Morphology Data of Hydrolagus alphus
Identification keys
Abnormalities
Main Ref. Quaranta, K.L., D.A. Didier, D.J. Long and D.A. Ebert, 2006
Appearance refers to
Bones in OsteoBase

Sex attributes

Specialized organs
Different appearance
Different colors
Remarks

Descriptive characteristics of juvenile and adult

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

Assigned to the genus Hydrolagus based upon the absence of an anal fin. Hydrolagus alphus is distinguished by being medium in size (average PCL 321 mm) and uniform dark brown in color with a distinct white spot (4%-6% BDL) on the lateral side above the pectoral fins. Paired fins with bluish hue and white margins. The dorsal spine longer than triangular shaped first dorsal fin and extends beyond the origin of the second dorsal fin when depressed. Eyes large (40.8–44.5% HDL) and pectoral fins reaching to or beyond insertion of pelvic fins when depressed. Pelvic claspers small, not extending beyond distal edge of pelvic fin, and divided distally for one half their length with slender fleshy denticulate tips. The base of second dorsal fin is long, deeply depressed and light colored in the center, anterior and posterior regions dark, considerably greater in height than the white middle region (Ref. 57721).

Ease of Identification

Meristic characteristics of Hydrolagus alphus

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
Barbels
Gill clefts (sharks/rays only)
Gill rakers
on lower limb
on upper limb
total
Vertebrae
preanal
total

Fins

Dorsal fin(s)

Attributes
Fins number
Finlets No. Dorsal   
Ventral  
Spines total
Soft-rays total
Adipose fin

Caudal fin

Attributes

Anal fin(s)

Fins number
Spines total
Soft-rays total

Paired fins

Pectoral Attributes  
Spines     
Soft-rays   
Pelvics Attributes  
Position    
Spines     
Soft-rays   
Main Ref. (e.g. 9948)
Glossary ( e.g. cephalopods )
Entered by Busson, Frédéric
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