Banffozoa

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Banffozoa
Temporal range: about 518–501  Ma
Fossil of Heteromorphus-like species "Form A".png
"Form A" fossil
Diagram of Heteromorphus-like species "Form A".png
"Form A" diagram
Banffia-constricta-fossils.png
Skeemella clavula KUMIP 310501.jpg
Fossils and diagrams of banffozoans
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade?:† Vetulicolia
Class:† Banffozoa
Caron 2006
Type species
† Banffia constricta
Walcott, 1911
Orders
Synonyms

Heteromorphida Shu 2005 (see text)

Banffozoa (also called Heteromorphida) [1] is an extinct class of bilaterians. Most workers place it in the Vetulicolia, [2] [3] but the protostome-like features of some members have motivated ongoing debate. [4] Banffozoa consists of the order Banffiata (which has only one family, Banffiidae) [2] as well as a dwarf "Form A" that has not been formally described or named. [5] Skeemella has been placed incertae sedis in this class, but has more recently been placed with the Banffiidae (if it is a banffozoan or vetulicolian at all). Banffozoa may be paraphyletic even if Vetulicolia is monophyletic. [2]

Contents

Description

Banffozoans have a bipartite body with a smooth anterior part that generally lacks evidence of segmentation and may or may not have a lateral groove. The posterior section features far more segments than the Vetulicolida, and (except in Skeemella) these segments are each much narrower as well. Lateral pouches such as those found in the Vetulicolida have not been seen, although some questions remain regarding their possible presence in Skeemella. [6]

The entire body is twisted dextrally (from an anterior view). Gut diverticula may be present. [6] The anus is terminal, [7] despite initial reports to the contrary in Heteromorphus. [8]

The length of banffozoans ranges from 1 cm for "Form A" [5] to more than 14 cm for Skeemella. [9]

Form A

In addition to its much smaller size (even smaller than Beidazoon ), the specimen known as "Form A" differs from other banffozoans by having a highly sclerotized shell and a posterior section that emerges only from the dorsal portion of the anterior section, instead of from both the dorsal and ventral portions. [5]

Taxonomy

Banffozoans have been argued to be more closely related to protostomes than to deuterostomes, even if the Vetulicolida are deuterostomes. [10] Banffia shows no sign of gill openings, and potential gill openings in Heteromorphus or Skeemella are unclear. However, a burrowing lifestyle could explain the lack of visible openings. [11]

The possible presence of gut diverticula in Banffia constricta would suggest a protostome affinity, but the same researcher proposed that these features could represent a circulatory system instead. [12]

Other arguments center around possible arthropod affinity for Skeemella, although if Skeemella is not a banffozoan, they would no longer apply. No mouth has been preserved in any Skeemella specimens, preventing observations of its morphology. The extremely long posterior section has been considered arthropod-like, especially the bifid (forked) terminal segment. However, the length of the posterior section would also be unusually long for an arthropod thorax, and reconstruction as an arthropod would require unlikely breakage in the supposed valve. The forked terminal segment remains more reminiscent of arthropods than vetulicolians. [4]

Despite these debates, most workers continue to consider Banffozoa a class within Vetulicolia, [3] [13] or otherwise closely associated with the Vetulicolida. [14]

An intriguing possibility for protostome affinities is suggested by the Centroneuralia hypothesis, which features a paraphyletic Deuterostomia with chordates as the sister-group to protostomes. If proven true, pharyngeal slits would no longer require a deuterostome placement and vetulicolians could prove to be stem protostomes that lost the post-anal tail. In such a scenario, Banffozoa could be a more derived stem protostome group than Vetulicolida. [15]

Cladograms

A 2024 study has found the Banffozoa to form the earliest part of the paraphyletic stem-chordate evolutionary grade, as shown in this simplified cladogram: [14]

Chordata
(total group)
"Banffozoa"

An earlier study in 2014 placed vetulicolians as the sister-group of tunicates, but was unable to resolve any relationships among vetulicolians as a group: [16]

Preference for Banffozoa over Heteromorphida

Banffozoa was published in a journal issue dated June 2005, [17] but with a formal in-print date of 2006. [18] Heteromorphida was published with a date of October 2005. [19] When expanding Banffozoa to encompass Chinese genera such as Heteromorphus, Aldridge et al. added a post-proof note suggesting that Heteromorphida, of which they had been unaware, appeared to take precedence over Banffozoa based on Banffozoa's formal date of 2006. [20] However, the principle of priority does not govern taxonomic ranks above the family level. [21]

While at least one later source has given precedence to Heteromorphida, [3] several sources have preferred Banffozoa. At least one such source mentions Heteromorphida as a synonym, [1] but most do not. [14] [22] [13] [23]

Related Research Articles

<span class="mw-page-title-main">Vetulicolia</span> Extinct Cambrian group of animals

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 some continue to favor a more crownward placement as a sister group to the Tunicata. It was initially erected as a monophyletic clade with the rank of phylum in 2001, with subsequent work supporting its monophyly. However, more recent research suggests that vetulicolians may be paraphyletic and form a basal evolutionary grade of stem chordates.

<span class="mw-page-title-main">Maotianshan Shales</span> Series of Early Cambrian deposits in the Chiungchussu Formation in China

The Maotianshan Shales (帽天山页岩) are a series of Early Cambrian sedimentary deposits in the Chiungchussu Formation, famous for their Konservat Lagerstätten, deposits known for the exceptional preservation of fossilized organisms or traces. The Maotianshan Shales form one of some forty Cambrian fossil locations worldwide exhibiting exquisite preservation of rarely preserved, non-mineralized soft tissue, comparable to the fossils of the Burgess Shale of British Columbia, Canada. They take their name from Maotianshan Hill in Chengjiang County, Yunnan Province, China.

<i>Yunnanozoon</i> Cambrian fossil chordate

Yunnanozoon lividum is an extinct species of bilaterian animal from the Lower Cambrian Chengjiang biota of Yunnan province, China. Its affinities have been long the subject of controversy.

<i>Vetulicola</i> Fossil genus of marine animal

Vetulicola is an extinct genus of marine animal discovered from the Cambrian of China. It is the eponymous member of the enigmatic phylum Vetulicolia, which is of uncertain affinities but may belong to the deuterostomes. 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.

<i>Pomatrum</i> Cambrian age animal

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, Lower Cambrian, Haikou, (Kunming), about 50 km west of Chengjiang, China.

<i>Banffia</i> Extinct genus of Cambrian organisms

Banffia is a genus of animals described from Middle Cambrian fossils. The genus commemorates Banff, Alberta, near where the first fossil specimens were discovered. Its placement in higher taxa is controversial, with it mostly being considered to be a member of the enigmatic phylum Vetulicolia.

<span class="mw-page-title-main">Vetulicolidae</span> Extinct Cambrian family of vetulicolian animals

Vetulicolidae is a vetulicolian family from the Cambrian Stage 3 Maotianshan Shale and Sirius Passet Lagerstätte that consists of Vetulicola, Beidazoon, and Ooedigera. It is distinguished from the Didazoonidae by a harder body wall and the lack of an oral disc.

<span class="mw-page-title-main">Didazoonidae</span> Extinct Cambrian family of vetulicolid animals

Didazoonidae is a vetulicolian family within the order Vetulicolata. It is charaterized by a relatively thin-walled, non-biomineralized body and a large, round anterior opening surrounded by an oral disc. It may be paraphyletic, even if the phylum Vetulicolia is monophyletic.

<i>Yuyuanozoon</i> Cambrian genus of animals

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

<i>Haikoucaris</i> Extinct genus of arthropods

Haikoucaris is a genus of megacheiran arthropod that contains the single species Haikoucaris ercaiensis. It was discovered in the Cambrian Chengjiang biota of China.

<i>Vetulicola cuneata</i> Extinct species of animal

Vetulicola cuneata is a species of extinct marine animal from the Early Cambrian Chengjiang biota of China. It was described by Hou Xian-guang in 1987 from the Lower Cambrian Chiungchussu Formation, and became the first animal under an eponymous phylum Vetulicolia.

<i>Ooedigera</i> Ovoid Cambrian animal with a bulbous tail

Ooedigera peeli is an extinct vetulicolian from the Early Cambrian of North Greenland. The front body was flattened horizontally, oval-shaped, likely bearing a reticulated or anastomosing pattern, and had 5 evenly-spaced gill pouches along the midline. The tail was also bulbous and flattened horizontally, but was divided into 7 plates connected by flexible membranes, allowing movement. Ooedigera likely swam by moving side-to-side like a fish. It may have lived in an oxygen minimum zone alongside several predators in an ecosystem based on chemosynthetic microbial mats, and was possibly a deposit or filter feeder living near the seafloor.

<i>Skeemella</i> Extinct genus of bilaterians

Skeemella is a genus of elongate animal from the Middle Cambrian Wheeler Shale and Marjum lagerstätte of Utah. It has been classified with the banffozoan vetulicolians.

<i>Cotyledion</i> Extinct genus of filter-feeders

Cotyledion tylodes is an extinct, stalked filter-feeder known from the Chengjiang lagerstatten. The living animal reached a couple of centimetres in height, and bore a loose scleritome of ovoid sclerites. Its interpretation has been controversial, but it is currently thought to be a member of the Entoprocta stem group.

<i>Vetulicola rectangulata</i> Extinct animal from Cambrian of the Chengjiang biota of China

Vetulicola rectangulata is a species of extinct animal from the Early Cambrian of the Chengjiang biota of China. Regarded as a deuterostome, it has characteristic rectangular anterior body on which the posterior tail region is attached. It was described by Luo Huilin and Hu Shi-xue in 1999.

<i>Nesonektris</i> Extinct genus of Cambrian Era Chordate

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.

<i>Beidazoon</i> Extinct species of Cambrian organism

Beidazoon venustum is a marine deuterostome from the group Vetulicolia. It originates from the lower Cambrian Chengjiang biota of Yunnan Province, China, and was discovered in 2005. It is known as the smallest described vetulicolian, and for its surface being covered in many small nodes.

<span class="mw-page-title-main">Banffiidae</span> Extinct Cambrian family of animals

Banfiidae is a family of extinct banffozoan animals from North America and China. The family name is sometimes spelt Banffidae. It includes Banffia, Heteromorphus, and possibly Skeemella. The family may be paraphyletic. The family may be paraphyletic. A Heteromorphus-like dwarf "Form A" is allied with this group at the class level, but has not been formally described or assigned to this family.

<i>Shenzianyuloma</i> Species of vetulicolian invertebrate

Shenzianyuloma is an extinct genus of vetulicolian represented by a single species, Shenzianyuloma yunnanense, from the Maotianshan Shale during Stage 3 of the Cambrian period. It is notable for having a compact body shape akin to that of an angelfish. It's exact phylogenetic position is unclear, and it was not included in a 2024 phylogenetic analysis of vetulicolians.

<i>Heteromorphus</i> Extinct genus of Cambrian organisms

Heteromorphus is an extinct genus of banffiid from the lower Cambrian Chengjiang lagerstatte. It contains one broadly accepted species, Heteromorphus confusus, as well as a proposed junior synonym, Heteromorphus longicaudatus that may prove to be a separate species as additional specimens are examined. A much smaller species labeled "Form A" is allied with Heteromorphus at the class level but has not been formally described or assigned to Heteromorphus itself.

References

  1. 1 2 Vinther, Smith & Harper 2011 , p. 711
  2. 1 2 3 Aldridge et al. 2007 , pp. 147–148
  3. 1 2 3 Li et al. 2018 , pp. 1083–1084
  4. 1 2 Kimmig, Leibach & Lieberman 2020 , pp. 219–220
  5. 1 2 3 Shu 2005 , p. 2349
  6. 1 2 Aldridge et al. 2007 , pp. 147–150
  7. ↑ Hou et al. 2017 , p. 272
  8. ↑ Aldridge et al. 2007 , pp. 152
  9. ↑ Briggs et al. 2005 , p. 682
  10. ↑ Caron 2005 , p. 95
  11. ↑ Conway Morris et al. 2015 , p. 5
  12. ↑ Caron 2005 , p. 109
  13. 1 2 Kimmig, Leibach & Lieberman 2020 , p. 216
  14. 1 2 3 Mussini et al. 2024 , pp. 6–7(Note: The cladogram is simplified using the definition of Vetulicolidae from Li et al. 2018, cited elsewhere on this page)
  15. ↑ Kapli et al. 2021 , p. 6
  16. ↑ García-Bellido et al. 2014 , p. 9
  17. ↑ "Banffia constricta, a putative vetulicolid from the Middle Cambrian Burgess Shale | Cambridge Core". Cambridge Core. July 26, 2007. Retrieved December 10, 2024."Earth and Environmental Science Transactions of The Royal Society of Edinburgh , Volume 96 , Issue 2 , June 2005 , pp. 95 - 111"
  18. ↑ Caron 2005 , p. 95, header text"Transactions of the Royal Society of Edinburgh: Earth Sciences,96, 95–111, 2006 (for 2005)"
  19. ↑ "On the Phylum Vetulicolia | Science Bulletin". Springer Nature Link. Retrieved December 10, 2024."On the Phylum Vetulicolia | Articles Published: October 2005"
  20. ↑ Aldridge et al. 2007 , p. 168
  21. ↑ ICZN 1999 (International Code of Zoological Nomenclature, 1999 Ed.).
  22. ↑ Conway Morris et al. 2015 , p. 3
  23. ↑ "†class Banffozoa Caron 2006". The Paleobiology Database.

Works cited

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