Globigerinatheka mexicana Cushman 1925 from: Pearson, P.N.Olsson, R.K.Hemleben, C.Huber, B.T.Berggren, W.A. (2006): Atlas of Eocene Planktonic Foraminifera. p. 1-513 . |
Notice: This catalogue page may contain unedited data.
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Species Globigerinatheka mexicana Cushman 1925 |
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Diagnosis / Definition: |
Pearson et al. (2006):
DESCRIPTION.
Type of wall: Spinose, cancellate, densely
porous, pores about 0.04 mm in diameter.
Test morphology: Test very close to spherical,
early chambers arranged in a low trochospire composed
of at least 6 subglobular chambers initially gradually
increasing in size as added, then increasing much more
rapidly; last chamber hemispherical constituting almost half of the entire test totally covering the umbilical side
of the earlier chambers; sutures poorly visible except
between the last two to three chambers where they are
very slightly depressed; three visible apertures at the base
of the last chamber, small to medium-sized arches close
to subcircular, apparently located at the junctions of
previous chambers.
Size: The diameter of the holotype measures 0.30
mm, much smaller than that indicated by Cushman
(1925, diameter 0.40-0.60 mm). |
Discussion / Comments: |
Pearson et al. (2006):
DISTINGUISHING FEATURES.-
Globigerinatheka
mexicana is characterized by its nearly spherical test and
large inflated last chamber that comprises about half of
the entire test. It differs from G. semiinvoluta by its less
embracing last chamber and smaller secondary apertures
that lack a rim, from G. barri by its larger hemispherical
last chamber, less depressed sutures throughout,
spherical outline and less common bullae, and from C.
kugleri by its more spherical test and less distinct sutures.
DISCUSSION.-
As reported by Bolli (1972, p. 129),
Cushman's species mexicana "has been misinterpreted
more than any other of the Globigerinatheka" (see the
synonymy list) owing to the inadequate original
description and illustrations and to the fact that
specimens with different features and of much larger
sizes than the holotype have been identified as mexicana,
including by Cushman himself (1927). Saito (1962), in
emending mexicana, regarded it as being very closely
related to barri, which he interpreted as the bullate form
of the former. Saito's view was followed by Bolli (1972,
p. 129) who, based on Beckmann's observation of the
original types, considered mexicana S. S. and barri as subspecies of Globigerinatheka mexicana. Bolli (1972)
also included in mexicana his species kugleri, again as a
subspecies of it, based on his finding intermediate forms,
a view rejected here (see above). For instance, the
specimen illustrated by Bolli (1972, pl. 2, fig. 5, the spiral
view) as C. mexicana mexicana for its subtriangular
outline is attributable to C. kugleri. Toumarkine (1978)
illustrated as G. mexicana mexicana some specimens
that do not possess the last large enveloping chamber
and have a rather short, not flat initial spire; they may
be closer to G. barri. The specimen attributed by
Samanta (1970, pl. 2, figs. 20-21) to G. barri in our
opinion exhibits a large last chamber that is more
characteristic of G. mexicana. Blow (1979, p. 789)referred Globigerinatheka kutchensis Singh and Tewari,
1967 to G. mexicana mexicana because it possesses
abortive chambers and not true bullae. Blow and Saito
(1968a) regarded mexicana as synonymous with
semiinvoluta, whilst Blow (1979) considered mexicana
as synonymous with tropicalis. We recognise all these
species as separate taxa (also see Bolli, 1972 for
discussion).
PHYOGENETIC RELATIONSHIPS.-
Bolli (1 972, p.
114) stated that mexicana "branched off from G.
subconglobata micra near the base of G. subconglobata
subconglobata Zone (= upper part of Zone E8), while
the subspecies barri and kugleri originated from
mexicana s.s. in subsequent order always within the G.
subconglobata subconglobata Zone". Besides Bolli
(1 972), other authors (i.e., Stainforth and others, 1975;
Blow, 1979; Toumarkine, 1983) all agree that mexicana
appears first, followedq slightly later by barri.
Consequently, G. mexicana probably descended from
the G. subconglobata plexus close to the EWE9 zonal
boundary. Through Zone E1 3, the sutures of G. mexicana
become less pronounced, the final chamber more
spherical and apertures semicircular to circular in outline.
In uppermost Zone E13 and lowermost E14 in the
western North Atlantic (ODP Site 1052), transitional
forms are evident to G. semiinvoluta (Plate 7.8, Fig. 1 l).
GEOGRAPHIC DISTRIBUTION.-
Low to mid latitudes.
STABLE ISOTOPE PALEOBIOL0GY.-
Globigerinatheka
mexicana has oxygen and carbon isotopic
ratios indicative of a mixed layer habitat (Boersma and
others, 1987; Wade, 2004). |
Systematics: |
35 Ordo Foraminiferida
Superfamilia Globigerinaceae
Familia Globigerinidae
Genus Globigerinatheka
Species Globigerinatheka mexicana
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Synonym list: |
Pearson et al. (2006):
1925 Globigerina mexicana Cushman. - Cushman : p.61 pl. 1; fig. 8a-b [upper Eocenc, Tantoyuca Fm., State of Vera Cruz,
Mexico]
non 1953 Globigerinoides mexicana Cushman. - Beckmann : p.395 pl. 25; fig. 15, 16 (= G. euganea), figs. 17-19
(= 0. beckmanni) [middle Eocene, Oceanic Fm.,
Barbados]
non 1957 Porticulasphaera mexicana Cushman. - Bolli et al. : p. 34-35 pl. 6; fig. 8-9b [middle Eocene
Orbulinoides beckmanni Zone, Navet Fm., Trinidad]
non 1957 Porticulasphaera mexicana Cushman. - Bolli : p.165 pl. 37; fig. 1a-b [middle Eocene,
Orbulinoides beckmanni Zone, Navet Fm., Trinidad]; (=
0. beckmanni).
p 1962 Globigerapsis mexicana Cushman. - Saito : p.219 pl. 34; fig. 6a-b (not 7a-c = G. euganea); [Eocene, Hahajima, Hillsborough Island, Japan]
? 1968 Globigerinatheka? sp. . - Samuel & Salaj : pl. 21; fig. 4a, b (cf. Globigerinatheka barri
Brönnimann); [middle Eocene ?Truncorotaloides rohri Zone, central
Carpathians, Slovakia]; [Not Brönnimann, 1952]
1969 Globigerapsis tropicalis Blow & Banner. - Blow : pl. 27; fig. 5-6 [middle Eocene Zone P13, Kilwa area,
Tanzania]; [Not Blow and Banner, 1962]
1970 Globigerinatheka barri Brönnimann. - Samanta : pl. 2; fig. 20, 21 [middle Eocene Orbulinoides beckmanni Zone,
Lakhpat, Cutch, India]
1970 Globigerinoides kugleri Bolli et al.. - Mohan & Soodan : pl. 1; fig. 10a-b [middle
Eocene Globigerinoides kugleri-Globigerina frontosa
Zone, Kutch, India]; [Not Bolli, Loeblich and Tappan,
1957]
non 1970 Globigerapsis mexicana Cushman. - Baumann : pl. 3; fig. 4a-c [middle Eocene Globigerapsis mexicana Zone,
Scalette Section, Umbria, central Italy]; (= G. tropicalis)
1971 Globigerinatheka barri Brönnimann. - Toumarkine : pl. 3; fig. 1-4 [fig. 1, upper Eocene Globigerapsis semiinvoluta
Zone; figs. 2-3, middle Eocene Truncorotaloides rohri Zone, Halimba borehole, Bakony, Hungary]; [Not
Brönnimann, 1952]
non 1971 Globigerapsis mexicana Cushman. - Toumarkine : pl. 3; fig. 8-10 [upper Eocene
Globigerapsis semiinvoluta Zone, Halimba borehole,
Bakony, Hungary]; (= G. barri)
non 1971 Globigerapsis mexicana Cushman. - Raju : pl. 11; fig. 1-6 [upper Eocene, Cauvery basin, India]; (=
G. semiinvoluta)
p 1972 Globigerinatheka mexicana mexicana Cushman. - Bolli : p.129 text-fig. 1-11 (1-2, refigured holotype; 3-6,
holotype redrawn by Blow and Saito, 1968a);
pl. 2 (partim), figs. 1-2,4 (not pl. 2: fig. 3 = G. kugleri); [middle Eocene
0. beckmanni Zone, Navet Fm., Pointe-á-Pierre,
Trinidad]
1975 Globigerinatheka mexicana mexicana Cushman. - Toumarkine : pl. 4; fig. 3, 4 [middle Eocene
Globorotalia lehneri to Truncorotaloides rohri Zone,
DSDP Site 305, Shatsky Rise, north-west Pacific
Ocean]
p 1975 Globigerinatheka mexicana Cushman. - Stainforth et al. : fig. 67.1-3,5 (from Bolli, 1972);
figs. 4a-d (refigured holotype hom Blow and Saito, 1968a) (not
fig. 67.6, from Bolli, 1972 = G. kugleri)
non 1978 Globigerinatheka mexicana mexicana Cushman. - Toumarkine : pl. 4; fig. 5 (= G. subconglobata), 6
and 7 (= G. barri) [middle Eocene Hantkenina aragonensis
to Globorotalia lehneri Zone, DSDP Site 363, South
Atlantic Ocean]
p 1979 Porticulasphaera mexicana mexicana Cushman. - Blow : pl. 27; fig. 5-6 (new name for G. tropicalis of Blow, 1969);
pl. 198 (partim), figs. 1, 3 (not figs. 2, 4-5 = G. kugleri) [middle Eocene Zone P1 3, Kilwa area, Tanzania]
non 1979 Globigerapsis mexicana Cushman. - Blow : p.330 pl. 27; fig. 3-4 [upper Eocene Zone P15, Lindi area,
Tanzania]; (= G. semiinvoluta)
p 1983 Globigerinatheka mexicana mexicana Cushman. - Toumarkine : pl. 20 (partim), fig. 34 (from Bolli, 1972);
pl. 20, fig. 39 (from Toumarkine, 1975) (not fig.
33 = G. kugleri; not figs. 35-38 = G. subconglobata)
? 1983 Globigerinatheka mexicana Cushman. - Pujol : pl. 7; fig. 1 [middle Eoccne Zone P1 1-13, DSDP Site 516,
Rio Grande Rise, South Atlantic Ocean]
? 1992 Globigerinatheka index Finlay. - Berggren : pl. 3; fig. 7 [middle Eocene, ODP Hole 748B, Kerguelen
Plateau, Indian Ocean]; [Not Finlay, 1939]
non 1994 Globigerinatheka mexicana mexicana Cushman. - Nishi & Chaproniere : pl. 2; fig. 14-15, ?13 [upper Eocene Zones P15-16, DSDP Hole
841B, south-west Pacific Ocean]; (= G. index)
2006 Globigerinatheka mexicana Cushman. - Pearson et al. : p.194 pl. 7.8; fig. 1-16 (Pl. 7.8, Figs. l, 2: new SEMs of holotype of
Globigerina mexicana Cushman)
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Was used in synonym list of: |
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Specimen: |
Smithsonian Museum of Natural History, Washington, D.C., Inventory number: USNM 4334
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References: |
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