Vetulicolia

Vetulicola cuneata fossil.

Vetulicolia as a phylum was created by Chinese palaeontologist Degan Shu and his research team at the Northwest University in Xi'an, China, along with Simon Conway Morris at the University of Cambridge in 2001.[3] The name was derived from Vetulicola cuneata, the first species described by Hou Xian-guang in 1987 from the Lower Cambrian Chiungchussu Formation in Chengjiang, China.[2][4] The purpose was to include all related Cambrian animals known under the families Didazoonidae (Didazoon, Pomatrum, and Xidazoon) and Vetulicolidae (Vetulicola, and Banffia) as a separate group of animals.[1][3] Other animals which may be related include the yunnanozoans.[3]

The taxonomic placement of the vetulicolians remains controversial. The original researcher Shu is of the opinion 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.[7] However, Derek Briggs of Yale University and his team who described Skeemella from the Middle Cambrian of Utah regard it as having affinity to protostomes with important arthropod features, thus confounding assignment of Vetulicolia to Deuterostomia.[12] Thurston C. Lacalli of the University of Saskatchewan, Saskatoon, Canada, agreed to the deuterostome position, but suggested that the animals were more likely related to tunicates.[13]

Dominguez and Jefferies have argued, based on morphological analysis, that Vetulicola (and by implication, other vetulicolians) is a urochordate, and probably a stem-group larvacean. Some question the relation to tunicates and larvaceans, as there is no evidence of segmentation in tunicates, larval or adult, that is comparable to segmentation in vetulicolians, that the anus of urochordates is within the atrium, while that of vetulicolians is positioned at the terminal end of the tail, and, perhaps most importantly, there is no exhalant siphon, or analogous structure, seen in vetulicolians.[14] However, a discovery of a new vetulicolian, Nesonektris aldridgei, from Australia in 2014 supported a position close to urochordates for vetulicolians.[9]

The monophyly of Deuterostomia is not strongly supported.[15][16] If deuterostomes are paraphyletic, pharyngeal slits were probably present in the common ancestor of Bilateria and vetulicolians may be stem-group protostomes that retained the ancestral pharyngeal slits.[16] If this is the case, banffids, which appear to lack pharyngeal slits, may be more closely related to crown-group protostomes than other vetulicolians.[16]

Vetulicola rectangulata fossil

From their superficially tadpole-like forms, leaf or paddle-shaped tails, and various degrees of streamlining, it is assumed that all vetulicolians discovered thus far were swimming animals that spent much, if not all, of their time living in the water column.[14] Some groups, like the genus Vetulicola, were more streamlined (complete with ventral keels) than other groups, such as the tadpole-like Didazoonidae.[14]

Because all vetulicolians had mouths which had no features for chewing or grasping, it is automatically assumed that they were not predators.[14] Since vetulicolians possessed gill slits, many researchers regard these organisms as planktivores. The sediment infills in the guts of their fossils have led some to suggest that they were deposit feeders. This idea has been contested, as deposit feeders tend to have straight guts, whereas the hindguts of vetulicolians were spiral-shaped. Some researchers propose that the vetulicolians were "selective deposit-feeders" which actively swam from one region of the seafloor to another, while supplementing their nutrition with filter-feeding.[14]

• Superphylum Deuterostomia
  • Phylum Vetulicolia
    • Class Vetulicolida
      • • Genus Nesonektris[9]
          • N. aldridgei
        • Genus Shenzianyuloma[6]
          • S. yunnanense
      • Family Vetulicolidae
        • Genus Vetulicola
          • V. rectangulata
          • V. cuneata
          • V. gangtoucunensis
          • V. monile
          • V. longbaoshanensis
        • Genus Ooedigera[17]
          • O. peeli
        • Genus Yuyuanozoon[14][18]
          • Y. magnificissimi
      • Family Beidazooidae
        • Genus Beidazoon
          • B. venustum (synonym = Bullivetula variola)
      • Family Didazoonidae
        • Genus Didazoon
          • D. haoae
        • Genus Pomatrum (=Xidazoon)
          • P. ventralis (Xidazoon stephanus)
          • Yunnanozoon lividum
    • ?Class Banffozoa
      • Genus Skeemella
        • Sk. clavula
      • Family Banffiidae
        • Genus Banffia
          • B. constricta[19]
          • B. episoma
    • Class Heteromorphida
      • Family Heteromorphidae
        • Genus Heteromorphus
          • H. longicaudatus (synonym=Banffia confusa)
          • "Form A" (unnamed species)

Wikispecies has information related to Vetulicolia.

Wikimedia Commons has media related to Vetulicolia.

• New phylum on the block – Accessed January 3, 2008
• Photos and drawings of fossils of various Vetulicolians – Accessed January 3, 2008