Diagnosis: Pellonula leonensis is characterised by having the first prepelvic scute being as large as the following ones lacking ascending arms, located behind the pectoral-fin bases; also characteristic are the inward-curving premaxillary teeth (Ref. 2244, 2849, 81269, 81631). It resembles Pellonula vorax, which has larger and straighter teeth, often pointing forward, and scutes before pectoral fin bases (Ref. 188). Absence of large canine teeth in upper jaw distinguishes it from Odaxothrissa and also Cynothrissa; Microthrissa species are deep-bodied and have much more slender maxilla (Ref. 188).
Description: Body slender to moderately deep (Ref. 188, 2244). Lower jaw very slightly projecting, but not prominent; premaxillary teeth relatively fine, curved inward, only the tips usually apparent (Ref. 188, 81269, 81631). Dorsal fin with 13-19 rays, the first dorsal-fin ray slightly in front or behind the insertion of the pelvic fin; anal fin with 16-22 rays; pectoral fin with 11-16 rays; pelvic fin with 8 rays; length of pectoral fin about half of the pectoral-pelvic fin distance (Ref. 2244, 2849, 81269, 81631). Cycloid scales (Ref. 2244): 36-45 scales in longitudinal line; 8-15 prepelvic and 6-9 postpelvic mid-ventral scutes (Ref. 2244, 2849, 81269, 81631).
Colouration: Ground colour in alcohol-preserved specimens variable from yellow-brown to yellow-gray; operculum, ventral region and flanks usually lighter (Ref. 2244, 2849, 81269, 81631). Silver stripe along flank (Ref. 188).