Post by creature386 on Jan 24, 2016 18:11:15 GMT 5
Saurichthys spp.
Temporal range: Early–Middle Triassic
Location: Cosmopolitan distribution[1]
Scientific classification:
Osteichthyes
Actinopterygii
Saurichthyiformes
Saurichthyidae
Saurichthys(Agassiz, 1834)
Species:
A bit too long to list, there could be up to 50[2] (though the exact number can be disputed; the Paleobiology Database lists under 30). The type species is S. apicalis.[3]
Description:
As the picture above shows you, Saurichthys was an extremely slender ray-finned fish, resembling a pike. It's head makes up about one third of its body length and is also very elongated. The type species has been identified by Agassiz in 1834 on the basis of jaw fragments. It's name means "lizard fish" and stems from the teeth's similarity to those of reptiles. Most known specimens probably ranged between 50 cm and 1 m in length.[2] The elongation of the axial skeleton results from a doubling of the number of neural arches per myomeric segment which is an unusual elongation mechanism. This innovation likely resulted in higher stability of the vertebral column, but in exchange a lower flexibility of the animal.[4]
Palaeobiology:
Saurichthys was not just found worldwide, but also in both, marine and freshwater strata, indicating that it lived in a variety of environments. Though most species were probably fast-swimming pelagic fish.[2] A reconstructed food web of the Middle Triassic ecosystem of the Fossil Hill Member formation in Nevada listed it as a secondary consumer that preyed on smaller ray-finned fish:[5]
Researches investigated the abdominal cavities of three Saurichthys specimens and found Saurichthys's spiral valve to be strikingly similar to that of sharks and rays. They also looked at its stomach and stated that Saurichthys could have either had a straight, tube-shaped stomach or no true stomach at all (the alternative would be a stomach-like structure that belongs to the gut).
From their findings, the scientists infer that Saurichthys had an active and energy-demanding lifestyle. One of the stomachs shows remains of an undigested Luganoia (a small, ray-finned fish).[6]
Taxonomy:
As noted above, there is some difficulty identifying the species number of Saurichthys which stems from the fact that only a few specimens are known from good fossils. The majority of referred material consists of fragmentary teeth or jaw bones.[2] It's family (Saurichthydae) is known from Upper Permian to Lower Jurassic deposits worldwide and they all share the elongated body.[6] Within the family, it is often classified as a close relative of the Triassic fish Birgeria, though this is not undisputed.[7] Here are three examples of phylogenetic trees from a 1999 study:[8]
Footnotes:
[1] To quote the paper linked in the second footnote:
Fragmentary Saurichthys remains have been reported from various Early and Middle Triassic sections of the former Soviet Union (mostly European, but also Asian part of Russia; MINIKH, 1981, 1982, 1992; MINIKH & MINIKH, 2006). Marine Early Triassic (Olenekian) strata of Mangyshlak, Western Kazakhstan, represent the occurrence nearest to Madygen (MINIKH, 1981).
[2] Kogan, I., Schönberger, K., Fischer, J. & Voigt, S. (2009): A nearly complete skeleton of Saurichthys orientalis (Pisces, Actinopterygii) from the Madygen Formation (Middle to Late Triassic, Kyrgyzstan, Central Asia) – preliminary results. Paläontologie, Stratigraphie, Fazies (17), Freiberger Forschungshefte, C 532: 139– 152; Freiberg.
[3] fossilworks.org/?page=paleodb (includes a list of some species)
[4] Erin E. Maxwell et al. 2013. Exceptional fossil preservation demonstrates a new mode of axial skeleton elongation in early ray-finned fishes. Nature Communications (4), 2570; doi:10.1038/ncomms3570
[5] Fröbisch, N. B.; Fröbisch, J. R.; Sander, P. M.; Schmitz, L.; Rieppel, O. (2013). Macropredatory ichthyosaur from the Middle Triassic and the origin of modern trophic networks. Proceedings of the National Academy of Sciences. doi:10.1073/pnas.1216750110
[6] Thodoris Argyriou, Marcus Clauss, Erin E. Maxwell, Heinz Furrer, Marcelo R. Sánchez-Villagra. Exceptional preservation reveals gastrointestinal anatomy and evolution in early actinopterygian fishes. Scientific Reports, 2016; 6: 18758 doi:10.1038/srep18758
[7] Some authors give Birgeria it's own family: fossilworks.org/bridge.pl?taxon_no=54880&action=taxonInfo
[8] Coates, M. I. (1999) Endocranial preservation of a Carboniferous actinopterygian from Lancashire, UK, and the interrelationships of primitive actinopterygians. Philos. Trans. R. Soc. London Biol. 354, 435–462.
Temporal range: Early–Middle Triassic
Location: Cosmopolitan distribution[1]
Scientific classification:
Osteichthyes
Actinopterygii
Saurichthyiformes
Saurichthyidae
Saurichthys(Agassiz, 1834)
Species:
A bit too long to list, there could be up to 50[2] (though the exact number can be disputed; the Paleobiology Database lists under 30). The type species is S. apicalis.[3]
Description:
As the picture above shows you, Saurichthys was an extremely slender ray-finned fish, resembling a pike. It's head makes up about one third of its body length and is also very elongated. The type species has been identified by Agassiz in 1834 on the basis of jaw fragments. It's name means "lizard fish" and stems from the teeth's similarity to those of reptiles. Most known specimens probably ranged between 50 cm and 1 m in length.[2] The elongation of the axial skeleton results from a doubling of the number of neural arches per myomeric segment which is an unusual elongation mechanism. This innovation likely resulted in higher stability of the vertebral column, but in exchange a lower flexibility of the animal.[4]
Palaeobiology:
Saurichthys was not just found worldwide, but also in both, marine and freshwater strata, indicating that it lived in a variety of environments. Though most species were probably fast-swimming pelagic fish.[2] A reconstructed food web of the Middle Triassic ecosystem of the Fossil Hill Member formation in Nevada listed it as a secondary consumer that preyed on smaller ray-finned fish:[5]
Researches investigated the abdominal cavities of three Saurichthys specimens and found Saurichthys's spiral valve to be strikingly similar to that of sharks and rays. They also looked at its stomach and stated that Saurichthys could have either had a straight, tube-shaped stomach or no true stomach at all (the alternative would be a stomach-like structure that belongs to the gut).
From their findings, the scientists infer that Saurichthys had an active and energy-demanding lifestyle. One of the stomachs shows remains of an undigested Luganoia (a small, ray-finned fish).[6]
Taxonomy:
As noted above, there is some difficulty identifying the species number of Saurichthys which stems from the fact that only a few specimens are known from good fossils. The majority of referred material consists of fragmentary teeth or jaw bones.[2] It's family (Saurichthydae) is known from Upper Permian to Lower Jurassic deposits worldwide and they all share the elongated body.[6] Within the family, it is often classified as a close relative of the Triassic fish Birgeria, though this is not undisputed.[7] Here are three examples of phylogenetic trees from a 1999 study:[8]
Footnotes:
[1] To quote the paper linked in the second footnote:
Fragmentary Saurichthys remains have been reported from various Early and Middle Triassic sections of the former Soviet Union (mostly European, but also Asian part of Russia; MINIKH, 1981, 1982, 1992; MINIKH & MINIKH, 2006). Marine Early Triassic (Olenekian) strata of Mangyshlak, Western Kazakhstan, represent the occurrence nearest to Madygen (MINIKH, 1981).
[2] Kogan, I., Schönberger, K., Fischer, J. & Voigt, S. (2009): A nearly complete skeleton of Saurichthys orientalis (Pisces, Actinopterygii) from the Madygen Formation (Middle to Late Triassic, Kyrgyzstan, Central Asia) – preliminary results. Paläontologie, Stratigraphie, Fazies (17), Freiberger Forschungshefte, C 532: 139– 152; Freiberg.
[3] fossilworks.org/?page=paleodb (includes a list of some species)
[4] Erin E. Maxwell et al. 2013. Exceptional fossil preservation demonstrates a new mode of axial skeleton elongation in early ray-finned fishes. Nature Communications (4), 2570; doi:10.1038/ncomms3570
[5] Fröbisch, N. B.; Fröbisch, J. R.; Sander, P. M.; Schmitz, L.; Rieppel, O. (2013). Macropredatory ichthyosaur from the Middle Triassic and the origin of modern trophic networks. Proceedings of the National Academy of Sciences. doi:10.1073/pnas.1216750110
[6] Thodoris Argyriou, Marcus Clauss, Erin E. Maxwell, Heinz Furrer, Marcelo R. Sánchez-Villagra. Exceptional preservation reveals gastrointestinal anatomy and evolution in early actinopterygian fishes. Scientific Reports, 2016; 6: 18758 doi:10.1038/srep18758
[7] Some authors give Birgeria it's own family: fossilworks.org/bridge.pl?taxon_no=54880&action=taxonInfo
[8] Coates, M. I. (1999) Endocranial preservation of a Carboniferous actinopterygian from Lancashire, UK, and the interrelationships of primitive actinopterygians. Philos. Trans. R. Soc. London Biol. 354, 435–462.