Spriggina

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Spriggina
Temporal range: Late Ediacaran, 555  Ma
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Spriggina Floundensi 4.png
Fossil of S. floundersi. Scale in millimetres
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum:† Proarticulata
Class:† Cephalozoa
Family:† Sprigginidae
Genus:† Spriggina
Glaessner, 1958 [1]
Species:
†S. floundersi
Binomial name
†Spriggina floundersi
Glaessner, 1958

Spriggina is a genus of early animals whose relationship to living animals is unclear. Fossils of Spriggina are known from the late Ediacaran period in what is now South Australia. Spriggina floundersi is the official fossil emblem of South Australia; [2] it has been found nowhere else.

The organism reached 3–5 centimetres (1.2–2.0 in) in length and may have been predatory. Its bottom was covered with two rows of tough interlocking plates, while one row covered its top; its front few segments fused to form a "head."[ citation needed ]

The affinity of Spriggina is unknown; it has been variously classified as an annelid worm, a rangeomorph-like frond, a variant of Charniodiscus , a proarticulatan, an arthropod (perhaps related to the trilobites), or even an extinct phylum. The lack of known segmented legs or limbs, coupled with the presence of glide reflection instead of symmetric segments, suggests that an arthropod classification is unlikely despite some superficial resemblance. [3]

The genus Spriggina originally contained three different species—S. floundersi, S. ovata, and S. borealis—but S. ovata is now considered a junior synonym of Marywadea ovata, [4] [5] while the phylogenetic status of S. borealis remains[ as of? ] a subject of debate. [5]

Description

S. floundersi, life restoration at MUSE - Science Museum in Trento Spriggina floundersi - MUSE.jpg
S. floundersi, life restoration at MUSE – Science Museum in Trento
Cast of S. floundersi at Houston Museum of Natural Science Spriggina, Ediacaran metazoan, Vendian, Ediacara Hills, south Australia - Houston Museum of Natural Science - DSC01385.JPG
Cast of S. floundersi at Houston Museum of Natural Science

Spriggina grew to 3–5 centimetres (1.2–2.0 in) in length and was approximately oblong. The organism was segmented, with no fused segments; the segments were sometimes curved. [6] The upper surface of the organism was covered by one row of overlapping cuticular plates, the underside with paired plates. [6]

The first two segments formed a "head". The front segment had the shape of a horseshoe with a pair of depressions on its upper surface; these may have represented eyes. [6] The second segment may have borne antennae. Subsequent segments bore annulations. [6]

Some fossils have what may be a circular mouth at the centre of the semicircular head, although interpretation is hampered by the small size of the creature relative to the large grains of sandstones in which it is preserved. [6] Legs are not preserved.

The symmetry observed is not exactly bilaterian [6] but appears to be a glide reflection, where opposite segments are shifted by half an interval. [3] In some specimens the body segments tilt backwards, making roughly chevron patterns; while in others they are more or less straight. There appear to be fairly complex variations between these two extremes.[ citation needed ]

Discovery and naming

The genus was named after Reg Sprigg who discovered the fossils of the Ediacara Hills—part of the Flinders Ranges in South Australia—and was a proponent of their recognition as multicellular organisms. [1] Spriggina floundersi is at present the only generally accepted species in this genus. The specific name "floundersi" refers to amateur South Australian fossil hunter Ben Flounders. [7] Spriggina ovata has now been moved into its own genus, Marywadea . [8]

Spriggina is known only from beds of Ediacaran age. Fossils from the Vindhyan basin, reliably dated to around 1,650 million years old, [9] have been classified as Spriggina, [10] but in all likelihood represent microbial artifacts. [9]

Spriggina possessed a tough, though uncalcified body, evident from the fossils' preservation: always as a mould in the lower surface of the fossiliferous bed.

Classification

Digitally enhanced image of a Spriggina fossil Spriggina flounensi C.jpg
Digitally enhanced image of a Spriggina fossil

Like many of the Ediacara biota, the relationship of Spriggina to other groups is unclear. It bears some similarity to the living polychaete worm Tomopteris and Amphinomidae, [11] but its lack of chaetae, along with other lines of evidence, suggests that it cannot be placed in this phylum. [12] It was also compared to the rangeomorphs, [13] frondose members of the Ediacara biota that may represent a separate kingdom. [14] While its glide symmetry may suggest otherwise, Spriggina is considered by some other researchers to be an arthropod; its superficial resemblance to the trilobites may suggest a close relationship to this class. [13] This similarity to trilobites could also be an example of convergent evolution. [15] Spriggina may have been predatory, and may have played a role in initiating the Cambrian transition. [16]

See also

Related Research Articles

<span class="mw-page-title-main">Ediacaran</span> Third and last period of the Neoproterozoic Era

The Ediacaran is a geological period of the Neoproterozoic era that spans 96 million years from the end of the Cryogenian period at 635 Mya to the beginning of the Cambrian period at 538.8 Mya. It is the last period of the Proterozoic eon as well as the last of the so-called "Precambrian supereon", before the beginning of the subsequent Cambrian period marks the start of the Phanerozoic eon, where recognizable fossil evidence of life becomes common.

The cloudinids, an early metazoan family containing the genera Acuticocloudina, Cloudina and Conotubus, lived in the late Ediacaran period about 550 million years ago. and became extinct at the base of the Cambrian. They formed millimetre-scale conical fossils consisting of calcareous cones nested within one another; the appearance of the organism itself remains unknown. The name Cloudina honors the 20th-century geologist and paleontologist Preston Cloud.

<i>Pteridinium</i> Ediacaran fossil

Pteridinium is an erniettomorph found in a number of Precambrian deposits worldwide. It is a member of the Ediacaran biota.

<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>Charnia</i> Genus of frond-like lifeforms

Charnia is an extinct genus of frond-like lifeforms belonging to the Ediacaran biota with segmented, leaf-like ridges branching alternately to the right and left from a zig-zag medial suture. The genus Charnia was named for Charnwood Forest in Leicestershire, England, where the first fossilised specimen was found. Charnia is significant because it was the first Precambrian fossil to be recognized as such.

<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.

Marywadea is a genus of Ediacaran biota shaped like an oval with a central ridge. It is a bilaterian organism as evidenced by its symmetry, vaguely resembling a very primitive trilobite. The fossil has an asymmetrical first chamber of the quilt. It has transverse ridges away from the central axis that may be gonads. The head is shaped as a semicircle and is the same width as the rest of the body. The ridges number about 50. There are two oval shapes below the head.

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

Cephalonega stepanovi is a fossil organism from Ediacaran deposits of the Arkhangelsk Region, Russia. It was described by Mikhail A. Fedonkin in 1976

<i>Rangea</i> Fossil taxon

Rangea is a frond-like Ediacaran fossil with six-fold radial symmetry. It is the type genus of the rangeomorphs.

<i>Parvancorina</i> Genus of fossil arnimal

Parvancorina is a genus of shield-shaped bilaterally symmetrical fossil animal that lived in the late Ediacaran seafloor. It has some superficial similarities with the Cambrian trilobite-like arthropods.

<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>Praecambridium</i> Extinct genus of marine animals

Praecambridium sigillum is an extinct organism that superficially resembles a segmented trilobite-like arthropod. It was originally described as being a trilobite-like arthropod, though the majority of experts now place it within the Proarticulata as a close relative of the much larger Yorgia. It is from the Late Ediacaran deposit of Ediacara Hills, Australia, about 555 million years ago. On average, P. sigillum had at least 5 pairs of segments, with each unit becoming progressively larger as they approach the cephalon-like head.

<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.

<span class="mw-page-title-main">Ediacaran biota</span> All organisms of the Ediacaran Period (c. 635–538.8 million years ago)

The Ediacaranbiota is a taxonomic period classification that consists of all life forms that were present on Earth during the Ediacaran Period. These were enigmatic tubular and frond-shaped, mostly sessile, organisms. Trace fossils of these organisms have been found worldwide, and represent the earliest known complex multicellular organisms. The term "Ediacara biota" has received criticism from some scientists due to its alleged inconsistency, arbitrary exclusion of certain fossils, and inability to be precisely defined.

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

Proarticulata is a proposed phylum of extinct, near-bilaterally symmetrical animals known from fossils found in the Ediacaran (Vendian) marine deposits, and dates to approximately 567 to 550 million years ago. The name comes from the Greek προ = "before" and Articulata, i.e. prior to animals with true segmentation such as annelids and arthropods. This phylum was established by Mikhail A. Fedonkin in 1985 for such animals as Dickinsonia, Vendia, Cephalonega, Praecambridium and currently many other Proarticulata are described.

<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.

<span class="mw-page-title-main">Avalon explosion</span> Proposed evolutionary event in the history of metazoa, producing the Ediacaran biota

The Avalon explosion, named from the Precambrian faunal trace fossils discovered on the Avalon Peninsula in Newfoundland, eastern Canada, is a proposed evolutionary radiation of prehistoric animals about 575 million years ago in the Ediacaran period, with the Avalon explosion being one of three eras grouped in this time period. This evolutionary event is believed to have occurred some 33 million years earlier than the Cambrian explosion, which had been long thought to be when complex life started on Earth.

<span class="mw-page-title-main">Cephalozoa</span> Extinct class of marine animals

Cephalozoa are an extinct class of primitive segmented marine organisms within the Phylum Proarticulata from the Ediacaran period. They possessed bilateral symmetry and were characterized by a thin, rounded body.

<span class="mw-page-title-main">Sprigginidae</span> Extinct family of cephalozoans

Sprigginidae is an extinct family of cephalozoans characterized by having a greater number of isomers than its sister taxon, Yorgiidae. They lived approximately 635 million years ago, in the Ediacaran period.

References

  1. 1 2 Glaessner, Martin F. (1958). "New Fossils from the Base of the Cambrian in South Australia" (PDF). Transactions of the Royal Society of South Australia. 81: 185–188. BHL page 41001421. Archived from the original (PDF) on 29 September 2007.
  2. ↑ "FOSSIL EMBLEM OF THE STATE OF SOUTH AUSTRALIA" (PDF). The South Australian Government Gazette. 2017 (8). Adelaide: Department of the Premier and Cabinet: 509. 16 February 2017. Retrieved 6 July 2017.
  3. 1 2 Ivantsov A.Yu. (2001). "Vendian and Other Precambrian "Arthropods"". Paleontological Journal. 35: 335–343.
  4. ↑ Glaessner, Martin F. & Wade, Mary (1966). "The Late Precambrian Fossils from Ediacara, South Australia" (PDF). Palaeontology. 9 (4): 599–628. Archived from the original (PDF) on 22 September 2013.
  5. 1 2 Fedonkin, Mikhail A.; Gehling, James G.; Grey, Kathleen; Narbonne, Guy M.; Vickers-Rich, Patricia (2007). The Rise of Animals: Evolution and Diversification of the Kingdom Animalia. JHU Press. ISBN   9780801886799.
  6. 1 2 3 4 5 6 McCall (2006). "The Vendian (Ediacaran) in the geological record: Enigmas in geology's prelude to the Cambrian explosion". Earth-Science Reviews. 77 (1–3): 1–229. Bibcode:2006ESRv...77....1M. doi:10.1016/j.earscirev.2005.08.004.
  7. ↑ Vickers-Rich, P. Komarower, P. The Rise and Fall of the Ediacaran Biota. The Geological Society, 2007, p. 444.
  8. ↑ Glaessner, Martin F. (1976). "A new genus of late Precambrian polychaete worms from South Australia" (PDF). Transactions of the Royal Society of South Australia. 100 (3): 169–170. Archived from the original (Free full text) on 29 September 2007.
  9. 1 2 Bengtson, Stefan; Belivanova, Veneta; Rasmussen, Birger; Whitehouse, Martin (2009). "The controversial "Cambrian" fossils of the Vindhyan are real but more than a billion years older". Proceedings of the National Academy of Sciences. 106 (19): 7729–7734. Bibcode:2009PNAS..106.7729B. doi: 10.1073/pnas.0812460106 . PMC   2683128 . PMID   19416859.
  10. ↑ De, C (2005). "Ediacara fossil assemblage in the upper Vindhyans of Central India and its significance". Journal of Asian Earth Sciences. 27 (5): 660–683. doi:10.1016/j.jseaes.2005.06.006.
  11. ↑ Donovan, S. K.; Lewis, D. N. (2001). "Fossils explained 35: The Ediacaran biota". Geology Today. 17 (3): 115–120. doi:10.1046/j.0266-6979.2001.00285.x. S2CID   128395097.
  12. ↑ Merz (2006). "Polychaete chaetae: Function, fossils, and phylogeny". Integrative and Comparative Biology. 46 (4): 481–96. doi:10.1093/icb/icj057. PMID   21672760.
  13. 1 2 "Spriggina is a Trilobitoid Ecdysozoan". Geological Society of America. Archived from the original on 4 July 2017.
  14. ↑ Seilacher, A. (1992). "Vendobionta and Psammocorallia: lost constructions of Precambrian evolution". Journal of the Geological Society . 149 (4): 607–613. Bibcode:1992JGSoc.149..607S. doi:10.1144/gsjgs.149.4.0607. S2CID   128681462 . Retrieved 21 June 2007.
  15. ↑ Conway Morris, S. (1993). "The fossil record and the early evolution of the Metazoa" (PDF). Nature. 361 (6409): 219. Bibcode:1993Natur.361..219M. doi:10.1038/361219a0. S2CID   86276440. Archived from the original (PDF) on 4 August 2016. Retrieved 11 October 2016.
  16. ↑ McMenamin, M. A. S. (2003). "Origin and early evolution of predators: The ecotone model and early evidence for macropredation". In P. Kelley; M. Kowalewski; T. Hansen (eds.). Predator-Prey Interactions in the Fossil Record.
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