Cambrian Explosion: punctuated trillobites (Introduction)

by David Turell , Monday, January 30, 2017, 21:26 (2854 days ago) @ David Turell

Very early multicellular organisms as being found at the beginning of the Cambrian explosion about 540 million years ago. Two new organisms:

https://www.sciencedaily.com/releases/2017/01/170130111008.htm

"Researchers have identified traces of what they believe is the earliest known prehistoric ancestor of humans -- a microscopic, bag-like sea creature, which lived about 540 million years ago.

"Named Saccorhytus, after the sack-like features created by its elliptical body and large mouth, the species is new to science and was identified from microfossils found in China. It is thought to be the most primitive example of a so-called "deuterostome" -- a broad biological category that encompasses a number of sub-groups, including the vertebrates.

"If the conclusions of the study, published in the journal Nature, are correct, then Saccorhytus was the common ancestor of a huge range of species, and the earliest step yet discovered on the evolutionary path that eventually led to humans, hundreds of millions of years later.

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https://www.sciencedaily.com/releases/2017/01/170130133409.htm

"A new species of fossil has been discovered that will shed light on early animal ecosystems. Investigators discovered the new species while conducting a survey of microfossils in mudstones from western Canada. To their surprise, the samples yielded miniscule loriciferans: a type of animal so small it has been considered “unfossilizable.

"To their surprise, the samples yielded miniscule loriciferans: a type of animal so small it has been considered "unfossilizable."

"Moreover, the fossils date to the late Cambrian Period, meaning they lived around half a billion years ago. This suggests that soon after the origin of animals, some groups were adopting specialized "meiobenthic" lifestyles, living among grains of sediment on the seabed.

***

"Loriciferans are a group of miniscule animals, always less than a millimetre long, which live among grains of sediment on the seabed. They are easy to overlook: the first examples were described from modern environments as recently as the 1980s.
Dr Harvey added: "As well as being very small, loriciferans lack hard parts (they have no shell), so no-one expected them ever to be found as fossils -- but here they are! The fossils represent a new genus and species, which we name Eolorica deadwoodensis, loosely meaning the "ancient corset-animal from rocks of the Deadwood Formation."

"'It's remarkable that so early in their evolution, animals were already exploiting such specialized meiobenthic ecologies: shrinking their bodies down to the size of single-celled organisms, and living among grains of sediment on the seabed.'"

***

"The dramatic diversification of animals known as the Cambrian "explosion" is a source of fascination to many people. Working out why animals evolved when they did, and how they came to dominate almost all ecosystems on Earth, is a longstanding scientific question that affects how we think about our place in the universe."

"The scientists added that the new fossils also support a close relationship between loriciferans and another obscure group of animals (the priapulid worms), helping to piece together the tree of animal life."

Comment: These fossils are complex animals. There is still an enormous gap from the earliest fossils predating the Cambrian era.