Bryopesanser tonsillorum, Tilbrook, Kevin J., 2012

Tilbrook, Kevin J., 2012, Review of the bryozoan genus Bryopesanser Tilbrook, 2006 (Escharinidae: Cheilostomata) with the description of 11 new species, Zootaxa 3165, pp. 39-63 : 47-49

Bryopesanser tonsillorum n. sp.

( Figures 17–22 , Table 1)

Mastigophora dutertrei var. pes anseris: Thornely 1905 (part): 117. Mastigophora pesanseris: Canu & Bassler 1929 (part): 412. Mastigophora pes-anseris: Hastings 1930: 722.

Escharina pesanseris: Harmer1957 (part): 998, pl. 67, figs 12, 14. Escharina pesanseris: Cook, 1985: 165 , fig. 43.

Escharina pesanseris: Montoya-Cadavid et al. 2007: 170 .

Material. Holotype (here selected): NHMUK 2000.2.23.6, Siboga Stn 274, off Jedan Island, Indonesia, 5°28’2” S, 134°53’9” E, 26.12.1899, 57 m. Other material examined: NHMUK 2000.2.23.7, Siboga Stn 50, Badjo Bay, west coast of Flores, 16.04.1899, 0–40 m; NHMUK 2000.2.23.10, Siboga Stn 49a, Sapeh Strait, Sumbawa, 8°23’5” S, 119°04’06” E, 14.04.1899, 69 m; NHMUK 1929.4.26.191, Gorgona 3, Isla Gorgona, Colombia, 2°58’3” N, 78°10’49” W, dredge, 42.5 m (15 fms); NHMUK 1936.12.30.44, Sri Lanka, Thornely collection; NHMUK 1998.6.18.9, Sri Lanka, Thornely collection; NHMUK 1969.10.10.17–19 Ghana ( Gold Coast), Stn 131, Bassindale collection, 37 m; USNM 8222, Albatross Station 5235, Nagabut Island, off Magaboa Island, East Mindanoa, 9°43’ N, 125°48’15” E, 80 m (44 fms); USNM 8223, Albatross Station 5478, off Tacbuc Point, East Leyte, 10°46’24” N, 125°16’306” E, 104 m (57 fms).

Description. Autozooids 0.60–0.80 x 0.50–0.65 mm, hexagonal or irregularly polygonal, distinct, separated by shallow grooves. Frontal shield slightly nodular and convex, evenly perforated with numerous small multiporous pores, areolar septular pores laterally and proximally at each angle. Primary orifice as wide as long, ca 0.12 x 0.13 mm, excluding sinus, anter deeply arched, proximal border convex, condyles coarsely denticulate, dropshaped sinus longer than wide. Oral spines 7, evenly spaced. Proximal peristome widely flared, developed into a raised, median mucro with ontogeny. Avicularia originating lateral to most proximal pair of spines, rostrum medium-sized, with serrated edges, open-ended distally, crossbar complete, distally or distomedially directed, mandible fan-shaped. Ovicell hyperstomial, producing a thickened proximal edge, sometimes with a raised process frontally. Ovicellate zooids with 6 oral spines, the most distal pair incorporated into ovicell.

Etymology. Latin tonsilla, tonsil alluding to the shape of the oral condyles.

Remarks. Bryopesanser tonsillorum n. sp. is characterised by the details of the primary orifice, with its convex proximal border, coarsely denticulate condyles and longer-than-wide sinus, and the widely flared peristome often develops into a proximal mucro. The position of the avicularia (crossbar adjacent to most proximal oral spine) and their serrated edges are also characteristic.

Bryopesanser tonsillorum n. sp. differs from B. pesanseris in the shape of the oral condyles and in having multiporous frontal pores. Harmer (1957: Pl. 67, figs 12, 14) figured the holotype specimen (here selected), accurately showing the convex nature of the proximal oral border, yet noting that “the ‘Siboga’ specimens differ little from that figured by Smitt”. The multiporous frontal pores appear to develop late in ontogeny, but are also lost quite readily over time, leaving a frontal shield covered in large pores with jagged edges. The presence of multiporous frontal pores is not unique to B. tonsillorum n. sp. inasmuch as three other Bryopesanser species also develop them. However, this pore morphology in conjunction with attributes of the primary orifice, especially the morphology of the condyles, enables this group of species to be readily distinguished. B. tonsillorum n. sp. produces a flared peristome that sometimes develops a peristomial mucro similar to that in B. pesanseris , but the flaring is still visible. There is some within- and between-locality variation in the amount of sculpturing seen around the peristome of both species ― NHMUK 1998.6.18.9, Sri Lanka, has a sharply raised proximal umbo in ovicellate zooids and the ovicells themselves have an acute proximofrontal process; NHMUK 2000.2.23.10, Sumbawa, has very small versions of both processes in ovicellate zooids; both processes are lacking in NHMUK 1969.10.10.17–19, Gold Coast; NHMUK 1029.4.26.191, Colombia, has some ovicellate zooids with both processes whereas others have a process only on the ovicell itself.

Distribution. Bryopesanser tonsillorum n. sp. is widespread in its distribution, being found on the coast of Ghana, West Africa ( Cook 1968), Sri Lanka ( Thornely 1905), Indonesia ( Harmer 1957), Philippines ( Canu & Bassler 1929), and east to Isla Gorgona, off the Pacific coast of Colombia ( Hastings 1930).

Figures

FIGURES 17 – 22, Bryopesanser tonsillorum n. sp. 17 - 19. Holotype specimen, NHMUK 2000.2. 23.6, Indonesia; 20, NHMUK 1929.4. 26.191, Colombia; 21 - 22, NHMUK 1969.10. 10.17, Ghana. Scale bars: 17, 500 µm; 18, 100 µm; 19, 100 µm; 20, 50 µm; 21, 200 µm; 22, 50 µm.