Chancelloriidae

Chancelloriidae
Temporal range: Early Cambrian–Late Cambrian
Chancelloria
Life restoration of Allonnia
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Order: †Chancelloriida
Family: †Chancelloriidae
Walcott, 1920
Genera
Chancelloria eros fossil, Wheeler Shale, House Range, Utah

The Chancelloriids are an extinct family of superficially sponge-like animals common in sediments from the Early Cambrian to the early Late Cambrian. Many of these fossils consists only of spines and other fragments, and it is not certain that they belong to the same type of organism. Other specimens appear to be more complete and to represent sessile, radially symmetrical hollow bag-like organisms with a soft skin armored with star-shaped calcareous sclerites from which radiate sharp spines.

Classifying the chancelloriids is difficult. Some paleontologists classify them as sponges, an idea which chancelloriids' sessile lifestyle and simple structure make plausible. Other proposals suggest that they were more advanced, or at least originated from more advanced ancestors; for example chancelloriids' skins appear to be much more complex than those of any sponge. It has been suggested that chancelloriids were related to the "chain mail" armored slug-like halkieriids, which are typically considered to be stem-group molluscs. While the sclerites of the two groups are very similar right down to the microscopic level, the large dissimilarity in the body plans of the two groups is difficult to reconcile with this hypothesis.[1] The proposed clade containing the two groups, "Coeloscleritophora", is generally not thought to be monophyletic.[2][3] Recent research has suggested that chancellorids represent an independent group of basal eumetazoans.[4]

  1. ^ Bengtson, Stefan; Collins, Desmond (August 2009). "Burgess Shale Chancelloriids – A Prickly Problem" (PDF). In Smith, Martin R.; O'Brien, Lorna J.; Caron, Jean-Bernard (eds.). Abstract Volume. International Conference on the Cambrian Explosion (Walcott 2009). Toronto, Ontario, Canada: The Burgess Shale Consortium (published 31 July 2009). ISBN 978-0-9812885-1-2.
  2. ^ Bengtson, S; Collins, D (2015). "Chancelloriids of the Cambrian Burgess Shale". Palaeontologia Electronica. doi:10.26879/498. ISSN 1094-8074.
  3. ^ Murdock, Duncan J. E. (October 2020). "The 'biomineralization toolkit' and the origin of animal skeletons". Biological Reviews. 95 (5): 1372–1392. doi:10.1111/brv.12614. ISSN 1464-7931. PMID 32447836. S2CID 218872873.
  4. ^ Yun, Hao; Zhang, Xingliang; Brock, Glenn A.; Li, Luoyang; Li, Guoxiang (2021-02-05). "Biomineralization of the Cambrian chancelloriids". Geology. 49 (6): 623–628. doi:10.1130/g48428.1. ISSN 0091-7613. S2CID 234069516.