Tag: Ediacaran Period

Paleontology news for April 2020.

As you know the science of paleontology is about origins, where did life on this planet come from and how did it find its wandering way to us? Well the big story this month fills in a rather large piece to that puzzle. Fossil hunters in Australia think that they may have discovered evidence of the first animal!

As you may guess the first animal evolved during the time of the very first multi-cellular life, a period now known as the Ediacaran period some 550 to 570 million years ago, see my posts of 16June2018, 15August2018 and 22January2020. Fossils of creatures from the Ediacaran were first unearthed back in 1946 but even from the beginning evolutionary biologists had problems connecting them to later, better understood groups of animals.

The Ediacaran creature Dickinsonia costata. Is that an animal, plant or what? (Credit: Wikipedia)

In fact analysis of the Ediacaran fossils indicates that these creatures were constructed in a manner totally unlike that of any life form that exists today. One example of this is the complete lack of anything resembling a mouth, anus or digestive tract in the Ediacaran fossils leaving scientists to wonder how the creatures consumed their food and excreted their waste.

Artists illustration of life during the Ediacaran period. Very different from the animal life of today! (Credit: Science Photo Library)

Additionally the very body shape of the Ediacaran fauna is strange, paleontologists often describing them as having a ‘quilted’ pattern, something like an air mattress. Another way in which the Ediacaran creatures differ from all modern animals is that, although at first glance they may appear to possess right-left symmetry a closer inspection reveals that in fact they are not bilaterally symmetric.

Bilateral symmetry is one of the cardinal features that connects all modern animals together. While it is true that individuals are rarely right-left mirror images, you may have a small mole on your right cheek for example. In general however people have as many moles on their left sides as their right. As a species we, and other animals are strongly bilaterally symmetric.

Bilateral Symmetry is a defining factor amongst almost all living animals. (Credit: Study.com)

Looking at the image below of a member of the Ediacaran genus Dickinsonia you might say that the creature’s segments are also bilaterally symmetric. However, taking a look at the second figure below, which is a blowup of the area where the right and left segments come together, we can see that the segments are actually offset from each other in a fashion known to mathematicians as glide reflection.

Dickinsonia and how it grew! Not like any animal alive today! (Credit: Wikipedia)
Closeup of the center line of Dickinsonia. Notice how the segments do not match up but are offset from each other. This pattern is called glide reflection and is unlike anything alive today! (Credit: Wikipedia)

Glide reflection shows up in a number of Ediacaran creatures such as Spriggina, Andiva and Yorgia. For glide reflection to be so prevalent among the Ediacaran creatures is also a clear sign that the manner in which they grew must have been very different from the way modern animals grow.

A fossil of Andiva ivantsovi. It’s little wonder that paleontologists have problems trying to connect creatures like this with our modern forms. (Credit: Wikipedia)

So if the best known fossil creatures from 550 to 570 million years ago were not related to modern animals then where was our ancestor? Well in a paper published in the Proceedings of the National Academy of Science (PNAS) Professor Mary Droser and lead author Scott Evans, a recent Doctoral graduate, both from the University of California Riverside claim to have found crucial evidence of our early ancestor in rocks from the original Ediacaran region of southern Australia. Recognizing that the first animal would certainly lack hard parts that could fossilize easily, otherwise it would have been discovered by now, they searched for small impressions in the rocks that might remain after the creature had died and decayed.

What they found were numerous rice grain sized depressions, 2 to7 millimeters in length and 1 and 2.5 in width, that showed hardly any clear indication of what the creature that made them looked like. Modern technology to the rescue however as the researchers used 3D laser scanning to precisely measure the outlines of the depressions. Based on those measurements the creature that made the depressions was basically tube shaped, bilateral, and was thicker at one end, presumably the front. In other words it was basically built like us. It was an animal. See image below.

Those little depressions inside the chalk square are all that remain of the first animal. (Credit: Albany Herald)
Result of Laser scan of an impression left by Ikaria wariootia. (Credit: Geology Page)

The paleontologists gave their new species the name Ikaria wariootia where Ikara means ‘meeting place’ in the local Adnyamathanha language and Warioota is the name of a creek that runs through the Ediacaran region. The laser measurements were so precise that Evans and Droser could even make out the faint body curves made by I wariootia’s muscles which bore a distinct resemblance to those of a modern earthworm indicating both how the creature moved as well as its mode of life.

Artists impression of Ikaria warioota. (Credit: University of California Riverside)

According to Doctor Droser. “This is what evolutionary biologists predicted. It’s really exciting that what we have found lines up so neatly with their prediction.”

The evidence is growing that the best known creatures from the Ediacaran period, Spriggina, Dickinsonia and their relatives, were evolutionary dead ends leaving no descendents in our modern world. Instead the future belonged to little worm-like Ikaria wariootia, and millions of years later to us.

Paleontology News for August 2018.

Paleontology is in a very real sense the study of origins, of beginnings. Paleontologists study the history of life in order to discover when and how different kinds of living creatures came into being. This month I’d like to discuss two such origin stories. In one case the discovery of the earliest known Pterosaur, those flying reptiles who shared the ancient Earth with the dinosaurs but first some new discoveries about the very beginnings of all the animals on Earth, including you and me!

Today pretty much everybody knows that more than a billion years ago the first living creatures here on Earth were tiny, microscopic single-celled organisms like bacteria and amoeba. Sometime in the distant past some of these single celled creatures learned to live together in groups like those in a sponge. In time, although still many millions of years ago, some of the cells began to perform one function, like digesting food while other cells performed other functions like motion or grabbing food.

Groups like this, where different cells concentrated on different functions to the mutual benefit of all the cells were the first multi-cellular organisms. It is from these creatures that all of the living things see every day have evolved.

The earliest fossils we have of multi-cellular life are collectively known as the Ediacaran Biota because they were first discovered in the Ediacara region of Australia. Since their first discovery Ediacaran fossils have been found throughout the world and have been dated to between 635 and 541 million years ago.

Because these creatures lived before the evolution of hard parts like bones or bark or shell they do not fossilize well and can be very difficult to study. In some cases paleontologists cannot even tell whether a specimen is a plant or an animal. The images below show several different types of Ediacaran creatures.

Dickinsonia costata from the Ediacaran Period (Credit: Alamy)

Spriggina a fossil from the Ediacaran Period (Credit: NetMassimo)

Tribrachidium heraldicum from the Ediacaran (Credit: Yale News)

A new study published in the journal ‘Paleontology’ seeks to clear away some of the mystery in the Ediacaran Biota and definitively identify the earliest known animal. The study, co-authored by Jennifer F. Hoyal Cuthill of Cambridge University and the Tokyo Institute of Technology, boy I wouldn’t want her commute between jobs, and Jian Han of the Shaanxi Key Laboratory of early life at Northwest University in Xi’an China has provided an evolutionary link between several species in the Ediacaran period to a later species of animal in the Cambrian period (540-485 Million years ago).

The animals in question certainly look more like plants; see artist’s impression below. Known collective as the Petalonamae because of their petal like branches only close examination of the anatomic details in the fossil remains show that the animals are in fact more highly evolved relatives of the sponges. The image below shows a fossil from the Ediacaran period on the right while the fossil  that belongs to the Cambrian is on the left.

reconstruction of a Petalonamae(Credit: Jennifer H. Cuthill)

Ediacaran Fossil (r) compared to Cambrian descendent (l) (Credit: Jennifer H. Cuthill)

The results of the study by Doctors Cuthill and Han reveal some of the details of how the animal kingdom itself came into being. A rather important chapter in the history of life.

 

Another chapter in the history of life deals with those flying reptiles, the pterosaurs who filled the sky during the time of the dinosaurs. Now a new species has been identified in fossils unearthed in the state of Utah. At an estimated age of 210 million years old the new pterosaur is some 65 million years older than the previous oldest known flying reptile.

The new species has been named Caelestiventus hanseni by its discoverer Professor Brooks Britt of Brigham Young University. While the specimen was not yet fully grown it already had a wingspan of a meter and a half. The images below show first the almost perfectly preserved skull of C. hanseni and below that an artist’s impression of what the pterosaur might have looked like.

Skull of Caelestiventus hanseni (credit: Nate Edwards)

Caelestiventus hanseni (Credit: Michael Skrepnick)

Thanks to the work of dedicated researchers like Doctors Cuthill, Han and Professor Britt we are slowly, bit by bit filling in the missing pages to the story of life on Earth.