Urogymnus acanthobothrium Last, White & Kyne, 2016
Mumburarr whipray
Mumburarr whipray

Family:  Dasyatidae (Stingrays), subfamily: Urogymninae
Max. size:  103 cm WD (male/unsexed); 161 cm WD (female)
Environment:  benthopelagic; brackish; marine; depth range 2 - 20 m
Distribution:  Western Pacific: western Australia and Papua New Guinea.
Diagnosis:  This species is distinguished by the following set of characters: elongate disc suboval with the snout tip to axis of maximum width 53% DW; anterior disc margin not truncated, it is almost straight with lateral apices broadly rounded; preorbital snout broadly angular, its angle 114° and with a very small apical lobe; preorbit long, its length 26% TL, 2.1 times interorbital length; orbits are small and protruded slightly; spiracle is very large, 8.6% DW, 1.9 in orbit diameter; internasal distance is 2.0 in prenasal length, 2.8 times nostril length; preoral snout length is 2.6 times mouth width, 2.5 times internarial distance; caudal sting very large with its length more than a 30% DW; mid-scapular denticles are very small and inconspicuous; secondary denticles are very small, rather widely spaced, band delimited but margin not sharply defined, band truncate forward of eye; presence of minute upright tertiary denticles, barely visible; with a low and short-based ventral tail fold; dorsal disc colour is variable, juveniles plain dark greyish brown to yellowish brown, while in adults very finely and faintly mottled greyish white to yellowish brown; its ventral surface is largely white, posterior disc without regular dark margins; tail beyond sting white in young, while in adults it is unknown but possibly paler than anterior tail; propterygial radials 66, 3 times the number of mesopterygial radials; 151 total vertebral segments (excluding synarcual) (Ref. 110274).
Biology:  Juveniles were recorded from lower reaches of rivers at depths of 2.2-8.7 m; salinity 14.6-33.1; turbidity 367->1000 NTU. Subadult specimens were from depths of 10-20 m. An adult female (161.0 cm DW, 174.0 cm disc length) aborted a late embryo which was estimated to be ca. 26.5 cm DW on capture. Juveniles (5) measured 39.o - 67.2 cm DW, 43.0-72.0 cm DL, while a late adolescent male measured 103.0 cm DW, This stingray could be traditionally hunted for food and the caudal sting can be used as a traditional knife. (Ref. 110274).
IUCN Red List Status: Data deficient (DD); Date assessed: 22 April 2021 Ref. (130435)
Threat to humans:  harmless
Country info:  Type locality of Urogymnus acanthobothrium, West Arm of Cambridge Gulf, Western Australia. Juveniles were recorded from the lower reaches of the Wildman and West Alligator Rivers, Northern Territory (NT), and the lower Ord River and West Arm of Cambridge Gulf, Western Australia (Ref. 110274).


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