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Zygospira
Classification
Phylum:
Brachiopoda
Class:
Rhynchonellata
Order:
Atrypida
Superfamily:
Anazygoidea
Family:
Anazygidae
Formal Genus Name and Reference:
Zygospira HALL, 1862, p. 154
Type Species:
Producta modesta Say in HALL, 1847, p. 141, OD
Images
(Click to enlarge in a new window)
Fig. 976, 1a-h. *Z. modesta (SAY), middle'
Synonyms
Pusillagutta
Geographic Distribution
worldwide
Age Range
Beginning Stage in Treatise Usage:
Ordovician (Caradoc)
Beginning International Stage:
Sandbian
Fraction Up In Beginning Stage:
0
Beginning Date:
458.18
Ending Stage in Treatise Usage:
Ordovician (Ashgill)
Ending International Stage:
Hirnantian
Fraction Up In Ending Stage:
100
Ending Date:
443.07
Description
Small, ventribiconvex-planoconvex; ventral valve strongly to weakly carinate; weakly sulcate dorsal valve; long hinge; small orthocline-anacline area; minute beak; apical-transapical foramen; deltidial plates minute to absent; ribs medium (coarse ribs on ventral carina), expanding distally, generally nonbifurcating; growth interruptions common, rare, slightly overlapping anterior growth lamellae; commissure sulcate; interior thinly walled; minute, medially directed teeth with dental cavities; brachidia delicate; crura small, laterally directed; spiralia dorsomedially directed with fewer than 8 whorls, filling much of shell interior; jugum posteromedial to dorsal, in mid-anterior of shell. [Distinguished from Anazyga by wider hinge line, carination, coarser ribs, and dorsomedially directed spiralia.]
References
Museum or Author Information
Classification
Phylum:
Brachiopoda
Class:
Rhynchonellata
Order:
Atrypida
Superfamily:
Anazygoidea
Family:
Anazygidae
Formal Genus Name and Reference:
Zygospira HALL, 1862, p. 154
Type Species:
Producta modesta Say in HALL, 1847, p. 141, OD
Images
(Click to enlarge in a new window)
Fig. 976, 1a-h. *Z. modesta (SAY), middle'
Synonyms
Pusillagutta
Geographic Distribution
worldwide
Age Range
Beginning Stage in Treatise Usage:
Ordovician (Caradoc)
Beginning International Stage:
Sandbian
Fraction Up In Beginning Stage:
0
Beginning Date:
458.18
Ending Stage in Treatise Usage:
Ordovician (Ashgill)
Ending International Stage:
Hirnantian
Fraction Up In Ending Stage:
100
Ending Date:
443.07
Description
Small, ventribiconvex-planoconvex; ventral valve strongly to weakly carinate; weakly sulcate dorsal valve; long hinge; small orthocline-anacline area; minute beak; apical-transapical foramen; deltidial plates minute to absent; ribs medium (coarse ribs on ventral carina), expanding distally, generally nonbifurcating; growth interruptions common, rare, slightly overlapping anterior growth lamellae; commissure sulcate; interior thinly walled; minute, medially directed teeth with dental cavities; brachidia delicate; crura small, laterally directed; spiralia dorsomedially directed with fewer than 8 whorls, filling much of shell interior; jugum posteromedial to dorsal, in mid-anterior of shell. [Distinguished from Anazyga by wider hinge line, carination, coarser ribs, and dorsomedially directed spiralia.]