Hippopleurifera barbosae, Ramalho, Laís V., Távora, Vladimir A., Tilbrook, Kevin J. & Zágoršek, Kamil, 2015

Ramalho, Laís V., Távora, Vladimir A., Tilbrook, Kevin J. & Zágoršek, Kamil, 2015, New species of Hippopleurifera (Bryozoa, Cheilostomata) from the Miocene Pirabas Formation, Pará state, Brazil, Zootaxa 3999 (1), pp. 125-134 : 128-130

Hippopleurifera barbosae sp. nov.

( Figs 2 A–F)

Material examined. Holotype: MG–6301–I–a, Atalaia Beach, Salinópolis, Pará state, Brazil. Paratypes: MG– 6301–I–b to n, same locality as holotype.

Diagnosis. Colony encrusting. Autozooids rectangular to polygonal; frontal shield with 1–4 rows of areolar pores. Orifice with 4 distal spines and a median lyrulate convexity, sometimes denticulate. A single suboral avicularium and a pair (usually) of lateral and asymmetrical avicularia. Oecium hyperstomial, with perforated entooecium and smooth bifenestrate ectooecium bearing two small avicularia.

Description. Colony encrusting. Autozooids rectangular to polygonal, longer than wide (633–1121 [800] µm x 468–633 [526] µm). Frontal shield with 1–4 rows of areolar pores, leaving the central region imperforate ( Fig. 2 A– C). Interior of frontal shield not well preserved, but 3–4 rows of areolar pores can be seen with small, smooth central area proximal to orifice ( Fig. 2 F).

Primary orifice slightly longer than wide (235–286 [255] µm x 235–262 [244] µm); anter evenly rounded, bordered by 4 spine bases, the distalmost pair closer to each other than the more proximal pair ( Fig. 2 C) [Laís, this is not easy to discern in 2C, but is seen in 2D.]; maternal zooids have only 2 spines visible ( Fig. 2 D); poster concave, with prominent median lyrulate convexity on proximal rim, sometimes weakly denticulate ( Fig. 2 B–D); a pair of short rounded-triangular condyles adjacent to proximalmost spines ( Fig. 2 C, D).

Single small suboral avicularium (100–176 [128] µm long), always on a raised cystid ( Fig. 2 A–D); rostrum triangular, directed distofrontally ( Fig. 2 C, D); crossbar complete; rostral tip often ending on the lyrulate convexity ( Fig. 2 B–D). Lateral avicularia often paired and asymmetrical in position, or simple, directed distally, parallel to or angled away from lateral border of orifice ( Fig. 2 A–D); variable in size (84–262 µm long) as well as shape ( Fig. 2 B, C); rostrum elongate-rounded, or sometimes spatulate; crossbar complete ( Fig. 2 A–C).

Ooecium hyperstomial, wider than long (233–407 [332] µm x 367–471 [425] µm), entooecium perforated by small pores, ectooecium smooth, thick, surrounding external border and frontal surface, forming a central keel, resulting in the ooecium appearing bifenestrate ( Fig. 2 E). Two small adventitious avicularia (96–144 µm long) often developed proximofrontally on ectooecium, asymmetrical, directed proximomedially, one situated on each side of the central keel ( Fig. 2 B, D–E); rostrum rounded ( Fig. 2 D, E), crossbar complete.

Etymology. Honorific for Dra. Maria Marta Barbosa who first studied the bryozoans from the Pirabas Formation.

Remarks. Some 25 species of Hippopleurifera have been described from around the world ( Bock 2012; Gordon 2014) (although the genus still needs to be reviewed; see comments above) but no Hippopleurifera species have yet been recorded from Brazil (fossil or Recent species). Most of the known species of Hippopleurifera are fossil, and most of these have six oral spines (although a few species may have up to seven), with lateral avicularia located near the proximal border of the orifice directed distally, but an umbo or suboral avicularium is not common. However, H. semicristata ( Reuss, 1847) has lateral avicularia similar in shape to those of H. barbosae sp. nov. but they are more proximally positioned and the number of oral spines is higher (five to seven). H. sedgwicki ( Milne Edwards, 1836) also resembles H. barbosae but this species has a significantly reduced, smooth area suborally on the frontal shield, only three to five oral spines, small oval, lateral avicularia and a bifenestrate ooecium. Finally, H. ampla ( Canu & Bassler, 1920) is the most similar to H. barbosae , mainly because of its possession of a suboral avicularium and bifenestrate oecium. However, the species are readily distinguished as H. ampla has a small elliptical, suboral avicularium, narrower zooids (220 µm), a smaller primary orifice (180 µm long x 200 µm wide) with a narrow cylindrical lyrula, only one or two rows of areolar pores and only a single lateral avicularium with a longer, more-spatulate rostrum. Canu & Bassler (1920) did not describe the ooecial surface of H. ampla , but neverthless illustrated an ooecium with what appears to be a pair of avicularia upon it ( Canu & Bassler 1920, fig. 15). Hippopleurifera barbosae sp. nov. is known only from the Pirabas Formation.

Figures

FIGURE 2. Hippopleurifera barbosae sp. nov. Specimens: A, MG – 6301 – I – a; B, MG – 6301 – I – b; C, MG – 6301 – I – d; D: MG – 6301 – I – c; E: MG – 6301 – I – e; F: MG – 6301 – I – f. A, general view of colony fragment showing primary orifices, some lateral and suboral avicularia and one ovicellate zooid. B, general view of colony fragment with ovicellate zooids showing their major characteristics. C, detail of two autozooids showing primary orifices with condyles, lyrulate processes and distal spines, as well as suboral and lateral avicularia and frontal shields with areolar pores. D, ovicellate and non-ovicellate zooids. E, detail of a perforated bifenestrate oecium with two frontal avicularia. F, frontal-shield interiors showing openings of areolar pores and reduced umbonuloid areas (best seen in zooid at upper left). Scale bars: A, B, D, F, 500 µm; C, 200 µm; E, 150 µm.