Mesolenellus is a contraction of meso - middle - and Olenellus, the genus from which it was split off. The epithethyperborea is a contraction of hyper (Greek ὑπέρ "excess") and Boreas (Greek: Βορέας), god of the North Wind in Greek mythology, referencing the current geographical position of the deposits of its type location. M. svalbardensis has been named for the Norwegian island group Svalbard or Spitsbergen, where it was originally collected.
Taxonomyedit
It was considered a subgenus of Olenellus before.[3] The nearest relatives of Mesolenellus are the species of the genus Mesonacis, with which it constitutes the subfamily Mesonacinae.
Distributionedit
Mesolenellus hyperborea occurs in the Botomian (Nevadella-zone) of the paleocontinentLaurentia, now Greenland (Upper Buen Formation, above Brillesø, 1.5 km east of Borglum Elv, Peary Land, North-Eastern end of the island).[4] The occurrence of M. hyperborea has been specified as the early mudstone layer of the Upper Buen Formation. The famous Sirius Passet fauna (e.g. Kleptothule and Aaveqaspis) occurs in the lowest (sandy) member of the Buen Formation and thus predates Mesolenellus.[5]
M. svalbardensis has been found in the Botomian (Nevadella-zone) of Laurentia, now Svalbard/Spitsbergen (lower Slakli Series, Sofiekammen Formation, northern side of the Hornsund, West-Spitsbergen). A specimen that probably belongs to M. svalbardensis or is closely related was found in Greenland (Schley Fjord Formation, Peary land).[6] There is a further mention of the occurrence in Greenland for the late mudstone layer of the Upper Buen Formation,[5] indicating that M. hyperborea predated M. svalbardensis.
Habitatedit
The mudstone in which both species were found indicates deeper, quiet waters.[5]
As with most early trilobites, Mesolenellus has an almost flat exoskeleton, that is only thinly calcified, and has crescent-shaped eye ridges. As part of the suborder Olenellina, Olenellus lacks dorsal sutures. Like all other members of the superfamily Olenelloidea, the eye-ridges spring from the back of the frontal lobe (L4) of the central area of the cephalon, that is called glabella. Mesolenellus also shares the typical character of the whole family Olenellidae that the frontal (L3) and middle pair (L2) of lateral lobes of the glabella are partially merged. This creates two very typical, isolated slits. Mesolenellus is a genus within the Mesonacinae, with eye-ridges curved but almost parallel to the midline. The back of the eye-ridges is opposite the most backward ring of the glabella (L0 or occipital ring). Genal spines are 6-8 times as long as L0. The outer furrows of the glabella are parallel to the midline between the back of the cephalon and the furrow between side lobes L2 and L3. The thorax is 3 times as wide as the axis at the 3rd segment. Mesolenellus can be distinguished from the sister-genus Mesonacis, where the back of the eye-ridge extends only to the most backward side lobes (L1), genal spines are only 1-5 times as long as L0, and the glabella widens forwards along L1 and L2. Except for in Mesonacis fremonti the curved eye-ridges are at an angle of 15°-20° with the midline. A third genus Olenellus, that constitutes the second subfamily of the family Olenellidae differs from Mesolenellus in having genal spines 4-5 times as long as L0, the glabella widens forwards along L1 and L2, and the thorax 4-4½ times wider that the axis at the 3rd segment.[1]
Key to the speciesedit
1
A short ridge (called plectrum) connects the frontal lobe of the glabella with the frontal border of the headshield. The section of the border of the back of the head (posterior cephalic border) halfway between the midline and the genal angle (between the axis and the intergenal angle) has a backward angle. The base of the genal spine is opposite the most backward ring of the glabella (L0). The furrow between the 2nd and 3rd ring (S2) does not contact the furrow that outlines the glabella (or axial furrow).[1]Nevadella-zone. Svalbard (Vestspitsbergen, Hornsund) and Greenland (Peary Land, Schley Fjord Formation and Buen Formation). → M. svalbardensis (Kielan, 1960)
-
Plectrum absent. The midsection of the posterior cephalic border is transverse. The base of the genal spine is opposite the middle ring of the glabella (L2). S2 contacts the axial furrow.[1]Nevadella-zone. Greenland (Buen Formation). → M. hyperborea (Poulsen, 1974)
Referencesedit
^ abcdefLieberman, B.S. (1999). (PDF). Bulletin of the Peabody Museum of Natural History. 45. Archived from the original (PDF) on 2016-06-24. Retrieved 2012-10-30.
^Cowie, J.; McNamara, K.J. (1978). (PDF). Palaeontology. 21 (3): 615–634. Archived from the original (PDF) on 2012-05-26.
^H. B. Whittington; et al. (1997). "Introduction, Order Agnostida, Order Redlichiida". Treatise on Invertebrate Paleontology. Part O, Revised. Trilobita.
^Poulsen, V. (1974). "Olenellacean trilobites from eastern North Greenland". Bulletin of the Geological Society of Denmark. 23: 79–101.
^ abcdMark R. Blaker & John S. Peel (1997). Lower Cambrian trilobites from North Greenland. Meddelelser om Grønland. Geoscience. Vol. 35. ISBN978-87-635-1241-1.
^Kielan, Z. (1960). "On two olenellid trilobites from Hornsund, Vestspitsvergen". Studia Geologica Polonica. 4: 133–139.
External linksedit
Trilobite info
January 01, 1970
mesolenellus, extinct, genus, trilobites, that, lived, during, lower, cambrian, botomian, found, greenland, spitsbergen, temporal, range, preꞒ, botomian, scientific, classification, kingdom, animalia, phylum, arthropoda, class, trilobita, order, redlichiida, s. Mesolenellus is an extinct genus of trilobites that lived during the lower Cambrian Botomian found in Greenland and Spitsbergen 1 MesolenellusTemporal range 516 513 Ma PreꞒ Ꞓ O S D C P T J K Pg N Botomian Scientific classification Kingdom Animalia Phylum Arthropoda Class Trilobita Order Redlichiida Suborder Olenellina Superfamily Olenelloidea Family Olenellidae Subfamily Mesonacinae Genus MesolenellusPalmer amp Repina 1993 Species Mesolenellus hyperborea Poulsen 1974 type species synonyms Olenellus hyperborea Holmia hyperborea 1 Mesolenellus svalbardensis Kielan 1960 synonym Olenellus svalbardensis 1 2 Contents 1 Etymology 2 Taxonomy 3 Distribution 4 Habitat 5 Ecology 6 Description 7 Key to the species 8 References 9 External linksEtymology editMesolenellus is a contraction of meso middle and Olenellus the genus from which it was split off The epithet hyperborea is a contraction of hyper Greek ὑper excess and Boreas Greek Boreas god of the North Wind in Greek mythology referencing the current geographical position of the deposits of its type location M svalbardensis has been named for the Norwegian island group Svalbard or Spitsbergen where it was originally collected Taxonomy editIt was considered a subgenus of Olenellus before 3 The nearest relatives of Mesolenellus are the species of the genus Mesonacis with which it constitutes the subfamily Mesonacinae Distribution editMesolenellus hyperborea occurs in the Botomian Nevadella zone of the paleocontinent Laurentia now Greenland Upper Buen Formation above Brilleso 1 5 km east of Borglum Elv Peary Land North Eastern end of the island 4 The occurrence of M hyperborea has been specified as the early mudstone layer of the Upper Buen Formation The famous Sirius Passet fauna e g Kleptothule and Aaveqaspis occurs in the lowest sandy member of the Buen Formation and thus predates Mesolenellus 5 M svalbardensis has been found in the Botomian Nevadella zone of Laurentia now Svalbard Spitsbergen lower Slakli Series Sofiekammen Formation northern side of the Hornsund West Spitsbergen A specimen that probably belongs to M svalbardensis or is closely related was found in Greenland Schley Fjord Formation Peary land 6 There is a further mention of the occurrence in Greenland for the late mudstone layer of the Upper Buen Formation 5 indicating that M hyperborea predated M svalbardensis Habitat editThe mudstone in which both species were found indicates deeper quiet waters 5 Ecology editMesolenellus hyperborea occurs together with Limniphacos perspiculum Serrodiscus hyoliths Petrianna fulmenta Bradoriida and inarticulate brachiopods 5 Description editAs with most early trilobites Mesolenellus has an almost flat exoskeleton that is only thinly calcified and has crescent shaped eye ridges As part of the suborder Olenellina Olenellus lacks dorsal sutures Like all other members of the superfamily Olenelloidea the eye ridges spring from the back of the frontal lobe L4 of the central area of the cephalon that is called glabella Mesolenellus also shares the typical character of the whole family Olenellidae that the frontal L3 and middle pair L2 of lateral lobes of the glabella are partially merged This creates two very typical isolated slits Mesolenellus is a genus within the Mesonacinae with eye ridges curved but almost parallel to the midline The back of the eye ridges is opposite the most backward ring of the glabella L0 or occipital ring Genal spines are 6 8 times as long as L0 The outer furrows of the glabella are parallel to the midline between the back of the cephalon and the furrow between side lobes L2 and L3 The thorax is 3 times as wide as the axis at the 3rd segment Mesolenellus can be distinguished from the sister genus Mesonacis where the back of the eye ridge extends only to the most backward side lobes L1 genal spines are only 1 5 times as long as L0 and the glabella widens forwards along L1 and L2 Except for in Mesonacis fremonti the curved eye ridges are at an angle of 15 20 with the midline A third genus Olenellus that constitutes the second subfamily of the family Olenellidae differs from Mesolenellus in having genal spines 4 5 times as long as L0 the glabella widens forwards along L1 and L2 and the thorax 4 4 times wider that the axis at the 3rd segment 1 Key to the species edit1 A short ridge called plectrum connects the frontal lobe of the glabella with the frontal border of the headshield The section of the border of the back of the head posterior cephalic border halfway between the midline and the genal angle between the axis and the intergenal angle has a backward angle The base of the genal spine is opposite the most backward ring of the glabella L0 The furrow between the 2nd and 3rd ring S2 does not contact the furrow that outlines the glabella or axial furrow 1 Nevadella zone Svalbard Vestspitsbergen Hornsund and Greenland Peary Land Schley Fjord Formation and Buen Formation M svalbardensis Kielan 1960 Plectrum absent The midsection of the posterior cephalic border is transverse The base of the genal spine is opposite the middle ring of the glabella L2 S2 contacts the axial furrow 1 Nevadella zone Greenland Buen Formation M hyperborea Poulsen 1974 References edit a b c d e f Lieberman B S 1999 Systematic Revision of the Olenelloidea Trilobita Cambrian PDF Bulletin of the Peabody Museum of Natural History 45 Archived from the original PDF on 2016 06 24 Retrieved 2012 10 30 Cowie J McNamara K J 1978 Olenellus Trilobita from the Lower Cambrian Strata of North West Scotland PDF Palaeontology 21 3 615 634 Archived from the original PDF on 2012 05 26 H B Whittington et al 1997 Introduction Order Agnostida Order Redlichiida Treatise on Invertebrate Paleontology Part O Revised Trilobita Poulsen V 1974 Olenellacean trilobites from eastern North Greenland Bulletin of the Geological Society of Denmark 23 79 101 a b c d Mark R Blaker amp John S Peel 1997 Lower Cambrian trilobites from North Greenland Meddelelser om Gronland Geoscience Vol 35 ISBN 978 87 635 1241 1 Kielan Z 1960 On two olenellid trilobites from Hornsund Vestspitsvergen Studia Geologica Polonica 4 133 139 External links editTrilobite info Retrieved from https en wikipedia org w index php title Mesolenellus amp oldid 1193422955, wikipedia, wiki, book, books, library,
