Selkirkia

Last updated

Selkirkia
Temporal range: Cambrian Stage 3–Floian
Selkirkia columbia ROM63131.jpg
Selkirkia columbia fossil from the Burgess Shale. From Smith et al. (2015) [1]
Selkirkia columbia Restoration.png
Restoration of Selkirkia columbia
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Stem group: Priapulida (?)
Class: Archaeopriapulida
Family: Selkirkiidae
Conway Morris, 1977 [2]
Genus: Selkirkia
Walcott, 1911
Species
  • S. columbia Conway Morris, 1977
  • S. elongata Luo & Hu, 1999
  • S. sinica Luo & Hu, 1999
  • S. spencei Resser, 1939
  • S. willoughbyi Conway Morris & Robison, 1986
  • S. tsering Nanglu 2024

Selkirkia is a genus of predatory, [3] tubicolous priapulid worms known from the Middle Cambrian Burgess Shale, Ogygopsis Shale, Puncoviscana Formation [4] and the Early Ordovician Fezouata Formation. [5] 142 specimens of Selkirkia are known from the Greater Phyllopod bed, where they comprise 0.27% of the community. [6] In the Burgess Shale, 20% of the tapering, organic-walled tubes are preserved with the worm inside them, whereas the other 80% are empty (or sometimes occupied by one or more small agnostid trilobites). [3] Whilst alive, the tubes were probably vertical, whereas trilobite-occupied tubes are horizontal. [3]

Contents

Morphology

Selkirkia had a body divisible into a proboscis towards the anterior of a trunk enclosed by a tube. The proboscis would have been partially invertable and was armed with several spinules and spines, decreasing size distally overall. It was controlled by at least two sets of anterior retractor muscles. Immediately behind the proboscis was the trunk, smooth for the most part but lined with papillae towards the anterior. Surrounding the trunk was the tube, which way very finely annulated (4 annulations per 0.1 millimeters).

History

Members of Cambrorhytium were originally described as Selkirkia before their identification as a separate genus. [7]

Related Research Articles

<span class="mw-page-title-main">Burgess Shale</span> Fossil-bearing rock formation in the Canadian Rockies

The Burgess Shale is a fossil-bearing deposit exposed in the Canadian Rockies of British Columbia, Canada. It is famous for the exceptional preservation of the soft parts of its fossils. At 508 million years old, it is one of the earliest fossil beds containing soft-part imprints.

<span class="mw-page-title-main">Priapulida</span> Phylum of unsegmented marine worms

Priapulida, sometimes referred to as penis worms, is a phylum of unsegmented marine worms. The name of the phylum relates to the Greek god of fertility, because their general shape and their extensible spiny introvert (eversible) proboscis may resemble the shape of a human penis. They live in the mud and in comparatively shallow waters up to 90 metres (295 ft) deep. Some species show a remarkable tolerance for hydrogen sulfide, anoxia and low salinity. Halicryptus spinulosus appears to prefer brackish shallow waters. They can be quite abundant in some areas. In an Alaskan bay as many as 85 adult individuals of Priapulus caudatus per square meter has been recorded, while the density of its larvae can be as high as 58,000 per square meter.

<i>Opabinia</i> Extinct stem-arthropod species found in Cambrian fossil deposits

Opabinia regalis is an extinct, stem group arthropod found in the Middle Cambrian Burgess Shale Lagerstätte of British Columbia. Opabinia was a soft-bodied animal, measuring up to 7 cm in body length, and its segmented trunk had flaps along the sides and a fan-shaped tail. The head shows unusual features: five eyes, a mouth under the head and facing backwards, and a clawed proboscis that probably passed food to the mouth. Opabinia probably lived on the seafloor, using the proboscis to seek out small, soft food. Fewer than twenty good specimens have been described; 3 specimens of Opabinia are known from the Greater Phyllopod bed, where they constitute less than 0.1% of the community.

<i>Ottoia</i> Extinct genus of priapulid worms

Ottoia is a stem-group archaeopriapulid worm known from Cambrian fossils. Although priapulid-like worms from various Cambrian deposits are often referred to Ottoia on spurious grounds, the only clear Ottoia macrofossils come from the Burgess Shale of British Columbia, which was deposited 508 million years ago. Microfossils extend the record of Ottoia throughout the Western Canada Sedimentary Basin, from the mid- to late- Cambrian. A few fossil finds are also known from China.

Fieldia is a genus of worms known from the Cambrian Burgess Shale, and assigned to the priapulids.

A number of assemblages bear fossil assemblages similar in character to that of the Burgess Shale. While many are also preserved in a similar fashion to the Burgess Shale, the term "Burgess Shale-type fauna" covers assemblages based on taxonomic criteria only.

<span class="mw-page-title-main">Wheeler Shale</span> Geologic formation in Utah notable for trilobite fossils

The Wheeler Shale is a Cambrian (c. 507 Ma) fossil locality world-famous for prolific agnostid and Elrathia kingii trilobite remains and represents a Konzentrat-Lagerstätte. Varied soft bodied organisms are locally preserved, a fauna and preservation style normally associated with the more famous Burgess Shale. As such, the Wheeler Shale also represents a Konservat-Lagerstätten.

The fossils of the Burgess Shale, like the Burgess Shale itself, are fossils that formed around 505 million years ago in the mid-Cambrian period. They were discovered in Canada in 1886, and Charles Doolittle Walcott collected over 65,000 specimens in a series of field trips up to the alpine site from 1909 to 1924. After a period of neglect from the 1930s to the early 1960s, new excavations and re-examinations of Walcott's collection continue to reveal new species, and statistical analysis suggests that additional discoveries will continue for the foreseeable future. Stephen Jay Gould's 1989 book Wonderful Life describes the history of discovery up to the early 1980s, although his analysis of the implications for evolution has been contested.

<i>Ancalagon</i> (worm) Extinct genus of priapulid worms

Ancalagon minor is an extinct priapulid worm known from the Cambrian Burgess Shale.

<span class="mw-page-title-main">Archaeopriapulida</span> Class of marine worms

Archaeopriapulida is a group of priapulid worms known from Cambrian lagerstätte. The group is closely related to, and very similar to, the modern Priapulids. It is unclear whether it is mono- or polyphyletic. Despite a remarkable morphological similarity to their modern cousins, they fall outside of the priapulid crown group, which is not unambiguously represented in the fossil record until the Carboniferous. In addition to well-preserved body fossils, remains of several archaeopriapulid taxa are known to have been preserved primarily as organic microfossils, such as isolated scalids and pharyngeal teeth. They are probably closely related or paraphyletic to the palaeoscolecids; the relationship between these basal worms is somewhat unresolved.

<span class="mw-page-title-main">Palaeoscolecid</span> Extinct class of worms

The palaeoscolecids are a group of extinct ecdysozoan worms resembling armoured priapulids. They are known from the Lower Cambrian to the lower Ludfordian ; they are mainly found as disarticulated sclerites, but are also preserved in many of the Cambrian lagerstätten. They take their name from the typifying genus Palaeoscolex. Other genera include Cricocosmia from the Lower Cambrian Chengjiang biota. Their taxonomic affinities within Ecdysozoa have been the subject of debate.

The Phyllopod bed, designated by USNM locality number 35k, is the most famous fossil-bearing member of the Burgess Shale fossil Lagerstätte. It was quarried by Charles Walcott from 1911–1917, and was the source of 95% of the fossils he collected during this time; tens of thousands of soft-bodied fossils representing over 150 genera have been recovered from the Phyllopod bed alone.

Cambrorhytium is an enigmatic fossil genus known from the Latham Shale (California), and the Chengjiang (China) and Burgess Shale lagerstätte. 350 specimens of Cambrorhytium are known from the Greater Phyllopod bed, where they comprise 0.7% of the community.

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

Emeraldella is a genus of arthropod known from the Middle Cambrian of North America. The type species E. brocki was described in 1912 from the Burgess Shale. 21 specimens of Emeraldella are known from the Greater Phyllopod bed, where they comprise < 0.1% of the community. A re-study on the species was done in 2012. A second species E. brutoni is known from the Wheeler Shale, which was described in 2011. An additional specimen of E. brutoni was described in 2019, which revealed more of the anatomy. It has been placed as a basal member of the clade Vicissicaudata within Artiopoda, a group of arthropods containing trilobites and their relatives.

<i>Louisella</i> Extinct genus of worms

Louisella is a genus of worm known from the Middle Cambrian Burgess Shale. It was originally described by Charles Walcott in 1911 as a holothurian echinoderm, and represents a senior synonym of Miskoia, which was originally described as an annelid. 48 specimens of Louisella are known from the Greater Phyllopod bed, where they comprise < 0.1% of the community. It has been stated to have palaeoscolecid-like sclerites, though this is not in fact the case.

<i>Pagetia</i> Genus of trilobites

Pagetia is a genus of small trilobite, assigned to the Eodiscinid family Pagetiidae and which had global distribution during the Middle Cambrian. The genus contains 55 currently recognized species, each with limited spatial and temporal ranges.

Scolecofurca is a genus of stem-group priapulid worm dating from the Middle Cambrian period approximately 505 million years ago.

Lecythioscopa is a genus of probable archaeopriapulid known from two specimens from the Walcott Quarry from the Middle Cambrian Burgess Shale.

<i>Erratus</i> Extinct genus of Cambrian arthropod

Erratus is an extinct genus of marine arthropod from the Cambrian of China. Its type and only species is Erratus sperare. Erratus is likely one of the most basal known arthropods, and its discovery has helped scientists understand the early evolution of arthropod trunk appendages. Some of the stem-arthropods like radiodonts did not have legs, instead they had flap like appendages that helped them swim. Erratus on the other hand had not only flaps but also a set of primitive legs. It also supported the theory that the gills of aquatic arthropods probably evolved into the wings and lungs of terrestrial arthropods later in the Paleozoic.

<span class="mw-page-title-main">Paleobiota of the Burgess Shale</span>

This is a list of the biota of the Burgess Shale, a Cambrian lagerstätte located in Yoho National Park in Canada.

References

  1. Smith, M. R.; Harvey, T. H. P.; Butterfield, N. J. (2015). "The macro- and microfossil record of the Cambrian priapulid Ottoia" (PDF). Palaeontology. 58 (4): 705–721. Bibcode:2015Palgy..58..705S. doi: 10.1111/pala.12168 .
  2. Conway Morris, S (1977). "Fossil priapulid worms". Special Papers in Palaeontology. 20.
  3. 1 2 3 Chatterton, B. D. E.; Collins, D. H.; Ludvigsen, R. (2003). "Cryptic behaviour in trilobites: Cambrian and Silurian examples from Canada, and other related occurrences". In Lane, P. D; Siveter, D. J; Fortey, R. A (eds.). Trilobites and Their Relatives. Special Papers in Palaeontology. Vol. 70. The Palaeontological Association. pp. 157–173. ISBN   978-0-901702-81-4.
  4. Aceñolaza, Florencio; Guillermo, Aceñolaza (2005). "La formación Puncoviscana y unidades estratigráficas vinculadas en el neoproterozoico - Cámbrico temprano del noroeste argentino" (PDF). Latin American Journal of Sedimentology and Basin Analysis (in Spanish). 12 (2): 65–87. Retrieved 7 December 2015.
  5. Nanglu, Karma; Ortega-Hernández, Javier (March 2024). "Post-Cambrian survival of the tubicolous scalidophoran Selkirkia". Biology Letters. 20 (3). doi: 10.1098/rsbl.2024.0042 . ISSN   1744-957X.
  6. Caron, Jean-Bernard; Jackson, Donald A. (October 2006). "Taphonomy of the Greater Phyllopod Bed community, Burgess Shale". PALAIOS. 21 (5): 451–65. Bibcode:2006Palai..21..451C. doi:10.2110/palo.2003.P05-070R. JSTOR   20173022. S2CID   53646959.
  7. See Cambrorhytium .