Auchenoglanis sacchii ( Vinciguerra, 1898 )

Retzer, Michael E., 2010, Taxonomy of Auchenoglanis Günther 1865 (Siluriformes: Auchenoglanididae), Zootaxa 2655 (1), pp. 25-51 : 46-47

Auchenoglanis sacchii ( Vinciguerra, 1898)

( Fig. 4 , Table 3)

Oxyglanis Sacchii Vinciguerra 1898: 250 . Type locality: fiume Omo a Murz [ Ethiopia]. Holotype: MSNG 14506 .

Material examined: Ethiopia, Southern Nations Nationalities and Peoples Region: Omo River at Murzú , MSNG 14506 , (307.7 mm SL, holotype) .

Diagnosis: Auchenoglanis sacchii can be distinguished from all other Auchenoglanis species by its adipose-fin origin that is over the origin of the anal fin. All other species of Auchenoglanis have adipose-fin origins that are anterior to the anal-fin origin. Note that this is evident on the holotype and described in the original description (see Comments below).

Auchenoglanis sacchii can be further distinguished from A. acuticeps , A. occidentalis , A. senegali , A. tanganicanus , and A. wittei by having a shorter preorbital-head length relative to the interorbital distance (PrOL to IOD ratio 1.3 in A. sacchii versus greater than 1.5 in A. acuticeps , A. occidentalis , A. senegali , A. tanganicanus , and A. wittei ).

The squarish premaxillary tooth patches of A. sacchii separate it from the oblong-oval, round, triangular, or tear-shaped tooth patches of A. occidentalis , A. acuticeps , A. biscutatus , A. tchadiensis , and A. senegali ( Fig. 2 ). Adult A. sacchii can be distinguished from A. biscutatus by having the anterior margins of the nuchal plates straight to slightly curved rather than strongly curved ( Fig. 1a ).

Description: Morphometrics are presented in Table 3. Because of the poor condition of the only known specimen, the holotype, the following description of the body is from the original description ( Vinciguerra 1898) that is detailed and provides helpful descriptive information. The fin ray counts are as follows: dorsal fin I,7 (1); pectoral fin I,9 (1), pelvic fin i,5 (1). The snout is long and its length is over one-half the head length. The mouth is small and there are two premaxillary teeth. The barbels are all short and maxillary barbel does not reach the orbit. The lower lip is thick. The dorsal spine is thick and approximately the equal to the body depth. The adipose fin is small. The pectoral spines are thick and longer than the dorsal fin and the head length.

No coloration can now be described from the holotype, a dried specimen. The original description gives only a vague one-sentence description that the body is brown with darker spots on the body and fins.

Comments: The diagnostic character that clearly distinguishes A. sacchii from the other species is the position of the origin of the adipose fin relative to the origin of the anal fin. The holotype is in poor condition and perhaps the position of the adipose has been distorted and changed from its original position. However, the original description states that the adipose-fin origin is over the origin of the anal fin. Also, Vinciquerra (1898) noted that distance between the dorsal fin and adipose fin is three times the length of the base of the adipose fin. In the other species, the length of adipose fin is much greater than the space between the dorsal fin and adipose fin.

Range: Auchenoglanis sacchii is known only from the Omo River, Ethiopia ( Fig. 4 ).

Figures

FIGURE 1. Diagrams of nuchal plate patterns of Auchenoglanis. a) leading edge straight, b) leading edge curved. The arrow indicates the anterior end of the plates. The numbers indicate individual plates.

FIGURE 2. Diagrams of the five types of premaxillary tooth patches of Auchenoglanis. a) oblong-oval, b) round, c) square, d) tear, and e) triangle. The arrow indicates the direction of the anterior end of the patches.

FIGURE 4. Collection localities of Auchenoglanis acuticeps (black squares), A. biscutatus (black triangles), A. sacchii (open circle), and A. tchadiensis (black circles). Symbols may represent multiple collections.