Figure 5. Humeral processes of A) Synodontis dhonti,
holotype, MRAC 14344, 395 mm TL, 325 mm SL, B) S.
irsacae, MRAC A3-033-P-0036-0040, 139 mm TL, 116
mm SL, C) S. polli, MRAC A3-033-P-0076-0080, 160
mm TL, 132 mm SL, D) S. ilebrevis, UF 160942, holo-
type, 139 mm TL, 116 mm SL. An axillary pore is present
in A), absent in other species shown.


BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL. 46(4)

 transversely bisects the toothpad. The separated condi-
 tion is referred to herein as interrupted, and the
 unseparated condition as uninterrupted. This appears to
 be the first study to examine this character in
 Synodontis, although the length of the premaxillary
 toothpad has often been used in previous morphological
 examinations of Synodontis species.
 The skin of the ten endemic species of Tanganyikan
 Synodontis is unique within the genus in having numer-
 ous minute, vertical skin folds. The purpose of these
 folds is unknown. The folds distinguish the Tanganyikan
 species from species outside the lake's basin but are not
 helpful in distinguishing among species from the lake.
 The papillae on the skin of certain species, however,
 separates them from other Tanganyikan species in which
 the skin is bare. This character is most useful in the
 identification of fresh or well-preserved specimens, as
 the papillae may degrade.
 Some species of Synodontis have a swelling in
 the posterior part of the intestine which Taverne and
 Aloulou-Triki (1974) termed the "poche intestinal" and
 which is referred to herein as the hindgut chamber. A
 similar structure is known only in species of Kyphosidae,
 a family of herbivorous, marine fishes that utilizes fer-
 mentative digestion in the hindgut (Rimmer & Wiebe
 1987; Clements & Choat 1997; Mountfort et al. 2002).
 The presence of a similar structure in highly herbivo-
 rous mochokid species such as S. polli,
 Brachysynodontis batensoda, and Hemisynodontis
 membranaceus suggests that the mochokid hindgut
 chamber may play a similar role. If so, this is the first
 time that such a behavior and structure has been found
 in a freshwater fish. The presence or absence of the
 hindgut chamber appears to be species-specific and can
 distinguish between species for which few good exter-
 nal diagnostic characters exist.

 TAXONOMIC DESCRIPTIONS
 Order Siluriformes Hay 1929
 Family Mochokidae Jordan 1923
 Genus Synodontis Cuvier 1817

 Diagnosis. Lateral line complete and midlateral,
 extending onto base of caudal fin. Cone-shaped genital
 papilla in male; papilla absent in female. Anterior nos-
 trils tubular; posterior nostrils with semicircular flaps of
 skin along anterior margin. Gill opening extends from
 lower edge of ventral rounded occipital-nuchal process
 to point horizontal to base of pectoral fin spine. Gill
 membranes broadly joined at isthmus. Well developed,
 papillate, membranous flap immediately posterior to pre-
 maxillary toothpad. Eye with free orbital margin.