Morphology Data of Betta falx
Identification keys
Main Ref. Tan, H.H. and M. Kottelat, 1998
Appearance refers to
Bones in OsteoBase

Sex attributes

Specialized organs
Different appearance
Different colors

Descriptive characteristics of juvenile and adult

Striking features
Body shape lateral fusiform / normal
Cross section
Dorsal head profile
Type of eyes
Type of mouth/snout
Position of mouth
Type of scales

This species is closely related to Betta picta from Java where it can be distinguished in the following characters: fewer dorsal fin rays (mode 8 vs. 9); fewer lateral scales (mode 27 vs. 28); dorsal fin origin above 11-12th lateral scale (vs. 12-14th); anal fin origin below modal 6th lateral scale (vs. 7th); fewer predorsal scales (mode 19 vs. 20); slightly greater anal-fin base length (46.5-50.3% SL vs. 42.6-48.4); anal and caudal fins with reddish distal band in live male (vs. bluish); iridescent greenish-blue opercle scales (vs. yellow-gold); in preserved specimens, male with distinct dorsal transverse bars (vs. faint); male with distinct dark anal distal margin wide (vs. narrow); male without elongated median caudal fin rays (vs. presence); female with distinct caudal transverse bars (vs. very faint or absent); dorsal head view narrow (vs. broad); thick preorbital black stripe (vs. narrow); and the distance between posterior part of anal fin to lower part of caudal narrow (vs. wide) (Ref. 56386).

Ease of Identification

Meristic characteristics of Betta falx

Lateral Lines Interrupted: No
Scales on lateral line
Pored lateral line scales
Scales in lateral series
Scale rows above lateral line
Scale rows below lateral line
Scales around caudal peduncle
Gill clefts (sharks/rays only)
Gill rakers
on lower limb
on upper limb


Dorsal fin(s)

Fins number 1
Finlets No. Dorsal   
Spines total 1 - 2
Soft-rays total 7 - 8
Adipose fin absent

Caudal fin

Attributes other (see remark); more or less normal

Anal fin(s)

Fins number 1
Spines total 2 - 2
Soft-rays total 19 - 21

Paired fins

Pectoral Attributes  more or less normal
Spines     1
Soft-rays   12 - 12
Pelvics Attributes  more or less normal
Position    before origin of D1
Spines     1
Soft-rays   4 - 4
Main Ref. (e.g. 9948)
Glossary ( e.g. cephalopods )
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