Something caught my eye at the cheap table of trilobites at a Moroccan vender at a past fossil show. There were several Scabriscutellum of mediocre quality but I bought two. You can see them here. I am pretty certain these fossils are legit. One seems to have to have a clear cleft in the pygidium. There is even a small overlap of one pygidial "lobe" over the other. This is the first time I have seen such a "dramatic" mutation. I would guess that it is far more likely to be a developmental issue rather then a genetic mutation. The cleft trilobite obviously survived to its current size just fine (both approx. 4cm or 1.5 inches long). What do you think? Has anyone seen similar mutations within a species?