Skeletonia, Gooday & Kamenskaya & Cedhagen, 2007
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publication ID |
https://doi.org/ 10.1111/j.1096-3642.2007.00326.x |
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persistent identifier |
https://treatment.plazi.org/id/CC41BE6E-FFF7-3A7F-5972-FB2D2E59F944 |
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treatment provided by |
Felipe |
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scientific name |
Skeletonia |
| status |
gen. nov. |
SKELETONIA View in CoL GEN. NOV.
Diagnosis: Test consisting of initial (proximal) cluster of globular, grape-like or more elongate chambers followed by small number of relatively wide, stiff, crooked, tubular processes, typically 80–100 µm in diameter. These usually arise from either side of the longitudinal growth axis and increase in length from proximal to distal; however, the growth axis is sometimes compressed, obscure or lacking. Tubular processes are sometimes interrupted by internal septa.
Type species: Skeletonia variabilis gen. et sp. nov.
Derivation of name: The generic name reflects the skeletal appearance of the test, which is particularly apparent in specimens with a distinct direction of growth.
Remarks
The test of this new genus comprises a series of elongate elements, usually with length/width ratios <5. We term these ‘tubular processes’ because they are relatively wider than the tubules of typical komoki- aceans. This raises the question of whether Skeletonia is a true komokiacean. However, the general disposition of the tubular processes, the frequent presence of a proximal cluster of grape-like chambers and the development of septa are reminiscent of members of this superfamily. The basically elongate morphology, the frequent development of tubular processes from a more or less irregular central axis and the initial cluster of globular chambers are all reminiscent of the genus Baculella . Unlike species of this genus, however, there is no axial tubule. Instead, the axis, where present, is created by the bases of the lateral tubular processes and the short, stolon-like necks that link them together. The tubular processes are also much larger and more robust than the beadlike chambers of Baculella . Because the relationship of Skeletonia to other komokiaceans is presently unclear, we hesitate to place it in any particular family.
An undescribed species of Skeletonia occurs in the Porcupine Abyssal Plain (north-east Atlantic) (A.J.G. & O.E.K., unpubl. observ.). It differs from the type species described below in having rounded rather than tubular lateral processes.
SKELETONIA VARIABILIS GEN. ET SP. NOV.
( FIGS 16–18 View Figure 16 View Figure 17 View Figure 18 )
Diagnosis: As for genus.
Type material and locality: The holotype and three paratypes were collected from Stn 88#8, using an epibenthic sledge; 68°3.61′S, 20°27.52′W to 68°3.85′S, 20°31.42′W; 4927–4932 m water depth. They are preserved in 4% buffered formalin and deposited in the Forschungsinstitut Senckenberg, Frankfurt am Main, under reg. nos SMF XXVII 7533 (holotype) and SMF XXVII 7534 (paratypes) GoogleMaps .
Other material examined: Stn 88#8, 11 additional specimens; Stn 94#11, 3 specimens; 102#13, 13 specimens; 110#8, 2 specimens.
Derivation of name: Latin variabilis = variable, alluding to the variable appearance of the test.
Description of type material
Holotype: Length 1.45 mm, width 0.20 mm at the proximal end widening to 1.20 mm at the distal end ( Fig. 16A, C View Figure 16 ). The test is flattened and the height (with the test orientated so that the height is at a minimum) is 0.65 mm. The initial part consists of an irregular cluster of globular to droplet-shaped chambers, each ∼80 µm in diameter ( Fig. 16B View Figure 16 ). These are succeeded by a series of stiff, tubular processes (in effect, broad tubules), which increase in length and width along the length of the test. The test has a fairly distinct axis of growth created by the bases of the tubular processes, which are linked together by narrow constrictions or short, tubular, stolon-like necks, ∼20 µm in width. At the proximal end of the test, the processes are 120– 220 µm long and 60–80 µm wide with a length/width ratio of 4.5–6.5; at the distal end they are 600–700 µm long and 80–140 µm wide with a length/width ratio of 3–4. Most of them branch dichotomously once or twice. The processes project outwards from the central growth axis and slightly forwards. Some lie in a more or less horizontal plane while others extend upwards or downwards. They tend to arise alternately on either side of the test. However, the pattern is not regular and the general arrangement of the processes is somewhat haphazard. The ends of some processes are flattened, others are more rounded.
Paratype 1: Length 1.50 mm, width increasing from 0.50 mm at the proximal end to 1.20 mm at the distal end; height ∼ 0.90 mm. This individual is larger than the holotype and has a rather more complex test ( Fig. 16F View Figure 16 ). As in the holotype, the initial part comprises a cluster of globular chambers, each 75–100 µm in diameter. The tubular processes extend forward at an angle from the direction of growth and have a length/width ratio of 4–5. However, they are more numerous and rather less regular in form than those of the holotype; in most cases the processes branch dichotomously or have short lateral protuberances. The axis of growth is also more irregular than in the holotype and follows a somewhat curved course. The axis consists mainly of short, stolon-like necks which join together the bases of the tubular processes.
Paratype 2: Length 1.20 mm, width increasing from 0.40 mm at the proximal end to 0.80 mm at the distal end; height ∼ 0.40 mm. This is a smaller and morphologically rather simpler individual than either the holotype or paratype 1 ( Fig. 16D View Figure 16 ). The initial part consists of only two small, closely adjoining chambers (∼75 µm in diameter), but in other respects the morphology is similar. The tubular processes are linked at their bases by stolon-like necks to form an irregular axis. The processes are ∼100 µm in diameter, range in length from ∼270 µm near the proximal end (length/width ratio ∼3) to ∼500 µm near the distal end (length/width ratio ∼5). They are rather irregular and most branch or have lateral protuberances.
Paratype 3: Length ∼ 0.80 mm, width 0.30–1.1 mm. A small specimen with a clearly developed cluster of about six small, globular chambers (50–100 µm in diameter) at the initial end; these are attached to the rest of the test by a short neck, ∼20 µm in width ( Fig. 16E View Figure 16 ). The short growth axis consists of similar, stolon-like necks. There are rather few tubular processes, ∼80 µm in width (length/width ratio 3–5) and in some cases branched, extending out from the central axis.
Description of other specimens
Stn 88#8: Eleven additional specimens from the type locality are 0.75–1.25 mm long, 0.62–1.14 mm wide with a length/width ratio of 0.96–1.68; the width/ height ratio is 1.2–1.5. In six of the 11 specimens, the proximal cluster of small, grape-like chambers is clearly developed and contrasts with the latter part of the test. As in the type specimens, the main part of the test consists of thick, branched tubular processes, joined at their bases by short necks or constrictions. Four specimens have a distinct direction of growth, with the lateral processes arranged on either side of the axis. In other cases, however, the growth axis is either compressed and difficult to see ( Fig. 17C View Figure 17 ), or there is no clear direction of growth ( Fig. 17A, D–F View Figure 17 ). The tubular processes are typically ∼100 µm wide, although the width varies in an irregular manner along the length; in smaller specimens they may be only 60 µm in width. The processes often branch dichotomously.
The test has a smooth outer surface. The wall is composed of a mosaic of angular grains, typically 10–40 µm in size, with the gaps between them filled by smaller grains. Most are composed of quartz, but dark grains of various sizes are also present. A few large quartz particles several hundreds of micrometres in diameter sometimes project from the surface of the wall. The interior of the tubular processes may be interrupted by transverse septa ( Fig. 17B View Figure 17 ). These are difficult to visualize through the rather coarsely agglutinated test wall, even when specimens are examined in glycerol. However, careful examination sometimes reveals several septa within one tubular process. The test contains stercomata.
Stn 94#11: Three small specimens, ranging in length from 0.80 to 1.00 mm and broadly similar to those from Stn 88. All have a cluster of small chambers at the proximal end. The axis of the test along which the tubular processes join is irregular.
Stn 102#13: Six larger specimens are 1.04–1.53 mm long and 0.67–1.33 mm wide with a length/width ratio of 1.14–1.79; the height is generally less than the width of the test (width/height ratio = 0.92–1.80). Two of these six specimens have a clearly developed cluster of small chambers (60–80 µm) at the proximal end ( Fig. 18B View Figure 18 ); in the others, the proximal part of the test consists of elongate, tubular elements (width ∼60 µm) ( Fig. 18A View Figure 18 ). Four specimens exhibit a more or less distinct direction of growth with elongate processes (tubes ∼80 µm width) arranged on either side of the growth ‘axis’ formed by the bases of the processes ( Fig. 18C, D View Figure 18 ). These are separated by constrictions rather than by the stolon-like necks developed in the type specimens. In one case, a tubular process extends along the axis between the branches. Another 12 specimens are smaller (length = 0.42–0.74 mm; width = 0.27–0.57 mm). Most have no clear direction of growth and consist of a few irregular tubular processes, which arise from a central area ( Fig. 18C, D View Figure 18 ).
Stn 110#8: Two small specimens comprise a few tubular processes with no clear direction of growth. Stolonlike necks are clearly developed between the bases of some processes.
Remarks
This species exhibits considerable variability. All specimens possess a series of relatively wide, tubular processes, but their disposition is not consistent. In some individuals, there is a more or less distinct direction of growth, the axis of which is usually formed by the bases of the tubular processes and the short, stolonlike necks that sometimes link them together. However, this axis often follows an irregular course and sometimes is very contorted, compressed or not discernible at all. The initial part, where visible, often consists of a cluster of globular chambers, but in some specimens these are replaced by small, tubular structures.
Distribution
Central Weddell Sea (4696–4932 m water depth).
| SMF |
Forschungsinstitut und Natur-Museum Senckenberg |
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.