Morphology Data of Microthrissa royauxi
Identification keys
Main Ref. Whitehead, P.J.P., 1985
Appearance refers to
Bones in OsteoBase

Sex attributes

Specialized organs no special organs
Different appearance males alike females
Different colors males alike females

Descriptive characteristics of juvenile and adult

Striking features none
Body shape lateral fusiform / normal
Cross section compressed
Dorsal head profile more or less straight
Type of eyes more or less normal
Type of mouth/snout more or less normal
Position of mouth terminal
Type of scales cycloid scales

Diagnosis: Body rather deep, its depth about 30-37% of standard length; scutes strongly keeled, 1 or 3 before base of first pectoral fin ray, 13-16 pre-pelvic and 3-7 post-pelvic scutes; snout fairly pointed; lower jaw not or slightly projecting, included in upper when mouth closed, with small teeth limited to anterior part; pre-maxilla with medial notch and 16-26 small conical teeth directed outwards; maxilla blade slender, more than 3 times as long as deep, upper edge with a ridge flared outward; posterior supra-maxilla small, spatulate, shaft as long as or longer than blade; lower gillrakers 14-17 (Ref. 188, 47399). Also characterized by 34-41 scales in a longitudinal series and anal fin with 22-27 rays (Ref. 188, 47399). It resembles Microthrissa minuta, which has more lower gillrakers but fewer anal fin rays, 18-22 and 18-21 respectively (Ref. 188, 47399). It is distinguished from Microthrissa whiteheadi by the presence of a medial notch in pre-maxilla and a lower number of teeth on the pre-maxilla, 16-26 vs. 32-40 (Ref. 46514).

Description: Depth of body 3-3.5 times in total length, length of head 3.5-4 times in total length (Ref. 1878). Snout rounded, shorter than diameter of eye, which is 2.3-3.3 times in length of head and a little greater than interorbital width (Ref. 1878, 41594). Lower jaw not or slightly projecting; maxillary rather narrow, extending scarcely beyond anterior border of eye; premaxilla with 16-26 conical teeth directed outward; maxillary with 8-30 small conical teeth (Ref. 28136, 47399). Gillrakers long and slender, about 14-17 on lower part of anterior arch, 20-36 total gillrakers (Ref. 188, 1878, 47399). Dorsal fin base slightly behind origin of pelvic fins, last ray above first of anal fin, longest ray 4/5 length of head; dorsal fin rays 11-14; anal fin rays 22-27; pectoral fin rays 12-15, pectoral fin rather more than 2/3 length of head, nearly reaching ventral; pelvic fin rays 8; caudal deeply forked, with pointed lobes (Ref. 188, 1878, 47399). Caudal peduncle nearly as long as deep, its depth 10-12% of standard length (Ref. 1878, 93833). Cycloid scales; 34-41 scales in longitudinal series; 12 in transverse series (Ref. 188, 1878, 47399). Scutes strongly keeled; 13-16 prepelvic scutes,with 1-3 scutes before base of pectoral fin, first 3-4 scutes without ascending arms; 3-7 postpelvic scutes (Ref. 188, 1878, 47399, 93833). Number of vertebrae 37-41; with 17-19 abdominal vertebrae and 21-23 caudal vertebrae (Ref. 47399).

Colouration: Preserved colouration brownish, with a rather indistinct silvery lateral band (Ref. 1878, 47399).

Ease of Identification

Meristic characteristics of Microthrissa royauxi

Lateral Lines Interrupted: No
Scales on lateral line
Pored lateral line scales
Scales in lateral series 34 - 41
Scale rows above lateral line
Scale rows below lateral line
Scales around caudal peduncle
Barbels 0
Gill clefts (sharks/rays only)
Gill rakers
on lower limb 14 - 17
on upper limb
total 20 - 36
total 37 - 41


Dorsal fin(s)

Attributes no striking attributes
Fins number 1
Finlets No. Dorsal   
Spines total 0 - 0
Soft-rays total 11 - 14
Adipose fin absent

Caudal fin

Attributes forked; more or less normal

Anal fin(s)

Fins number 1
Spines total 0 - 0
Soft-rays total 22 - 27

Paired fins

Pectoral Attributes  more or less normal
Spines     0
Soft-rays   12 - 15
Pelvics Attributes  more or less normal
Position    abdominal  before origin of D1
Spines     0
Soft-rays   8 - 8
Main Ref. (e.g. 9948)
Glossary ( e.g. cephalopods )
Entered by Binohlan, Crispina B.
Modified by Boden, Gert
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