Saurichthys

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Saurichthys
Temporal range: Triassic
~251.902–201.3 Ma
Saurichthys.JPG
Saurichthys fossil
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: †Saurichthyiformes
Family: †Saurichthyidae
Genus: †Saurichthys
Agassiz, 1834
Type species
†Saurichthys apicalis
Agassiz, 1834
Species
  • More than 50 species (see list below)
Synonyms
  • Belonorhynchus Bronn 1858[1]
  • Brevisaurichthys Beltan 1972[2]
  • Giffonus Costa 1862[1]
  • Gymnosaurichthys Berg 1940
  • Ichthyorhynchus Bellotti 1857[1]
  • Stylorhynchus Martin 1873 non-Lesson1847 non-Stein 1848
  • Systolichthys Beltan 1972[2]
Saurichthys curionii fossil from the Middle Triassic of Monte San Giorgio, Switzerland
Early Triassic and Middle Triassic marine predators:[3] 3. Saurichthys
Saurichthys model at the Museum of Man and Nature, Munich
Saurichthys seefeldensis attacking Preondactylus, based on an outdated interpretation of a gastric pellet now believed to contain remains of Langobardisaurus

Saurichthys (meaning: 'lizard fish') is an extinct genus of predatory ray-finned fish from the Triassic period. It is the name giving genus of the family Saurichthyidae (Changhsingian-Middle Jurassic). This family also includes the Permian Eosaurichthys (China) and the Jurassic Saurorhynchus (= Acidorhynchus)[4] from Europe and North America.

Fossils of Saurichthys have been found on all continents except South America and Antarctica.[5] It inhabited both marine and freshwater environments. The oldest fossils of Saurichthys were recovered from the Wordie Creek Formation in East Greenland and are (Induan, Early Triassic) in age.[6]

Over 50 species of Saurichthys have been described (see list below). The species differ in size and show variability in their skeletal features. The latter can potentially be ascribed to changes in major developmental genes.[7] The use of subgenera (Eosaurichthys, , , Saurorhynchus, Sinosaurichthys) in the literature reflects differences in morphology between species groups.[8] Several species that were described predominantly in the 19th century are based on fragmentary fossils (often isolated teeth). These are mostly considered invalid species by modern taxonomic standards.

Louis Agassiz, who described the type species of Saurichthys in 1834, named it the "lizard fish" because of skeletal features that he thought were intermediate to reptiles and fishes.

Their closest modern-day relatives include the sturgeons, paddlefish, and the bowfins.[9] However, a recent study investigated the inner skull anatomy of Saurichthys and questioned a close affiliation with Acipenseriformes and Amiiformes.[10]

Appearance[]

Saurichthys was an elongate, streamlined fish, commonly about 0.6 metres (2.0 ft) to 1 metre (3.3 ft) long. Some species were only a few decimetres long (e.g. Saurichthys minimahleri), while others could grow up to about 1.5 metres (4.9 ft) in length (specimen from the Middle Triassic of Turkey).[11][12]

Species of Saurichthys looked superficially similar to the modern pike (note that the pike is a teleost and only distantly related with Saurichthys). Its dorsal and anal fins were placed opposite each other well back on the body, and the tail was symmetrical. These features would have made it a powerful swimmer, and it is presumed to have hunted in a similar way to the pike, attacking from an ambush at high speed. Its jaws were extremely long, making up a third of the total body length, and ended in a sharp, beak-like tip.[13] Two to six longitudinal scale rows are developed, with small scales in between in some species. The caudal fin is abbreviate-diphycercal.

The axial skeleton consists of ossified neural and haemal arches. Haemal arches may develop spines. The neural arches often show spines as well as other projections interpreted as and postzygapophyses. Ossified centra are missing. The axial skeleton shows regionalization, meaning that there are differences in bone morphology between segments of the axial skeleton. Some species show dedifferentiation of the axial skeleton.[14]

Early Triassic species of Saurichthys[15] differ from later species most prominently in their more elongate postorbital portion of the skull (part of the skull behind the eyes) and their generally denser scale cover.

Ecology[]

Large species of Saurichthys were apex predators among Triassic ray-finned fish, together with the marine Birgeria (Birgeriidae).

Saurichthys is classically interpreted as an ambush predator. It first approached its prey and then attacked it by quick, sudden darts.[16] Some species may have lived as subsurface cruisers (Sinosaurichthys).

Specimens showing half-swallowed conspecific individuals suggest that cannibalism was relatively common in Saurichthys.[17] Fossil evidence, in the form of a bolus (ball-shaped mass) of bones in the same strata, indicates that Saurichthys attacked marine reptiles such as the tanystropheid Langobardisaurus, or possibly scavenged their corpses.[citation needed]

A study on the gastrointestinal tract of Saurichthys found similarities with present-day sharks and rays, in particular the many windings in the spiral valve. The many windings increased the surface area for digestion, which is sure to have provided the fish with more energy. It indicates that Saurichthys had an energy-laden lifestyle.[18]

Reproduction[]

Saurichthys curionii with embryos

Fossils of gravid females provide evidence for (ovo-)viviparity in Saurichthys[19] and the oldest known example for viviparity in ray-finned fishes.

Internal fertilisation is also evidenced by specialized pelvic fin rays () or ventral scales (gonopodium; , ) that are interpreted as copulatory organs of males.[20]

Species[]

Lower jaw of Saurichthys apicalis
Saurichthys costasquamosus fossil
Saurichthys macrocephalus fossil
Fossil of Saurichthys sp.
Fossil of Saurichthys sp.
  • †Saurichthys ( Tintori 2013)
    • †Saurichthys (Costasaurichthys) costasquamosus Rieppel 1985
    • †Saurichthys (Costasaurichthys) paucitrichus Rieppel 1992
  • †Saurichthys (Eosaurichthys Liu and Wei 1988)
    • †Saurichthys (Eosaurichthys) chaoi (Liu and Wei 1988)
    • †Saurichthys (Eosaurichthys) madagascariensis Piveteau 1945[21]
  • †Saurichthys ( Tintori 2013)
    • †Saurichthys (Lepidosaurichthys) dayi (Raymond 1925)
    • †Saurichthys (Lepidosaurichthys) elongatus Stensiö 1925
    • †Saurichthys (Lepidosaurichthys) ornatus Stensiö 1925
    • †Saurichthys (Lepidosaurichthys) toxolepis Mutter et al. 2008
    • †Saurichthys (Lepidosaurichthys) wimani (Woodward 1912)[22]
  • †Saurichthys (Saurorhynchus Agassiz 1844)
    • †Saurichthys (Saurorhynchus) calcaratus Griffith 1977[23]
    • †Saurichthys (Saurorhynchus) deperditus (Costa 1862)
    • †Saurichthys (Saurorhynchus) striolatus Bronn 1858[24]
    • †Saurorhynchus acutus (Agassiz 1844)
    • †Saurorhynchus anningae Maxwell & Stumpf 2017
    • †Saurorhynchus brevirostris (Woodward 1895)
    • †Saurorhynchus hauffi Maxwell & Stumpf 2017
  • †Saurichthys (Sinosaurichthys Wu et al. 2009)
    • †Saurichthys (Sinosaurichthys) longipectoralis Wu et al. 2009
    • †Saurichthys (Sinosaurichthys) longimedialis Wu et al. 2009
    • †Saurichthys (Sinosaurichthys) minuta Wu et al. 2009
  • † Agassiz 1834 (type species)
  • † Maxwell et al. 2015[25]
  • † (Bellotti 1857)
  • † Firtion 1934
  • † Wu et al. 2009
  • † Maxwell et al. 2016
  • † Minich 1992
  • † Minikh 1982
  • † (Woodward 1890), non-von Quenstedt 1858
  • † (Woodward 1890)
  • † Tintori 2013
  • † Reis 1892
  • † Stensiö 1925
  • † Werneburg et al. 2014
  • † Chou & Liu 1957
  • † Oertle 1928
  • † Eck 1865
  • † Frech 1903
  • † (Deecke 1889)
  • † Tintori et al. 2014
  • † Werneburg et al. 2014
  • † Beltan & Janvier 1978
  • † Minich 1981
  • † Sytchevskaya 1999
  • † Wade 1935
  • † Beltan 1968
  • † Minich 1981
  • † Maxwell et al. 2015[25]
  • † Renesto et al. 2021[26]
  • †Saurichthys seefeldensis Kner 1867
  • † Wu et al. 2018[27]
  • † Lehman 1952
  • † Münster 1839[28]
  • † Minich 1982
  • † Minikh 1992
  • † Minikh 1983
  • † Wu et al. 2015
  • † Zhang, Zhou, Lu & Bai 2010

Species based on fragmentary fossils[]

  • † Henry 1876
  • † Winkler 1880
  • † (Betlan 1972)
  • † de Koninck 1863
  • † Plieninger 1844
  • † Agassiz 1834
  • † Agassiz 1844
  • † (Betlan 1972)
  • † Münster 1839
  • † Henry 1876
  • † Henry 1876

Synonyms[]

  • † Agassiz 1844 → †Birgeria acuminata
  • † Agassiz 1844 → †Saurorhynchus acutus
  • † (Woodward 1895) → †Saurorhynchus brevirostris
  • † Münster 1839 → †Birgeria? costata
  • † Stensiö 1925 → †
  • † (Bassani 1886) → †
  • † Schlosser 1918 → †
  • † Agassiz 1844 → †Birgeria mougeoti
  • † Bassani 1886 → †, †, †
  • † (Bassani 1886) → †

References[]

  1. ^ Jump up to: a b c Stensiö, E. (1925). "Triassic Fishes from Spitzebergen, Part II". Kungliga Svenska Vetenskapsakademiens Handlinga. 2: 1–126.
  2. ^ Jump up to: a b Cartanyà, J., ed. (1999). An overview of the Middle Triassic actinopterygians from Alcover, Mont-ral and El Pinetell (Catalonia, Spain). In: G. Arratia and H. P. Schultze (eds.) Mesozoic Fishes 2—Systematics and Fossil Record: Verlag Dr. F. Pfeil, München. pp. 535–551.CS1 maint: location (link)
  3. ^ Scheyer et al. (2014): Early Triassic Marine Biotic Recovery: The Predators' Perspective. PLoS ONE https://doi.org/10.1371/journal.pone.0088987
  4. ^ Kogan, I. (2016): Acidorhynchus Stensiö, 1925 or Saurorhynchus Reis, 1892: how to call the Jurassic saurichthyid? Neues Jahrbuch für Geologie und Paläontologie-Abhandlungen 279:123–126 https://doi.org/10.1127/njgpa/2016/0545
  5. ^ Saurichthys at Fossilworks.org
  6. ^ Kogan, I. (2011): Remains of Saurichthys (Pisces, Actinopterygii) from the Early Triassic Wordie Creek Formation of East Greenland. Bulletin of the Geological Society of Denmark 93:93–100 http://2dgf.dk/xpdf/bull59-93-100.pdf
  7. ^ Schmid and Sánchez-Villagra (2010):Potential genetic bases of morphological evolution in the triassic fish Saurichthys. Journal of Experimental Zoology 314B:519–526. https://doi.org/10.1002/jez.b.21372
  8. ^ Silvio Renesto; Fabio Magnani; Rudolf Stockar (2021). "A new species of Saurichthys (Actinopterygii: Saurichtydae) from the Middle Triassic of Monte San giorgio". Rivista Italiana di Paleontologia e Stratigrafia. 127 (1): 49–71.
  9. ^ Gardiner, B.G.; Schaeffer, B. & Masserie, J.A. (2005). "A review of the lower actinopterygian phylogeny". Zoological Journal of the Linnean Society. 144: 511–525. doi:10.1111/j.1096-3642.2005.00181.x.
  10. ^ Argyriou; et al. (2018). "Internal cranial anatomy of Early Triassic species of †Saurichthys (Actinopterygii: †Saurichthyiformes): implications for the phylogenetic placement of †saurichthyiforms". BMC Evolutionary Biology. 18 (1): 161. doi:10.1186/s12862-018-1264-4. PMC 6211452. PMID 30382811.
  11. ^ Beltan et al. (1979): A new marine fish and placodont reptile fauna of Ladinian age from southwestern Turkey. Neues Jahrbuch für Geologie und Paläontologie, Monatshefte, 1979:257–267.
  12. ^ Romano C., Kogan I., Jenks J., Jerjen I., Brinkmann W. (2012). "Saurichthys and other fossil fishes from the late Smithian (Early Triassic) of Bear Lake County (Idaho, USA), with a discussion of saurichthyid palaeogeography and evolution" (PDF). Bulletin of Geosciences. 87: 543–570. doi:10.3140/bull.geosci.1337.CS1 maint: multiple names: authors list (link)
  13. ^ Palmer, D., ed. (1999). The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals. London: Marshall Editions. p. 36. ISBN 1-84028-152-9.
  14. ^ Maxwell, E.E.; Romano, C. & Wu, F.-X. (2021). "Regional disparity in the axial skeleton of Saurichthyidae and implications for axial regionalization in non‐teleostean actinopterygians". Journal of Zoology. doi:10.1111/jzo.12878.
  15. ^ Kogan , Romano (2016). "Redescription of Saurichthys madagascariensis Piveteau, 1945 (Actinopterygii, Early Triassic), with implications for the early saurichthyid morphotype". Journal of Vertebrate Paleontology. 36 (4): e1151886. doi:10.1080/02724634.2016.1151886. S2CID 87234436.
  16. ^ Kogan; et al. (2015). "The invisible fish: hydrodynamic constraints for predator-prey interaction in fossil fish Saurichthys compared to recent actinopterygians". Biology Open. 4 (12): 1715–1726. doi:10.1242/bio.014720. PMC 4736038. PMID 26603471.
  17. ^ Kogan , Romano (2016). "Redescription of Saurichthys madagascariensis Piveteau, 1945 (Actinopterygii, Early Triassic), with implications for the early saurichthyid morphotype". Journal of Vertebrate Paleontology. 36 (4): e1151886. doi:10.1080/02724634.2016.1151886. S2CID 87234436.
  18. ^ Thodoris Argyriou, Marcus Clauss, Erin E. Maxwell, Heinz Furrer, and Marcelo R. Sánchez-Villagra (2016). Exceptional preservation reveals gastrointestinal anatomy and evolution in early actinopterygian fishes. Scientific Reports 6:18758 . https://doi.org/10.1038/srep18758
  19. ^ Maxwell; et al. (2018). "Re‐evaluation of the ontogeny and reproductive biology of the Triassic fish Saurichthys (Actinopterygii, Saurichthyidae)". Palaeontology. 61: 559–574. doi:10.5061/dryad.vc8h5.
  20. ^ Bürgin T (1990). "Reproduction in Middle Triassic actinopterygians; complex fin structures and evidence of viviparity in fossil fishes". Zoological Journal of the Linnean Society. 100 (4): 379–391. doi:10.1111/j.1096-3642.1990.tb01866.x.
  21. ^ Kogan , Romano (2016). "Redescription of Saurichthys madagascariensis Piveteau, 1945 (Actinopterygii, Early Triassic), with implications for the early saurichthyid morphotype". Journal of Vertebrate Paleontology. 36 (4): e1151886. doi:10.1080/02724634.2016.1151886. S2CID 87234436.
  22. ^ Kogan, I. and Romano, C. (2016): A new postcranium of Saurichthys from the Early Triassic of Spitsbergen. Freiberger Forschungshefte C, Paläontologie, Stratigraphie, Fazies 23:205–221
  23. ^ Ilja Kogan; Andrea Tintori; Martin Licht (2020). "Locomotor function of scales and axial skeleton in Middle-Late Triassic species of Saurichthys (Actinopterygii". Rivista Italiana di Paleontologia e Stratigrafia. 126 (2): 475–498.
  24. ^ Ilja Kogan; Andrea Tintori; Martin Licht (2020). "Locomotor function of scales and axial skeleton in Middle-Late Triassic species of Saurichthys (Actinopterygii". Rivista Italiana di Paleontologia e Stratigrafia. 126 (2): 475–498.
  25. ^ Jump up to: a b Discovery of two new species of primitive fishes
  26. ^ Silvio Renesto; Fabio Magnani; Rudolf Stockar (2021). "A new species of Saurichthys (Actinopterygii: Saurichtydae) from the Middle Triassic of Monte San Giorgio". Rivista Italiana di Paleontologia e Stratigrafia. 127 (1): 49–71.
  27. ^ Fei-Xiang Wu; Yuan-Lin Sun; Geng-Yu Fang (2018). "A new species of Saurichthys from the Middle Triassic (Anisian) of southwestern China". Vertebrata PalAsiatica. 56 (4): 273–294. doi:10.19615/j.cnki.1000-3118.171023.
  28. ^ Fossilworks: Saurichthys Agassiz 1843

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