Name that Cetacean

We encountered this small pod of cetaceans a little while ago at Isla Cerralvo near the dive site of La Reyna. We never got close enough to make a good identification, but did get a few shots through a long telephoto lens. The general consensus on the boat was that these were not dolphins based on their behavior and fluke morphology, but beyond that, we were at a loss. Being an invertebrate nerd, mammal identification isn’t my forte, but I’d be interested to hear if anyone can help make an id, or point me to a resource for identifying cetaceans by their flukes and dorsal fins. A few people on board suggested that they might be short finned (Pacific) pilot whales Globicephana macrohynchus. If anyone wants to take a crack at it, please do! If you click on the picture, you will be able to see a larger image.