Eight populations of microspheric and megalospheric individuals belonging to the species Nummulites ptukhiani (uppermost middle Eocene) and N. fabianii (upper Eocene) from northern Italy, Spain and Romania are described and discriminated biometrically. This distinction permits recognition of the middle/upper Eocene boundary in shallow carbonate platform facies, The name N. ptukhiani as used here applies only to the western European ancestors of N. fabianii, with N. ptukhiani from Armenia being a separate species. In the megalospheric generation, test size, ornamentation, and external form show no direct correlation with geologic age and may have been paleoenvironmentally controlled. On the contrary, the examined B forms of N. ptukhiani are substantially smaller and more inflated than the N, fabianii B forms, Moreover, the ornamentation pattern of N. ptukhiani B (reticulated, granulated) is easily distinguishable from that of N. fabianii B (sinuous to meandering reticulate, non-granulated). For the megalospheric individuals, internal features seem more independent of the paleoenvironment, but they may also have been environmentally controlled in some cases. Four parameters are used to distinguish the A forms: protoconch height, shape of the embryonic apparatus, mean chamber length, and coiling curves. None of these internal features has been found useful to distinguish between the B forms of the two species. Only the total number of whorls is different (two to seven more whorls in N. fabianii B than in N. ptukhiani B). The overall similarities between the two species and the gradual transition of the measured features confirm they are successive chronospecies that can, however, be separated by conventional limits, useful for biostratigraphy of the middle/upper Eocene carbonates of the Tethys.
|Data di pubblicazione:||1998|
|Titolo:||Biometric analyses of Nummulites "ptukhiani" Z.D. Kacharava, 1969 and Nummulites fabianii (Prever in Fabiani, 1905)|
|Autore/i:||Papazzoni, Cesare Andrea|
|Codice identificativo ISI:||WOS:000075177500002|
|Codice identificativo Scopus:||2-s2.0-0032222224|
|Citazione:||Biometric analyses of Nummulites "ptukhiani" Z.D. Kacharava, 1969 and Nummulites fabianii (Prever in Fabiani, 1905) / Papazzoni, Cesare Andrea. - In: JOURNAL OF FORAMINIFERAL RESEARCH. - ISSN 0096-1191. - STAMPA. - 28 (3)(1998), pp. 161-176.|
|Tipologia||Articolo su rivista|
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