A new genus and species of a weakly armoured plec has been described from the upper Mazaruni River in northwestern Guyana.
Jonathan Armbruster and Donald Taphorn name the new plec Paulasquama callis.
The head and body of most plecs are covered with bony plates, with only the belly, lower surface of the head and the area around the fins lacking plates. Paulasquama differs from most plecs in lacking bony plates in two oval areas on the top of the snout, and the bony plates below the dorsal fin being greatly reduced in size. In addition, thick skin covers much of the body of the catfish (which is unusual for a plec).
Paulasquama callis was collected from a swift stream with clear water having a slightly black tint. The substrate consisted of polished cobble and gravel.
The generic name comes from the Latin paulus, meaning small, and squama, for scale armor, in reference to the small plates located in the dorsal series just below the dorsal fin. The species is named after the Latin callis for a stony, uneven, narrow footway, in reference to the narrow plated area between the two oval, naked patches on the snout.
The authors hypothesise that the numerous waterfalls in the drainages of the Pakaraima Mountains severely limit upstream migration and isolate the upstream regions. This would allow unique fishes like Paulasquama to evolve or to persist there.
For more information, see the paper: Armbruster, JW and DC Taphorn (2011) A new genus and species of weakly armored catfish from the upper Mazaruni River, Guyana (Siluriformes: Loricariidae). Copeia 2011, pp. 46–52.