Demarcation problem in fusuline classifi cation: A case for Verella/Eofusulina discrimination
Department of Earth System Science, Fukuoka University, Fukuoka 814-0180, Japan.
Departamento de Geología, Universidad de Oviedo, c/ Jesús Arias de Velasco, s/n, 33005 Oviedo, Spain. email@example.com
Departamento de Geología, Universidad de Oviedo, c/ Jesús Arias de Velasco, s/n, 33005 Oviedo, Spain. firstname.lastname@example.org
The eofusulinin genera Verella and Eofusulina formed an important lineage among fusulines to define the Bashkirian/ Moscovian transitional interval in the Pennsylvanian (Upper Carboniferous) subsystem. We studied morphologies of Verella transiens, a highly evolved form in the genus, and the first Eofusulina species from the Los Tornos section in the Cantabrian Zone of northern Spain, to understand the discriminating diagnosis of these two genera. We conclude that Eofusulina is distinguishable from Verella in having stronger septal fluting, lesser development of secondary deposits, generally larger proloculus, absence of early tightly coiled volutions, and with some lesser extent slightly larger diameter of shell and absence of polar torsion. No single morphological character provides a reliable criterion to distinguish the two genera, but rather only a combination of all these morphological criteria enables reliable generic discrimination. In order to better understand the morphology, we emphasise the usefulness of non-oriented specimens in this study. They have potential to show some morphological features that are sometimes not easy to perceive based only on well-oriented axial and sagittal sections. In regional biostratigraphic aspects, we propose a minor modification on the FAD of Eofusulina in the Los Tornos section, and lower it about 5 m stratigraphically. We also perform a comprehensive taxonomic review of Verella and Eofusulina. Two replacement names, Verella zhenanensis and V. ivanovae, are proposed for Pseudowedekindellina fusiformis Sun and V. fusiformis Ivanova, which are subjective and objective junior synonyms of V. fusiformis Bensh, respectively. Moreover, we deem V. varsanofievae as a correct original spelling of the type species of Verella, in accordance with the International Code of Zoological Nomenclature.
Key words: Carboniferous, Pennsylvanian, fusuline morphology, thin section, taxonomy.
How to cite: Ueno, K. & Villa, E. 2018. Demarcation problem in fusuline classification: A case for Verella/Eofusulina discrimination. Spanish Journal of Palaeontology, 33 (1), 215-230.
Received 04 December 2017, Accepted 05 March 2018, Published 30 June 2018