For the reptile group, see Anapsida. For the gastropod clade, see Anaspidea. For the freshwater crustacean family, see Anaspididae.
Anaspida ("shieldless ones") is an extinct group of jawless fish that existed from the early Silurian period to the late Devonian period.[2] They were classically regarded as the ancestors of lampreys.[3] Anaspids were small marine fish that lacked a heavy bony shield and paired fins, but were distinctively hypocercal.
Compared to other prehistoric agnathan groups, such as the Heterostraci and Osteostraci, anaspids did not possess a bony shield or armor, hence their name. The anaspid head and body are instead covered in an array of small, weakly mineralized scales, with a row of massive scutes running down the back, and, at least confirmed among the birkeniids, the body was covered in rows of tile-like scales made of aspidine, an acellular bony tissue.[4] Anaspids all had prominent, laterally placed eyes with no sclerotic ring, with the gills opened as a row of holes along either side of the animal, typically numbering anywhere from 6-15 pairs. The major synapomorphy for the anaspids is the large, tri-radiate spine behind the series of the gill openings.[1]
TaxonomyEdit
Now that Jamoytius and its close cohorts, i.e., Euphanerops, have been moved to Jamoytiiformes,[5]Class Anaspida now consists of two orders, the monogeneric Lasaniida, which contains the genus Lasanius and represents a basal anaspid group,[6] and Birkeniida, which contains all other recognized anaspid taxa.[7] Birkeniida is further divided into several families, including Birkeniidae, Pterygolepididae, Rhyncholepididae and Pharyngolepididae, which contain those taxa known from whole body fossils (in addition to several taxa known only from scales) and the family Septentrioniidae, whose subtaxa are known exclusively from scales.[7] Two recently described genera, Kerreralepis[6] and Cowielepis,[8] are considered to be Birkeniida incertae sedis.
^Ahlberg, Per Erik (2001). Major events in early vertebrate evolution: palaeontology, phylogeny, genetics, and development. Washington, DC: Taylor & Francis. p. 188. ISBN0-415-23370-4.
^Patterson, Colin (1987). Molecules and morphology in evolution: conflict or compromise?. Cambridge, UK: Cambridge University Press. p. 142. ISBN0-521-32271-5.
^Janvier, Philippe (2003). Early Vertebrates. Oxford University Press. ISBN978-0-19-852646-9.
^Sansom, Robert S., et al. "Taphonomy and affinity of an enigmatic Silurian vertebrate, Jamoytius kerwoodi White." Palaeontology 53.6 (2010): 1393-1409.
^ abBlom, Henning. "New birkeniid anaspid from the Lower Devonian of Scotland and its phylogenetic implications." Palaeontology 55.3 (2012): 641-652.
^ abBlom, Henning, T. Märss, and C. G. Miller. "Silurian and earliest Devonian birkeniid anaspids from the Northern Hemisphere." Earth and Environmental Science Transactions of the Royal Society of Edinburgh 92.03 (2001): 263-323.
^Blom, Henning. "A new anaspid fish from the Middle Silurian Cowie Harbour fish bed of Stonehaven, Scotland." Journal of Vertebrate Paleontology 28.3 (2008): 594-600.
^Reeves, Jane C.; Wogelius, Roy A.; Keating, Joseph N.; Sansom, Robert S. (March 2023). Cavin, Lionel (ed.). "Lasanius , an exceptionally preserved Silurian jawless fish from Scotland". Palaeontology. 66 (2): e12643. doi:10.1111/pala.12643. ISSN 0031-0239.
^Haaramo, Mikko (2003). "†Anaspida – anaspids". In Mikko's Phylogeny Archive. Retrieved November 25, 2018.
^van der Laan, Richard (2018). "Family-group names of fossil fishes". {{cite journal}}: Cite journal requires |journal= (help)
External linksEdit
"The Anaspida - unarmoured "ostracoderms"". Palaeos: Life Through Deep Time. Retrieved 2012-11-24.
Monroe M. H. "Anaspida "no shield"". Australia: The Land Where Time Began. Retrieved 2012-11-24.
October 21, 2023
anaspida, reptile, group, anapsida, gastropod, clade, anaspidea, freshwater, crustacean, family, anaspididae, shieldless, ones, extinct, group, jawless, fish, that, existed, from, early, silurian, period, late, devonian, period, they, were, classically, regard. For the reptile group see Anapsida For the gastropod clade see Anaspidea For the freshwater crustacean family see Anaspididae Anaspida shieldless ones is an extinct group of jawless fish that existed from the early Silurian period to the late Devonian period 2 They were classically regarded as the ancestors of lampreys 3 Anaspids were small marine fish that lacked a heavy bony shield and paired fins but were distinctively hypocercal AnaspidaTemporal range 444 419 Ma PreꞒ Ꞓ O S D C P T J K Pg N early Silurian Early DevonianCowielepisScientific classificationDomain EukaryotaKingdom AnimaliaPhylum ChordataSuperclass AnaspidomorphiClass AnaspidaTraquair 1899Type species Birkenia elegansTraquair 1898OrdersEndeiolepidiformes BirkeniiformesSynonymsAnaspidi BirkeniaeAnaspids are characterized by a large tri radiate spine red posteriorly to the series of branchial openings It is assumed that the most primitive anaspids such as Pharyngolepis top possessed a long ribbon shaped ventrolateral fin fold green More advanced forms such as Rhyncholepis bottom possessed a shorter paired fin fold green and enlarged spine shaped median dorsal scutes Philippe Janvier 1 Contents 1 Anatomy 2 Taxonomy 3 Notes 4 External linksAnatomy EditCompared to other prehistoric agnathan groups such as the Heterostraci and Osteostraci anaspids did not possess a bony shield or armor hence their name The anaspid head and body are instead covered in an array of small weakly mineralized scales with a row of massive scutes running down the back and at least confirmed among the birkeniids the body was covered in rows of tile like scales made of aspidine an acellular bony tissue 4 Anaspids all had prominent laterally placed eyes with no sclerotic ring with the gills opened as a row of holes along either side of the animal typically numbering anywhere from 6 15 pairs The major synapomorphy for the anaspids is the large tri radiate spine behind the series of the gill openings 1 Taxonomy EditNow that Jamoytius and its close cohorts i e Euphanerops have been moved to Jamoytiiformes 5 Class Anaspida now consists of two orders the monogeneric Lasaniida which contains the genus Lasanius and represents a basal anaspid group 6 and Birkeniida which contains all other recognized anaspid taxa 7 Birkeniida is further divided into several families including Birkeniidae Pterygolepididae Rhyncholepididae and Pharyngolepididae which contain those taxa known from whole body fossils in addition to several taxa known only from scales and the family Septentrioniidae whose subtaxa are known exclusively from scales 7 Two recently described genera Kerreralepis 6 and Cowielepis 8 are considered to be Birkeniida incertae sedis Some authors have suggested that anaspids are stem cyclostomes related to hagfish and lampreys 9 A newer taxonomy based on the work of Mikko s Phylogeny Archive 10 Nelson Grande and Wilson 2016 11 and van der Laan 2018 12 Class Anaspida Janvier 1996 non Williston 1917 Order Endeiolepidiformes Berg 1940 Family Endeiolepididae Stensio 1939 corrig Genus Endeiolepis Stensio 1939 Order Birkeniiformes Berg 1940 Genus Cowielepis Blom 2008 Genus Hoburgilepis Blom Marss amp Miller 2002 Genus Kerreralepis Blom 2012 Genus Maurylepis Blom Marss amp Miller 2002 Genus Rytidolepis Pander 1856 Genus Schidiosteus Pander 1856 Genus Silmalepis Blom Marss amp Miller 2002 Genus Vesikulepis Blom Marss amp Miller 2002 Family Pharyngolepididae Kiaer 1924 corrig Genus Pharyngolepis Kiaer 1911 Family Pterygolepididae Obruchev 1964 corrig Genus Pterygolepis Cossmann 1920 Pterolepis Kiaer 1911 non Rambur 1838 non De Candolle ex Miquel 1840 Pterolepidops Fowler 1947 Family Rhyncholepididae Kiaer 1924 corrig Genus Rhyncholepis Kiaer 1911 non Miquel 1843 non Nuttall 1841 Family Tahulalepididae Blom Marss amp Miller 2002 Genus Tahulalepis Blom Marss amp Miller 2002 Genus Trimpleylepis Miller Marss amp Blom 2004 Family Lasaniidae Goodrich 1909 Genus Lasanius Traquair 1898 Family Ramsaasalepididae Blom Marss amp Miller 2003 Genus Ramsaasalepis Blom Marss amp Miller 2003 Family Birkeniidae Traquair 1899 Genus Vilkitskilepis Marss 2002 Genus Ctenopleuron Matthew 1907 Genus Saarolepis Robertson 1945 Anaspis Robertson 1941 non Geoffroy 1762 non Thomson 1893 Genus Birkenia Traquair 1898 Family Septentrioniidae Blom Marss amp Miller 2002 Genus Liivilepis Blom Marss amp Miller 2002 Genus Manbrookia Blom Marss amp Miller 2002 Genus Ruhnulepis Blom Marss amp Miller 2002 Genus Spokoinolepis Blom Marss amp Miller 2002 Genus Septentrionia Blom Marss amp Miller 2002 nbsp Life reconstruction of Lasanius problematicusNotes Edit a b Janvier Philippe 1997 Anaspida The Tree of Life Web Project Ahlberg Per Erik 2001 Major events in early vertebrate evolution palaeontology phylogeny genetics and development Washington DC Taylor amp Francis p 188 ISBN 0 415 23370 4 Patterson Colin 1987 Molecules and morphology in evolution conflict or compromise Cambridge UK Cambridge University Press p 142 ISBN 0 521 32271 5 Janvier Philippe 2003 Early Vertebrates Oxford University Press ISBN 978 0 19 852646 9 Sansom Robert S et al Taphonomy and affinity of an enigmatic Silurian vertebrate Jamoytius kerwoodi White Palaeontology 53 6 2010 1393 1409 a b Blom Henning New birkeniid anaspid from the Lower Devonian of Scotland and its phylogenetic implications Palaeontology 55 3 2012 641 652 a b Blom Henning T Marss and C G Miller Silurian and earliest Devonian birkeniid anaspids from the Northern Hemisphere Earth and Environmental Science Transactions of the Royal Society of Edinburgh 92 03 2001 263 323 Blom Henning A new anaspid fish from the Middle Silurian Cowie Harbour fish bed of Stonehaven Scotland Journal of Vertebrate Paleontology 28 3 2008 594 600 Reeves Jane C Wogelius Roy A Keating Joseph N Sansom Robert S March 2023 Cavin Lionel ed Lasanius an exceptionally preserved Silurian jawless fish from Scotland Palaeontology 66 2 e12643 doi 10 1111 pala 12643 ISSN 0031 0239 Haaramo Mikko 2003 Anaspida anaspids In Mikko s Phylogeny Archive Retrieved November 25 2018 Nelson Joseph S Grande Terry C Wilson Mark V H 2016 Fishes of the World 5th ed John Wiley amp Sons ISBN 9781118342336 van der Laan Richard 2018 Family group names of fossil fishes a href Template Cite journal html title Template Cite journal cite journal a Cite journal requires journal help External links Edit The Anaspida unarmoured ostracoderms Palaeos Life Through Deep Time Retrieved 2012 11 24 Monroe M H Anaspida no shield Australia The Land Where Time Began Retrieved 2012 11 24 Retrieved from https en wikipedia org w index php title Anaspida amp oldid 1177564488, wikipedia, wiki, book, books, library,