Taxonomy of Finfish (1+2)

Identification of Skate families

Visit nearby fish landingcentre or a fish market.

Collect skates/ rays (order :Rajiformes) based on the following characters.

• ventral gill openings
• dorsoventrally depressed
• pectoral fins
• enlarged and fused to the sides of the head over the gillopenings
  
• eyes and well-developed spiracles on the dorsal surface ofthe head mouth and nostrils are ventral
• an anal fin is absent
  

Identify the following families based on the given characters.

RHINIDAE

• Free rear tips of pectoral fins anterior to pelvic-finorigins;
• Two dorsal fins large and strongly falcate; origin offirst dorsal over or in front of pelvics.
• Caudal fin large,shark-like, and asymmetrical with a strong ventral lobe
• Pectoral fins small, originatingin front of mouth

TORPEDINIDAE- Electric rays

• Disc truncate or emarginate anteriorly;
• transversely elliptical, not pear-shaped;
• tail not greatly reduced,
• caudal fin much higher than dorsal fin
• Jaws extremely slender
• no labial cartilage’
• rostrum absent

NARCINIDAE

• Snout with a broad, stiff, shovel-shaped rostralcartilage, readily felt by palpitation of the snout;
• a deep groove around mouth ;
• teeth extending onto outer surfaces of upper and lowerjaws in most species
• 2 dorsal fins present
• Jaws stout strong labial cartilage

RHINOBATIDAE- Guitar fish

• Disc narrow and wedge-shaped anteriorly;
• midback and tail with a row of small and often bluntthorns, and with a few additional thorns often present on scapular area (=shoulder region)
• First dorsal fin origin behind pelvics.

GYMNURIDAE - Butterfly rays

• Disc broad and laterally expanded, rhomboidal and morethan 1.5 times as broad as long)
• Dorsal fin and tail spin present or absent
• short whip-like tails about 0.5 to 0.9 times disclength
• snout short

DASYATIDAE

• Disc less than 1.3 times as broad as long
• Caudal fin absent or reduced to dorsal and ventrallongitudinal folds on midline of tail;
• No caudal fin
• Tail more or less elongated and whip-like with stingingspine
  

MOBULIDAE

• Snout formed into prehensile, elongated, bilobate cephalicfins, laterally based on head;
• mouth very large, jaws weak and transversely expanded,
• with very small cuspidate or hexagonal teeth; gills withfilter plates

Myliobatidae- eagle ray

• Head elevated above the disc
• Eyes and spiracles lateral on head
• gill opening about length of eye to much longer
• tail much longer than disc Pectoral fin absent
• Anterior face of cranium nearly straight
• subrostral fin not incised.
• Single row of plate like teeth on upper jay.

Rhinopteridae

• Rostral fin bilobate and broadly notched medially;
• forehead expanded anteriorly and forming a ledge over baseof rostral fins, its anterior projection with a broad medial notch;
• 3 medial rows of expanded plate-like teeth in each jaw,usually with 2 or 3 rows of smaller hexagonal teeth on each side of them
• Subrostral fin incised (bilobed)
• broad, rhomboidal, wing-like pectoral disc
• Tail slender and whip-like

Rajidae

• Species with a stout rostral cartilage and hard snout
• basihyal cartilage without lateral projections;scapulocoracoid without anterior bridge;
• Caudal fin moderately well developed
• tail extremely slender