Psammodus

Psammodus
Temporal range: Latest Devonian–Mississippian
Reconstructed tooth-plates of Psammodus (formerly classified as the genus Archaeobatis)
Isolated tooth-plate of Psammodus
Scientific classification Edit this classification
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Subclass: Holocephali
Order: †Psammodontiformes
Obruchev, 1953
Family: †Psammodontidae
de Koninck, 1878
Genus: †Psammodus
Agassiz, 1838
Type species
Psammodus rugosus
Agassiz, 1838
Synonyms
  • Archaeobatis Newberry, 1878
  • Astrabatis Davis, 1884
  • Homalodus Davis, 1883

Psammodus is an extinct genus of cartilaginous fish known from the Late Devonian to the Early Carboniferous period.[1] It is the only member of the family Psammodontidae and the order Psammodontiformes, although other genera have been classified in these groups in the past. Psammodus were durophagous carnivores.[2]

Research history

Fossils of the genus Psammodus were first described and named by naturalist Louis Agassiz.[3][1]

Description

Psammodus are known primarily from their plate-like teeth. These teeth are broad and flat, and often appear rectangular or triangular. In life the teeth were tightly packed together in the jaws.[4]

A partial skull of Psammodus is known, which has not been described in detail.[1][5]

Classification

Psammodus is the type genus of the family Psammodontidae and order Psammodontiformes.[6] The name Psammodontidae was first coined by paleontologist Laurent-Guillaume de Koninck in 1878 to include Psammodus and the genus Helodus,[1][7] although the family "Psammodonten" was already named by biologist Christian Heinrich Pander in 1856. Because "Psammodonten" is not latinized it is considered an invalid taxon, and Psammodontidae is the name used for the family.[6] In a 1953 publication, Dmitry Obruchev established the monotypic order Psammodontiformes to include Psammodontidae, as he considered it preferable to use order-level taxonomy for extinct cartilaginous fish groups. Obruchev himself later sank Psammodontidae into the order Bradyodonti in 1964,[4] but other authors have continued to separate various "bradyodonts", including the psammodonts, into their own orders.[6][8]

Additional genera were named and considered relatives of Psammodus by later authors, such as the junior synonyms Archaeobatis,[4] Homalodus and Astrabodus. Of these genera, Lagarodus is still considered valid and was traditionally classified as part of Psammodontidae and Psammodontiformes,[1] but it has been reclassified as a member of the family Lagarodontidae, and is no longer classified as part of a specific order.[9][10]

Paleobiology

Psammodus tooth plates are adapted for durophagy, and members of the genus likely had similar diets to living chimaeras consisting of small benthic invertebrates with hard shells and occasional small fish. Food was likely ground between the upper and lower tooth plates, rather than being crushed.[4]

References

  1. ^ a b c d e Stahl, Barbara J. (1999). Handbook of Paleoichthyology: Chondrichthyes III, Holocephali. Vol. 4. München: Pfeil. pp. 85–90. ISBN 978-3-931516-63-5.
  2. ^ "PBDB Taxon". The Paleobiology Database. Retrieved 26 August 2024.
  3. ^ Agassiz, Louis; Agassiz, Louis (1833). Recherches sur les poissons fossiles ... Neuchatel: Petitpierre. doi:10.5962/bhl.title.4275.
  4. ^ a b c d Obruchev, Dmitry (1967). Fundamentals of paleontology. A manual for paleontologists and geologists of the USSR. Vol. 11. Jerusalem: Israel Program for Scientific Translations. pp. 353–419.
  5. ^ Ahlberg, Per Erik; Coates, Michael I. (1997). "There's a ratfish in our cellar!". Geology Today. 13 (1): 20–23. doi:10.1046/j.1365-2451.1997.00013.x. ISSN 0266-6979.
  6. ^ a b c Van der Laan, Richard (2018-10-11). "Family-group names of fossil fishes". European Journal of Taxonomy (466): 38. doi:10.5852/ejt.2018.466. ISSN 2118-9773.
  7. ^ de Koninck, Laurent-Guillaume (1878). "Faune du calcaire carbonifère de la Belgique. Première partie, poissons et genre nautile". Annales du Musée royal d'histoire naturelle de Belgique. 2: 58 – via Biodiversity Heritage Library.
  8. ^ Nelson, Joseph S.; Grande, Terry C.; Wilson, Mark V. H. (2016). Fishes of the World (5th ed.). Wiley. doi:10.1002/9781119174844. ISBN 978-1-118-34233-6.
  9. ^ Cuny, Gilles; Kristensen, Jakob Bruun; Stemmerik, Lars (2015-12-18). "First record of Lagarodus (Chondrichthyes: Euchondrocephali) from the Carboniferous of Svalbard, Arctic Norway". Norwegian Journal of Geology. doi:10.17850/njg96-1-01.
  10. ^ Lebedev, Oleg (2008). "Systematics and dental system reconstruction of the durophagous chondrichthyan Lagarodus JAEKEL, 1898". Acta Geologica Polonica. 58 (2).

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