The Oligocene nannolith Sphenolithus evolutionary lineage: morphometrical insights from the palaeo-equatorial Pacific Ocean
2010 (English)In: Journal of Micropalaeontology, ISSN 0262-821X, no 29, 17-35 p.Article in journal (Refereed) Published
Changes in morphology within the biostratigraphically important Oligocene nannofossil lineage, Sphenolithus predistentus-distentus-ciperoensis, were investigated in carbonate sediments from the paleo-equatorial Pacific Ocean Site 1218 in order to determine the nature of this evolutionary lineage. Using differences in their morphology and stratigraphic ranges, the aim of this study was to determine whether this set of sphenolith species represents an anagenetic evolutionary lineage or a set of discrete species with overlapping geological ranges. 1000 specimens were analysed morphometrically and the basal ratio (the ratio between the proximal cycle height and basal width), was identified as a key parameter for study of this lineage. We conclude that S. distentus and S. predistentus are intergradational species forming an anagenetic lineage but that S. ciperoensis is a discrete species which evolved relatively abruptly in the Late Oligocene.
Place, publisher, year, edition, pages
2010. no 29, 17-35 p.
Oligocene, Sphenolithus predistentus, S. distentus, S. ciperoensis, evolutionary lineage, morphometry, ODP Leg 199 Site 1218, Pacific Ocean
Research subject Geology
IdentifiersURN: urn:nbn:se:su:diva-27597DOI: 10.1144/jm.29.1.17ISI: 000279030100003OAI: oai:DiVA.org:su-27597DiVA: diva2:216399