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Vetulocystidae

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Vetulocystidae
Temporal range: 541–501 Ma Early Cambrian - Middle Cambrian
Reconstruction of 2 specimens of Vetulocystis catenata (in the lower part), and the chordate Cathaymyrus diadexus.
Scientific classification
Kingdom:
Superphylum:
(unranked):
Vetulocystida
Family:
Vetulocystidae

Shu, et al., 2004
Type species
Vetulocystis catenata
Shu, et al., 2004
Genera

Vetulocystidae is the only family of the taxon Vetulocystida, which is a group of extinct deuterostomes of uncertain phylogenetic position. Vetulocystidae is made up of the genera Vetulocystis, Dianchicystis and Thylacocercus.[1][2]

Features

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The body consists of a voluminous thecal-shaped section (similar to the outer shape of the pterobranchs), where there are two cone-shaped structures (anterior and posterior) and a lenticular respiratory organ; and another small section attached to the substrate.[1]

The anterior cone-shaped structure is believed to have constituted the mouth, due to its similarity to other primitive echinoderms (such as stylophoids and blastoids); while the posterior structure (similar to that of the cystoids and eocrinoids) fulfilled the functions of anus and gonopore. Furthermore, and unlike many other echinoderms, these animals lacked a calcified skeleton.[1]

Paleoecology

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They were probably sessile, although it is possible that the part attached to the substrate produced a slow displacement. They were fed by filtration.[1]

Phylogeny

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Despite sharing certain surface characteristics with other taxa (such as Urochordata), Vetulocystida is believed to belong to the Echinodermata stem group; and that it is also related to the taxon Vetulicolia. Based on this, Vetulocystida would represent the transition from the body plan of the vetulicolians to one of the echinoderms.

Old studies suggest the following phylogenetic relationships:[1]

Ambulacraria
Echinodermata (s. l.)

Vetulocystida (Vetulocystidae)

Echinodermata

Homalozoa

Other echinoderms

Hemichordata

However, subsequent studies result in the following phylogeny:[3]

Both cases imply a close relationship with vetulicolians, which is supported by physiological similarities and phylogenetic analyzes.[3]

References

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  1. ^ a b c d e Shu, D.-G.; Conway Morris, S.; Han, J.; Zhang, Z.-F.; Liu, J.-N. (2004). "Ancestral echinoderms from the Chengjiang deposits of China". Nature. 430 (6998): 422–428. Bibcode:2004Natur.430..422S. doi:10.1038/nature02648. PMID 15269760. S2CID 4421182.
  2. ^ Rare primitive deuterostomes from the Cambrian (Series 3) of Utah (PDF). Vol. 89. 2015. pp. 631–636.
  3. ^ a b Han, Jian; Conway Morris, Simon; Ou, Qiang; Shu, Degan; Huang, Hai (2017). "Meiofaunal deuterostomes from the basal Cambrian of Shaanxi (China)" (PDF). Nature. 542 (7640): 228–231. Bibcode:2017Natur.542..228H. doi:10.1038/nature21072. PMID 28135722. S2CID 353780.
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