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An introduction to the classification of elasmobranchs

17 Rekha J. Nair and P.U Zacharia Central Marine Research Institute, Kochi-682 018

Introduction eyed, stomachless, deep- creatures that possess an upper which is fused to its cranium (unlike in ). The term Elasmobranchs or chondrichthyans refers to the The great majority of the commercially important of group of marine organisms with a made of . chondrichthyans are elasmobranchs. The latter are named They include sharks, skates, rays and . These for their plated which communicate to the exterior by organisms are characterised by and differ from their sister 5–7 openings. In total, there are about 869+ extant species group of bony in the characteristics like cartilaginous of elasmobranchs, with about 400+ of those being sharks skeleton, absence of swim bladders and presence of five and the rest skates and rays. is also perhaps to seven pairs of naked slits that are not covered by an infamously known for its constant, yet essential, revisions . The chondrichthyans which are placed in of the relationships and identity of different organisms. are grouped into two main subdivisions Classification of elasmobranchs certainly does not evade this Holocephalii (Chimaeras or ratfishes and elephant fishes) process, and species are sometimes lumped in with other with three families and approximately 37 species inhabiting species, or renamed, or assigned to different families and deep cool waters; and the Elasmobranchii, which is a large, other taxonomic groupings. It is certain, however, that such diverse group (sharks, skates and rays) with representatives revisions will clarify our view of the taxonomy and phylogeny in all types of environments, from fresh waters to the bottom (evolutionary relationships) of elasmobranchs, leading to a of marine trenches and from polar regions to warm tropical better understanding of how these creatures evolved. waters with over 950 different species. Chimaeras are big-

Fig. 1. Main parts of an Elasmobranch

Summer school on recent advances in marine biodiversiy conservation and management 118 Rekha J. Nair and P.U Zacharia

Fig. 2. Fig. 3. of sharkw (Source: FAO Species Catalogue No.8, vol. 1)

Class (cartilaginous • Labial furrows when present reduced or absent on lower fishes) jaw Subclass (chimaeras and relatives) • Teeth without enlarged anterior or posterior teeth without Chimaeriformes (chimaeras or silver sharks) a gap or small intermediate teeth between anterior and Subclass (modern sharks and batoids) lateral teeth in the upper jaw Cohort Selachii (modern sharks) • 2 families • Family Chlamydoselachidae ( ) Superorder Squalomorphii (Squalomorph • Family Hexanchidae (Genera , ) sharks) Order (cow and frilled sharks) Order - dogfish sharks Order Squaliformes (dogfish sharks) • Two dorsal , with or without spines Order Squatiniformes (angel sharks) • Anal absent Order Pristiophoriformes () • Five gill slits • Spiracles present Superorder Galeomorphii (Galeomorph • Nictiating lower eyelid absent sharks) • Lateral-line canal closed Order Heterodontiformes (bullhead sharks) • 7 families - Echinorhinidae*, Oxynotidae, , Order ( sharks) , , , Order Orectolobiformes (carpet sharks) • As per Nelson (2006), Family Echinorhinidae is placed in Order (ground sharks) a separate order Echinirhiniformes Cohort (batoids) Order Torpediniformes (electric rays) Order Squatiniformes – angel sharks. Order Pristiformes () • Marine, temperate to tropical, found along continental Order (skates and ) shelves and upper slopes Order (stingrays) • Atlantic, and Pacific • Body ray like Order Hexanchiformes (cow and frilled • dorsal sharks) • Two spineless dorsal fins • One , without spine,trunk cylindrical, • No anal fin slightly depressed • Five gill openings • Anal fin present • large • Six or seven gill slits present on sides of head, • Mouth almost terminal posteriormost in front of pectoral fin origins • Nostrils terminal with barbels on anterior margin. • Eyes without nictitating fold Maximum length up to 2 m. • Spiracle present but small, well behind eye • Family Squatinidae– angel sharks. • Nostrils without barbels • Nasoral grooves separate from mouth Order Pristiophoriformes– saw sharks. • Mouth large, arched and elongated, extending well • Marine (rarely in ), temperate to tropical, behind eyes continental and insular shelves and slopes

16th February – 8th March 2015 Central Marine Fisheries Research Institute 119 An introduction to the classification of elasmobranchs

Fig. 4 Measurements used for sharks (Source: FAO Species Catalogue No.8, vol. 1)

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• Western Atlantic in region of Bahamas, Florida, and ➢ Head nearly as long as trunk Cuba, Southwestern Indian off , and Western ➢ Snout with a greatly elongated with flattened blade like Pacific from Southern to . projections • Body shark like ➢ very protusible • Snout produced in along flat blade with teeth on each ➢ Gill openings short side ➢ Peduncle pit absent • One pair of long barbels ➢ Eye small • No dorsal fin spines ➢ Caudal fin long but ventral lobe not developed • Anal fin absent ➢ One genus, one species- owstoni, Goblin • Spiracles large shark

∗Family Pristiophoridae - saw sharks. Family Pseudocarchariidae - sharks Superorder Galeomorphii (Galeomorph sharks) ➢ Eyes exceptionally large ➢ Mouth large, parabolic, ventral on head, jaws protrusible Order Heterodontiformes (bullhead ➢ Teeth large, anterior ones narrow, laterals compressed sharks) blade like • Two dorsal fins, each with a spine ➢ Gill openings extending onto dorsal surface of head • Anal fin present ➢ Pectoral fins small, pelvic large • Five gill slits ➢ Caudal peduncle with upper and lower precaudal pits • Spiracle present but small and with low lateral keel • Snout pig like ➢ One genus with one species- Pseudocarcharias • Nictitating fold absent kamoharai, • Oviparous • One family - Heterodontidae Family Megachasmidae – megamouth • 1genus Heterodontus, with eight species sharks ➢ Head elongated, about length of trunk Order Lamniformes – mackerel sharks ➢ Mouth very large, terminal • Head conical, not expanded laterally ➢ Snout short and broadly rounded • Eyes usually on sides of head ➢ Gill opening moderately long but not extending onto • Nictitating eyelids, barbels absent dorsal surface of head last two gill slits over pectoral fin • Snout very short base • Spiracles usually present ➢ Teeth small, in numerous rows • Five gill slits, last two above pectoral fin origin ➢ One genus with one species pelagios- • Two dorsal fins, without spines • Anal fin present • 7 families with 10 genera and 15 species Family Alopiidae – thresher sharks * Family Odontaspididae - Tiger Sharks ➢ Upper lobe of caudal fin long and curving, about as long * Family Pseudocarchariidae - Crocodile Sharks as rest of shark * Family Alopiidae – Thresher Sharks ➢ Last two gill openings above pectoral fin base * Family Cetorhinidae– Basking Sharks ➢ Gill openings short * Family - Mackerel Sharks ➢ Mouth small * Family - Goblin Sharks ➢ Pectoral fins long and narrow * Family Megachasmidae – Megamouth Sharks ➢ One genus, Alopias, with three species

Family Odontaspididae - sand tiger sharks Alopias superciliosus ➢ Eyes relatively small ∗ Head nearly flat between eyes, with a deep horizontal ➢ Gill openings all in front of pectoral fin, relatively large groove on nape on each side above gills but not extending onto dorsal surface of head ∗ Eyes very large, with orbits expanded onto dorsal surface ➢ Caudal peduncle with an upper precaudal pit, without a of head lateral keel ➢ 2 genera- and , with three species Alopias pelagicus ➢ Carcharias taurus-, Odontaspis ferox, Odontaspis ∗ Head narrow, forehead nearly straight noronhai ∗ Eyes smaller, with orbits not expanded onto dorsal surface of head Family Mitsukurinidae - goblin sharks ∗ Pectoral fins nearly straight and broad-tipped

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∗ Sides above pectoral bases dark

Alopias vulpinus ∗ Head broad, snout shorter ∗ Eyes smaller, with orbits not expanded onto dorsal surface of head ∗ Forehead strongly arched ∗ Sides above pectoral-fin bases marked with a white patch

Family Cetorhinidae– basking sharks ➢ Gill openings exceptionally large, extending almost to the top of the head; ➢ Teeth small and numerous ➢ Mouth large • Spiracles present ➢ Eye small • Teeth very small, numerous, with a single medial cusp ➢ Gill rakers elongate and usually one or more cusplets on each side near the ➢ One genus with one species Cetorhinus maximus, basking center of mouth shark • Intestine with • Lateral keels or precaudal pits absent on caudal peduncle Family Lamnidae - mackerel sharks • 16 genera- of which 7 genera are forms found ➢ Large sharks with pointed snouts and spindle-shaped in Indian bodies , , , , ➢ Mouth large with blade like teeth, 40 rows in each jaw , , , ➢ Gill slits long ending far lateral to mid dorsal surface Holohalaelurus, , Scyliorhinus ➢ Gill rakers absent ➢ Caudal fin nearly symmetrical and caudal peduncle with Family Proscyllidae– finback sharks strong lateral keel and precaudal pits. • Nictitating eyelids rudimentary ➢ Three genera, , and , with five • Spiracles large species • Posterior teeth comb like • Labial furrows short or absent Genus Isurus • Three genera, Ctenacis (1), (3), and • Cusplets absent on teeth (1), with five species • Origin of first dorsal fin over or behind rear tips of pectoral fins Family – false cat sharks • Origin of second dorsal fin well in front of anal-fin origin • First dorsal fin low, elongate, and keel –like • Secondary keel absent on caudal fin • Nictating eyelids rudimentary • 2 species - Isurus oxyrinchus and Isurus paucus • Spiracles large • rows exceptionally numerous Family Scyliorhinidae - cat sharks • Posterior teeth comblike • Small sharks , body slender and elongated • Two monotypic genera, and Pseudotriakis • 5 gill slits, the last two posterior to pectoral fin origins • First dorsal fin base opposite or behind base Family Leptochariidae– barbeled hound • Nictitating eyelids rudimentary sharks

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• Labial furrows very long in size • Anterior nasal flaps formed into slender barbels ➢ Origin of anal fin behind origin of second dorsal fin. • Nictitating eyelids internal • Spiracles small Family Parascyllidae – collared carpet • Intestine with spiral valve sharks • One species, Leptocharias smithii, Barbeled hound shark • Marine, tropical to temperate, continental to slopes • Spiracles minute Family Triakidae– hound sharks • Anal fin origin well in front of origin of second dorsal-fin • Labial furrows moderately long • Short caudal fin • Anterior nasal flaps usually not slender or like • Caudal fin origin behind anal fin base at a distance • Spiracles present greater than anal fin base • Intestine with spiral valve • Maximum length 3.3m, in Cirrhoscyllium expolitum , most • Nine genera with at least 38 species under 9 m Two genera, Cirrhoscyllium and , with seven species. Family – weasel sharks • Dorsal fin margin undulated 1.Genus Cirrhoscyllium • Precaudal pit present ➢ Snout long, narrow pointed • internal ➢ A pair of barbels on throat • Spiracles small ➢ Head broad and flattened • Labial furrows moderately long ➢ Eyes oval • Intestine with spiral valve ➢ Spiracles large. • Four genera, (1), (1), ➢ Origin of anal fin well behind second dorsal origin, (1), and (4), with seven species separated from lower caudal origin by space less than its base length Order Orectolobiformes - carpet sharks ➢ Pectoral fins thin, large • Two dorsal fins, without spines ➢ Dark saddles present on body. • Anal fin present, broad, last two to four above or behind pectoral fin origin 2.Genus Parascyllium • Five narrow gill slits ➢ Snout short, thick, and broadly rounded • Nictitating eyelids absent ➢ Pectoral fins thick, muscular, and rather small • Barbels and nasoral grooves present ➢ No barbels on throat • Spiracles present ➢ Eyes more elongated and slit-like • Mouth short, ends in front of eyes ➢ Body with spots, in some with collar • 7 families, 14 genera and 32 species ∗ Family Parascyllidae Family Brachaeluridae - blind sharks ∗ Family Brachaeluridae • Marine, tropical to temperate , primarily ∗ Family Orectolobidae coastal ∗ Family • Spiracles large ∗ Family Stegostomatidae • Nasal barbels very long ∗ Family • Eyes dorsolateral ∗ Family Rhincodontidae • Vertebrae 117-142. • Maximum length about 1.2m, reported in Species reported from Indian waters waddi. ∗ Stegostoma fasciatum (Hermann, 1783) • Two monotypic extant genera, Brachaelurus and ∗ ferrugineus (Lesson, 1830) Heteroscyllium ∗ Rhincodon typus Smith, 1828 Family Rhincodontidae (Rhiniodontidae) - Suborder Parascyllioidei shark ➢ Spiracles minute, without gill filaments; fifth gill opening • Broad, flat head, truncated snout large • Mouth large, terminal ➢ Origin of anal fin well in front of origin of second dorsal • Caudal peduncle with strong lateral keels. fin. • Caudal fin with a strong ventral lobe, but without a strong terminal lobe and subterminal notch Suborder Orectoloboidei • Teeth reduced, numerous internal gill slits inside mouth ➢ Spiracles moderate to large, with gill filaments; fifth gill cavity with filter screens. opening moderate • Gill openings very large, fifth well separated from

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fourth griseum - • Gill rakers elongate Chiloscyllium hasselti • One species Rhincodon typus, 2. Genus Family Orectolobidae – ➢ Nostrils terminal on snout • Marine, tropical to warm temperate, continental shelf ➢ Preoral snout short • Head and body depressed; flattened, variegated ➢ Mouth closer to snout tip than eyes • Mouth nearly terminal; skin flaps present ➢ Eyes and supraorbital ridges prominently elevated • Nostrils with very long pointed or branched barbels ➢ Large dark or spots on sides of body above pectoral • Spiracles large, gill slits small fins, or a black hood on head • Enlarged fang like teeth at symphysis of upper and lower ➢ 5 species recognised – jaws Hemiscyllium strahani • Maximum length about 3.2m, reported in Hemiscyllium trispeculare maculates Hemiscyllium freycineti • Three genera, Eucrossorhius, Orectolobus and Sutorectus, Hemiscyllium ocellatum with six species Hemiscyllium hallstromi

Family Hemiscylliidae - bamboo sharks Family Stegostomatidae - zebra sharks • Marine , tropical and subtropical, continental shelves • Species moderate in size • Small, slender sharks, nasal barbels short; spiracles large • Eyes placed lateral on head without movable upper • Dorsal fins two, spineless eyelids • Anal fin low and rounded, origin well behind origin of • Spiracles large second dorsal fin • Nostrils with short pointed barbels • Caudal peduncle without lateral keels or precaudal pits • Caudal fin unusually long, almost as long as rest of shark • Vertebrae 151-192 • Caudal peduncle without lateral keels or precaudal pits • Maximum length about 1.0m, recorded in Chiloscyllium • Maximum length possibly 3.5m, usually under 2.5m punctatum and 70 cm in Hemiscyllium ocellatum. • One genus, one species, Stegostoma fasciatum (Hermann, • Two genera, Chiloscyllium and Hemiscyllium with 12 1783). species. Family Ginglymostomatidae – nurse sharks • Spiracles small, behind the eyes • Eyes placed lateral on head in Nebrius • Nostrils with short to moderately long barbels, no lobe and groove around outer edges of nostrils • Circumnarial grooves absent, nasoral grooves present • Fourth and fifth gill slits almost overlapping • Maximum length about 3m, recorded in 1.Genus Chiloscyllium cirratum and Nebrius ferrugineus ➢ Nostrils subterminal on snout • 3 monotypic genera, Ginglymostoma, Nebrius and ➢ Preoral snout long Pseudoginglymostoma ➢ Mouth closer to eyes than snout tip ➢ Eyes and supraorbital ridges hardly elevated 1. Genus Ginglymostoma ➢ 7 species recognised – ➢ Nasal barbels elongate reaching mouth Chiloscyllium indicum ➢ Lower lip trilobate Chiloscyllium plagiosum ➢ Second dorsal and anal fins much smaller than first dorsal Chiloscyllum arabicum -Arabian fin Chiloscyllium punctatum ➢ Eyes and gill openings dorsolateral on head Chiloscyllium burmensis ➢ Teeth neither compressed nor imbricate ➢ Pectoral fins broad and not falcate ➢ One species - Ginglymostoma cirratum

2. Genus Nebrius ➢ Eyes and gill openings lateral on head ➢ Teeth compressed on sides of jaws ➢ Pectoral, dorsal and anal fins angular apically ➢ Pectoral fins narrow and falcate

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➢ One species - Nebrius ferrugineus - Tawny

3. Genus Pseudoginglymostoma ➢ Nasal barbels greatly reduced, not reaching mouth ➢ Lower lip not trilobate ➢ Caudal fin short ➢ One species - Pseudoginglymostoma brevicaudatum

Order Carcharhiniformes - ground sharks

This order includes many of the most ecologically and commercially important species.

Prominent characters are - ➢ 16 genera- of which 7 genera are deep sea forms found • Nictitating eyelids present in • Two dorsal fins without spines Apristurus, Atelomycterus, Aulohalaelurus, Haploble- • Anal fin present pharus, Cephaloscyllium, Scyliorhinus, Poroderma, • Five gill slits, with the last one to three over the pectoral Holohalaelurus, Halaelurus, Scyliorhinus fin • Gill rakers absent Family Carcharhinidae – requiem sharks • Mouth extending behind eyes ➢ Dorsal fin margin undulated, origin ahead of pelvic base. • Includes 8 families, 49 genera, and at least 224 species ➢ Precaudal pit present ➢ Spiracles usually absent ∗ Family Scyliorhinidae ➢ Nictitating eyelids internal ∗ Family ➢ Intestine with scroll valve ∗ Family Pseudotriakidae ➢ 32 species from Western Indian Ocean ∗ Family Leptochariidae ∗ Family Triakidae 1.Genus ∗ Family Hemigaleidae ➢ Small to large sharks with round eyes, internal nictitating ∗ Family Carcharhinidae eyelids, usually no spiracles. ∗ Family Sphyrnidae ➢ Teeth usually blade like with one cusp. ➢ Development usually viviparous with young born fully Family Scyliorhinidae - cat sharks developed. Includes several dangerous species. ➢ Small sharks , body slender and elongated ➢ Carcharhinus hemiodon (Valenciennes, in Müller & Henle, ➢ 5 gill slits, the last two posterior to pectoral fin origins 1839) – -protected under WPA (1972). ➢ First dorsal fin base opposite or behind pelvic fin base ➢ Nictitating eyelids rudimentary 2.Genus: ➢ Spiracles present ➢ Labial furrow long, conspicuous ➢ Teeth very small, numerous, with a single medial cusp ➢ Teeth oblique and narrow-cusped Rhizoprionodon acutus and usually one or more cusplets on each side near the – center of mouth ∗ Distinct line of pores at corners of mouth ➢ Intestine with spiral valve ∗ Teeth narrow, sharply angled and finely serrated ➢ Lateral keels or precaudal pits absent on caudal peduncle ∗ 2nd dorsal fin origin behind anal fin origin

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3. Genus ➢ Free rear tip of first dorsal on a vertical over midbases of ➢ Short blunt snout pelvic fins. ➢ Large mouth ➢ Postventral margin of caudal fin only slightly concave. ➢ Pointed tail, curved serrated teeth, ➢ Raised keels on either side of caudal peduncle 9. Genus Prionace ➢ Dusky bars on body ➢ One species – Galeocerdo cuvier 10. Genus Nasolamia ➢ Snout very narrow 4. Genus Triaenodon: ➢ Nostrils large close-set ➢ Snout very short, broadly rounded ➢ Internarial space 1.3 times nostril width or less ➢ Teeth narrow, smooth-edged cusps with strong cusplets on each side, no serrations 11. Genus Glyphis ➢ First dorsal and caudal fin tips broad white ➢ Cusps of lower teeth protruding when mouth is closed ➢ Second dorsal fin half the height of first dorsal. ➢ Second dorsal fin 1/2 the height of first dorsal. ➢ Precaudal pits longitudinal 5. Genus : ➢ Snout broader, smaller nostrils more widely spaced, ➢ Snout short internarial space 3 times the nostril width ➢ Teeth with narrow unserrated cusps ➢ Glyphis gangeticus – protected under Indian Protection Act (1972) 6. Genus : ➢ Snout long 12. Genus Isogomphodon ➢ Preoral length about equal to mouth width. ➢ Second dorsal fin smaller than first ➢ Upper teeth with broad, triangular, serrated cusps, lowers ➢ Snout triangular dagger-shaped in dorsoventral view, with narrow, smooth cusps while narrow and spearlike laterally ➢ Tooth rows 49 - 56 7. Genus Loxodon: ➢ Labial furrows reduced confined to mouth corners Family Sphyrnidae – hammerhead sharks ➢ Notch present posteriorly on eye ➢ Head with lateral, bladelike expansions ➢ Eyes at its outer edges 8. Genus ➢ Two dorsal fins, first dorsal fin high and pointed, base ➢ Second dorsal fin smaller than first dorsal shorter than caudal fin, anterior to origins of pelvic fins ➢ Head greatly depressed trowel-shaped. ➢ Second dorsal and anal fins much smaller than the first ➢ Pectoral fins triangular in shape dorsal fin ➢ Three species reported from Indian waters

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mokarran (Rüppell, 1837) ∗ Sphyrna lewini (Griffith and Smith, 1834). ∗ Sphyrna zygaena (Linnaeus, 1

Family Proscyllidae – finback cat sharks ➢ Nictitating eyelids rudimentary ➢ Spiracles large ➢ Posterior teeth comb like ➢ Labial furrows short or absent ➢ Posterior teeth on dental bands comb like ➢ Labial furrows very short or absent, when present confined to mouth corners ➢ Three genera, Ctenacis (1), Eridacnis(3), and Proscyllium ➢ Spiracles small (1), with five species ➢ Intestine with spiral valve ➢ One species, Leptocharias smithii, Barbeled hound shark 1. Genus Ctenacis Family Hemigaleidae – weasel sharks 2. Genus Eridacnis ➢ Dorsal fin margin undulated Eridacnis radcliffei Smith, 1913- Pygmy ribbontail ➢ Precaudal pit present ➢ Nictitating membrane internal ➢ One of the smallest living sharks ➢ Spiracles small ➢ Anal fin and two equal-sized, spineless dorsal fins ➢ Labial furrows moderately long ➢ Nictitating eyelids, mouth triangular, ➢ Intestine with spiral valve ➢ Labial furrows rudimentary or absent, ➢ Four genera, Chaenogaleus (1), Hemigaleus (1), ➢ posterior teeth comblike Hemipristis (1) and Paragaleus (4), with seven species

3.Genus Proscyllium Family Triakidae – hound sharks ➢ One of the most species-rich orders of sharks Family Pseudotriakidae – false cat sharks ➢ First dorsal fin originates in front of pelvic fins ➢ Head without laterally expanded blades ➢ Labial furrows moderately long ➢ Eyes elongated and slitlike, nictating eyelids rudimentary ➢ Anterior nasal flaps usually not slender or barbel like ➢ Spiracles large ➢ Spiracles present ➢ Tooth rows exceptionally numerous ➢ Intestine with spiral valve ➢ Posterior teeth comb like ➢ Anal fin smaller than second dorsal and with concave ➢ First dorsal fin low, elongate, and keel –like rear margin ➢ Two monotypic genera, Gollum and Pseudotriakis ➢ Precaudal pits absent ➢ Top edge of caudal fin not undulated Family Leptochariidae – barbeled hound ➢ 9 genera with at least 38 species sharks ➢ Eyes horizontally oval 1.Genus Mustelus ➢ Labial furrows very long • Slender with long, parabolic subangular ➢ Anterior nasal flaps formed into slender barbels snouts, ➢ Nictitating eyelids internal • Eyes dorsolateral, strong subocular ridges,

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• Mouths angular, teeth formed into a pavement, with • Two genera with 22 species cusps and cusplets variably developed • Medial teeth not differentiated from anterolaterals Subfamily Torpedininae ( electric rays ) • Second dorsal fin nearly as large as first • Tail and dorsal and caudal fins well developed • This taxon is ranked as a separate family by some workers 1. Mustelus mosis Hemprich & Ehrenberg, 1899 - Arabian • Genus Torpedo smooth-hound ∗ Head snout short, broad internarial space, Sub family Hypninae ( coffin rays ) ∗ Large eyes, narrow interorbital space, • Tail and dorsal and caudal fins very small. ∗ Upper labial furrows about equal to lowers, • Continental shelf and uppermost slope, off Australia ∗ Low-crowned teeth with weak cusps, ∗ Dorsal fins unfringed, a semifalcate ventral caudal lobe, Family – numbfishes 59 to 81 precaudal centra, • Disc rounded anteriorly; ∗ Heavily hypercalcified head and other . • Jaws stout, strong labial cartilages ∗ This is the only species of Mustelus in most areas where • present it occurs. • Mouth transverse and entirely surrounded by a deep groove or labial folds 2. M. mustelus

3. M. mangloreanses

Order Torpediniformes -electric rays • Powerful electric organs, derived from branchial muscles in head region • Skin soft and loose • Eye small to obsolete • Caudal fin well developed • Dorsal fin 0-2 • Body disc thick and flabby, oval to roundish, snout short, truncate or rounded, skin soft and loose, without armature of dermal denticles or their modifications • Tail section thick, caudal fin well developed • Electric production is largely for feeding and defence. • 2 families ∗ Family – Torpedo Electric Rays ∗ Family Narcinidae – Numbfishes

Family Torpedinidae– torpedo electric rays • Disc truncate or emarginated anteriorly • Jaws extremely slender • No labial cartilages • Shape of disc rounded anteriorly • Rostrum reduced • 9 genera with around 37 species • Mouth arcuate and not entirely surrounded by a deep groove or labial folds The family has 10 recognized genera, with about 43 nominal • Shape of disc truncate or emarginate anteriorly species, of which four genera and five species are considered to be deep–sea inhabitants; three genera and five species occur in the Indian Ocean deep–sea.

Deep sea species occurring in the Indian Ocean

Benthobatis moresbyi Alcock, 1898 -Moresby’s blind

Sub family Narcininae ( Numbfishes) • Deep groove around mouth and lips, jaws long and strongly protractile

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• Rostrum broad species • Usually two dorsal fins • Four genera, (4), Discopge (1), and 1.Genus (17), with 26 species and many undescribed species Pristis zijsron Sub family Narkinae (Sleeper rays) ∗ Long, saw-toothed snout • Shallow grooves around mouth, jaws short and weakly ∗ Gill slits located entirely on white ventral surface protractile ∗ 1st dorsal fin origin is behind the pelvic fin origin • Rostrum narrow; usually a single dorsal fin ∗ 24-28 teeth on each side of saw that are more closely • Five genera, Crassinarke (1), (4), (3), spaced nearer Temera (1) and (2) with 11 species ∗ the saw-tip than near the mouth

Pristis microdon Latham, 1851 ∗ Rostral saw with 14 to 23 pairs of teeth ∗ Rostrum with sides markedly divergent posteriorly ∗ Rostrum broad and stout ∗ Rostral teeth moderately flattened, ∗ Elongated interspace between posterior most 2 rostral teeth ∗ 1 to 2 times space between first 2 rostral teeth ∗ First dorsal fin with origin well anterior to pelvic-fin origins Order Pristiformes– saw fishes ∗ No secondary caudal keel below the main one on the caudal-fin Family pristidae – sawfishes ∗ Caudal fin without a subterminal notch but with a short ➢ Snout produced in a long flat blade with teeth on each ventral lobe side ➢ Barbels absent 2.Genus Anoxypristis ➢ Body somewhat shark like, although the head is depressed Anoxypristis cuspidata (Latham, 1794) ➢ Two distinct dorsal fins and a caudal fin ∗ Rostral saw with 16 to 29 pairs of teeth ➢ Two genera, Anoxypristis and Pristis, with about seven ∗ Posteriormost teeth on rostral saw well anterior to base

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of saw ➢ Caudal fin large, bilobed ∗ Rostral teeth greatly flattened, blade-like, and triangular ➢ Origin of first dorsal over or in front of pelvics ∗ Broad incurrent grooves on underside of snout ➢ Head and anterior part of head broadly rounded, with ∗ Nostrils long, narrow and diagonal deep indentation separating it from pectoral fin origin ∗ A secondary caudal keel below the first one on the ➢ caudal-fin base. ∗ Caudal fin with a shallow subterminal notch and a long, Family Rhynchobatidae - wedge fishes prominent ventral lobe. ➢ Body moderate between sharklike and skatelike ➢ Caudal fin large, bilobed Order Rajiformes – skates ➢ Origin of first dorsal over or infront of pelvics ➢ Caudal fin moderately well developed, reduced , or ➢ Snout and anterior part of head broadly angular and absent; wegde shaped, with shallow indentation separating it ➢ Tail extremely slender ➢ Dorsal fins 0-2 ➢ Most with prickles or thorns on skin, often with a row along midline of back ➢ Claspers long , slender , and depressed distally ➢ Four families, 32 genera, and 285 species ∗ Family Rhinidae - Bowmouth Guitarfishes ∗ Family Rhynchobatidae - Wedge Fishes ∗ Family Rhinobatidae - Guitarfishes ∗ Family Rajidae - Skates from pectoral fin origin ➢ One genus , with four species Family Rhinidae - bowmouth guitarfishes ➢ Body intermediate between sharklike and like Family Rhinobatidae - guitarfishes ➢ Body intermediate between shark like and skate like

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➢ Tail stout, not definitely marked off from body ➢ Two distinct dorsal fins and a caudal fin, the latter not bilobed ➢ Origin of first dorsal behind pelvics ➢ Denticles over body from a row on midline of back ➢ Tail without spine ➢ Snout wedge-shaped and variously prolonged but not as a blade and without lateral teeth ➢ Four genera, (3), Rhinobatos , Trygonorrhina (1), and (3), with 42 species

∗Rhinobatos granulatus Cuvier, 1829 ➢ very small, posteriorly placed in large cranial cavity ➢ Tail with one or two serrate spines ➢ Hexatrygon bickelli Heemstra and Smith, 1980

Super family Urolophoidea

Family Plesiobatidae – deep water stingrays ➢ Nasal curtain incompletely inited, not reaching the mouth FAMILY RAJIDAE - ➢ Maximum length 2.7m

SKATES ➢ Caudal fin moderately well developed, reduced, or absent ➢ Tail extremely slender ∗ Plesiobatis daviesi (Wallace, 1967) ➢ Weak electric organs derived from caudal muscles ➢ Dorsal fins 0-2, most with prickles on skin, often with a Family - round stingrays row along midline of back ➢ Disc less than 1.3 times as broad as long ➢ Tail variable in shape and length with or without armature ➢ Caudal fin small but well developed of prickles, thorns, and spines ➢ Dorsal fin present in some species ➢ Disc not fleshy toward margins ➢ Tail moderately long with a barbed spine ➢ Body mostly firm Superfamily UROTRYGONOIDAE Order Myliobatiformes– stingrays Family - american round Suborder – Myliobatoidei stingrays ➢ Disc not more than 1.3 times as broad as long Family Hexatrygonidae– sixgill stingrays ➢ Tail slender and about as long as disc length, without ➢ Six gill openings and six gill arches dorsal fin with poisonous spines, Caudal fin well ➢ Snout elongate, thin, translucent developed, supported by cartilaginous radials ➢ No supraorbital crests on cranium ➢ Tail broad and thick at base and not whip-like distally ➢ Spiracles large, well behind eyes, with external flap like ➢ Two genera, (6), and (10), with 16 valve species

16th February – 8th March 2015 Central Marine Fisheries Research Institute 131 An introduction to the classification of elasmobranchs

Super family Dasyatoidea ➢ Disc more than 1.5 times as broad as long ➢ Tail distinctly shorter than disc width Family Dasyatidae (Trygonidae )- whiptail ➢ Transverse parts of nasal curtains smooth-edged stingrays ➢ Papillae absent on floor of mouth ➢ Eyes and spiracles on top of head; ➢ Tail short ➢ Head part of disc, anterior margins of pectoral fins ➢ No caudal fin continuous along sides of head ➢ 2 genera, Aetoplatea (2) and Gymnura (least 9), with at ➢ No separate cephalic fins or rostral lobes least 11 species ➢ Disc about 1.3 times as broad as long ➢ Caudal fin absent, tail long very slender to whiplike, Family Myliobatidae – eagle rays ➢ Poisonous spines on tail ➢ Distinct but small dorsal fin present ➢ Most species with one or more long poisonous spines on tail ➢ No caudal fin ➢ Head elevated above disc ➢ Eyes and spiracles lateral on head ➢ Gill openings about length of eye to much longer ➢ Tail much longer than disc ➢ Small dorsal fin ➢ Pectoral fin absent or reduced ➢ Anterior parts of pectoral fins forming 1 fleshy lobe extending below front of head, or this lobe with a more or less deep median notch, thus forming 2 basally connected lobes ➢ Teeth large, flat, and in a few series only ➢ Caudal fin absent ➢ Tail much longer than disc width; Subfamily Myliobatinae ( Eagle rays)- ➢ Transverse parts of nasal curtains with fringed margins ➢ Anterior face of cranium nearly straight ➢ Floor of mouth with several fleshy papillae

Family -river stingrays ➢ Long , median, anteriorly directed process from the pelvic girdle ➢ Angular cartilages present, within hyomandibular- Meckelian ligament ➢ Adaption to freshwater as evidenced by rectal gland

Family Gymnuridae - butterfly rays ➢ Eyes and spiracles on top of head; head part of disc, ➢ Subrostral fin not incised anterior margins of pectoral fins continuous along sides ➢ Four genera, (3), of head; (4), and Pteromylaeus (2) ➢ No separate cephalic fins or rostral lobes ➢ Disc extremely broad Subfamily RHINOPTERINAE (COWNOSE RAYS) ➢ Dorsal fin and tail spines present or absent

Summer school on recent advances in marine biodiversiy conservation and management 132 Rekha J. Nair and P.U Zacharia

➢ Anterior face of cranium concave, subrostral fin incised Family (bilobed) ➢ Anterior subdivisions of pectoral fins forming 2 thin and ➢ One genus , widely separated cephalic fins ➢ Rhinoptera javanica ➢ teeth minute and in bands of many series in 1 or both jaws Subfamily MOBULINAE ( DEVIL RAYS) ➢ japonica, M. kuhlii, M. tarpacana ➢ Members of this family are the only living ➢ Manta birostris, Manta alfredi with three pairs of functional limbs ➢ The cephalic pair assist in feeding and are the anterior Further reading sub division of the pectorals 1. by Joseph S. Nelson ➢ Two genera, Manta and Mobula 2. FAO Species Catalogue, Vol. 4, Part 1 Sharks Of The World, FAO Fisheries Synopsis No. 125, Volume 4, Part 1

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