Munroe: Systematics of western Atlantic Symphurus 
Table 6 
Frequency distributions of numbers of total vertebrae for western Atlantic Symphurus species. 
Number of vertebrae 
Species 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 
nebulosus — — — — — — — — — — — — — — — — — — 1 9 15 2 
arawak 117 21 6 — — — — — — — — — — — — — — — — — — 
rhytisma — — — — — — — 1 6 2 — — — — — — — — — — — — 
billykrietei — — — — — — — — — — — 9 49 33 2 — — — — — — — 
stigmosus — — — — — — — — — — — — 5 7 — — — — — — — — 
ginsburgi — — — — — — — — — — — 7 38 13 — — — — — — — — 
pelicanus — — — — 1 7 25 27 — — — — — — — — — — — — — — 
pusillus — — — — — — — — 4 15 10 — — — — — — — — — — — 
marginatus — — — — — — — — — — — — 1 17 35 41 2 2 — — — — 
piger — — — — — — 1 4 48 80 11 — — — — — — — — — — — 
trewavasae — — — — — — — — 3 25 31 8 3 — — — — — — — — — 
kyaropterygium — — — — — — — 1 9 3 1 — — — — — — — — — — — 
minor — — 11 45 19 4 — — — — — — — — — — — — — — — — 
parvus — — — — 1 13 23 34 7 — — — — — — — — — — — — — 
ommaspilus — — — — 10 16 — — — — — — — — — — — — — — — — 
diomedeanus — — — — — — — — 4 50 131 34 — — — — — — — — — — 
jenynsi — — — — — — — — — — — — — — — — — — 4 37 36 11 
plagiusa — — — — — 1 16 30 69 26 1 — — — — — — — — — — — 
urospilus — — — — — 3 54 49 7 1 — — — — — — — — — — — — 
caribbeanus — — — — — — — — — 1 43 33 5 — — — — — — — — — 
civitatium — — — — — — — 2 34 109 28 2 — — — — — — — — — — 
oculellus — — — — — — — — — — — — — 6 35 20 2 — — — — — 
plagusia — — — — — — — — 1 4 21 13 5 — — — — — — — — — 
tessellatus — — — — — — — — — 1 3 52 97 89 37 3 — — — — — — 
length (CFL): base of articulations of middle caudal- 
fin rays to tip of longest middle rays. Pelvic-fin length 
(PL); (only blind-side pelvic fin present in adults): 
basal articulation to distal tip of longest ray. Pelvic 
to anal length (PA): shortest horizontal distance from 
base of most posterior pelvic-fin ray to anal-fin ori- 
gin. Head length (HL): tip of fleshy snout to most 
posterior extension of upper fleshy lobe of opercu- 
lum. Head width (HW): greatest distance across head 
at posterior portion of operculum. Postorbital head 
length (POL): posterior margin of lower eye to poste- 
rior extent of upper fleshy lobe of operculum. Upper 
head lobe width (UHL): distance at operculum from 
dorsal margin of body to dorsal origin of operculum. 
Lower head lobe width (LHL): distance at opercu- 
lum from dorsal origin of operculum to most ventral 
part of operculum. Snout length (SNL): anterior rim 
of lower eye to tip of snout. Upper jaw length (UJL): 
shortest horizontal distance from bony tip of premax- 
illa to angle of mouth. Eye diameter (ED): greatest 
horizontal diameter of the cornea of the lower eye; 
does not include fleshy tissue surrounding eye. Chin 
depth (CD): vertical distance from angle of mouth to 
most ventral aspect of head. Upper opercular lobe 
(OPUL): vertical distance from midpoint of opercu- 
lar indentation to dorsal origin of operculum. Lower 
opercular lobe (OPLL): vertical distance from mid- 
point of opercular indentation to ventral margin of 
operculum. 
Qualitative characters 
The following qualitative characters are also impor- 
tant in identifying Symphurus, especially when used 
in combination with meristic and morphometric data. 
Pupillary operculum (Fig. 3AJ A triangular or 
rounded, pigmented structure on the upper part of 
the cornea. A presumed function of the pupillary oper- 
culum is to shade the retina from direct exposure to 
light. Chabanaud (1948a), Ginsburg (1951), and 
Menezes and Benvegnu (1976) did not use this char- 
acter in their studies on Atlantic tonguefishes. 
Mahadeva (1956) and Munroe ( 1987), however, found 
this character useful for diagnosing some eastern 
Pacific and Atlantic species. For example, a pupil- 
lary operculum is not found in any eastern Atlantic 
tonguefish nor in any western Atlantic deepwater 
species, and its absence is useful in distinguishing these 
Symphurus from other western Atlantic species with 
similar meristic and morphometric features but which 
possess a well-developed pupillary operculum. 
