Genus Amphilius Günther

The genus is diagnosed on derived musculo-skeletal characters by Diogo (2003). These features are (1) the anterior margin of the mesethmoid is bifurcated, (2) there is a prominent medial process on the postero-medial surface of the angulo-articular, (3) the presence of a muscle-3 for the mandibular barbels, (4) the abductor profundus muscle is differentiated into a thick and a thin bundle with the thicker bundle situated anteriorly to the thinner. An additional derived feature is shared with other amphiliid genera, namely that the dorsal division of the arrector dorsalis muscle is constituted as a single mass of fibres situated on the ventral surface of the pectoral girdle.

Amphilius generally are small, soft-bodied catfishes found in rocky reaches of streams and rivers and are the least specialized members of this family. The head is depressed and soft skinned; the mouth terminal, broad with fleshy lips; and the villiform teeth are in bands along the upper and lower jaw. There are three pairs of simple barbels, a maxillary pair from the lateral corners of the mouth and two mandibular pairs on the ventral side of the lower jaw. The small eyes are without a free border, dorsal, widely spaced, and in the median third of the head. Anteriorly the body is moderately depressed becoming compressed posteriorly; the caudal peduncle is short, deep and compressed. The paired fins are large and fan-like with the first ray curved, pectinate and well padded. The dorsal fin is short-based, soft and flexible. There is a low, elongate or shorter, teardrop shaped adipose fin. Fin ray formulae are generally similar between the species and diagnostic features are more often found in terms of body proportions and features of the head. The species are variously cryptically patterned with bars, spots or marbling in shades of brown, black and cream. Sexual dimorphism is usually subtle, often only evident in mature and sexually active individuals. Seven species are recognized from the WCA region, four are new and described herein. Most have restricted distribution ranges and are uncommon in collections.