Paleontologists headed by the University of Arizona’s Center for Insect Science announced an amazing find yesterday in the journal Nature.
Near Kunming, southwest China last year, they found beautifully preserved fossil remains of Lyrarapax unguispinus, a half-billion-year-old arthropod now thought to be far-distant kin of modern spiders, scorpions, spiny lobsters—and butterflies. The largest and most diverse animal group on Earth, arthropods like this now comprise over a million described species, over 80% of all living types of animal.
The insect, an anomalocaridid, was about 12 cm (five inches) long. A pretty grotesque little beast, this tiny ancient sea monster had body armor, compound eyes, and two spiky claws. Fossil experts have dated it from the Lower Cambrian Period, about 520 million years ago.
We reproduce its photograph here in an image captured by Dr. Peiyun Cong of Yunnan University, China, first author of the study. Dr. Nicholas Strausfeld of the University of Arizona, who headed the scientific team, provided the artist’s impression of it (above). Its Latin name means “spiny-clawed lyre-shaped predator.”
The authors of the scientific study describe the pertinent qualities of its unusual brain:
Carbon-rich areas in the head resolve paired pre-protocerebral ganglia at the origin of paired frontal appendages. The ganglia connect to areas indicative of a bilateral pre-oral brain that receives projections from the eyestalk neuropils and compound retina. The dorsal, segmented brain of L. unguispinus reinforces an alliance between anomalocaridids and arthropods rather than cycloneuralians.
In particular, the discovery resolves a mystery that has perplexed modern science for the last few decades. It may help solve the “arthropod head problem”: a longstanding embryological dispute over the segmental organization of arthropod heads. Through nearly complete specimens preserving traces of muscles, digestive tract, and brain, these researchers have found the first direct evidence that the anomalocaridid head was segmental.
“Correspondences in brain organization between anomalocaridids and Onychophora resolve pre-protocerebral ganglia, associated with pre-ocular frontal appendages, as characters of the last common ancestor of euarthropods and onychophorans. A position of Radiodonta on the euarthropod stem-lineage implies the transformation of frontal appendages to another structure in crown-group euarthropods, with gene expression and neuroanatomy providing strong evidence that the paired, pre-oral labrum is the remnant of paired frontal appendages.”
Unfortunately, our antediluvian sea monster can’t really take credit for today’s lobsters and butterflies. It’s much more closely related to the onychophorans (“velvet worms”) found in equatorial and southern-hemisphere forest litter. Dr. Strausfeld refers to these carnivorous terrestrial invertebrates as “modest worm-like animals.”
On the onychophora.com website, Dr. Georg Mayer and Ivo de Sena Oliveira connect the creature’s descendants (photo above right) with many basic questions of modern science, such as the origins of vision and color vision, evolution of mitochondrial genomes, developmental basis of animal segmentation, and bioengineering potential of its slime.