It could be that the biology of these creatures are drastically different to the traditional categorizations of "mammal" and "reptile" as we have back in our dimensions. Some form of evolutionary adaptation that would make it beneficial for all creatures to lay eggs as opposed to giving live birth.

[Probably has something to do with inter-species breeding. But Egon perks up at what Ray says, completely ignoring the alarm in Venkman's voice.]

A radio tower? I'd like to get a recording of any EVPs in and around the site--the radio waves may pick up and amplify the voices within the area. This could be a crucial step in deciphering the speech of the ghosts in this dimension.