ulmus

While some characteristics look like elm, it's not any I'm familiar with nor is it common here. Any idea of species?

Pretty sure stob nailed it. As to specific species, looks like an American elm. Maybe one of the vase shaped cultivars perhaps.

John

given location doubtful it was planted, making the possibility of cultivar unlikely.

if i had to guess, i'd opt for u. pumila bit there are a number of possibilites i'm not familiar with in the southland. also possible is the fact that a chance seedling could be have some mixed parentage. combine with variation within a species from a roll of the genetic dice...

any seeds?

Typical Ulmus americana ssp. Floridana. It is native all the way to south Florida.

Pictures I'm seeing of americana bark seem to be distinctly ridged striations whereas this seems longitudinally patchy. Also, the leaves seem rather small. The leaves and branches seem like pumila, but the branching structure seems thick and full. I grew up with pumila in the yard and remember it as being wildly branched and not all that dense. If americana, I wonder its long term outlook. This is the first time I've seen this tree here in Florida.

Ulmus americana is locally abundant in central FL (I see a lot of it in Volusia County, a fair amount in Hernando - as wild trees, not planted). That's what it looks like to me.