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Hesperonomia
Classification
Phylum:
Brachiopoda
Class:
Rhynchonellata
Order:
Orthida
Superfamily:
Orthoidea
Family:
Hesperonomiidae
Formal Genus Name and Reference:
Hesperonomia Ulrich & COOPER, 1936b, p. 621
Type Species:
H. planidorsalis, OD
Images
(Click to enlarge in a new window)
Fig. 532, 1a-d. *H. planidorsalis, Tremadoc, Alberta; a, ventral interior, ×2; b, dorsal interior, ×2; c, details of cardinalia, ×4; d, dorsal exterior, ×2 (Ulrich & Cooper, 1938).
Synonyms
Geographic Distribution
North America, Siberia, Great Britain, South America (Argentina), France, central Asia, China
Age Range
Beginning Stage in Treatise Usage:
Lower Ordovician (Tremadoc)
Beginning International Stage:
Tremadocian
Fraction Up In Beginning Stage:
0
Beginning Date:
486.85
Ending Stage in Treatise Usage:
Lower Ordovician (Arenig)
Ending International Stage:
Floian
Fraction Up In Ending Stage:
100
Ending Date:
471.26
Description
An elongately semioval brachiopod genus with acute cardinal extremities and a concavoconvex shell. It has a short, flat apsacline ventral interarea and deltidiodont teeth with recessive dental plates. The ventral muscle field is subcordate with an undifferentiated adductor muscle track not enclosed by diductor scars. The notothyrial platform bears notothyrial ridges fused with a simple cardinal process and extends anteriorly as a median ridge, with rodlike divergent brachiophores. The dorsal adductor muscle scar is vaguely impressed.
References
Museum or Author Information
Classification
Phylum:
Brachiopoda
Class:
Rhynchonellata
Order:
Orthida
Superfamily:
Orthoidea
Family:
Hesperonomiidae
Formal Genus Name and Reference:
Hesperonomia Ulrich & COOPER, 1936b, p. 621
Type Species:
H. planidorsalis, OD
Images
(Click to enlarge in a new window)
Fig. 532, 1a-d. *H. planidorsalis, Tremadoc, Alberta; a, ventral interior, ×2; b, dorsal interior, ×2; c, details of cardinalia, ×4; d, dorsal exterior, ×2 (Ulrich & Cooper, 1938).
Synonyms
Geographic Distribution
North America, Siberia, Great Britain, South America (Argentina), France, central Asia, China
Age Range
Beginning Stage in Treatise Usage:
Lower Ordovician (Tremadoc)
Beginning International Stage:
Tremadocian
Fraction Up In Beginning Stage:
0
Beginning Date:
486.85
Ending Stage in Treatise Usage:
Lower Ordovician (Arenig)
Ending International Stage:
Floian
Fraction Up In Ending Stage:
100
Ending Date:
471.26
Description
An elongately semioval brachiopod genus with acute cardinal extremities and a concavoconvex shell. It has a short, flat apsacline ventral interarea and deltidiodont teeth with recessive dental plates. The ventral muscle field is subcordate with an undifferentiated adductor muscle track not enclosed by diductor scars. The notothyrial platform bears notothyrial ridges fused with a simple cardinal process and extends anteriorly as a median ridge, with rodlike divergent brachiophores. The dorsal adductor muscle scar is vaguely impressed.