Mixopterus is a genus of eurypterid, an extinct group of aquatic arthropods. Fossils of Mixopterus have been discovered in deposits from Late Silurian age, and have been referred to several different species. Fossils have been recovered from two continents; Europe and North America.[1]
Mixopterus was a medium-sized predatory eurypterid. The largest species, M. simonsoni, reached lengths of 75 cm (29.5 in).[2] It was characterised by a robust exoskeleton with scattered tubercles or semicircular scales. The prosoma (head) was subquadrate, protruding antemedially. The chelicerae (claws in front of the mouth) were small.[3] The two first pairs of legs of Mixopterus (appendages II and III) were highly specialized and not used for walking, instead being highly developed with long paired spines.[3] The two following pairs (appendages IV and V) were moderately sized and typically spiniferous walking legs. The last legs, (VI), form a pair of swimming legs characteristic of the Eurypterida.[4]
The preabdomen, the front portion of the body, was narrow with axial furrows, while the postabdomen was narrow. The telson was a curved spine.[5] By thrusting and pushing the tail, the telson spine would be capable of stinging prey in between the front legs. The structure of the tail of indicates that Mixopterus would be able to move on land, but such movement would likely be difficult because of its weight. Respiration would not be an issue, since moist gills would be well concealed above the ventral plates.[4]Mixopterus might have buried itself in the sand to wait for prey, as the swimming legs were very well-adapted for digging. The frontal legs and foremost portion of the prosoma, including the eyes, would have been kept above the substrate. When a prey was sufficiently close, the frontal appendages would be clasped together, almost forming a cage.[4]
PaleobiologyEdit
Frontal appendage of M. kiaeri with preserved spines.
LocomotionEdit
Eurypterids with swimming legs were capable of both walking on the bottom of bodies of water or swimming through them. Unlike some highly derived eurypterines, Mixopterus is not thought to have been a good swimmer and it likely kept near the bottom. During swimming, the prosomal legs (appendages IV and V) were probably positioned backwards to produce minor lateral strokes. The swimming legs were likely used as flaps for moving vertically. It might have been able to push itself forward with rapid strokes of the ventral plates, but this is considered unlikely.[4]
Mixopterus likely walked on the bottom with a gait similar to most insects. The two heavy and specialized frontal appendages, held above the bottom, would balance the weight of the long abdomen. The spread appendages would give a decent foothold, perhaps adjustable by raising the tail. On land, the raised tail would act as balance for the body. This was more important on land, as the weight of the body is larger without water.[4]
ReproductionEdit
Mixopterus preserves a long ventro-medially placed genital appendage.[4] Mating in Mixopterus would likely be similar to that in horseshoe crabs. There is a presumed clasping organ on appendage II shaped as a flat and round lobee with a blade-shaped flat spine behind, overall similar to the clasping organs of Limulus. The male could then attach itself to the lateral corners of the last prosomal segment, and direct its long genital appendage to the point where the eggs were stored by the female.[4]
SpeciesEdit
Size comparison of the three species of Mixopterus
Mixopterus contains three valid species, with some others that historically have been assigned to it being recovered as outside of the genus. The species currently seen as valid species of the genus are:
Mixopterus multispinosus Clarke & Ruedemann, 1912 - New York (Silurian)
Mixopterus simonsoni Schmidt, 1883 - Saaremaa, Estonia (Silurian)
Invalid or reassigned species are listed below:
Mixopterus dolichoschelus Peach and Horne, 1899 - Lanarkshire and Ayrshire, Scotland (Silurian), reclassified as its own genus, Lanarkopterus.[6]
IchnologyEdit
Tracks attributed to Mixopterus have been discovered in fossil deposits in Ringerike, Norway. The tracks, referred to the ichnogenusMerostomichnites, were made by an arthropod in which only three pairs of legs took part in the gait, the last pair being swimming legs.[4]
Swimming legs that constitute the last limbs of the prosoma are present in eurypterine eurypterids, out of which the only reasonably large taxa present in the silurian deposits of Ringerike are Mixopterus kiaeri and Pterygotus holmi. With its slender and spineless walking legs and short genital appendage, Pterygotus could not have produced the tracks, though they match the size and morphology of M. kiaeri rather well. The great morphological similarities as well as the relative abundance of M. kiaeri in the region prompted Hanken and Størmer (1975)[4] to refer the tracks to Mixopterus.
^Lamsdell, James C.; Braddy, Simon J. (2009). "Cope's rule and Romer's theory: patterns of diversity and gigantism in eurypterids and Palaeozoic vertebrates". Biology Letters. 6 (2): 265–269. doi:10.1098/rsbl.2009.0700. ISSN 1744-9561. PMC2865068. PMID 19828493. Supplemental material.
^ abEuan Neilson Kerr Clarkson (1998). "Arthropods". Invertebrate Palaeontology and Evolution (4th ed.). Wiley-Blackwell. pp. 348–405. ISBN978-0-632-05238-7.
^ abcdefghiHanken, N.-M. & Størmer, L. (1975): "The trail of a large Silurian eurypterid". Fossils and Strata, No. 4, pp. 255-270, Pl. 1 -3.
^Ritchie, Alexander (1968-12-01). "Lanarkopterus dolichoschelus (Størmer) gen. nov., a mixopterid eurypterid from the Upper Silurian of the Lesmahagow and Hagshaw Hills inliers, Scotland". Scottish Journal of Geology. 4 (4): 317–338. doi:10.1144/sjg04040317. ISSN 0036-9276. S2CID 129769781.
August 29, 2023
mixopterus, genus, eurypterid, extinct, group, aquatic, arthropods, fossils, have, been, discovered, deposits, from, late, silurian, have, been, referred, several, different, species, fossils, have, been, recovered, from, continents, europe, north, america, te. Mixopterus is a genus of eurypterid an extinct group of aquatic arthropods Fossils of Mixopterus have been discovered in deposits from Late Silurian age and have been referred to several different species Fossils have been recovered from two continents Europe and North America 1 MixopterusTemporal range Late Silurian 426 2 416 Ma PreꞒ Ꞓ O S D C P T J K Pg NFossil of M kiaeri exhibited at the Moscow Paleontological Museum Scientific classificationDomain EukaryotaKingdom AnimaliaPhylum ArthropodaSubphylum ChelicerataOrder EurypteridaSuperfamily CarcinosomatoideaFamily MixopteridaeGenus MixopterusRuedemann 1921Type species Mixopterus multispinosusRuedemann 1921Species M kiaeri Stormer 1934 M multispinosus Ruedemann 1921 M simonsoni Schmidt 1883 Contents 1 Description 2 Paleobiology 2 1 Locomotion 2 2 Reproduction 3 Species 4 Ichnology 5 See also 6 ReferencesDescription Edit Life restoration of M kiaeri Mixopterus was a medium sized predatory eurypterid The largest species M simonsoni reached lengths of 75 cm 29 5 in 2 It was characterised by a robust exoskeleton with scattered tubercles or semicircular scales The prosoma head was subquadrate protruding antemedially The chelicerae claws in front of the mouth were small 3 The two first pairs of legs of Mixopterus appendages II and III were highly specialized and not used for walking instead being highly developed with long paired spines 3 The two following pairs appendages IV and V were moderately sized and typically spiniferous walking legs The last legs VI form a pair of swimming legs characteristic of the Eurypterida 4 The preabdomen the front portion of the body was narrow with axial furrows while the postabdomen was narrow The telson was a curved spine 5 By thrusting and pushing the tail the telson spine would be capable of stinging prey in between the front legs The structure of the tail of indicates that Mixopterus would be able to move on land but such movement would likely be difficult because of its weight Respiration would not be an issue since moist gills would be well concealed above the ventral plates 4 Mixopterus might have buried itself in the sand to wait for prey as the swimming legs were very well adapted for digging The frontal legs and foremost portion of the prosoma including the eyes would have been kept above the substrate When a prey was sufficiently close the frontal appendages would be clasped together almost forming a cage 4 Paleobiology Edit Frontal appendage of M kiaeri with preserved spines Locomotion Edit Eurypterids with swimming legs were capable of both walking on the bottom of bodies of water or swimming through them Unlike some highly derived eurypterines Mixopterus is not thought to have been a good swimmer and it likely kept near the bottom During swimming the prosomal legs appendages IV and V were probably positioned backwards to produce minor lateral strokes The swimming legs were likely used as flaps for moving vertically It might have been able to push itself forward with rapid strokes of the ventral plates but this is considered unlikely 4 Mixopterus likely walked on the bottom with a gait similar to most insects The two heavy and specialized frontal appendages held above the bottom would balance the weight of the long abdomen The spread appendages would give a decent foothold perhaps adjustable by raising the tail On land the raised tail would act as balance for the body This was more important on land as the weight of the body is larger without water 4 Reproduction Edit Mixopterus preserves a long ventro medially placed genital appendage 4 Mating in Mixopterus would likely be similar to that in horseshoe crabs There is a presumed clasping organ on appendage II shaped as a flat and round lobee with a blade shaped flat spine behind overall similar to the clasping organs of Limulus The male could then attach itself to the lateral corners of the last prosomal segment and direct its long genital appendage to the point where the eggs were stored by the female 4 Species Edit Size comparison of the three species of MixopterusMixopterus contains three valid species with some others that historically have been assigned to it being recovered as outside of the genus The species currently seen as valid species of the genus are Mixopterus kiaeri Stormer 1934 Ringerike Norway Silurian Mixopterus multispinosus Clarke amp Ruedemann 1912 New York Silurian Mixopterus simonsoni Schmidt 1883 Saaremaa Estonia Silurian Invalid or reassigned species are listed below Mixopterus dolichoschelus Peach and Horne 1899 Lanarkshire and Ayrshire Scotland Silurian reclassified as its own genus Lanarkopterus 6 Ichnology EditTracks attributed to Mixopterus have been discovered in fossil deposits in Ringerike Norway The tracks referred to the ichnogenus Merostomichnites were made by an arthropod in which only three pairs of legs took part in the gait the last pair being swimming legs 4 Swimming legs that constitute the last limbs of the prosoma are present in eurypterine eurypterids out of which the only reasonably large taxa present in the silurian deposits of Ringerike are Mixopterus kiaeri and Pterygotus holmi With its slender and spineless walking legs and short genital appendage Pterygotus could not have produced the tracks though they match the size and morphology of M kiaeri rather well The great morphological similarities as well as the relative abundance of M kiaeri in the region prompted Hanken and Stormer 1975 4 to refer the tracks to Mixopterus See also Edit Arthropods portal Paleontology portalList of eurypterid genera Pterygotioidea CarcinosomatoideaReferences Edit Dunlop J A Penney D amp Jekel D 2015 A summary list of fossil spiders and their relatives In World Spider Catalog Natural History Museum Bern online at http wsc nmbe ch version 18 5 http www wsc nmbe ch resources fossils Fossils18 5 pdf PDF Lamsdell James C Braddy Simon J 2009 Cope s rule and Romer s theory patterns of diversity and gigantism in eurypterids and Palaeozoic vertebrates Biology Letters 6 2 265 269 doi 10 1098 rsbl 2009 0700 ISSN 1744 9561 PMC 2865068 PMID 19828493 Supplemental material a b Euan Neilson Kerr Clarkson 1998 Arthropods Invertebrate Palaeontology and Evolution 4th ed Wiley Blackwell pp 348 405 ISBN 978 0 632 05238 7 a b c d e f g h i Hanken N M amp Stormer L 1975 The trail of a large Silurian eurypterid Fossils and Strata No 4 pp 255 270 Pl 1 3 Leif Stormer 1955 Merostomata Part P Arthropoda 2 Chelicerata Treatise on Invertebrate Paleontology pp 34 35 Ritchie Alexander 1968 12 01 Lanarkopterus dolichoschelus Stormer gen nov a mixopterid eurypterid from the Upper Silurian of the Lesmahagow and Hagshaw Hills inliers Scotland Scottish Journal of Geology 4 4 317 338 doi 10 1144 sjg04040317 ISSN 0036 9276 S2CID 129769781 Retrieved from https en wikipedia org w index php title Mixopterus amp oldid 1165323530, wikipedia, wiki, book, books, library,
