Schizomavella tubulata, Reverter-Gil & Souto & Novosel & Tilbrook, 2015

Reverter-Gil, Oscar, Souto, Javier, Novosel, Maja & Tilbrook, Kevin J., 2015, Adriatic species of Schizomavella (Bryozoa: Cheilostomata), Journal of Natural History 50, pp. 281-321 : 297-299

Schizomavella tubulata sp. nov.

( Figure 8 ; Table 6)

Type material

Holotype. CNHM Inv. br. 37: St. 16, Korčula Island (Sika), 42°94.973 N, 17°16.026 E, 24 April 2004, 30 – 40 m depth, one colony on a shell ( Figure 8 ).

Diagnosis

Primary orifice rounded, with distal and lateral edges forming a continuous curve; no proximolateral notches; surrounded laterally and proximally by a fine, raised peristome, containing the suboral avicularium; sinus small, U-shaped, occupying one third of the proximal border; condyles broad and thick; four or five stout, hollow, oral spines; avicularium almost perpendicular to frontal plane, enlarged and slightly spatulate; basal (distalmost) portion of the avicularium (opesia) covered by a raised, calcified opesial ‘ hood ’; ovicell globose, its distal half covered by a thick, imperforate cover of secondary calcification, and a crescent-shaped proximal area of exposed ectooecium perforated by several rounded pseudopores; ovicellate zooids with a tubular peristome, totally incorporating the avicularian cystid.

Etymology

Alluding to the tubular peristome developed in ovicellate zooids.

Description

Colony encrusting, unilaminar, developing as a small subcircular crust.

Autozooids oval or irregularly polygonal, separated by fine sutures, in linear series or losing orientation (perhaps evidence of partial overgrowth or the start of a multilaminar growth).

Frontal shield slightly nodular, convex, distally raised to form a small suboral prominence; perforated by 12 – 18 rounded pores, plus a row of elongated areolar pores; a smaller pore (occasionally two) on each side of the suboral avicularium.

Primary orifice rounded, slightly wider than long; distal and lateral edges forming a continuous curve; sinus small, U-shaped, occupying one third of the proximal border; condyles broad and thick, emphasising the sinus and reaching the corners of the orifice (i.e. there are no proximolateral notches).

Five (sometimes four) stout, hollow, oral spines, articulated, forming an arch around the distal half of the orifice.

The primary orifice is surrounded laterally and proximally by a fine, raised peristome, starting from the first pair of spines and containing the suboral avicularium. The avicularium is almost perpendicular to the frontal plane, enlarged and slightly spatulate, with finely denticulate rostrum; crossbar complete with a thick, triangular columella; basal (distalmost) portion of the avicularium (opesia) covered by a raised, calcified opesial ‘ hood ’; palatal foramen Y-shaped with granular inner edges.

Zooid lateral walls with small uniporous septula, placed in rows near the basal wall.

Ovicell acleithral, globose, prominent, its distal half covered by a thick, imperforate cover of secondary calcification; a crescent-shaped proximal area of exposed ectooecium perforated by several rounded pseudopores, the two in the proximal (outermost) corners clearly enlarged and elongate. Ovicellate zooids with a well-developed peristome, obscuring the primary orifice; the distal portion partially covering the ovicell, the proximal portion enclosing and incorporating the avicularium, forming a tall tube.

Ancestrula unknown.

Remarks

Shizomavella tubulata sp. nov. shows superficial similarities with S. halimedae and S. discoidea s. l. in the general shape of the primary orifice, in the number and shape of the oral spines, and in the development of a tubular peristome in ovicellate zooids; the ovicell morphology in S. tubulata sp. nov. is also very similar to that of S. halimedae . However, S. tubulata sp. nov. differs from both species due to its wider sinus, its larger condyles, the fine peristome in non-ovicellate zooids that encloses the median suboral avicularium (that is not as enlarged and spatulate as that in S. halimedae ) with its Y-shaped rostral foramen, and a calcified opesial ‘ hood ’. Finally, S. tubulata sp. nov. is characterised by the tall tubular peristome in ovicellate zooids which totally encloses the avicularium; in S. halimedae the peristome is interrupted proximally, in other words not enclosing the avicularium, while in S. discoidea s. l. it is interrupted distally, on the ovicell.

Schizomavella tubulata sp. nov. produces a fine peristome which includes the suboral avicularium, with a distal calcified opesial ‘ hood ’, as described in S. mystacea sp. nov. (see above), but this species differs from S. tubulata sp. nov. in, amongst other characters, its extremely short zooidal orifice.

Figures

Figure 8. Schizomavella tubulata sp. nov. (CNHM Inv. br. 37, holotype, St. 16, Korčula Island). (A) Part of the colony; (B) two autozooids showing the opercula, peristome, spines and suboral avicularia with serrated distal edge; (C, D) primary orifices without opercula; (E) suboral avicularium showing the calcified ‘hood’; (F) ovicellate zooids; (G) suboral avicularia within the tubular peristome of ovicellate zooids.

Tables

Table 6. Measurements (in mm) of Schizomavella tubulata sp. nov. (holotype).

	Mean	SD	Minimum	Maximum	N
Autozooid length	0.409	0.0607	0.321	0.491	10
Autozooid width	0.279	0.0360	0.211	0.328	10
Orifice length	0.072	0.0017	0.070	0.074	4
Orifice width	0.082	0.0024	0.079	0.085	4
Ovicell length	0.167	0.0151	0.156	0.184	3
Ovicell width	0.234	0.0104	0.222	0.242	3
Avicularium length	0.076	0.0082	0.065	0.085	5
Avicularium width	0.037	0.0030	0.033	0.041	5

Note: SD, standard deviation; N, number of measurements.