| 1a |
Arms repeatedly dichotomously
branched (picture);
plates
of arms
and disk
concealed by a thick skin; diameter of disk sometimes exceeding 5 cm;
strictly
subtidal |
Gorgonocephalus
eucnemis |
| 1b |
Arms
not branched; plates
of arms
and disk
usually distinct, although those on the disk
may be small or partly obscured by spines; diameter of disk
not exceeding 2 cm; intertidal or subtidal |
2 |
| 2a |
Plates on upper surface of arms
separated from one another by small supplementary plates; coloration
usually
with some bright red or purplish red, this typically concentrated in
streaks
or blotches |
Ophiopholis
aculeata |
| 2b |
Plates on upper surface of arms
not separated from one another by small supplementary plates;
coloration
usually not including bright red or purplish red streaks or blotches
(in
Ophiura
leptoctneia, which is strictly subtidal, the aboral
surface of the disk
may be rose, violet, or red, with a few streaks; some other species are
pinkish, but these ae not likely to have prominent markings) |
3 |
| 3a |
Aboral
surface of
disk
with conspicuous marginal notches into which the arms
are inserted (photo),
each
notch bordered on both sides by an arm
comb |
4 |
| 3b |
Aboral
surface of
disk
without marginal notches into which the arms
are inserted, and without arm
combs |
6 |
| 4a |
Oral
shields
(the largest plates on the oral
surface, situated between the bases of the arms)
widest on the side nearer the margin of the disk;
spines of arm
combs
at least 5 times as long as wide, with sharp tips; prevailing color of
aboral
surface
of disk
rose, violet,
or red |
Ophiura leptoctenia |
| 4b |
Oral
shields
widest near their middle portions (photo);
spines of arm
combs
usually not more than 3 times as long as wide, with blunt or
truncate
tips; prevailing color of aboral
surface generally some shade of gray, bluish gray, or greenish gray,
rarely
reddish |
5 |
| 5a |
Spines of arm combs
contiguous and with truncate
tips |
Ophiura
luetkenii |
| 5b |
Spines of arm combs
well separated and with bluntly rounded tips |
Ophiura sarsi |
| 6a |
With 4 oral
papillae
on both sides of each jaw |
7 |
| 6b |
With 3 oral
papillae
on both sides of each jaw |
8 |
| 7a |
Plates on upper surface of arms
nearly circular, hardly wider than long, and barely in contact with one
another even near the bases of the arms;
interbrachial areas of oral surface of disk
(the areas between the arm
insertions) without scales |
Amphioplus strongyloplax |
| 7b |
Plates on upper surface of arms
nearly triangular (but with truncated
corners), decidedly wider than long and in contact with one another at
least near the bases of the arms;
interbrachial areas of oral surface of disk
with small scales |
Amphioplus macraspis |
| 8a |
Oral
papillae
of the pair farthest from the tip of the jaw decidedly longer and wider
than those of the other 2 pairs |
9 |
| 8b |
All 3 pairs of oral
papillae about the same size |
10 |
| 9a |
Length of arms
not over
4.5 times the diameter of the disk;
longest arm
spines usually
shorter than the width of the arm
units from which they originate; ovoviviparous
(the young develop in the bursal pockets) |
Amphipholis squamata |
| 9b |
Length of arms
7 or
8 times the diameter of the disk;
longest arm
spines longer
than the width of the arm
units from which they originate; oviparous
(discharging eggs instead of brooding young in the bursal pockets) |
Amphipholis pugetana |
| 10a |
Arm
spines blunt, markedly
flattened |
Amphiodia occidentalis |
| 10b |
Arm
spines pointed,
either not flattened or only slightly flattened (oval in cross-section) |
11 |
| 11a |
Arm
spines not at all
flattened (circular in cross-section) |
Amphiodia
urtica |
| 11b |
Arm
spines slightly
flattened (oval in cross-section) |
Ampiodia periercta |
