Greetings, I have a mountain bike with a Selle San Marco Ponza Power Saddle that I find super comfy and awesome.
I recently bought a road bike with what I think is a women's saddle on it, it's an old beat specialized saddle. It feels like its trying to pull my legs apart at the hips. It's much wider than the one on my mountain bike.
How do I go about looking for a saddle shaped similarly to the one on my mountain bike? are saddles categorized by shape at all?
Thanks.

Saddles can be categorized by these attributes, in roughly descending order of importance: butt width (width at the widest point), width between the thighs, length, profile contour (flat or scooped), contour under the butt (flat or rounded), side skirts (present or absent), and thickness and density of padding. For instance, my profile is medium width at the butt, kinda narrow between the legs, shallow scooped profile, long, flattish under the butt, side skirts, and firm dense padding. I can pretty much look at a saddle and tell if it will work for me. My favorites are Bontrager's Serano (medium width) and Selle Italia's 1990 Edition Flite.

Determine your saddle type and look for those with matching attributes.

Take your "Selle San Marco Ponza Power Saddle" off your bike and take it to the Local Bike Shop with you. You should be able to find one very similar in width and shape. Don't hesitate to ask the employees for help.