Munroe: Western Atlantic tonguefishes of the Symphurus plagusia complex 



273 



scale rows on head 21, transverse scale count 42). Ad- 

 ditionally, the specimen has small ctenoid scales on the 

 blind sides of the dorsal and anal fin rays and a rela- 

 tively large eye (10.6% HL), features characteristic of 

 S. tessellatus. Plagusia brasiliensis is therefore re- 

 garded as a junior subjective synonym of Symphurus 

 tessellatus (Quoy and Gaimard 1824). 



In their revision of the tonguefishes occurring in the 

 western South Atlantic, Menezes and Benvegnu (1976) 

 reported that the species they identified as S. plagusia 

 had high counts and that the pigmentation consisted 

 of sharply contrasting crossbands with dorsal and anal 

 fins becoming almost black in their posterior portions. 

 These authors found little variation in their material 

 and believed that only a single species was present on 

 the inner continental shelf of southern South America. 

 Menezes and Benvegnu (1976) used the oldest available 

 name, Symphurus plagusia (Schneider, in Bloch and 

 Schneider 1801), for their species. These authors also 

 suggested that the subspecific designation for S. pla- 

 gusia, as proposed by Ginsburg (1951), should be re- 

 examined. Based on the high counts and color descrip- 

 tion of their specimens (strongly banded with fins 

 becoming black posteriorly) and the capture location 

 (open-shelf region where S. plagusia [sensu strictu] is 

 rare), it is probable that Menezes and Benvegnu had 

 studied only S. tessellatus. 



Comparisons Symphurus tessellatus most closely 

 resembles and is completely sympatric throughout the 

 Caribbean and warmer waters of the western South 

 Atlantic with S. oculellus, S. caribbeanus, and S. pla- 

 gusia. Symphurus tessellatus differs from S. oculellus 

 in having 4-8 small but well-developed scales on the 

 blind sides of the dorsal and anal fin rays (especially 

 evident in specimens >70mm SL), a larger eye (79- 

 114, x 95 HL in S. tessellatus vs. 68-104, x 84 HL), 

 and lower meristic values (dorsal fin rays 91-102 vs. 

 99-106 in S. oculellus; anal fin rays 77-86 vs. 81-88; 

 total vertebrae usually 50-53 versus 53-54). Sym- 

 phurus tessellatus lacks a fleshy ridge on the ocular- 

 side lower jaw that is usually present and well devel- 

 oped in S. oculellus (compare Figures 4c and 4d). Also, 

 the posterior extension of the jaws is slightly less ex- 

 tensive in S. tessellatus, reaching only to about the ver- 

 tical line through the rear margin of the pupil or rear 

 margin of the lower eye. In S. oculellus, the jaws ex- 

 tend further backwards reaching a vertical line through 

 the posterior margin of the eye, and in many specimens 

 the jaws extend slightly posterior to the vertical line 

 through the posterior margin of the lower eye. 



Symphurus tessellatus generally has about nine wide, 

 dark-brown crossbands; S. oculellus has 10-14 (usual- 

 ly 10-12) narrower crossbands. In S. tessellatus the 

 caudal fin and the posterior one-third of the dorsal and 



anal fins are usually dark -brown or black and without 

 an alternating series of blotches and unpigmented 

 areas. In S. oculellus, the dorsal and anal fins are not 

 uniformly dark-brown or black; instead, in the posterior 

 two-thirds of the dorsal and anal fins there is an alter- 

 nating series of blotches and unpigmented areas. 



Symphurus tessellatus, especially juveniles and small 

 adults (to ~ 150 mm SL), are superficially similar in 

 overall body shape, relative eye size, and body pig- 

 mentation (crossbanding) to S. caribbeanus. However, 

 S. tessellatus is easily distinguished from S. carib- 

 beanus by the black spot on the outer surface of the 

 ocular-side opercle and presence of scales on the blind 

 sides of the dorsal and anal fin rays (both absent in 

 S. caribbeanus), and S. tessellatus has the posterior 

 dorsal and anal fins, as well as the caudal fin, uniform- 

 ly darkly-pigmented without alternating blotches and 

 unpigmented areas, and often has black pigment 

 patches on the blind side of the body. In contrast, in 

 S. caribbeanus, posterior regions of the vertical fins 

 have alternating dark blotches and unpigmented areas 

 without a progressive darkening in coloration pos- 

 teriorly in these fins, and the blind side of the body 

 lacks black pigment patches. Symphurus tessellatus 

 also has modally higher counts than S. caribbeanus 

 (total vertebrae 50-53 vs. 49-50 in S. caribbeanus; 

 dorsal fin rays 91-102 vs. 89-96; anal fin rays 77-86 

 vs. 74-80; 81-96 scales in a longitudinal series vs. 

 78-89). 



Symphurus tessellatus can readily be distinguished 

 from S. plagusia and S. civitatium, and differences 

 between these species were discussed in the "Compari- 

 sons" sections under the accounts for S. plagusia and 

 S. civitatium, respectively. 



Symphurus tessellatus is quite distinct from other 

 Atlantic tonguefishes. Some meristic values of this 

 species overlap those of S. marginatus (Goode and 

 Bean) and S. diomedeanus, a species sometimes col- 

 lected with S. tessellatus. Additionally, in the southern 

 extent of its range S. tessellatus sometimes co-occurs 

 with S. jenynsi. 



Although S. tessellatus and S. marginatus have near- 

 ly complete overlap in fin-ray and vertebral counts, 

 such similarities are the only ones between these other- 

 wise distinctive species. Important differences between 

 these species occur in ID pattern (1-4-3 vs. 1-3-2 in 

 S. marginatus), hypural number (4 vs. 5), presence of 

 scales on the blind sides of the dorsal and anal fin rays 

 in S. tessellatus (absent in S. marginatus), and pigmen- 

 tation features including an unpigmented peritoneum 

 (black in S. marginatus), crossbanding on the body, and 

 a black spot on the ocular-side opercle (vs. no cross- 

 banding on body; instead, body with a dark blotch 

 in the caudal region and no opercular spot in S. 

 marginatus). 



