I've already pointed out its unique characteristics (pleurocoels
in sacral vertebrate, pneumatic formina in the nasal, etc.)
That's the correct answer. If *E.* were a direct ancestor of anything known,
each of these features would have to have disappeared -- that's one extra
step for each. Not parsimonious. By definition, paleontology is a science,
so "the majority of paleontologists" uses Ockham's Razor.
You can also use probabilistic arguments. Imagine the diversity of life
today, and imagine the amount of time involved (...good luck). How likely is
it that any two of the exceedingly rare fossils would happen to be an
ancestor-descendant pair?