Hello all! I found this a few days ago while hiking in the Ischigualasto provincial park in San Juan province in Argentina.
I'm not even sure it's a fossil at all, but it was too heavy to be a bone, and it also felt (and sounded) like a rock.
I took a few pictures of it and its surroundings, marked the spot in my GPS and left it where I found it (It's illegal to collect fossils in this area) so I hope these pictures will be enough.
Thanks!