SQUALOMORPHEA (SHARKS)
9b Mouth ventral (under snout) ............................................. 10
lOa Length of upper C lobe about half or more
oftotallength ..................................... ALOPIIDAE (No. 16)
lOb Upper C lobe much less than half of total length .................... 11
11a C lunate, its lower lobe more than half as long as
upper lobe; distinct keel along each side of caudal
peduncle ................................................................ .. .... 12
lIb C not lunate, the lower lobe less than half length
of upper lobe; keel on peduncle present or absent .................. 13
12a Teeth minute, with 4 or 5 functional series
in rows of 100 or more in each jaw;
gill-rakers long and numerous; 1st gill
slits nearly continuous under throat .. CETORHINIDAE (No. 15)
12b Teeth large, with 1 or 2 functional series in
rows of 24-30 in each jaw; 1st gill slits
widely separated ................................. LAMNIDAE (No. 14)
13a A groove from each nostril to mouth;
nasal barbel distinct; last 2 gill slits
close together ............................ ORECTOLOBIDAE (No.7)
13b Nostril groove and barbel not both present; last 2
gill slits not closer together than the others ........................... 14
14a First D base distinctly shorter than C .................................. 15
14b First D base about as long as C and
situated in front of V .............. PSEUDOTRIAKIDAE (No. 12)
44
15a First D base in front of V .................................................. 16
15b First D base over or behind V ....... SCYLIORHINIDAE (No. 11)
16a Last gill slits in front ofP; teeth slender,
awl-like, similar in both jaws ............................................. 17
16b Last gill slits over P base .................................................. 18
17a Orbit height greater than height of 2nd
D; apex of dorsal fins over middle of
their bases .................... PSEUDOCARCHARIIDAE (No. 18)
17b Orbit height less than height of 2nd D;
apex of dorsal fins over rear end of their
bases .................................... ODONTASPIDIDAE (No. 19)
18a Head hammer-shaped (flattened in front
and greatly expanded laterally) ............ SPHYRNIDAE (No. 13)
18b Head normal, not expanded laterally ........... .. .. .. ... .. ... .. .. .. ... 19
19a C without distinct lower lobe; 2nd Dbase
subequal to or greater than length of 1st D
base; teeth with erect cusps, usually several
functional rows ........................... PROSCYLLIIDAE (No. 10)
~ 10
19b Lower caudal lobe distinct; 2nd Dbase
shorter than 1st Dbase .............. CARCHARHINIDAE (No.9)