Synechodontiformes

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Synechodontiformes
Temporal range: Early Permian-Paleogene 290.1–37.2  Ma [1]
Synechodus.png
Fossil of Synechodus ungeri from the Late Jurassic of Germany
Rya Formation shark teeth - Synechodus - S. occultidens (A-G) & S. enniskilleni (H-J).jpg
Fossil teeth of Palidiplospinax occultidens (top) and P. enniskilleni
Scientific classification OOjs UI icon edit-ltr.svg
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Subclass: Elasmobranchii
Order: Synechodontiformes
Duffin & Ward, 1993 [2]
Families

See text

Synechodontiformes is an extinct order of prehistoric shark-like cartilaginous fish, known from the Permian to the Paleogene. They are considered to be members of Neoselachii, the group that contains modern sharks and rays.

Contents

Their placement in the group is uncertain, some authors have considered them to be members of the modern shark group Galeomorphi, while others have considered them to represent a stem-group to modern sharks, [3] [4] with some suggesting that they are basal to the last common ancestor of modern sharks and rays. [5] There is also disagreement about the relationships between Triassic and earlier members of the group, only known from isolated teeth, and those from the Jurassic onwards, with the similarity between the two groups possibly being superficial. [6]

The main shared characters of the group relate to teeth anatomy. The teeth roots have a distinctive pseudopolyaulacorhize vascularisation pattern, with a depression on the tooth root to where the nutritive grooves are confined. [4] While Klug (2010) recovered the group as monophyletic, [4] the monophyly of the group has been doubted by other authors, who suggest that they represent a paraphyletic group, [5] and that the tooth vascularisation patterns do not clearly demonstrate that these sharks are more closely related to each other than to other sharks. [7] One family is unambiguously placed in the order, Palaeospinacidae. The families Orthacodontidae, Paraorthacodontidae and Pseudonotidanidae, often considered members of the group, have been alternatively considered as members of the modern shark order Hexanchiformes rather than as members of Synechodontiformes. [7] [8]

The oldest known synechodontiform remains are teeth of Synechodus antiquus from the early Permian (Cisuralian) of the Ural Mountains. [9] However, other authors have considered the attribution to the teeth to Synechodus to be questionable. [6]

Taxonomy

Disputed members

These members were classified in the Synechodontiformes by Klug (2010), but are classified by some other authors as Hexanchiformes: [11] [19] [8] [7]

References

  1. "†order Synechodontiformes Duffin and Ward 1993 (elasmobranch)". Fossilworks.
  2. C. J. Duffin and D. J. Ward. 1993. The Early Jurassic Palaeospinacid sharks of Lyme Regis, southern England. Belgian Geological Survey, Professional Papers, Elasmobranches et Stratigraphie 264:53-102
  3. Bazzi, Mohamad; Campione, Nicolás E.; Ahlberg, Per E.; Blom, Henning; Kear, Benjamin P. (2021-08-10). Quental, Tiago Bosisio (ed.). "Tooth morphology elucidates shark evolution across the end-Cretaceous mass extinction". PLOS Biology. 19 (8): e3001108. doi: 10.1371/journal.pbio.3001108 . ISSN   1545-7885. PMC   8354442 . PMID   34375335.
  4. 1 2 3 Klug, Stefanie (2010). "Monophyly, phylogeny and systematic position of the †Synechodontiformes (Chondrichthyes, Neoselachii)" . Zoologica Scripta. 39 (1): 37–49. doi:10.1111/j.1463-6409.2009.00399.x. ISSN   1463-6409. S2CID   85265779.
  5. 1 2 3 Maisey, J. G. (April 2012). "What is an 'elasmobranch'? The impact of palaeontology in understanding elasmobranch phylogeny and evolution" . Journal of Fish Biology. 80 (5): 918–951. Bibcode:2012JFBio..80..918M. doi:10.1111/j.1095-8649.2012.03245.x. ISSN   0022-1112. PMID   22497368.
  6. 1 2 Rees, Jan; Campbell, Hamish J.; Simes, John E. (2023-05-21). "The first Triassic elasmobranch teeth from the Southern Hemisphere (Canterbury, New Zealand)" . New Zealand Journal of Geology and Geophysics: 1–8. doi:10.1080/00288306.2023.2214369. ISSN   0028-8306. S2CID   258840273.
  7. 1 2 3 4 Villalobos-Segura, Eduardo; Amadori, Manuel; Stumpf, Sebastian; Jambura, Patrick L.; Begat, Arnaud; Lopez-Romero, Faviel A.; Schweigert, Günter; Maxwell, Erin E.; Kriwet, Jürgen (2025-12-31). "Articulated specimens provide new insights into the iconic Mesozoic shark genus Sphenodus". Journal of Systematic Palaeontology. 23 (1). doi: 10.1080/14772019.2025.2507014 . ISSN   1477-2019.
  8. 1 2 3 4 Thies, Detlef; Vespermann, Jürgen; Solcher, Jutta (2014-12-23). "Two new neoselachian sharks (Elasmobranchii, Neoselachii, Synechodontiformes) from the Rhaetian (Late Triassic) of Europe" . Palaeontographica Abteilung A. 303 (4–6): 137–167. doi:10.1127/pala/303/2014/137. ISSN   0375-0442.
  9. Ivanov, Alexander (2005-08-30). "Early Permian chondrichthyans of the Middle and South Urals" (PDF). Revista Brasileira de Paleontologia. 8 (2): 127–138. doi:10.4072/rbp.2005.2.05.
  10. 1 2 Guinot, Guillaume; Cappetta, Henri; Adnet, Sylvain (March 2014). "A rare elasmobranch assemblage from the Valanginian (Lower Cretaceous) of southern France" . Cretaceous Research. 48: 54–84. Bibcode:2014CrRes..48...54G. doi:10.1016/j.cretres.2013.11.014.
  11. 1 2 "Bibliography Database | Shark-References". shark-references.com. Retrieved 2023-12-02.
  12. 1 2 Klug, Stefanie; Kriwet, Jürgen (May 2008). "A new basal galeomorph shark (Synechodontiformes, Neoselachii) from the Early Jurassic of Europe" . Naturwissenschaften. 95 (5): 443–448. Bibcode:2008NW.....95..443K. doi:10.1007/s00114-007-0341-0. ISSN   0028-1042. PMID   18196213. S2CID   8460659.
  13. Batchelor, Trevor J.; Duffin, Christopher J. (August 2020). "First description of sharks' teeth from the Ferruginous Sands Formation (Aptian, Early Cretaceous) of the Isle of Wight" . Proceedings of the Geologists' Association. 131 (3–4): 353–359. Bibcode:2020PrGA..131..353B. doi:10.1016/j.pgeola.2019.06.004. S2CID   199107658.
  14. "Mucrovenator".
  15. 1 2 Koot, Martha B.; Cuny, Gilles; Orchard, Michael J.; Richoz, Sylvain; Hart, Malcolm B.; Twitchett, Richard J. (2015-10-03). "New hybodontiform and neoselachian sharks from the Lower Triassic of Oman" . Journal of Systematic Palaeontology. 13 (10): 891–917. Bibcode:2015JSPal..13..891K. doi:10.1080/14772019.2014.963179. ISSN   1477-2019. S2CID   129741739.
  16. 1 2 Li, Jiachun; Sun, Zuoyu; Cuny, Gilles; Jiang, Dayong (August 2023). "Early Triassic chondrichthyans from the Zuodeng Section, Guangxi Province, South China: Palaeobiological and palaeobiogeographical implications". Palaeogeography, Palaeoclimatology, Palaeoecology. 624: 111635. doi:10.1016/j.palaeo.2023.111635.
  17. Li, Jiachun; Sun, Zuoyu; Cuny, Gilles; Ji, Cheng; Jiang, Dayong; Zhou, Min (January 2022). Cavin, Lionel (ed.). "An unusual shark assemblage from the Ladinian–Carnian interval of South China" . Papers in Palaeontology. 8 (1). doi:10.1002/spp2.1404. ISSN   2056-2799.
  18. Plamen S. Andreev & Gilles Cuny (2012). "New Triassic stem selachimorphs (Chondrichthyes, Elasmobranchii) and their bearing on the evolution of dental enameloid in Neoselachii". Journal of Vertebrate Paleontology. 32 (2): 255–266. Bibcode:2012JVPal..32..255A. doi:10.1080/02724634.2012.644646. S2CID   84162775.
  19. Klug, Stefanie (January 2010). "Monophyly, phylogeny and systematic position of the †Synechodontiformes (Chondrichthyes, Neoselachii)" . Zoologica Scripta. 39 (1): 37–49. doi:10.1111/j.1463-6409.2009.00399.x. ISSN   0300-3256. S2CID   85265779.
  20. Kanno, Shiori; Nakajima, Yasuhisa; Hikida, Yoshinori; Sato, Tamaki (2017-04-01). "Sphenodus (Chondrichthyes, Neoselachii) from the Upper Cretaceous in Nakagawa Town, Hokkaido, Japan" . Paleontological Research. 21 (2): 122. doi:10.2517/2016PR009. ISSN   1342-8144. S2CID   133054888.
  21. 1 2 Klug, Stefanie; Kriwet, Jürgen (September 2010). "A new Late Jurassic species of the rare synechodontiform shark, Welcommia (Chondrichthyes, Neoselachii)" . Paläontologische Zeitschrift. 84 (3): 413–419. Bibcode:2010PalZ...84..413K. doi:10.1007/s12542-010-0058-9. ISSN   0031-0220. S2CID   129213049.