THE ORIGINAL PUBLISHED DESCRIPTION OF AN EMBRYONIC APPARATUS FROM THE ORBITOLINIDAE (FORAMINIFERA) (LOWER CRETACEOUS OF BORNEO) WITH A BRIEF COMMENTARY ON THE AGE OF ORBITOLINID OCCURRENCES IN BORNEO

Abstract

The family Orbitolinidae originates with Martin (1890), who described the external and internal test features of orbitolinids from what can now understood to be the Lower Cretaceous of western Borneo. Overlooked in subsequent literature, this description includes the illustration of a transverse section passing through a megalospheric embryo of a specimen assigned to Orbitolina concava Lamarck and regarded as being Cenomanian in age. However, the illustration, description, and dimensions refer this specimen to Palorbitolina lenticularis (Blumenbach, 1805) comprising a relatively large, subdivided chamber (= periembryonic chambers) surrounding a large ‘Centralkammer’. It is worth mentioning that the original illustration by Blumenbach (1805) from the Lower Cretaceous of south-eastern France as Madreporites lenticularis did not show this taxonomically important feature in the modern classification of the Orbitolinidae and with special respect to the subfamily Orbitolininae. The re-interpretation of Martin’s illustrations and a literature review challenge Cenomanian ages ascribed to orbitolinid occurrences in Borneo.