Fossils of bizarre, figure-8 shaped creatures called vetulicolians that
lived during the Cambrian Period have now been discovered. An analysis
of the fossils revealed these eyeless creatures sported a hollow nerve
structure called a notochord similar to today's vertebrates, including
humans. Here's a look at the oddballs. [Read full story on the bizarre Cambrian creature] Off Kangaroo Island
The 500-million-year-old swimming filter-feeders called vetulicolians
have been a mystery since their discovery more than a century ago. Now,
with the discovery of new vetulicolian fossils on Kangaroo Island off of
Australia, researchers at the University and Adelaide and the South
Australian Museum believe they understand how vetulicolians fit into the
tree of life. As improbable as it seems, these bizarre creatures are
distant relations of humans. (Credit: Copyright Katrina Kenny, 2014) A large specimen
The distinct figure-8 shaped fossil of a vetulicolian, dating back 500
million years. The largest of these fossils measures about 4.9 inches
(12.5 centimeters) in length. New vetulicolian fossils found on Kangaroo
Island reveal a rod-like structure in the tail, similar to a backbone.
This discovery reveals that vetulicolians are relatives of vertebrates,
or animals with backbones, placing them in a distant relationship with
modern humans. (Credit: University of Adelaide/South Australian Museum) Emu Bay fossil site
The Emu Bay fossil site on Kangaroo Island, Australia, is home to a
treasure trove of Cambrian fossils more than 500 million years old.
Incredibly, many of these fossils are preserved with soft tissue, such
as guts, skin and muscle. A new species of vetulicolian, Nesonektris aldridgei, was
first found here in 2009, though it took researchers three years to
discover the surprising notochord-like rod in the animal's tail.
(Credit: Diego Garcia-Bellido) Something different
A detailed look at the rod-like structure discovered in
500-million-year-old vetulicolian fossils from the Cambrian. The blocky
shape of the structure indicates that it is not a gut structure,
according to a new study published in the journal BMC Evolutionary
Biology. Instead, the structure looks more similar to modern nerve cords
known as notochords. (Credit: Diego Garcia-Bellido) How the creature lived
Photographs of the Kangaroo Island vetulicolians show notochord
structures (labeled "nc"). The labels S1, S4 and S7 indicate body
segments on the creature's tail. On the other end, "om" labels the oral
margin, or mouth of the creature. Vetulicolians likely swam through the
water column, filter-feeding. (Credit: Diego Garcia-Bellido) How the creature moved
An artist's impression of the Kangaroo Island vetulicolian swimming
near the sea surface. There are 14 species of vetulicolian known from
fossils around the world, including Southern China, Greenland and
Canada. The new species found on Kangaroo Island, Australia, is dubbed Nesonektris aldridgei.
"Nesonektris" is from the Greek for "island swimmer," and "aldridgei"
is in memory of Dick Aldridge, a geologist and vetulicolian expert at
the University of Leicester. (Credit: Copyright Katrina Kenny, 2014) Family and relations
An evolutionary tree showing the position of vetulicolians compared
with their closest relations. New research finding evidence of a primal
spinal-cord-like structure in vetulicolian fossils suggests that the
closest modern relative of these 500-million-year-old organisms are
tunicates. Also known as sea squirts, tunicates are marine animals that
anchor themselves to rocks and filter-feed off plankton. (Credit: Diego
Garcia-Bellido) The oldest animals
Vetulicolians date back to the Cambrian, making them some of the oldest
animals on Earth. During this time, diversity of life expanded
enormously in what is known as the "Cambrian Explosion." As a result,
the fossil record is full of bizarre animals that sometimes bear little
resemblance to life in the modern era. (Credit: Copyright Katrina Kenny,
2014) Fossils to study
The anterior (head) fragments of vetulicolians from Kangaroo Island,
Australia. The Emu Bay fossil site on this island preserves soft-bodied
fossils, allowing researchers a good look at some of the oldest animals
on the planet. In some fossils, gut contents are even preserved,
revealing the animal's last meal. (Credit: Diego Garcia-Bellido) Heads or tails
The tail segments of vetulicolians from Kangaroo Island, Australia. It
was in these tail segments that researchers first noticed a long,
rod-like structure that didn't match the description of the animal's
gut. (Credit: Diego Garcia-Bellido) Follow Stephanie Pappas on Twitter and Google+. Follow us @livescience, Facebook & Google+. Original article on Live Science.
Author Bio
Stephanie Pappas, Live Science Contributor
Stephanie interned as a science writer at Stanford University Medical
School, and also interned at ScienceNow magazine and the Santa Cruz
Sentinel. She has a bachelor's degree in psychology from the University
of South Carolina and a graduate certificate in science writing from the
University of California, Santa Cruz.
quinta-feira, 28 de fevereiro de 2019
The skeleton articulated
Jan Zalasiewicz enjoys Brian Switek’s exploration of
how the human scaffold — and our ideas about it — evolved.
Our bones have evolved over millions of years.Credit: Nick Veasey
Skeleton Keys: The Secret Life of BoneBrian Switek Riverhead (2019)
The
bony scaffolding beneath our skin can move us emotionally as well as
physically. In enabling our lives, yet enduring beyond them, our
skeletons challenge our understanding of ourselves. This premise
underpins Brian Switek’s Skeleton Keys, a thoughtful, engaging
meditation on the origins of the human skeleton, how it functions (or
malfunctions) and how we come to terms with our essential but unsettling
osseous framework.
Bone’s potential for physical immortality
reminds us all too vividly of our personal mortality. Switek conveys the
Grand Guignol aspects of this with suitably horrified fascination —
contemplating, say, the bones of England’s King Richard III, hacked and
broken in his final hour on the battlefield. Dinosaur bones, however
awe-inspiring, cannot chill the spine in quite the same way as the
fleshless frames of our own kind.
A ênfase é assim muito no "nosso".Switek há muito entusiasmou e escreveu elegantemente sobre os ossos de nossos parentes distantes, não menos os dinossauros.E alguns, como o monstruoso Supersaurus, são abordados neste livro.A história ainda mais antiga dos vertebrados é bem delineada desde o início, suas origens no período Cambriano, exemplificado pelo Pikaia, um organismo marinho extinto parecido com uma enguia que não tinha esqueleto, mas provavelmente possuía uma notocorda, a precursora da coluna vertebral.O Pikaia foi encontrado nos cerca de 508 milhões de anos de idade Burgess Shale, um rico tesouro descoberto no Canadá em 1909 pelo temível paleontólogo Charles Doolittle Walcott.
As outras criaturas da cornucópia Burgess - e os muitos esqueletos sofisticados, principalmente externos, então sendo conjurados por grupos de invertebrados, como os artrópodes - são mencionados apenas brevemente.Esta é uma narrativa de osso, não de carapaça, e os primeiros organismos revestidos de carapaça são significativos aqui principalmente para efetivamente empurrar os vertebrados para os lados por mais de 100 milhões de anos.O esqueleto dos vertebrados finalmente prosperou, e Switek descreve alguns passos importantes ao longo do caminho, como a forma como passou de externa para interna entre os primeiros peixes.
Further
towards our particular twig of life’s tree, dinosaurs make a guest
appearance, with legendary nineteenth-century US bone hunters and sworn
enemies Edward Drinker Cope and Othniel Charles Marsh in the spotlight.
Obsessively driven, and each burning their way through a family fortune,
they unearthed many iconic dinosaurs, such as Triceratops and Diplodocus.
There is nothing on their UK counterpart Mary Anning, although she
performed comparable palaeontological miracles in extracting
ichthyosaurs and plesiosaurs from dangerous Dorset cliffs. This nascent
scientific field had formidable female protagonists, too, working
against tremendous odds.
Close to the bone
Os próximos 100 milhões de anos, nos quais os mamíferos floresceram, são cobertos rapidamente, para chegar à bonança óssea do Pleistoceno dos depósitos de alcatrão de La Brea, em Los Angeles, Califórnia.Descrevendo-os como o mais importante sítio fóssil do planeta (que é a luta entre os paleontólogos), Switek concentra-se no conjunto de ossos humanos encontrados entre os mamutes e leões e gatos com dentes de sabre.Chamada de La Brea Woman, seus restos de 10 mil anos permitem que Switek explique as complexidades físicas e químicas do osso em geral e dos ossos humanos em particular.E é uma coisa extraordinária, permitindo resiliência e força, e contínua remodelação interna.Os esqueletos dos vertebrados, ao contrário dos dos artrópodes, não precisam ser sucessivamente mudados à medida que o animal cresce, e assim podem alcançar vastas dimensões - como na baleia azul.
This narrative is
neatly done, but the fascination exerted by human bone on human minds
lies at the book’s heart. With Switek, we visit Neolithic tombs and
medieval ossuaries, consider skull cults and muse on the bony
personification of Death. The book makes extended explorations of how
nineteenth-century anthropologists such as Samuel Morton in
Philadelphia, Pennsylvania, used skull measurements to claim the
existence of racial differences, a malign legacy that, although long
discredited in science, lingers today in apologias for racism. Switek
also describes the protracted tug-of-war between scientists and the
Native American community around the Columbia River in Washington state
over who owns the 9,000-year-old skeleton of the Ancient One, also known
as Kennewick Man (D. H. Thomas Nature531, 302–303; 2016). This is terrain most palaeontologists never navigate; Switek picks through it well.
In
the book’s coda, the narrative gets up close and personal. Switek
considers his own skeleton, and how it might follow those of the
dinosaurs into geological immortality. Switek’s deep-time focus comes
through a little too strongly, I think, in his assertion that it is
mainly our skeletons that will be left to tell of our passing. Of the
detritus that each of us casually scatters — thousands of ballpoint
pens, polyester socks, aluminium cans and so on — much is a good deal
more decay-resistant than the average cranium or femur. Our bones might
be only a small part of our ultimate legacy.
Nevertheless, as this
book shows, the skeletal side of life grips us now, and might enthral
whoever excavates our remains in the far future. As Switek ponders the
sediments in which his own bones might be fossilized, he needs to think
of larger geological processes. The sea floor off the shore of New
Orleans, Louisiana, might provide a good start: there are stagnant muds,
and local tectonic subsidence will allow the fossil to be securely
entombed. In the meantime, we should enjoy Switek’s talent for spinning
compelling tales of old bones.
