Post #166265 by Jawa on 06/16/2005

Tikifish is confused, here is a graphic to demonstrate:

Dolphin or porpoise? The answers you've been looking for.
Posted: December 10 1998
By: Dave Johnston
Probably the most common question that people ask me when they learn that part of my job (when I'm not in front of this computer) involves studying harbour porpoises in the Bay of Fundy is "What is the difference between a dolphin and a porpoise?" Although this seems to be a rather simplistic topic for those readers who actively study marine mammals (and small cetaceans in particular), many of the general public don't know the difference and it appears that, until relatively recently, these words were often used interchangeably by academics as well. Dolphins and porpoises are indeed classified separately by biologists, based on a number of criteria. Although the original classification was based on morphological differences between species, modern genetic techniques also tend to support the phylogenetic, or evolutionary basis for this classification.

There appear to be at least 3 general morphological differences between dolphins (the taxonomic family Delphindae) and porpoises (Family Phocoenidae).

1: Porpoises have laterally compressed, spatulate (spade shaped) teeth while dolphins have teeth that are conical in shape.

2: Porpoises tend to have small, triangular shaped dorsal fins as compared to their dolphin relatives. The dorsal fins of dolphins are taller and tend to have a greater curvature to their trailing edge.

3: Porpoise generally have a more rounded body shape, including the lack of a distinct "beak" like those found on many species of dolphins.

[ Edited by: Jawa on 2005-06-16 13:12 ]