Parasmittina acondylata Dick & Ngai & Doan 2020, n. sp.

Parasmittina acondylata n. sp.

(Fig. 9 A–C)

urn:lsid:zoobank.org:act: D3FE34D9-98B3-4883-9A6C-AC0C5B74281A

Etymology. The specific name is derived from the Greek prefix a- (without) and condyle, referring to the apparent lack of condyles.

Material examined. Holotype, VNMN-0236 (CT-32), on SEM stub. VNMN-0237, additional dried specimens.

Measurements. AzL, 0.35–0.56 (0.430 ± 0.063); AzW, 0.19–0.32 (0.267 ± 0.037); SecOrL, 0.088 –0.143 (0.119 ± 0.013); SecOrW, 0.077 –0.117 (0.103 ± 0.009); OvL, 0.13–0.17 (0.158 ±0.014); OvW, 0.19–0.23 (0.203 ± 0.014) (n = 15, 1). AvRL, 0.07–0.13 (0.103 ± 0.024); AvRW, 0.03–0.04 (0.034 ± 0.003) (n = 12, 1).

Diagnosis. Three oral spines. Orifice with lyrula moderately broad and tall, alate or non-alate; condyles lacking. Frontal shield coarsely pustulose; areolae conspicuous, circular. Single, rather small frontal avicularium per zooid, proximolateral to orifice (occasionally medial), abutting peristomial collar, directed proximally, rostrum elongate, narrow, rounded at both ends; no giant avicularia observed. Ooecium broader than long, smooth, with around 20 scattered pseudopores; peristomial rim continuous around proximal ooecial margin.

Description. Colony encrusting, unilaminar, sheet-like.

Zooids irregular; rectangular, barrel-shaped, or spindle-shaped; distinct, delineated by groove and marginal line flanked by opposing columns of areolae. Frontal wall highly convex, rising to raised peristomial collar surrounding orifice laterally and proximally; coarsely pustulose, with six to nine conspicuous areolae along each lateral margin, with short struts between adjacent areolae. Primary orifice submerged, appearing longer than broad, with median lyrula about one-third as wide as orifice; lyrula moderately long, tapering, weakly alate or truncate. Condyles appear lacking, or scarcely evident, possibly represented by slight, broad convexity on either side distolateral to lyrula. Secondary orifice pear-shaped in outline, with proximal median constriction forming weak or pronounced pseudosinus. Three oral spines.

Many but not all zooids with single frontal avicularium abutting peristomial collar, offset to one side of midline or other, occasionally in midline; rostrum elongate, parallel-sided, rounded at both ends, directed proximally; opesial opening oval, occupying nearly half of rostrum; no crossbars observed, but possibly lost.

Ooecium prominent, first forming as concavity in proximal frontal wall of next-distal zooid, later appearing to rest on frontal wall; broader than long; globose, somewhat flattened, smooth, with up to 25 small, scattered pseudopores. Sides of peristomial collar continue as raised lip around proximofrontal part of ooecium, forming secondary orifice; oocium ringed around lateral and distal margin with band of raised secondary calcification from next-distal zooid.

Remarks. This species was detected as a single small, worn colony. While it clearly belongs in Parasmittina, it is unusual in lacking well-defined condyles, which is one of the diagnostic features of the genus. If condyles are present at all, they are evident only as a slight convexity in each lateral margin of the primary orifice, and we are aware of no other Parasmittina species with this condition. The frontal avicularia are similar in shape, size, and position to those in P. soulesi Scholz & Cusi, 1991, which differs in having two oral spines; the orifice with a narrow, truncate lyrula and massive condyles, creating a deep sinus on each side of the lyrula; and the ooecia subimmersed, with a single row of large pseudopores around the distal margin.

Distribution. Co To Island is the only known locality.