Pogonopoma Regan 1904

Pogonopoma obscurum, Photo provided by R. E. Reis

Pogonopoma parahybae, Photo by K.S. Cummings

Pogonopoma wertheimeri, Photo by K.S. Cummings

TAXA LIST

Only one species, Pogonopoma wetheimeri (Steindachner, 1867), used to be recognized; however, Quevedo and Reis in their description of P. obscurum synonymized Pogonopomoides with Pogonopoma.  The diagnosis below is from Quevedo and Reis (2002) and the character numbers and states are from Armbruster (1998).


SYNONYM

Pogonopomoides Gosline 1947


SPECIES



DIAGNOSIS

Pogonopoma is diagnosed by: contact of the hyomandibular condyle solely to the pterotic-supracleithrum (5:1), lateral wall of pterygoid channel much higher than mesial wall (6:1), one to several vertebrae above the anal fin with bifid hemal spines (23:0), posterior processes of the pelvic basipterygium pointed and thin (33-1), and U-shaped diverticulum of the esophagus retroperitoneal, wide, not expandable and with anterior section reduced.



DESCRIPTION

Pogonopoma is a cylindrically-shaped loricariid.  Ground color in alcohol preserved specimens is grayish-brown with large dark spots occasionally developed on the head, upper sides, and dorsal fin.  Abdomen is gray.  The abdomen is mostly unplated except for a row of large plates along the sides, a large patch of small plates between the pelvic fins, and a few scattered small plates along the pectoral girdle.  An adipose fin is present although occasionally only the spine is present and is fused with the dorsal plates.  The cheek is covered in long but thin odontodes that form a dense patch.  Dorsal  II-7, pectoral I-6, pelvic I-5, anal 6 (one unbranched and five branched), caudal I-14-I.  23-26 lateral line plates, 6-7 plates under the base of the dorsal fin, 10-12 plates in the depressed dorsal fin, 14-15 postdorsal plates, 10-12 postanal plates, and 38-89 teeth per jaw ramus.



COMPARISONS

Pogonopoma is not readily identifiable from other hypostomines as a whole. It seems as if the genus is a very old group with three very divergent species. In most other groups, probably the three species would be recognized as separate genera, but there seems to be little reason for this becuase each of the genera would be monotypic. In order to actually separate the species, I will do so one species at a time.

Pogonopoma obscurum can be separated from all other hypostomines by a combination of having no dorsal flap of the iris and greater than seven dorsal-fin rays. The only other hypostomines with greater than seven dorsal-fin rays are Pterygoplichthys, the Acanthicus group, and the Chaetostoma group. Pogonopoma obscurum can be separated from these genera (except some Pterygoplichthys) by lacking hypertrophied odontodes on the cheek and from all of the genera except Acanthicus itself and a few Chaetostoma by the lack of the adipose fin.

Pogonopoma parahybae can be identified from most other loricariids by a combination of a loss of the adipose fin and median pre-adipose plate, a well developed dorsal fin spinelet (vs. a small, rectangular spinelet or no spinelet in Hemipsilichthys, Pareiorhaphis, Kronichthys, Pareiorhina, and Corymbophanes andersoni), six anal fin rays, and a coracoid that is exposed ventrally.  Within the Rhinelepis group, P. parahybae differs from P. wertheimeri by the lack of elongate cheek odontodes and lack of an adipose fin; from P. obscurum by having seven dorsal-fin rays (vs. eight to 11); from Pseudorinelepis by the lack of tall ridges on the pterotic-supracleithrum, lack of cheek spines, an incompletely plated abdomen, and the following morphometric features (Table 2): a longer snout length/SL ratio (0.176-0.193 vs. 0.138-0.176), a shorter thorax length/SL ratio (0.189-0.233 vs. 0.258-0.317), a smaller head depth/SL ratio (0.155-0.190 vs. 0.200-0.260), and a smaller cleithral width/SL ratio (0.233-0.275 vs. 0.275-0.311); and from Rhinelepis by having smaller gill openings, only a few plates on the abdomen (versus fully plated), an exposed posteroventral projection of the coracoid, lack of a plate between the opercle and the pterotic-supracleithrum, and the following morphometric features (Table 2): a smaller predorsal length/SL ratio (0.373-0.400 vs. 0.430-0.473), a smaller head length/SL ratio (0.304-0.326 vs. 0.347-0.396), a smaller snout length/SL ratio (0.176-0.193 vs. 0.210-0.243), a smaller interorbital width/SL ratio (0.120-0.137 vs. 0.182-0.194), a larger postanal length/SL ratio (0.260-0.289 vs. 0.203-0.241), a larger dorsal fin length/SL ratio (0.235-0.256 vs. 0.195-0.212), a smaller head depth/SL ratio (0.155-0.190 vs. 0.214-0.243), and a smaller cleithral width/SL ratio (0.233-0.275 vs. 0.286-0.333).

Pogonopoma wertheimeri can be distinguished from other Hypostominae by a combination of the following characteristics: a dense patch of odontodes on the cheek that are very elongate and not evertible (the odontodes in most Hypostominae with cheek odontodes, are not dense, are not as long, or are evertible), a well-developed dorsal fin spinelet (vs. a small, rectangular spinelet or no spinelet in Hemipsilichthys, Pareiorhaphis, Kronichthys, Pareiorhina, and Corymbophanes andersoni), 6 anal fin rays, one pre-adipose plate (vs. 3 or more in Delturus and Upsilodus), and a coracoid that is exposed ventrally.  Within the Rhinelepis group, Pogonopoma differs from all others by the presence of an adipose fin.  In addition, Pogonopoma differs from P. parahybae by the presence of elongate cheek odontodes and large (versus small) plates along the sides of the abdomen; from P. obscurum by having seven dorsal-fin rays (vs. eight to 11); from Pseudorinelepis by the presence of an incompletely plated abdomen, unkeeled plates, lack of tall ridges on the pterotic-supracleithrum, and a smaller head depth/SL ratio (0.161-0.198 vs. 0.200-0.260) (Table 2); and from Rhinelepis by presence of a smaller gill opening, an incompletely plated abdomen, large (versus small) plates along the sides of the abdomen, elongate cheek odontodes, lack of a large plate between the opercle and pterotic-supracleithrum, and the following morphometric features (see Table 2): a smaller predorsal length/SL ratio (0.366-0.413 vs. 0.430-0.473), a smaller head length/SL ratio (0.265-0.326 vs. 0.347-0.396), a smaller snout length/SL ratio (0.155-0.179 vs. 0.210-0.243), a smaller interorbital width/SL ratio (0.112-0.136 vs. 0.182-0.194), a larger dorsal-caudal length/SL ratio (0.342-0.396 vs. 0.298-0.338), and a smaller head depth/SL ratio (0.155-0.190 vs. 0.214-0.243).



DISTRIBUTION

There is only one species, Pogonopoma wertheimeri, in the Rio Mucuri in southeast Brazil (see below).

The question mark refers to a potentially introduced population of Rhinelepis.



LITERATURE CITED

Armbruster, J.W. 1998. Phylogenetic relationships of the suckermouth armored catfishes of the Rhinelepis group (Loricariidae: Hypostominae). Copeia 1998:620-636.

Quevedo, R. and R. E. Reis. 2002. Pogonopoma obscurum: a new species of loricariid catfish (Siluriformes: Loricariidae) from southern Brazil, with comments on the genus Pogonopoma. Copeia 2002: 402-410.


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