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Proconodontida

Not to be confused with Protoconodontida, Paraconodontida, or Protopanderodontida.

Proconodontida is an order of conodonts which originated in the late Cambrian (Furongian) and persisted partly through the Ordovician.[1] The ancestral proconodont, Proconodontus, was one of the earliest euconodonts ("true conodonts") to appear. Proconodonts are often equated with the broader group Cavidonti, which occupies one side of a basal division in the evolution of early euconodonts in the Cambrian. All other euconodonts occupy Conodonti, the other side of the Cambrian split.[1]

Proconodontida
Temporal range: Furongian – Ordovician Possible descendant taxon Belodellida survives to the Devonian or Permian
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: †Conodonta
Subclass: †Cavidonti
Order: †Proconodontida
Sweet, 1988
Synonyms
  • Cordylodontacea Lindström, 1970
  • Proconodontacea Miller, 1981
  • Fryxellodontoacea Miller, 1981

Proconodontida may be ancestral to another order, Belodellida.[1] Belodellids originate in the Ordovician and survive up to the Devonian[1] or even the Permian (if Caenodontus qualifies as a member of the order).[2]

Description

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Cavidonts were simple conodonts, tending to maintain smooth and thin-walled elements with a hyaline structure. They were often coniform (horn- or tooth-shaped) with a semi-symmetrical or elliptical cross-section.[1][3] The basal cavity was deeper than in early members of their sister taxon Conodonti. The apparatus is quinquimembrate at most (with five or fewer different element forms) and P elements are infrequent.[1]

Lateral keels and subtle lines of serrations are frequently found in the hook-shaped elements of bellodelids, while other proconodonts rarely deviate from one or more basic conical structures.[1] The Ordovician proconodont Fryxellodontus is occasionally considered ancestral to Polonodus and pygodontids, which had more unusual elements covered with ridges, nodes, and denticles.[4][1]

Taxonomy

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Cavidonti and its interrelationships were first established by Sweet (1988).[1] Many families and larger groups are paraphyletic and not yet evaluated by cladistic analyses.[5]

A different taxonomic arrangement, proposed by Dzik (1991), does not use Cavidonti as a grouping. Instead, it classifies proconodontids (families Proconodontidae, Cordylodontidae, and Fryxellodontidae) as members of the order Panderodontida and the superfamily Cordylodontacea. The order Belodellida is broken up and removed from their status as descendants of proconodontids. Bellodellidae and the component taxa of Dapsilodontidae (Besselodus and Dapsilodus) were moved into the superfamily Panderodontacea, closer to Panderodontidae and Strachanognathidae. Ansellidae is given a more distant placement among the Prioniodontida.[9] A 1994 reevaluation of Panderodus argued that Belodellidae may have close affinities to Panderodontida, while Besselodus and Dapsilodus are best classified within the order Protopanderodontida.[10]

References

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  1. ^ a b c d e f g h i j k l m n o p Sweet, W. C. (1988). The Conodonta: morphology, taxonomy, paleoecology and evolutionary history of a long-extinct animal phylum. Oxford Monographs on Geology and Geophysics. Vol. 10. pp. 1–211. ISBN 978-0-19-504352-5.
  2. ^ Nestell, Merlynd K.; Wardlaw, Bruce R. (2015). "An apparatus reconstruction of the conodont Caenodontus serrulatus Behnken 1975". Micropaleontology. 61 (4–5): 293–300. doi:10.47894/mpal.61.4.03. ISSN 0026-2803.
  3. ^ Jain, Sreepat (2020), "Conodonts", Fundamentals of Invertebrate Palaeontology, Springer Geology, New Delhi: Springer India, pp. 93–115, doi:10.1007/978-81-322-3962-8_5, ISBN 978-81-322-3960-4, retrieved 2024-03-27
  4. ^ Bergström, Stig M. (1983-12-15), "Biogeography, evolutionary relationships, and biostratigraphic significance of Ordovician platform conodonts", in Martinsson, Anders; Bengtson, Stefan (eds.), Taxonomy, ecology and identity of conodonts, Fossils and Strata, vol. 15, Universitetsforlaget, pp. 35–58, doi:10.18261/8200067378-1983-05, ISBN 978-82-00-06737-5, retrieved 2024-03-27
  5. ^ Sweet, W. C.; Donoghue, P. C. J. (2001). "Conodonts: Past, Present, Future" (PDF). Journal of Paleontology. 75 (6): 1174–1184. doi:10.1666/0022-3360(2001)075<1174:CPPF>2.0.CO;2. S2CID 53395896.
  6. ^ a b Lindström, Maurits (1970). "A suprageneric taxonomy of the conodonts". Lethaia. 3 (4): 427–445. doi:10.1111/j.1502-3931.1970.tb00834.x. ISSN 0024-1164.
  7. ^ Ferretti, Annalisa; Corradini, Carlo; Fakir, Sana; Malferrari, Daniele; Medici, Luca (2023). "To be or not to be a conodont. The controversial story of Pseudooneotodus and Eurytholia". Marine Micropaleontology. 182: 102258. doi:10.1016/j.marmicro.2023.102258. hdl:11380/1329541.
  8. ^ Clark, David L. (1981). "Chapter 3: Systematic Descriptions". In Moore, Raymond C.; Robison, R.A. (eds.). Part W, Miscellanea, Supplement 2: Conodonta. Treatise on Invertebrate Paleontology. Boulder, Colorado; Lawrence, Kansas: Geological Society of America; University of Kansas. pp. 111–180. ISBN 0-8137-3028-7.
  9. ^ Dzik, Jerzy (1991). "Evolution of oral apparatuses in the conodont chordates" (PDF). Acta Palaeontologica Polonica. 36 (3): 265–323.
  10. ^ Samson, Ivan J.; Armstrong, Howard A.; Smith, M. Paul (1994). "The apparatus architecture of Panderodus and its implications for coniform conodont classification" (PDF). Palaeontology. 37 (4): 781–799.
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