Anoteropora latirostris Silén, 1947a

Martino, Emanuela Di, 2023, Scanning electron microscopy study of Lars Silén’s cheilostome bryozoan type specimens in the historical collections of natural history museums in Sweden, Zootaxa 5379 (1), pp. 1-106 : 88-91

Anoteropora latirostris Silén, 1947a

( Figs 48 , 49 ; Table 43)

Anoteropora latirostris Silén, 1947a: 58 , text-figs 49, 50, pl. 5, figs 25–27.

Material examined. Lectotype (designated here) SMNH-Type-8746a ( Fig. 48 ; specimen figured in Silén 1947a, pl. 5, fig. 25; the specimen was found fragmented in two parts) Indian Ocean , Bab-el-Mandeb, Aden Island; 12°26'N, 44°16'E; depth 37 m, gravel. Leg. Vega Expedition 1878–1880, Station 1186 . Paralectotypes SMNH-Type-8746b ( Fig. 49A, B ), SMNH-Type-8746c ( Fig. 49C, D ), SMNH-Type-8746d ( Fig. 49E, F ), and SMNH-Type-8746e (not figured), same details as lectotype.

Description. Colony discoidal, concave basally, convex frontally, formed by autozooids arranged in radial rows when starting from one of the six periancestrular autozooids, or in oblique, concentric, V-shaped rows when positioned within one of the sectors delimited by the radial rows ( Figs 48A, B, E , 49A, C ); ancestrula broken or altered in the specimens examined ( Fig. 49B, D ); largest fragment (now broken into two, Fig. 48A, B ) c. 1 cm long by 0.57–0.65 cm wide, circular colonies 2.3–3.5 mm in diameter. Basal side with visible boundaries between autozooids ( Fig. 49E, F ); basal surface ridged and granular with pits between ridges and pores (10–15 µm in diameter) at their centre; an elliptical distal pore chamber window visible on the peripheral zooids ( Fig. 49F ), 165–210 µm long by 50–80 µm wide.

Autozooids distinct, separated by thin furrows, seemingly quadrangular frontally but clearly hexagonal when observed from the basal side, almost equidimensional (mean L/ W 1.02).

Frontal area almost entirely occupied by the orifice ( Fig. 48C ), frontal shield reduced, imperforate except for 2–3 pairs of marginal areolae on each zooidal side, granular.

Orifice placed at the centre of the frontal shield, subcircular (mean OL/OW 0.97) with robust, rounded condyles placed at approximately orifice mid-length, 17–27 µm wide ( Fig. 48F ); orifice of ovicellate zooids more elliptical, wider than long ( Fig. 48C, D ).

Avicularium single, adventitious, lying horizontally, distally to each autozooid, including periancestrular zooids ( Fig. 49B, D ); rostrum spoon-shaped, directed laterally or slightly distolaterally, always in the same direction (counter clockwise) ( Fig. 48F ); central area of rostrum with wing-like constrictions raised in relation to the tip, crossbar complete; avicularia associated with ovicellate zooids oblique ( Fig. 48C, D ), when rostrum distolaterally directed, or vertical when rostrum distally directed. Mandible not observed.

Ovicell globular ( Fig. 48C, D ); ooecium surface granular, evenly and densely pseudoporous; pseudopores circular, 10–20 µm in diameter.

Remarks. Some inconsistencies in relation to depth and seafloor typology were detected between the information reported in Silén (1947a, p. 58) and the museum label accompanying the syntype specimens. The depth was reported as 30 m and the sea-bottom as muddy in Silén (1947a), while it is 37 m and gravel in the specimen label.

Organic parts were not preserved. The specimens were probably already dead when collected as Silén (1947a) suggested, and therefore characters such as rhizoids, opercula and mandibles were not observed. Hayward & Cook (1983) observed that colonies from off the eastern South African coast were attached to sand grains via numerous basal rhizoids, the pits and pores visible on the basal surface ( Fig. 49F ) corresponding to the attachment of the rhizoids ( Cook & Chimonides 1994). A mandibulate avicularium and orifices with opercula were figured in Jacob et al. (2019, fig. 1d): the mandible exceeds slightly the length of the rostrum and is curved and hooked at the tip; the operculum closes the ovicell.

Size measurements of the lectotype specimen are in agreement with those reported in Cook (1966) based on colonies from the Red Sea, the Gulf of Aden, the Gulf of Oman, Malacca, East and South Africa.

Figures

FIGURE 48. Anoteropora latirostris Silén, 1947a. Lectotype (designated here) SMNH-Type-8746a, Indian Ocean, Bab-el- Mandeb, Aden Island. A, B. General view of two fragments of the same colony figured in Silén (1947a, pl. 5, figs 25–27). C. Close-up of two zooids, one ovicellate, and associated interzooidal avicularia. D. Close-up of two zooids, one ovicellate, at the colony edge. E. General view of another colony fragment. F. Close-up of an autozooid showing the robust orifice condyles. Scale bars: A, B, E = 3 mm; C, D = 400 µm; F = 200 µm.

FIGURE 49. Anoteropora latirostris Silén, 1947a. Indian Ocean, Bab-el-Mandeb, Aden Island. A, B. Paralectotype SMNH- Type-8746b. C, D. Paralectotype SMNH-Type-8746c. E, F. Paralectotype SMNH-Type-8746d. A, C. General view of two young, subcircular colonies with ancestrulae. B, D. Close-up of the ancestrula and periancestrular zooids. E. View of the dorsal side of a colony fragment. F. Close-up of the dorsal side showing the large, distal pore chamber window and part of the ovicells at the colony growing edge. Scale bars: A, C, E = 1 mm; B, D = 500 µm; F = 400 µm.