Identificaciones de holland

This shell had me confused, as it looks like a big, inflated Quadrula nobilis. Until I saw the interior, that is. It is very different in outline from specimens of A. confragosus found in other parts of Texas, but looks very much like some specimens from the upper Mississippi drainage. It might have been a hitchhiker on a fish that was stocked in Lake Corpus Christi. 118mm

Knobs on beak are alternating like Obliquaria reflexa. I've only seen this on these two species and juvenile specimens of Plectomerus dombeyanus.

My first thought was Sharp-shinned, but on reviewing photos some seemed to lean more Cooper's to me, nonetheless the tail is shorter and more square in all photos. And in the 3rd photo you can see the helmet appears to extend to the nape.