Ancalagon
Temporal range:
Reconstruction of Ancalagon minor
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Stem group: Priapulida (?)
Class: †Archaeopriapulida
Family: †Ancalagonidae
Conway Morris, 1977[1]
Genus: †Ancalagon
Conway Morris, 1977[1]
Species
  • †A. minor (Walcott, 1911) Conway Morris, 1977 (type)
Synonyms
  • Ottoia minor Walcott 1911[2]

Ancalagon minor is an extinct priapulid worm known from the Cambrian Burgess Shale.[3]

Because it superficially resembles the modern-day internal parasites known as the acanthocephalids or "spiny-headed worms," A. minor was once thought to be, or once thought to resemble the hypothetical free-living ancestor of acanthocephalids.[3][4] Two specimens of Ancalagon (worm) are known from the Greater Phyllopod bed, where they comprise < 0.01% of the community.[5]

Along with the other Cambrian worms such as Ottoia, Selkirkia, Louisella, Fieldia, Scolecofurca, and Lecythioscopa, the organism may fall into a clade termed "Archaeopriapulida," a stem group to the Priapulids proper.[6] However, the morphological similarity of these organisms to their modern cousins is remarkable, especially for the Burgess Shale.[7] A phylogenetic analysis does not provide a great deal of resolution to the relationships between these basal worms.[8]

Etymology

The generic name is a homage to the dragon Ancalagon of J.R.R. Tolkien's Middle-earth legendarium, in reference to the worm's prominent rows of hooks on its proboscis.[9] The species was previously placed in the genus Ottoia, as Ottoia minor, but was removed by Simon Conway Morris, who noted morphological differences.[10]

Morphology

Ancalagon had a slender, cyndrical, radially symmetric body[10] averaging 6 centimeters in length. Its proboscis was armed with circum-oral hooks at the anterior. There were about 10 of these hooks, equal in size and with prominent bases. Directly posterior was an unarmed space, followed by posteriorly directed spinose hooks. The trunk is annulated with 0.2 to 0.25 millimeter spacing, and carried rows of setae possibly performing sensory functions. The apparent absence of retractor muscles correlates with Ancalagon's inability to significantly invert its proboscis. The organism was probably a burrowing predator.[1]

See also

References

  1. 1 2 3 Conway Morris, S. "Fossil priapulid worms". Special Papers in Palaeontology. 20.
  2. ↑ Haaramo, Mikko (2003). "Scalidophora – †palaeoscolecids, priapulids, mud dragons and brush heads". Mikko's Phylogeny Archive. Retrieved May 14, 2019.
  3. 1 2 Conway Morris, S. (1979). "The Burgess Shale (Middle Cambrian) Fauna". Annual Review of Ecology and Systematics. 10: 327–349. doi:10.1146/annurev.es.10.110179.001551.
  4. ↑ Morris, S. C.; Crompton, D. W. T. (1982). "The Origins and Evolution of the Acanthocephala". Biological Reviews. 57: 85–115. doi:10.1111/j.1469-185X.1982.tb00365.x. S2CID 84098740.
  5. ↑ 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.
  6. ↑ Por, F. D. (1983). "Class Seticoronaria and Phylogeny of the Phylum Priapulida". Zoologica Scripta. 12 (4): 267–272. doi:10.1111/j.1463-6409.1983.tb00510.x. S2CID 85091685.
  7. ↑ Huang, D. Y.; Vannier, J.; Chen, J.Y. (2004). "Anatomy and lifestyles of Early Cambrian priapulid worms exemplified by Corynetis and Anningvermis from the Maotianshan Shale (SW China)". Lethaia. 37: 21–33. doi:10.1080/00241160410005088.
  8. ↑ Wills, M. A. (1 April 1998). "Cambrian and Recent Disparity: the Picture from Priapulids". Paleobiology. 24 (2): 177–199. doi:10.1666/0094-8373(1998)024[0177:CARDTP]2.3.CO;2. JSTOR 2401237. S2CID 88647544.
  9. ↑ "Ancalagon minor". The Burgess Shale. 10 June 2011. Retrieved 23 October 2023.
  10. 1 2 Whittington, H.B. (1911). "Middle Cambrian Annelids". Cambrian Geology and Paleontology. 2: 109–142.
  • "Ancalagon minor". Burgess Shale Fossil Gallery. Virtual Museum of Canada. 2011. (Burgess Shale species 96)
This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.