Pliotrema annae Weigmann, Gon, Leeney & Temple, 2020
Anna’s sixgill sawshark
photo by Weigmann, S.

Family:  Pristiophoridae (Saw sharks)
Max. size:  98 cm TL (female)
Environment:  demersal; marine; depth range 20 - 35 m
Distribution:  Western Indian Ocean: Zanzibar and probably off Kenya and Somalia.
Diagnosis:  This medium-sized six-gilled sawshark is distinguished by 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; the first dorsal fin originates about opposite pectoral-fin free rear tips; lateral trunk dermal denticles tricuspidate, rather flat and imbricated; monospondylous centra 53-54; precaudal diplospondylous centra 46-49; total vertebral centra 154; generally with a shorter snout, 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; with lower total large lateral rostral tooth and ventral rostral spine counts, and a rostrum that is slightly constricted between barbel origin and nostrils. Similar to P. kajae, with barbels situated about half way from rostral tip to mouth, with prebarbel length about equidistant from barbel origin to symphysis of upper jaw, while in P. warreni, 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. Colouration: 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, especially the caudal and pectoral fins; dorsal rostrum surface with two distinct longitudinal dark stripes, lateral rostral teeth dark-edged (Ref. 122027).
Biology:  Probably occurs in deeper waters during the day but enters shallow water during the night. The specimens were caught directly adjacent to a dropoff along the southern tip of Unguja Island where the water depth descends rapidly from ca.20 m to >200 m (Ref. 122027).
IUCN Red List Status: Data deficient (DD); Date assessed: 20 April 2020 Ref. (124695)
Threat to humans:  harmless
Country info:   

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