Vetulicolia
| Vetulicolia Temporal range: Cambrian Stage 3–Middle Cambrian |
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| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Subphylum: | Vetulicolia |
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Vetulicolia is an extinct taxon, either phylum or subphylum in rank, encompassing several Cambrian organisms. The vetulicolian body comprises two parts: a voluminous anterior forebody, tipped with an anteriorly positioned mouth, and lined with a row of five round to oval-shaped features on each lateral side, which have been interpreted as gills - or at least openings in the vicinity of the pharynx, and a posterior section that primitively comprises seven segments, and functions as a tail. All vetulicolians lack preserved appendages of any kind, having no legs, feelers, or even eyes. The area where the anterior and posterior parts join is constricted. Their affinity has been uncertain; they have been considered to represent stem- and crown-group arthropods, stem-group vertebrates, and early deuterostomes. The general scientific consensus formerly (before 2001) considered them early limbless arthropods, but now considers them early deuterostomes. Recently examined Vetulicolian fossils show the presence of -like structures. Therefore, it can be concluded that vetulicolians are crown-group chordates and probably the sister group of modern tunicates.
As originally proposed, the phylum included the Didazoonidae (Didazoon, Pomatrum, and Xidazoon) and the Vetulicolidae (Vetulicola, and Banffia). Other groups which may be related include the yunnanozoans.
The taxonomic placement of the Vetulicolians remains controversial. One researcher have argued that the vetulicolians probably represent an early side-branch of deuterostomes, and that this implies that segmentation in cephalochordates and vertebrates may be derived from the common ancestor of protostomes and deuterostomes. However, the researchers who described Skeemella from the Middle Cambrian of Utah regard it as having affinity to Vetulicolia, but also as having arthropod features, thus confounding assignment of Vetulicolia to Deuterostomia.
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