Lets look again at the cladogram of basic amniote relationships.
One of the richest areas to find these odd diapsids is in marine Triassic age deposits in the Alps. Tanystropheus is from marine deposits and has an absurdly long neck, with otherwise rather lizard-like proportions. Tanytrachelos is very much smaller and even more lizard-like, and comes from lake deposits in the eastern US, Newark Supergroup.