Type species.—Cylix tupareomanaia, new species.

Diagnosis.—A genus of the Syngnathidae that shares numerous morphological synapomorphies with Acentronura and Idiotropiscis, including head angled ventrally approximately 25° from the principal body axis, enclosed brood pouch, brood pouch plates, prehensile tail, and absence of caudal fin. However, Cylix tupareomanaia, new species, differs from all other genera by unique anatomical features of the head, including: a distinct, cup-like crest present anterodorsally on the supraoccipital; and large and conspicuous medioventral conical spines on the cleithral symphysis and the first trunk ring between the pectoral-fin bases. It differs further in having the following combination of morphological characters: prominent supraoccipital; continuous cleithrum; prominent supracleithrum; anterior nuchal plate absent; posterior nuchal plate present with bony dorsomedial crest; large gap present between the supraoccipital and posterior nuchal plate; one to three dorsal spines at midline of snout, posteriormost of these spines large; one large double and rugose lateral head spine present below the cup-like supraoccipital crest; three small blunt lateral head spines on operculum; rim of orbit elevated dorsolaterally and strongly ventrally; two spines on cleithral ring; large rugose spine anterior to ventral third of pectoral-fin base; moderate-sized spine at ventral extent of head; small spine present posterolateral to the pelvic-fin base; four subdorsal spines, forming a square, the dorsal two enlarged.

Etymology.—The generic name Cylix is derived from the Greek kylix, meaning cup or chalice, in reference to the cup-like crest present on the head. Gender masculine.

Hippocampus jugumus: Kuiter, 2009: 93, figs. A, B (Poor Knights Islands, New Zealand).

Acentronura australe: Stewart, 2015: 1053, fig. 148.1 (Bay of Islands, New Zealand).

Idiotropiscis aotearoa: Perkins, 2017 (Whangaruru, New Zealand;  http://www.inspiredtodive.com/photo-blog/introducing-idiotropiscis-aotearoa).

Holotype.—AIM MA122274, 31.4 mm SL, female, New Zealand, Waiatapaua Bay, Whangaruru, 35°19′18.7″S, 174°22′08.1″E, depth 14 m, hand collected via SCUBA on vertical rock wall covered in encrusting coralline algae, bryozoans, sponges, solitary corals, turf algae, with Ecklonia in adjacent area, C. Bedford, S. Hannam, I. Middleton, G. Short, and T. Trnski, 11 April 2017.

Paratypes.—NMNZ P.046322, 55.5 mm SL, male, New Zealand, Bay of Islands, east of Oturori Rock, 35°14′53.9″S, 174°09′35.1″E, depth 12–17 m, beam trawl, trip code kah0907, RV Kaharoa, shallow rocky reef and soft sediments with a mixture of Caulerpa, Ecklonia, and red and brown algae, M. Morrison, N. Bagley, NIWA, 3 September 2009; NMNZ P.056154, 35.5 mm SL, female, New Zealand, Cavalli Islands, Cavalli Passage, 35°00′50.4″S, 173°55′26.4″E, depth 12.6–14.5 m, beam trawl, mixture of brown algae, Ecklonia, Caulerpa, Lissonia, rhodoliths, and assorted red and brown algae, C. and I. Middleton, NIWA, 21 April 2014.

Diagnosis.—See generic diagnosis.

Description.—Morphometric and meristic characters of the three type specimens listed in Table 1. Trunk rings 13–14; tail rings 35–36; anal-fin rays 4; subdorsal rings 3 (spans one trunk ring and two tail rings); dorsal-fin rays 14; anal-fin rays 4; pectoral-fin rays 14. Body slender; head large relative to body, angled ventrally approximately 25° from the principal body axis, the dorsal profile pyramidal in lateral aspect, rising steeply from snout to elevated and prominent supraoccipital; distinct cup-like crest (SC) present anterodorsally on the supraoccipital well behind the eye, height moderate, pentamerous in dorsal view, divided transversally into two concave sections (Figs. 3, 4); cleithral and supracleithral ridge prominent (Fig. 4); posterior margins of pentamerous crest on supraoccipital fused and equal in height to cleithrum; anterior nuchal plate absent; posterior nuchal plate present with bony dorsomedial crest; large gap between the supraoccipital and posterior nuchal plate; gill openings small, bilateral; rim of orbit with prominent dorsolateral and ventral ridges, fluted with rugose sculpturing; opercular ridge low, entire, angled dorsally toward gill opening; swelling of gular region posteroventrally of eye, forming a transverse pair of blunt protuberances; pectoral-fin base without distinct ridges, one strongly elevated ventrolateral bulge (Fig. 4); dorsal-fin origin on 12^th trunk ring, fin base elevated; superior trunk ridge discontinuous with superior tail ridge below dorsal-fin base; lateral trunk ridge continuous with inferior tail ridge; inferior tail ridge ends on anal trunk ring; dorsum of anteriormost two trunk rings distinctly broader than posterior trunk rings; trunk in lateral view narrowest at 1^st and 2^nd trunk rings where angle of head forms from body axis, broadest at 5^th trunk ring; principal body ridges distinct and moderately elevated; tail rings of uniform depth over most of length, becoming progressively shorter and smaller near posterior tip; tail prehensile; scutella not evident.

Large spine present on dorsal midline of snout on the ethmoid area, at confluence with the anterior ends of supraorbital ridges, its height extended well above level of nares; none to two smaller medial spines anterior to the large spine on the snout, on the mesethmoid bone (principal dorsal spine and one anterior spine in paratype NMNZ P.056154, principal spine with anterior dorsal spines or elevations absent in paratype NMNZ P.046322); distinct median frontal spine at convergence of anterior edges of the cup-like supraoccipital crest, protruding anteriorly; four lateral head spines, one large double and rugose lateral head spine directly below the cup-like supraoccipital crest, three small blunt spines on operculum aligned 55–58° relative to the ventral axis of the head, the dorsal and ventral blunt spines connecting to terminal elements of the opercular ridge; large, conspicuous midventral conical spines on the cleithral symphysis and the first trunk ring between the pectoral-fin bases (Figs. 3, 5); two spines on cleithral ring, large rugose spine anterior to ventral third of pectoral-fin base, moderate-sized spine at ventral extent of head; small spine present posterolaterally of the pectoral-fin base (Figs. 3, 5); superior trunk ridges with spines of small to moderate size, enlarged blunt spines dorsally on 3^rd, 6^th, 10^th, 11^th, and 12^th rings, all bearing dermal flaps; lateral trunk ridges with moderate-sized spines on each trunk ring starting at 2^nd ring with enlarged spines on 3^rd, 6^th, and 10^th rings; inferior trunk ridges with moderate-sized spines starting at 3^rd ring with enlarged spines on 3^rd, 6^th, and 10^th rings; subdorsal spines four, superior trunk ridge ending with two subdorsal spines, the anteriormost spine large and conspicuous, superior tail ridge commencing with two subdorsal spines, posteriormost spine reduced, in alignment with larger subdorsal spines above; superior tail ridge spines well developed anteriorly, except on first and second ring, with enlarged spines on 3^rd, 4^th, 7^th, and 11^th tail ridges, gradually reducing in size to 22^nd trunk ring; lateral tail ridge spines absent; inferior tail ridge spines well developed to 8^th tail ring. Simple and branched dermal appendages present on head: long simple appendages extending anteriorly from dorsal rim of orbit, long and branched appendages ventrodorsally of each eye.

Cylix tupareomanaia exhibits strong sexual dimorphism with an enclosed brood pouch in male paratype NMNZ P.046322 (Fig. 2). The brood pouch is located along the ventral midline of the tail below the anteriormost ten tail rings. It is enclosed by ten arcuate bony extensions (Fig. 4) that extend ventrolaterally from the anterior ventral plate ridges of the tail, and progressively reduce in size posteriorly. The ten brood pouch plates are similar in appearance, whereas the posteriormost pouch plate is diminutive in size.

Coloration.—Holotype in life (Fig. 6A), head, trunk, and tail red; ventrolateral margin of trunk pale red to white; dorsum of head and snout speckled with fine white dots; pentamerous crest on supraoccipital red; snout spines, supraoccipital spine, anterior continuations of supraorbital ridges, and dorsal rim of orbit pale brown to white; white band extending from just behind the eye, grading posteriorly into a reticulated pattern of irregular, roundish quadrilaterals delineated by white coloration, concentrated on operculum and pectoral-fin base; reticulated pattern diffused laterally on head, pale brown to white; dorsal-fin base white with reticulated pattern, proximal third of dorsal-fin red; two parallel rows of rounded quadrilaterals present on trunk and tail rings, four quadrilaterals per ring; medioventral conical spines on the cleithral symphysis and the first trunk ring between the pectoral-fin bases pale brown to white. Fleshy appendages, pale brown to white, present on the frontal spine, principal snout spine, dorsum of rim of orbit, ventrolateral of snout, 3^rd and 6^th superior trunk ridge spines, and 3^rd and 7^th superior tail ridge spines. Other individuals of C. tupareomanaia observed at the type location and the Poor Knights Islands exhibited red and white countershading coloration or background color typically uniformly pale orange to dark red, respectively (Fig. 6B–F). In alcohol, head and body color pale cream to light brown. Fins hyaline.

Distribution and habitat.—Cylix tupareomanaia is thus far known only from Taitokerau Northland, New Zealand, including Pēwhairangi (Bay of Islands), Nukutaunga (Cavalli Islands), Tawhiti Rahi and Aorangi (Poor Knights Islands), and the coastal headlands off Whangaruru (Fig. 7). At the type locality, C. tupareomanaia was observed in mixed habitat on a vertical rock wall that was covered in encrusting coralline algae, bryozoans, sponges, solitary corals, and turf algae, and which faced a rocky outcrop exposed to the open ocean. The rock wall was subject to moderate ocean swell as was evident from the accumulated debris of detached and decomposed algae on the sandy to rubble bottom of the channel at a depth of 17–18 m. The holotype was collected below the Ecklonia radiata kelp line; it was observed moving about in close proximity to another individual of the same species, which appeared to represent a male–female pair. Additional reef fishes observed on and at the base of the rock wall included: Gobiopsis atrata (Gobiidae); Forsterygion flavonigrum, F. maryannae, and Notoclinops segmentatus (Tripterygiidae); Aplodactylus arctidens (Aplodactylidae); Coris sandeyeri and Notolabrus tetricus (Labridae); Chromis dispilus (Pomacentridae); and Chrysophrys auratus (Sparidae).

Species composition and biodiversity around the North Island of New Zealand indicate subdivision of inshore marine reef ichthyofauna into three regional biogeographic groups or eco-regions, including: western North Island coast; northeastern North Island coast and offshore islands; and Manawatāwhi Three Kings Islands (Brook, 2002). Cylix tupareomanaia may be restricted to the warm temperate waters off the north-eastern coast of the North Island and its offshore islands where it has been collected and observed. The coastal headlands and offshore islands are strongly influenced by oceanic water masses and reflect higher overall species diversity (Brook, 2002); therefore, the new taxon may not occur in the other cooler regional biogeographic areas. Its occurrence further north and south, however, may be confirmed by comprehensive sampling for this cryptic species. The new species is likely endemic to temperate New Zealand; no observations as of yet have been recorded at Rangitāhua the Kermadec Islands, where more than 90% of the coastal ichthyofauna are of subtropical and tropical Indo-Pacific origin, in temperate or tropical Australia, including its offshore subtropical territories of Lord Howe and Norfolk Islands, nor in New Caledonia (Allen et al., 1976; Francis, 1993; Francis and Randall, 1993; Johnson, 1999; Hutchins, 2001; Gomon, 2007; Fricke et al., 2011; Larson et al., 2013; Francis and Duffy, 2015; Trnski et al., 2015; Clark et al., 2017).

Cryptic fish assemblages on temperate rocky reefs in New Zealand are dominated by the highly diverse triplefins (Tripterygiidae) and clingfishes (Gobiesocidae) and exhibit a high degree of endemism (Paulin and Roberts, 1993; Hickey et al., 2009; Roberts et al., 2015; Conway et al., 2017, 2018). Other diminutive cryptic reef species recorded include the blennies (Blenniidae), kelpfishes (Clinidae), gobies (Gobiidae), and pipefishes and seahorses (Syngnathidae). The recent discovery of the highly cryptic C. tupareomanaia is therefore a noteworthy addition to reef fish diversity in New Zealand based on the fact it hadn't been collected or observed in numerous biodiversity surveys of temperate marine ichthyofauna previously conducted in a wide range of habitats. These surveys were carried out in estuaries, shallow coastal bays, seagrass meadows, mangrove forests, open mainland coasts, peninsulas, nearshore islands, and passages within the Bay of Islands (Nicholson, 1979; Nicholson and Roberts, 1980; Francis et al., 2005, 2011; Kelly, 2007; Jones et al., 2009; Gordon et al., 2010), throughout northern New Zealand (Willan et al., 1979; Brook, 2002; Morrison et al., 2002, 2014; Francis et al., 2005; Leathwick et al., 2006; Edgar et al., 2013), along the coast of the East Cape Region (Roberts and Stewart, 2006), at various inshore and offshore islands, including Manawatāwhi Three Kings Islands (Hardy et al., 1987), Cavalli Islands (Nicholson, 1979), the Poor Knights Islands (Russell, 1970; Kelly, 2007), Aotea Great Barrier Island (Roberts et al., 1986; Sivaguru and Grace, 2004), the Mokohinau Islands (Housley, 1980), Hen Island (Willis, 1995), Cuvier Islands (Housley et al., 1981), Ahuahu Grea Mercury Island (Grace, 1976), Aldermen Islands (Grace, 1973), the Chatham Islands (Roberts, 1991), in the South Island (Francis, 1979; Leathwick et al., 2006; Gordon et al., 2010; Francis et al., 2011; Morrison et al., 2014), and the sub-Antarctic Auckland Islands (Kingsford et al., 1989).

Cylix tupareomanaia is currently known from very few collected specimens and observations, which suggests that this species occurs in low abundance throughout its range, is hard to find due to its diminutive size and excellent crypsis, only occasionally occurs within SCUBA depths, or is simply rare in the regions where surveys have been conducted. These inferences are supported by the fact that representatives of Idiotropiscis in southern Australia are uncommon in its respective distributions; only two records currently exist for I. larsonae, and seven for I. australe (OZCAM museum record search;  https://ozcam.ala.org.au/occurrences/search?taxa=Idiotropiscis#tab_recordsView).

Etymology.—The species epithet tupareomanaia is a neologism gifted by kaumātua (tribal elders) of Ngātiwai and references Home Point adjacent to the type locality, referred to by Ngātiwai as Tu Pare o Huia, meaning “the plume of the huia”; the huia was a bird that became extinct in the early 20^th century. Tu Pare o Manaia translates as “the garland of the Manaia.” The pare, or garland, references the pentamerous head crest of the new species, and Manaia is the Māori name for a seahorse, and is also an ancestor that appears as a stylized figure used in Māori carvings representing a guardian.

Remarks.—Apparent ontogenetic differences in morphological features of the head were observed between the specimens of C. tupareomanaia examined herein (Fig. 2). The smallest female (Fig. 2A, AIM MA122274, 31.4 mm SL, holotype) exhibits a cup-like crest on the supraoccipital that is highly elevated anteriorly, distinct median supraoccipital spine at convergence of anterior edges of the coronet, protruding well anteriorly; three dorsal spines at midline of snout on mesethmoid bones, exceptionally large principal dorsal spine at confluence with anterior continuations of supraorbital ridges, the two anterior dorsal spines small, and the lateral head spine directly ventral of the cup-like supraoccipital crest consists of distinct but small paired spines. The morphological features in the larger female paratype (Fig. 2B, NMNZ P.056154, 35.5 mm SL) are less pronounced: the median supraoccipital spine presents as a distinct but blunt spine protruding anteriorly, the snout possesses two dorsal spines, the principal spine and one small anterior spine, and the lateral head spine directly ventral of the bony pentamerous bony crest consists of small but merged paired spines. In contrast, the adult male paratype (Fig. 2C, NMNZ P.046322, 55.5 mm SL) exhibits a cup-like supraoccipital crest that is low, less elevated, angled somewhat posteriorly, and cup-like in dorsal view, the median frontal spine a minute but discernible ridge, wedge-like in appearance, one large principal spine at midline of snout, and the lateral head spine directly ventral of the pentamerous bony crest is merged as one rugose spine.

Diagnosis.—A genus of the Syngnathidae that shares numerous morphological synapomorphies with Cylix and Idiotropiscis, including head angled ventrally approximately 25° from the principal body axis, enclosed brood pouch, brood pouch plates, prehensile tail, and absence of caudal fin. However, Acentronura differs from its co-familials by the following combination of characters: supraoccipital low, not elevated, with distinct dorsomedial crest, followed by an elevated bony dimple; bilateral bony lobed protuberances on the posterolateral margins of the post-temporal bones; anterior nuchal plate absent; posterior nuchal plate present anterior to cleithrum with dorsomedial crest-like ridge along its dorsum, large gap present between the supraoccipital and posterior nuchal plate; small blunt spine midway between orbit and lobed protuberance on operculum; cleithral ring distinct, discontinuous mid-dorsally; single gill slit between supraoccipital and cleithral ridge; rim of orbit projecting dorsolaterally and slightly ventrolaterally; spines absent on principal trunk and tail ridges.

Type species.—Hippocampus gracilissimus Temminck and Schlegel, 1850.

Acentronura breviperula Fraser-Brunner and Whitley, 1949: 148, fig. 1 (Mabuiag, Torres Strait, Queensland).

Diagnosis.—See generic diagnosis. Acentronura breviperula differs from its congeners by the following combination of characters: supraoccipital consisting of a distinct bony bipartite dorsomedial crest, segments arcuate in lateral view, followed by an elevated and long bony dimple; posterior margin of second segment of dorsomedial crest merging within the bony dimple, which is approximately one-third longer than the dorsomedial crest and tapered posteriorly.

Description.—Morphometric and meristic characters listed in Tables 2–4. Superior trunk and tail ridges discontinuous below dorsal-fin base, lateral tail ridge present, inferior trunk ridge ends at anal ring, lateral trunk ridge confluent with inferior tail ridge. Head angled ventrally 25° from the principal body axis, the anterodorsal profile slightly conoid in lateral aspect; supraoccipital low, not elevated, with a distinct bony bipartite dorsomedial crest, segments arcuate in lateral view, followed by an elevated and long bony dimple; posterior margin of second segment of dorsomedial crest merging within the bony dimple, which is approximately one-third longer than the dorsomedial crest and tapered posteriorly; bilateral bony lobed protuberances on the posterolateral margins of the post-temporal bones (Fig. 10A); anterior nuchal plate absent (Fig. 9A); posterior nuchal plate present anterior to cleithrum with dorsomedial crest-like ridge along its dorsum, large gap between the supraoccipital and posterior nuchal plate; small blunt spine midway between orbit and lobed protuberance on operculum; cleithral ring distinct, discontinuous mid-dorsally; gill slit between supraoccipital and cleithral ridge; rim of orbit projecting dorsolaterally and slightly ventrolaterally; snout spine absent; interorbital narrow, depressed; opercular ridge distinct, entire, angled dorsally toward gill opening; swelling of gular region ventroposterior to orbit absent; pectoral-fin base without distinct ridges, low, strongly elevated ventrolateral bulge supporting the pectoral-fin absent; trunk deepest anteriorly, principal body ridges distinct; principal body ridge spines absent; caudal fin absent. Acentronura breviperula exhibits strong sexual dimorphism associated with the presence of a brood pouch. The brood pouch is formed along the ventral midline of the tail and is present below the anteriormost eight tail rings (Fig. 11A).

Distribution.—Acentronura breviperula is known from the tropical Indo-West Pacific, from East Africa, Madagascar, the Red Sea, Persian Gulf, Papua New Guinea, Torres Strait, northern Great Barrier Reef, Australia, New Caledonia, and Taiwan (Fraser-Brunner and Whitley, 1949; Dawson, 1985; Kuiter, 2000, 2003; Fricke and Kulbicki, 2006; Chen, 2017; Fricke et al., 2019).

Material examined.—Acentronura breviperula: CAS 247135, female, 40.1 mm SL, channel between Iles aux Canards and Noumea, Anse Vate Bay, New Caledonia, 22°18′23.8″S, 166°26′07.9″E, depth 23 m, H. Hamilton and G. Short, 18 October 2008.

Hippocampus gracilissimus Temminck and Schlegel, 1850: 274, pl. 120, fig. 6 (Japan).

Atelurus germani Duméril, 1870: 584 (Cochin, China).

Diagnosis.—See generic diagnosis. Acentronura gracilissima differs from its congeners by the following combination of characters: supraoccipital consisting of a distinct dorsomedial crest, non-segmented, ridge-like in lateral view, followed by an elevated and bony dimple; bony dimple approximately one-third in length of dorsomedial crest.

Description.—Morphometric and meristic characters listed in Tables 2–4. Superior trunk and tail ridges discontinuous below dorsal-fin base, lateral tail ridge present, inferior trunk ridge ends at anal ring, lateral trunk ridge confluent with inferior tail ridge. Head angled ventrally 25° from the principal body axis, the anterodorsal profile slightly conoid in lateral aspect; supraoccipital, low, not elevated, with a distinct dorsomedial crest, non-segmented, ridge-like in lateral view, followed by an elevated and bony dimple; bony dimple approximately one-third in length of dorsomedial crest; bilateral bony lobed protuberances on the posterolateral margins of the post-temporal bones (Fig. 10B); anterior nuchal plate absent (Fig. 9B); posterior nuchal plate present anterior to cleithrum with dorsomedial crest-like ridge along its dorsum, large gap present between the supraoccipital and posterior nuchal plate; small blunt spine midway between orbit and lobed protuberance on operculum; cleithral ring distinct, discontinuous mid-dorsally; single gill slit between supraoccipital and cleithral ridge; rim of orbit projecting dorsolaterally and slightly ventrolaterally; snout spine absent; interorbital narrow, depressed; opercular ridge distinct, entire, angled dorsally toward gill opening; swelling of gular region ventroposterior to orbit absent; pectoral-fin base without distinct ridges, low, strongly elevated ventrolateral bulge supporting the pectoral-fin absent; trunk deepest anteriorly, principal body ridges distinct; principal body ridge spines absent; caudal fin absent. Acentronura gracilissima exhibits strong sexual dimorphism associated with the presence of a male brood pouch. The brood pouch is formed along the ventral midline of the tail and is present below the anteriormost 14 tail rings (Fig. 8B). µCT scanning of the specimen (Fig. 9B) revealed the brood pouch is enclosed by 14 arcuate bony extensions, which extend ventrolaterally from the anterior ventral plate ridges of the tail and are reduced in size posteriorly. The anteriormost pouch plate is broad and paddle-shaped at ventrocaudal margin and curved posterolaterally relative to other pouch plates. The second pouch plate appears to consist of double arcuate bony extensions merged as one bony extension. The posteriormost pouch plate is diminutive in size.

Distribution.—Acentronura gracilissima is known from the tropical western Pacific from New Caledonia, Japan, Indochina, and the South China Sea (Dawson, 1985; Rivaton and Richer de Forges, 1990; Randall and Lim, 2000; Nakae et al., 2018; Araki et al., 2019).

Material examined.—Acentronura gracilissima: CAS-SU 6681, 70.4 mm SL, Honshu Island, Sagami Sea, Japan, 35°09′34.0″N, 139°29′37.9″E, date collected 1900.

Acentronura tentaculata Günther, 1870: 516 (Suez, Egypt).

Syngnathoides algensis Fourmanoir, 1954: 210 (Dzaoudzi, Mayotte Island, Commore Island).

Acentronura mossambica Smith, 1963: 522, pl. 76, figs. f, g (Inhaca and Inhambane Estuary, Mozambique).

Diagnosis.—See generic diagnosis. Acentronura tentaculata differs from its congeners by the following combination of characters: supraoccipital consists of distinct bony bipartite dorsomedial crest, segments arcuate in lateral view, followed by an elevated and bony dimple; posterior margin of second segment of dorsomedial crest located at opening of, but not merged within, the bony dimple, which is approximately equal in length to the dorsomedial crest and tapered posteriorly.

Description.—Morphometric and meristic characters listed in Tables 2–4. Superior trunk and tail ridges discontinuous below dorsal-fin base, lateral tail ridge present, inferior trunk ridge ends at anal ring, lateral trunk ridge confluent with inferior tail ridge. Head angled ventrally 25° from the principal body axis, the anterodorsal profile slightly conoid in lateral aspect; supraoccipital, low, not elevated, with a distinct bony bipartite dorsomedial crest, segments arcuate in lateral view, followed by an elevated and bony dimple; posterior margin of second segment of dorsomedial crest located at opening of, but not merged within, the bony dimple, which is approximately equal in length to the dorsomedial crest and tapered posteriorly; bilateral bony lobed protuberances on the posterolateral margins of the post-temporal bones (Fig. 10C); anterior nuchal plate absent (Fig. 9C–D); posterior nuchal plate present anterior to cleithrum with dorsomedial crest-like ridge along its dorsum, large gap present between the supraoccipital and posterior nuchal plate; small blunt spine midway between orbit and lobed protuberance on operculum; cleithral ring distinct, discontinuous mid-dorsally; single gill slit between supraoccipital and cleithral ridge; rim of orbit projecting dorsolaterally and slightly ventrolaterally; snout spine absent; interorbital narrow, depressed; opercular ridge distinct, entire, angled dorsally toward gill opening; swelling of gular region ventroposterior to orbit absent; pectoral-fin base without distinct ridges, low, strongly elevated ventrolateral bulge supporting the pectoral-fin absent; trunk deepest anteriorly, principal body ridges distinct; principal body ridge spines absent; caudal fin absent. Acentronura tentaculata exhibits strong sexual dimorphism associated with the presence of a male brood pouch. The brood pouch is formed along the ventral midline of the tail and is present below the anteriormost 12 tail rings (Fig. 8C–D). µCT scanning of the material (Fig. 9C–D) revealed the brood pouch is enclosed by 12 arcuate bony extensions, which extend ventrolaterally from the anterior ventral plate ridges of the tail and are reduced in size posteriorly. The anteriormost pouch plate is broad and paddle-shaped at ventrocaudal margin and curved posterolaterally relative to other pouch plates. The posteriormost pouch plate is diminutive in size.

Distribution.—Acentronura tentaculata is known from the tropical Indo-West Pacific, from East Africa, Madagascar, the Red Sea, Arabian and Persian gulfs to Torres Strait, Philippines, the northern Great Barrier Reef, Australia, and New Caledonia (Dawson, 1985; Rivaton and Richer de Forges, 1990; McKenna, 2003; Fricke and Kulbicki, 2006; Al-Jufaili et al., 2010; Grandcourt, 2012; Nakae et al., 2018).

Material examined.—Acentronura tentaculata: CAS 247139, male, 50.8 mm SL, female, 53.9 mm SL, Tamaraw Beach, South Puerto Galera, Philippines, 13°30 ′03.8 ″N, 120°53′40.2″E, Hearst Philippine Biodiversity Expedition, station PG-011, B. Moore and H. Hamilton, 3 June 2011.

Diagnosis.—A genus of the Syngnathidae that shares numerous morphological synapomorphies with Acentronura and Cylix, including head angled ventrally approximately 25° from the principal body axis, enclosed brood pouch, brood pouch plates, prehensile tail, and absence of caudal fin. However, Idiotropiscis differs from its co-familials by the following combination of characters: supraoccipital is elevated with a distinct and raised bony dorsomedial crest; posterolateral margins of post-temporal bones expanded moderately anteriorly taking the form of protuberances; anterior nuchal plate absent; posterior nuchal plate present anterior to cleithrum with dorsomedial crest-like ridge along its dorsum, large gap present between the supraoccipital and posterior nuchal plate; small blunt spine midway between orbit and lobed protuberance on operculum; cleithral ring distinct, discontinuous mid-dorsally; bilateral gill slits situated laterally on head between supraoccipital and cleithrum.

Acentronura australe Waite and Hale, 1921: 317–318, fig. 53 (St. Vincent Gulf, South Australia).

Diagnosis.—See generic diagnosis. Idiotropiscis australe differs from its congeners by the following combination of characters: distinct raised bony multipartite dorsomedial crest on the supraoccipital, the four segments arcuate in lateral view, spanning the complete frontal from anterior margins of the interorbital to the supraoccipital, protruding anteriorly; posterolateral margins of post-temporal bones expanded moderately anteriorly taking the form of curved protuberances; small dorsal snout spine present medially on mesethmoid bone.

Description.—General body shape as in Figure 13. Morphometric and meristic characters listed in Tables 2–4. Superior trunk and tail ridges discontinuous below dorsal-fin base, lateral tail ridge present, inferior trunk ridge ends at anal ring, lateral trunk ridge confluent with inferior tail ridge. Head angled ventrally 25° from the principal body axis, the anterodorsal profile slightly conoid in lateral aspect, rising from short snout to an elevated supraoccipital; distinct raised bony multipartite dorsomedial crest on the supraoccipital, the four segments arcuate in lateral view, spanning the complete frontal from anterior margins of the interorbital to the supraoccipital, protruding anteriorly; posterolateral margins of post-temporal bones expanded moderately anteriorly taking the form of curved protuberances (Fig. 14A); anterior nuchal plate absent (Fig. 13A); posterior nuchal plate present anterior to cleithrum with dorsomedial crest-like ridge along its dorsum, large gap present between the supraoccipital and posterior nuchal plate; small blunt spine midway between orbit and lobed protuberance on operculum; cleithral ring distinct, discontinuous mid-dorsally; gill openings as small bilateral slits directly situated laterally on head between supraoccipital and cleithrum; small dorsal snout spine present medially on mesethmoid bone; interorbital narrow, depressed; opercular ridge low, entire, angled dorsally toward gill opening; slight swelling of gular region ventroposterior to eye; pectoral-fin base without distinct ridges, on strongly elevated ventrolateral bulge; trunk deepest anteriorly, principal body ridges distinct; principal body ridge spines absent. Caudal fin absent. Idiotropiscis australe exhibits strong sexual dimorphism associated with the presence of a male brood pouch. The brood pouch is formed along the ventral midline of the tail and is present below the anteriormost 11 tail rings (Fig. 12A). µCT scanning of the material (Fig. 13A) revealed the brood pouch is enclosed by 11 arcuate bony extensions, which extend ventrolaterally from the anterior ventral plate ridges of the tail and are reduced in size posteriorly. The anteriormost pouch plate is broad and paddle-shaped at ventrocaudal margin and curved posterolaterally relative to other pouch plates. The posteriormost pouch plate is diminutive in size.

Distribution.—Idiotropiscis australe is endemic to the temperate waters of southern and southwestern Australia, from Cape Jarvis and the Gulf St Vincent, South Australia, and Carnac Island, Western Australia (Dawson, 1985).

Material examined.—Idiotropiscis australe: SAMA F2657, Yankalilla, South Australia, Australia, 35.597767°S, 138.097511°E, depth 20 m; WAM P.25346-015, Australia, Western Australia, Carnac Island, Gage Roads, dredge, J. Scott, 30 June 1975; WAM P.33542-001, Success Bank, Cockburn Sound, Western Australia, 32.083097°S, 115.683344°E, depth 4 m, 3 November 1997; WAM P.33543-001, male, Owen Anchorage, Cockburn Sound, Western Australia, Australia, 32.114459°S, 115.749989°E, depth 12 m, 1 November 1997.

Acentronura (Idiotropiscis) larsonae Dawson, 1984: 157–158, figs. 1, 2 (Alpha Island, Monte Bello Islands, Western Australia).

Diagnosis.—See generic diagnosis. Idiotropiscis larsonae differs from its congeners by the following combination of characters: bony dorsomedial crest on the supraoccipital, strongly elevated, tripartite, the three large segments arcuate in lateral view, spanning the complete frontal from anterior margins of the interorbital to the supraoccipital, compressed laterally, protruding anteriorly; posterolateral margins of post-temporal bones expanded slightly anteriorly taking the form of flat protuberances, not prominent; rim of orbit projecting slightly dorsolaterally and ventrolaterally; small dorsal snout spine present medially on mesethmoid bone; body compressed laterally.

Description.—Morphometric and meristic characters listed in Tables 2–4. Superior trunk and tail ridges discontinuous below dorsal-fin base, lateral tail ridge present, inferior trunk ridge ends at anal ring, lateral trunk ridge confluent with inferior tail ridge. Head angled ventrally 25° from the principal body axis, the anterodorsal profile slightly conoid in lateral aspect; bony dorsomedial crest on the supraoccipital, strongly elevated, tripartite, the three large segments arcuate in lateral view, spanning the complete frontal from anterior margins of the interorbital to the supraoccipital, compressed laterally, protruding anteriorly; posterolateral margins of post-temporal bones expanded slightly anteriorly taking the form of flat protuberances, not prominent and difficult to discern (Fig. 14B); anterior nuchal plate absent; posterior nuchal plate present anterior to cleithrum with dorsomedial crest-like ridge along its dorsum, large gap present between the supraoccipital and posterior nuchal plate; small blunt spine midway between orbit and lobed protuberance on operculum; cleithral ring distinct, discontinuous mid-dorsally; bilateral gill slits situated laterally on head between supraoccipital and cleithrum; median dorsal snout spine present on mesethmoid bone; interorbital narrow, depressed; rim of orbit projecting moderately dorsolaterally and ventrally; opercular ridge low, entire, angled dorsally toward gill opening; swelling of the gular region ventroposteriorly of eye absent; pectoral-fin base without distinct ridges, low, strongly elevated ventrolateral bulge supporting the pectoral-fin base absent; trunk compressed laterally, span of dorsum of pre-dorsal trunk rings less by half of dorsum of anterior post-dorsal tail rings, span of trunk at lateral and inferior ridges somewhat greater than span of dorsum of trunk; subdorsal rings four (spans three trunk rings and one tail rings vs. two trunk rings and two tail rings in paratype); principal body ridges distinct; superior tail ridge with slightly enlarged spines on 4^th, 12^th, and 16^th trunk rings. Caudal fin absent.

Idiotropiscis larsonae exhibits strong sexual dimorphism associated with the presence of a brood pouch in the male (Figs. 11C, 12B). The brood pouch is formed along the ventral midline of the tail and is present below the anteriormost nine tail rings. X-ray image of the holotype revealed the brood pouch is enclosed by nine arcuate bony extensions and reduced in size posteriorly. The female paratype exhibits well-developed ossification of the skeleton, including the strong ossification of the inferior and ventral trunk area as detected by µCT scanning (Fig. 13B).

Distribution.—Idiotropiscis larsonae is known only from the tropical waters of the Monte Bello Islands, north Western Australia (Dawson, 1985).

Material examined.—Idiotropiscis larsonae: NTM S.10805-001, adult male, holotype, Monte Bello Islands, Western Australia, Australia, 20°36′S, 115°37′E, depth 3–9 m, 22 April 1983; GCRL 21518, female, paratype, 33.0 mm SL, Monte Bello Islands, Western Australia, Australia, 20°36′S, 115°37′E, depth 3–9 m, 22 April 1983.

Idiotropiscis lumnitzeri Kuiter, 2004: 165, fig. 1 (Henrietta Head, La Perouse, Sydney, New South Wales, Australia); AMS I.38660-001 (holotype).

Diagnosis.—See generic diagnosis. Idiotropiscis lumnitzeri differs from its congeners by the following combination of characters: strongly elevated supraoccipital; large, prominent, and raised bony dorsomedial crest on the supraoccipital, dome-like in lateral view, protruding anteriorly; posterolateral margins of post-temporal bones expanded moderately anteriorly taking the form of tapered and winglike protuberances; rim of orbit projecting dorsolaterally; one large and blunt spine on cleithral at level of last pectoral-fin ray; small spine posterolateral to pectoral fin; superior trunk ridge with enlarged spines projecting dorsolaterally on 6^th and 10^th trunk rings; subdorsal spines four, last two superior trunk ridges ending under dorsal fin with subdorsal spines, first two superior tail ridges under dorsal fin with subdorsal spines.

Description.—Morphometric and meristic characters listed in Tables 2–4. Superior trunk and tail ridges discontinuous below dorsal-fin base, lateral tail ridge present, inferior trunk ridge ends at anal ring, lateral trunk ridge confluent with inferior tail ridge. Head large relative to body, angled ventrally 25° from the principal body axis, the anterodorsal profile conoid in lateral aspect; rising steeply from short snout to a prominent supraoccipital; large, prominent, and raised bony dorsomedial crest on the supraoccipital, dome-like in lateral view, dorsocaudal margin irregular, protruding anteriorly; posterolateral margins of post-temporal bones expanded moderately anteriorly taking the form of tapered and wing-like protuberances (Fig. 14C); cleithral ring distinct, prominent, discontinuous mid-dorsally; anterior nuchal plate absent; posterior nuchal plate present anterior to cleithrum with dorsomedial crest-like ridge along its dorsum, large gap present between the supraoccipital and posterior nuchal plate; cleithral ring distinct, low, discontinuous mid-dorsally at bony dorsomedial crest; rim of orbit projecting dorsolaterally; opercular ridge low, entire, angled dorsally toward gill opening; swelling of gular region ventroposterior to eye forming a transverse pair of blunt protuberances; pectoral-fin base without distinct ridges, on strongly elevated ventrolateral bulge (Fig. 15); trunk narrowest at 3^rd and 4^th ring; dorsum of 2^nd, 3^rd, and 4^th trunk rings noticeably broader than 5–11^th trunk rings; dorsal-fin base strongly raised dorsally; subdorsal rings four (spans two and a half trunk rings and one and a half tail rings), dorsal-fin base starting immediately posterior to 10^th trunk ring and ending immediately posterior to 2^nd tail ring; caudal fin absent. Body spines: large spine present on cleithral ring at level of last pectoral-fin ray (Fig. 15A); small spine present posterolateral to the pelvic fin (Fig. 15A); superior trunk ridge with enlarged spines projecting dorsolaterally on 6^th and 10^th trunk rings; subdorsal spines four, last two superior trunk ridges ending under dorsal fin with subdorsal spines, first two superior tail ridges under dorsal fin with subdorsal spines (Fig. 15B); large simple and branched dermal flaps present on anterior part of frontal ridge, ventral to eye, 4^th and 7^th superior trunk ridges, 7–9^th lateral and inferior trunk ridges, and on 5^th, 10^th, 15^th, 19^th, and 24^th superior and inferior tail ridges. The female specimen (AMS I.45395-001) exhibits well-developed ossification of the skeleton, including the strong ossification of the inferior and ventral trunk area as detected by µCT scanning (Fig. 13D). Idiotropiscis lumnitzeri exhibits strong sexual dimorphism associated with the presence of a male brood pouch. The brood pouch is formed along the ventral midline of the tail and is present below the anteriormost 11 tail rings (Fig. 12D). µCT scans revealed the brood pouch is enclosed by 11 arcuate bony extensions (Figs. 13C, 15B), which extend ventrolaterally from the anterior ventral plate ridges of the tail, are reduced in size posteriorly, the anteriormost extension and curved posterolaterally relative to the other extensions.

Distribution.—Idiotropiscis lumnitzeri is endemic to the temperate waters of southeastern Australia, from Cabbage Tree Bay, Manly, to Brush Island located south of Ulladulla Harbour, New South Wales (Kuiter, 2004).

Material examined.—Idiotropiscis lumnitzeri: AMS I.45395-001, female, 54.0 mm SL, N of Burrewarra Point, S of Batemans Bay, New South Wales, Australia, depth 22 m; CAS HH-0423, male, 69.9 mm SL, SW of Bare Island, Botany Bay, NSW, Australia, 33°59′33.3″S, 151°13′47.3″E, depth 18 m, 1 March 2007.