Lonchodomas

{{Short description|Extinct genus of trilobites}} {{Automatic taxobox | fossil_range = {{temporal_range|472|443|Ordovician}} | image = Lonchodomas mcgeheei CRF.jpg | image_caption = ''L. mcgeheei'', Bromide Formation, Oklahoma | taxon = Lonchodomas | authority = Angelin, 1854 | type_species = ''Ampyx rostrata'' | subdivision_ranks = Species | subdivision = * ''L. rostratus'' (Sars, 1835) * ''L. carinatus'' Cooper, 1953 * ''L. clavulus'' Whittington, 1965 * ''L. mcgeheei'' (Decker, 1931) synonym ''Ampyx mcgeheei'' * ''L. retrolatus'' Ross jr. & Barnes, 1967 * ''L. suriensis'' Harrington & Leanza, 1957 * ''L. volborthi'' (Schmidt, 1894) synonym ''Ampyx volborthi'' }}

'''''Lonchodomas''''' is a genus of trilobites, that lived during the Ordovician. It was eyeless, like all raphiophorids, and had a long straight sword-like frontal spine, that gradually transforms into the relatively long glabella. Both the glabellar spine and the backward directed genal spines are subquadrate in section. ''Lonchodomas'' has five thorax segments and the pleural area of the pygidium has two narrow furrows. ''Lonchodomas'' occurred in what are today Argentina, Canada (Newfoundland), Estonia, Latvia, Norway, Sweden, the Russian Federation (Leningrad Oblast<ref name="Krylov2003">A.V. Krylov (2003). "[https://www.researchgate.net/publication/339460347_New_data_on_trilobites_from_Hecker_mud_mounds_Ordovician_in_the_Leningrad_region New data on trilobites from Hecker mud mounds (Ordovician) in the Leningrad region (in Russian)]". ''Vestnik Sankt-Petersburgskogo Universiteta, Seriya Geologiya i Geografiya'' 3(33):95-96</ref>) and the United States (Oklahoma, Virginia).

== Distribution == left|thumb|''Lonchodomas suriensis'', 4 mm long * ''L. carinatus'' is found in the Upper Ordovician of the United States (Lower Member and Botetourt limestone Member, of the Edinburgh Formation, Shenandoah County, Virginia, 39.0° N, 78.4° W Blackriveran 460.9 - 449.5 Ma)<ref>{{cite journal|last1= Whittington|first1= H. B.|last2= I.I. Evitt|first2= W.R.|year= 1953|title= Silicified Middled Ordovician trilobites|journal= Geological Society of America Memoirs |volume= 59|pages= 1–139|doi=10.1130/mem59-p1}} cited in {{cite web|title= 73341|website= Paleobiology Database|url= https://paleobiodb.org/classic/displayCollResults?collection_no=73341}}</ref> * ''L. clavulus'' is present in the Middle Ordovician of Newfoundland, Canada (''Histiodella kristinae'' conodont zone, Table Cove Formation; Table Point, "Middle Table Head" and Table Cove).<ref>{{cite journal|last1= Whittington|first1= H. B. |last2= Kindle.|first2= C.H.|year= 1963|title= Middle Ordovician Table Head Formation, western Newfoundland|journal= Geological Society of America Bulletin|volume= 74|issue= 6 |pages= 745–758|doi=10.1130/0016-7606(1963)74[745:mothfw]2.0.co;2|bibcode= 1963GSAB...74..745W }} cited in {{cite web|title= 104800|website= Paleobiology Database|url= https://paleobiodb.org/classic/displayCollResults?collection_no=104800}}</ref> * ''L. mcgeheei'' is present in the Upper Ordovician of Oklahoma, United States (Bromide Formation, Sandbian).<ref>{{cite journal|last= Decker|first= C.E.|year= 1939|title= Genal spine attached to Ampyx (Lonchodomas) mcgeheei|journal= Journal of the Academy of Science|pages= 107–108|url= http://digital.library.okstate.edu/oas/oas_pdf/v20/p107.pdf}}</ref> * ''L. retrolatus'' was collected from the Ordovician of Nevada (Eureka Quartzite, sandy limestone, 60–90 ft above base, Ranger Mountains, Nevada Test Site))<ref>{{cite journal|last1= Ross|first1= R.J. jr.|year= 1967|title= Brachiopods and Trilobites from the Basin Ranges, Western United States|journal= Contributions to Paleontology|volume= Geological Survey Professional Paper 523-D|url= https://pubs.usgs.gov/pp/0523d/report.pdf}}</ref> * ''L. rostratus'' is known from the Upper Ordovician of Estonia (Narva open pit, and Lasnamägi, Kukruse Stage, Sandbian) and Latvia (Remte 3 borehole, and Adze 6 borehole, Kukruse Stage, Sandbian).<ref>{{cite web|url= http://fossiilid.info/?id=3497 |title= Species Lonchodomas rostratus (Sars, 1835)|website= Baltoscandian fossils|publisher= Tallinn University of Technology, University of Tartu, Finnish Museum of Natural History, Swedish Museum of Natural History|accessdate=14 September 2013}}</ref> * ''L. suriensis'' was excavated from the Middle Ordovician of Argentina (Portillo del Cajón, Cerro Morado; Cerro Suri; Puesto El Despacho; Las Pircas; all La Rioja)<ref>{{cite book|last1= Harrington|first1= H.J.|last2= Leanza|first2= A.F.|year= 1957|title= Ordovician trilobites of Argentina|series= Department of Geology, University of Kansas Special Publication|location= Lawrence|publisher= University of Kansas Press|pages= 1–276}} cited in {{cite web|title= Lonchodomas suriensis occurrences listing|website= Paleobiology Database|publisher= Macquarie University|access-date=1 October 2013|url= https://paleodb.org/?a=displayCollResults&taxon_no=198580&max_interval=Ordovician&country=Argentina&is_real_user=1&basic=yes&type=view&match_subgenera=1}}</ref> * ''L. volborthi'' occurs in the Lower Ordovician of the Russian Federation (Volkhovian level, Syas River, Putilovo and Babino quarries, St.Petersburg region).<ref name="Krylov2003" /> It was originally described as ''Ampyx volborthi'' but assigned to ''Lonchodomas'' in 1952 by Steinar Skjeseth.<ref>Steinar Skjeseth, 1952. "[https://njg.geologi.no/images/NJG_articles/NGT_30_138-182.pdf On the lower Didymograptus zone (3B) at Ringsaker, and contemporaneous deposits in Scandinavian]": ''Norsk geol. tidsskr''., v. 30, p. 138 — 182.</ref>

== Description == Like all raphiophorids, ''Lonchodomas'' is eyeless. The headshield (or cephalon) and tailshield (or pygidium) are subtriangular in outline. ''Lonchodomas'' looks a lot like Ampyx but the glabella is diamond-shaped in outline, and it has a ridge along the midline (it is carinate). The glabella gradually transforms into the spine, which makes it difficult to determine where the spine begins. The long median glabellar spine is subquadrate in section and is directed horizontally forward, from the frontal tip of the glabella. The glabella has 2 pairs of muscle scars. The genal spines are also subquadrate in section. The thorax has 5 segments. The pleural regions of pygidium have 2 pairs of narrow pleural furrows.<ref name=Treatise59>{{Citation |editor-last=Moore |editor-first=R. C. |title=Treatise on Invertebrate Paleontology, Part O, Arthropoda 1, Trilobita |pages=''xix'' + 560 pp., 415 figs |publisher=The Geological Society of America & The University of Kansas Press|place=Boulder, CO & Lawrence, KA |year=1959 |isbn=0-8137-3015-5}}</ref>

== References == {{Reflist|30em}}

Category:Raphiophoridae Category:Asaphida genera Category:Ordovician trilobites Category:Fossils of Argentina Category:Fossils of Estonia Category:Fossils of Latvia Category:Fossils of Norway Category:Fossils of Russia Category:Fossils of the United States Category:Bromide Formation Category:Paleozoic life of Newfoundland and Labrador Category:Paleozoic life of the Northwest Territories Category:Paleozoic life of Quebec Category:Paleozoic life of Yukon