Homosteus is a genus of flattened arthrodireplacoderm from the Middle Devonian. Fossils are found primarily in Eifelian-epoch aged strata of Europe, Canada, Greenland, and Estonia.[1] All of the species had comparatively large, flattened heads with, as suggested by the upward opening orbits, upward-pointing eyes. These adaptations suggest that the various species were benthic predators. A study on Titanichthys, in contrast, suggests that species of Homosteus may have been filter-feeders instead.[2]
Homosteus specimens from the Old Red Sandstone of Scotland are known to be significantly radioactive, on the order of 1.2 * 104 gamma/min/g [sic].[3][4][5] Notably, Homosteus specimens are the only fish fossils from the Old Red Sandstone to show significant radioactivity. This suggests that these specimens became radioactive from the animals ingesting radioactive isotopes in life (e.g., through ingesting radioactive sediment),[5] rather than radioactive isotopes being absorbed by the bones during fossilization (as in most cases of radioactive fossils).[6] Individuals of Homosteus from the Old Red Sandstone were chronically exposed to enough radiation that these animals would be expected to suffer negative effects of radiation exposure. However, no specimen of Homosteus shows any sign of bone cancer or other radiation-induced pathologies.[5]
The type species of the genus. It is a thin-plated species from the Eifelian-aged Aruküla beds of Estonia. Although H. sulcatus was described earlier in 1837, H. formosissimus is the official type species as it was the first to be described as a placoderm (H. sulcatus was originally described as a soft-shelled turtle). H. formosissimus had a small, thin keel down the dorsal-center of its median dorsal plate.[1]
H. arcticusedit
This species is based on a 15 centimeter-long preorbital plate from the early Eifelian of the Wood Bay formations of Spitzbergen, Norway. Compared to other species, the anatomy of the plate suggests the species is very primitive for the genus. Denison, 1978, suggests that the species may be different enough to merit its own distinct genus.[1]
H. cf. arcticusedit
Based on a specimen found in the Emsian epoch-aged layers of the Wood Bay formations of Spitzbergen. May or may not be of this genus.[1]
H. kochiedit
This species is from the Givetian of Middle Devonian Greenland, of Canning Land, to be precise. H. kochi has a comparatively very narrow nuchal plate.[1]
H. latusedit
A giant species from the Eifelian-aged Aruküla beds of Estonia, and may have existed sympatrically with H. formosissimus. H. latus differed from H. formosissimus in having comparatively thick plates, a large, massive crest-like keel along the dorsal-center of its medial dorsal plate, and head-plates over a meter in length. Originally described as "Trionyx latus Kutorga 1837"[1]
H. manitobensisedit
This species is found in the Eifelian-aged Elm Point Limestone of Manitoba. Based on a pair of paranuchal and marginal plates originally referred to the genus Dinichthys. H. manitobensis is the only member of the genus found in North America proper.[1]
H. milleriedit
H. milleri is from the Givetian of what is now the Orkney and Shetland Islands. It is a medium-sized species with a comparatively very rectangular-shaped median dorsal plate.[1] It is named for Hugh Miller.[7]
H. sulcatusedit
Another species from the Eifelian-aged Aruküla beds of Estonia. Although H. sulcatus was described before H. formosissimus, H. sulcatus was originally described as a soft-shelled turtle, ne "Trionyx sulcatus Kutorga 1837". H. sulcatus had thick plates, and a well-developed keel on the dorsal-center of its median dorsal plate. It was larger than H. formosissimus, but still much smaller than H. latus.[1]
Referencesedit
^ abcdefghiDenison, Robert (1978). Placodermi Volume 2 of Handbook of Paleoichthyology'. Stuttgart New York: Gustav Fischer Verlag. p. 71. ISBN978-0-89574-027-4.
^Coatham, Samuel J.; Vinther, Jakob; Rayfield, Emily J.; Klug, Christian (2020). "Was the Devonian placoderm Titanichthys a suspension feeder?". Royal Society Open Science. 7 (5): 200272. doi:10.1098/rsos.200272. PMC7277245. PMID 32537223.
^Bowie, S. H. U.; Atkin, D. (March 1956). "An Unusually Radioactive Fossil Fish from Thurso, Scotland". Nature. 177 (4506): 487–488. doi:10.1038/177487b0.
^Diggle, W. R.; Saxon, J. (October 1965). "An Unusually Radioactive Fossil Fish from Thurso, Scotland". Nature. 208 (5008): 400–400. doi:10.1038/208400a0.
^ abcSaxon, J. (1979). "The radioactive fossil fishes of the north of Scotland". Caithness Field Club Bulletin. Retrieved 31 December 2022.
^Kielan-Jaworowska, Zofia (2013). In pursuit of early mammals. Bloomington: Indiana University Press. ISBN978-0253008176.
homosteus, genus, flattened, arthrodire, placoderm, from, middle, devonian, fossils, found, primarily, eifelian, epoch, aged, strata, europe, canada, greenland, estonia, species, comparatively, large, flattened, heads, with, suggested, upward, opening, orbits,. Homosteus is a genus of flattened arthrodire placoderm from the Middle Devonian Fossils are found primarily in Eifelian epoch aged strata of Europe Canada Greenland and Estonia 1 All of the species had comparatively large flattened heads with as suggested by the upward opening orbits upward pointing eyes These adaptations suggest that the various species were benthic predators A study on Titanichthys in contrast suggests that species of Homosteus may have been filter feeders instead 2 HomosteusTemporal range Eifelian GivetianH milleriScientific classificationDomain EukaryotaKingdom AnimaliaPhylum ChordataClass PlacodermiOrder ArthrodiraSuborder BrachythoraciFamily HomostiidaeGenus HomosteusType speciesHomosteus formosissimusAsmuss 1856SpeciesH formosissimus Asmuss 1856 H arcticus Heintz 1934 H cf arcticus Orvig 1969 H kochi Stensio amp Save Soderbergh 1938 H latus Asmuss 1856 H manitobensis Okulitch 1944 H milleri Traquair 1888 H sulcatus Kutorga 1837SynonymsDinichthys manitobensis Okulitch 1944 Homostius sp Asmuss 1856 Homosteus anceps Asmuss 1856 Homosteus cataphractus Asmuss 1856 Homosteus ponderosus Asmuss 1856 Trionyx sulcatus Kutorga 1837 Trionyx latus Kutorga 1837Homosteus specimens from the Old Red Sandstone of Scotland are known to be significantly radioactive on the order of 1 2 104 gamma min g sic 3 4 5 Notably Homosteus specimens are the only fish fossils from the Old Red Sandstone to show significant radioactivity This suggests that these specimens became radioactive from the animals ingesting radioactive isotopes in life e g through ingesting radioactive sediment 5 rather than radioactive isotopes being absorbed by the bones during fossilization as in most cases of radioactive fossils 6 Individuals of Homosteus from the Old Red Sandstone were chronically exposed to enough radiation that these animals would be expected to suffer negative effects of radiation exposure However no specimen of Homosteus shows any sign of bone cancer or other radiation induced pathologies 5 Contents 1 Species 1 1 H formosissimus 1 2 H arcticus 1 3 H cf arcticus 1 4 H kochi 1 5 H latus 1 6 H manitobensis 1 7 H milleri 1 8 H sulcatus 2 ReferencesSpecies editH formosissimus edit The type species of the genus It is a thin plated species from the Eifelian aged Arukula beds of Estonia Although H sulcatus was described earlier in 1837 H formosissimus is the official type species as it was the first to be described as a placoderm H sulcatus was originally described as a soft shelled turtle H formosissimus had a small thin keel down the dorsal center of its median dorsal plate 1 H arcticus edit This species is based on a 15 centimeter long preorbital plate from the early Eifelian of the Wood Bay formations of Spitzbergen Norway Compared to other species the anatomy of the plate suggests the species is very primitive for the genus Denison 1978 suggests that the species may be different enough to merit its own distinct genus 1 H cf arcticus edit Based on a specimen found in the Emsian epoch aged layers of the Wood Bay formations of Spitzbergen May or may not be of this genus 1 H kochi edit This species is from the Givetian of Middle Devonian Greenland of Canning Land to be precise H kochi has a comparatively very narrow nuchal plate 1 H latus edit A giant species from the Eifelian aged Arukula beds of Estonia and may have existed sympatrically with H formosissimus H latus differed from H formosissimus in having comparatively thick plates a large massive crest like keel along the dorsal center of its medial dorsal plate and head plates over a meter in length Originally described as Trionyx latus Kutorga 1837 1 H manitobensis edit This species is found in the Eifelian aged Elm Point Limestone of Manitoba Based on a pair of paranuchal and marginal plates originally referred to the genus Dinichthys H manitobensis is the only member of the genus found in North America proper 1 H milleri edit H milleri is from the Givetian of what is now the Orkney and Shetland Islands It is a medium sized species with a comparatively very rectangular shaped median dorsal plate 1 It is named for Hugh Miller 7 H sulcatus edit Another species from the Eifelian aged Arukula beds of Estonia Although H sulcatus was described before H formosissimus H sulcatus was originally described as a soft shelled turtle ne Trionyx sulcatus Kutorga 1837 H sulcatus had thick plates and a well developed keel on the dorsal center of its median dorsal plate It was larger than H formosissimus but still much smaller than H latus 1 References edit a b c d e f g h i Denison Robert 1978 PlacodermiVolume 2 of Handbook of Paleoichthyology Stuttgart New York Gustav Fischer Verlag p 71 ISBN 978 0 89574 027 4 Coatham Samuel J Vinther Jakob Rayfield Emily J Klug Christian 2020 Was the Devonian placoderm Titanichthys a suspension feeder Royal Society Open Science 7 5 200272 doi 10 1098 rsos 200272 PMC 7277245 PMID 32537223 Bowie S H U Atkin D March 1956 An Unusually Radioactive Fossil Fish from Thurso Scotland Nature 177 4506 487 488 doi 10 1038 177487b0 Diggle W R Saxon J October 1965 An Unusually Radioactive Fossil Fish from Thurso Scotland Nature 208 5008 400 400 doi 10 1038 208400a0 a b c Saxon J 1979 The radioactive fossil fishes of the north of Scotland Caithness Field Club Bulletin Retrieved 31 December 2022 Kielan Jaworowska Zofia 2013 In pursuit of early mammals Bloomington Indiana University Press ISBN 978 0253008176 Collections Fossil Homosteus milleri traq Stromness Museum Retrieved 17 February 2024 Retrieved from https en wikipedia org w index php title Homosteus amp oldid 1208451869, wikipedia, wiki, book, books, library,
