Hypoptopoma ?? for Cat-eLog

[Birger]

[Silurus]

Using the recent Aquino & Schaefer paper, I'm inclined to think H. thoracatum.

[Lobosupermalo]

Hi.

This fishes was imported from Paraguay.So I think they are inexpectatum. Please note that they haven't the fat fin!

[Mike_Noren]

I tried to use Aquino & Schaeffers key to identify some Hypoptopoma in our museum collection, and I found it very difficult. Some of the characters, like the exact arrangement of small plates by the nares, was simply beyond my ability to see even though I had the fish under a stereo microscope.

Anyway, if this fish is from Paraguay, then it's likely inexspectatum; as far as I can tell it's the only described Hypoptopoma from that region.
H. inexspectatum can be reasonably easily identified by taking a head-on macro-photo of the snout: if it shows a very narrow, just a hairs width, band along the edge of the snout, then it's inexspectatum. The band is shown in figure 16 in Aquino & Schaeffer, but I'll see if I can take a photo of it for the Cat-eLog on monday. I'll also take a closer look at the very large Hypoptopoma from Paraguay we have in collection - if i remember correctly they look much like this one, with stocky bodies and strongly depressed heads.

EDIT: Presence/absence of adipose fin doesn't appear to be a particularly useful character for identifying Hypoptopoma.

EDIT2: I actually think the line on the snout is visible on the top fish:

[Birger]

EDIT2: I actually think the line on the snout is visible on the top fish:

Thats great Mike, you seem to have confirmed what it came labelled as...are you reasonably certain now, or am I still waiting until monday?

Birger

[Mike_Noren]

Thats great Mike, you seem to have confirmed what it came labelled as...are you reasonably certain now, or am I still waiting until monday?

The line on the snout is allegedly only found in H. inexspectatum, and the only species known from Paraguay is H. inexspectatum. I'll have a look at reference material, but considering how hard a time I had identifying specimens the last time I tried it's unlikely that I'll be able to say this it's NOT H. inexspectatum. So, while it's a highly tentative ID I'd say you can run with it.