Distansescharella cervicornis, Souto, Javier, Berning, Björn & Ostrovsky, Andrew N., 2016

Souto, Javier, Berning, Björn & Ostrovsky, Andrew N., 2016, Systematics and diversity of deep-water Cheilostomata (Bryozoa) from Galicia Bank (NE Atlantic), Zootaxa 4067 (4), pp. 401-459 : 421-423

Distansescharella cervicornis n. sp.

( Figs 46–51 , Table 10 )

? Distansescharella alcicornis : López-Fé 2006: 1807 , figs 7, 8.

Material examined. Holotype: MNCN 25.03/3941, locality DR02. Paratypes: MNCN 25.03/3942, locality DR02; MNCN 25.03/3943, locality DR01; OLL 2015/900, locality DR02; OLL 2015/901, Locality V01.

Etymology. The species name alludes to the antler-shaped oral spines.

Description. Colonies encrusting, unilaminar, multiserial, forming spots or small patches. Zooids broadly oval, separated by grooves; costate frontal shield flattened, made of 20–24 broad flattened costae with up to 5 intercostal spaces, these elongated towards base of costa, round to oval in central part, often closed if costae closely appressed; costal surface wrinkled owing to growth striations; distalmost pair always distinctly broader, distal projections usually absent, forming extremely broad and very short central denticle with straight distal margin if present; gymnocystal walls well developed, especially in proximal region. Orifice broadly transversely D-shaped, distinctly wider than long, distal margin with 4 thick, branching oral spines in ovicellate and non-ovicellate zooids, forming a kind of collar around orifice with slightly wider gap between bases of distal pair; spines obliquely positioned, reminiscent of deer antlers, with 4–5 cylindrical terminal projections.

Ovicells hyperstomial, cleithral. Bilobate ooecium produced by distal autozooid and positioned on its proximal gymnocyst; globular, usually as long as wide, with medial suture; ectooecium smooth, proximal margin incorporating bases of distal pair of oral spines.

SD, standard deviation; N, number of measurements

Avicularia interzooidal, small, normally with oval or pear-shaped cystid outline, but sometimes triangular or irregular, usually 2 per zooid, situated laterally to zooidal orifice, mandibles directed laterally to distally; lateral gymnocystal walls well developed; avicularian frontal area pyriform, framed by elevated rim, rostrum at acute angle to colony surface; postmandibular area forming 2/3 of full circle, being wider than semielliptical or semicircular palatal area that is separated from postmandibular area by small condyles on which mandible is hinged; cryptocystal shelf broadest proximally and narrowing distally, framing oval opening that united palatal foramen and postmandibular opesia. Kenozooids common, usually attaining slightly more than autozooid length and width, occasionally larger; frontal area flattened, almost entirely composed of smooth gymnocystal calcification apart from small round or elliptical central opesia that is encircled by narrow cryptocystal calcification and slightly elevated rim positioned more or less centrally. Basal pore-chambers present in all types of zooids.

Only one tatiform ancestrula was found, partially overgrown, and presumably with 8–9 relatively thin, jointed branching spines.

Remarks. This species is very similar to Distansescharella alcicornis but there are a sufficient number of differences that allow us to recognize it as a distinct species. The number of frontal costae always exceeds 20 in D. cervicornis n. sp., whereas D. alcicornis has 16–19 costae. Oral spines in the latter species have cylindrical, not flattened tines, and the ratio of orifice width to length is 1.48 in D. alcicornis in contrast to 2 in D. cervicornis n. sp. These differences are constant at all localities. Although ancestrulae were lacking from our specimens of D. alcicornis, Harmelin et al. (1989) described the ancestrula as tatiform with up to 17 spines. In contrast, there are only nine spines in the ancestrula of D. cervicornis n. sp.

A variety of Jullien's species, Distansescharella alcicornis var. bifurcata (d'Hondt, 1974) , was described based on a single specimen that differs in the morphology of the spines, which are bifurcated. The type specimen of this variety (MNHN 6983) is a small colony formed by four zooids that are not very well preserved. The number of frontal costae in these zooids is 16 or 17, thus similar to D. alcicornis , whereas the only spine present (while broken) is apparently bifurcate. It is impossible to comment further on the status of this taxon until new material has been obtained.

The specimens described by López-Fé (2006) and identified as D. alcicornis are very similar to D. cervicornis n. sp. The zooids have a large number of frontal costae (up to 24) as well as oral spines with cylindrical, not flattened tines. It is possible that these specimens from bathyal waters of the Canary Islands (1686–2200 m depth) correspond to D. cervicornis n. sp. but it is difficult to come to a conclusion based on the single image provided, particularly considering the geographic distance between these two deep-water populations.

At Galicia Bank, D. cervicornis n. sp. was found at six localities, growing on dead corals and rocks between 770 and 1697 m depth.

Figures

FIGURES 46 – 51. Distansescharella cervicornis n. sp.: 46, 47, general view of colonies (MNCN 25.03 / 3943, 3941); 48, area of autozooidal orifice and avicularium (OLL 2015 / 900); 49, autozooids with oral spines (OLL 2015 / 900); 50, 51, part of colony with ovicellate zooid and kenozooids (MNCN 25.03 / 3943, 3941).

Tables

TABLE 10. Measurements (in mm) of Distansescharella cervicornis n. sp.

	Mean	SD	Minimum	Maximum	N
Autozooid length	0.452	0.0428	0.376	0.542	40
Autozooid width	0.334	0.0298	0.278	0.382	40
Orifice length	0.065	0.0082	0.050	0.078	21
Orifice width	0.131	0.0122	0.107	0.159	21
Ooecium length	0.169	0.0160	0.131	0.201	12
Ooecium width	0.168	0.0109	0.141	0.183	12
Avicularium cystid length	0.110	0.0115	0.085	0.138	46
Avicularium cystid width	0.099	0.0145	0.072	0.135	46
Avicularium length	0.068	0.0060	0.057	0.082	46
Avicularium width	0.048	0.0053	0.037	0.061	46