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Foresi et al 2002 pl1 f01a-c.JPG
Foresi et al 2002 pl1 f02-3.JPG
Foresi et al 2002 pl1 f04-5.JPG
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Foresi et al 2002 pl1 f10-11.JPG
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Foresi et al 2002 pl2 f01-2.JPG
Foresi et al 2002 pl2 f05-6.JPG
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Foresi et al 2002 pl2 f13a-b.JPG
Foresi et al 2002 pl2 f14.JPGCurrent identification:
Original Description
Size:
Extra details from original publication
Remarks: The variability of the subspecies has been described in detail previously by Tjalsma (1971), Zachariasse (1975), and in the foreword of this paper. Ve report here the most variable features: the equatorial profile may be more or less elongated (Pl. 1, fig. a-5 and 9, 13); the aperture is sometimes limited to the umbilical area (Pl. 2, fig. 6, 12) and may vary in size; the chambers of the last whorl are rarely 4 and half and 5 only when the last chamber is abortive and smaller than the previous one (Pl. 2, fig. 11). The anterior compression of the last chamber and the high of the apertural arch become less appreciable in the upper part of its range.
N. atlantica praeatlantica differs from N. atlantica atlantica (Pl. 3, figs. 1-8) for the considerably smaller size (compare Pl. 3 with Pls. 1,2), less number of chambers in the last whorl (generally 4 rather than 5), commonly umbilical-extraumbilical aperture (and not generally umbilical), with a thick rim or lip (commonly absent in "atlantica"), cancellate wall texture without secondary encrustations.
N. acostaensis (Blow) (P1. 4, figs. 1-8) differs for a less inflated test, the generally 4 and half -5 chambers in the last whorl, the more circular equatorial profile, the last chamber smaller than the previous one, and the aperture a low slit with well developed lip. Neogloboquadrina 4-chambered type, distinguished by Hilgen et al. (2000) in the neogloboquadrinid assemblages from Miocene succession of Monte Gibliscemi is considered by the authors a variant of N. acostaensis (p1.2, figs. 8-9).
N. atlantica preatlantica is also related to Catapsydrax parvulus Bolli, Loeblich & Tappan (Pl. 4, figs. 9-19) which differs for its smaller size, more compressed chambers and test, smaller and lower aperture umbilical, the presence of a little bulla or an abortive last chamber covering the umbilicus. The relationship is based on the occurrence in the basal part of the neogloboquadrinid range of C parvulus morphotypes grading into N. atlantica praeatlentica.
Stratigraphy distribution (Fig. 1): in the Mediterranean N. atlantica praeatlantica first occurs at the astronomical age of 11.78 Ma (Hilgen et al. 2000, Foresi et al. 2002) and vanishes within the Globigerinoides extremus Zone of Foresi et al. (1998). The FO of the subspecies marks the MMi7/MMi8 zonal boundary of Sprovieri et al. (2002) and the N. continuosa/P siakensis zonal boundary of Foresi et al. (1998). However in the upper part of its range it becomes very rare. According to Hilgen et al. (2000) its LRO occurs around 10.48 Ma. In Site 982 located at 57°N in the Atlantic Ocean, N. atlantica praeatlantica occurs (Lirer, unpublished data) within the B. badenensis Zone (Spiegler 1999) between 11.9 and 12.6Ma. At low latitude (Ceara Rise, 3°N) N. atlantica praeatlantica is absent, and the FO of neogloboquadrinids is characterized by sinistral forms of N. acostaensis which first occurs at 9.89 Ma (Turco et al. in press). At Site 397 (Cap Bojador, 26'N) (Foresi et al. 1998) N. a. praeatlantica first occurs in levels postdating the LCO of G. subquadratus (synchronous event between Mediterranean and low latitude; Foresi et al. 2002, Turco et al. in press) at 11.54 Ma. It follows that the N. atlantica praeatlantica migrated from higher to lower latitude through time. This strengthens the hypothesis ol Zachariasse, (1992), Zachariasse & Aubry (1994), Hilgen et al. (2000), and Turco et al. (2001) that the areal distribution of N. atlantica (sensu lato) is primarily controlled bv cold surface water.
Origin of N. atlantica praeatlantica
All the authors agree that the entry of the neogloboquadrinids in the biological record is a Middle Miocene event, but the origin and phylogeny of the genus Neogloboquadrina is still an open problem. As previously stated the neogloboquadrinids firstly entered into the Mediterranean sedimentary record in the late Middle Miocene (Serravallian) at the astronomical age of 11.78-11.8 Ma (Hilgen et al. 2000; Di Stefano et al. 2002; Foresi et al. 2002). According to several authors (Zachariasse 1992; Zachariasse & Aubry 1994; Hilgen et al. 2000), this invasion is connected with a climatic cooling and more precisely (Turco et al. 2001) is related to Mi 5 event of Miller et a|. (1991). This entry represents an excellent and synchronous event easily recognizable in the Mediterranean successions (Foresi et al. 1998, 2002,in press; Hilgen et al. 2000) and virtually coincides with last occurrence (LO) of Paragloborotalia partimlabiata (Ruggieri & Sprovieri) (sensu Foresi et al.20A2, not sensu Hilgen et al. 2000). On the contrary this event is strongly diachronous (almost about 2 my) with the low latitude FO as evidenced by Hilgen et al. (2000) and Turco et al. (in press), that renders the correlation with the low latitude zonal scheme of Blow (1969) no more possible.
Foresi et al. (1998) suggested its evolution from Globorotaloides falconarae. This hypothesis was in agreement with that suggested by Zachariasse & Aubry (1994) who derived N. atlantica from C. parvulus of which G. falconarae was considered a junior synonym (Zachariasse 1992). This synonymy was rejected by Hilgen et al. (2000) who regarded G. falconarae as evolved from Globoquadrina sp.1 whiie C. parvulus was considered a low latitude homeomorphic species. The resemblance of N. atlantica with some morphotype of Globoquadrina sp.1, induced the authors to suggest that N. atlantica might be originated from Globoquadrina sp.1.
We agree withZachariasse's (1992) opinion about the synonymy between C. parvulus and "G. falconarae" and we think that "Globoquadrina sp.1." represents large sized specimens of "G. falconarae" (Pl. 4, figs. 17, 18).
In the present intepretation N. atlantica praeatlantica is suggested to be evolved from Catapsydrax parvulus (Pl. 5, figs. 1-10) through the gradational morphotypes (described in the remarks) occurring at the beginning of the neogloboquadrinid distribution in the Mediterranean and Globoquadrina sp. 1, could be one of these morphotypes.
Samples from Leg 162, Site 982 located at 58° N in the North Atlantic, (Lirer, unpublished data) contain "Globoquadrina sp.I" morphotypes together with the first Neogloboquadrina atlantica praeatlantica. Therefore, the origin and philogeny of N. atlantica praeatlantica still remains poorly understood and documented. The previously inferred hypothesis about the origin of N. atlantica praeatlantica at present cannot be proved. However, according to the writers its migration into the Mediterranean should closely postdate its evolutionary appearance because its morphology is very similar to that of the suggested ancestor.
The occurrence of transitional forms between praeatlantica and acostaensls in the earliest levels of the neogloquadrinid distribution of the Mediteranean (Foresi et al. 1998, pl. 2, fig. 7 and Hilgen et al. 2000, pl. 3, figs. 1-16 and 22-27) suggests that N. acostaensis could be evolved from N. atlantica praeatlantica. In fact, rare morphotypes referable to N. acostaensis are already present in the earliest neogloboquadrinid assemblages entering the Mediterranean in Zone N.14. If it is not biologically certain that these very rare forms are N. acostaensis, it is certain that the evolutionary appearance of this taxon (which reaches the tropical regions later; Zachariasse 1992, Hrlgen et al. 2000, Turco et al. 2001 and in press) predates that established by Blow (1969)
Foresi, L. M. et al. (2002a). High resolution calcareous plankton biostratisraphy of the Serravallian succession of the Tremiti Islands (Adriatic Sea, Italy). In, S. M. , I. (ed.) Integrated Stratigraphy and Paleoceanography of the Mediterranean Middle Miocene. Rivista Italiana di Paleontologia e Stratigrafia . 108: 257-273. gs Foresi, L. M., Iaccarino, S. & Salvatorini, G. (2002b). Neogloboquadrina atlantica praeatlantica, new subspecies from Late Middle Miocene. In, S. M. , I. (ed.) Integrated Stratigraphy and Paleoceanography of the Mediterranean Middle Miocene. Rivista Italiana di Paleontologia e Stratigrafia . 108: 325-336. gs Hilgen, F. J., Krijgsman, W., Raffi, I., Turco, E. & Zachariasse, W. J. (2000). Integrated stratigraphy and astronomical calibration of the Serravallian/Tortonian boundary section at Monte Gibliscemi (Sicily, Italy). Marine Micropaleontology. 38: 181-211. gs Sprovieri, R. et al. (2002). An integrated calcareous plankton biostratigraphic scheme and biochronology for the Mediterranean Middle Miocene. In, S. M. , I. (ed.) Integrated Stratigraphy and Paleoceanography of the Mediterranean Middle Miocene. Rivista Italiana di Paleontologia e Stratigrafia . 108: 337-353. gs Tjalsma, R. C. (1971). Stratigraphy and foraminifera of the Neogene of the Eastern Guadalquivir Basin (southern Spain). Utrecht Micropaleontological Bulletin. 4: 1-161. gs Zachariasse, W. J. & Aubry, M. P. (1994). Origin and early dispersal of Neogloboquadrina. Paleobios. 16(2): 68-. gs Zachariasse, W. J. (1975). Planktonic foraminiferal biostratigraphy of the Late Neogene of Crete (Greece). Utrecht Micropaleontological Bulletin. 11: 1-171. gsReferences:
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Neogloboquadrina atlantica praeatlantica compiled by the pforams@mikrotax project team viewed: 12-10-2024
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