Phorticium pylonium group
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|Cortical shell irregular, roundish, about three times as large as the enclosed lentelliptical, regular, Larnacilla-shell, connected with it by some radial beams and irregularly latticed girdles; between these remain four to eight large open gates of irregular roundish form and size; and these gates are the same as in Tetrapyle and Octopyle. This very variable species may be regarded as a monstrosity of those genera of Pylonida; it is very common, but all individuals are more or less unequal; some specimens approach to some common species of Tetrapyle. The surface of the shell is more or less spiny.|
Dimensions.—Diameter of the irregular cortical shell 0.12 to 0.18; length of the lentelliptical medullary shell 0.05 to 0.06, breadth 0.035 to 0.45.
|Benson, 1966, p. 252-256; pl. 16, figs. 5-9; pl. 17, figs. 1-3:|
Phorticium pylonium (Haeckel) Cleve
Phorticium pylonium Haeckel, 1887, Challenger Rept., Zool., vol. 18, p.709, Pl. 49, fig. 10; Cleve, Kongl. Svenska Vetenskap-Akad., Handlingar, 1899, p. 31, Pl. 3, figs. 2a-d.
Phorticium pylonium (Haeckel?) Cleve; Jørgensen, 1905, Bergens Mus. Skrifter, pp. 120-121, Pl. 10, figs. 42a-d; Pl. 11, figs. 42e-f, 43-45d.; Riedel, 1958, B.A.N.Z.A.R.E. Repts., ser. B, vol. 6, pt. 10, p. 229, Pl. 2, fig. 5.
Octopyle octostyle Haeckel f. minor Jørgensen, 1900, Bergens Mus. Aarbog, p. 64.
Tetrapylonium clevei Jørgensen, 1900, op. cit., p. 64.
Tests consisting of one to five systems of dimensive girdles supported by numerous (20-30 to 100 or more), cylindrical radial beams which continue beyond the relatively smooth, outer, ellipsoidal shell as conical spines. Girdles variable from regular, thin-walled with smooth surface and subregular pores to irregular, thick-walled with rough surface and irregular pores. Girdles of the outer system or systems more irregular than those of the inner systems; distance between girdle systems (concentric ellipses) variable. Gates on shell surface open or closed depending upon the degree of development of the outer girdle system. Outer shell of complete tests ellipsoidal with loss of definition of individual girdles; pores highly variable in size and shape; outline of outer shell generally regular. Radial beams variable in number; beams if occupying the three dimensive axes not distinguishab1e in size or shape from the others. Number, length, and breadth of surface spines highly variable; spines of several tests from diatomite regions more numerous than average (500-1000 or more), generally thin, very long (up to 80 µm).
Measurements; based on 30 specimens from stations 71, 81, 136, and 184: range in length of dimensive axes of each girdle system [see Benson, 1966, text-fig. 18 under Tetrapyle octacantha group]:
P1 15-33 T1 10-21 Sl 9-10
P2 37-81 T2 31-68 S2 15-39
P3 86-148 T3 68-154 S3 46-111
P4 138-194 T4 123-185 S4 103-180
Major diameter of outer ellipsoidal shell 111-283 µm, minor diameter 86-241 µm; length of surface spines 8-80 µm.
Remarks. This species differs from Tetrapyle octacantha Müller in the presence of numerous radial beams of variable number, at least 20 to 30. The outermost system of trizonal girdles is supported by these same radial beams, not by numerous short beams arising only from the surface of the second girdle system.
The taxonomy of this group at present is confused. It is my opinion that this group as present in the Gulf should best be regarded as a species-group rather than a separate species. It is a highly variable group and could be subdivided. As many as five systems of trizonal girdles were observed. The girdles vary from regular to irregular in outline. The distance between girdle systems is variable. Common to all tests, however, is the presence of numerous radial beams, and in complete specimens the outer shell is a large, relatively smooth (except for main spines), ellipsoidal shell. In random orientations on strewn slides the interior girdles are observed as either a concentric system of elliptical shadows or a double spiral. In wet slides, specimens showing a spiral structure were reoriented to positions in which the concentric structure became apparent. Thus, many of the species originally described as having an internal spiral arrangement may actually belong to this species or species-group, for example, Lithelius primordia1is Hertwig (1879, pp. 182-183, Pl. 6, fig. 4), Spirema melonia Haeckel (1887, p. 692, Pl. 49, fig. 1), Lithelius solaris Haeckel (1887, p. 695, P1. 49, fig. 2), Tholospira cervicornis Haeckel (1887, p. 700, Pl. 49, fig. 5), Popofsky (1912, p. 152, text fig. 73), Tholospira dendrophora Haeckel (1887, p. 700, Pl. 49, fig. 6), Streblacantha circumtexta Jørgensen (1905, pp. 121- 122, Pl. 11, fig. 46, Pl. 12, fig. 46), Lithelius nautiloides Popofsky (1909, p. 230, Pl. 27, figs. 2-4), and Lithelius obscurus Popofsky (1909, p. 231, Pl. 27, figs. 5, 6; Pl. 28, fig. 3-5; also possibly the form illustrated in Pl. 28, fig. 9).
This species or species-group from the Gulf is identified as Phorticium pylonium (Haeckel) Cleve mainly on the basis of Riedel' s (1958, p. 229) identification of Antarctic forms, which are similar if not the same species as the Gulf forms, with Cleve's species. Because numerous tests have three to four concentric systems of trizonal girdles, one objectively would place them within the genus Pylozonium Haeckel (1887, p. 659), although the gates of the outer shell are closed by the girdle systems. The illustrations of the species listed in the synonymy all resemble the Gulf forms, but Haeckel's only illustration of Pylozonium (P. octacanthum Haeckel, 1887, p. 660; Pl. 9, fig. 16) does not show the numerous radial beams characteristic of the Gulf species and is more like a fully developed form of Tetrapyle octacantha Müller..
Distribution. This species or species-group is an important member of the Gulf assemblage. In my counts, any large ellipsoidal test with numerous radial beams having an internal structure appearing as either widely spaced, concentric, elliptical shells or a double or single spiral (but not Larcospira guadrangula Haeckel) was included within this species-group. It is abundant at stations 91 and 99 (maximum at station 91 of 17.4%) and common at all other stations except station 191 where it is rare and stations 203 and 214 where it is absent. Its highest frequencies are at stations 91 and 99 (17.4% and 14.0%, respectively) and are much greater than its next lower percentages in the Gulf at stations 95 and 92 (9.2% and 9.0%, respectively). This suggests a response of this species to upwelling along the western and eastern margins of the Gulf here. However, because this species is relatively large, its increased frequency at these upper slope stations may be influenced by sorting processes as well. The cosmopolitan distribution of this species suggests that it is tolerant of the slightly higher salinities and temperatures and greater ranges in these properties in the Gulf.
If all the species listed in the synonymy and the remarks above are the same, this species has a cosmopolitan distribution. Riedel (1958, p. 229) states that the present unsatisfactory state of the taxonomy of this group makes it impossible to determine the distribution of one species relative to another, a statement with which I agree.
|Remarks. This group differs from the Tetrapyle octacantha group in (1) the presence of more than three (as many as five) systems of dimensive girdles supported by numerous radial beams (20-30) not confined to the region of the dimensive axes of the test, and (2) the presence, in fully-developed individuals, of an ellipsoidal outer shell of smooth [although spiny] outline (Benson, 1966, pl. 17, figs. 1-3; this chapter, Plate 7, Fig. 15) similar to the outer shell of Hexapyle dodecantha and Larcopyle bütschlii. This group is a difficult one to work with because in certain orientations individuals appear as a double spiral (Benson, 1964, pl. 1, fig. 61; 1966, pl. 16, figs. 5, 8) and in others as a concentric system of elliptical shells (Benson, 1966, pl. 16, fig. 9; this chapter, Plate 7, Fig. 16).|