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Acrotreta
Classification
Phylum:
Brachiopoda
Class:
Lingulata
Order:
Acrotretida
Superfamily:
Acrotretoidea
Family:
Acrotretidae
Formal Genus Name and Reference:
Acrotreta KUTORGA, 1848, p. 275
Type Species:
A. subconica, SD DAVIDSON, 1853, p. 133
Images
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Fig. 52, 1a-g. *A$. subconica, Billingen Stage, $a, b$, ventral valve, posterior view, lateral view, Päite beds, Lava River, Vassilkovo, Ingria, Russia, CNIGR 134/9960, X8.3 (Gorjansky, 1969), $c$, dorsal valve exterior, x13.8, d$, oblique lateral view of dorsal valve, x16.2$, $e$, detail of pitted ornamentation of dorsal larval shell, Päite beds, Mäekalda, Tallinn, Estonia, RMS Br 133894 , X1133, $f$, ventral valve interior, Mäeküla beds, Mäeküla, Estonia, RMS Br 133890, X9.2, g, dorsal valve interior, Päite beds, Mäekalda, Tallinn, Estonia, RMS Br 133895, X1 1.2 (Holmer & Popov, 1994).’
Synonyms
Geographic Distribution
Bohemia, ?Tremadoc, Arenig; Poland, Arenig; Estonia, Russia (Ingria, Southern Urals), Sweden, Arenig-Llanvirn; USA, Alabama, Llandeilo
Age Range
Beginning Stage in Treatise Usage:
Ordovician (?Tremadoc)
Beginning International Stage:
Tremadocian
Fraction Up In Beginning Stage:
0
Beginning Date:
486.85
Ending Stage in Treatise Usage:
Ordovician (Llandeilo)
Ending International Stage:
Darriwilian
Fraction Up In Ending Stage:
100
Ending Date:
458.18
Description
Shell finely pustulose with a wide posterior margin, ventral valve highly conical, pseudointerarea well defined, apsacline to catacline or weakly procline, foramen not enclosed within larval shell, dorsal pseudointerarea with a wide median groove and propareas, apical process forming a high septum and muscular platform, perforated by a pedicle tube that usually occupies more than half valve height, strongly impressed pinnate mantle canals, with three pairs of trunks, dorsal interior with a triangular median septum, median buttress