Over at her blog Jennae's Thoughts on the Paranormal...and More, Jennae has a thought-provoking post titled Beyond the Curtain, which in part addresses the issue of whether or not some cryptids might originate in other realms of existence - extra-dimensions, in other words. She suspects not, but it's a good, solid article on an issue that most definitely polarizes people into different camps.
Jennae begins as follows:
"They say that monsters don’t really come from our earth. They say that some monsters and ghosts come from other dimensions. They say that even some UFOs are not from outer space at all, but simply from another dimension. Who are they? A select few monster, ghost, and UFO hunters and theorists. It is a theory that seems to tie things up quite tidily. It makes a good explanation as to why no one can get any concrete evidence; the strange being or whatever simply slipped back into their dimension. I can certainly see the possibility of parallel realities. I bet these alternate existences can account for a lot of crazy things that happen out there. So let’s go over the whys and why nots regarding the possibility of parallel universes and the phenomena connected to them."
And here's the link to the complete article.