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Pachyrisma
Classification
Phylum:
Mollusca
Class:
Bivalvia
Subclass:
Heterodonta
Order:
Hippuritoida (rudists and relatives)
Superfamily:
Megalodontacea
Family:
Megalodontidae
Formal Genus Name and Reference:
Pachyrisma Morris & LYCETT, 1850, p. 399
Type Species:
P. grande, M
Images
(Click to enlarge in a new window)
Synonyms
Cardilla, Cardilia, Pachyerisma
Geographic Distribution
Eu.
Age Range
Beginning Stage in Treatise Usage:
L.Jur.
Beginning International Stage:
Hettangian
Fraction Up In Beginning Stage:
0
Beginning Date:
201.36
Ending Stage in Treatise Usage:
U.Jur.
Ending International Stage:
Tithonian
Fraction Up In Ending Stage:
100
Ending Date:
143.1
Description
Medium-sized to large, equivalve, thick-shelled, ovate to subtrigonal, with strongly prosogyrous, more or less anteriorly placed beaks, valves carinate posteriorly, hinge plate, ligamental nymph and teeth heavy, single strong, mesially placed cardinal in LV received in recess between strong posterior cardinal and weak (in some specimens ill-defined) anterior cardinal in RV, well-developed, tuberculiform lateral tooth present near each end of hinge plate in LV and received in sockets above corresponding laterals in RV, anterior adductor scar deep, situated just below anterior lateral tooth
References
Museum or Author Information
Classification
Phylum:
Mollusca
Class:
Bivalvia
Subclass:
Heterodonta
Order:
Hippuritoida (rudists and relatives)
Superfamily:
Megalodontacea
Family:
Megalodontidae
Formal Genus Name and Reference:
Pachyrisma Morris & LYCETT, 1850, p. 399
Type Species:
P. grande, M
Images
(Click to enlarge in a new window)Synonyms
Cardilla, Cardilia, Pachyerisma
Geographic Distribution
Eu.
Age Range
Beginning Stage in Treatise Usage:
L.Jur.
Beginning International Stage:
Hettangian
Fraction Up In Beginning Stage:
0
Beginning Date:
201.36
Ending Stage in Treatise Usage:
U.Jur.
Ending International Stage:
Tithonian
Fraction Up In Ending Stage:
100
Ending Date:
143.1
Description
Medium-sized to large, equivalve, thick-shelled, ovate to subtrigonal, with strongly prosogyrous, more or less anteriorly placed beaks, valves carinate posteriorly, hinge plate, ligamental nymph and teeth heavy, single strong, mesially placed cardinal in LV received in recess between strong posterior cardinal and weak (in some specimens ill-defined) anterior cardinal in RV, well-developed, tuberculiform lateral tooth present near each end of hinge plate in LV and received in sockets above corresponding laterals in RV, anterior adductor scar deep, situated just below anterior lateral tooth