German ichthyologists Andreas Dunz and Ulrich Schliewen have described two new species of the African characiform genus Nannocharax from the Cross River drainage in Cameroon.
The descriptions of the two new species, named Nannocharax zebra and N. usongo, are published in a recent issue of the journal Zootaxa.
Nannocharax zebra is distinguished from congeners by a combination of the following characters: distance between posterior border of the anus and the articulation of first anal-fin ray 2.2"3.8 % of standard length, 39"43 lateral line scales, 12"13 anal-fin rays, depth of caudal peduncle 55.9"63.8% of body depth and 11.3"15.2% of standard length.
This species is named after its striped colour pattern and according to the authors, the type material was collected ...inshore in areas of relatively calm water among fine twigs of a fallen tree...Specimens sometimes rested on the fine twigs, but mostly were seen moving or hovering in the free water column in a water depth of approx.50"100 cm (between the twigs), well above the bottom which consisted of leaf litter, sand and fine detritus.
Nannocharax usongo is distinguished from congeners by the distance between the posterior border of the anus and the articulation of first anal-fin ray 0.9"1.9% of standard length, 7"11 blotches along the lateral line often coalescing to form a wide black band, and 7"12 small blotches along the back.
This species is named after conservation biologist Leonard Usongo, and were collected swimming on rotten logs in areas of swift current.
For more information, see the paper: Dunz, AR and UK Schliewen (2009) Description of two new species of Nannocharax Gunther, 1867 (Teleostei: Characiformes: Distichodontidae) from the Cross River, Cameroon. Zootaxa 2028, pp. 1"19.