Cambrian Explosion: model of an early Cambrian (Introduction)

by David Turell , Thursday, December 21, 2017, 14:56 (2529 days ago) @ David Turell

Another very complex Cambrian with parts like a horseshoe crab, and no predecessors. A refutation to Darwin theory of gradual change:

https://cosmosmagazine.com/palaeontology/meet-a-500-million-year-old-micro-monster

Habelia optata – two centimetres long and first discovered a century ago – is described in detail for the first time in the journal BMC Evolutionary Biology.

"The description, led by Cédric Aria of the University of Toronto, reveals a savage hunter that walked in the waters of the Burgess Shale around 500 million years ago. Although very distantly related to modern horseshoe crabs and scorpions, Habelia shows structural adaptations that suggest its behaviours were rather more similar to those of a very different arthropod group, known as mandibulates.

***

"And now there is Habelia optata, a vicious little beast covered in spines, with a thorax boasting five pairs of legs and a post-thorax, or tail, covered in rounded appendages probably used in respiration.

"Habelia’s head, however, is the really interesting bit. It features a complex admixture of five sets of appendages, including large plates covered in teeth, pseudo-legs covered in bristly spines, long slender branches likely to have been used to feel or sense food, and a pair of appendages towards the pack of the head thought to have been used to assist the other bits in funnelling food towards the tooth-covered business end.

“'This complex apparatus of appendages and jaws made Habelia an exceptionally fierce predator for its size,” says Aria. “It was likely both very mobile and efficient in tearing apart its prey.”

***

"Meticulous observation of the creature’s head structure revealed it to be a member of a completely different subphyla, called the chelicerates. These are so named because of the tell-tale presence of a pair of specialised appendages (called chelicerae) in the front of the mouth. Modern chelicerates include horseshoe crabs and arachnids.

"Aria and Caron believe that Habelia evolved in such a way that its body parts became adapted for use in ways that mirrored those of mandibulates – a process known as convergent evolution.

“'From an evolutionary point of view, Habelia is close to the point of divergence between chelicerates and mandibulates,” says Aria.

“'But its similarities with mandibulates are secondary modifications of features that were in part already chelicerate in nature. This suggests that chelicerates originated from species with a high structural variability.”

"The researchers suggest that the species was an active predator, stalking the Cambrian sea floor in search of prey species. One of its most likely targets, they suggest, were trilobites – small creatures covered in tough shell carapaces.

“This builds onto the importance of carapaces and shells for evolutionary change during the Cambrian explosion, and expands our understanding of ecosystems at this time, showing another level of predator-prey relationship and its determining impact on the rise of arthropods as we know them today,” says Caron."

Comment: The fact that we can look back from what exists today and spot how current phyla started tells us the Cambrian was the true start of today's bush of life. These designed animals had no predecessors. They look invented on the spot. They totally destroy Darwin's concept of gradualism in evolution. He predicted tis result if intermediate forms were not found.