Translucent "leaves" with dots Appeared today

[yourendofdays]

These appeared in my tank today coming out of the sand. Look like almost clear leaves or fans with dots on them. Nothing new added in a couple weeks, which was two good sized nassarius snail's (one of which I saw earlier the siphon of sticking up from the middle), a hammer, and a couple of astrea snails.
I saw an old post on here of someone who had them, but with no answers. Any clues?

 

[Goaway]

These could be a type of vase tunicates. I don't know the actual species, but enjoy them while they last. I've never seen them last more than 6 months.

 

[taricha]

whoa, those are cool. and they just sprung up in 1 day. wild.