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Bkell: plural of "shelf" is "shelves"

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plural of "shelf" is "shelves"

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{{Taxobox
| fossil_range = {{Geological range|493|491|Upper Cambrian (upper [[Sunwaptan]])}}
| regnum = [[Animal]]ia
| phylum = [[Arthropod]]a
| classis = [[Trilobita]]
| ordo = [[Agnostida]]
| familia = [[Agnostidae]]
| subfamilia = [[Agnostinae]]
| genus = '''''Lotagnostus'''''
| genus_authority = [[Frederick William Whitehouse|Whitehouse]], 1936
| subdivision_ranks = [[species]]
| subdivision =
* ''L. trisectus'' ([[John William Salter|Salter]], 1864) ([[Type (biology)|type]]) [[synonym]] ''Agnostus trisectus''
* ''L. americanus'' ([[Elkanah Billings|Billings]], 1860) synonym ''Agnostus americanus''
* ''L. asiaticus'' [[Gustaf Troedsson|Troedsson]], 1937 possible synonym ''L. spectabilis''
* ''L. attenuatus'' Rusconi, 1955
* ''L. ergoides'' Shergold, 1972
* ''L. germanicus'' (Matthew, 1901) synonym ''Agnostus trisectus germanicus''
* ''L. hedeni'' (Troedsson, 1937) synonym ''Agnostus hedeni''
* ''L. irretinus'' Shergold, 1975
* ''L. obscurus'' [[Allison R. Palmer|Palmer]], 1955)
* ''L. peladensis'' Rusconi, 1951
* ''L. punctuatus'' Lu, 1964
}}

'''''Lotagnostus''''' is a genus of very small [[trilobite]]s in the order [[Agnostida]], which lived on the outer [[continental shelf|continental shelves]] worldwide, during the late Upper [[Cambrian]]. It was described by Whitehouse in 1936, and the type species is ''Lotagnostus trisectus'', which was originally described as a species of ''[[Agnostus]]'' by Salter in 1864.<ref>[http://www.trilobites.info/generic_names_Jell%26Adrain2003.pdf Available Generic Names for Trilobites] P.A. Jell and J.M. Adrain.</ref>

== Taxonomy ==
The [[Treatise on Invertebrate Paleontology]]<ref>{{cite book|last1= Shergold|first1= J.H.|last2= Laurie|first2= J.R.|year= 1997|chapter= Introduction to the Suborder Agnostina|title= Treatise on Invertebrate Paleontology, Part O., Revised|volume= 1. Introduction, Order Agnostina, Order Redlichiida|editor= H.B. Whittington|publisher= University of Kansas/Geological Society of America Inc.|location= Lawrence, Kansas|display-editors=etal}}</ref> divides ''Lotagnostus'' into three subgenera that differ in the degree of effacement: ''L. (Lotagnostus)'' Whitehouse, 1936 (neither cephalon nor pygidium strongly effaced), ''L. (Distagnostus)'' Shergold, 1972 (strongly effaced on the outer/dorsal surface, but with clear furrows on the inner/ventral surface and ''L. (Eolotagnostus)'' Zhou ''in'' Zhiqiang Zhou, li & Qu, 1982 (with even the inner/ventral surface strongly effaced). Later authors however consider it likely that creating these subgenera would render the [[Subspecies#Nominotypical subspecies and subspecies autonyms|nominate subgenus]] [[paraphyly|paraphyletic]].<ref name='WAL'>{{cite journal|last1=Westrop|first1= S,R.|last2= Adrian|first2= J.M.|last3= Landing|first3=E.|year=2011|title= The Cambrian (Sunwaptan, Furongian) agnostoid arthropod ''lotagnostus'' Whitehouse, 1936, in Laurentian and Avalonian North America: systematics and biostratigraphic significance|journal= Bulletin of Geosciences|volume= 86|issue= 3|pages= 569–594|url= http://www.geology.cz/bulletin/fulltext/1256_Westrop.pdf|accessdate= 10 June 2–13|doi=10.3140/bull.geosci.1256}}</ref>

== Biostratographic significance ==
The [[first appearance datum]] (FAD) of ''Lotagnostus americanus'' has been proposed to define the lower limit of [[Cambrian Stage 10]].<ref>{{cite journal|last1= Lazarenko|first1= N.P.|last2= Gogin| first2= I.Y.|last3= Pegel|first3= T.V.|last4= Abiamova|first4= G.P.|year= 2011|title= The Khos-Nelege River section of the Ogon’or Formation: a potential candidate for the GSSP of Stage 10, Cambrian System|journal= Bulletin of Geosciences|volume= 86|issue= 3|pages= 555–568|url= http://www.geology.cz/bulletin/fulltext/1270%20Lazarenko.pdf|accessdate= 12 June 2013|doi=10.3140/bull.geosci.1270}}</ref> This proposition is based on the interpretation that ''L. americanus'' is a [[Polymorphism (biology)|polymorph]] species with a global distribution, a concept that included ''L. obscurus'', and ''Agnostus trisectus'', the [[Type (biology)|type]] of ''Lotagnostus''. Recently however, the North American species of ''Lotagnostus'' have been revised and it was concluded that ''L. americanus'' in fact shows little variation and has a limited spatial distribution, and the variants from other locations belong to several other ''Lotagnostus'' species.<ref name='WAL'/> This renders ''L. americanus'' unfit as [[index fossil]] for the lower limit of Cambrian Stage 10. As alternatives the FADs of the conodonts ''[[Cordylodus]] andresi'' and ''[[Eoconodontus]] notchpeakensis'' have been suggested.<ref name='WAL'/>

== Distribution ==
* '''''L. trisectus''''' is known from the late Upper Cambrian of Canada (MacNeil Brook, Middle Chesley Drive Group, Nova Scotia), England (White Leaved Oak Shale, Malvern, Gloucestershire), Wales (Cwmhesgen formation) and Sweden (Andrarum).
* '''''L. americanus''''' occurs at the late Upper Cambrian of Canada (in boulders in conglomerates of the Léwis Formation, North Ridge, near Léwis, Quebec).
* '''''L. asiaticus''''' has been found in the late Upper Cambrian of China (Kuruktagh, Xinjiang)
* '''''L. germanicus''''' is known from the late Upper Cambrian of Canada (North shore of East Bay, near Eskasoni, Cape Breton Island, Middle Chesley Drive Group, Nova Scotia)
* '''''L. hedeni''''' occurs at the late Upper Cambrian of China (Kuruktagh, Xinjiang; Siyangshan Formation, western Zhejiang), Kazakhstan (''Euloma limitaris-Taoyuania'' zone) and Canada (''Phylacterus saylesi'' fauna, Shallow Bay Formation, western Newfoundland)
* '''''L. obscurus''''' is present in the late Upper Cambrian of the United States (Pogonip Limestone, Windfall formation, near Hamburg Shaft, Eureka District, Nevada))
* '''''L. peladensis''''' is known from the late Upper Cambrian of Argentina (Precordillera)
* '''''L. punctuatus''''' has been found in the late Upper Cambrian of China (Zejiang; elsewhere in Southeastern China) and Kazakhstan.
''Lotagnostus'' is also present in Siberia (Ogon'or Formation along the Khos-Negele River), but its assignment to a particular species is difficult.

== Description ==
Like all Agnostida, ''Lotagnostus'' is diminutive, with the headshield (or [[Cephalon (arthropod head)#Trilobites|cephalon]]) and tailshield (or [[pygidium]]) of approximately the same size (or [[Pygidium#Trilobites|isopygous]]) and outline. Like all Agnostina, ''Lotagnostus'' has only two thorax segments. The species are characterized by variable stages of effacement, more so on the outer/dorsal surface compared to the inner/ventral surface. This may complicate distinction from effaced species in other genera. The frontal lobe the central raised area of the cephalon (or [[Cephalon (arthropod head)#Trilobites|glabella]]) is long at about ⅓ or more of the length of the glabella. The basal lobes at the rear of the glabella are narrow triangular and equal in length to the frontal lobe. The central part of the glabella has two side lobes. Opposite the tip of the side lobes there is a node on the midline. There is a furrow at midline connecting the glabella with the border furrow. The axis of the pygidium (or rhachis) has three sections. The frontal section is split into three parts. Both lateral parts are defined by furrows on all sides: those with the central section directed backward and very slightly outward, those with the middle section outward and slightly backward, and those with the pleural zone backward and slightly inward. The middle part is merged with the central section. The middle part carries a node. The furrow between the central and rear parts is transverse, and those with the pleural zone backward and slightly inward. The rear part is about twice as long as the frontal and central parts individually. The surrounding axial furrow is directed outward, than strongly bends backward and than curves regularly ever more inward. Over the posterior ⅔ of the rear part a strip about as wide as the node on the central part may be discernible, which ends in a node that at the very rear of the rhachis. The distance between the rhachis and the border furrow (or post axial length) is about equal to ¼ of the rhachis. The pygidial border is about ⅛ of the rhachis. Opposite to the rear of the rhachis the border may carry a small spine at each side.<ref name='WAL'/>

==References==
{{reflist}}
{{Portal|Paleontology}}

[[Category:Agnostida]]
[[Category:Cambrian trilobites]]
[[Category:Fossils of Canada]]
[[Category:Fossils of the United Kingdom]]
[[Category:Fossils of China]]
[[Category:Fossils of Sweden]]
[[Category:Fossils of Russia]]
[[Category:Fossils of Argentina]]
[[Category:Fossils of Kazakhstan]]
[[Category:Fossils of the United States]]
[[Category:Paleontology in Nova Scotia]]
[[Category:Paleontology in Quebec]]
[[Category:Paleontology in Newfoundland and Labrador]]

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Bkell: plural of "shelf" is "shelves"