Nemagraptus is an extinct genus of graptolites which had an almost worldwide distribution during the Darriwilian and Sandbian (Ordovician). Two species are known: N. gracilis and N. subtilis.
History Nemagraptus gracilis was first collected from the Hudson River Shale and Normanskill Formation of New York State in 1843, and Hall (1847) assigned the species to Graptolithus as G. gracilis using specimen YPM IP 020351 as the paralectotype and specimen AMNH 30458 as the lectotype.Hall, J. (1847). Natural History of New York, Pt. VI, Paleontology of New York, 1. Albany, New York, 338 p. Emmons (1855) created the genus Nemagraptus for another species, N. elegans.Emmons, E. (1855). American Geology, 1, Pt. 1. Albany, New York, 194 p.Google Scholar Törnquist identified the first record of N. gracilis in Europe in 1865,Törnquist, S.L. (1865). Geologiska Jakttagelser öfver Fågelsångstraktens undersiluriska lager. Lunds Universitets Årsskrift.Törnquist, S. L. Descriptions of Ordovician graptolites from Baltoscandia, 1901 & 1904. and Elles and Wood (1904) moved G. gracilis into Nemagraptus, synonymising N. elegans with N, gracilis in the process.Elles, G. L., and Wood, E. M. R. (1904). A monograph of British graptolites. Palaeontographical Society, London, 4:135–180.Google Scholar Three-dimensional remains belonging to N. gracilis were identified in 2007 from boreholes across Latvia and Estonia.
Hadding (1913) named and described Nemagraptus subtilis as the second species assigned to the Nemagraptus genus. He identified the species based on specimens found in the Dicellograptus shale sequence in Skåne County, Sweden between 1910 and 1912.Hadding, A. (1913). Undre Dicellograptusskiffern i Skåne. Lunds Universitets Årsskrift, 9(15):1–91.
Starting with Bergström et al. (2000), the lower boundary of the Sandbian was defined as the first appearance datum of N. gracilis in that section.
Distribution Nemagraptus has been identified from: Argentina, Bolivia, Canada, China, Czech Republic, England, Estonia, Kazakhstan, Latvia, New Zealand, Peru, Sweden, the United States, and Wales.J. J. Sepkoski, Jr. (2002). A compendium of fossil marine animal genera. Bulletins of American Paleontology 363:1-560
Description It lived in deep water environments. The thecae possess considerable overlap, and it has isolated metasicula as the main synapomorphy.
Nemagraptus was a colony-forming organism with two s-shaped branches, which in turn split into several short branches.Frank H.T. Rodes, Herbert S. Zim and Paul R. Shaffer (1993) - Nature Guide Fossils (the origin, preparation and arrangement of fossils), Zuidnederlandse Uitgeverij N.V., Aartselaar. ISBN D-1993-0001-361
Classification Nemagraptus is a graptolite and has been classified into the family Dicranograptidae and the subfamily Nemagraptinae.
References