maybe can help:

Karahan A, Borsa P., Gucu A.C., Kandemir I., Ozkan E., Ak Orek Y., Acan S.C., Koban E., Togan I. (2014) Geometric morphometrics, Fourier analysis of otolith shape, and nuclear-DNA markers distinguish two anchovy species (Engraulis spp.) in the Eastern Mediterranean Sea. Fisheries Research. DOI: 10.1016/j.fishres.2014.05.009.

Dear Arzu, thank you for your reply and congrats for the nice paper.

However, we are exploring exactly the opposite pattern i.e. when you have two sharply different morphotypes (with no intermediate forms), which are currently considered two different species... but which proved to be reciprocally paraphyletic :-)