Agnostus pisiformis, from here.

Belongs within: Agnostida.

The Agnostinae are a group of agnostids known from the Middle Cambrian to Early Ordovician, characterised by a simple, axiolobate pygidium (Shergold et al. 1990).

Characters (from Shergold et al. 1990): En grande tenue to largely effaced, nondeliquiate to deliquiate border furrows; acrolobes usually unconstricted; preglabellar median furrow absent to well developed. Glabella with large ogival, semiovate, subpentagonal, subquadrate or trapeziform anterior lobe; F3 straight to concave forward; F2 absent to well developed; glabellar culmination variably rounded, subquadrate or obtusely angular; glabellar node from midway between Fl and F2 to level with F2; basal lobes variable in size, usually simple, occasionally incorporating lateral portions of M2 lobe. Pygidium bispinose or nonspinose, with agnostoid or basic articulating device; axis usually long, not reaching border furrow, with a slight constriction across M2; Fl variably impressed, rarely effaced; Ml usually trilobate; F2 variably impressed, rarely effaced; posterior lobe usually long, semiovate, ogival, semicircular or bulbous, with or without terminal node.

    |--Oxyagnostus S80
    |--Innitagnostus Öpik 1967 S80
    |    |--*I. innitens Öpik 1967 S80
    |    |--I. inexpectans S80
    |    `--I. medius Shergold 1980 S80
    |--Lotagnostus S80
    |    |  i. s.: L. trisectus S80
    |    `--L. (Trilobagnostus) S80
    |         |--L. (T.) ergodes Shergold 1972 S80
    |         `--L. (T.) irretitus Shergold 1975 S80
    |--Acmarhachis Resser 1938 [incl. Cyclagnostus Lermontova 1940] S80
    |    |--*A. typicalis Resser 1938 S80
    |    |--A. acuta (Kobayashi 1938) [=Homagnostus acutus, A. acutus (l. c.)] S80
    |    |--‘Cyclagnostus’ elegans Lermontova 1940 S80
    |    |--A. hybrida Shergold 1980 S80
    |    `--A. quasivespa (Öpik 1967) HLC03, S80 [=Cyclagnostus quasivespa S80]
    `--Agnostus Brongniart 1821 W77
         |--A. czekanowskii T10
         |--A. gibbus A38
         |--A. integer W77
         |--A. interstrictus White 1874 W77
         `--A. pisiformis A38
              |--A. p. pisiformis A38
              `--A. p. obesus A38

*Type species of generic name indicated


[A38] Alcock, F. J. 1938. Geology of Saint John region, New Brunswick. Geological Survey of Canada Memoir 216: 1-65.

[HLC03] Hong, P. S., J. G. Lee & D. K. Choi. 2003. Trilobites from the Lejopyge armata zone (upper Middle Cambrian) of the Machari Formation, Yongwol Group, Korea. Journal of Paleontology 77 (5): 895-907.

[S80] Shergold, J. H. 1980. Late Cambrian trilobites from the Chatsworth Limestone, western Queensland. Bureau of Mineral Resources, Geology and Geophysics—Bulletin 186: 1-111.

Shergold, J. H., J. R. Laurie & Sun X. 1990. Classification and review of the trilobite order Agnostida Salter, 1864: an Australian perspective. Bureau of Mineral Resources, Geology and Geophysics—Report 296.

[T10] Taylor, T. G. 1910. The Archaeocyathinae from the Cambrian of South Australia with an account of the morphology and affinities of the whole class. Memoirs of the Royal Society of South Australia 2 (2): 55-188.

[W77] White, C. A. 1877. Report upon the invertebrate fossils collected in portions of Nevada, Utah, Colorado, New Mexico, and Arizona, by parties of the expeditions of 1871, 1872, 1873, and 1874. U.S. Geographical Surveys West of the One Hundredth Meridian 4 (1): 1-219, pls 211-221.

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