Parasmittina ligulata, Martino & Rosso & Taylor & Chiu & Fujita & Kitamura & Yasuhara, 2025

Parasmittina ligulata sp. nov.

Di Martino, Rosso and Taylor

Figure 32 View FIGURE 32

zoobank.org/ FA9A9F18-2303-495A-A27B-85F929110C58

Type material. Holotype PMC. B59. 29.7.2024 a, sample 19178; Core 19, Daidokutsu cave, Okinawa, Japan, Holocene.

Etymology. Latin, meaning equipped with a ligula (i.e., the tongue-like skeletal projection on the pivotal bar), referring to the stout ligula of its avicularium.

Diagnosis. Parasmittina with autozooids separated by raised sutures; tubercular, flat to slightly sunken frontal shield with single row of conspicuous marginal areolae located between ridges; orifice partly concealed by an asymmetrical peristome, having a denticle projecting inwardly on one side and an avicularium on the other, forming a broad asymmetrical pseudosinus proximally; anvil-shaped lyrula with sharp tips curved proximally; five oral spine bases, none visible in ovicellate zooids; avicularium small, teardrop-shaped, proximally directed, located on a swollen cystid lateral to the orifice; crossbar with stout ligula; ooecium nodular with pseudopores, formed by the maternal zooid and one or two adjacent distal zooids.

Description. Colony encrusting, multiserial, unilaminar. Autozooids distinct, separated by raised sutures, longer than wide (mean ZL/ZW 1.43), rectangular to irregularly polygonal, quincuncially arranged. Frontal shield flat to slightly sunken, tubercular, imperforate except for a single row of 19–26, transversely elliptical to ovoid marginal areolar pores, 22–64 µm in maximum diameter, located between ridges, creating a costate appearance; additional smaller pores, about 10–15 µm in diameter, outlining proximally the avicularium cystid. Primary orifice partially concealed by an asymmetrical peristome, having a rounded triangular denticle projecting into the primary orifice on one side, an adventitious avicularium on the other, and a broad asymmetrical pseudosinus proximally; secondary orifice foot-shaped; lyrula anvil-shaped, 60–68 µm wide, with straight proximal margin sloping laterally into two pointed tips curved downward, often visible through the pseudosinus; acutely triangular condyles pointing medially, sometimes visible below the peristome; consistently five distal oral spine bases, 16–21 µm in diameter, none visible in ovicellate zooids. Avicularium adventitious, single or absent, located lateral to orifice on a swollen cystid, juxtaposed with the rim of the secondary orifice; rostrum rounded triangular, directed proximally; crossbar complete and equipped with a stout ligula, triangular to rectangular in shape, measuring 23–27 µm long by 18–27 µm wide, outlining a small semicircular opening distally, and a transversely C-shaped opening proximally. Ovicell hyperstomial, globular, formed by the maternal zooid and one or two adjacent distal zooids; ooecium striated, smooth (or tubercular when covered by variably developed secondary calcification), and pseudoporous; pseudopores circular, elliptical or drop-shaped roughly arranged in radial rows.

Measurements (µm). ZL 584±42, 483–639 (1, 15); ZW 410±47, 327–524 (1, 15); OL (secondary) 158±13, 140–183 (1, 7); OW 136±6, 127–143 (1, 7); AvL 83±12, 59–109 (1, 16); AvW 66±10, 46–80 (1, 16); OvL 292±22, 259–324 (1, 16); OvW 324±24, 296–369 (1, 16).

Remarks. We compared Parasmittina ligulata sp. nov. to all known North Pacific species of this genus and found that none had the same combination of characteristics. Among North Pacific species: P. acuta (Canu and Bassler, 1929) has avicularia placed adjacent to the proximal margin of the peristome; P. avicularissima Gontar, 1982 has a narrower lyrula, a large conical, nodular umbo, large frontal avicularia, and a single pore in the ooecium (see also Grischenko et al., 2007), P. contraria Seo, 1993 and P. pyriformis Seo, 2002 have only 1–2 spines and large, frontal, triangular avicularia distally directed; P. ragioidea Liu, 2001 in Liu et al. (2001) has 1–2 spines, two types of avicularia, triangular and spatulate (see also Taylor and Tan, 2015); P. spiculata Gluhak, Lewis and Popijak, 2007 lacks oral spines, and the avicularia are parallel-sided, long and slender; P. trispinosa granosa (Canu and Bassler, 1929) , P. trispinosa macroavicularia (Androsova, 1958) and P. trispinosa nanshaensis Lu, 1991 , all have 1–3 spines; P. winstonae Liu, 2001 in Liu et al. (2001) has 0–2 spines, serrated condyles, variably shaped avicularia, notably including giant avicularia directed distally, often extending over the frontal shield of the distal zooid (see also Taylor and Tan, 2015).

Among species from the Pliocene of Japan: P. chikagawaensis Hayami, 1975 is characterized by having 2–3 spines, and latero-oral and frontal avicularia distally directed; P. masudai Hayami, 1975 lacks spines and has prominent triangular avicularia directed distally, very large, occupying the entire frontal shield, sometimes covering one-quarter of the orifice and concealing its lyrula; P. shibikawaensis Hayami, 1975 seems to lack a lyrula and has a V-shaped peristomial sinus, with associated avicularia, two laterally, sometimes missing, and one proximally consistently present; P. okadai Hayami, 1975 has a prominent peristome forming a tube-like process with one to three associated avicularia, all directed distally.

Among species from the Pleistocene of Japan: P. aviculoumbonata Kataoka, 1961 has paired, umbonal avicularia lateral to the orifice and oriented in various directions, in addition to several rounded avicularia on the frontal shield, and two distal spines; P. peristoaviculata Kataoka, 1961 shows a well-developed peristome, thick and salient especially distally, and a long spatulate avicularium inside peristome; the peristome in P. plana Kataoka, 1961 forms a triangular pseudosinus and the frontal avicularia is placed nearly at the zooid axis pointing proximally.

Among Recent species described from or subsequently recorded in Japan, P. hanzawae Kataoka, 1960 has only two spines, a triangular pseudosinus, and median frontal avicularium, pointing obliquely distally; P. soulesi Scholz and Cusi, 1991 has 0–2 spines, elongate narrow avicularia, lyrula varying from minute to very large and conspicuous, and denticulate condyles (see Dick and Grischenko, 2017; note also that this species corresponds to P. lanceolata (Ortmann, 1890) in Hirose (2010)); P. triangularis (Mawatari, 1952) lacks spines and has four types of avicularia; P. trispinosa aomoriensis Kataoka, 1957 has two spines and slender obliquely directed avicularia.

Among Parasmittina species described and illustrated by Hirose (2010) from Sagami Bay, P. alanbanneri ( Soule and Soule, 1973) View in CoL has latero-oral avicularia with a narrow, elongate and serrated rostrum; P. areolata (Canu and Bassler, 1927) View in CoL has rounded, denticulate condyles and slender avicularia with denticulate rostrum; P. japonica (Ortmann, 1890) View in CoL has a strongly denticulate distal orifice margin, curved condyles that are also denticulate, and large frontal triangular avicularia pointing distally; the species reported as Parasmittina lateralis (Ortmann, 1890) n. comb. has a single spine and lateral, triangular avicularia almost as long as the entire length of the frontal shield; P. leviavicularia Soule and Soule, 1973 View in CoL has two spines and avicularia with raised, strongly serrated edges, directed distally; P. parsevaliformis Soule and Soule, 1973 View in CoL has 2–3 spines, a peristome that does not obstruct the orifice, narrow lyrula, and spatulate avicularia; P. projecta (Okada and Mawatari, 1937) View in CoL is distinguished by its forward-projecting peristome, forming a narrow U-shaped sinus, three spines, large triangular avicularia with serrated edges that extend distally over the edge of the peristome, and ovicells opening on the peristome; P. serrula Soule and Soule, 1973 View in CoL is distinguished by its larger rounded triangular avicularia and denticulate distal margin of the orifice; Parasmittina View in CoL sp. nov. 1 has an erect colony form, in addition to a denticulate orificial margin, and large triangular avicularia distally directed; Parasmittina View in CoL sp. nov. 2 has large, spatulate, triangular avicularia with serrated margins; Parasmittina View in CoL sp. nov. 3 and Parasmittina View in CoL sp. nov. 4 also have a denticulate orifice margin, and avicularia that are parallel-sided and slender in the former species, but spatulate in the latter species.