Natural History of Sharks, Skates, and Rays

Phylogeny of Batoidea

MARE 380Dr. Turner

Zoogeographic PatternsSuperorder Batoidea – electric rays, sawfishes, guitarfishes, skates, & stingrays

Range for polar to tropical seas

4 Orders3 Suborders4 Superfamilies13 Families6 Subfamilies79 Genera500 Species

Superorder BatoideaOrders: Torpediniformes – electric raysPristiformes – sawfishesRajiformes – true raysMylobatiformes – eagle rays

Order TorpediniformesFamily Torpedinidae – (electric rays)

Family Narcinidae – (electric rays)

Torpedo rayTorpedo nobiliana

NumbfishNarcine maculata

TorpedinidaeFamily Torpedinidae – (electric rays)

Torpedo rayTorpedo nobiliana

Bottom dwelling, shallow coastal waters to 1,000 m

Slow moving, propelling themselves along with their tails

Feed on invertebrates and small fish

Prey below the sand using electricity to stun and capture

NarcinidaeFamily Narcinidae – (electric rays)

NumbfishNarcine maculata

Slow-swimming bottom-dwellers that feed on small fishes and invertebrates off the bottom

Generate a moderate shock if disturbed and contact is made with the electric organs

Electrical discharges of narcinids have been measured at 8-37 volts, much less than the electric rays of the genus Torpedo

Order PristiformesFamily Pristidae – (sawfishes)

Common sawfishPristis pristis

Although they are similar in appearance, sawsharks are distinct from sawfish. Sawfish have a much larger maximum size, lack barbels, have evenly sized rather than alternating sawteeth, and have gill slits on their undersurface rather than on the side of the head

Order RajiformesFamily Rhinobatidae – (guitarfishes)

Family Rajidae – (skates)

Common guitarfishRhinobatos rhinobatos

Big SkateRaja binoculata

RhinobatidaeFamily Rhinobatidae – (guitarfishes)

Common guitarfishRhinobatos rhinobatos

To 225 kg (500 lb) to 3 m (9.8 ft) in length, Ovoviviparous

Bottom feeders, preferring small crustaceans

Teeth are small and numerous, arranged in 65 or 70 rows

Body form intermediate between those of sharks and rays

Tail has a typical ray-like form, head has a triangular shape

RajidaeFamily Rajidae – (skates)

Big SkateRaja binoculata

Benthic rays occurring in all oceans, from Arctic to Antarctic waters and from shallow coastal shelfs to abyssal regions

Tail slender, 2 reduced dorsal fins and a reduced caudal fin

Skin prickly in most species, the prickles often in a row along midline of dorsal

Disc quadrangular to rhomboidal

Five pairs of ventral gill slits

Oviparous

Order MylobatiformesFamily Platyrhinidae – (thornback ray)Family Zanobatidae – (pan rays) Family Hexatrygonidae – (longsnout stingray)Family Urolophidae – (round rays)Family Urotrygonidae – (smalleyed round ray)Family Dasyatidae – (stingrays)Family Potamotrygonidae – (river rays)Family Gymnuridae – (butterfly rays)Family Myliobatidae – (eagle rays)

Pelagic stingrayPteroplatytrygon violacea    

   

Spotted eagle rayAetobatus narinari

PlatyrhinidaeFamily Platyrhinidae – (thornback ray)

To 1 m (3.3 ft) from 4.5 to 8.75 lb (2 to 3.98 kg)

In sexually mature fish some of the spines are thickened with button-like bases (known as bucklers)

Usually found on mud, sand or gravel 10-60m

Feed on small crustaceans, amphipods shrimps, crabs, and small fish.

Thornback ray Raja clavata

ZanobatidaeFamily Zanobatidae – (pan rays)

Striped panray Zanobatus schoenleinii

Occurs in shallow coastal waters to moderate depth, over sandy and sandy-muddy bottoms

Feeds on mollusks and other benthic invertebrates

Ovoviviparous

HexatrygonidaeFamily Hexatrygonidae – (sixgill stingray)

Snout translucent, depressed, produced and may act as an electroreceptive organ

Large spiracles with external flaplike valve and well behind eyes

Two serrate spines in tail; Length of disc greater than width

Feeding habits unknown

6 Gill openings

Sixgill stingrayHexatrygon bickelli

UrolophidaeFamily Urolophidae – (round rays)Well-developed caudal fin; tail moderately long;

Anterior margin of pectorals continuous along side of head

One or more long poisonous spines on tail

Feed benthic invertebrates, copepods, amphipods, mysids

Oviparous

Round rayRajella fyllae

UrotrygonidaeFamily Urotrygonidae – (American round stingrays)

Disc width less than 1.3 times disc length

Tail slender as long as the disc; No dorsal fin

Distinct poisonous spines; Previously in Urolophidae

Smalleyed round stingrayUrotrygon microphthalmum

DasyatidaeFamily Dasyatidae – (stingrays)

Pelagic stingrayPteroplatytrygon violacea    

   

Chiefly marine; also in brackish and freshwater

Side of head continuous with the anterior margin of pectoral fin

Tail long and whip-like. venomous spine on tail, which can cause excruciating pain to humans

Largest species to about 4m

Ovoviviparous

PotamotrygonidaeFamily Potamotrygonidae – (river rays)Potamotrygonids are much maligned and feared because of their venomous caudal stings, but pose little or no threat if not stepped on or directly interfered with. The Potamotrygonidae is the only living chondrichthyan family restricted to freshwater habitats.

Raspy river stingrayPotamotrygon scobina 

GymnuridaeFamily Gymnuridae – (butterfly rays)

Atlantic, Indic and Pacific Oceans

Marine, rarely in estuaries

Outer anterior margin of pectorals continuous along side of head

Dorsal fin and tail spines present or absent

Disc extremely broad

Tail short

Twin-spot butterfly ray Gymnura bimaculata

MyliobatidaeFamily Myliobatidae – (eagle rays)

Spotted eagle rayAetobatus narinari

Head elevated above disc

Jaws powerful with large platelike crushing teeth

Pectoral fins reduced or absent opposite the eyes

Some known for their leaping ability high into the air

Viviparous