Yeah itls deffinatly not an otopharanx lithobates from that picture. One way you can tell if it is one of those is that they have 3 spots on the side of their body.
I do know what you have though. You actually have one of my favorites of the protomelas group. It is one of these two.
http://www.cichlid-forum.com/profiles/species.php?id=1359
http://www.cichlid-forum.com/profiles/species.php?id=1237
You most likely have the first one from mara rocks the they are more commonly encontured from what I have found. Either way you have a very nice fish there. Their even cooler when you have a 10in one.
Hope this helps you out.