invertebrates

Ventogyrus is an Ediacaran fossil found in the White Sea-Arkhangelsk region of Russia. It was first discovered in the Teska member of the Ust'-Pinega formation, in a thick lens of sandstone, originally sand dumped by storm waves that cut a deep channel through the shallow sea bottom where the organisms lived. Many individuals were preserved on top of each other, often torn or in distorted positions. As a result, it was originally thought to have had a "boat shaped" form and to have lived anchored in the sea floor. However, a nearby site discovered later by Mikhail Fedonkin yielded separate specimens which were beautifully preserved in an upright position and showed the internal anatomy.

<i>Archaeaspinus fedonkini</i>

Archaeaspinus fedonkini is an extinct proarticulatan organism from the Late Precambrian (Ediacaran) period.

<span class="mw-page-title-main">Ichnusa (genus)</span> Discoidal-pyramidal shaped Cnidarian

Ichnusa is a genus of discoidal cnidarians that existed during the Ediacaran, 635-541 Million Years ago (MYA) discovered on the island of Sardinia, Italy. The genus is monotypic, only containing the species Ichnusa cocozzi. Palaeontologists think that Ichnusa represented a cnidarian of unknown affinities, with I. cocozzi being put in the Scyphozoa.

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

A "Palaeopascichnid" describes a multitude of elongate fossils made up of multiple sausage-shaped chambers. They appear only in Ediacaran sediments. Fossils of Palaeopascichnids consist of an occasionally branching series of globular or elongate chambers. These fossils started appearing in the Vendian about 580 million years ago. Fossils of Palaeopascichnids are found in East European platform, Siberia, South China (Lantian), Australia, India (Tethys), Avalonia

Staurinidia is a genus of Ediacaran soft-bodied organism from the deposits of the Ust'-Pinega formation. It is a monotypic genus, containing only the single species Staurinidia crucicula. The genus was first described in 1985 by Russian palaeontologist Mikhail A. Fedonkin. S. crucicula's four-fold symmetry is present as a result of four canals radiating from the middle of a small cavity in the middle of the body. Other forms with four way symmetry, mainly Medusoid forms, from the Ediacaran comprise an essential chunk of the Ediacaran diversity of symmetry; their organisations are similar to, though smaller than, those of a modern-day Scyphozoan Cnidarian.

References

  1. Ben M. Waggoner; David Smith (1994). "Study of conulariid and related phosphatic conical exoskeletons from the Prague Basin (Czech Republic)". In G. L. Albanesi; M. S. Beresi; S. H. Peralta (eds.). Ordovician from the Andes. Serie Correlación Geológica Nº 17. INSTITUTO SUPERIOR DE CORRELACIÓN GEOLÓGICA.
  2. 1 2 3 Leme, J. M.; Van Iten, H.; Simões, M. G. (2022). "A New Conulariid (Cnidaria, Scyphozoa) From the Terminal Ediacaran of Brazil". Frontiers in Earth Science. 10: Article 777746. Bibcode:2022FrEaS..10.7746L. doi: 10.3389/feart.2022.777746 .
  3. 1 2 Van Iten, Heyo; Hughes, Nigel C.; John, Douglas L.; Gaines, Robert R.; Colbert, Matthew W. (2023-04-27). "Conulariid soft parts replicated in silica from the Scotch Grove Formation (lower Middle Silurian) of east-central Iowa". Journal of Paleontology: 1–10. doi: 10.1017/jpa.2023.6 . ISSN   0022-3360. S2CID   258389436.
  4. Waggoner, B.M. & D. Smith (1994): The Conulariida, Mystery fossils. University of California Museum of Paleontology web page
  5. Vinn, O.; Kirsimäe, K. (2015). "Alleged cnidarian Sphenothallus in the Late Ordovician of Baltica, its mineral composition and microstructure". Acta Palaeontologica Polonica. 60: 1001–1008. doi: 10.4202/app.00049.2013 .
  6. Ford, Robert C.; Van Iten, Heyo; Clark, George R. (2016). "Microstructure and composition of the periderm of conulariids". Journal of Paleontology. 90 (3): 389. doi:10.1017/jpa.2016.63. S2CID   133541791.
  7. Van Iten, H.; De Moraes Leme, J.; Coelho Rodrigues, S.; Guimaraes Simoes, M. (2005). "Reinterpretation of a Conulariid-Like Fossil from the Vendian of Russia". Palaeontology. 48 (3): 619–622. doi:10.1111/j.1475-4983.2005.00471.x. hdl: 11449/31655 . S2CID   247733826.
  8. Lucas, Spencer G. (2012-03-22). "The Extinction of the Conulariids". Geosciences. 2 (1): 1–10. doi: 10.3390/geosciences2010001 . ISSN   2076-3263.
  9. Iten, Heyo Van; Vyhlasová, Zdenka (2004-12-31), Webby, Barry D.; Paris, Florentin; Droser, Mary L.; Percival, Ian G. (eds.), "14. Conulariids", The Great Ordovician Biodiversification Event, Columbia University Press, pp. 119–123, doi:10.7312/webb12678-015, ISBN   978-0-231-12678-6 , retrieved 2023-06-25
  10. Leme, Juliana M.; Van Iten, Heyo; Simões, Marcello G. (2022-06-08). "A New Conulariid (Cnidaria, Scyphozoa) From the Terminal Ediacaran of Brazil". Frontiers in Earth Science. 10. Bibcode:2022FrEaS..10.7746L. doi: 10.3389/feart.2022.777746 . ISSN   2296-6463.
  11. "ZooBank: The World Register of Animal Names". www.zoobank.org. Archived from the original on 27 September 2007. Retrieved 14 January 2022.
  12. Ivantsov, A. Y.; Fedonkin, M. A. (2002). "Conulariid-like fossil from the Vendian of Russia: a metazoan clade across the Proterozoic/Palaeozoic boundary". Palaeontology. 45 (6): 1119–1129. doi: 10.1111/1475-4983.00283 .
  13. Boucot, A.J. (2013). Evolutionary Paleobiology of Behavior and Coevolution. Elsevier. pp. 750 (page 69). ISBN   9781483290812.

Bibliography