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Micragnostus
Classification
Phylum:
Unknown
Class:
Trilobata
Order:
Agnostida
Superfamily:
Agnostoidea
Family:
Agnostidae
Formal Genus Name and Reference:
Micragnostus HOWELL, 1935b, p. 233
Type Species:
Agnostus calvus Lake, 1906, p. 23, OD, lectotype (Lake, 1906, pl. 2, fig. 18, SD FORTEY, 1980b, p. 23), A548, SM, Cambridge
Images
(Click to enlarge in a new window)
Fig. 219,4. *M. calvus (L AKE ), Lower Ordovician (Tremadoc), northern Wales (Nant Rhos Ddu); lectotype, SM A548, ×10 (new).
Synonyms
Geographic Distribution
Wales, Spitsbergen, Asaphellus–D. bifidus Zones; Argentina, N. argentina–K. meridionalis Zones; Sweden, M. dalecarlicus Zone.
Age Range
Beginning Stage in Treatise Usage:
Upper Cambrian
Beginning International Stage:
Guzhangian
Fraction Up In Beginning Stage:
0
Beginning Date:
498.75
Ending Stage in Treatise Usage:
Lower Ordovician (Arenig)
Ending International Stage:
Floian
Fraction Up In Ending Stage:
0
Ending Date:
471.26
Description
En grande tenue, nonscrobiculate, border furrows nondeliquiate, acrolobes unconstricted, median preglabellar furrow absent. Glabella with semiovate anterior lobe, F3 straight, posterior lobe parallel-sided with F2 weakly developed or absent, glabellar culmination broadly rounded, glabellar node level with or slightly behind F2. Basal lobes small. Pygidium minutely bispinose, axis relatively short, unconstricted or weakly constricted over M2, M1 trilobate, F1 traversing axis, F2 well impressed, slightly deflected by axial node. Posterior lobe semiovate. Median postaxial furrow absent.
References
Museum or Author Information
Classification
Phylum:
Unknown
Class:
Trilobata
Order:
Agnostida
Superfamily:
Agnostoidea
Family:
Agnostidae
Formal Genus Name and Reference:
Micragnostus HOWELL, 1935b, p. 233
Type Species:
Agnostus calvus Lake, 1906, p. 23, OD, lectotype (Lake, 1906, pl. 2, fig. 18, SD FORTEY, 1980b, p. 23), A548, SM, Cambridge
Images
(Click to enlarge in a new window)
Fig. 219,4. *M. calvus (L AKE ), Lower Ordovician (Tremadoc), northern Wales (Nant Rhos Ddu); lectotype, SM A548, ×10 (new).
Synonyms
Geographic Distribution
Wales, Spitsbergen, Asaphellus–D. bifidus Zones; Argentina, N. argentina–K. meridionalis Zones; Sweden, M. dalecarlicus Zone.
Age Range
Beginning Stage in Treatise Usage:
Upper Cambrian
Beginning International Stage:
Guzhangian
Fraction Up In Beginning Stage:
0
Beginning Date:
498.75
Ending Stage in Treatise Usage:
Lower Ordovician (Arenig)
Ending International Stage:
Floian
Fraction Up In Ending Stage:
0
Ending Date:
471.26
Description
En grande tenue, nonscrobiculate, border furrows nondeliquiate, acrolobes unconstricted, median preglabellar furrow absent. Glabella with semiovate anterior lobe, F3 straight, posterior lobe parallel-sided with F2 weakly developed or absent, glabellar culmination broadly rounded, glabellar node level with or slightly behind F2. Basal lobes small. Pygidium minutely bispinose, axis relatively short, unconstricted or weakly constricted over M2, M1 trilobate, F1 traversing axis, F2 well impressed, slightly deflected by axial node. Posterior lobe semiovate. Median postaxial furrow absent.