Research team finds new explanation for Cambrian explosion

[Dave]

Tank's mention of the HAF facebook page led me to look at it. And I found the following article that I think fascination - potentially gills in many of the gaps in my understsnding of the Cambrian Ecplosion.

Around 520 million years ago, a wide variety of animals burst onto the evolutionary scene in an event known as the Cambrian explosion. In perhaps as few as 10 million years, marine animals evolved most of the basic body forms that we observe in modern groups.
The event has sparked fierce debate all the way back to Darwin. Some paleontologists see the Cambrian explosion as a real, astonishing episode of unprecedented, fast evolution. Others suggest it is a false artifact of an unreliable fossil record.
Now work published in the American Journal of Science shows that these competing theories can be unified by the geography of Cambrian Earth, as it underwent a wholesale lurch that clustered most of Earth's continents around the equator.

Read more at: https://phys.org/news/2016-02-great-secrets-earth-evolution.html#jCp

[OldGit]

Ah, but what made it lurch?  These scientists think they're so clever, but they haven't solved geolurching yet, nor ever will.

[Dave]

Ah, but what made it lurch?  These scientists think they're so clever, but they haven't solved geolurching yet, nor ever will.

True.

I know what makes me lurch - perhaps the world got drunk and slipped off its axis?

[Ecurb Noselrub]

Ah, but what made it lurch?  These scientists think they're so clever, but they haven't solved geolurching yet, nor ever will.

We've know what made it lurch for a long time - Lurch.  https://en.wikipedia.org/wiki/Lurch_(The_Addams_Family)

[Recusant]

A whole new trove of Cambrian fossils (may end up rivalling the Burgess Shale) has been found in China. A couple of stories about it:

"Spectacular new fossil bonanza captures explosion of early life" | National Geographic

This fossil Leanchoilia preserves fine anatomical details, including its largest appendages.
Image Credit: Ao Sun

A wealth of ancient remains found by chance on the banks of a river in China are some of the most astoundingly preserved fossils now known on Earth, researchers report today in the journal Science.

The 518-million-year-old site, called Qingjiang, joins just a few places around the world where fossil preservation is so extraordinary, it captures even soft-bodied animals. Called Lagerstätten, these special types of deposits include Canada's famous Burgess shale, which dates to 507 million years ago, and China's Chengjiang locality, which formed at about the same time as Qingjiang but in shallower waters.

"Most fossil localities throughout all of time are going to preserve the shelly things, the hard things ... [but] what these localities give you is anatomy," says Harvard paleontologist Joanna Wolfe, an expert on Cambrian life who wasn't involved in the study. "These are the best of the best."

So far, researchers have identified 101 animal species in the remains, and more than half of them are brand-new to science. "I can see a bright future," says lead study author Dongjing Fu, a paleontologist at Northwest University in Xi'an, China. "Qingjiang will be the next Burgess shale."

[Continues . . .]

"'Mindblowing' haul of fossils over 500m years old unearthed in China" | The Guardian

A "mindblowing" haul of fossils that captures the riot of evolution that kickstarted the diversity of life on Earth more than half a billion years ago has been discovered by researchers in China.

Paleontologists found thousands of fossils in rocks on the bank of the Danshui river in Hubei province in southern China, where primitive forms of jellyfish, sponges, algae, anemones, worms and arthropods with thin whip-like feelers were entombed in an ancient underwater mudslide.

The creatures are so well preserved in the fossils that the soft tissues of their bodies, including the muscles, guts, eyes, gills, mouths and other openings are all still visible. The 4,351 separate fossils excavated so far represent 101 species, 53 of them new.

"It is a huge surprise that such a large proportion of species in this fossil assemblage are new to science," said Robert Gaines, a geologist on the team from Pomona College in Claremont, California. The fieldwork was led by Xingliang Zhang and Dongjing Fu at Northwest University in Xi'an, 700 miles (1,127km) south-west of Beijing.

[Continues . . .]

[Tank]

*drools*

[Caliasseia]

Meanwhile, I think it apposite to mention here, that the oldest multicellular eukaryote fossil pre-dates the Cambrian by 700 million years.

Bangiomorpha pubescens is a fossil alga. Dated to 1,200 million years before present. This pre-dates the Neoproterozoic (the "Snowball Earth" era) by 200 million years. The paper describing the holotype is this one:

Bangiomorpha pubescens n. gen., n. sp.: Implications For The Evolution Of Sex, Multicellularity, And The Mesoproterozoic/Neoproterozoic Radiation Of Eukaryotes by Nicholas J. Butterfield, Palaeobiology, 26(3): 386-404 (2000) [Full paper downloadable from here]

Abstract.—Multicellular filaments from the ca. 1200-Ma Hunting Formation (Somerset Island, arctic Canada) are identified as bangiacean red algae on the basis of diagnostic cell-division patterns. As the oldest taxonomically resolved eukaryote on record Bangiomorpha pubescens n. gen. n. sp. provides a key datum point for constraining protistan phylogeny. Combined with an increasingly resolved record of other Proterozoic eukaryotes, these fossils mark the onset of a major protistan radiation near the Mesoproterozoic/Neoproterozoic boundary.

Differential spore/gamete formation shows Bangiomorpha pubescens to have been sexually reproducing, the oldest reported occurrence in the fossil record. Sex was critical for the subsequent success of eukaryotes, not so much for the advantages of genetic recombination, but because it allowed for complex multicellularity. The selective advantages of complex multicellularity are considered sufficient for it to have arisen immediately following the appearance of sexual reproduction. As such, the most reliable proxy for the first appearance of sex will be the first stratigraphic occurrence of complex multicellularity.

Bangiomorpha pubescens is the first occurrence of complex multicellularity in the fossil record. A differentiated basal holdfast structure allowed for positive substrate attachment and thus the selective advantages of vertical orientation; i.e., an early example of ecological tiering.More generally, eukaryotic multicellularity is the innovation that established organismal morphology as a significant factor in the evolutionary process. As complex eukaryotes modified, and created entirely novel, environments, their inherent capacity for reciprocal morphological adaptation, gave rise to the ''biological environment'' of directional evolution and ''progress.'' The evolution of sex, as a proximal cause of complex multicellularity, may thus account for the Mesoproterozoic/Neoproterozoic radiation of eukaryotes.

This fossil has been known about in scientific circles for nineteen years.

[Ecurb Noselrub]

So, those Bangiomorpha have been banging for over a billion years. 

[Caliasseia]

The fun part is, that's why they were given that name

[Ecurb Noselrub]

Seems to me that once life got to the multicellular eukaryote stage that things were well on their way to the astounding diversity that we see today.  The pieces were all in place for natural selection to work its magic.