DOI: 10.5176/2251-3353_GEOS13.45
Authors: Imad Mahmood Ghafor
Abstract: Biometric investigation of the megalospheric individuals of Nephrolepidina assemblages from Bai-Hassan well-25 section in Kirkuk area, Iraq led to recognize three morphometrically defined species( Lipidocyclina praemarginata, L.ex.interc. praemarginata-morgani and L morgani ) by the combination of two parameters, the degree of embracement of the protoconch by the deuteroconch, (Factor A) and number of accessory auxiliary chambers on the deuteroconch. (factor B) On the basis of generally accepted theory which is called embryonic and nepionic acceleration The succession of these three species corresponds to the phylogenitic lineage in the European –Mediterranean area which started at some level in the middle part of the Oligocene and continued upward into the Early Miocene. The slow numerical progress in this lineage and especially the double morphometric definition of the species limits have led to the recognition of a wide array of morphologically intermediate assemblages.
Keywords: Late Oligocene, Kirkuk area, Northeast Iraq, Bai-Hassan Well- 25, Evolutionary aspects
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