Matskási István (szerk.): A Magyar Természettudományi Múzeum évkönyve 79. (Budapest 1987)

Kecskeméti, T.: Contributions to the phylogenetic connections of Nummulites species

N. dudarensis fit very well in that part of the lineage which predates the Late Lutetian stage of the morphogenetic evolution of N. variolarius. By Late Lutetian time, N. variolarius had got taxonomically stabilized to some extent and it had become more uniform. Once it had passed the Middle/Upper Eocene boundary, it became again more plastic giving rise to the source species of a relatively rich and heterogeneous Upper Eocene Nummulites fauna. After differentiation, a rapid simplification in its ontogeny is observable which led — still in the initial period of the Upper Eocene — to its extinction. As early as Late Lutetian time, N. variolarius saw the separation of N. incrassatus which persisted throughout the Late Eocene and even in a considerable part of the Oligocène. This latter was that which gave rise, at the Eocene/Oligocene boundary, to N. vascus, form that lived only during the Oligocène. The virtual differentiation of N. variolarius began, however, as late as the outset of Late Eocene time. By and large simultaneously with this development, the following collateral lines departed from the stock: N. rectus, a convex form and N. prestwichiatws and N. bouillei, forms having flat shells. The character they have in common is represented by the operculinoid chambers. N. rectus and N. prestwichianus got extinct at the end of Late Eocene time, but N. bouillei persisted in the initial interval of the Oligocène as well. The present writer's morphogenetic studies suggest that the role N. variolarius played in its lineage was assumed — at a much lower level though — somewhere around the middle of Late Eocene time by N. paravariolarius*

. Its existence spanned the upper interval of the Late Oligocène only. Deviating in habit and structure from the foregoing, N. chavannesi got separated also at the beginning of Late Eocene time, its presence being observable throughout a good deal of the Late Eocene. The form that sprang off from it around the middle of Late Eocene time was N. budensis which, after passing the Eocene/Oligocene boundary, became one of the last species that constituted the sparse Oligocène Nummulites fauna. A form linked with the globulus—variolarius line that issued from the stock stratigraphically deeper was N. rozlozsniki. ROZLOZSNIK reported from the Dorog Basin a taxon akin to N. globulus (N. globulus rasse dorogensis n. r.; ROZLOZSNIK 1929, p. 102, Taf. Ill, Fig. 32, 36). As obvious from the description, the taxon is tied, as far as its major characters are concerned, to N. globulus, but some characters suggest a kinship to N. variolarius as well. Later on, MÉHES promoted this taxon, under the name N. rozlozsniki, to the rank of a species (MÉHES 1961). The enclosing rock, the Operculum claymarl, had been regarded as Ypresian. At its stratigraphie revision (SZŐTS 1967), however, it turned out to be Lutetian in age. This assignation did not concern the relation of N. rozlozsniki and N. globulus, the only change it had brought about was the assignation of N. rozlozsniki to the Lutetian, i. e. its getting farther away from N. globulus. The time of differentiation is a question still to be answered. It is very likely, however, that it falls in the major Early Lutetian speciation interval. In some features, N. rozlozsniki is akin to N. subplanulatus as well, but these characters are already very "faint". The conclusion that may be drawn from this circumstance is that the separation of the two taxa could take place at an early date, presumably at the time of disintegration of the variolarius and striatus lineages. In spite of the wide geographic range of N. rotularius, this species is a poorly known one, its genetic connections being unclear. There are points of controversy even as far as its descent from the ancestral form is concerned. SCHAUB places it on a line of parallel development issuing synchronously with N. solitarius, assigning it to the burdigalensis

—perforatus group. The form in which he represents it in his phylogenetic scheme is such as N. rotularius, after * and not "praevariolarius" as in Table on p. 63.