Snout elongated into a long, flat rostral saw with enlarged lateral teeth (Fig. 1) . . . Pristidae (p. 1410) 1b. Snout short to elongated, not saw-like ................................→ 2
2a. Free rear tips of pectoral fins anterior to pelvic-fin origins; dorsal fins large and strongly falcate; caudal fin with a strong ventral lobe (Fig. 2) . . . . . . . . . . . . . . . . Rhinidae (p. 1418) 2b. Free rear tips of pectoral fins opposite or posterior to pelvic-fin origins; dorsal fins, when present, rounded or angular, but not strongly falcate; caudal fin without a ventral lobe ......→ 3
3a. Pelvic fins not bilobate (Fig. 3a); males without alar spines on their discs ............→ 4 3b. Pelvic fins strongly bilobate, with a narrow anterior lobe and broad posterior lobe (Fig. 3b); males with curved, hooked alar spines on their discs (skates) .............→ 17
4a. Pectoral disc thick and flabby, with a large kidney-shaped electric organ at the base of the fin radials on each side that is visible through the skin (Fig. 6); no denticles or medial thorns on dorsal surface of disc and tail, body entirely naked....................→ 5 4b. Pectoral disc thick basally, flat peripherally, usually not flabby and without electric organs; denticles and usually medial thorns present on dorsal surface of disc and tail, ventral surface variably denticulate or naked ............................→ 8
5a. Mouth broadly arcuate, without labial folds and cartilages at ends (Fig. 4a, b); 2 dorsal fins, the first much larger than the second ..............................→ 6 5b. Mouth nearly transverse, with strong labial folds and cartilages at corners (Fig. 4c); 2, a single, or no dorsal fins, the first about as large as the second when 2 are present ........→ 7
snout extremely prolonged, blade-like, armed with tooth-like structures
Fig. 1 Pristidae
dorsal fins large, falcate
pelvic fin
pectoral fin
Fig. 2 Rhinidae
clasper of males
pelvic fins not bilobate
a)
clasper of males
pelvic fins bilobate
b)
(after Last and Stevens, 1994)
Fig. 3 ventral view of body
nostrils
a) Torpedinidae b) Hypnidae c) Narcinidae
mouth broadly arcuate
Fig. 4 region of nostrils and mouth
labial fold
mouth transverse
Key to Families 1401
6a. Disc longitudinally pear-shaped; tail greatly reduced, caudal fin about as high as dorsal fins (Fig. 5) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hypnidae (p. 1447) 6b. Disc truncate anteriorly, transversely elliptical, not pear-shaped; tail not greatly reduced, caudal fin much higher than dorsal fin (Fig. 6) . . . . . . . . . . . . . . . . . Torpedinidae (p. 1449)
7a. Snout with a broad, stiff, shovel-shaped rostral cartilage, readily felt by palpitation of the snout; a deep groove around mouth (Fig. 7a); teeth extending onto outer surfaces of upper and lower jaws in most species (Fig. 7a); 2 dorsal fins present (Fig. 7b) . . . . . . Narcinidae (p. 1434) 7b. Snout with a narrow, rod-shaped rostral cartilage; a shallow groove around mouth (Fig 8a); teeth not extending onto outer surfaces of upper and lower jaws; genera in the area with a single dorsal fin (Narke) or none (Temera) (Fig. 8b) . . . . . . . . . . Narkidae (p. 1443)
8a. Tail very thick and massive, with 2 large dorsal fins and a large caudal fin; no sting or stinging spine on tail (Figs 9 and 10).................................→ 9 8b. Tail more or less attenuated and slender, with 1 small to moderate-sized dorsal fin or none; a small caudal fin present and well developed, or variably reduced or absent; usually a sting present on tail (absent in Urogymnus, Aetomylaeus, and some members of Gymnuridae and Mobulidae) ...................................→ 10
tail reduced, caudal fin low
Fig. 5 Hypnidae
high caudal fin
electric organ
Fig. 6 Torpedinidae
teeth
deep grove
a) region of nostrils and mouth
nostril
a) region of nostrils and mouth
nostril
shallow groove
2 dorsal fins
b) dorsal view
Fig. 7 Narcinidae
1 dorsal fin present or absent
b) dorsal view
Fig. 8 Narkidae
1402 Batoid Fishes
9a. Disc narrow and wedge-shaped anteriorly; midback and tail with a row of small and often blunt thorns, and with a few additional thorns often present on scapular area (= shoulder region) (Fig. 9). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Rhinobatidae (p. 1423) 9b. Disc broad and rounded; tail and scapular area of disc with strong sharp thorns (Fig. 10) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Platyrhinidae (p. 1431)
10a. Head not elevated and laterally demarked from disc by a deep notch; eyes dorsolateral on head, well medial from edge of disc; snout not differentiated into separate rostral or cephalic fins; dorsal fin either absent or small and well behind pelvic-fin bases .........→ 11 10b. Head elevated and laterally demarked from disc; eyes lateral on head; anterior part of pectoral fins formed as a separate rostral fin or paired cephalic fins or horns; dorsal fin moderately large, close to or over pelvic-fin bases.........................→ 15
11a. Six pairs of gill openings (Fig. 11a); spiracles well separated from eyes (Fig. 11b) ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hexatrygonidae (p. 1477) 11b. Five pairs of gill openings; spiracles close to eyes .........................→ 12
12a. Disc broad and laterally expanded, rhomboidal and at least 1.6 times as wide as long (Fig. 12). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Gymnuridae (p. 1506) 12b. Disc not greatly expanded, diamond-shaped or rounded, but not rhomboidal, usually less than 1.3 times as wide as long ...................................→ 13
row of small blunt thorns
Fig. 9 Rhinobatidae
strong sharp thorns
Fig. 10 Platyrhinidae
a) dorsal view b) ventral view
6 gill slits
Fig. 11 Hexatrygonidae
tail distinctly cross-banded
disc at least 1.6 times broader than long
Fig. 12 Gymnuridae
eyespiracle
Key to Families 1403
13a. Caudal fin absent or reduced to dorsal and ventral longitudinal folds on midline of tail; tail more or less elongated and whip-like (Fig. 13) . . . . . . . Dasyatidae (p. 1479) 13b. A small but well-developed caudal fin present; tail relatively short and not whip-like..............→ 14
14a. Preorbital length of snout over 6 times orbit diameter; nasal curtain short and broad, not overlapping mouth; floor of mouth without lobate papillae; adults attaining nearly 3 m in length (Fig. 14) . . . . . . . . . . . . . . . . . . . . . . Plesiobatidae (p. 1467) 14b. Preorbital length of snout much less than 6 times orbit diameter; nasal curtain longer and narrow, overlaps mouth; floor of mouth with lobate papillae; adults to less than 1 m in length (Fig. 15) . . Urolophidae (p. 1469)
15a. Snout formed into prehensile, elongated, bilobate cephalic fins, laterally based on head; mouth very large, jaws weak and transversely expanded, with very small cuspidate or hexagonal teeth; gills with filter plates (Fig. 16) . . . . . . . . . . . Mobulidae (p. 1524) 15b. Snout formed as a single convex or low bilobate pair of rostral fins; mouth small, jaws very stout and longitudinally expanded with large transversely expanded plate-like teeth that form a powerful crushing and grinding mill for eating shellfish; gills without filter plates ...................→ 16
no caudal fin
tail whip-like
Fig. 13 Dasyatidae
Fig. 14 Plesiobatidae Fig. 15 Urolophidae
cephalic fins
Fig. 16 Mobulidae
1404 Batoid Fishes
16a. Rostral fin single and convex; forehead rounded and not expanded anteriorly or medially notched; 1 medial row of expanded plate-like teeth in each jaw, usually with 3 rows of smaller hexagonal teeth on each side of them (except Aetobatus, in which the lateral teeth are lost) (Fig. 17) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Myliobatidae (p. 1511) 16b. Rostral fin bilobate and broadly notched medially; forehead expanded anteriorly and forming a ledge over base of 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 (Fig. 18) . . . . . . . . . . . . . . . . Rhinopteridae (p. 1520)
17a. Anterior and posterior lobes of pelvic fins completely separate, anterior lobe leg-like; species in the area naked except for alar spines of males, without dorsal fins and with the tail very slender and caudal fin long and low (Fig. 19) ... . . . . . . . . . . . . Anacanthobatidae 17b. Anterior and posterior lobes of pelvic fins conjoined basally, anterior lobe not leg-like; species in the area with dorsal surface of disc and tail variably covered with denticles and thorns, with 2 low dorsal fins far posterior on tail, with a short, greatly reduced caudal fin and with the tail moderately stout ......→ 18
arrangement of teeth in upper jaw
hexagonal teeth
a single row of plate-like teeth
Aetobatus Aetomylaeus, Myliobatis
3 rows of plate-like teeth
a single, convex rostral fin
Fig. 17 Myliobatidae
bilobed rostral fin
teeth in upper and lower jaws
Fig. 18 Rhinopteridae
ventral view dorsal view
lobes of pelvic fins not cojoined anterior lobe leg-like
Fig. 19 Anacanthobatidae
Key to Families 1405
18a. Species in the area with a reduced rostral cartilage and soft snout; basihyal cartilage of hyobranchial skeleton with lateral projections; scapulocoracoid (shoulder girdle) usually with stout or slender anterior bridge separating predorsal and ventral fenestra; clasper glans of adult males not greatly expandable, usually without rhipidion or shield; clasper ventral terminal cartilage spoon-shaped, without a sharp lateral edge and not forming an external clasper shield; clasper dorsal terminal cartilages 2 and 3 arranged in parallel (Fig. 20) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Arhynchobatidae (p. 1457) 18b. Species in the area with a stout rostral cartilage and hard sno