Rhabdopleura manubialis Jullien & Calvet, 1903

Gordon, Dennis P., Randolph Quek, Z. B. & Huang, Danwei, 2024, Four new species and a ribosomal phylogeny of Rhabdopleura (Hemichordata: Graptolithina) from New Zealand, with a review and key to all described extant taxa, Zootaxa 5424 (3), pp. 323-357 : 337

Rhabdopleura manubialis Jullien & Calvet, 1903 ( Figs 4G , 6E )

Type locality. Off the southeastern tip of Pico Island, Azores, 318 m [38.4000° N, 28.0239° W in Stebbing (1970a, p. 211), the original Paris meridian corrected to Greenwich], on dead bryozoans and a sertularian hydroid “en compagnie de Rhabdopleura Grimaldii. ”

Key features. Inception of ringed erect tubes is indirect. The species occurred at the same station as R. grimaldii , but the light-yellowish <3 cm-long colony lacked the ‘tubes très fins’ and had dormant buds (‘statoblasts’) in adherent parts of some blind-ending side branches. The dark pectocaulus is visibly continuous from the main creeping tube(s) into the side branches.

Comment. MNHN Paris sent two close-up images of this species based on the unique syntype (MNHN-IB-2014-387), which occurs on a fenestrate bryozoan, but the information content is very limited, again because creeping tubes are highly transparent and reflective; fusellar sutures were not clear enough in the images for zigzag angles to be measured. One erect ringed tube [ Fig. 6E ] was well imaged, however [784 m long, diameter 118‒131 (126) μm], with fusellus height 11‒24 (18) μm]. Creeping-tube width is 98‒110 (104) μm (n = 2), adherent-tube convexity width 177‒178 μm and creeping-tube stolon width is 20‒32 (26) μm (n = 3). Fusellar-collar extensions are greater than in R. grimaldii and there is no trace of a narrowing pectocaulus in side-branches. It is clear that the species is not synonymous with R. grimaldii .

The Latin epithet manubialis means ‘manual’ or ‘captured,’ with no obvious application to the description or illustration. If we assume that the sole illustration of the species was accurately rendered (as per camera lucida), zigzag angles are 57°‒81°, mean 72°, mode 70° (n = 34); the range of angles (57‒81°) just overlaps with that for R. normani [54‒61°, mean 57°, mode 55°] based on Allman’s (1869, pl. 8, fig. 4) illustration. Rhabdopleura manubialis has been treated as a junior synonym of R. normani but more work needs to be carried out on the latter species. External tube diameter between fusellar collars is 143‒154 (148) μm (n = 10) and fusellus height is 24‒41 (33) μm (n = 20), i.e. less than and almost completely non-overlapping with equivalent metrics for R. normani .

Figures

FIGURE 4. Original illustrations of described species of Rhabdopleura characterized by indirect inception of ringed erect tubes from creeping tubes via an intervening adnate portion that comprises a blind-ending branch. A, Rhabdopleura normani (from Allman 1869, pl. 8, fig. 1). Note that most of the colony is adherent; only the ringed tubes (rt) are erect, the proximal part of each side branch (ppsb) is adherent and the oblique sutures are not shown. B, schematic interpretative depiction of R. normani (after Andres 1977). C, D, Rhabdopleura grimaldii (from Jullien 1890, p. 181); note that ringed erect tubes (rt) are mostly lacking, with only the adherent proximal parts of side branches (ppsb) present. D is a cropped part of C to show the proximal parts of two side branches, with fusellar sutures and Jullien’s putative ‘very fine tubes’ (vft)—actually the side walls of the tapering pectocaulus, the proximal end of which is transparent, hence the apparent gap between it and the pectocaulus of the creeping tube. E, F, Rhabdopleura striata (from Schepotieff 1909, pl. 7, figs 2, 7); E shows longitudinally striated erect parts of side branches; oblique sutures on prostrate parts omitted in E but shown in F, with characteristic web of fusellar sutures (wfs) in branch angles from main creeping tube. G, Rhabdopleura manubialis (from Jullien & Calvet, 1903, pl. 1, fig. 2) with dormant bodies (db).

FIGURE 6. Rhabdopleura grimaldii Jullien, 1890 (A‒D, syntype MNHN-IB-2014-386) and R. manubialis Jullien & Calvet, 1903 (E, syntype MNHN-IB-2014-387). A, B, oblique views of two erect ringed tubes. C, adherent proximal part of a side branch (apsb), with a tapering pectocaulus (tp) (its side walls appearing as converging brown lines) and the broken base of an erect tube (bbet). D, similar to C, but also showing the creeping tube (ct) from which the broader side branch originated; note the faint outlines of oblique sutures on the creeping tube and side branch. E, erect ringed tube. Scale bars: A, B, 100 μm; C‒E, 200 μm. Images cropped from photos supplied by Pierre Lozuet, MNHN, Paris.