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Himalayan Geology, Vol. 31
(1), 2010, pp. 51-69, Printed in India
Classification of species of larger foraminiferal genus Nummulites
Lamarck 1801 of the Tethyan Realm based on significant characters
N.S. MATHUR
Wadia Institute of Himalayan Geology, Dehra Dun 248001, India
Abstract: Based on nature of spire in various species of Nummulites
of the Tethyan Realm, three classes have been recognized. The species with
gradually opening spire from centre to outer part fall under Class A, those
with slowly opening/tightly coiled spire under Class B, and those with
loose/rapidly opening spire under Class C. Within these classes, several
subclasses have been distinguished on the basis of a detailed study of
nature of spire. As shape, size and spacing of chambers as well as thickness
of marginal cord are quite consistent features in various species of this
genus, a number of divisions and/or subdivisions have been delineated. These
categories fall under various species groups, subgroups and/or lineages.
Additional significant morphological characters, including shape,
granulations and septal filaments of the test as well as septa and size of
meglosphere (in case of Forms A), have been used for delineating these
ranks.
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