Larger benthic foraminifera during the Eocene within the Tethyan realm played a crucial role in regional biostratigraphy.In the Middle East,particularly in Libya,Tunisia,and Egypt,nummulitids are key constituents of n...Larger benthic foraminifera during the Eocene within the Tethyan realm played a crucial role in regional biostratigraphy.In the Middle East,particularly in Libya,Tunisia,and Egypt,nummulitids are key constituents of nummulitic limestone reservoirs,making the taxonomic identification of this structurally complex group vital for biostratigraphic and petroleum applications.This review focuses on the genus Gaziryina of the nummulitids,clarifying its taxonomic status,biostratigraphic utility,and paleobiogeographic significance using biometric data from published literature.Previously misidentified as Nummulites pulchellus,Gaziryina species have been systematically reassessed based on biometric data from published literature.The findings confirm Gaziryina as a distinct genus comprising two species:Gaziryina basatinensis(late Lutetian-Bartonian,SBZ15-18a) and Gaziryina pulchellus(late Bartonian-Priabonian,SBZ18a/b-20).Morphological characters(test shape,size progression,chamber configuration,protoconch enlargement) and ontogenetic trends(tight to lax) indicate a phylogenetic transition where Gaziryina basatinensis evolved into Gaziryina pulchellus,consistent with Cope's rule.Paleobiogeographic reconstruction indicates a probable origin in the southern NeoTethys,likely the Western Desert of Egypt,with subsequent dispersal across the northern and southeastern Tethys.These findings confirm Gaziryina as a key biostratigraphic marker,necessitating further research on its evolution and biostratigraphic framework.展开更多
The genus Assilina is a taxon within the Nummulitacea that appeared early in the Ypresian(Early Eocene)and continued until the end of the Lutetian(Middle Eocene).Thus,this taxon could be useful for the chronostratigra...The genus Assilina is a taxon within the Nummulitacea that appeared early in the Ypresian(Early Eocene)and continued until the end of the Lutetian(Middle Eocene).Thus,this taxon could be useful for the chronostratigraphy of this time interval.Lower Eocene rocks in southern Galala,Egypt are exposed at Bir Dakhl.This section includes marl sediments with debris flow shallow-marine facies deposits laid down during early Eocene times and includes fossils of large foraminifera:Assilina placentula Deshayes,1838 and Nummulites burdigalensis de la Harpe,1926.These are systematically treated,described and illustrated.Nummulites burdigalensis belongs to the N.burdigalensis group,and Assilina placentula belongs to the group of Assilina exponens.This assumption is based on qualitative morphology and quantitative measurements.Both species,together with Operculina libyca Schwager,1883,enable the assignment of the Bir Dakhl(D5-40 Section)to the Early Eocene,Ypresian(SBZ10 of Serra-Kiel et al.,1998)supporting an earlier opinion that Assilina placentula belongs to that zone in the calibrated larger foraminiferal biostratigraphic zonation.展开更多
文摘Larger benthic foraminifera during the Eocene within the Tethyan realm played a crucial role in regional biostratigraphy.In the Middle East,particularly in Libya,Tunisia,and Egypt,nummulitids are key constituents of nummulitic limestone reservoirs,making the taxonomic identification of this structurally complex group vital for biostratigraphic and petroleum applications.This review focuses on the genus Gaziryina of the nummulitids,clarifying its taxonomic status,biostratigraphic utility,and paleobiogeographic significance using biometric data from published literature.Previously misidentified as Nummulites pulchellus,Gaziryina species have been systematically reassessed based on biometric data from published literature.The findings confirm Gaziryina as a distinct genus comprising two species:Gaziryina basatinensis(late Lutetian-Bartonian,SBZ15-18a) and Gaziryina pulchellus(late Bartonian-Priabonian,SBZ18a/b-20).Morphological characters(test shape,size progression,chamber configuration,protoconch enlargement) and ontogenetic trends(tight to lax) indicate a phylogenetic transition where Gaziryina basatinensis evolved into Gaziryina pulchellus,consistent with Cope's rule.Paleobiogeographic reconstruction indicates a probable origin in the southern NeoTethys,likely the Western Desert of Egypt,with subsequent dispersal across the northern and southeastern Tethys.These findings confirm Gaziryina as a key biostratigraphic marker,necessitating further research on its evolution and biostratigraphic framework.
文摘The genus Assilina is a taxon within the Nummulitacea that appeared early in the Ypresian(Early Eocene)and continued until the end of the Lutetian(Middle Eocene).Thus,this taxon could be useful for the chronostratigraphy of this time interval.Lower Eocene rocks in southern Galala,Egypt are exposed at Bir Dakhl.This section includes marl sediments with debris flow shallow-marine facies deposits laid down during early Eocene times and includes fossils of large foraminifera:Assilina placentula Deshayes,1838 and Nummulites burdigalensis de la Harpe,1926.These are systematically treated,described and illustrated.Nummulites burdigalensis belongs to the N.burdigalensis group,and Assilina placentula belongs to the group of Assilina exponens.This assumption is based on qualitative morphology and quantitative measurements.Both species,together with Operculina libyca Schwager,1883,enable the assignment of the Bir Dakhl(D5-40 Section)to the Early Eocene,Ypresian(SBZ10 of Serra-Kiel et al.,1998)supporting an earlier opinion that Assilina placentula belongs to that zone in the calibrated larger foraminiferal biostratigraphic zonation.
