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Macromckenziea giambonini Brandão, 2010
- class Ostracoda Latrielle, 1806
- subclass Podocopa Müller, 1894
- order Podocopida Sars, 1866
- suborder Cypridocopina Jones, 1901
- family Macrocypridoidea Müller, 1912
- family Macrocyprididae Müller, 1912
- genus Macromckenziea Maddocks, 1990
Overview
General Description
Description. Carapace medium-sized (for the genus), non-equilateral, elongate in lateral outline, narrow zone of concrescence with straight radial pore canals, calcified inner lamella narrow. Greatest height at midlength in RV and anterior to mid-length in LV. Length approximately 2.3 times maximum height. RV larger than LV. Anterior margin of both valves narrowly rounded, dorsal margin gently arched, posterior margin rounded, ending in 90º posterior angle. Ventral margin straight in RV, and slightly concave in LV. Anterodorsal margin fairly straight in RV, slightly concave in LV.
Antenna I robust, thick, tapering, with 7 podomeres; Podomere II and III flexibly articulated. Antenna II compact, thick-proportioned, tightly curled, with 6 podomeres; podomere IV short and thick. Mandible with a broad masticatory jaw armed with one dorsal, conical tooth followed by four tricuspidate teeth and several setae. Maxilla I with three slender endites, each armed distally with a dense fringe of subequal claws, ventral endite with 2 proximal setae on ventral margin, other 2 endites without proximal setae; vibratory plate with 1 strahlen and ~14 to ~17 feathered setae; palp slender, flexible; podomeres I and II fused, dorsal seta of podomere I absent). Exopodite of female appendage V with 7 setae; podomeres IV and V with long and thin setae, mid-distal seta conspicuously longer than other 3 setae. Podomere IV and V of appendage VI short; podomere VI elongate, with 2 subequal, medium-sized, distal claws and one short distal seta. appendage VII thin and small; podomere V with 2 ventrodistal, medium-sized setae, the most ventral one shortest; and with one very short reflexed-seta. Furca very small, each rod flexible and bearing 2 tiny proximal setae and one terminal, short seta.
Adult chaetotaxy. Antenna I 1, 2(0/.2), 3(.1/.1.), 4(.1/.1.), 5(.1/.1), 6(.2/.3), 7(0/0:3-4). Antenna II 1(0/0:1), 2(0/0:1), Exopodite (0/0:2,1r), 3(0/5.:5), 4(.2/.1c:3), 5(0/.1,1c:1.3c), 6(0/0:4c,1s). Mandible 1(0/5t,+5:.1.), 2(0/.2), Exopodite (0/0:5), 3(0/5:1), 4(5/4), 5(.2./0:3). Maxilla I vibratory plate (1re,~14-16), palp 1+2(4/0), 3(0/0:5). Appendage V F 1, Exopodite (.3./0:4), 2, 3, 4(0/1), 5(0/0:3). Appendage VI 1(0/.1), 2(.1/.1.1.1), 3(0/.1), 4(0/.1), 5(0/.1), 6(0/0:2c,1). Appendage VII 1+2(.1/.1), 3(0/1), 4(0/1), 5(0/1), 6(0/0:1.1r,1). Furca 1(0/0:1.2r).
LV, left valve; RV, right valve.
For chaetotaxy formula, see Schornikov EI, Keyser D. 2004. The morphology and classification of Paradoxostomatinae (Ostracoda) from the nearshore zone of Madeira and the Canary Islands. Revista Espanola de Micropaleontologia 36: 57-81
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Description
Diagnostic Description
Carapace medium-sized. In lateral view, elongate; with slightly arched dorsal margin; and straight (RV) or slightly concave (LV) ventral margin; posterior margin pointed at 90°. Zone of concrescence very narrow with short, straight radial pore canals. Podomeres I of maxilla I without seta. Podomere V of female appendage V with very long mid-distal seta. Furca reduced, with 2 rods, each rod flexible and bearing 2 tiny proximal setae and one terminal, short seta.
LV, left valve; RV, right valve.
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Comparisons
Macromckenziea giambonini Brandão, 2010 fits well in the description of the genus Macromckenziea except for the furca, which is more similar to the genera Macrocypris Brady, 1868 and Macropyxis Maddocks, 1990. In the new species the furca is less reduced than the furca of the other species in Macromckenziea. In this character, Macromckenziea giambonini Brandão, 2010 differs from all other species of Macromckenziea, for which the appendages have been figured-Macromckenziea glacierae, Macromckenziea ligustica and Macromckenziea siliquosa (Maddocks 1990. Fig. 46.20-34). Additionally, Macromckenziea australiana, Macromckenziea glacierae, Macromckenziea gregalis, Macromckenziea porcelanica, and Macromckenziea swansoni are more subtriangular, higher in relation to length than Macromckenziea giambonini Brandão, 2010 Furthermore, Macromckenziea glacierae presents a more pointed posterior angle than Macromckenziea giambonini Brandão, 2010 Macromckenziea ligustica and Macromckenziea siliquosa have more sub-parallel ventral and dorsal margins, more straight dorsal margin and more sinuate ventral margin than Macromckenziea giambonini Brandão, 2010 The valves of Macromckenziea sp. 3 from Maddocks (1990: 56), which was recorded from the Drake Passage (240m), are very similar to the Macromckenziea giambonini Brandão, 2010, but smaller (gray triangle in Fig. 7), with a slightly more truncated anterior margin, and its antenna I is more robust, with the podomeres wider in relation to length than in Macromckenziea giambonini Brandão, 2010 Macropyxis andreseni and Macropyxis sonneae, from the Pacific Sector of the Southern Ocean, present similar carapace outlines, but are higher in relation to length, and present well developed furca, while in Macromckenziea giambonini Brandão, 2010 the furca is reduced.
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Look Alikes
Valves of females of Macromckenziea giambonini Brandão, 2010 are very similar to the valves of males of Macromckenziea glacierae Maddocks, 1990.
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Size
Holotype, RV L 1.56mm, H 0.68mm; LV L 1.54mm, H 0.64mm. Paratypes, A F, RV, L 1.56-1.60mm, H 0.68-0.70mm; (A-1) RV, L 1.34-1.38mm, H 0.56-0.60mm.
(A-1), last juvenile instar; H, Height; L, length; LV, left valve; RV, right valve.
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Genetics
Few COI, ITS and 16S sequences were obtained by myself and collaborators and will be soon available in the GenBank.
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Ecology and Distribution
Distribution
Recent. Eastern Weddell Sea, Southern Ocean, from 924 to 934m
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| File | Size (kb) | Uploaded |
|---|---|---|
| Mk giambonini + Mk glaciera - geo and size.jpg | 570.7 | 2009-09-23T12:46:01Z |
| Fig. 11 Mk giambonini Valves Kopie.jpg | 462.9 | 2009-09-30T18:05:44Z |
| Fig. 11 Mk giambonini MuS Kopie.jpg | 218.5 | 2009-09-30T18:07:05Z |
| Fig. 12 31.2 Mk. giambonini - NOVO 03 -ZJLS Kopie.jpg | 2243.6 | 2009-09-30T18:15:37Z |
| Mk giambonini ApVII Fu.jpg | 441.5 | 2009-09-30T18:21:09Z |
Brandão, Simone N.. 2009. Taxon page for Macromckenziea giambonini Brandão, 2010. In: Ostracoda, http://ostracoda.lifedesks.org/pages/4178. First Created: 2009-09-23T12:44:15Z. Last Updated: 2009-09-30T18:43:54Z.