Globorotalia hirsuta d'Orbigny 1839 from: Bolli, H.M.Saunders, J.B. (1985): Oligocene to Holocene low latitude planktic foraminifers. In: Plankton Stratigraphy Eds: Bolli, H.M.Saunders, J.B. p. 155-262 | . |
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Species Globorotalia hirsuta d'Orbigny 1839 |
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| Discussion / Comments: |
Bolli & Saunders (1985):
The species which may be mistaken most easily for the Early Pliocene G. margaritae is G. hirsuta, known from the Pleistocene and Recent. The lost original type figured by d'Orbigny measured only about, 1/3 mm. It is unfortunate that Blow (1969) selected a neotype with three chambers more, measuring 0.59 mm or about double the original type. G. margaritae and G. hirsuta possess morphological similarities, but an evolutionary connection cannot be recognized on present evidence. The reasons for this are pointed out above where it is shown that Blow's G. praehirsuta is in fact a G. margaritae, with a range no higher than Early Pliocene and therefore cannot serve as an intermediate between G. margaritae and G. hirsuta in the Middle and Late Pliocene. A characteristic difference between G. hirsuta and G. margaritae lies in the presence of a more convex umbilical surface in hirsuta, resulting in a deeper umbilical pit. In addition, chambers in G. hirsuta are more loosely coiled and are finely spinose as the name implies. The equatorial periphery in G. hirsuta is more lobate than in G. margaritae, except for the last chamber or two in highly evolved forms of the latter: the peripheral keel is less pronounced in G. hirsuta. G. hirsuta is a temperate form, originally described by d'Orbigny from near the Canary Islands. In its typical development it is largely absent in tropical subtropical areas. G. margaritae on the other hand is much more cosmopolitan, known to occur in the Early Pliocene of both tropical and temperate regions. The geographic concurrence of the two morphologically somewhat similar species in, for example, the Mediterranean area is the reason why in some publications Gmargaritae has been erroneously identified as G. hirsuta. |
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Bolli & Saunders (1985):
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| Stratigraphy - absolute ages: |
FAD: 0.45 ± 0 [Ma], Berggren et al. (1995)
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| References: |
d'Orbigny,A.D. (1839):
Foraminifères.
In: Histoire Physique, Politique et Naturelle de l'ile de Cuba2 (atlas vol 8 pls 1-12) Eds: de la Sagra, R. p. 1-224
Blow,W.H. (1969):
Late middle Eocene to Recent planktonic foraminiferal biostratigraphy.
In: Proceedings of the First International Conference on Planktonic Microfossils, Geneva 1967 Vol. 1 Eds: Bronnimann, P.Renz, H.H. p. 199-422
Bolli,H.M. and Saunders,J.B. (1985):
Oligocene to Holocene low latitude planktic foraminifers.
In: Plankton Stratigraphy Eds: Bolli, H.M.Saunders, J.B. p. 155-262
Berggren,W.A.; Hilgen,F.J.; Langereis,C.G.; Kent,D.V.; Obradovich,J.D.; Raffi,I.; Raymo,M.E. and Shackleton,N.J. (1995):
Late Neogene chronology: New perspectives in high-resolution stratigraphy . Geological Society of America Bulletin Vol. 107(11)
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