The life of Cambroraster, a new predatory species uncovered by U of T PhD student

Joe Moysiuk discusses the specialized predator, life on Earth millions of years ago

The life of Cambroraster, a new predatory species uncovered by U of T PhD student

Fossils of a new predatory species named Cambroraster have been uncovered in British Columbia by U of T PhD student Joe Moysiuk, together with a team of palaeontologists from the Royal Ontario Museum (ROM).

The animal dates back 500 million years, and is described by Moysiuk to have “a mouth apparatus that looks like a pineapple slice with teeth inside” and “rake-like claws.” This incredible discovery provides insight into the evolution of its modern relatives — including insects, crabs, and spiders.

The big discovery

Moysiuk began exploring the Marble Canyon, a site in the Burgess Shale in the Kootenay and Yoho National Parks, in the summer of 2014. The original Burgess Shale has been known for approximately 100 years but some of the newer sites, including Marble Canyon, have only recently been discovered.

Here, Moysiuk and his colleagues, led by the Richard M. Ivey Curator of Invertebrate Palaeontology Jean-Bernard Caron, found a fossil that no one recognized. “We didn’t know what to make of this thing at first; we had never seen anything like it before,” said Moysiuk.

The team nicknamed the species the “spaceship” on the spot, due to the appearance of its radial teeth in the rock, but the species was later given the scientific name Cambroraster falcatus. “As the excavations went on, it became more and more clear what we were looking at,” recalled Moysiuk.

The species was found to be a 500-million-year-old marine predator with rake-like claws and radial teeth that grew up to a foot in length. Belonging to a group called the Radiodonta, it is related to the apex predator Anomalocaris — a metre-long marine species with giant grasping claws capable of preying on fast-moving organisms. The discovery of Cambroraster shows that Radiodonta may have been far more diverse than previously thought.

Moysiuk describes two aspects that make the Burgess Shale site remarkable: its age, and the extraordinary preservation of its fossils. The site that held the Cambroraster’s fossils dated back to the Cambrian period, which is more than seven times older than the era of the Tyrannosaurus rex.

The Cambrian period was “an extremely rapid period of evolution,” noted Moysiuk. It provides paleontologists with “representatives of virtually all of the major modern groups of animals coming into the fossil record all at once.”

The Burgess Shale site also provides remarkable insight into the Cambrian ecosystem because fossils found there often contain preserved soft tissue. Because of this, researchers learn a great deal about the organisms of the Burgess Shale and get a unique window into life during the Cambrian period.

“When we think of fossils, we tend to think of things like dinosaur bones, shells, and teeth — hard parts of animals that are easily preserved,” said Moysiuk. “In the Burgess Shale we get, not only those parts, but also things like eyes, nervous systems, and even digestive tracts containing the last meal of the animal.”

The challenges of identifying a species from rock

Unlike dinosaur bones in fossils where the rock is very soft, explained Moysiuk, “these fossils are extremely hard, flat, and almost two-dimensional sheets of carbon.” The process therefore involves breaking out big blocks of rock and splitting it as finely as possible to uncover a fossil. “The fossils actually sort of form a layer of weakness in the rock, allowing the rock to split where the fossil is,” he continued.

However, the almost two-dimensional form of these fossils can make it difficult to recreate the animal in three dimensions. Researchers will peel away layers of the fossil “like the layers of an onion” in order to see what’s underneath, and to help get fossils from different angles.

“A fossil with its front sticking up in the mud looks different from one preserved at the top-up,” noted Moysiuk, “and so [by] putting this information together, we are able to reconstruct things in three dimensions — but this can be quite challenging.”

How Cambroraster can tell us about biodiversity today

Prior to the Cambrian period, the ocean floor was very low in oxygen, and any nutrients in the sediment were trapped and unable to surface. “When we get into the Cambrian, we start seeing organisms [like Cambroraster] digging deeper and deeper progressively into the sediment,” said Moysiuk, “and exhibiting more complex burrowing patterns to draw oxygen down into the sediment.”

The Cambroraster’s digging would allow decomposition of the organic matter, which recycles it back into the marine ecosystem. The species was also a specialist predator, which would have preyed on organisms buried in the sediment.

“Cambroraster is playing a role that is analogous to what a lot of modern bottom-feeding organisms play today,” noted Moysiuk. “So this is a mode of life that has persisted ever since.”

What’s next for Moysiuk and his colleagues at the ROM?

The discovery of new sites, including those in the Marble Canyon in the Canadian Rockies, has led to researchers uncovering huge collections of fossils, including several other new species other than Cambroraster. Moysiuk is interested in studying the new species of radiodonts found at these sites, as well as exploring how these species may have contributed to the evolution of modern marine biodiversity.

“There is a lot more work to be done in terms of understanding these ecosystems,” said Moysiuk, “and [the] organisms that were living in them.”

The Dawn of Life

The Royal Ontario Museum’s exhibit will travel four billion years back in time

The Dawn of Life

Last week, the Royal Ontario Museum (ROM) finalized plans to build The Willner Madge Gallery, Dawn of Life. As its name suggests, the Dawn of Life will feature fossils from the start of life about four billion years ago until the appearance of dinosaurs over 200 million years ago.

Professor in the Department of Ecology & Evolutionary Biology and Department of Earth Sciences Jean-Bernard Caron and his research team travelled to the Burgess Shale and collected some of the fossils that will become a focus of Dawn of Life.

“Without the close relationship we have with U of T, this would not be possible,” said Caron, who is also the Richard M. Ivey Curator of Invertebrate Paleontology at the ROM. “Without students, my collection would be a pile of rocks.”’

Showcasing Canada’s ancient past

The Cambrian Explosion occured 542 million years ago. This period marked the rapid appearance of diversified animals and mineralized fossils.

The Burgess Shale in British Columbia contains a myriad of fossils from the Cambrian period. In particular, the Burgess Shale is known for its intricate preservation of soft-bodied animals. Many of the fossils from this UNESCO World Heritage site provide a wealth of information that cannot be found anywhere else.

Caron initiated the Burgess Shale projects after joining the ROM in 2006, providing insight into Canada’s ancient past.

In addition to the Burgess Shale, fossils from Mistaken Point in Newfoundland, Parc national de Miguasha and Anticosti island in Québec, and Joggins Fossil Cliffs in Nova Scotia will also be on display.

Featured fossils

The fossils in this exhibit are not only relics of the past, but are also representative of Canada’s rich archaeological history.

In 1886, Canadian geologist Richard G. McConnell collected fossils from the Mount Stephen Trilobite Beds in the Canadian Rockies. McConnell ended up with a collection of trilobites, one of the earliest arthropods. But he also recovered fossils that didn’t belong to trilobites. These fossils had unusual appendages and created confusion among researchers who followed in McConnell’s tracks.

In 1892, Joseph Whiteaves described the specimen as a shrimp. In 1911, Charles Walcott found a complete version of the specimen and described it as a sea cucumber. Other researchers throughout the twentieth century described the specimen as a sponge or jellyfish.

It wasn’t until 1985 that researchers Harry Whittington and Derek Briggs described two of the species in full, one of which is Anomalocaris canadensis, a basal arthropod related to spiders and shrimp.

Anomalocaridids were large predators that dominated the Cambrian seas roughly 535 million years ago.

In the 1990s, researchers from the ROM collected several, complete Anomalocaridids specimens. And in 1996, researcher Desmond Collins described Anomalocaris canadensis in detail.

This specimen is one of many treasures that will be on display in Dawn of Life.

PHOTO BY JEAN BERNARD CARON, COURTESY OF THE ROM (Click to Expand)

Visitors will also be able to view banded iron formation — from the Nuvvuagittuq Greenstone Belt in northern Québec — which contains the earliest evidence of life on earth.

PHOTO BY DR. JONATHAN O’NEIL & PITUVIK LANDHOLDING, COURTESY OF THE ROM (Click to Expand)

At the preview last week, visitors had the chance to see Acutiramus macrophthalmus in person. The fossil is the world’s largest specimen of its kind. It’s not evident from its large size, but the 420-million-year-old specimen is a distant relative to horseshoe crabs.

PHOTO COURTESY OF THE ROM (Click to Expand)

A 370-million-year-old Eusthenopteron fish and a Xenasaphus devexus trilobite are examples of some of the other fossils that will be featured.

SRIVINDHYA KOLLURU/THE VARSITY (Click to Expand)

 

PHOTO BY BRIAN BOYLE, COURTESY OF THE ROM (Click to Expand)

Construction of the Dawn of Life is slated to begin in 2019 and the ROM hopes to open the exhibit in 2021. Meanwhile, a preview of the gallery is located on the second-floor rotunda.

Dinosaur teeth uncover evolutionary secrets

UTM paleontologists search the past to learn how mammalian teeth evolved

Dinosaur teeth uncover evolutionary secrets

UTM paleontologists, professor Robert Reisz and former PhD student Aaron LeBlanc, published studies in PLOS One and the Proceedings of the Royal Society B that shed light on the complex evolution of teeth.

In PLOS One, Reisz and co-authors published an article that discusses Changchunsaurus parvus from the ornithopod family of dinosaurs. Ornithopods are herbivorous dinosaurs. Based on fossil records, ornithopods used their beaks to rip plants from the ground and had muscles to chew through coarse vegetation.

Reisz and LeBlanc explored the importance of this species in understanding the evolution of dentition in dinosaurs and a newfound form of teeth replacement.

LeBlanc’s study in the Proceedings of the Royal Society B located points of evolutionary change in mammalian dentition and delved into how mammalian dentition has evolved over the last 300 million years.

Both studies examined the fossil record by sawing off thin slices of tissue from the desired region. These slices were then polished to create transparent samples. The resulting slice was then subjected to three-dimensional analysis and subsequent computer configuration.

Herbivorous ornithopods are often studied due to the myriad of dental innovations they developed to cope with their diet. C. parvus was specifically studied, as it precedes major innovations in dinosaur dentistry and was thought to possess an ancestral version of previously investigated structures.

The thin sections examined confirmed the function of some components of the dental network. However, they also exhibited a novel form of tooth replacement, which was essential in herbivores due to the extensive pressures of a plant-based diet.

Reisz’s study also solidified that C. parvus had the earliest known occurrence of wavy enamel. This type of enamel was previously disassociated with the ornithopod family and its discovery in C. parvus opens their phylogenetic relationships for discussion.

The results are significant. C. parvus appears at a pivotal point in the evolutionary history of the tooth and understanding its dentition better will lead to a more complete understanding of teeth in general.

LeBlanc’s study examined tooth complexity.

Researchers previously believed that mammals had the most complex form of teeth, while reptiles possessed a simpler version. This was a result of mammals having a ligamentous attachment mechanism for teeth compared to the reptilian teeth being fused directly to the jaw.

But through observing thin sections of therapsid — early reptiles — teeth, Reisz and LeBlanc observed ligamentous structures similar to mammals.

Further study of thin sections from a variety of organisms implied that teeth ligaments developed before the divergence of mammals from reptiles, and that the reptilian fused teeth arrangement is in fact due to calcification — the accumulation of solid calcium deposits — of teeth over time.

Insight into dental history allows for a more comprehensive understanding of our teeth, and the resulting development of new theories, techniques, and explanations in dentition.

Young dinosaur finding hints at evolutionary differences

U of T researcher involved in study that uncovered rare diplodocid skull remains

Young dinosaur finding hints at evolutionary differences

Diplodocids are a group of sauropods that include giants such as Diplodocus and Supersaurus — some of the longest creatures ever to walk the Earth.

Archaeologists have uncovered hundreds of fossils from this dinosaur group, but little is known about their origin or development into adult form.

In a study published in Scientific Reports, researchers including U of T PhD candidate Cary Woodruff analyzed a young diplodocid’s skull remains — unearthed in 2010 in Montana — and found that younger diplodocids may have had different diets than their older counterparts.

The skull remains, dubbed ‘Andrew,’ demonstrate that cranial dimensions did not develop on a fixed scale or at equal measures.

The dental and cranial differences between a mature and immature diplodocid can give the impression that they are of different species, but Andrew reveals that there are implications for cranial ecology as young diplodocids grow.

Woodruff and his team were able to determine specific differences between Andrew and adult skulls discovered earlier, including an extended tooth row, taller jaw bones, and peg tooth formation.

In fact, the authors state that if the fragments of the skull had been discovered separately, they would have likely been misidentified.

This is mostly because these distinct traits were common to other species — taxa — in the same clade as diplodocids, such as Eusauropoda and Macronaria. To a non-expert, it would seem strange that younger dinosaurs may horizontally integrate in taxa.

However, the researchers describe that this may be due to either recapitulation or, most likely, dietary niche partitioning between the young and adults.

Recapitulation theory suggests that an organism takes on forms of its ancestors — forms that were critical for survival in evolutionary past but are no longer needed — as it grows from embryo to adult, reaching the latest derived state during adulthood.

As such, it has been suggested that the skulls of adult diplodocids are taking the same form as their ancestors’.

The researchers in this study outline how dietary levels of specialization are what determined skull sizes, and that this is a form of recapitulation.

The younger diplodocids, like their relatives in the same clade and their common ancestors, ate more plants and lived in forested areas.

But as they got older, they gravitated to open space habitats and developed a more specific diet. Dietary specialization is the latest in the evolutionary timeline of diplodocid behavioural development, and is only found in fully mature individuals.

Woodruff explained why so many diplodocid skeletons have been discovered, but so little is known about their cranial ontogeny.

“The greatest difficulty in studying diplodocid — any sauropod — skulls are their rarity. We have loads of Diplodocus skeletons (well over 100), but fewer than 10 skulls are known. So it’s difficult to even have specimens to study in the first place,” he wrote.

The fragility of these fossils is also a significant limitation. “Dinosaur skulls are made up of dozens of thin, fragile, and delicate bones. The skull could easily get damaged or destroyed long before it’s even buried and begins the fossilisation process,” wrote Woodruff.

Some of Andrew’s bones were missing, “and those that remained were greatly squished” from being underground for millions of years. Bones can also become warped or distorted after long periods.

The work done by Woodruff and his team to draw out the cranial ontogeny and dietary habits of these animals have significant scientific implications. It reveals that diplodocid adults most likely gave birth and then separated from their young early on. It also shows us that herds were mostly segregated according to age.

The work done with Andrew highlights how the fossil record can impart indicators of behaviour and animal sociology. But the questions don’t end here.

“Andrew is not some missing link, nor does it fill in all of the remaining questions — it doesn’t even come close. Each new discovery, finding, and bit of research is like finding a piece to our puzzle. With every piece our picture becomes more and more complete,” wrote Woodruff.