This species is distinguished by the following combination of characters: moderate-sized disc, its width at anterior orbit 5.2-7.8 times mouth width; moderately elongate to short tail, its postcloacal length 79-170% of disc length; relatively large eyes with orbit diameter 4.7-8.8 in horizontal snout and 6.7-10.6 in head lengths, respectively; distal portion of tail expanded laterally in specimens exceeding about 28 cm TL (130 mm DW), width of tail near tip 1.3-2.2 times tail width at its midlength; pectoral-fin radials 66-71; moderate-sized pelvic fins, anterior lobe 12.1-18.1% TL; anterior pelvic-fin lobe rather broad-based, width 1.7-3.2 in distance between pelvic-fin origins; caudal fin rudimentary; tooth rows 20-28, in each jaw of adults; with teeth of adult males with greatly elongated conical cusps; 25-31 abdominal vertebral centra; 148-171 total centra; dorsal surface pale pinkish brown, ventral surface uniformly pale (Ref. 75174).
Description: The medium-sized Sinobatis bulbicauda has affinities to the slightly smaller species S. borneensis (South and East China Seas). Based on it description of the adult male holotype, S. borneensis has a filamentous (vs. bulbous) tail and the snout is relatively longer with preorbital length 6.5 times the interorbital length (vs. 3.9-4.8 in adult males and 3.4-5.7 in all types of S. bulbicauda). Although, adult males of the two species are not identical in size, S. borneensis, 31.7 cm TL (vs. 42.9-43.3 cm TL in S. bulbicauda), however, the 2 species are similar enough to ensure that morphometric biases due to ontogenetic variability are minimal (Ref. 75174).