Within the genus Corydoras there is a wide variation in body shape and size, particularly the head and snout. There are those that we term the 'Rounded' or 'Short nosed' group at one end of the scale and then there's the 'long nosed' or 'Snouted' species at the other. In between these two extremes are other head shapes where several species can be categorized, which is what I tend to do mainly for my own convenience. What the various shapes indicate to me is, that in all probability these species inhabit the same or very similar environments, feed in the same manor and on the same or similar types of food. This then helps when I prepare tanks for new acquisitions, by giving them the right set of conditions from the start.