Population dynamics of Ordovician conodonts (Oepikodus evae, O. intermedius, and O. intermedius robustus) in the San Juan Formation, Argentine Precordillera

G. M. DELLA COSTA; G. L. ALBANESI

Montpellier

Congreso; II Joint Congress on Evolutionary Biology; 2018

The margins of the distributional space of species could be related to anomalous or unfavorableenvironmental characteristics for the development of species. The present study addresses the analysisof the population dynamics of the conodont fauna from the Peña Sombría section of the Lower-MiddleOrdovician, in northern Argentine Precordillera, over two local populations of conodont species(Oepikodus evae and Oepikodus intermedius robustus), with coeval habitats in deep-waterenvironments, where the presence of K-bentonites act as environmental control for the development,growth and expansion of their distributional range. The population dynamics of both species arecompared with the dynamics of a local population of Oepikodus intermedius inhabiting shallowermarine environments in the Niquivil section of the central Precordillera, where the bathimetric conditionsare not favorable for the distribution of the previously mentioned taxa. The morphometric parametersanalyzed for the Pa and Pb elements of the oral apparatuses are the lengths of the anterior, lateral andposterior processes, the height of the cusp, the number of denticles of the processes, the angle betweenthe cusp and the oral margin of the M elements, and the absolute frequency of individuals of the threespecies. An increase in the number of denticles is very