Briguglio, A.

Eder, W.

Hohenegger, J.

Torres, A. I.

English

Torres A. I.

Eder W.

Hohenegger J.

Briguglio A.

Archivio istituzionale della ricerca - Università di Genova

Geophysical Research AbstractsVol. 19, EGU2017-12654, 2017EGU General Assembly 2017© Author(s) 2017. CC Attribution 3.0 License.Morphometric analysis of Eocene nummulitids in Western and CentralCuba - inferences on taxonomy, biostratigaphy and evolutionary trendsAna Ives Torres-Silva (1), Wolfgang Eder (1), Johann Hohenegger (1), and Antonino Briguglio (2)(1) University of Vienna, Earth Sciences, Palaeontology, Vienna, Austria (ana_ivist@hotmail.com), (2) Universiti BruneiDarussalam, Department of Petroleum Geoscience, Jalan Tungku Link, Gadong BE1410, Brunei DurassalamNone other larger benthic foraminifera (LBF) group in the Caribbean realm has led to such diverse opinionsand controversy about their classification than the nummulitids. Unlike the Tethys species, where delimitationand details of evolutionary changes within species are well known, intraspecific evolution in the Caribbeanremains understudied and generic nomenclature has not reached consensus yet. Morphometric studies appear tobe the most appropriate methods in solving this unsatisfactory taxonomical situation. For every proposed species,morphological variations correlating with paleoecological factors and precise stratigraphic occurrence and rangehas to be studied in detail. Thus, the morphology in equatorial sections of nummulitids without chamber partitionswas quantified at seven localities from Western and Central Cuba and interpreted by eleven growth-independentand/or growth-invariant characters and attributes. 102 isolated megalospheric individuals originating from Cubanlocalities, spanning the time interval from lower Middle Eocene to lower Oligocene, were classified by nonmetricmultidimensional scaling and cluster analysis. Thirteen Caribbean specimens, which are considered as typematerial, were included. Two clearly differentiated morphogroups could be differentiated according to clusterand ordination analysis into the genera Nummulites and Palaeonummulites. Main differences in morphologicalcharacters between the morphogroups were confirmed by discriminant analysis. Nummulites differs from Palaeon-ummulites in a weak increase of the marginal radius and weak backbend angles. All specimens of Nummulitess.stricto from different localities were regarded as Nummulites striatoreticulatus. Based on discriminant analysis,N. striatoreticulatus specimens with similar depositional environments, but of different stratigraphic occurrence,are strongly separated. The older forms have a smaller backbend angle, perimeter ratio and proloculus nominaldiameter, thus documenting stratigraphic and evolutionary trends. The species Nummulites striatoreticulatus inthe Cuban sections ranges from lower middle Eocene to lower Priabonian.Within the Palaeonummulites group, the exceptional range of morphological variation tends to obscure the factthat there are several well-defined morphological species. Based on discriminant analysis the species P. willcoxi,P. trinitatensis, P. floridensis, P. ocalanus and P. soldadensis were classified ranging from tightly coiled individualsthat are very similar to Nummulites to loosely coiled moprhotypes. Major separators between the species arethe marginal radius, proloculus nominal diameter, spiral chamber height increase and the length of the firstchamber. Stratigraphic trends within species were not clearly detectable, but paleogeographic differences and themorphological overlap between morphogroups in certain species are obvious. Paleonummulites species have longstratigraphic ranges from late Middle Eocene to probably lower Oligocene.

Morphometric analysis of Eocene nummulitids in Western and Central Cuba - inferences on taxonomy, biostratigaphy and evolutionary trends

https://iris.unige.it/bitstream/11567/921412/2/EGU2017-12654%281%29.pdf

Morphometric analysis of Eocene nummulitids in Western and Central Cuba - inferences on taxonomy, biostratigaphy and evolutionary trends

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Archivio istituzionale della ricerca - Università di Genova