Kyphosus bigibbus, the brown chub, grey drummer, darkfin drummer, insular rudderfish, grey chub, grey sea chub, southern drummer or topsail drummer is a species of marine ray-finned fish, a sea chub from the family Kyphosidae. It is a herbivorous species which is found in subtropical and tropical seas worldwide. Description Kyphosus bigibbus has an oval shaped body which is laterally compressed with a small head, a pointed snout and a slightly bulging forehead. The mouth is small and when closed the maxilla are hidden beneath the preorbital bones. The mouth is terminal and is almost oblique. The teeth are fixed and incisiform with their bases positioned horizontally in mouth, they have rounded crowns and have a curved, J shape. There are teeth are found on the centre of the roof of the mouth and on the tongue. The dorsal fin is a similar height along its length The anterior part of the dorsal fin has 11 spines which fold down into a scaled furrow while the posterior part contains 10-12 rays. The anal fin has three spines and 10-12 moderately long soft rays and is reasonably long at its base. The symmetrical caudal fin is forked but not extremely so. The lateral line has 61-76 scales of which 51-60 are pored. The colour varies from uniform grey to brownish, silvery ventrally, bronze to greenish tint dorsally. There are very indistinct dark stripes on the body and there are usually whitish streaks on the cheek. The dorsal and anal fins are frequently dark with black margins on their soft-rayed parts. There is sometimes a dark patch visible on the lower posterior angle of the base of the pectoral fin. The caudal fin is usually dark. There are infrequent records of completely yellow individuals and very rate records of albinos.<ref name = FofA>{{cite web | author = Bray, D.J. | year = 2019 | title = Kyphosus bigibbus | work = Fishes of Australia | access-date = 26 April 2020 | url = http://136.154.202.208/home/species/1300 | publisher = Museums Victoria}}</ref> The maximum total length of this species is and it has been weighed at . DistributionKyphosus bigibbus has a wide distribution in the Indian, Pacific and Atlantic Oceans. In the Indo-Pacific it has been recorded off Western Australia as far south as Rottnest Island, in eastern Australia it is found from southern Queensland and New South Wales as far south as Montague Island,