New species of Scorpiodoras catfish described

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A new species of the thorny woodcat in the genus Scorpiodoras has been described in a revision of the genus by Brazilian ichthyologists.

Leandro Sousa and José Birindelli name the new woodcat Scorpiodoras liophysus in their study, which was published in the most recent issue of the journal Copeia. 

The study also recognises two other species of the genus as valid: S. heckelii and S. calderonensis.

Scorpiodoras heckelii (pictured above) is distinguished from congeners in having a relatively large eye (diameter 91–129% of interorbital width vs. 58–93). 

It further differs from congeners in having a simple, egg-shaped, secondary swimbladder without a terminal diverticulum (vs. secondary swimbladder absent in S. liophysus and with a terminal diverticulum in S. calderonensis), and from S. liophysus in having shallow bony scutes on the sides of the body (33–51% of body depth near the anal-fin origin vs. 61–72). 

This species is known from the Orinoco and the Negro river drainages, as well as the Amazon River drainage at and below its confluence with the Rio Negro.

Scorpiodoras calderonensis was previously considered a synonym of S. heckelii. It is distinguished from congeners in having secondary swimbladder terminally extended by an elongate diverticulum (vs. secondary swimbladder absent in S. liophysus and without diverticulum in S. heckelii).

Scorpiodoras calderonensis further differs from S. heckelii by having a relatively small eye (diameter 63–93% of interorbital width vs. 91–129) and from S. liophysus in having shallow bony scutes on the sides of the body (41–59% of body depth near the anal-fin origin vs. 61–72). 

This species is known from the upper Amazon River drainage, including the Rio Solimões and lower portions of its tributaries, such as the Juruá, Japurá, and Tefé rivers.

Scorpiodoras liophysus can be distinguished from congeners in having a simple swimbladder without a secondary bladder, and deeper midlateral bony scutes (61–72% of body depth near the anal-fin origin vs. 33–59).

Scorpiodoras liophysus also differs from S. heckelii in having a relatively small eye (diameter 58–77% of interorbital width vs. 91–129). 

This species is known from the Rio Madeira drainage, and is named after its absence of a secondary swimbladder (Greek leios meaning smooth, bald, and physa meaning bladder).

For more information, see the paper: Sousa, LM and JLO Birindelli (2011) Taxonomic revision of the genus Scorpiodoras (Siluriformes: Doradidae) with resurrection of Scorpiodoras calderonensis and description of a new species. Copeia 2011, pp. 121–140.