Didazoonidae is a

vetulicolian Vetulicolia is a group of bilaterian marine animals encompassing several extinct species from the Cambrian, and possibly Ediacaran, periods. As of 2023, the majority of workers favor placing Vetulicolians in the stem group of the Chordata, but ...

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

within the

order Order, ORDER or Orders may refer to: * A socio-political or established or existing order, e.g. World order, Ancien Regime, Pax Britannica * Categorization, the process in which ideas and objects are recognized, differentiated, and understood ...

Vetulicolata Vetulicolida is a class of vetulicolians. It consists of the order Vetulicolata (which contains the families Vetulicolidae and Didazoonidae) and the genus ''Nesonektris'', which is of uncertain placement. It is distinguished from the Banffozo ...

. It is characterized by a relatively thin-walled, non-biomineralized body and a large, round anterior opening surrounded by an oral disc. It may be

paraphyletic Paraphyly is a taxonomic term describing a grouping that consists of the grouping's last common ancestor and some but not all of its descendant lineages. The grouping is said to be paraphyletic ''with respect to'' the excluded subgroups. In co ...

, even if the phylum

Vetulicolia Vetulicolia is a group of bilaterian marine animals encompassing several extinct species from the Cambrian, and possibly Ediacaran, periods. As of 2023, the majority of workers favor placing Vetulicolians in the stem group of the Chordata, but ...

monophyletic In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria: # the grouping contains its own most recent co ...

Description

Didazoonids have an ovoid to subquadrate anterior section divided into six subdivisions marked by five circumventing lines perpendicular to the body axis. Cowl-shaped lateral pouches appear along each side of the anterior section, coincident with the five dividing lines. The anterior opening is large, round, and surrounded by a circumventing oral disc. The posterior section has seven segments, which in some species each carry up to six annulations.

Taxonomy

Didazoonidae was erected to group ''

Didazoon ''Didazoon haoae'' is an extinct species of vetulicolid vetulicolian described by Shu, et al. based on fossils found in the Qiongzhusi (Chiungchussu) Formation, Yu'anshan Member (Eoredlichia zone), Lower Cambrian, in the Dabanqiao area (Kunming), ...

''. ''

Xidazoon ''Pomatrum'' is an extinct vetulicolian, the senior synonym of ''Xidazoon''; the latter taxon was described by Shu, et al. (1999) based on fossils found in the Qiongzhusi (Chiungchussu) Formation, Yu'anshan Member (Eoredlichia zone), Lower Cambri ...

''. and ''

Pomatrum ''Pomatrum'' is an extinct vetulicolian, the senior synonym of ''Xidazoon''; the latter taxon was described by Shu, et al. (1999) based on fossils found in the Qiongzhusi (Chiungchussu) Formation, Yu'anshan Member (Eoredlichia zone), Lower Cambri ...

'', although ''Xidazoon'' has since been shown to be a junior synonym of ''Pomatrum''. ''

Yuyuanozoon ''Yuyuanozoon magnificissimi'', from the Cambrian Stage 3 Chengjiang lagerstatte, is the largest known vetulicolian, an extinct species of marine animal, with specimens up to 20 cm in length compared to 5–14 cm for other vetulicolian species. ...

'' was moved to the Didazoonidae after additional specimens illuminated more details of the anterior opening and posterior segment annulations. ''

Nesonektris ''Nesonektris aldridgei'' is an extinct vetulicolian from the Late Botomian-aged Emu Bay Shale Lagerstätte in Kangaroo Island, Australia. So far, it is the fourth described vetulicolian that is not restricted to the Maotianshan Shales (the oth ...

'' has also been assigned to Didazoonidae by some workers, but this has not been widely accepted. A 2024 study has found the Didazoonidae (without ''Nesonektris'') to be a paraphyletic grade of the vetulicolians closest to crownward

chordates A chordate ( ) is a bilaterian animal belonging to the phylum Chordata ( ). All chordates possess, at some point during their larval or adult stages, five distinctive physical characteristics ( synapomorphies) that distinguish them from ot ...

as shown in this simplified cladogram: An earlier study in 2014 placed vetulicolians as the sister-group to tunicates, but was unable to resolve any relationships among vetulicolians as a group:

References

Works cited

* * * * * * {{Taxonbar, from1=Q5274089 Vetulicolia Prehistoric chordate families