This issue has been something I've pondered for a long time (basically
when hearing all sorts of different pronunciations of "aetosaur"), and
whether it's technically correct under various linguistic rules or not, I've
more or less come to the conclusion that all those extra a's and o's in the
Old English spellings are essentially silent (unless you have a very thick
accent!) and serve basically as markers that the following "e" is long
rather than short.
Basically it _has_ to be "LEE-laps," or else you also have to pronounce:
Are you insinuating that English has spelling rules? :-)
"palaeontology" as "PAY-lay-on-TAH-loh-jee" (instead of "PAY-lee-on...")
"_Coelophysis_" as "SOY-loh-FY-sis" (instead of "SEE-loh-FY...")
etc. For "aetosaur," I often hear "ah-EE-toh-sawr" or "ay-EE-toh-sawr," but
I've always contended it's just "EE-toh-sawr."