There are loads of different 'plecs' that look fairly similar to common plecs; yours could be small species, like bristlenoses, or they could be juveniles or even possibly stunted, if they've been kept in too small a tank.
The only way to tell for certain is for you to post some pics of your fish (you need to upload them to a hosting site, like Flickr or Photobucket and post the IMG code into your post) and we can try and identify it/them for you.