A New Species of Polyzoan, and Notes on Taxonomy
[Read by title before Otago Branch on 5th May, 1953; received by Editor, 10th May, 1953.]
Chiastosella cnigma, sp. nov, appears to bridge the gap between Chiastosella Canu & Bassler (Family Schizoporellidae) and Calloporina (Family Microporellidae). It is not proposed, however, to complicate the nomenclature at this stage by uniting the species concerned under a single genus.
I. Amongst the Cheilostomata Ascophora, the family Microporellidae has been separated since 1880 (Hincks, p. 204) and restricted, inter alia, to those species possessing a semicircular, holostomatous orifice with a straight or very slightly concave proximal lip, and an ascopore or trypa perforating the frontal wall along the median line. This ascopore, on the proximal side of the orifice, permits the passage of water to the compensation-sac or ascus. In these ways, such species have been readily distinguished from those relegated to the family Schizoporellidae in which the orifice is schizostomatous, the proximal lip of the orifice being interrupted by a well-marked sinus opened or closed by the insertion of a corresponding projection on the proximal end of the operculum.
Species classified as Microporellidae have occasionally been recorded that possess an ancestrula with a schizoporelliform orifice (e.g., see Harmer, 1902, p. 325; Levinsen, 1909, p. 19), and Harmer (op. cit., p. 336) has suggested that the ascopore has probably resulted from the closure of such a sinus. So far as I am aware, however, no example has yet been cited of such a phylogenetic trend, although it has been suspected Recently, however, a new species of Chiastosella (a schizoporellid) has been discovered that appears clearly to bridge the artificial barrier of “natural classification” set up between the Microporellidae and the Schizoporellidae. In fact, an earlier suggestion (Brown, 1952, p. 219) is now fully confirmed that Chiastosella and Calloporina (a microporellid) are really congeneric, in so far as a genus is a grouping together of a number of related species.
If we accept Harmer's suggestion (1902, p. 336) that Microporella s.l. is a distinct step in advance of Schizoporella sl and “Lepralia”, then the phylogenetic trend involving development of an ascopore by closure of a schizoporelliform sinus is illustrated by the following series (as yet with no firm stratigraphical basis):—
Chiastosella porosa Canu & Bassler—wide, rounded sinus (cf. Stach, 1937, Pl. 18, fig. 8).
Chiastosella conservata (Waters)—narrow, shallow sinus (cf. Stach, 1937, Pl. 18, figs. 6, 7).
Chiastosella enigma, sp. nov.—narrow, deep, slit-like sinus (Fig. 1A).
Calloporina angustipora (Hincks)—narrow, slit-like ascopore (Fig. 1C).
Calloporina lata (MacGillivray)—semi-lunar ascopore (Fig. 1B).
Note.—The last two species are not regarded as varieties of Calloporina diadema (MacGillivray).
While this is a clear case illustrating the unsatisfactory nature of the present classification of the Ascophora, I am sure that there is far too little known about that sub-order to justify any drastic change such as uniting these species and others (see below) under the heading of Calloporina Neviani, which is the earlier generic name.
The nature of the proximal lip of the orifice has generally been regarded as a firm character upon which to base generic differences at least, but in the series of species cited above which may, after all, simply be landmarks in a continuum of merging transients forming a developmental series, the important characters appear to be the nature of the ovicell and the oral spines, and the areolation of the frontal wall.
II. There now follows the description of a species which appears to form a link between Chiastosella on the one hand and Calloporina on the other. It is relegated to the former genus for reasons given below.
Chiastosella enigma,* sp. nov.
Holotype.—Recent: Inner Island Bay Bank, Wellington, New Zealand. Specimen encrusting siderite concretion. Geology Department, University of Otago. Presented by Dr. C. A. Fleming.
Diagnosis: Chiastosella (see Brown, 1952, p. 219, for definition) with arched, semicircular orifice possessing a narrow median sinus on the proximal lip. Large, paired, acuminate avicularia on either side of the orifice. Four or five stout, distal spine-bases. Frontal wall with large marginal areolae. Ovicell large, the ectooecium marginal, with areolae.
Description: Zoarium encrusting.
Zooecia large, hexagonal, arranged quincuncially in radiating rows, distinctly separated by shallow furrows. Orifice semicircular, highly arched, the proximal lip straight, with a narrow, median, deep, slit-like sinus. Peristome slightly thickened and raised, bearing, in non-ovicelled zooecia, four or five stout spinebases, the proximal pair larger. Frontal wall slightly convex, smooth centrally, with one or two rows of rounded, marginal areolae, often bearing a transverse umbo at a short distance from the orifice.
Avicularia paired, acuminate, placed outside and at the proximal corners of the orifice, their long rostra directed outwards along the zooecial margins.
Ovicells hyperstomial, large, the ectooecium raised and confined to the distallateral margin, bordered with large, rounded areolae. The ovicelled zooecia with a pair of stout spine-bases at the corners of the orifice, and a second pair within the orifice of the ovicell.
Lz = 0·50–0·58 mm. lz = 0·50–0·55 mm.
(excluding sinus) hr = 0·10–0·12 mm. lr = 0·09–0·11 mm.
Ovicell L = 0·38–0·43 mm. l = 0·33–0·35 mm.
[Footnote] * Gk. [ unclear: ] αγμα “a riddle”, referring to the doubtful generic position.
Fig. 1 A.—Chiastosella enigma, sp. nov Nukumaruan sandstone, Waipukurau, New Zealand Paratype. Ovicelled zooecium with portion of another on left and of a nonovicelled zooecrum on right Jelly Collection, Manchester Museum.
Fig 1 B—Outline diagram of Calloporina lata (MacGillirvay) Recent Port Phillip Heads, Victoria. 97.5.1 670 Bracebridge Wilson Collection, British Museum (Natural History).
Fig 1 C—Outline diagram of Calloporina angustipora (Hincks). Castlecliffian CU2c, N.Z Geological Survey Loc 4103, Castlecliff New Zealand D. 36814, British Museum (Natural History).
Remarks: The first indication of the possible relationship between Calloporina and Chiastosella was that given by Maplestone (1902, p. 66) when he noted the remarkable similarity of the ovicells in Schizoporella (= Chiastosella) convexa MacGillivray and Microporella (= Calloporina) diadema MacGillivray sp.
My attention was first drawn to this problem while studying the collections of Polyzoa in the Manchester Museum. There I discovered a specimen from Waipukurau, New Zealand (Nukumaruan—[Middle Pliocene]) labelled “M. decorata Rss. var. lata McGill.” by Miss Jelly. This clearly referred to Microporella decorata (Reuss) var. lata MacGillivray var. (= Calloporina lata (MacGillivray), 1885, p. 112, Pl. 4, fig. 5). Careful examination of the species, however, revealed that the zooecial orifice is provided with a narrow, median sinus and not with a semi-lunar ascopore as in MacGillivray's species.
Since then, I have found a well-preserved Recent specimen which I have made the holotype of this species, and as the genus Chiastosella is undoubtedly the most satisfactory pigeon-hole on the present basis of classification, I have relegated the species there.
Other Material: Paratype. Waipukurau, New Zealand (Nukumaruan—[Middle Pliocene]). 1 specimen encrusting a shell fragment. Labelled “M. decorata Rss. var. lata McGill” by Miss Jelly. Jelly Collection, Manchester Museum.
III. The following species have been referred to Chiastosella and Calloporina. The validity of those relegated to the latter genus cannot be finally confirmed in the absence of an examination of Reuss's material of the genotype which is a Miocene species from the Leithakalk of Nussdorf, near Vienna, Austria, and Eisenstadt, Hungary. The appropriate references will be found in Brown (1952, pp. 388–399).
(a) Chiastosella Canu & Bassler, 1934.
conservata, Schizoporella, Waters, 1881, p. 340, Pl. 18, fig. 81.
conservata, Schizoporella, Waters, 1882a, p. 273, Pl. 7, fig. 7 (non Waters, 1881; = C. daedala MacGillivray sp.).
convexa, Schizoporella, MacGillivray, 1895, p. 85, Pl. 11, fig. 21.
daedala, Schizoporella, MacGillivray, 1887a, p. 180 (nom. nov. for S. insignis MacGillivray, pre-occupied).
daedala, Schizoporella, MacGillivray, 1895, p. 84, Pl 11, fig. 15 (non MacGillivray, 1887; = C. porosa Canu & Bassler).
diagonalis, Chiastosella, Brown. 1952, p. 223, figs. 158–160.
gabrieli, Chiastosella, Stach, 1937b, p. 336, Pl 18, figs. 3, 4.
grandicella, Chiastosella, Canu & Bassler, 1935, p. 26, Pl. 6, fig. 3.
granulata, Schizoporella, MacGillivray, 1895, p. 87. Pl. 11, fig. 27.
insignis, Schizoporella, MacGillivray, 1883a, p. 132, Pl. 2, fig. 11 (non Hincks, 1881; = C. daedala MacGillivray sp.).
parviporosa, Chiastosella, Canu & Bassler, 1935, p. 27, Pl. 6, fig. 10.
porosa, Chiastosella, Canu & Bassler, 1935, p. 26, Pl 6, fig. 4.
watersi, Chiastosella, Stach, 1937b, p. 336, Pl 18, fig. 5.
(b) Calloporina Neviani, 1895.
form angustipora, Microporella diadema, Hincks, 1885, p. 249, Pl. 8, figs. 3, 3a.
canaliculata, Lepralia, MacGillivray, 1860a, p. 98, Pl. 1, figs. 3, 3a, 3b.
decorata, Cellepora, Reuss, 1848, p. 89, Pl. 10, fig. 25.
decorata, Calloporina, Canu & Lecointre, 1928, p. 61, Pl. 7, fig. 8 (non Reuss, 1848; = C. parvicella Canu & Bassler).
diadema, Lepralia, MacGillivray, 1869, p. 133.
var. lata, Microporella diadema, MacGillivray, 1885a, p. 112, Pl. 4, fig. 5.
var. longispina, Microporella diadema, MacGillivray, 1885a, p. 112, Pl. 4, fig. 4.
lunata, Lepralia, MacGillivray, 1860b, p. 166, Pl 2, fig. 6.
var. lumpuncta, Microporella diadema, MacGillivray, 1885a, p. 111, Pl. 4, fig. 3.
napierensis, Calloporina, Brown, 1952, p. 265, figs. 197, 198.
parvicella, Calloporina, Canu & Bassler, 1930, Ann. Stat. Ocean. Salammbô, 5, p. 48 (nom. nov for C. decorata Canu & Lecointre, 1928)
renipuncta, Microporella, MacGillivray, 1883a, p. 130, Pl. 1, figs. 1, la.
scandens, Microporella, MacGillivray, 1885a, p. 111, Pl. 4, fig. 7.
sculpta, Calloporina, Canu & Bassler, 1929, p. 334, Pl. 40, figs. 7, 8.
sigillata, Calloporina, Canu & Bassler, 1929, p. 333, Pl, 40, figs. 9, 10.
My grateful thanks are due to the Keepers of the Departments of Zoology and Geology in the British Museum (Natural History) for access to the collections; to Dr. P. M. Butler, of the Manchester Museum, for access to the Jelly Collection at the Manchester Museum; and to Dr. C. A. Fleming, of the New Zealand Geological Survey, for the material from which the holotype was taken.
Brown, D. A. 1952. The Tertiary Cheilostomatous Polyzoa of New Zealand. British Museum (Natural History), London., xii + 405 pp.
Harmer, S. F. 1902. On the Morphology of the Cheilostomata Quart. Journ. Micr. Sci. London, (n s.) 46, pp. 263–350, Pls. 15–18.
Hincks, T. 1880. A History of the British Marine Polyzoa cxli + 601 pp, atlas, 83 Pls. London.
Levinsen, G. M. R. 1909. Morphological and Systematic Studies on the Cheilostomatous Bryozoa. vii + 431 pp., 24 Pls. Copenhagen.
Maplestone, C. M. 1902. Further Descriptions of the Tertiary Polyzoa of Victoria, VII. Proc Roy. Soc. Victoria (n.s.) 14, pp. 65–74, Pls. 6–8.
Stach, L. W. 1937. The Species of Chiastosella (Bryozoa). Australian Zool. Sydney 8, pp. 334–340, Pl. 18.