Aegirocassis benmoulae

Anomalocaris has always been one of my favorite Cambrian animals -- it was so weird, and it was also the top predator of the age, making it the equivalent of T. rex. The anomalocarids were also a diverse and successful group, so wouldn't you know it…it also had a distant filter-feeding cousin in the Ordovician. This is Aegirocassis benmoulae.

Aegirocassis

Isn't that beautifully bizarre? The great appendages on the front of the animal have been modified to form a filter-feeding apparatus. It was also a real monster, over 2 meters long.

You want to know more? One of the discoverers, Peter van Roy, has narrated a video in which he explains step-by-step how they reconstructed the organism from the fossils. Very educational!

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I think the most interesting thing about this particular organism is something that you didn't even touch on, Namely that it appears to be ancestral to arthropods (or, at least, a VERY close relative of a species that was). The theory being that the anomalocaridids were a bridge group between lobopods (a group whose extant species are called onychophorans) and arthropods. But, as is often the case in paleontology, some steps were missing. This big guy apparently has, in the paired rows (dorsal and ventral) on each side, structures ancestral to the typical biramous arthropod limb.

By rocketride (not verified) on 12 Mar 2015 #permalink