Just as in the case of Wetherellus brevior, Wetherellus longior is only known from one specimen at the NHM, London, Wetherellus longior features a more elongated and narrower skull morphology compared to that of Wetherellus cristatus. This can be seen here in the final image which compares the skull length and morphology side by side. Monsch (2005) casts doubt however on whether W.brevior and W.longior some enough difference from W.cristatus and that they are in fact all from the same species.