Diagnosis: Body moderately deep, its depth about 28-37% of standard length; scutes keeled, 1 or 2 before base of first pectoral fin ray, 13-16 pre-pelvic and 5-9 post-pelvic scutes; snout rounded; lower jaw not or slightly projecting, with small teeth limited to anterior part; pre-maxilla lacking a medial notch and with 32-40 small conical teeth directed inwards; maxilla blade slender, more than 5 times as long as deep, lower edge bordered with minute conical teeth; posterior supra-maxilla about as long as maxilla blade, its shaft as long as its blade; lower gillrakers 14-18 (Ref. 46514, 47399). Also characterized by 35-39 scales in a longitudinal series and anal fin with 20-25 rays (Ref. 46514, 47399). Closely related to Microthrissa royauxi and distinguished from this species by the shape of the pre-maxillary, the medial notch as found in M. royauxi is absent in M. whiteheadi, and the latter also has 32-40 pre-maxilla teeth vs. 16-26 in M. royauxi (Ref. 46514). It is distinguished from Microthrissa minuta by a higher number of teeth on the pre-maxilla, 32-40 vs. 12-30 in M. minuta; and additionally by a lower number of lower gillrakers, 14-18 vs. 18-22, a higher number of anal fin rays, 20-25 vs. 18-21, and a higher number of pre-pelvic scutes, 13-16 vs. 11-12 (Ref. 46514, 47399).

Description: Head relatively small, about 1/4 of standard length (Ref. 46514). Eye about 1/3 of head length, longer than snout length; snout rounded; premaxillary bones moderately flattened, lacking a medial notch; 32-40 small conical backward pointed premaxillary teeth; one group of 3-8 larger conical teeth on each side of vomer; no teeth on the tongue; maxilla reaching back to anterior eye margin; its length 5.5-7.8 times as long as deep, with the lower edge bordered with minute conical teeth, 13-29; supramaxilla, 2nd or posterior, length 1.8-2.1 times in maxillary length, about as long as maxilla blade; anterior supramaxilla shaft about as long as its blade; dentary with sharp backward pointed conical teeth at its symphysis; 5-6 branchiostegal rays (Ref. 46514, 47399). With 22-29 long and slender gillrakers on the complete first branchial arch, 14-18 on the lower part, generally as long as or longer than the corresponding gill filaments (Ref. 46514, 47399). Body compressed, moderately deep, maximum body depth about 1/3 of standard length; belly keeled; 1-2 prepelvic scutes in front of first pectoral finray; the first 3-4 prepelvic scutes lacking ascending lateral arms; 13-16 prepelvic scutes with distinct keel; 5-9 postpelvic scutes with a spiny keel (Ref. 46514, 47399). Dorsal fin origin closer to tip of snout than to caudal fin origin; 11-14 dorsal finrays; last dorsal finray at about the same level as last postpelvic scute; pelvic fin inserted at about the same distance from the tip of the snout as dorsal fin, 8 pelvic finrays; pelvic fins nearly reaching anal fin; 20-25 anal finrays; pectoral fin reaching base of pelvic fins; 12-14 pectoral finrays (Ref. 46514). Cycloid scales: 35-39 transparant, oval-shaped scales in a longitudinal series; a few continuous vertical striae and several incomplete striae on each scale (Ref. 46514, 47399). Generally 9-10 predorsal bones; total vertebrae 39-40; 18-19 abdominal and 20-21 caudal vertebrae (Ref. 46514, 47399).

Colouration: In alcohol, preserved specimens brownish-yellow, with eye, middle of flanks and ventral region often silvery; with a silvery longitudinal band along the flanks, showing a high concentration of melanophores on the caudal part; base of each caudal lobe blackish (Ref. 46514, 47399).