A collaborative study found that East Coast estuarine dolphins are a separate species, distinct from the offshore form of common bottlenose dolphins.
The scientists collected DNA and morphological data from tissue samples, skulls, and vertebral columns from dolphins that stranded along the East Coast between 1966 and 2011.
https://www.fisheries.noaa.gov/feature-story/bottlenose-dolphins-along-east-coast-proposed-be-different-species