Juvenile Anomalocaris from Nevada

Description: This is a juvenile example of one of the “Terrors Of The Cambrian” known as Anomalocaris. The members of this group of enigmatic creatures are known from Asia, Australia, Europe, and North America, and are thought by many to be closely allied with the Arthropoda, a position not held by all researchers. The spiniferous grasping appendages are strongly suggestive of its carnivorous habits; some trilobites from Utah bear evidence of bite marks that have been attributed to its near relative Anomalocaris nathorsti. This example comes from a soft-bodied preservation site known for some ten years. Two species are currently known; A. pennsylvanica and A. cf saron. The fact that the cranidium of a trilobite identified as Eokochaspis has been found at the same level places it in the slightly younger strata that houses A. cf saron. Both horizons are somewhat older than the celebrated Burgess Shale of British Columbia. A few examples in a near complete state have been found, but those are all four to five times the size of this one at minimum. To my knowledge this is the first time a juvenile of this taxon has been offered. The flattened lobes by which this enigmatic creature propelled itself in search of prey, and its large eyes are readily apparent, The grasping appendage is only visible as a faint trace. It was either not preserved or still buried within the matrix. I know from examples I have had from Chengjiang that as these animals grew their appendages became more robust, possibly indicative of a change in diet with age. See my other examples for an Anomalocaris grasping appendage of what was obviously a much larger specimen.

Reference: Journal of Paleontology, 77 (4), 2003, pp 674-690.