The Cambrian Period, which lasted from approximately 540 to 485 years ago, is best known for the Cambrian Explosion, in which an abundance of new, highly evolved species sprang up in the gene pool. A particularly unique and innovative group of new species during this time was the anomalocaridids – huge shrimp-like predators with front-facing pincers and gills that functioned as blades. They grew anywhere from 0.6 to 1.8 meters (2 to 6 feet) in length and were the top of the food chain in their Cambrian marine habitats.
But since the discovery of these predatory beasts of the past, paleontologists have been stumped by one thing: where do anomalocaridids fall in the broad scheme of things? Who are they most closely related to; whom did they evolve from, and which species today have evolved from them? A new find, described in Nature, sheds light on these questions.
Peiyun Cong from Yunnan University in Kunming, China, led a group of researchers from the United Kingdom and the United States in analysis of the remains of the 520-million-year-old anomalocaridid Lyrarapax unguispinus. Discovered in southwestern China, the three specimens of this species were almost completely preserved – muscles, brain, and digestive tract traces were all found in incredibly good shape.
L. unguispinus, Cong et al.
The brain remains were most telling – Cong and his team found that the brain was not similar to those of chelicerates – a group that includes scorpions and arachnids – in which some scientists previously placed anomalocaridids. According to the remains of its brain, the most similar creatures to L. unguispinus, it appears, are velvet worms – two families of which exist today.
Source: Cong, P., Ma, X., Hou, X., Edgecombe, G. D., & Strausfeld, N. J. (2014). Brain structure resolves the segmental affinity of anomalocaridid appendages. Nature (online).
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