Introduction

The scorpionfish genus Parascorpaena Bleeker 1876, features palatine teeth, erect spines on the head and suborbital region, an occipital depression, a scaly thoracic and preventral region, as observed in the type species Scorpaena picta Cuvier in Cuvier and Valenciennes 1829. Bleeker (1876) also reclassified Scorpaena bandanensis Bleeker 1851 to Parascorpaena. Subsequently, Herre (1952) provided additional characteristics of Parascorpaena, including: oblong, compressed body; cutaneous filaments and appendages sometimes present on head and body; villiform teeth on both jaws, vomer and palatines; either ctenoid or cycloid scales; 36–60 scale rows in longitudinal series; scales absent on dorsal and anal fins; head naked (except behind eyes and on upper half of opercle), with spiny crests above; spines on preorbital; 2 opercular spines; 3–5 preopercular spines; dorsum of head more or less deeply grooved; 8–11 dorsal-fin soft rays; 3 anal-fin spines with 5 or 6 soft rays; branched dorsal-, anal-, and caudal-fin rays; non-elongated pectoral rays, upper rays branched or all rays unbranched, no free rays; and 7 branchiostegals. Smith (1957) further refined the definition of Parascorpaena based on a combination of characters, including: absence of chin barbels; fewer than 20 pectoral-fin rays; an anteriorly hooked lower hind preorbital spine; cycloid scales at most feebly crenulate; lateral line extending to caudal-fin base; 12 dorsal-fin spines connected by membrane; teeth absent on vomer but present on palatines; and fewer than 14 (total) gill rakers on lower part of outer gill arch. Based on these distinctive features, he then re-assigned Scorpaena aurita Rüppell 1838 to Parascorpaena and described a new species, namely Parascorpaena maculipinnis Smith 1957. Later, Dor (1984) re-assigned Scorpaena mossambica Peters 1855 to Parascorpaena without explanation.

Eschmeyer’s (1986) concept of Parascorpaena, to which he re-assigned Scorpaena mcadamsi Fowler 1938, included new characters plus a combination of some described by Bleeker (1876), Herre (1952), and Smith (1957), including a moderately compressed body, well-developed head spines, lacrimal with 2 spines over maxilla, the long posterior spine outwardly curved and anteriorly hooked (less so in young), 8–10 dorsal-fin soft rays, 14–18 pectoral-fin rays, and 35–45 scale rows in longitudinal series. Following that generic diagnosis, Motomura et al. (2011a) confirmed the taxonomic validity of Parascorpaena armata (Sauvage 1873) and Parascorpaena moultoni (Whitley 1961), clarifying the distribution range of P. armata in the Pacific Ocean, and restricting P. mossambica solely to the Indian Ocean. Furthermore, Motomura et al. (2011a) distinguished P. moultoni from P. mcadamsi, previously thought to be synonymous, based on the number of suborbital spines: two in P. moultoni, three in P. mcadamsi. The most recent addition to Parascorpaena is Parascorpaena poseidon Chou and Liao 2022, described from collections in Taiwan, resulting in a total of nine valid species of the genus Parascorpaena to date.

Although Mandrytsa (2001) categorized Parascorpaena as a subgenus of Scorpaena Linnaeus 1758, subsequent research recognized Parascorpaena as a distinct genus (Fricke 2005; Motomura et al. 2005, 2011a, 2015; Motomura 2009; Allen and Erdmann 2012; Larson et al. 2013; Delrien-Trottin et al. 2015; Mohapatra et al. 2015; Fricke et al. 2015, 2018; Koeda et al. 2016; Nelson et al. 2016; Golani and Fricke 2018; Kwik and Lim 2020; Emel’yanova and Pavlov 2021; Wibowo and Motomura 2021; Chou and Liao 2022; Poss and Motomura 2022; Mochizuki et al. 2023; Mochizuki and Motomura 2024). While the relationship of the genus Parascorpaena to other genera in the overall family Scorpaenidae has been explored (Ishida 1994; Lautredou et al. 2013), monophyly of the former has at no time been demonstrated.

Currently, the genus Parascorpaena is distinguished from other related genera by having two lacrimal spines on the ventral margin, with the posterior lacrimal spine (PLS) oriented anteriorly, and cycloid scales (Smith 1957; Eschmeyer 1986; Poss 1999; Motomura et al. 2005, 2009; Poss and Motomura 2022). However, P. bandanensis has ctenoid scales and a postero-ventral PLS (Bleeker 1851; Herre 1952; de Beaufort and Briggs 1962; Allen and Erdmann 2012; this study). Additionally, anterior orientation of the PLS is a defining trait in Parascorpaena, yet it may not be evident in smaller specimens, often resulting in misplacement within Scorpaena or Sebastapistes Gill in Streets 1877. Such inconsistency in these diagnostic traits has necessitated a review of the key generic characters. Consequently, the definition of Parascorpaena has been modified to include the morphological features of all species herein considered valid. In addition, the monophyly were confirmed on the basis of molecular evidence.

Materials and methods

Standard length (SL) was measured to the nearest 0.1 mm with digital calipers. Head spine terminology follows Motomura et al. (2009) and Wibowo and Motomura (2021). Institutional codes follow Sabaj (2020). Curatorial procedures for KAUM specimens followed Motomura and Ishihara (2013).

DNA extractions were carried out using preserved muscle tissue subsamples in 99.5% ethanol, following the manufacturer’s protocols specified for the Wizard Genomic DNA Purification Kit (Promega Inc.). Polymerase chain reaction (PCR) amplifications were performed for the three different gene markers: two mitochondrial gene markers—cytochrome oxidase subunit I (COI), 16S ribosomal ribonucleic acid (16S rRNA), and a nuclear DNA locus of the recombination activating gene 1 (RAG1). The primers used in this study were based on Ward et al. (2005) and Ivanova et al. (2007) for COI, Palumbi et al. (1991) for 16S rRNA, and López et al. (2004) and Chen et al. (2007) for RAG1, as listed in Electronic Supplementary Material Table S1 (ESM Table S1).

The thermocycler conditions for the amplification of the three gene markers were as follows: for the COI gene marker, pre-denaturation at 94°C for 30 seconds (s), 30 cycles of denaturation at 94°C for 30 s, annealing at 48°C for 30 s, extension at 72°C for 30 s, and a final extension step at 65°C for 10 minutes (mins); 16S rRNA amplification followed a similar pattern with pre-denaturation at 94°C for 3 mins, 30 cycles of denaturation at 94°C for 45 s, annealing at 50°C for 45 s, extension at 72°C for 2.5 mins, and final extension at 72°C for 5 mins; for RAG1, 30 cycles of denaturation at 94°C for 35 s, annealing at 56°C for 30 s, and an extension at 72°C for 1 min 15 s. The PCR products were purified using Sephadex G-50 Fine (Cytiva). Subsequently, automated sequencing was performed bidirectionally, using the BigDye Terminator v3.1 Cycle Sequencing Kit (Applied Biosystems), and was analyzed on a model 3730xl DNA Analyzer (Applied Biosystems). The sequences obtained from 18 species were aligned using Clustal X (Thompson et al. 1994) and deposited in GenBank. The corresponding accession numbers are provided in Table 1, with the exception of the sequences pertaining to P. mossambica complex. MEGA X software (Kumar et al. 2018) was employed for optimal evolutionary modeling (Nei and Kumar 2000) and subsequent analyses, including generating a maximum likelihood tree using the Kimura 2-parameter model (Kimura 1980) with 1,000 bootstrap replications (Felsenstein 1985).

Table 1 Sequences used for the study
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Comparative material: Caracanthus maculatus (Gray 1831): KAUM–I. 169070, 22.8 mm SL, Nazumado, Okago, Hachijo-jima Island, Izu Islands, Tokyo, Japan, 33°08.42′N, 139°44.19′E, 5–20 m. Neochirus brachypterus (Cuvier in Cuvier and Valenciennes 1829): KAUM-I. 167316, 112.9 mm SL, east of Kozakiyama, Kasasa, Minami-satsuma, Kagoshima, Japan, 31°25.44′N, 130°10.25′E, 36 m. Parascorpaena aurita: KAUM–I. 7642, 109.8 mm SL, off Ginowan, Okinawa-jima Island, Okinawa, Japan, 26°15–20′N, 127°42–45′E, 10–15 m; KAUM–I. 7646, 118.0 mm SL, off Isyado, Nakagusuku, Nakagami, Okinawa-jima Island, Okinawa, Japan, 26°16′03″N, 127°48′30″E, 2.5 m; KAUM–I. 79238, 95.9 mm SL, Kasari Bay, Kasari, Amami-oshima Island, Amami Islands, Kagoshima, Japan, 28°30′N, 129°39′E, 17 m; KAUM–I. 122877, 41.6 mm SL, KAUM–I. 161814, 44.2 mm SL, off Bandokorobana National Park, Beppu, Ei, Minami-kyushu, Kagoshima, Japan, 31°14′50″N, 130°26′00″E, 0.3–0.6 m; ROM 74350 (1 of 4), 19.7 mm SL, Hon Chong (Chong Island), Nha Trang Bay, Vietnam, 12°16′27″N, 109°12′8″E. Parascorpaena mcadamsi: AMS I. 33746-087 (1 of 2), 21.0 mm SL, southeast side of Boot Reef, Coral Sea, 10°2′43″S, 144°41′52″E; KAUM–I. 115044, 43.7 mm SL, south of Kiriishi Port, Suwanose-jima Island, Tokara Islands, Kagoshima, Japan, 29°36′34″N, 129°42′50″E, 15–18 m. Parascorpaena mossambica complex: KAUM–I. 72115, 53.8 mm SL, off north of Sanekumisaki, Setouchi, Amami-oshima Island, Amami Islands, Kagoshima, Japan, 28°11′N, 129°11′E, 10–24 m; KAUM–I. 89146, 80.2 mm SL, tidepool east of Dafu Port, Xiaoliuqiu, Liuqiu, Taiwan, 22°20′14″N, 120°22′41″E, 0.3 m; KAUM–I. 153105, 62.3 mm SL, Okidomari Port, Okinoerabu-jima Island, Amami Islands, Kagoshima, Japan, 27°23′48″N, 128°33′13″E, 2–4 m. Parascorpaena moultoni: KAUM–I. 72114, 60.9 mm SL, north of Sanekumisaki, Setouchi, Amami-oshima Island, Amami Islands, Kagoshima, Japan, 28°11′43″N, 129°11′32″E, 10–24 m. Parascorpaena picta: KAUM–I. 20964, 121.4 mm SL, north end of Supply Bay, Townshead Island, Australia, 22°12.14′S, 150°28.32′E, 0–0.2 m. Scorpaena brevispina Motomura and Senou 2008: KPM-NI 16667, holotype, 116.1 mm SL, off Futo, Ito, east coast of Izu Peninsula, Shizuoka Prefecture, Japan, 34°52′N, 139°08′E, 45 m depth; KPM-NI 65197, 70.7 mm SL, Sagami Bay, Kanagawa Prefecture, Japan. Scorpaena jacksoniensis Steindachner 1866: KAUM–I. 35883, 111.7 mm SL, 100 m off Fairlight Beach, Sydney Harbour, NSW, Australia, 33°48′04″S, 151°16′29″E, 2–8 m. Scorpaena neglecta Temminck and Schlegel 1843: KAUM–I. 86597, 76. 3 mm SL, East China Sea, 31°24′43″N, 127°32′00″E, 128–129 m; KAUM–I. 157984, 241.6 mm SL, off Shima-kishi, Itoshima, Fukuoka, Japan, 33°34′N, 130°07′E. Scorpaena pepo Motomura et al. 2007: KAUM–I. 55849, 178.5 mm SL, between Tanega-shima and Yaku-shima Islands, Osumi Islands, Kagoshima, Japan, >100 m. Scorpaenopsis diabolus (Cuvier 1829): KAUM–I. 134822, 169.8 mm SL, Irie Beach, Nakasato, Kikai-jima Island, Amami Islands, Kagoshima, Japan, 28°21′07″N, 129°55′08″E, 0.1–1.0 m. Scorpaenopsis neglecta Heckel 1837: KAUM–I. 175622, 152.2 mm SL, Genkainada Sea, Fukuoka, Japan. Scorpaenopsis papuensis (Cuvier in Cuvier and Valenciennes 1829): KAUM–I. 160605, 52.9 mm SL, Isso, Yaku-shima Island, Osumi Islands, Kagoshima, Japan, 30°27′33″N, 130°28′43″E, 5–15 m. Scorpaenopsis vittapinna Randall and Eschmeyer 2002: KAUM–I. 176539, 37.9 mm SL, Doren, Setouchi, Kakeroma-jima Island, Amami Islands, Kagoshima, Japan, 28°06′45″N, 129°20′44″E, 3–15 m. Sebastapistes fowleri (Pietschmann 1934): KAUM–I. 58426, 31.6 mm SL, off Tomori, southwest coast of Yoron-jima Island, Amami Islands, Kagoshima, Japan, 27°01′N, 128°24′E, 12–28 m. Sebastapistes mauritiana (Cuvier in Cuvier and Valenciennes 1829): USNM 423398, 41.3 mm SL, Austral Islands, Tubuai, French Polynesia. Sebastapistes strongia (Cuvier in Cuvier and Valenciennes 1829): KAUM–I. 111242, 48.1 mm SL, off southeast Dongsha Island, Dongsha Atoll, Taiwan, 20°40′07″N, 116°46′01″E, 8–10 m; SMNS 10632, holotype of Scorpaena bandanensis (Fig. 1), 52.6 mm SL, Banda Neira, Banda Islands, Indonesia. Sebastapistes taeniophrys (Fowler 1943): USNM 99522, holotype of Scorpaena taeniophrys, 19.3 mm SL, Cammahala Bay, Luzon, Philippines. Sebastapistes tinkhami (Fowler 1946): KAUM–I. 57664, 28.8 mm SL, Kaitsuzaki, Setouchi, Amami Islands, Kagoshima, Japan, 28°06′34″N, 129°22′34″E, 2.0–18.0 m.

Fig. 1
figure 1

Holotype of Scorpaena bandanensis (SMNS 10632), 52.6 mm SL, Banda Islands, Indonesia

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The following abbreviations are used in this paper: ALS (anterior lacrimal spine), PLS (posterior lacrimal spine), ALR (anterior lacrimal ridge), PLR (posterior lacrimal ridge), ADLS (antero-dorsal lacrimal spine), LLS (lateral lacrimal spine), AALS (additional spine along anterior lacrimal spine), and SR (first suborbital ridge). Specimens depicted in Figs. 2, 3, 4 were stained using cyanine blue to enhance visualization of particular features.

Fig. 2
figure 2

Comparison of posterior lacrimal spine orientation (a, d, g) and scale type (b, e, h) in Parascorpaena (a–c KAUM–I. 79238, P. aurita), Scorpaena (d–f KAUM–I. 86597, Scorpaena neglecta) and Sebastapistes (g–i KAUM–I. 57664, Sebastapistes tinkhami)

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Fig. 3
figure 3

Size-dependent variations on the posterior lacrimal spine (PLS) in Parascorpaena, described as strongly hooked anteriorly (a–b), oriented ventrally with anterior curvature (c), and oriented postero-ventrally (d). a Parascorpaena aurita (KAUM–I. 7646), 118.0 mm SL; b P. picta (KAUM–I. 20964), 121.4 mm SL; c P. mcadamsi (AMS I. 33746-087), 21.0 mm SL); d P. aurita (ROM 74350), 19.7 mm SL. Scale bar: 1 mm

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Fig. 4
figure 4

Spines and ridges along the lacrimal bone of Parascorpaena aurita (a KAUM–I. 7642) and Scorpaena jacksoniensis (b KAUM–I. 35883). Abbreviations: ALR anterior lacrimal ridge, PLR posterior lacrimal ridge, ADLS antero-dorsal lacrimal spine, LLS lateral lacrimal spine, ALS anterior lacrimal spine, AALS additional spine along anterior lacrimal spine, PLS posterior lacrimal spine, SR first suborbital ridge

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Parascorpaena Bleeker 1876

Parascorpaena Bleeker 1876: 295 (type species: Scorpaena picta Cuvier 1829; type by original designation).


Revised diagnosis. A genus of the family Scorpaenidae, characterized by the following combination of characters: usually complete lateral line, pored lateral-line scales continuing onto caudal-fin base (incomplete, continuing forward caudal-peduncle area in small specimens of P. moultoni); usually two or three suborbital spines; body covered with cycloid scales; usually second to fifth or sixth pectoral-fin rays branched (unbranched in small specimens); lower jaw slightly shorter than upper jaw; villiform teeth on upper jaw, canine-like teeth absent; palatine teeth present; posterior lacrimal ridge present; anterior and posterior lacrimal spines simple, without additional spinous points, PLS oriented anteriorly (small specimens <20 mm SL with PLS oriented postero-ventrally).

Description. Body size ranging from small to moderately large, characterized by deep, moderately compressed morphology. Head moderate in size; head length usually less than half of SL. Snout fairly blunt; dorsal profile steep. Eyes large; diameter usually slightly longer than snout length. Mouth large; maxilla extending just below or slightly beyond posterior margin of eye; four prominent pairs of mandibular pores on dentary, first pore positioned just behind tip of lower jaw, second pore along anterior lacrimal spine, third pore along posterior lacrimal spine and fourth pore behind posterior lacrimal spine (before posterior end of maxilla). Teeth on upper jaw villiform; teeth on lower jaw varying among species, from entirely villiform to canine-like on frontal area (e.g., P. mcadamsi); teeth on palatines small, villiform, in bands; teeth on vomerine villiform, in V-shaped patch. Body entirely covered with cycloid scales (rarely with weak ctenii); body scales extending to dorsal- and anal-fin soft ray membranes in some species (e.g., P. aurita); head mostly naked, a few scales behind posterior margin of eye and along posterior end of operculum, just behind opercular spines; dentary smooth, naked.

Dorsal-fin spines usually 12 (rarely 13) connected to soft rays; fourth or fifth spine longest; sixth to 11th spine gradually decreasing in size; 12th spine elongated, followed by usually 9 (rarely 8 or 10) branched soft rays; second dorsal-fin soft ray usually longest; seventh to tenth dorsal spines bearing black blotch in males in some species (e.g., P. mcadamsi). Anal-fin spines three, second spine longest; usually five branched soft rays. Pectoral-fin rays varying among species, ranging from usually 15 or 16 to 17 or 18; first (uppermost) ray simple, unbranched; second to fifth or sixth ray branched; lower rays thickened, unbranched; tips of fins variable, either just reaching or not reaching anal-fin spine base. Pelvic-fin length variable, not or just reaching anal-fin spine base.

Head spination. Nasal spines positioned bilaterally on nasal ridge, extending slightly beyond its height. Preocular spine relatively thick with broad base, located anteriorly within orbital region. Interorbital ridge originating either from mid-eye, anterior mid-eye, or along preocular-spine base, extending beyond posterior eye margin; rear end of ridge variable, forming a broad or faint loop, or distinct loop absent. Occipital pit variable, ranging from relatively deep to shallow, or not distinct. Supraocular and postocular spines situated above orbital region, close to one another. Supraocular spines occasionally possessing tentacle of variable size, from small (smaller than eye diameter; e.g., P. mcadamsi) to long (longer than eye diameter; e.g., P. mossambica). Tympanic spines simple, just behind postocular spine, usually separated by distance greater than that between spines on parietal and nuchal. Parietal and nuchal spines simple, close to one another; parietal spine originating posterior to origin of pterotic spine; nuchal spine originating just behind parietal spine. Sphenotic spine just behind posterior margin of eye, varying intraspecifically – sometimes singular, commonly in unevenly-sized pairs, and rarely in triplicate or lump-like. Pterotic spine simple, attached to skin, situated just behind sphenotic spine. Upper and lower post-temporal spines well-developed, uneven in size; upper spine shorter than and positioned just above lower spine; lower spine situated between pterotic and supracleithral spines. Lacrimal bone dorsally with two distinct ridges; ALR located before anterior eye margin, longer than PLR, located just behind origin of first suborbital ridge (just below ventral eye margin). ALS and PLS along ventral region of lacrimal bone, ALS prominently antrorse with tip not extending beyond lower lip; PLS notably hooked anteriorly in larger specimens, ventrally orientated with forward curvature in smaller specimens, postero-ventrally orientated without forward curvature in specimens <20 mm SL. Suborbital ridges variable, comprising a single or two distinct ridges, including two or three suborbital spines. Preopercular spines five; first and second along posterior margin of maxilla, covered with thick skin, usually with small tentacles; third to fifth exposed, progressively longer, fifth longest with small anterior supplemental preopercular spine. Opercular spines just behind pre-opercular margin; upper opercular spine slightly longer than lower opercular spine. Supracleithral spine single, short; located between upper and lower post-temporal spines (but closer to latter). Cleithral spine simple, base covered with operculum; spinous point not extending beyond most posterior tip of operculum. Postorbital spine usually absent; if present, lump-like, lacking a spinous point. Median interorbital ridge, coronal spine, ridge on lateral surface of maxilla, antero-dorsal lacrimal spines, lateral lacrimal spine, and additional spines on anterior lacrimal spine and posterior lacrimal spine all absent.

Taxonomic status of Scorpaena bandanensis. Scorpaena bandanensis was originally described by Bleeker (1851) based on a single specimen collected from Banda Neira, Banda Islands, Indonesia. Weber (1913) noted the resemblance between Scorpaena bandanensis and smaller specimens of P. picta, suggesting that they might be hybrids due to the shared characteristic of undivided pectoral-fin rays. However, this study reveals that juveniles of Parascorpaena naturally exhibit undivided pectoral-fin rays, indicating that the hybrid hypothesis is incorrect. Fowler (1939) originally proposed the genus Oligoscorpaena, designating Scorpaena bandanensis as its type species. However, Fricke et al. (2024) has been synonymized Oligoscorpaena with the genus Sebastapistes, although they have regarded Scorpaena bandanensis as a valid species of Parascorpaena. Currently, Scorpaena bandanensis is recognized as Parascorpaena bandanensis (Herre 1952; de Beaufort and Briggs 1962; Randall and Lim 2000; Fricke 2005; Allen and Erdmann 2012; Fricke et al. 2015; Kwik and Lim 2020).

The genus Parascorpaena is widely recognized for the combination of cycloid scales and anteriorly hooked PLS (Eschmeyer 1986; Poss 1999; Motomura et al. 2005, 2009; Poss and Motomura 2022), with the exception of P. bandanensis, which possess ctenoid scales (de Beaufort and Briggs 1962; Allen and Erdmann 2012). However, examination of the holotype of P. bandanensis (Fig. 1), measuring 52.6 mm SL, revealed that the PLS was oriented postero-ventrally. In fact, the overall description, based on scale type and PLS orientation, aligns P. bandanensis more closely with the genus Sebastapistes than with its presumed congeners. Furthermore, the holotype lacked an occipital pit and coronal spines, and had only two simple spines along the ventral margin of the lacrimal (ALS anteriorly oriented and PLS postero-ventrally oriented), 15 pectoral-fin rays, and three suborbital spines, which aligned P. bandanensis more closely with the characteristics of Sebastapistes strongia. Distinguishing characters, such as the presence of ctenoid scales, two simple spines on the ventral margin of the lacrimal, a posteroventrally oriented posterior lacrimal spine, usually 15 pectoral rays, two or three suborbital spines, and lack of an occipital pit, are consistent with the diagnosis of Sebastapistes strongia given by Poss (1999), Motomura (2009), Allen and Erdmann (2012), Motomura et al. (2011a, 2014), and Poss and Motomura (2022). Consequently, the present study concluded unequivocally that cycloid scales were a characteristic of all species of Parascorpaena, and that P. bandanensis should be treated as a junior synonym of Sebastapistes strongia.

Remarks. The review across all valid species of morphological traits that traditionally distinguished Parascorpaena from other genera has led to a refined definition of the former, based upon morphology. Descriptions of certain morphological characters and head spines, shared by all species, unless specifically stated as restricted to a particular species, are also included here.

Chou and Liao (2022) provided a detailed description of the suborbital spines of P. poseidon, noting the absence of a suborbital ridge. However, their figure 2, which illustrated preserved specimens, shows a distinct ridge evident along the first suborbital spine. It is therefore suggested that P. poseidon may exhibit distinct suborbital ridges, contrary to the description of Chou and Liao (2022). This characteristic has been corroborated in a subsequent redescription of P. poseidon, which delineated two distinct suborbital ridges (Mochizuki and Motomura 2024).

Although, some specimens of Parascorpaena have 13 dorsal spines, that number is considered an abnormality due to its rarity, a characteristic shared with Hoplosebastes Schmidt 1929, Scorpaenodes Bleeker 1857, and Thysanichthys Jordan and Starks 1904 (Jordan and Starks 1904; Eschmeyer 1969; Ishida 1994; Poss 1999; Nakabo 2002; Poss and Motomura 2022; Roy et al. 2022). However, Parascorpaena is easily distinguishable from the other three genera, based on scale type, cycloid scales covering the former compared with ctenoid scales in the others (Jordan and Starks 1904; Eschmeyer 1969; Poss and Motomura 2022; Roy et al. 2022). Additionally, all species of Parascorpaena have palatine teeth, which are absent in Hoplosebastes and Scorpaenodes (Eschmeyer 1969; Ishida 1994; Poss 1999; Poss and Motomura 2022; Roy et al. 2022).

Most species within the genera Parascorpaena (excluding P. maculipinnis and P. poseidon) and Sebastapistes (excluding Sebastapistes coniorta Jenkins 1903, Sebastapistes galactacma Jenkins 1903, and Sebastapistes perplexa Motomura Motomura, Aizawa and Endo 2014) were originally classified under the genus Scorpaena. Shared similarities of the three genera include 12 dorsal spines (rarely 13), three anal spines, some pectoral-fin rays branched, palatine teeth present, and some meristic counts overlapping, including pectoral-fin rays (15–18 in Parascorpaena vs. 13–21 in Scorpaena vs. 14–16 in Sebastapistes), and pored lateral-line scales (16–25 vs. 21–30 vs. 11–27) (Poss 1999; Wibowo and Motomura 2021; Poss and Motomura 2022; Mochizuki et al. 2023). In a cladistic analysis by Ishida (1994), Parascorpaena and Scorpaena were defined in one clade by three derived characters, including absence of a swimbladder, 1 + 2 hypurals, and fused scapula and uppermost radial. However, no derived trait was found that separated the two genera from each other. Because Sebastapistes was not included in the comparison, the myological and osteological relationship within the three genera remained unclear.

The close morphological similarities between Scorpaena and Sebastapistes have been clarified by Wibowo and Motomura (2021), with particular focus on Indo-Pacific species. Following their findings, Scorpaena is distinguished from Sebastapistes by the consistent combined traits of an occipital pit and three suborbital spines (vs. either lacks an occipital pit with 1–3 suborbital spines or has an occipital pit with only two suborbital spines in the latter). Moreover, they characterized Sebastapistes by the absence of a lateral lacrimal spine, a condition shared with Parascorpaena. However, the presence of spinous point on the lateral region of the lacrimal bone in some specimens of Sebastapistes necessitates further examination of this characteristic across the genus.

Nevertheless, Parascorpaena, defined by the combination of cycloid scales and anteriorly oriented PLS (Fig. 2a–c), is distinguished from both Scorpaena (Fig. 2d–f) and Sebastapistes (Fig. 2g–i) which have ctenoid scales and the PLS oriented ventrally (Fig. 2d) or postero-ventrally (Fig. 2g). It should be noted that some specimens of Scorpaena also have a postero-ventrally oriented PLS (Wibowo and Motomura 2021), indicating that this condition is not exclusively limited to species of Sebastapistes (Poss and Motomura 2022).

The anterior orientation of the PLS is one of the defining characters of the genus Parascorpaena, although not apparent in juvenile specimens, as noted by Eschmeyer (1986), Poss (1999), and Poss and Motomura (2022). However, the ventral or postero-ventral orientation of the PLS in some specimens has frequently lead to misplacement of species under Scorpaena or Sebastapistes. Consequently, a PLS orientation-status character is established here, following comparisons across different sizes of specimens of Parascorpaena.

Larger specimens of Parascorpaena (e.g., 118.0 mm SL and 121.4 mm SL as shown in Fig. 3a and 3b, respectively) possess a strongly anteriorly hooked PLS, whereas smaller specimens tend to have a ventrally-oriented PLS, although anteriorly curved (Fig. 3c). The smallest specimen available to this study with anterior curvature was 21.0 mm SL. Specimens of 20.0 mm SL or less had the PLS oriented postero-ventrally, as shown in Fig. 3d, indicating that specimens >20 mm SL with a ventrally- or postero-ventrally-directed PLS should not be placed under Parascorpaena, but referred to either of the genera Scorpaena or Sebastapistes.

The anteriorly-oriented posterior lacrimal spine observed in Parascorpaena is similar to that of Scorpaena canariensis (Sauvage 1878). Nevertheless, species of Parascorpaena are distinguished by cycloid scales, contrasting with the ctenoid scales found in Scorpaena canariensis, as mentioned in Motomura et al. (2005). Additionally, the geographic distribution of these taxa differs, with the genus Parascorpaena is predominantly distributed within the Indo-Pacific region, while Scorpaena canariensis has been exclusively documented within the Atlantic region.

Although scale type can further separate species of Parascorpaena (cycloid scales) from species of Scorpaena and Sebastapistes (ctenoid scales), some species of the latter two genera have cycloid scales, including Scorpaena cardinalis Solander and Richardson in Richardson 1842, Scorpaena jacksoniensis, Scorpaena orgila Eschmeyer and Allen 1971, Sebastapistes pascuensis (Eschmeyer and Allen 1971), and Sebastapistes galactacma (see Richardson 1842; Steindachner 1866; Jenkins 1903; Eschmeyer and Allen 1971; Poss 1999; Motomura et al. 2011b; Wibowo and Motomura 2021). Such inconsistency in scale type may result in misidentification of juvenile specimens, particularly as the defining anterior orientation of PLS in Parascorpaena is not distinct in smaller specimens.

Scorpaena cardinalis, Scorpaena jacksoniensis, and Scorpaena orgila are most closely similar to P. aurita, sharing a combination of characters, such as a well-defined occipital pit, pectoral-fin rays usually 17 (16–18), palatine teeth, and cycloid scales (Richardson 1842; Steindachner 1866; Eschmeyer and Allen 1971; Poss 1999; Motomura et al. 2011b; Wibowo and Motomura 2021). However, all species of Parascorpaena can be easily distinguished from the above species by the absence of a lateral lacrimal spine (vs. lateral lacrimal with two spinous points) and absence of additional ALS and PLS spines (vs. additional ALS and PLS spines present in Scorpaena cardinalis; additional ALS spine present in Scorpaena jacksoniensis) (Motomura et al. 2011b; Wibowo and Motomura 2021). Spines and ridges along the lacrimal bone in P. aurita and Scorpaena jacksoniensis are shown in Fig. 4, which illustrates that the ALS and PLS of all species of Parascorpaena (Fig. 4a) are simple, lacking additional spinous points in contrast to Scorpaena jacksoniensis (Fig. 4b) (Motomura et al. 2011b; Wibowo and Motomura 2021). Moreover, Scorpaena jacksoniensis has both an antero-dorsal lacrimal and lateral lacrimal spine (Motomura et al. 2011b; Wibowo and Motomura 2021), both being absent in Parascorpaena, which instead has a posterior lacrimal ridge positioned behind the first suborbital ridge.

Among the valid species of Parascorpaena, Sebastapistes pascuensis closely resembles P. moultoni, sharing morphological features including cycloid scales, palatine teeth, a shallow occipital pit, two suborbital spines, dorsal-fin rays usually XII, 9, anal-fin rays usually III, 5, and pectoral-fin rays usually 15 or 16. Some specimens in both species exhibit black spots on the dorsal spines (in P. moultoni males only). However, Sebastapistes pascuensis is distinguished by a brown to black spot on the opercle (Eschmeyer and Allen 1971), such being absent in P. moultoni. Live coloration further separates the two species, with Sebastapistes pascuensis being brown to greenish-brown (Eschmeyer and Allen 1971) and P. moultoni rosy-red (Whitley 1961; Mochizuki et al. 2023). On the other hand, a combination of characters, including an undefined occipital pit, three suborbital spines,15 or 16 pectoral-fin rays, coronal spines absent, and black spots present posteriorly on the dorsal spines (in P. mcadamsi males only) suggest that Sebastapistes galactacma is closest to P. mcadamsi. However, the latter has canine-like teeth on the lower jaw in males (vs. villiform teeth in Sebastapistes galactacma) (Jenkins 1903; Poss and Motomura 2022; Mochizuki et al. 2023).

Monophyly. Monophyly of the genus Parascorpaena has at no time been investigated, and the sister taxon of the genus has remained uncertain. In this study, the molecular analysis focused on the four species of Parascorpaena, namely, P. aurita, P. mcadamsi, P. mossambica complex, and P. moultoni. Specimens within the P. mossambica complex are originally classified under P. mossambica; however, molecular analysis indicates that these specimens may actually represent three distinct species. Therefore, this study provisionally identifies these taxa as a complex, pending further confirmation. A dataset of 18 sequences was generated, including representatives from various genera such as Neochirus Chou et al. 2023, Scorpaena, Scorpaenopsis Heckel 1837, Sebastapistes, and Caracanthus Krøyer 1845 as the outgroup. Notably, the specimen initially identified as Dendrochirus brachypterus (Cuvier in Cuvier and Valenciennes 1829) has been reclassified under the proposed new genus Neochirus by Chou et al. (2023). The concatenated sequences utilized in the analysis comprised COI (471 bp), 16S rRNA (501 bp), and RAG1 (528 bp), resulting a total dataset length of 1,500 bp for each sequence. This molecular analysis provided a valuable insight into evolutionary history and taxonomic placement of Parascorpaena within the tribe Scorpaenini (sensu Nelson et al. 2016).

The phylogenetic tree (Fig. 5) constructed from the concatenated sequences revealed the genetic similarities within species of Parascorpaena, affirming the monophyletic nature of the genus. Bootstrap values on distinct clades emphasized the divergence of Parascorpaena from other genera. In addition, species representing Scorpaena and Scorpaenopsis were also found to be monophyletic. However, the paraphyletic nature of species representing Sebastapistes demonstrated a need for further study.

Fig. 5
figure 5

Maximum likelihood phylogenetic tree constructed using Kimura 2-parameter model from concatenated sequences of COI, 16S rRNA, and RAG1 markers, with Caracanthus maculatus serving as the outgroup. Node numbers indicate bootstrap support values

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Essentially, despite the morphological similarity of Parascorpaena with both Sebastapistes and Scorpaena, including number of fin spines, palatine teeth, and overlapping meristics (e.g., pectoral-fin rays), as noted above, the molecular evidence suggests a closer affinity between Parascorpaena and Sebastapistes mauritiana. This implies that species of Parascorpaena are more closely related to the Sebastapistes I group, represented by S. mauritiana [and probably Sebastapistes ballieui (Sauvage in Vaillant and Sauvage 1875), a sister species of S. mauritiana], than to Scorpaena and the Sebastapistes II group, represented by S. fowleri and S. strongia.

Although further taxonomic study is needed for the genus Sebastapistes, as implied by the above findings, comparisons on size and distribution depth among three closely related genera were also noted. Species of Parascorpaena and Scorpaena range from small to large, Poss (1999) noting that P. picta can grow to 170.0 mm SL (largest recorded size in the genus), whereas P. mcadamsi reaches a maximum length of only 80.0 mm SL. Species of Scorpaena distributed in the Indo-Pacific region range from 472.5 mm SL in Scorpaena cardinalis (see Wibowo and Motomura 2021) to the smallest species, Scorpaena sororreginae Wibowo and Motomura 2021, at 43.6 mm SL. On the other hand, Sebastapistes are usually small, the largest recorded being Sebastapistes ballieui at 85.9 mm SL (Motomura et al. 2014), with the apparently smallest, Sebastapistes taeniophrys being ca. 35.0 mm SL (Poss and Motomura 2022). Both Parascorpaena (approximately 0–45 m) and Sebastapistes (<50 m) are limited to shallower waters (Poss 1999; Poss and Motomura 2022), whereas species of Scorpaena can be found at various depths, ranging from 0 to 600 m (Wibowo and Motomura 2021).

Mandrytsa (2001) classified both Parascorpaena and Sebastapistes as subgenera of the genus Scorpaena. However, both morphological and molecular evidence presented in this study strongly suggested that both of the former should be recognized as distinct genera. Morphological variations, including scale type, coloration features, and spines along the lacrimal bone, are evident among Parascorpaena, Scorpaena, and Sebastapistes, and the differentiation between closely related species (e.g., between P. aurita and Scorpaena jacksoniensis, and P. moultoni and Sebastapistes pascuensis) further underscores the distinctiveness of the genera. This conclusion was substantiated by the molecular data, revealing that Parascorpaena and Sebastapistes (I and II) each form distinct clades, which are clearly divergent from the clade of Scorpaena, contradicting the classification proposed by Mandrytsa (2001).