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Extinctions on land are often inferred from sparse sightings over time, but this technique is ill-suited for wide-ranging species. We develop a space-for-time approach to track the spatial contraction and drivers of decline of sawfishes. These iconic and endangered shark-like rays were once found in warm, coastal waters of 90 nations and are now presumed extinct in more than half (n = 46). Using dynamic geography theory, we predict that sawfishes are gone from at least nine additional nations. Overfishing and habitat loss have reduced spatial occupancy, leading to local extinctions in 55 of the 90 nations, which equates to 58.7% of their historical distribution. Retention bans and habitat protections are urgently necessary to secure a future for sawfishes and similar species.

Pristiophorus lanae Ebert and Wilms (1 specimen). ZSM 45812: presumably adult female, 900 mm TL, off Culasi, Antique province, Panay Island, Philippines, collected on 10 March 2016 by Alexandra Bagarinar and Wilfredo L. Campos., Published as part of Weigmann, Simon, Gon, Ofer, Leeney, Ruth H., Barrowclift, Ellen, Berggren, Per, Jiddawi, Narriman & Temple, Andrew J., 2020, Revision of the sixgill sawsharks, genus Pliotrema (Chondrichthyes, Pristiophoriformes), with descriptions of two new species and a redescription of P. warreni Regan, pp. 1-56 in PLOS ONE 15 (3) on page 3, DOI: 10.1371/journal.pone.0228791, http://zenodo.org/record/7415225

Pristiophorus cirratus (Latham) (2 specimens). LACM 42620–20: adult male, 870 mm TL, east of Sydney (33º46'S 151º49'E), collected by C.C Swift and pty on 09 September 1981 with 27 m headrope otter trawl, 421–507 m depth. ZMH 8503: juvenile male, 506 mm TL, RV 'Southern Surveyor', Station SS 5/94/95 (Bass Strait: 38º42.4'S 148º16.8'E), collected on 26 August 1994 with bottom trawl, 86–87 m depth., Published as part of Weigmann, Simon, Gon, Ofer, Leeney, Ruth H., Barrowclift, Ellen, Berggren, Per, Jiddawi, Narriman & Temple, Andrew J., 2020, Revision of the sixgill sawsharks, genus Pliotrema (Chondrichthyes, Pristiophoriformes), with descriptions of two new species and a redescription of P. warreni Regan, pp. 1-56 in PLOS ONE 15 (3) on page 3, DOI: 10.1371/journal.pone.0228791, http://zenodo.org/record/7415225

Pliotrema annae Weigmann, Gon, Leeney & Temple sp. nov. urn:lsid:zoobank.org:act: DE91D0E9-3AED-41FC-8CB6-09A53E50EEBD. Proposed English vernacular name: Anna's sixgill sawshark. Proposed German vernacular name: Annas Sechskiemer-Sägehai. Local name: Papa Unguja. Figs 15–25; Table 3. Pliotrema warreni: Gubanov [28]: 221 (in part)? The holotype and paratype are deposited in the Zoological Museum Hamburg (ZMH). Holotype ZMH 26361, presumably adult female, 981 mm TL fresh, caught on or near Kobela Reef (~ 6º29'35”S 39º22'21”E) in Menai Bay, Unguja Island, Zanzibar, in a demersal longline at ~ 20–25 m (i.e. set depth of the gear; water depth unknown but probably only 2–5 m deeper than this), haul time ~8 am, time of catch unknown but likely during hours of darkness, date 07 March 2019. Paratype ZMH 26362, presumably adult female, 980 mm TL fresh, 950 mm TL 70% ethanol preserved, caught off Zanzibar in a longline at ~ 25–35 m depth during hours of darkness, landed on 24 Feb 2017 in Kizimkazi-Dimbani, Zanzibar (two further specimens were landed at the same place but not retained on 23 Jan 2017: gravid female, ~ 980 mm TL, with six eggs and on 25 Jan 2017: female with saw cut off, ~ 580 mm to beginning of saw; both these specimens were also caught in a longline at ~ 25–35 m depth during hours of darkness). Measurements taken from the fresh photographs of the not retained gravid female show that this specimen can be assigned to P. annae sp. nov. based on the main morphometric characteristics, particularly the generally shorter snout. Diagnosis. A medium-sized six-gilled sawshark with the following characters: barbel origin to anterior nostrils 1.9–2.0 times anterior nostrils to symphysis upper jaw; prenarial length 1.6–1.7 times prebarbel length; preoral length 1.5–1.7 times interdorsal space; pectoral-fin anterior margin 1.4–1.5 times dorsal–caudal space; mouth width 2.7–3.2 times spiracle length. First dorsal fin originates about opposite pectoral-fin free rear tips. Lateral trunk dermal denticles tricuspidate, rather flat and imbricated. Color uniform medium to dark brown dorsally without longitudinal stripes; white ventrally but with few indistinct dark blotches on belly; fins with pronounced white posterior fin margins, particularly caudal and pectoral fins; dorsal rostrum surface with two distinct longitudinal dark stripes, lateral rostral teeth dark-edged. Monospondylous centra 53–54; precaudal diplospondylous centra 46–49; total vertebral centra 154. Pliotrema annae is distinguished from its two congeners by a combination of characteristics, including a generally shorter snout, with head length 34.2–34.5% TL, preorbital length 21.7–22.0% TL, preoral length 24.6–25.1% TL, prebarbel length 12.6–12.7% TL, and barbel origin to symphysis upper jaw 12.1–12.3% TL. Pliotrema annae further differs from its two congeners in lower total large lateral rostral tooth and ventral rostral spine counts, and a rostrum that is slightly constricted between barbel origin and nostrils. Like in P. kajae, the barbels are situated about half way from rostral tip to mouth, with prebarbel length about equidistant from barbel origin to symphysis of upper jaw. In contrast, the barbels are situated about two thirds way from rostral tip to mouth, with prebarbel length about twice distance from barbel origin to symphysis of upper jaw in P. warreni. Description of the holotype. Values of the paratype are presented in parentheses, more complex differences between holotype and paratype are described separately. Where relevant, ratios are based on horizontal measurements unless otherwise stated. Morphometric measurements and meristics are given in Table 3. External morphology. Body firm and slender, depressed forward of gills, abdomen subcircular in cross-section, tail subtriangular in cross-section, deepest at abdomen; not tapering gradually and evenly beyond pectoral fins; snout flattened, greatly extended, saw-like; abdomen elongate, horizontal head length 0.6 (0.6) times snout–anterior vent length, pectoral–pelvic space 19.0 (19.9)% TL; pelvic–caudal space 2.7 (2.7) times pelvic-fin length; tail flattened ventrally, elongate, snout–anterior vent length 1.3 (1.3) times anterior vent–caudal tip length; caudal peduncle short, dorsal–caudal space 9.1 (9.0)% TL, caudal peduncle height 4.9 (4.5) times in dorsal–caudal space and width 1.1 (1.1) times in height; ventrolateral keels well developed, extending from somewhat behind level of free rear tip of pelvic fins to beyond origin of ventral lobe of caudal fin, converging strongly near their posterior extremity; no precaudal pit; no median predorsal, postdorsal or preventral caudal grooves (Figs 15 and 16). https://doi.org/10.1371/journal.pone.0228791.t002 Head narrow, subtriangular and deepest at sixth gill slit, strongly depressed above eyes, head width 6.4 (6.8)% TL, 1.1 (1.0) times head height. Snout forming a very elongate, bladelike rostrum. Rostrum triangular in dorsal view; slightly constricted between barbel origin and nostrils, sides of rostrum nearly straight from tip to barbel origin but slightly concave in posterior part from barbel origin to origin of orbit; tip narrowly rounded; rostrum extending laterally below eyes as a well-defined suborbital ridge along ventrolateral edge of head, terminating somewhat behind level of posterior edge of spiracle (Fig 17). A slender, filamentous, dorsoventrally flattened barbel originating on the ventrolateral margin about half way from rostral tip to mouth on each side, with prebarbel length 1.0 (1.0) times distance from barbel origin to symphysis of upper jaw, 51.1 (50.7)% of preoral length and 12.6 (12.7)% TL. Barbel length 2.2 (2.3) times in prebarbel length and 2.1 (2.2) times in length from barbel origin to symphysis of upper jaw. Preorbital length, horizontally 5.3 (5.1) times mouth width, 14.5 (16.4) times spiracle length, 2.1 (2.1) times first dorsal-fin length, 4.3 (4.3) times rostral width at anterior nostrils; extremely narrow in lateral view; preoral length 24.6 (25.1)% TL, 3.8 (3.7) times head width, 4.9 (4.9) times rostral width at anterior nostrils, 7.4 (7.4) times rostral width at origin of barbels, 2.0 (2.0) times prebarbel length, 1.2 (1.2) times prenarial length, and 1.5 (1.7) times interdorsal space (Fig 17). (Continued) (Continued) https://doi.org/10.1371/journal.pone.0228791.t003 Large lateral rostral teeth of prenarial portion of rostrum variable in length, curved, rather stout, serrated, longest near barbel origin and near apex of rostrum posterior to anteriormost two teeth; longest tooth immediately anterior to barbels only slightly shorter than spiracle length, length 1.0 (1.0)% TL and 0.8 (0.9) times first complete interspace anterior to barbels, width 0.2 (0.2)% TL; anteriormost tooth close to tip of rostrum medium-sized, followed by a tiny tooth and the first large tooth; large teeth shortest near nostrils, longest rostral tooth posterior to nostrils 0.4 (0.3)% TL; large teeth absent behind nostrils but interstitial-like teeth present, short to very short and closely set, partially directed almost ventrally, particularly near mouth. Interspaces between large rostral teeth rather regularly sized, about as long as adjacent teeth, with 0–3 (1–3) smaller, variable interstitial teeth. Rostral tooth counts mostly symmetrical between left and right hand sides; left side with 17 (17) large teeth, right side with 17 (16); anterior to barbels left side with 10 (11) large rostral teeth, right side with 10 (10), posterior to barbels left side with 7 (6) large rostral teeth, right side with 7 (6); anterior to nostrils left side with 15 (15) ventral spines, right side with 15 (15), anterior to barbel origin left side with 9 (10) ventral spines, right side with 9 (10); one enlarged ventral spine, distinctly larger than the other ventral spines, present just in front of each nostril. Large rostral teeth (Fig 18a and 18b) with elongated crown and oval-shaped base, slightly bent to the rear and flattened towards the apex, forming anterior and posterior cutting edges at front and rear, the latter serrated by barbed hooks. Crown base with numerous short longitudinal ridges forming a pronounced transversal crest. Both, anterior and posterior faces of the root are curved outwards from the junction of crown and root towards the base of the root. The basal face shows a deep v-shaped median groove that is antero-posteriorly directed and has an oval-shaped cavity in the center. Large interstitial rostral teeth similar but with somewhat less pronounced serration. Small interstitial rostral teeth (Fig 18c) with blade-shaped crown and without serration. Crown of ventral spines elongated cone-shaped with a pronounced transversal basal ridge, root with roundish and pedestal-like base. Eyes lateral on head, moderately large, oval, length 2.8 (2.7)% TL; skeletal interorbital space 0.9 (0.9) times eye length, 9.0 (8.7) times in horizontal preorbital length; posterior eye notches and suborbital grooves present. Spiracles moderately large, length 1.5 (1.3)% TL and 0.5 (0.5) times eye length, left spiracle with 10 (11) folds, right one with 10 (11); spiracles strongly crescentic, oblique, directed posteroventrally from top to bottom, located just posterior to posterior eye notch, separated by a narrow but deep vertical groove along posterior margin of orbit, shorter than eye; upper edge below level of top of eye. Gill slits small, upright, weakly pleated, lateral on head, close to ventral surface, extending slightly onto ventral surface, subequal in length, sixth slit arches around pectoral-fin origin. Mouth moderately large, strongly inferior, broadly arched, symphysis about level with posterior edge of eye, width 4.1 (4.3)% TL and 1.6 (1.6) times in head width; upper labial furrows absent, lower furrows very short, 0.3 (0.3)% TL; corner of mouth partly concealed by lateral muscles of jaw (Fig 19). Teeth unicuspidate, in well-defined series, bases oval and flattened with short but pronounced, narrow median cusp near middle of jaw, no lateral cusps; cusps diminishing in height towards jaw angles, indistinct near jaw corners; about 4–5 series of functional teeth (Fig 20). Median cusp with labial face slightly convex and with both mesial and distal cutting edges weakly bent mesially and distally in occlusal view, respectively. The mesial and distal crown base parts somewhat curve apically. A pronounced and broad, irregularly shaped apron overlaps the junction of crown and root, building a notch at the junction with both mesial and distal crown base parts. Basal ornamentation, striae, reticulations and folds absent in both upper and lower jaw teeth. The lingual face of the cusp is strongly convex, a well-developed uvula is present at the central crown base. The mesial/distal latero-lingual crown faces curve strongly towards the apex of the crown, forming a sharp notch with the uvula. The root is anaulacorhizid and slightly arched without lobation. The outer surface of the root shows large basal foramina, which are mostly oval-shaped. The inner face of the root shows well-developed foramina along the crown-root junction at each side of the uvula. The basal face of the root is flat, partly showing some outer foramina. Nostrils small, widely separated, subcircular; nostril width 0.7 (0.7)% TL, 4.7 (4.5) times in internarial width, 6.2 (6.5) times in mouth width, 7.7 (7.7) times in width of rostrum at nostrils; located distinctly forward of level of anterior margin of eye; distance from anterior nostrils to symphysis of upper jaw 1.3 (1.3) times internarial space, distance from barbel origin to anterior nostrils 7.9 (8.3)% TL. Anterior nasal flaps well developed, leaf-like, extended ventrally beyond nostrils; incurrent and excurrent apertures surrounded by pronounced marginal lobes; no nasoral or circumnarial grooves; no dermal lobes (Fig 19). Lateral trunk dermal denticles densely set and overlapping, with flat, tricuspidate crowns (Fig 21). The lateral cusps are rather weakly pronounced but situated quite far anteriorly so that the median cusp is not much longer than the lateral cusps. The median ridge is strongly pronounced and reaches the tip of the median cusp. The lateral ridges are less pronounced and do not reach the tips of the lateral cusps. The surface of the denticles is only weakly structured by reticulations very close to base. Dermal denticles on rostrum fan-shaped, with an obtusely angled, weakly pronounced median cusp and no lateral cusps but with 6–7 strongly pronounced ridges (Fig 18d–18f). The surface of the rostral dermal denticles is only weakly structured by reticulations very close to base. Pectoral fins very large, anterior margin weakly convex, 13.4 (12.7)% TL and 1.9 (1.9) times inner margin; apex narrowly rounded; posterior margin weakly concave, directed across horizontal axis at about origin of first dorsal fin; inner margin convex and strongly notched basally; free rear tip angular (Figs 17 and 22a). Pelvic fins large, anterior margin almost straight to slightly convex, 7.1 (7.0)% TL, 1.6 (1.6) times in first dorsal-fin anterior margin, and 1.4 (1.4) times in second dorsal-fin anterior margin; apex narrowly rounded; posterior margin concave; inner margin weakly convex and slightly notched basally; free rear tip broadly rounded; origin distinctly posterior to level free tip of first dorsal fin and well forward of level second dorsal fin origin (Fig 22a). First dorsal fin broad, semifalcate, anterior margin slightly convex; apex narrowly rounded; posterior margin slanting posteroventrally, slightly convex distally, strongly concave in basal three quarters; inner margin straight, free rear tip narrowly pointed; origin about opposite pectoral-fin free rear tips; insertion and free rear tip clearly anterior to level pelvic-fin origins (Fig 22a). Second dorsal fin somewhat smaller than first but of similar shape, anterior margin weakly convex, apex very narrowly rounded; posterior margin weakly convex distally, strongly concave near basal three quarters; inner margin straight, free rear tip narrowly pointed; origin clearly behind level pelvic insertions; interdorsal space 1.5 (1.4) times first dorsal-fin length, 1.8 (1.6) times dorsal–caudal space; second dorsal-fin inner margin 1.1 (1.1) times subterminal caudal-fin margin (Fig 22b). Caudal fin short, dorsal margin slightly convex, length 19.1 (19.8)% TL, 1.2 (1.1) times in pelvic–caudal space and 4.6 (5.0) times terminal caudal margin; lower post-ventral lobe absent, upper post-ventral margin slightly convex; terminal lobe well developed, caudal terminal margin slightly concave, apices angular (Fig 22b). Ventral origin of caudal fin situated anteriorly due to low anterior fin ridge (Fig 22b). Cranium: four anterior-most basiventral cartilages laterally expanded, with curved, dorsally reflected margins. Chondrocranium and cranial nerves highly modified to accomodate the elongated rostrum. Foramen magnum surrounded by crescent-shaped occipital condyles. Dorsal fenestra of the precerebral fossa spindle-shaped, elongate and long, notched anteriorly and posteriorly (Fig 12b). Skeletal meristics (from radiographs): monospondylous trunk vertebral centra: 53 (54); diplospondylous precaudal centra: 49 (46); total precaudal centra: 102 (100); caudal centra: 52 (54); total centra: 154 (154). Coloration. Fresh, prior to preservation (types and unretained specimens, Figs 23, 24 and 25): color uniform medium to dark brown dorsally without longitudinal stripes, white ventrally but with few indistinct dark blotches on belly; fins translucent dusky but with white posterior fin margins, particularly pronounced at the posterior pectoral-fin margin and the upper post-ventral and terminal caudal-fin margins; rostrum translucent dusky, dark edged and with two distinct longitudinal stripes dorsally; lateral rostral teeth dark-edged; ventrolateral keels white. Color in preservative (type specimens, Fig 16): coloration similar to fresh coloration, ventral ground coloration yellowish instead of white as usual but dark blotches still present, ventrolateral keels also yellowish; dark edging of rostrum and lateral rostral teeth, as well as longitudinal dorsal rostral stripes still conspicuous. Size. A medium-sized sawshark species reaching about 981 mm TL. As one specimen of ~ 980 mm TL (not retained) contained six eggs, the holotype and paratype are presumably also adult. Distribution. Known only from off Zanzibar in depths of 20 to 35 m (Fig 14). All four known specimens of this new species were caught in these depths during hours of the darkness / twilight. As both other species of Pliotrema usually occur in much deeper waters, P. annae sp. nov. possibly also occurs in deeper waters during the day but enters shallow water during the night. The area in which the specimens were caught is directly adjacent to a dropoff along the southern tip of Unguja Island. The water depth descends rapidly from ~ 20 m to> 200 m. Accordingly, deep-water sharks such as sixgill sharks and spurdogs are caught, alongside oceanic species such as mako and silky sharks and coastal species such as tiger and bull sharks, smoothhounds, and reef sharks all in the same fishery. Pliotrema annae sp. nov. possibly also occurs off Kenya and/or Somalia following the short description of P. warreni in Gubanov [28]. Pliotrema annae sp. nov. is apparently the only species of the genus occurring in this area. Etymology. The new species is named after Anna Weigmann Huerta, the niece of the first author, to express its relationship to Pliotrema kajae, named after the first author's daughter Kaja Magdalena Weigmann.

Key to the valid species of Pliotrema 1a. Five pairs of gill openings, large lateral rostral teeth smooth.. ................................................................................... Pristiophorus 1b. Six pairs of gill openings, large lateral rostral teeth serrated (Pliotrema).. ....... ................ ‥.. ................................................................... ‥ 2. 2a. Barbels about two thirds way from rostral tip to mouth, with prebarbel length about twice distance from barbel origin to symphysis of upper jaw; rostrum not constricted between barbel origin and nostrils; a pronounced yellowish longitudinal stripe on dorsal surface.. .................................. Pliotrema warreni [South Africa, southern Mozambique]. 2b. Barbels about half way from rostral tip to mouth, with prebarbel length about equal to distance from barbel origin to symphysis of upper jaw; rostrum constricted between barbel origin and nostrils; dorsal surface without or with two longitudinal stripes.. ...................... ‥ 3. 3a. Snout long, head length 38.3–40.4% TL, preorbital length 25.7–27.3% TL, preoral length 28.6–31.3% TL, prebarbel length 14.8–16.2% TL, barbel origin to symphysis upper jaw 13.7– 15.0% TL; rostrum clearly constricted between barbel origin and nostrils; 21–31 large lateral rostral teeth; 38–43 upper jaw tooth rows, jaw teeth with sharp basal folds; pale to light brown dorsally with two yellowish stripes, uniform white ventrally, posterior fin margins with narrow white edges.. ...................... Pliotrema kajae sp. nov. [Madagascar, Mascarene Ridge]. 3b. Snout short, head length 34.2–34.5% TL, preorbital length 21.7–22.0% TL, preoral length 24.6–25.1% TL, prebarbel length 12.6–12.7% TL, barbel origin to symphysis upper jaw 12.1– 12.3% TL; rostrum only slightly constricted between barbel origin and nostrils; 16–17 large lateral rostral teeth; 35–37 upper jaw tooth rows, jaw teeth without basal folds; uniform medium to dark brown dorsally without longitudinal stripes, white ventrally but with few indistinct dark blotches on belly, posterior fin margins conspicuously white-edged.. .................................................... ‥... Pliotrema annae sp. nov. [Zanzibar]., Published as part of Weigmann, Simon, Gon, Ofer, Leeney, Ruth H., Barrowclift, Ellen, Berggren, Per, Jiddawi, Narriman & Temple, Andrew J., 2020, Revision of the sixgill sawsharks, genus Pliotrema (Chondrichthyes, Pristiophoriformes), with descriptions of two new species and a redescription of P. warreni Regan, pp. 1-56 in PLOS ONE 15 (3) on page 53, DOI: 10.1371/journal.pone.0228791, http://zenodo.org/record/7415225

Pliotrema warreni Regan. Proposed English vernacular name: Warren's sixgill sawshark. Proposed German vernacular name: Warrens Sechskiemer-Sägehai. Figs 26–30; Table 4. Material examined (18 specimens). Syntype (BMNH 1905.6.8.9): female, 805 mm TL, off the coast of Natal (kwaZulu–Natal), 73 m depth, received from Dr. E. Warren of the Natal Government Museum. Syntype (BMNH 1899.2.10.4): heavily dissected female (skeletal parts and remains of flesh and fins only), ~ 704 mm TL, False Bay, Cape of Good Hope, received from Dr. J.D.F. Gilchrist. DAFF01: adult male, 1022 mm TL, FRS 'Africana' Cruise AND00003, Station D00331 (off South Africa: 34.29º S 25.97 º E), collected on 15 May 2014, trawl 081, grid ID S 3659, depth 108 m. DAFF02: presumably adult female, 1176 mm TL, FRS 'Africana' Cruise CCH00009, Station D00743 (off South Africa: 35.59º S 20.82 º E), collected on 01 May 2016, trawl 014, grid ID S 2058, depth 94 m. DAFF03: gravid female, 1277 mm TL, FRS 'Africana' Cruise CCH00009, Station D00802 (off South Africa: 33.90º S 26.45 º E), collected on 17 May 2016, trawl 071, grid ID S 2326, depth 89 m. DMM I-E/4946: female, 785 mm TL, RV 'Ernst Haeckel' Cruise 51, off Mozambique, June to September 1980. ERB 1105: adult female, 1310 mm TL, FRS 'Africana' Cruise Afr-200, Station A 23549 (off South Africa: 35º30' S 20º 20' E), collected on 23 September 2004, trawl no. 018, grid no. 3069, trawl duration 30 min, 137 m depth (photographs only). ERB 1106: subadult male, 945 mm TL, Prawn Trawler, Tugela Bank, 29º14' S 31º31' E, 27 May to 02 June 2006, 10–25 m depth (photographs only). RBINS uncatalogued: adult female, 1300 mm TL, off South Africa, Zululand (SEM images only). SAIAB 186452: juvenile male, 456.4 mm TL, off KwaZulu-Natal, South Africa, 29º10'49.5” S 32º06'24.6” E, 18 August 2010. SAIAB 189132: juvenile female, 405.9 mm TL, off KwaZulu-Natal (Tugela Bank), South Africa, 29º07'30” S 31º45' E, 15 August 2009. SAIAB 208021: female, 925 mm TL, Great fish River mouth, 33º29'43" S 27º08'06" E, Eastern Cape, South Africa, found stranded on the beach, Warren Potts, 09 June 2019. SAM 33313: 1 specimen, taken off Mozambique, 26º19'0.12” S 33º08'60” E, trawl, 366 m depth, 09 June 1994 (photographs only). SAM 37244: two specimens, taken off Mozambique, 22º36'28.8” S 35º42'46.08” E, bottom trawl, 264 m depth, 16 October 2007 (photographs only). Uncatalogued: female, 920 mm TL fresh, RV 'Dr. Fridtjof Nansen', Survey 2007409, Station 61, off Mozambique, 22º 36.48' S 35º42.77' E, 261–264 m depth, bottom trawl # 18, duration 28.4 minutes, 16 Oct 2007 (taken together with three further specimens) (photographs only). USNM 199741: adult female, 1350 mm TL, RV 'Anton Bruun', Cruise 8, Station 396B, International Indian Ocean Expedition Seychelle Islands Program, 1964, off Delagoa Bay, Mozambique, 25.517º S 33.442 º E, 450–455 m depth, 40-ft shrimp trawl, 28 Sep 1964, collector L. W. Knapp (radiographs only). USNM 353830: one specimen, RV 'Africana', Cruise 106, Station A 13997, off South Africa, 33.92º S 26.68 º E, 101 m depth, otter trawl, 20 Sep 1992, collectors L. W. Knapp and P. C. Heemstra (radiographs only). Diagnosis. A large six-gilled sawshark with the following characters: barbel origin to anterior nostrils 1.4–1.6 times anterior nostrils to symphysis upper jaw; prenarial length 1.3–1.4 times prebarbel length; preoral length 1.8–2.3 times interdorsal space; pectoral-fin anterior margin 1.4–1.5 times dorsal–caudal space; mouth width 3.1–3.9 times spiracle length. First dorsal fin originates about opposite pectoral-fin free rear tips. Lateral trunk dermal denticles tricuspidate, rather flat and imbricated. Color medium to dark brown dorsally with a pronounced yellowish longitudinal stripe; uniform white ventrally; dorsal rostrum surface with two distinct longitudinal dark stripes, lateral rostral teeth dark-edged. Monospondylous centra 53–56; precaudal diplospondylous centra 49–51; total vertebral centra 154–158. Pliotrema warreni clearly differs from both new species in a rostrum that is not constricted between barbel origin and nostrils and barbels that are situated about two thirds way from rostral tip to mouth, with prebarbel length about twice, i.e. 1.7–2.1 times, distance from barbel origin to symphysis of upper jaw (vs. barbels situated about half way from rostral tip to mouth, with prebarbel length about equal, i.e. 1.0–1.1 times, distance from barbel origin to symphysis of upper jaw), prebarbel length 60.2–68.0% vs. 49.4–52.9% of preoral length, preoral length 1.5–1.7 vs. 1.9–2.0 times prebarbel length, and prenarial length 1.3– 1.4 vs. 1.5–1.7 times prebarbel length. Description. The description is based on the intact syntype BMNH 1905.6.8.9, as well as the four specimens DMM I-E/4946, SAIAB 186452, SAIAB 189132, and SAIAB 208021. Where relevant, ratios are based on horizontal measurements unless otherwise stated. Morphometric measurements and meristics are given in Table 4. External morphology. Body firm and slender, depressed forward of gills, abdomen subcircular in cross-section, tail subtriangular in cross-section, deepest at abdomen; not tapering gradually and evenly beyond pectoral fins; snout flattened, greatly extended, saw-like; abdomen elongate, horizontal head length 0.6–0.7 times snout–anterior vent length, pectoral–pelvic space 14.1–21.2% TL; pelvic–caudal space 2.4–2.8 times pelvic-fin length; tail flattened ventrally, elongate, snout–anterior vent length 1.4–1.5 times anterior vent–caudal tip length; caudal peduncle short, dorsal–caudal space 7.5–8.7% TL, caudal peduncle height 3.5–4.7 times in dorsal–caudal space and width 1.2–1.5 times in height; ventrolateral keels well developed, extending from slightly behind level of free rear tip of pelvic fins to beyond origin of ventral lobe of caudal fin, converging strongly near their posterior extremity; no precaudal pit; no median predorsal, postdorsal or preventral caudal grooves (Fig 26). Head narrow, subtriangular and deepest at sixth gill slit, strongly depressed above eyes, head width 6.3–7.1% TL, 1.2–1.3 times head height. Snout forming a very elongate, blade-like rostrum. Rostrum triangular in dorsal view; not constricted between barbel origin and nostrils, sides of rostrum nearly straight from tip to origin of orbit; tip narrowly rounded; rostrum extending laterally below eyes as a well-defined suborbital ridge along ventrolateral edge of head, terminating somewhat behind level of posterior edge of spiracle (Fig 27). A slender, filamentous, dorsoventrally flattened barbel originating on the ventrolateral margin about two thirds way from rostral tip to mouth on each side, with prebarbel length 1.7–2.1 times distance from barbel origin to symphysis of upper jaw, 60.2–68.0% of preoral length and 16.5–20.2% TL. Barbel length 1.9–3.5 times in prebarbel length and 1.1–1.8 times in length from barbel origin to symphysis of upper jaw. Preorbital length, horizontally 5.3–6.2 times mouth width, 18.9–21.5 times spiracle length, 2.3–3.0 times first dorsal-fin length, 3.9–4.6 times rostral width at anterior nostrils; extremely narrow in lateral view; preoral length 26.7– 30.2% TL, 3.8–4.4 times head width, 4.4–5.2 times rostral width at anterior nostrils, 5.9–7.6 times rostral width at origin of barbels, 1.5–1.7 times prebarbel length, 1.2–1.2 times prenarial length, and 1.8–2.3 times interdorsal space (Fig 27). Large lateral rostral teeth of prenarial portion of rostrum variable in length, curved, rather stout, serrated, longest about half way from apex of rostrum to barbel origin; longest tooth immediately anterior to barbels shorter than spiracle length, length 0.5–1.3% TL and 0.5–1.7 times first complete interspace anterior to barbels, width 0.1–0.3% TL; anteriormost tooth close to tip of rostrum small, followed by the first large tooth; large teeth shortest near nostrils, longest rostral tooth posterior to nostrils 0.2–0.8% TL; large teeth absent behind nostrils but interstitial-like teeth present, short to very short and closely set, partially directed almost ventrally, particularly near mouth. Interspaces between large rostral teeth rather regularly sized, about as long as adjacent teeth, with 2–4 smaller, variable interstitial teeth. Rostral tooth counts mostly symmetrical between left and right hand sides; left side with ~21–~34 large teeth, right side with ~21–~34); anterior to barbels left side with ~15–~17 large rostral teeth, right side with ~14–~18, posterior to barbels left side with ~6–~19 large rostral teeth, right side with ~5– ~18; anterior to nostrils left side with ~17–~24 ventral spines, right side with ~16–~27, anterior to barbel origin left side with ~11–~15 ventral spines, right side with ~10–~19; one enlarged ventral spine, distinctly larger than the other ventral spines, present just in front of each nostril. Large rostral teeth (Fig 28a–28c) with elongated crown and oval-shaped base, slightly bent to the rear and flattened towards the apex, forming anterior and posterior cutting edges at front and rear, the latter serrated by barbed hooks. Crown base with numerous short longitudinal ridges forming a pronounced transversal crest. Both, anterior and posterior faces of the root are curved outwards from the junction of crown and root towards the base of the root. The basal face shows a deep v-shaped median groove that is antero-posteriorly directed and has an oval-shaped cavity in the center. Large interstitial rostral teeth similar but with somewhat less pronounced serration in specimens of 704 mm TL (heavily dissected syntype BMNH 1899.2.10.4) or larger. Large interstitial rostral teeth without serration in specimens of 456.4 mm TL (juvenile male SAIAB 186452) or smaller. Small interstitial teeth (Fig 28d and 28e) with blade-shaped crown and without serration in all specimens. Crown of ventral spines (Fig 28f) elongated cone-shaped with a pronounced transversal basal ridge, root with roundish and pedestal-like base. The basal face has a large and deep roundish foramen in the center. (Continued) (Continued) https://doi.org/10.1371/journal.pone.0228791.t004 Eyes lateral on head, large, oval, length 2.9–4.0)% TL; skeletal interorbital space 0.8–1.0 times eye length, 8.7–11.7 times in horizontal preorbital length; posterior eye notches and suborbital grooves present. Spiracles moderately large, length 1.2–1.4% TL and 0.3–0.5 times eye length, left spiracle with 10–13 folds, right one with 10–13; spiracles strongly crescentic, oblique, directed posteroventrally from top to bottom, located just posterior to posterior eye notch, separated by a narrow but deep vertical groove along posterior margin of orbit, shorter than eye; upper edge below level of top of eye. Gill slits small, upright, weakly pleated, lateral on head, close to ventral surface, extending slightly onto ventral surface, subequal in length, sixth slit arches around pectoral-fin origin. Mouth large, strongly inferior, broadly arched, symphysis about level with posterior edge of eye, width 4.2–4.9% TL and 1.4–1.7 times in head width; upper labial furrows absent, lower furrows short, 0.5–0.6% TL; corner of mouth partly concealed by lateral muscles of jaw (Fig 27). Teeth unicuspidate, in well-defined series, bases oval and flattened with short but pronounced, narrow median cusp near middle of jaw, no lateral cusps; cusps diminishing in height towards jaw angles, indistinct near jaw corners; about 4–5 series of functional teeth (Fig 29). Median cusp with labial face slightly convex and with both mesial and distal cutting edges weakly bent mesially and distally in occlusal view, respectively. The mesial and distal crown base parts somewhat curve apically. A pronounced and broad, irregularly shaped apron overlaps the junction of crown and root, building a notch at the junction with both mesial and distal crown base parts. Basal ornamentation, striae or reticulations absent, sharp folds present in upper but absent in lower jaw teeth. The lingual face of the cusp is strongly convex, a well-developed uvula is present at the central crown base. The mesial/distal latero-lingual crown faces curve strongly towards the apex of the crown, forming a sharp notch with the uvula. The root is anaulacorhizid and slightly arched without lobation. The outer surface of the root shows up to four large basal foramina, which are mostly ovalshaped. The inner face of the root shows up to six well-developed foramina along the crownroot junction at each side of the uvula. The basal face of the root is flat, partly showing some outer foramina. Nostrils small, widely separated, subcircular; nostril width 0.6–1.1% TL, 3.1–5.4 times in internarial width, 4.4–6.8 times in mouth width, 5.9–9.2 times in width of rostrum at nostrils; located distinctly forward of level of anterior margin of eye; distance from anterior nostrils to symphysis of upper jaw 1.2–1.4 times internarial space, distance from barbel origin to anterior nostrils 5.5–6.6)% TL. Anterior nasal flaps well developed, leaf-like, extended ventrally beyond nostrils; incurrent and excurrent apertures surrounded by pronounced marginal lobes; no nasoral or circumnarial grooves; no dermal lobes (Fig 27). Lateral trunk dermal denticles densely set and slightly overlapping, with flat, tricuspidate crowns (Fig 28g and 28h). The lateral cusps are rather weakly pronounced but situated quite far anteriorly so that the median cusp is not much longer than the lateral cusps. The median ridge is strongly pronounced and reaches the tip of the median cusp. The lateral ridges are less pronounced and rarely reach the tips of the lateral cusps. The surface of the denticles is only weakly structured by reticulations close to base. Dermal denticles on rostrum fan-shaped, with an obtusely angled, weakly pronounced median cusp and no lateral cusps but with 6–7 strongly pronounced ridges. The surface of the rostral dermal denticles is only weakly structured by reticulations very close to base. Pectoral fins large, anterior margin weakly convex, 10.7–12.2% TL and 1.3–1.6 times inner margin; apex narrowly rounded; posterior margin weakly concave, directed across horizontal axis at about origin of first dorsal fin; inner margin convex and strongly notched basally; free rear tip angular (Fig 26). Pelvic fins moderately large, anterior margin almost straight to slightly convex, 5.8–6.8% TL, 1.5–1.8 times in first dorsal-fin anterior margin, and 1.4–1.6 times in second dorsal-fin anterior margin; apex narrowly rounded; posterior margin concave; inner margin weakly convex and slightly notched basally; free rear tip broadly rounded; origin distinctly posterior to level free tip of first dorsal fin and well forward of level second dorsal fin origin (Fig 26). First dorsal fin broad, semifalcate, anterior margin slightly convex; apex narrowly rounded; posterior margin slanting posteroventrally, slightly convex distally, strongly concave in basal three quarters; inner margin straight, free rear tip narrowly pointed; origin about opposite pectoral-fin free rear tips; insertion and free rear tip clearly anterior to level pelvic-fin origins (Fig 26). Second dorsal fin somewhat smaller than first but of similar shape, anterior margin weakly convex, apex very narrowly rounded; posterior margin weakly convex distally, strongly concave near basal three quarters; inner margin straight, free rear tip narrowly pointed; origin clearly behind level pelvic insertions; interdorsal space 1.4–1.6 times first dorsal-fin length, 1.6–1.9 times dorsal–caudal space; second dorsal-fin inner margin 0.8–1.1 times subterminal caudal-fin margin (Fig 26). Caudal fin short, dorsal margin slightly convex, length 18.0–19.1% TL, 1.0–1.2 times in pelvic–caudal space and 3.7–5.4 times terminal caudal margin; lower post-ventral lobe absent, upper post-ventral margin slightly convex; terminal lobe well developed, caudal terminal margin slightly concave, apices angular (Fig 26). Ventral origin of caudal fin situated anteriorly due to low anterior fin ridge (Fig 26c). Cranium: five anterior-most basiventral cartilages laterally expanded, with curved, dorsally reflected margins. Chondrocranium and cranial nerves highly modified to accomodate the elongated rostrum. Foramen magnum surrounded by crescent-shaped occipital condyles. Dorsal fenestra of the precerebral fossa egg-shaped, notched anteriorly and posteriorly (Fig 12c). Skeletal meristics (from radiographs): monospondylous trunk vertebral centra: 53–56; diplospondylous precaudal centra: 49–51; total precaudal centra: 103–106; caudal centra: 50– 55; total centra: 154–158. Coloration. Fresh, prior to preservation (ERB 1105, ERB 1106, SAIAB 208021 and Uncatalogued; Fig 30): ground color medium to dark brown dorsally with a pronounced yellowish longitudinal stripe; uniform white ventrally; fins translucent dusky, upper post-ventral caudalfin and pelvic-fin posterior margins narrowly edged white, weak white edges also present at posterior margins of pectoral and dorsal fins, as well as terminal caudal-fin margin; rostrum translucent dusky, dark edged and with two distinct longitudinal stripes dorsally; lateral rostral teeth dark-edged; ventrolateral keels white. Color in preservative (other material examined): coloration similar to fresh coloration but yellowish longitudinal dorsal stripe not detectable in all specimens, particularly after long-time storage in ethanol; ventral coloration uniform yellowish instead of white as usual, ventrolateral keels also yellowish; dark edging of rostrum and lateral rostral teeth still pronounced in most specimens but hardly detectable in the intact syntype which is more than 100 years old; longitudinal dorsal rostral stripes still conspicuous in all specimens including the intact syntype. Fresh photographs of one specimen caught off Mozambique and kindly provided by Oddgeir Berg Alvheim, as well as a photograph of one specimen from off South Africa, taken and kindly provided by Frederik Mollen, Elasmobranch Research Belgium, are shown in Fig 30. Size. A large sawshark species reaching at least 1360 mm TL but possibly attaining 1700 mm TL [14, 15]. Males are adolescent at 700 to 740 mm, mature at 830 mm and grow to at least 1120 mm TL, females are adolescent at around 950 to 1100 mm TL, are mature when over 1100 mm TL and attain at least 1360 mm TL [30]. The male specimen ERB 1106 is subadult at 945 mm TL. The size at birth is about 350 mm TL, the litter size 5–7 pups, but up to 17 developing eggs recorded [18, 30]. Distribution. Known from off South Africa and southern Mozambique in depths from 26 to 500 m (Fig 14). However, the maximum depth of 500 m is apparently based on erroneous data for the holotype of Pliotrema kajae sp. nov., in, Published as part of Weigmann, Simon, Gon, Ofer, Leeney, Ruth H., Barrowclift, Ellen, Berggren, Per, Jiddawi, Narriman & Temple, Andrew J., 2020, Revision of the sixgill sawsharks, genus Pliotrema (Chondrichthyes, Pristiophoriformes), with descriptions of two new species and a redescription of P. warreni Regan, pp. 1-56 in PLOS ONE 15 (3) on pages 38-50, DOI: 10.1371/journal.pone.0228791, http://zenodo.org/record/7415225, {"references":["29. Herman J, Ladeuze F. Odontologie des Elasmobranches actuels (ring folders). Bonheiden: Elasmobranch Research Belgium Archives; n. d.","14. Weigmann S. Annotated checklist of the living sharks, batoids and chimaeras (Chondrichthyes) of the world, with a focus on biogeographical diversity. J Fish Biol. 2016; 88 (3): 837 - 1037. https: // doi. org / 10. 1111 / jfb. 12874 PMID: 26860638","15. Compagno LJV, Ebert DA, Smale MJ. Guide to the sharks and rays of southern Africa. London: New Holland (Publishers) Ltd.; 1989.","30. Bass AJ, D'Aubrey JD, Kistnasamy N. Sharks of the east coast of southern Africa. v. The families Hexanchidae, Chlamydoselachidae, Heterodontidae, Pristiophoridae and Squatinidae. Invest Rep Oceanogr Res Inst Durban. 1975; 43: 1 - 50.","18. Compagno LJV. FAO species catalogue. Vol. 4, Sharks of the World. An annotated and illustrated catalogue of shark species known to date (Part 1, Hexanchiformes to Lamniformes). FAO Fish Synop. 1984; 4 (1), 125: 249 pp.","27. Compagno LJV, Ebert DA, Cowley PD. Distribution of offshore demersal cartilaginous fishes (Class Chondrichthyes) of the west coast of southern Africa, with notes on their systematics. A Afr J Mar Sci. 1991; 11 (1): 43 - 139. https: // doi. org / 10.2989 / 025776191784287664","28. Gubanov EP. Akuly Indiiskogo okeana. Atlas-opredelitel (Sharks of the Indian Ocean. Identification Handbook). Moscow: VNIRO; 1993."]}

Pristiophorus nudipinnis Günther (1 specimen). ZMH 8504: juvenile male, 474 mm TL, RV 'Southern Surveyor', Station SS 5/94/30 (Bass Strait: 39º00.1'S 146º35.8'E), collected on 24 August 1994 with bottom trawl, 43–44 m depth., Published as part of Weigmann, Simon, Gon, Ofer, Leeney, Ruth H., Barrowclift, Ellen, Berggren, Per, Jiddawi, Narriman & Temple, Andrew J., 2020, Revision of the sixgill sawsharks, genus Pliotrema (Chondrichthyes, Pristiophoriformes), with descriptions of two new species and a redescription of P. warreni Regan, pp. 1-56 in PLOS ONE 15 (3) on page 4, DOI: 10.1371/journal.pone.0228791, http://zenodo.org/record/7415225

Pristiophorus schroederi Springer and Bullis (4 specimens). Holotype (USNM 185946): juvenile female, 383 mm TL, RV 'Combat', Station 449 (east of Dog Rocks, Cay Sal Bank: 24º 05'N 79º46'W), collected on 24 June 1957 with beam trawl, 640 m depth (radiographs only). Two paratypes (USNM 185947): juvenile male, 645 mm TL and female, 805 mm TL, RV 'Silver Bay', Station 445 (north of Little Bahama Bank: 28º03'N 78º46'W), collected on 09 June 1958, 914– 951 m depth (radiographs only). USNM 202479: subadult male, 766 mm TL, RV 'Silver Bay', Station 2458 (Santaren Channel off Cuba: 23º40'N 79º18'W), collected by S. Springer on 05 November 1960 with bottom trawl, 530 m depth., Published as part of Weigmann, Simon, Gon, Ofer, Leeney, Ruth H., Barrowclift, Ellen, Berggren, Per, Jiddawi, Narriman & Temple, Andrew J., 2020, Revision of the sixgill sawsharks, genus Pliotrema (Chondrichthyes, Pristiophoriformes), with descriptions of two new species and a redescription of P. warreni Regan, pp. 1-56 in PLOS ONE 15 (3) on page 4, DOI: 10.1371/journal.pone.0228791, http://zenodo.org/record/7415225

Pristiophorus nancyae Ebert and Cailliet (23 specimens). Holotype (SAM 34013 / MB-F034013): adult male, 616 mm TL, RV 'Algoa', Mozambique Scad Survey, Station C00840 014 037 3074 (Mozambique Channel: 22º07'S 35º45'E), collected on 19 June 1994 with bottom trawl, 500 m depth (photographs only). Paratype (SAM 33477 / MB-F 033477): subadult male, 440 mm TL, same data as holotype (photographs only). Paratype (SAM 33502 / MB-F 033502): subadult female, 573 mm TL, RV 'Algoa', Mozambique Scad Survey, Station C00848 014 045 3179 (off South Mozambique: 25º21'S 34º30'E), collected on 21 June 1994 with bottom trawl, 286 m depth (photographs only). Five paratypes (SAM 33511 / MB-F 033511): two juvenile males (314 and 358 mm TL), one juvenile female (391 mm TL), two adult females (522 and 550 mm TL), RV 'Algoa', Mozambique Scad Survey, Station C00841 014 038 3118 (Mozambique Channel: 23º32'S 35º51'E), collected on 20 June 1994 with bottom trawl, 490 m depth (photographs only). DMM I-E/3460: two juvenile females, 268 mm TL and 361 mm TL, RV 'Ernst Haeckel', off Mozambique, 24º13'S 35º42'E, 30 October 1988, 450 m depth. DMM I-E/ 4506: adult female, 640 mm TL, RV 'Ernst Haeckel' Cruise 51, Haul 89/80, off Mozambique, 23º56'S 35º48'E, 15 June 1980 (photographs only). DMM I-E/4817: juvenile male, 351 mm TL, RV 'Ernst Haeckel' Cruise 51, Haul 567/80, off Mozambique, 23º56'S 35º48'E, 21 September 1980. DMM I-E/4872: adult male, 555 mm TL, off Mozambique, February to March 1983. DMM I-E/4902: adult female, 700 mm TL, off Mozambique, February to March 1983. ZMH 25963: adult male, 581 mm TL fresh, 578 mm TL 70% ethanol preserved, RV 'Vityaz' Cruise 17, Station 2560 (off Socotra Islands: 12º16'6”N 53º08'2”E–12º14'7”N 53º06'2”E), collected on 27 October 1988 with 29 m shrimp trawl, trawl no. 2, on the bottom for 45 min, 375–380 m depth. ZMH 25964: adult male, 547 mm TL fresh, 540 mm TL 70% ethanol preserved, same data as ZMH 25963. ZMH 25965: adult male, 563 mm TL fresh, 558 mm TL 70% ethanol preserved, same data as ZMH 25963. ZMH 25966: juvenile male, 334 mm TL fresh, 328 mm TL 70% ethanol preserved, same data as ZMH 25963. ZMH 25967: juvenile female, 327 mm TL fresh, 324 mm TL 70% ethanol preserved, same data as ZMH 25963. ZMH 25968: adult female, 574 mm TL fresh, 568 mm TL 70% ethanol preserved, RV 'Vityaz' Cruise 17, Station 2631 (off South Mozambique: 25º30'4”S 35º08'2”E–25º34'2”S 35º01'5”E), collected on 23 November 1988 with 29 m shrimp trawl, trawl no. 28, on the bottom for 78 min, 500–570 m depth. ZMH 25969: juvenile female, 283 mm TL fresh, 275 mm TL 70% ethanol preserved, RV 'Vityaz' Cruise 17, Station 2830 (off Socotra Islands: 12º14'8”N 53º06'2”E–12º17'8”N 53º 08'9”E), collected on 16 January 1989 with 29 m shrimp trawl, trawl no. 101, on the bottom for 80 min, 395–420 m depth. ZMH 25970: juvenile female, 374 mm TL fresh, 367 mm TL 70% ethanol preserved, same data as ZMH 25969. ZMMU P 14847: adult female, 621 mm TL, RV 'Prof. Mesyatsev' Cruise 5, Station 10 (off Kenya: 02º59'5”S 40º30'E), collected by A.D. Druzhinin on 22 December 1975, 287– 300 m depth., Published as part of Weigmann, Simon, Gon, Ofer, Leeney, Ruth H., Barrowclift, Ellen, Berggren, Per, Jiddawi, Narriman & Temple, Andrew J., 2020, Revision of the sixgill sawsharks, genus Pliotrema (Chondrichthyes, Pristiophoriformes), with descriptions of two new species and a redescription of P. warreni Regan, pp. 1-56 in PLOS ONE 15 (3) on page 3, DOI: 10.1371/journal.pone.0228791, http://zenodo.org/record/7415225

Pristiophorus japonicus Günther (4 specimens). Syntype (BMNH 1862.11.1.37): juvenile male, 734 mm TL, off Japan (photographs only). Syntype (BMNH 1867.2.20.1), female, ~ 1000 mm TL, off Japan (photographs only). Syntype (BMNH 1867.2.20.2), female, ~ 1200 mm TL, off Japan (photographs only). Syntype (BMNH 1953.8.10.6): juvenile female, ~ 700 mm TL, off Japan (photographs only)., Published as part of Weigmann, Simon, Gon, Ofer, Leeney, Ruth H., Barrowclift, Ellen, Berggren, Per, Jiddawi, Narriman & Temple, Andrew J., 2020, Revision of the sixgill sawsharks, genus Pliotrema (Chondrichthyes, Pristiophoriformes), with descriptions of two new species and a redescription of P. warreni Regan, pp. 1-56 in PLOS ONE 15 (3) on page 3, DOI: 10.1371/journal.pone.0228791, http://zenodo.org/record/7415225

Pliotrema kajae Weigmann, Gon, Leeney & Temple sp. nov. urn:lsid:zoobank.org:act: D4EF80CA-3448-4015-A96C-279C5A0A7970. Proposed English vernacular name: Kaja's sixgill sawshark. Proposed German vernacular name: Kajas Sechskiemer-Sägehai. Local name: vae vae. Figs 1–14; Tables 1–2. Poliotrema warreni (misspelling for Pliotrema): Séret [26]: 1. Pliotrema warreni: Compagno et al. [27]: 73 (in part), based on Séret [26]. Assuming that this new species does not occur off the southern African continent (South Africa, Mozambique), no records of Pliotrema kajae sp. nov. (as Pliotrema warreni) before Séret [26] have been found. All subsequent records of Pliotrema from off Madagascar are apparently based on Séret [26]. The holotype is deposited in the Muséum national d'Histoire naturelle, Paris (MNHN), 10 paratypes are deposited in the South African Institute for Aquatic Biodiversity (SAIAB), and one paratype in each of the Natural History Museum, London (BMNH), Ruth H. Leeney personal collection (RHL), and Simon Weigmann personal collection (SW), National Museum of Natural History, Smithsonian Institution, Washington D.C. (USNM), and Zoological Museum Hamburg (ZMH). Holotype MNHN 1987–1266, juvenile female, 560 mm TL, off Tulear (Madagascar), 23º 19'58.8” S 43º31'1.2” E, 320 m depth, Dec 1985. Paratypes (15) SAIAB 84039, gravid female, 1170 mm TL fresh, 1143 mm TL 70% ethanol preserved, RV 'Dr. Fridtjof Nansen', Survey 2008407, Station 7, Mascarene Ridge, 16º27.62'S 60º16.84'E, 214–219 m depth, bottom trawl # 22, duration 27.3 minutes, 14 Oct 2008 (taken together with 1 further specimen, which was not retained); SAIAB 84096, adult male, 970 mm TL fresh, 940 mm TL 70% ethanol preserved, RV 'Dr. Fridtjof Nansen', Survey 2008407, Station 11, Mascarene Ridge, 15º41.11'S 61º4.54'E, 302–305 m depth, bottom trawl # 22, duration 34.3 minutes, 18 Oct 2008 (taken together with 1 further specimen, which was not retained); SAIAB 189447, 1 gravid female, 3 of 6 mid- to late-term embryos (1 male: 246 mm TL; 2 females, 320 mm TL, 324 mm TL; three embryos of 243 mm TL, 318 mm TL, and 329 mm TL were donated to the ZMH, BMNH and USNM collections, respectively), and 4 early embryos (71+ mm TL with tail broken off, 95 mm TL, 103 mm TL, 110 mm TL), RV 'Dr. Fridtjof Nansen', Survey 2009408, Station 24, off western Madagascar, 21º58.79'S 43º8.38'E, 235–239 m depth, trawl, duration 30.1 minutes, 07 Sep 2009; BMNH 2019.1.28.1 (ex SAIAB 189447), male late-term embryo, 318 mm TL, data the same as SAIAB 189447; RHL-Mad-01 (dried rostrum), presumably adult female, estimated TL 1100 mm (TL estimated based on the prebarbel length [160 mm] in comparison to the ratios prebarbel length to TL in other type specimens), taken off southwestern Madagascar by local fishermen; SW 01–2016 (dried rostrum), presumably adult female, estimated TL 1300 mm (prebarbel length 191.1 mm), taken off southwestern Madagascar by local fishermen, USNM 443683 (ex SAIAB 189447), male late-term embryo, 329 mm TL, data the same as SAIAB 189447; ZMH 26360 (ex SAIAB 189447), female midterm embryo, 243 mm TL, data the same as SAIAB 189447. Diagnosis. A large six-gilled sawshark with the following characters: barbel origin to anterior nostrils 1.4–2.3 times anterior nostrils to symphysis upper jaw; prenarial length 1.5–1.7 times prebarbel length; preoral length 2.0–2.7 times interdorsal space; pectoral-fin anterior margin 1.2–1.6 times dorsal–caudal space; mouth width 2.8–6.6 times spiracle length. First dorsal fin originates about opposite pectoral-fin free rear tips. Lateral trunk dermal denticles tricuspidate, rather flat and imbricated. Color pale to light brown dorsally with two thin yellowish longitudinal stripes; uniform white ventrally; fins with rather indistinct white posterior fin margins; dorsal rostrum surface with two distinct longitudinal dark stripes, lateral rostral teeth dark-edged. Monospondylous centra 52–57; precaudal diplospondylous centra 48– 56; total vertebral centra 151–164. This new species is distinguished from its two congeners, Pliotrema warreni and the second new species, by a combination of characteristics, including most notably, a rostrum that is clearly constricted between barbel origin and nostrils. Furthermore, P. kajae has sharp folds in both upper and lower jaw teeth, as well as a posteriorly notched, teardrop-shaped dorsal fenestra of the precerebral fossa. Pliotrema kajae is further distinguished from P. warreni by barbels that are situated about half way from rostral tip to mouth, with prebarbel length about equidistant from barbel origin to symphysis of upper jaw (vs. barbels about two thirds way from rostral tip to mouth, with prebarbel length about twice distance from barbel origin to symphysis of upper jaw) and the presence of two indistinct, yellowish longitudinal stripes on the dorsal surface (vs. one pronounced yellowish longitudinal stripe). Pliotrema kajae also clearly differs from the second new species in a generally longer snout, more upper and lower jaw tooth rows, higher total large lateral rostral tooth and ventral rostral spine counts, and a pale to light brown dorsal coloration with two indistinct yellowish stripes, uniform white ventral coloration, and posterior fin margins with narrow white edges (vs. uniform medium to dark brown dorsally without longitudinal stripes, white ventrally but with few indistinct dark blotches on belly, posterior fin margins conspicuously white-edged). Description of the holotype. Values of the paratypes are presented in parentheses, more complex differences between holotype and paratypes are described separately. Where relevant, ratios are based on horizontal measurements unless otherwise stated. Morphometric measurements and meristics are given in Table 1. External morphology. Body firm and slender, depressed forward of gills, abdomen subcircular in cross-section, tail subtriangular in cross-section, deepest at abdomen; not tapering gradually and evenly beyond pectoral fins; snout flattened, greatly extended, saw-like; abdomen elongate, horizontal head length 0.6 (0.6–0.7) times snout–anterior vent length, pectoral– pelvic space 16.1 (13.5–18.5)% TL; pelvic–caudal space 2.7 (2.5–3.0) times pelvic-fin length; tail flattened ventrally, elongate, snout–anterior vent length 1.5 (1.5–1.6) times anterior vent– caudal tip length; caudal peduncle short, dorsal–caudal space 7.7 (6.7–9.1)% TL, caudal peduncle height 3.5 (2.8–4.0) times in dorsal–caudal space and width 1.0 (0.8–1.6) times in height; ventrolateral keels well developed, extending from slightly behind level of free rear tip of pelvic fins (from about level to slightly behind level) to beyond origin of ventral lobe of caudal fin, converging strongly near their posterior extremity; no precaudal pit; no median predorsal, postdorsal or preventral caudal grooves (Figs 1 and 2). Head narrow, subtriangular and deepest at sixth gill slit, strongly depressed above eyes, head width 6.7 (6.8–8.7)% TL, 1.3 (0.9–1.9) times head height. Snout forming a very elongate, blade-like rostrum. Rostrum triangular in dorsal view; constricted between barbel origin and nostrils, sides of rostrum nearly straight from tip to barbel origin but concave in posterior part from barbel origin to origin of orbit; tip narrowly rounded; rostrum extending laterally below eyes as a well-defined suborbital ridge along ventrolateral edge of head, terminating somewhat behind level of posterior edge of spiracle (Fig 3). A slender, filamentous, dorsoventrally flattened barbel originating on the ventrolateral margin about half way from rostral tip to mouth on each side, with prebarbel length 1.0 (1.0–1.1) times distance from barbel origin to symphysis of upper jaw, 51.1 (49.4–52.9)% of preoral length and 15.6 (14.8–16.2)% TL. Barbel length 1.6 (0.8–2.3) times in prebarbel length and 1.5 (0.8–2.1) times in length from barbel origin to symphysis of upper jaw. Preorbital length, horizontally 6.0 (4.8–6.0) times mouth width, 19.7 (16.4–31.5) times spiracle length, 2.9 (2.7–3.6) times first dorsal-fin length, 4.4 (3.4–4.9) times rostral width at anterior nostrils; extremely narrow in lateral view; preoral length 30.6 (28.6–31.3)% TL, 4.6 (3.4–4.4) times head width, 5.1 (4.0–5.4) times rostral width at anterior nostrils, 7.2 (6.0–8.2) times rostral width at origin of barbels, 2.0 (1.9–2.0) times prebarbel length, 1.2 (1.2–1.3) times prenarial length, and 2.3 (2.0– 2.7) times interdorsal space (Fig 3). Large lateral rostral teeth of prenarial portion of rostrum variable in length, curved, rather stout, serrated, longest near barbel origin and near apex of rostrum posterior to anteriormost two teeth; longest tooth immediately anterior to barbels only slightly shorter than spiracle length, length 1.1 (0.9–2.3)% TL and 0.8 (0.9–2.6) times first complete interspace anterior to barbels, width 0.2 (0.2–0.4)% TL; anteriormost two large rostral teeth on each side of the rostrum very close to snout tip, without interstitial tooth between or anterior to them; large teeth shortest near nostrils, longest rostral tooth posterior to nostrils 0.6 (0.2–0.3)% TL; large teeth absent behind nostrils but interstitial-like teeth present, short to very short and closely set, partially directed almost ventrally, particularly near mouth. Interspaces between large rostral teeth rather regularly sized, about as long as adjacent teeth, with 2–4 (1–4) smaller, variable interstitial teeth. Rostral tooth counts mostly symmetrical between left and right hand sides; left side with 21 (22–31) large teeth, right side with 21 (22–31); anterior to barbels left side with 13 (12– 14) large rostral teeth, right side with 13 (13–14), posterior to barbels left side with 8 (9–17) large rostral teeth, right side with 8 (9–17); anterior to nostrils left side with 23 (~19–~24) ventral spines, right side with 23 (~19–~23), anterior to barbel origin left side with 13 (~11–~14) ventral spines, right side with 12 (~12–~13); one enlarged ventral spine, distinctly larger than the other ventral spines, present just in front of each nostril. Large rostral teeth (Fig 4a and 4b) with elongated crown and oval-shaped base, slightly bent to the rear and flattened towards the apex, forming anterior and posterior cutting edges at front and rear, the latter serrated by barbed hooks. Crown base with numerous short longitudinal ridges forming a pronounced transversal crest. Both, anterior and posterior faces of the root are curved outwards from the junction of crown and root towards the base of the root. The basal face shows a deep v-shaped median groove that is antero-posteriorly directed and has an oval-shaped cavity in the center. Interstitial rostral teeth (Fig 4c–4h) with blade-shaped crown and without serration (large interstitial rostral teeth serrated and similar to large lateral rostral teeth in all specimens larger than the holotype). Crown of ventral spines (Fig 4i and 4j) elongated cone-shaped with a pronounced transversal basal ridge, root with roundish and pedestal-like base. The basal face has a large and deep roundish foramen in the center. (Continued) (Continued) https://doi.org/10.1371/journal.pone.0228791.t001 Eyes lateral on head, large, oval, length 3.3 (2.8–5.2)% TL; skeletal interorbital space 0.9 (0.7–1.0) times eye length, 9.3 (6.1–9.5) times in horizontal preorbital length; posterior eye notches and suborbital grooves present. Spiracles moderately large, length 1.4 (0.8–1.6)% TL and 0.4 (0.2–0.6) times eye length, left spiracle with 12 (12–15) folds, right one with 13 (12– 15); spiracles strongly crescentic, oblique, directed posteroventrally from top to bottom, located just posterior to posterior eye notch, separated by a narrow but deep vertical groove along posterior margin of orbit, shorter than eye; upper edge below level of top of eye. Gill slits small, upright, weakly pleated, lateral on head, close to ventral surface, extending slightly onto ventral surface, subequal in length, sixth slit arches around pectoral-fin origin. Mouth large, strongly inferior, broadly arched, symphysis about level with posterior edge of eye, width 4.5 (4.4–5.4)% TL and 1.5 (1.3–1.8) times in head width; upper labial furrows absent, lower furrows short, 0.4 (0.4–0.5)% TL; corner of mouth partly concealed by lateral muscles of jaw (Fig 5). Teeth unicuspidate, in well-defined series, bases oval and flattened with short but pronounced, narrow median cusp near middle of jaw, no lateral cusps (cusps similar in paratypes except for adult male SAIAB 84096, which has distinctly longer cusps); cusps diminishing in height towards jaw angles, indistinct near jaw corners; about 4–5 series of functional teeth (Figs 6 and 7). Median cusp with labial face slightly convex and with both mesial and distal cutting edges weakly bent mesially and distally in occlusal view, respectively. The mesial and distal crown base parts somewhat curve apically. A pronounced and broad, irregularly shaped apron overlaps the junction of crown and root, building a notch at the junction with both mesial and distal crown base parts. Basal ornamentation, striae or reticulations absent, but sharp folds present in both upper and lower jaw teeth. The lingual face of the cusp is strongly convex, a well-developed uvula is present at the central crown base. The mesial/distal latero-lingual crown faces curve strongly towards the apex of the crown, partially forming a sharp notch with the uvula (Fig 6k and 6l). The root is anaulacorhizid and slightly arched without lobation. The outer surface of the root shows up to five large basal foramina, which are mostly oval-shaped. The inner face of the root shows up to six well-developed foramina along the crown-root junction at each side of the uvula. The basal face of the root is flat, partly showing some outer foramina. Nostrils small, widely separated, subcircular; nostril width 0.8 (0.7–1.0)% TL, 4.5 (3.8–5.6) times in internarial width, 5.7 (4.8–7.0) times in mouth width, 7.7 (6.4–9.6) times in width of rostrum at nostrils; located distinctly forward of level of anterior margin of eye; distance from anterior nostrils to symphysis of upper jaw 1.3 (1.2–1.5) times internarial space, distance from barbel origin to anterior nostrils 10.4 (8.5–10.5)% TL. Anterior nasal flaps well developed, leaf-like, extended ventrally beyond nostrils; incurrent and excurrent apertures surrounded by pronounced marginal lobes; no nasoral or circumnarial grooves; no dermal lobes (Fig 5). Lateral trunk dermal denticles densely set and overlapping, with flat, tricuspidate crowns (Fig 8). The lateral cusps are rather weakly pronounced but situated quite far anteriorly so that the median cusp is not much longer than the lateral cusps. The median ridge is strongly pronounced and reaches the tip of the median cusp. The lateral ridges are less pronounced and do not reach the tips of the lateral cusps. The surface of the denticles is only weakly structured by reticulations very close to base. No sexual dimorphism detectable in the morphology of the trunk dermal denticles. Dermal denticles on rostrum fan-shaped, with an obtusely angled, weakly pronounced median cusp and no lateral cusps but with 6–7 strongly pronounced ridges (Fig 9). The surface of the rostral dermal denticles is only weakly structured by reticulations very close to base (Fig 9a–9c). Pectoral fins large, anterior margin weakly convex, 11.4 (10.3–12.2)% TL and 1.5 (1.4–2.0) times inner margin; apex narrowly rounded; posterior margin weakly concave, directed across horizontal axis at about origin of first dorsal fin; inner margin convex and strongly notched basally; free rear tip angular (Figs 3 and 10a). Pelvic fins moderately large, anterior margin almost straight to slightly convex, 6.5 (5.3–6.7)% TL, 1.6 (1.6–1.9) times in first dorsal-fin anterior margin, and 1.5 (1.3–1.7) times in second dorsal-fin anterior margin; apex narrowly rounded; posterior margin concave; inner margin weakly convex and slightly notched basally; free rear tip broadly rounded; origin distinctly posterior to level free tip of first dorsal fin and well forward of level second dorsal fin origin (Fig 10a). First dorsal fin broad, semifalcate, anterior margin slightly convex; apex narrowly rounded; posterior margin slanting posteroventrally, slightly convex distally, strongly concave in basal three quarters; inner margin straight, free rear tip narrowly pointed; origin about opposite pectoral-fin free rear tips; insertion and free rear tip clearly anterior to level pelvic-fin origins (Fig 10a). Second dorsal fin somewhat smaller than first but of similar shape, anterior margin weakly convex, apex very narrowly rounded; posterior margin weakly convex distally, strongly concave near basal three quarters; inner margin straight, free rear tip narrowly pointed; origin clearly behind level pelvic insertions; interdorsal space 1.4 (1.3–1.7) times first dorsal-fin length, 1.7 (1.3–1.9) times dorsal–caudal space; second dorsal-fin inner margin 1.0 (0.7–1.2) times subterminal caudal-fin margin (Fig 10b). Caudal fin short, dorsal margin slightly convex, length 18.8 (17.1–19.9)% TL, 1.1 (0.9–1.3) times in pelvic–caudal space and 5.1 (3.9–7.9) times terminal caudal margin; lower post-ventral lobe absent, upper post-ventral margin slightly convex; terminal lobe well developed, caudal terminal margin slightly concave, apices angular (Fig 10b). Ventral origin of caudal fin situated anteriorly due to low anterior fin ridge (Fig 10b). Clasper morphology: Fig 11 provides photographs of the claspers of adult male SAIAB 84096. The claspers of adult males extend posteriorly to clearly posterior to level of pelvic-fin free rear tips. Clasper shaft flattened rod-shaped. Glans broad and flattened, with long, straight and thorn-like spur. Due to the fragile condition of the specimen, it was not possible to open one of the claspers for further examination. Cranium: five anterior-most basiventral cartilages laterally expanded, with curved, dorsally reflected margins. Chondrocranium and cranial nerves highly modified to accomodate the elongated rostrum. Foramen magnum surrounded by crescent-shaped occipital condyles. Dorsal fenestra of the precerebral fossa teardrop-shaped, with posterior notch (Fig 12a). Skeletal meristics (from radiographs): monospondylous trunk vertebral centra: 57 (52–56); diplospondylous precaudal centra: 49 (48–56); total precaudal centra: 106 (101–110); caudal centra: 54 (47–54); total centra: 160 (151–164). Coloration. Fresh, prior to preservation (paratypes SAIAB 84039 and SAIAB 84096; Fig 13): ground color pale (SAIAB 84096) to light brown (SAIAB 84039) dorsally with two thin yellowish longitudinal stripes (hardly detectable in paratype SAIAB 84096); uniform white ventrally; fins translucent dusky, upper post, Published as part of Weigmann, Simon, Gon, Ofer, Leeney, Ruth H., Barrowclift, Ellen, Berggren, Per, Jiddawi, Narriman & Temple, Andrew J., 2020, Revision of the sixgill sawsharks, genus Pliotrema (Chondrichthyes, Pristiophoriformes), with descriptions of two new species and a redescription of P. warreni Regan, pp. 1-56 in PLOS ONE 15 (3) on pages 5-18, DOI: 10.1371/journal.pone.0228791, http://zenodo.org/record/7415225, {"references":["26. Seret B. Halaelurus clevai, sp. n., a new species of catshark (Scyliorhinidae) from off Madagascar, with remarks on the taxonomic status of the genera Halaelurus Gill & Galeus Rafinesque. J L B Smith Inst Ichthyol Spec Publ. 1987; 44: 1 - 27.","27. Compagno LJV, Ebert DA, Cowley PD. Distribution of offshore demersal cartilaginous fishes (Class Chondrichthyes) of the west coast of southern Africa, with notes on their systematics. A Afr J Mar Sci. 1991; 11 (1): 43 - 139. https: // doi. org / 10.2989 / 025776191784287664"]}