Conicotheca, Gooday & Todo & Uematsu & Kitazato, 2008
|
publication ID |
https://doi.org/ 10.1111/j.1096-3642.2008.00393.x |
|
persistent identifier |
https://treatment.plazi.org/id/03BE87EC-983D-FF82-3427-FBCCDFD8F8E3 |
|
treatment provided by |
Felipe |
|
scientific name |
Conicotheca |
| status |
gen. nov. |
CONICOTHECA View in CoL GEN. NOV.
Type species: Conicotheca nigrans gen. et sp. nov.
Derivation of name: Refers to the shape of the organic theca (test).
Diagnosis: Test tiny (usually <120 Mm long), elongate, more or less conical in shape, tapering towards proximal end from widest point in distal third to quarter. Proximal end often slightly bulbous; distal end truncated or bluntly pointed with single terminal aperture that is round to elongated in shape. There are no internal subdivisions. Test wall mainly organic, transparent and colourless. Some areas smooth on submicrometre scale; other areas with scale-like surface pattern, probably due to presence of clay minerals. Test interior contains large, darkcoloured stercomata.
Remarks: The much smaller test size, the more compact, streamlined shape and the lack of a welldefined proloculus distinguish Conicotheca from Nodellum . The new genus differs from Resigella in the absence of chamber-like subdivisions. The tapered shape of the test is most similar to that of Micrometula , a monothalamous, organic-walled genus that occurs on the continental margins of north-west Europe and Svalbard ( Nyholm, 1952; Gooday et al., 2005; Majewski, Pawlowski & Zajczkowski, 2005). However, Conicotheca has a relatively shorter test and lacks the short apertural neck present in Micrometula . Another important difference is that the test of Coniotheca is filled with stercomata whereas that of Micrometula contains only cytoplasm.
In addition to the type species from the Challenger Deep, at least one species that can be assigned to this genus occurs at the abyssal Kaplan East site in the eastern Equatorial Pacific ( Nozawa et al., 2006).
CONICOTHECA NIGRANS GEN. ET SP. NOV.
FIGS 14–16 View Figure 14 View Figure 15 View Figure 16
Diagnosis: As for genus.
Types: The type specimens are deposited in Tokyo and London under reg. nos. MPC-02704 (holotype), MPC-02699-02703 (five paratypes) and ZF 5168 (six paratypes) .
Other material examined: 62 specimens
Derivation of name: Latin nigrans (black or dark) alluding to the dark appearance of this species due to the presence of stercomata within the transparent test.
Description
Test morphology: The test resembles an elongate cone with either a bluntly rounded or truncated distal (apertural) end ( Figs 14 View Figure 14 , 15A, B, F, G View Figure 15 ). It typically measures 80–120 Mm long and tapers from 23 to 35 Mm at the widest point in the anterior third to quarter to 9–13 Mm just in front of the rounded proximal end ( Table 3), which is often slightly bulbous. Occasionally, there is a rather abrupt decrease in width at some point along the length of the test ( Fig. 14D View Figure 14 ), possibly reflecting a growth discontinuity. A few specimens are larger, up to 156 Mm long and 52 Mm wide. The length/width ratio varies from 2.7 to 5.2 but is usually between 3 and 4. The position of the widest point varies from 16% to 42% of the length from the distal end; in more than three-quarters of specimens it is situated between one-fifth and onethird (25–33%) of the length from the distal end. In dried specimens viewed by SEM, the proximal end maintains a rounded shape whereas adjoining parts of the test tend to collapse ( Figs 15D View Figure 15 , 16D View Figure 16 ). It may represent a poorly defined proloculus.
Aperture: The aperture is difficult to see clearly by light microscopy. Some specimens have a rounded distal end and a relatively small aperture (e.g. Fig. 14I, J View Figure 14 ), but in many cases, the end of the test is truncated and the aperture appears to be more elongated (e.g. Fig. 14E, O, P View Figure 14 ). Examination of four specimens by SEM confirms the impression gained from light microscopy. In one individual ( Fig. 15A–C View Figure 15 ), the end of the test is rounded and the aperture forms a simple, oval opening measuring 5.5 by 3.0 Mm. In another ( Fig. 15F–H View Figure 15 ), the end is truncated and the aperture, although obscured by detritus, seems to be slit-like. The third specimen ( Fig. 16A, B View Figure 16 ) also has a truncated end, with a relatively large, elongate oval aperture, measuring 14 by 7 Mm. The aperture of a fourth specimen (not illustrated) forms a circular opening ~6 Mm across.
Wall structure and composition: The wall is mainly organic, transparent and colourless. A variable proportion of the test surface is rough and lumpy on a submicrometre scale. In places, the surface irregularities merge into irregularly shaped, scale-like features, <1 Mm in size, which form an imbricated pattern on the surface ( Fig. 16F View Figure 16 ). These rough surfaces are more extensively developed in some specimens than in others. The remaining areas of the test, and particularly the rounded, proximal end, are smooth on a submicrometre scale ( Figs 15D View Figure 15 , 16D View Figure 16 ), except for occasional, tiny, finger-like projections of the organic wall ( Fig. 16E View Figure 16 ).
EDS analyses of test areas covered by scale-like formations reveal strong peaks for Al and Si with
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.