Schizotheca aviculifera Canu and Bassler, 1925

Reverter-Gil, Oscar & Fernández-Pulpeiro, Eugenio, 2007, Species of genus Schizotheca Hincks (Bryozoa, Cheilostomata) described in the Atlantic-Mediterranean region, with notes on some species of Parasmittina Osburn, Journal of Natural History 41 (29 - 32), pp. 1929-1953 : 1947-1951

Schizotheca aviculifera Canu and Bassler, 1925

( Figures 6 , 7 )

Schizotheca aviculifera Canu and Bassler 1925, p 49 , Plate 3, Figures 6 –9; Canu and Bassler 1928, p 51. Schizotheca serratimargo (Hincks) : Canu and Bassler 1925, p 48 (part: material from Fedhala).

Material examined

Lectotype (designated here): MNHN-( Paléontologie ) -A-26411: Casablanca ( Morocco). Canu Coll.

Other material. MNHN-14748: Temara ( Morocco), 18 August 1951. MNHN-14754: as Schizotheca serratimargo, Temara , 4 April 1958, Morocco . MNHN-(Paléontologie): as Schizotheca serratimargo, Fedhala , Morocco.

Description

Colony encrusting, unilaminar. Autozooids oval to hexagonal, separated by clear sutures, indistinct in calcified zooids; frontal surface convex, smooth or slightly granular, perforated by up to 10 large conspicuous marginal pores.

Primary orifice immersed in calcified zooids; anter semielliptical, finely denticulated; poster straight, with two well-developed teeth defining an apparent wide, shallow sinus. Two oblique condyles, occasionally with slightly wavy distal edge, which does not reach the ends of the sinus. Peristome developed forming a fine, wide ring around the primary orifice, with a slight medio-proximal notch. Four spines at the edge of the colony, reduced to two in calcified or ovicellate zooids.

Each autozooid bears two small adventitious avicularia, situated on each side of the orifice; sometimes one or both avicularia may be lacking; mandible lanceolate, orientated distally and slightly upwards. Foramen basically triangular, but usually more or less narrow in the median zone; cross bar fine, generally without columella. Occasionally an avicularium may be associated distally with an ovicell, varying in its orientation.

Vicarious avicularia large, with a wide triangular mandible facing distally and upwards; orientation may be lost in very calcified colonies; foramen extensive, closed gradually from the distal end due to calcification, and Y-shaped. Cross bar with a large denticle. The vicarious avicularium is three times the size of the dependent avicularium.

Ovicell prominent, smooth and imperforate, deeply immersed in the distal zooid; proximal fissure wide, more or less elliptical.

Ancestrula not observed.

Measurements

MNHN. (Paléontologie) -A-26411 lectotype. AZL: 0.52¡0.03 (10); AZW: 0.36¡0.03 (10); OL: 0.12¡0.005 (5); OW: 0.11¡0.008 (5); VAL: 0.29 (1); VAW: 0.15 (1); AAL: 0.10¡0.02 (10); AAW: 0.06¡0.04 (10); VAL/AAL53 .

MNHN-14748. AZL: 0.51¡0.03 (20); AZW: 0.34¡0.03 (20); OL: 0.12¡0.01 (20); OW: 0.11¡0.008 (20); OVL: 0.21¡0.01 (10); OVW: 0.25¡0.01 (10); VAL: 0.39¡0.08 (10); VAW: 0.19¡0.03 (10); AAL: 0.12¡0.02 (30); AAW: 0.06¡0.01 (30); VAL/ AAL53.16.

Remarks

Schizotheca aviculifera is characterized by encrusting colonies consisting of zooids with a large number of very conspicuous marginal pores and often presenting a pair of disto-lateral avicularia, orientated distally. The vicarious avicularium is three times the size of the adventitious avicularium, of similar structure, but the former has a thick denticle in the cross bar.

This species was described by Canu and Bassler (1925) from a dead specimen collected in Casablanca ( Morocco) and from about 10 dead fragments from Mazagan (now El Jadida), to the south of Casablanca; the latter material is that originally figured ( Canu and Bassler 1925, Plate 3, Figures 6 –9). In a subsequent study ( Canu and Bassler 1928, p 51) these authors cited S. aviculifera from a dredge close to Casablanca (Vanneau, st. XIII, 9 July 1923, 100 m). From all of this original material, we have only been able to locate the dead colony from Casablanca, which is held in the Canu Collection deposited in the Laboratoire de Paléontologie of the MNHN, which has no registration number and was not labelled as the type specimen. The colony is very deteriorated and has many zoecial orifices filled with sand, making their examination difficult. The ovicells have been lost, with only the deep perforation in the distal zooid remaining. Only one large vicarious avicularium has been preserved. As this is the only original extant material, expressly cited by Canu and Bassler (1925, p 49), and as we have verified that it fits the description of the species, despite its poor state of conservation, we here designate the specimen as the lectotype of S. aviculifera .

We have been able to locate two colonies deposited in the MNHN (14754 and 14784) labelled as S. aviculifera and as S. serratimargo , but they do not correspond to the original material of Canu as indicated by the dates of collection (18 August 1951 and 4 April 1958); however, the material fits perfectly the description and the original figures of S. aviculifera , and furthermore originates from Temara, a beach situated 15 km to the south of Rabat and therefore relatively close to the original locations.

We have also located another colony from the Canu Collection deposited in the Laboratoire de Paléontologie, labelled as Schizotheca serratimargo , and originating from Fedhala (now Mohammedia), which is close to Casablanca. This material was cited by Canu and Bassler (1925, p 48). This encrusting colony consists of very calcified nodular zooids; the orifice of the zooids, difficult to observe as it is deeply immersed, totally coinciding with that typical of the species. The adventitious avicularia are very numerous, located on the margins of the zooids and orientated at random, with a narrowed foramen in the median zone, due to calcification, and adopting the shape of a figure ‘8’.

The colonies cited here constitute the only existing material that corresponds to S. aviculifera , as the species does not appear to have been cited since its original description.

Figures

Figure 6. Schizotheca aviculifera. (A) Group of zooids (MNHN-14754); (B) view in perspective, showing the position of adventitious avicularia (MNHN-14748); (C) two ovicellate zooids, one of them with three spines (right) (MNHN-14748); (D) two orifices, showing poorly developed proximal teeth, and condyles with wavy distal edge (MNHN-14754); (E) orifice with well-developed proximal teeth (MNHN-14748); (F) a vicarious avicularium, showing Y-shaped foramen (MNHN-14754).

Figure 7. Schizotheca aviculifera. (A–C) Casablanca, lectotype: (A) general view, showing orifices filled with sand; (B) orifice with well-developed proximal teeth; (C) orifice showing poorly developed proximal teeth. (D–F) Fedhala (as Schizotheca serratimargo): (D) general view, showing calcified zooids, and vicarious and adventitious avicularia; (E) orifice with well-developed proximal teeth; (F) orifice showing poorly developed proximal teeth.