How many different types of dolphins are there? And can the different types communicate with each other?

Question: How many different types of dolphins are there? And can the different types communicate with each other?
- Keywords:
  communicate,
  communication,
  diversity,
  dolphin,
  sealife
Asked by tomlowe81 to Valeria, Charlotte, Jo, Kevin, Louise on 11 Jun 2012. This question was also asked by eveve, scientificgrapefruit, katyyy, hannahhorrocks, megan98, sarahtierney99.
- Valeria Senigaglia answered on 11 Jun 2012:
  
  Well there are almost 50 species of dolphins, some lives in the sea, other in fresh waters. Some of them are called whales because are very big but they are actually dolphins (like killer whales who are dolphins).
  There are few studies on inter-specific (between different species) communication. Is very hard to study communication as we are not very good in translating from dolphin sound to human language. Moreover some dolphins have different dialects even if they belong to the same species or live in the same place!
  However I think some messages are understood by every dolphins, for example if two dolphins pet each others with the flippers, I am sure they will understand it as a sign of affection regardless of their species.

Question: How many different types of dolphins are there? And can the different types communicate with each other?