This plant was collected in waters connected to the Brazos River about 6" deep. It was growing in silty mud with Ludwigia spp. and some Myriophyllum. I didn't see any other plants of this kind near it and it was not connected by runners or anything.
I have no doubt Cavan or Michael will be along in no time with an ID, but if I were a betting man, I would suspect it at least belongs to family Alismataceae. I'm not as smart as them or Aaron or Zapins but at the same time this is an opportunity to test myself.
My money (not that I have any) would be on it being an Echinodorus - There are only a handful of species in the genus that are native to Texas, and of them I would probably guess E. berteroi as the most likely candidate for this plant (the leaves are kinda translucent, which is a feature of that species). But, given that there are plenty of fish farms and other ornamental aquatic businesses in the South, it's entirely possible that it's an escaped import or a hybrid thereof... after all, they even have crypts growing in parts of TX!
But yeah, definitely something out of Alismataceae, and very pretty!
We only have two Echinodorus in Texas, the less common berteroi and the very common cordifolius. It could be a submerged growing seedling of either. I'm going to assume you collected it in Hill County. You normally have to travel down to Georgetown before you start running into them, cordifolius that is, you have to go more north and west for berteroi, think Palo Pinto and then west.
I have a teacher who knows a botanist doing phd research on aquatics at A&M and I'm sending the pics to him.... The plant btw has been putting out new leaves that are nigh translucent and green since it's low light. I have a feeling if we put it in stronger lighting it'll put out red leaves again. It's growing rather fast in my tank, putting out 3 new leaves.
Texas Plant ID 
Re: Texas Plant ID 
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