Eschara sulcata (Milne Edwards, 1836)

D’Hondt, J. - L., 2006, The Henri Milne EDWARDS’ (1800 - 1885) collection of recent and fossil bryozoa, Linzer biologische Beiträge 38 (1), pp. 25-38 : 32-33

2. Eschara sulcata : Adeonella sulcata (MILNE- EDWARDS 1836a)

The zoarium est foliaceous, constituted by wide erect dichotomic and bistratified lobes. The autozooids are regularly lozenge-shaped, 0,44-0,60 mm in length and 0,28-0,30 mm wide. The zoecial outlines form rather salient rims. The aperture is 0,080 -0,085 mm in length (exceptionaly a little shorter) and 0,90-0,95 mm wide; it is hemicircular with a proximal edge almost rectilinear, or almost circular. Normally 3 aviculairia are present on each zooid. The first is lateral to the aperture, 0,08-0,10 mm long, narrow and sharppointed at the extremity, oriented forewards (very rarely backwards); it can be in some very exceptional cases larger (0,14 mm). The second is immediately preapertural (or, by exception, completely proximal), perpendicular to the longitudinal axis (hence parallel to the proximal side of the aperture), with a same shape as the previous and 0,08-0,09 mm in length. The third is axial, oriented forewards, 0,17-0,18 mm long, angular, with a base 0,09-0,18 mm wide. Immediately proximal to the previous, at the bottom of a hole in the middle of the frontal surface, a minute circular spiramen is present, 0,045 -0,050 mm in diameter, often obtured and virtual. No ovicell. The zooids in reproduction are much more voluminous and inflated, normally reunited (in groups of 2-5) in given areas scattered in the zoarium, 0,90 mm in length and 0,50 mm in width, with a wide and narrow transversal aperture in shape of crescent and an axial avicularium 0,16 mm in length localized in a groove delimited by tho symmetrical bulgings of the frontal face. Vicarious avicularian zooids, in lozenge-shaped like the autozooids, but much more voluminous, measuring 0,70-0,80 mm in length and 0,30-0,36 mm in width, often arranged in groups of 2 or 3, are also scattered in the zoarium; each of them carries a sharp-pointed avicularium, orientated distally, triangular in shape, measuring 0,40-0,45 mm in length and 0,20-0,24 mm in width at its base.

The species, arising from " Australie ", was very badly illustrated by EDWARDS (1836); he has not observed the transversal avicularium and has increased on his drawing the number of the zooids devoid of axial avicularia (in fact, their apparent lack depends of the state of abrasion according to the regions of the specimen). The original label joined to the material is more explicit: " de Port Western, mm. Quoy et Gaimard 1829 ". The same species has been further described and illustred by MCGILLIVRAY (cf. 1879-1890, pl. 48, figs. 6-7), apparently ignorant of the EDWARDS’ works, under the name of Lepralia mucronata ( MCGILLIVRAY 1868), a binomen he modified later as Eschara mucronata, a junior synonym of Adeonella sulcata (EDWARDS 1836) . MCGILLIVRAY correctly noted the vicariant large avicularium, but he seems not have distinguished the two small and typical apertural avicularia. A long list of the synonymies of Eschara mucronata has been further published by JELLY (1889); she refers particularly to some REUSS’ publications, but incorrectly and curiously regards E. sulcata EDWARDS 1836 as a junior synonym of a species described about thirty years before (1867), Microporella coscinophora REUSS 1867, from the Austrian Middle-Miocene. The type-specimen of Henri Milne EDWARDS being now rediscovered, a direct comparison of both taxa would now be judicious to confirm or infirm this synonymy.

Adeonella sulcata does not correspond to any of the species described or redescribed later by COOK (1973 1982) from African coasts, by HAYWARD & COOK (1983) from South Africa, or in the general recapitulations of all the species of this genus published by HAYWARD (1983, 1988), in which this taxon is not mentioned, even under the specific name of mucronata.