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Malvinia escutiana
Malvinia escutiana Houben et al., 2011, p.177, 179, pl.1, figs.1–12, pl.2, figs.1–6; text-fig.3.
Holotype: Houben et al., 2011, pl.1, figs.1–3.
Age: early Oligocene.
Original description (Houben et al., 2011):
Species: Malvinia escutiana sp. nov. Forma T: Goodman and Ford, plate 6, figs. 14–16.
Holotype: Sample 511–03R 01W 72–73 cm, slide #1 , England Finder (EF) reference: R30-4. Plate I, 1–3. Dimension: 41–45 μm.
Paratype: Sample 511–03R 03W 75–76 cm, slide #2 , EF reference: L25. Plate I, 4–5. Dimension: 42–44 μm.
Stratum typicum: DSDP Leg 71, Site 511, Lithological Unit 2, Subunit 2a.
Derivation of name: Named in recognition of the scientific achievements of Dr. Carlota Escutia, marine geologist and geophysicist of the University of Granada (Spain), expert of the geology of the Antarctic margin.
Diagnosis: Proximate cyst of intermediate size with spherical outline, lacking horns or protrusions. The cyst wall is relatively thin, rugulate and appears to be composed of a single layer; an endo- and periphragm are not distinguishable. Tabulation is protoperidinioid (pr, 4 , 3a, 7 , 1t, 3c, 5″′, 2″″), indicated by low parasutural ridges. The archeopyle is theropylic between the intercalary and apical series. Typically, the dorsal-apical region displaced, generally in the direction of the empty cyst. Specimens are therefore exclusively found folded and distorted.
Dimensions: Average diameter around 45 μm (n= 16, Holotype: 45– 50 μm).
Description: Peridinioid spherical cysts of intermediate size, lacking horns or protrusions. The outer wall surface of the cyst is rugulate, and exhibits faint parasutural ridges. These are difficult to discern under typical LM-magnification (Plate I) but reflect a protoperidinioid tabulation (pr, 4 , 3a, 7 , t, 3c, 5″′, 2″″) under SEM magnification (Plate II). A small, preapical plate (pr) is clearly distinguishable on SEM images (Plate II, 1 and 3) but is not discernable on LM specimens. Plate 1 is characteristically symmetric, as is typical in peridinioid dinoflagellates. The sulcal area (Plate II, 2) consists of one anterior plate (as), a right (rs) and a left (ls) sulcal plate and a posterior (ps) plate. The cingulum is divided on the ventral face with a small sulcal–cingular transitional plate (t). The plates 1c and 3c extend only along the ventral face and the cingulum on the dorsal face consists of a single wide plate (2c) (Plate II, 2), this is characteristic for the Protoperidiniaceae family. The archeopyle is often difficult to discern as result of folding and is theropylic. Parasutural splits occur along the anterior margins of the anterior intercalary plates (1a, 2a and 3a), which remain attached to the cyst (Plate I, 1, 2, 5, 7 and 11). Such splits also occur along the parasutures between the anterior intercalary plates 1a with 2a and 2a with 3aand between apical series (1a with 2 3 , 2a with 3 and 3a with 3 and 4 ). This generally leads to the folding of plate 2a and 3 (Plate II, 1) and displacement of the apical area (Plate I, 1–2; Plate II, 3).
Stratigraphic distribution: At Site 511, the lowest occurrence of Malvinia escutiana is in Sample Core 12R, Section 02 W, 115–117 cm. This level corresponds to an ~1.5 increase in foraminiferal δ18O (Houben et al., submitted for publication; see also Liu et al., 2009), interpreted to represent the Oi-1 isotope shift in the earliest Oligocene (see, e.g., Coxall and Pearson, 2007). This isotopic shift is dated as 33.7 Ma following the timescale ofGradstein et al. (2004). At Site 511 M. escutiana initially occurs sporadically up to Core 6R to occur consistently above it and even becoming quite abundant (~20% relative abundance) in Core 4R and 3R (~32 Ma). The range top of M. escutiana is at least younger than 31.5 Ma at DSDP Site 511 (Fig. 2; Houben et al., submitted for publication).
Geographic distribution: Malvinia escutiana has exclusively been recorded in the Southern Ocean, that is from DSDP Sites 511 and 513 (Goodman and Ford, 1983, Falkland Plateau) and from ODP Sites 693 and 696 (Mohr, 1990, Weddell Sea, early Oligocene). It has also been recorded from ODP Site 739 (P.K. Bijl, 2010 pers. obs., Prydz Bay).
Holotype: Houben et al., 2011, pl.1, figs.1–3.
Age: early Oligocene.
Original description (Houben et al., 2011):
Species: Malvinia escutiana sp. nov. Forma T: Goodman and Ford, plate 6, figs. 14–16.
Holotype: Sample 511–03R 01W 72–73 cm, slide #1 , England Finder (EF) reference: R30-4. Plate I, 1–3. Dimension: 41–45 μm.
Paratype: Sample 511–03R 03W 75–76 cm, slide #2 , EF reference: L25. Plate I, 4–5. Dimension: 42–44 μm.
Stratum typicum: DSDP Leg 71, Site 511, Lithological Unit 2, Subunit 2a.
Derivation of name: Named in recognition of the scientific achievements of Dr. Carlota Escutia, marine geologist and geophysicist of the University of Granada (Spain), expert of the geology of the Antarctic margin.
Diagnosis: Proximate cyst of intermediate size with spherical outline, lacking horns or protrusions. The cyst wall is relatively thin, rugulate and appears to be composed of a single layer; an endo- and periphragm are not distinguishable. Tabulation is protoperidinioid (pr, 4 , 3a, 7 , 1t, 3c, 5″′, 2″″), indicated by low parasutural ridges. The archeopyle is theropylic between the intercalary and apical series. Typically, the dorsal-apical region displaced, generally in the direction of the empty cyst. Specimens are therefore exclusively found folded and distorted.
Dimensions: Average diameter around 45 μm (n= 16, Holotype: 45– 50 μm).
Description: Peridinioid spherical cysts of intermediate size, lacking horns or protrusions. The outer wall surface of the cyst is rugulate, and exhibits faint parasutural ridges. These are difficult to discern under typical LM-magnification (Plate I) but reflect a protoperidinioid tabulation (pr, 4 , 3a, 7 , t, 3c, 5″′, 2″″) under SEM magnification (Plate II). A small, preapical plate (pr) is clearly distinguishable on SEM images (Plate II, 1 and 3) but is not discernable on LM specimens. Plate 1 is characteristically symmetric, as is typical in peridinioid dinoflagellates. The sulcal area (Plate II, 2) consists of one anterior plate (as), a right (rs) and a left (ls) sulcal plate and a posterior (ps) plate. The cingulum is divided on the ventral face with a small sulcal–cingular transitional plate (t). The plates 1c and 3c extend only along the ventral face and the cingulum on the dorsal face consists of a single wide plate (2c) (Plate II, 2), this is characteristic for the Protoperidiniaceae family. The archeopyle is often difficult to discern as result of folding and is theropylic. Parasutural splits occur along the anterior margins of the anterior intercalary plates (1a, 2a and 3a), which remain attached to the cyst (Plate I, 1, 2, 5, 7 and 11). Such splits also occur along the parasutures between the anterior intercalary plates 1a with 2a and 2a with 3aand between apical series (1a with 2 3 , 2a with 3 and 3a with 3 and 4 ). This generally leads to the folding of plate 2a and 3 (Plate II, 1) and displacement of the apical area (Plate I, 1–2; Plate II, 3).
Stratigraphic distribution: At Site 511, the lowest occurrence of Malvinia escutiana is in Sample Core 12R, Section 02 W, 115–117 cm. This level corresponds to an ~1.5 increase in foraminiferal δ18O (Houben et al., submitted for publication; see also Liu et al., 2009), interpreted to represent the Oi-1 isotope shift in the earliest Oligocene (see, e.g., Coxall and Pearson, 2007). This isotopic shift is dated as 33.7 Ma following the timescale ofGradstein et al. (2004). At Site 511 M. escutiana initially occurs sporadically up to Core 6R to occur consistently above it and even becoming quite abundant (~20% relative abundance) in Core 4R and 3R (~32 Ma). The range top of M. escutiana is at least younger than 31.5 Ma at DSDP Site 511 (Fig. 2; Houben et al., submitted for publication).
Geographic distribution: Malvinia escutiana has exclusively been recorded in the Southern Ocean, that is from DSDP Sites 511 and 513 (Goodman and Ford, 1983, Falkland Plateau) and from ODP Sites 693 and 696 (Mohr, 1990, Weddell Sea, early Oligocene). It has also been recorded from ODP Site 739 (P.K. Bijl, 2010 pers. obs., Prydz Bay).