Tetrapyle octacantha group
Description - Add description
|Benson, 1966, p. 245-250; pl. 15, figs. 3-10; pl. 16, fig. 1; text-fig. 18:|
Tetrapyle octacantha Müller
Tetrapyle octacantha Müller, 1858b, Akad. Berlin, Ahandl. (1858), p. 33, Pl. 2, figs. 12, 13, P1. 3, figs. 1-12; 1858a, Akad. Berlin, Monatsb. (1858), p. 154; Hertwig 1879, Der Organismus der Radiolarien, pp. 180-181, P1. 6, figs. 2, 2a, 4, 4a, 5, 5a.
Schizomma quadrilobum Ehrenberg, 1861, Akad. Berlin, Monatsb. (1860), p. 824; 1862, Akad. Berlin Monatsb. (1861), p. 301; 1873b, Akad. Berlin, Abhandl. (1872), Pl. 10, figs. 12-14.
Tetrapyle quadriloba Haeckel, 1862, Die Radiolarien, p.436; 1887, Challenger Rept., Zool., vol. 18, p. 645; Popofsky, 1912, Deutsche Südpolar-Exped., vol. 13, pp. 150-151, text figs. 70-72.
?Larnacalpis lentellipsis Haeckel, 1887, Challenger Rept., Zool., vol. 18, p. 620, P1. 50, fig. 2.
Amphipyle tetraceros Haeckel, 1887, op. cit.., p. 642, Pl. 9, fig. 5.
?Tetrapyle circularis Haeckel, 1887, op. cit., p. 645, Pl. 9, fig. 8.
?Octopyle sexangulata Haeckel, 1887, op. cit., p. 653, Pl. 9, fig. 12.
?Octopyle decastyle Haeckel, 1887, op. cit., p. 654, Pl. 9, fig. 13.
Pylonium quadricorne Haeckel, 1887, op. cit., p. 655, Pl. 9, fig. 14.
?Pylozonium novemcinctum Haeckel, 1887, op. cit., p. 659.
?Pylozonium octacanthum Haeckel, 1887, op. cit., p. 660, Pl. 9, fig. 16.
Monozonium pachystylum Popofsky, 1912, Deutsche Südpolar-Exped., vol. 13, pp. 146-147, text figs. 65, 66.
Amphipyle aspera Popofsky, 1912, op. cit., pp. 148-149, text figs. 67,68.
Amphipyle horrida Popofsky, 1912, op. cit., pp. 149-150, text fig. 69.
Complete tests consisting of two well-defined systems of latticed dimensive girdles, with few, if any, radial beams, and a third outer system of poorly-defined girdles supported by numerous short beams of approximately equal length that arise from the nodes of the intervening bars of the latticed girdles of the second system [pl. 16, fig. 1]. Most tests incomplete, consisting either of all or a portion of the second girdle system (transverse and lateral girdles with rudimentary sagittal girdle), but in several tests with some indication of the third girdle system in the form of numerous branched spines or incomplete outer girdles, generally representing the rudimentary, third transverse girdle. Pores of the latticed girdles relatively large, unequal, irregular to subregular in arrangement, generally subcircular to subpolygonal. Surface of complete specimens irregular, rough or spinose; surface of second girdle system relatively smooth to highly spinose. Outline of second lateral girdle generally ellipsoidal (major diameter the principal or P axis) but variable from subcircular to subquadrate. Gates defined by the transverse and lateral girdles of the second system generally elliptical to kidney-shaped, in a few specimens with beams lying in their plane and joining the transverse girdle with the rudimentary second sagittal girdle. Radial beams absent in many tests but when present generally lie in the axes of the test (P, T, or S), although in a few specimens they extend from the pole of the inner system of girdles at an acute angle with the axis. Beams arise from the inner ellipsoidal shell or ring but do not penetrate beyond the second girdle system as free spines; number of coaxial beams variable but generally six when present; a few specimens were observed with only one of a pair of opposite polar beams extending through the inner tubular space between gates; rarely more than one beam observed at each pole; tests without beams generally with short polar spines or thorns representing rudimentary beams. Specimens with eight diagonal spines, each originating from one of the eight edges of the second transverse girdle (Tetrapyle octacantha Müller) rare, with or without polar beams [pl. 15, figs. 8,9].
Measurements; based on 30 specimens from stations 27, 34, and 71: range in length of diinensive axes of each girdle system (see text-fig. 18):
P1 14-18 T1 9-12 S1 5-9
P2 39-65 T2 31-48 S2 15-25
P3 93-194 T3 70-156 S3 55-95
P4 215-246 T4 172-221 S4 121-221
Remarks. This species differs from Phorticium pylonium in the absence of numerous radial beams which, when present, occupy only the dimensive axes of the test, and in the presence of an irregular third system of girdles joined to the second system by numerous, short radial beams arising from the surface of the latter.
The synonymy of this species or species-group is based only on figures of specimens from the literature. The decision to name this species Tetrapyle octacantha rests not only on the fact that it was the first-named pylonid taxon but also because the eight diagonal spines characteristic of this species as defined by Müller (1858b, p. 33) were observed to be an intraspecific variation in specimens from the Gulf. The other species listed in the synonymy either are incomplete forms (ontogenetic stages) of this species, represent orientations other than the frontal orientation, or were observed from the Gulf with the outer or third girdle system complete as defined above.
After study of hundreds of individual pylonid tests I conclude that the species of this family present in the Gulf could all be placed within a single genus characterized by the presence of one or more concentric systems of latticed dimensive girdles with open. gates on the shell surface. Because the Gulf assemblage is a limited one and type specimens were not examined such a decision at this stage is premature. Revision of not only the Pyloniidae, but of the superfamily Litheliacea as well, is needed.
Distribution. This species is a predominant member of the Gulf assemblage. It occurs in greatest abundance in the southern part of the Gulf, being abundant at stations 27, 34, 46, 56, 60, and 71 with a maximum of 16.6% at station 34. It is abundant (10.6%) at station 92, common at all other stations except 130, 151, and 191 where it occurs rarely, and absent at stations 203 and 214. In contrast to the distribution of Phorticium pylonium which has maxima near the eastern and western shores of the Gulf with a decrease toward the axial part along the section occupied by stations 90-99, this species shows a higher frequency west of the Gulf axis than east of it. It occurs in much greater numbers in the southern Gulf than does P. pylonium. At stations located within the diatomite facies, namely stations 106, 115, 133, 151, 191, and 192, it occurs less commonly than at other stations within this general region, in particular, stations 184, 194, and 208 where its percentage ranges from 4.0-9.2 which is comparable to its frequency at some of the stations in the southern and central Gulf. Its decrease in the diatomite facies may be the result of its dilution by increases in the abundance of certain nasselline species. In the northern Gulf, notably at stations 184, 194, and 208, it does show a marked increase; thus, its distribution in this region is similar to the increases noted for Dip1op1egma banzare Riedel and Hexacontium enthacanthum Jĝrgensen.
Popofsky (1912, p. 151) states that according to Haeckel this species is cosmopolitan, occurring at the surface in the Mediterranean Sea and Atlantic, Indian, and Pacific Oceans. Its distribution in polar seas is unknown. Owing to the poorly known taxonomy of this species or species-group, it is difficult to decide from the literature alone the true nature of its distribution.
|This group differs from the Phorticium pylonium group in (1) the presence of few, if any, radial beams, which are generally confined to the regions of the dimensive axes of the tests, and (2) the presence, in fully developed individuals, of no more than three systems of girdles, the third being irregular and joined to the second system by numerous short beams arising from the surface of the latter (Benson, 1966, pl. 16, fig. 1).|