Category: Palaeontological articles

Chinese Fossil Primates Unravel Evolutionary Puzzle

Ancient Asian Primates Decimated by Climate Change

The lineage of primates that led to the monkeys, the apes and eventually the hominins (that’s us), originated in Asia.  Palaeoanthropologists and palaeontologists tend to agree on this as the known fossil record suggests a Far Eastern evolutionary heritage for our distant ancestors.  However, there is a conundrum, if the anthropoids (those flat-faced monkeys that led to the apes and ourselves), evolved in Asia, then why didn’t this evolutionary line continue and lead to higher apes and hominins from Asia?

The fossil record indicates that the earliest anthropoid fossils date from 45 million years ago (Asian fossil discoveries).  In African strata some seven or eight million years younger, the first fossils of African anthropoids are found.  We can conclude from this fossil evidence that the anthropoids first evolved in Asia, only making their way to Africa around 38 million years ago, with the hominins evolving something like 33 million years later, but only in Africa, so what caused the Asian anthropoids to stall?

Thanks to some remarkable fossil finds from China, scientists have solved this primate puzzle, it seems that dramatic climate change some 34 million years ago, nearly wiped out Asian primates, decimated populations and rendered much of that continent as “no go” areas for our distant cousins.

Ancient Teeth and Bones Provide an Important Breakthrough in Our Understanding of Primate Evolution

Fossil jaws and teeth of ancient Chinese primates.

Different types of ancient primate from southern China identified from their fossilised jaws and teeth.

Picture Credit: Chinese Academy of Sciences

The picture above shows the different types of fossil teeth and jawbone used by the scientists to identify new species of Asian Oligocene primates.

In a study published in the journal “Science”, researchers from the University of Kansas in collaboration with colleagues from the Chinese Academy of Sciences, report on the identification of six new species of primates from a site in southern China.  Described as a “mother lode”, these extremely rare and precious fossils shed light on how some Asian primates survived the global cooling event that marked the end of the Eocene Epoch.

Eocene to Oligocene Transition (EOT)

The end of the Eocene Epoch is marked by a significant extinction event.  It may not have been as devastating as the end Cretaceous extinction that led to the demise of something like 70% of all large terrestrial animals, but nonetheless, there was a considerable amount of faunal turnover with many long-established genera (such as the early whales), becoming extinct.  Some 34 million years ago, the Earth cooled dramatically.  Global temperatures fell from an average of around 21 degrees Celsius to around 16 degrees Celsius.  Scientists remain uncertain as to the cause of the cooling, although there was considerable tectonic plate activity, volcanism and a number of extraterrestrial impacts during the Late Eocene.  Some studies have indicated a fall in atmospheric carbon dioxide at this time.  This “greenhouse gas”, so feared today, because of its affect on global warming, may have been reduced in the atmosphere to such an extent that the Earth entered a phase of dramatic cooling.  It is at this time that Antarctica began to change into the frozen wasteland we know today.

As the Earth grew colder so the tropical forests shrank and the available habitat for Asian primates was greatly reduced, the six newly described species were part of an ecosystem that clung on in southern China, an area where a tropical climate still persisted.

Commenting on the significance of this decade long study, co-author of the scientific paper, K. Christopher Beard, (senior curator at the University of Kansas Biodiversity Institute) stated:

“Primates like it warm and wet, so they faced hard times around the world — to the extent that they went extinct in North America and Europe.  Of course, primates somehow survived in Africa and southern Asia, because we’re still around to talk about it.”

The Key to Understanding the Evolution of Primates

As anthropoid primates first appeared in Asia, these new fossil discoveries help scientists to understand the fate of primates on that continent, which is fundamental to understanding early primate and ultimately ape evolution.

Senior curator Beard added:

“This has always been an enigma.  We had a lot of evidence previously that the earliest anthropoids originated in Asia.  At some point, later in the Eocene, these Asian anthropoids got to Africa and started to diversify there.  At some point, the geographic focal point of anthropoid evolution — monkeys, apes and humans — shifted from Asia to Africa.  But we never understood when and why.  Now, we know.  The Eocene-Oligocene climate crisis virtually wiped out Asian anthropoids, so the only place they could evolve to become later monkeys, apes and humans was Africa.”

Working with colleagues from the Chinese Academy of Sciences (Institute of Vertebrate Palaeontology and Palaeoanthropology), specifically Xijun Ni, Qiang Li and Lüzhou Li, the researchers were able to shift through the 34 million-year-old sediments to find teeth and jaw fragments that enabled them to erect six new species.  The fossils were recovered from the upper part of the Caijiachong Formation, Yuezhou Basin, Yunnan Province, through a combination of careful site mapping and scree washing.  It seems that whilst much of Asia became inhospitable for primates, this part of China retained tropical forest so a number of species ended up being crowded into a limited space.

A List of the Six New Species of Primate Named

  1. Yunnanadapis folivorus (pronounced You-nan-ah-dap-is) a member of the Strepsirrhini (lemurs).  In the fossil teeth photograph above Y. folivorus is A.
  2. Yunnanadapis imperator (pronounced You-nan-ah-dap-is) a member of the Strepsirrhini (lemurs).  In the fossil teeth photograph above Y.  imperator is B.
  3. Laomaki yunnanensis (pronounced Lay-oh-ma-key) a lemur-like primate (Strepsirrhini).  In the photograph of the fossil teeth above L. yunnanensis is C.
  4. Gatanthropus micros (pronounced Gat-anthro-pos) another lemur-like primate.  In the fossil teeth picture above G. micros is D.
  5. Oligotarsius rarus (pronounced Olee-go-tar-see-us) the only member of the Tarsiidae (Tarsiers) described from this location.  O. rarus is represented by E in the fossil teeth picture above.
  6. Bahinia banyueae (pronounced Ba-hin-nee-ah), the only anthropoid identified, superficially similar to today’s marmosets, represented by F in the fossil teeth photograph above.

Differences in Oligocene Primate Faunas

The team’s research suggests that the Eocene-Oligocene transition (EOT) led to completely different primate faunas in Asia compared to Africa and the Near East.  In Africa, the anthropoid primates radiated, diversified and became dominant.  However, in Asia, it was the lemur-like primates the Strepsirrhini that seem to have dominated.  The EOT acted as an evolutionary filter dramatically altering the evolution of primates around the world.

The EOT Acted as an Evolutionary Filter Changing Primate Evolution

Global cooling changed primate evolution.

Changing Primate Faunas due to Eocene to Oligocene transition.

Picture Credit: Chinese Academy of Sciences

The EOT changed the evolutionary history of the primates, acting as a filter.  When the composition of early Oligocene primate faunas of Asia and Afro-Arabia are compared, we see that in Asia it was the lemur-like primates (Strepsirrhini) that rose to dominance, whereas in Afro-Arabia, the lemurs became much rarer and it was the anthropoid apes that diversified and became prominent.

The Rare Oligotarsius

Tarsier fossils are incredibly rare in the fossil record, and very little is known about the evolution of the Tarsiidae, the trivial name of O. rarus recognises this.  The teeth of Oligotarsius are very similar to modern tarsiers found today in Indonesia and the Philippines.  This suggests that extant tarsiers are little changed from their ancient ancestors.

Tarsiers – A “Living Fossil”

An extant tarsier.

A photograph of a modern tarsier, described as a “living fossil”.

Picture Credit: University of Kansas/Andrew Cunningham

Dr. Beard explained:

“If you look back at the fossil record, we know that tarsiers once lived on mainland Asia, as far north as central China.  The fossil teeth described in this paper are nearly identical to those of modern tarsiers.  Research shows that modern tarsiers are pretty much living fossils, those things have been doing what they do ever since time immemorial, as far as we can tell.”

A Vulnerability of All Primates?

This new study underscores a vulnerability of perhaps, all primates, that is how they cope when there is dramatic climate change.  The global cooling of the EOT altered primate evolution and transformed the primate faunal mixes of both Asia and Africa.  The EOT is an opposite climate effect to what we are experiencing today.  Thirty-four million years ago the world cooled, today people are very concerned about global warming, the key point is this, whether the climate warms or grows cold, primates seem to be more sensitive to a changing world than other mammals.  This could mean very bad news for our own species.

Food for Thought

It is a sobering thought, but what if the Eocene-Oligocene cooling had not taken place?  Asian anthropoids would have continued to evolve and diversify, potentially with far-reaching consequences for all primates, including hominins and our own species.  Homo sapiens (that’s us), evolved in Africa some 220,000 years ago, however, had this ancient cooling not occurred, the outcome in terms of anthropoid and ultimately human evolution could have been very different.

For an article on potentially the oldest primate: The Oldest Primate To Date?

To read about Miocene Tarsiers from Thailand: Miocene Tarsier Fossils from Thailand

World’s First Mass Extinction Engineered by Animals

Ediacaran Faunal Out Competed by Newly Evolved Animals

A remote fossil site in Namibia has helped strengthen the theory that the fauna of the Ediacaran was unable to survive the radical “re-engineering of marine ecosystems” that resulted with the evolution of more advanced biological organisms.  Newly evolved metazoans (animals that have three types of tissue layer in the embryo and are multi-cellular), altered the marine environment so much that most of the older, largely immobile, species that had dominated the Ediacaran geological period died out.

A Late Precambrian (Ediacaran) Marine Environment

Ediacaran marine life.

Life in the Ediacaran.

Picture Credit: John Sibbick

The Ediacaran geological period is defined as the last geological period of the Proterozoic (early life), it lasted from around 635 million years ago to 542 million years ago and this geological period saw the emergence of a diverse variety of soft-bodied multi-cellular creatures, most of which have no living descendants today.  The ecosystems that existed were very simple with short food chains, multi-cellular life was bizarre with many organisms shaped like discs, tubes or fronds.

Towards the end the Ediacaran more advanced and crucially mobile organisms began to evolve.  Food chains became more complicated with the evolution of active predation amongst organisms.  These new species were “ecological engineers” who changed the environment in ways that made it more and more difficult for Ediacaran organisms to survive.  That is the conclusion of the research team which studied the Namibian fossil remains.

Assistant Professor Simon Darroch Searching the Namibian Site for Fossils

Fossil hunting (Namibia)

Searching for fossils dating from the Ediacaran (southern Namibia).

Picture Credit: Sarah Tweedt, Smithsonian Institution

Writing in the journal “Palaeogeography, Palaeoclimatology, Palaeoecology”, the scientists, which include Simon Darroch (Assistant Professor of Earth and Environmental Sciences at Vanderbilt University located at Nashville Tennessee), report that they have found one of the best-preserved examples of a mixed community of Ediacaran and metazoan organisms preserved in strata from the Zaris sub-basin of southern Namibia.

The Biota Replacement Model

Palaeontologists had predicted that evidence would be found in the fossil record to indicate ecosystems dominated by Ediacaran organisms being replaced by ecosystems dominated by organisms whose fossil record persist into the Cambrian and beyond.  The Namibian fossils provide the best evidence yet of a close ecological association between these distinct types of life-form.

Assistant Professor Darroch explained:

“Until this, the evidence for an overlapping ecological association between metazoans and soft-bodied Ediacaran organisms was limited.  Here, we describe new fossil localities from southern Namibia that preserve soft-bodied Ediacara biota, enigmatic tubular organisms thought to represent metazoans and vertically oriented metazoan trace fossils.  Although the precise identity of the trace makers remains elusive, the structures bear several striking similarities with a cone-shaped organism called Conichnus that has been found in the Cambrian period.”

Conichnus Trace Fossils from Namibia – Evidence of Biota Replacement

Conichnus trace fossils (Namibia).

Conichnus burrows are trace fossils. The surface bumps represent vertical tubes that were originally occupied by anemone-like animals that may have fed on Ediacaran larvae

Picture Credit: Vanderbilt University/Darroch

Conichnus is an ichnogenus (known only from trace fossils), that may have been some form of anemone that fed on Ediacaran larvae.  The scientists also report that they have found strands of Ediacaran frond-like organisms with animal fossils preserved in place coiled around their holdfasts.  The Namibian fossil material provides a snapshot of a transitional ecosystem prior to the Cambrian explosion which led to the evolution of much more modern looking food chains.

Assistant Professor Darroch stated:

“Both animal burrows – ‘trace fossils’ – and the remains of animals themselves sharing the same communities, lets us speculate about how these two very different groups of organisms interacted.”

Lessons for Today

Although the research team are studying the remains of organisms preserved in rocks that were laid down more than 540 million years ago, the biota replacement model that these fossils seem to confirm has relevance for our planet today.  Some of the fossil strata shows the preserved body fossils of a bizarre metazoan called Shaanxilithes, these fossils are coiled found the anchoring, trace fossil (a holdfast) of a frond-like organism),

Shaanxilithes Fossils (Ediacaran Strata – Namibia)

Signs of Late Ediacaran biota replacement.

Shaanxilithes are odd, annulated and ribbon-like fossils that start showing up near the end of the Ediacaran period. In this fossil they are wrapped around Aspidella holdfasts.

Picture Credit: Vanderbilt University/Darroch

Simon explained:

“There is a powerful analogy between the Earth’s first mass extinction and what is happening today.  The end-Ediacaran extinction shows that the evolution of new behaviours can fundamentally change the entire planet, and today we humans are the most powerful ‘ecosystems engineers’ ever known.”

This research entitled: “A mixed Ediacaran-metazoan assemblage from the Zaris sub-basin, Namibia”, builds on an earlier scientific paper published last year that examined a large number of animal burrows preserved in the Namibia rocks that were interpreted as representing the fossil record of a community under stress.

The Disc-Like Structures Represent the Holdfasts of Ediacaran Organisms

Trace fossils (Aspidella).

The disc-like fossils are the preserved remains of holdfast structures used by the Ediacaran species Aspidella that went extinct about a million years after these individuals died and were preserved.

Picture Credit: Vanderbilt University/Darroch

The picture above shows the preserved remains of several disc-like fossils in the Namibian strata.  These have been interpreted as the holdfast, anchoring structures of the fern-like Aspidella.  Once thought to be an ancestral jellyfish, at the time it was first studied, it was the first Precambrian body fossil to have been formally scientifically described.  These disc shapes are now interpreted as trace fossils, examples of the benthic, immobile fauna of the Ediacaran, that was being replaced by more complex and mobile metazoans.

Stirring up Sediments

Hunting and eating the Ediacaran fauna might not have been the only destructive behaviour of the more complex mobile organisms that represented emerging fauna that would dominate the Cambrian.  The researchers also point out that mobile Cambrian animals would have stirred up nutrients leaving them in suspension above the sea floor, far away from the reach of the benthic Ediacaran life-forms.  In essence, the microbial mats and more complex but ultimately, confined to the sea floor Ediacaran fauna, would have found that nutrients that once always fell to the seabed were now suspended in a new marine ecosystem, effectively placing these nutrients out of reach.

The Origin of High Frequency Hearing In Whales

Ancient “Echo Hunter” Provides Insight into Whale Evolution

Scientists from the College of Osteopathic Medicine, New York Institute of Technology (New York), in collaboration with colleagues from a number of other institutions including the Museum of Natural History (Paris), have published a paper on a newly described species of toothed whale, one that suggests that echolocation abilities started early in the Cetaceans.

Writing in the journal “Current Biology” the researchers report that they have found evidence of ultrasonic hearing and the use of echolocation as a probable navigation aid in the beautifully preserved inner ear of a 27 million-year-old toothed whale.

An Illustration of Echovenator (E. sandersi) A Newly Described Genus of Toothed Whale

Echovenator sandersi.

A small, early toothed whale (Echovenator sandersi).

Picture Credit: A. Gennari

Known from a skull, jaws and an atlas bone (bone from the neck), which are believed to represent a single individual, Echovenator sandersi had features in its inner ear that suggest that this marine mammal could hear a greater range of high-pitched sounds when compared to most other mammals.  Believed to be a basal member of the Odontocetes (toothed whales),  this fossil suggests that sophisticated echolocation evolved very early on in this whale lineage.

From a Ditch in South Carolina

The fossil remains were discovered during work on a drainage ditch in Berkeley County, South Carolina fifteen years ago.  The bones and fossil teeth are associated with a basal bed of the Chandler Bridge Formation (Upper Oligocene).  The rocks of this formation were laid down in a marine environment, close to the shore (nearshore marine or possibly an embayment).

Commenting on the conclusions of the research, lead author Morgan Churchill (New York Institute of Technology), stated:

“We can tell a lot about how well this animal fits within whale evolution based on the cranial features and we can use that cranial anatomy to determine whether or not it could echolcate.”

Dr. Churchill, a postdoctoral Fellow at the College of Osteopathic Medicine added:

“The fossil specimen shows several features that we would see in a modern whale with echolocation.”

The Prepared Fossil Skull of the Early Toothed Whale (E. sandersi)

The skull of Echovenator sandersi

The prepared skull of the prehistoric toothed whale Echovenator.

Picture Credit: M. Churchill/Journal of Current Biology

A Well-Travelled Whale

In order to assess the morphology and likely capabilities of the inner ear of this early whale, a number of X-ray scans were taken of the skull fossils.  The skull was carefully X-rayed at the Nikon Metrology X-ray facilities in Tring, (Buckinghamshire, England) and these results were compared to X-ray studies of living and extinct whales skulls undertaken at the University of Texas Austin and the National Museum of Natural History in Paris

By examining Echo Hunter’s inner ear, the researchers found evidence of its ability to receive ultrasonic frequencies.  A soft tissue structure called the basilar membrane, while not present in the fossil itself, was indicated by other parts of the ear to be of a size and thickness consistent with high-frequency hearing.  Another part of the inner ear, a thin, bony structure within the cochlea, provided further evidence of a likely echolocation ability.  Echolocation is the use of vocalisations to navigate and to find prey underwater, other studies have proposed that the ability to produce very high frequency sounds occurred early on in the evolution of the Cetacea, this new research suggests echolocation evolved in basal members of the toothed whale group.

Jonathan Geisler, a co-author of the study and a professor at the New York Institute of Technology commented:

“We had suspicions that they were echolocating but to really get down to a rough estimate of frequency, you really had to look in the inner ear in more detail and that’s where this project comes in.”

Echovenator sandersi

About the size of a small dolphin, Echovenator hunted fish and other small, nektonic creatures close to the shore.  It used its echolocation to help it forage in the murky, sediment-filled coastal waters.  The genus name is Latin which means “echo hunter”, the species name honours Albert Sanders, a former curator of The Charleston Museum, in recognition of his contribution to the scientific study of Cenozoic whales.  Mark D. Uhen, a professor at George Mason University, who in 2008 erected a new family of ancient whales, the Xenorophidae, the oldest and most primitive of the toothed whales, the whale family to which Echovenator has been ascribed, explained that previous research had suggested that the earliest toothed whales could echolocate, but that the new paper provided a clearer picture.

The Evolution of High Frequency Hearing and Echolocation in Whales

The evolution of echolocation and ultrasonic hearing in whales.

Plotting the evolution of ultrasonic hearing and echolocation in early whales.

Picture Credit: College of Charleston

Dr. Uhen, who was not involved in this study, said that the development of high-frequency hearing in whales was a nice illustration of natural selection.

Professor Uhen commented:

“I think the way evolution mostly works is that animals adopt a behaviour, and then natural selection changes generation after generation so that they get better and better and better at that behaviour.  Whales started feeding in the water so their feeding apparatus and their ears changed early.”

Heard the one about the origins of echolocation?: The Origins of Echolocation in Dolphins (related article)

To read an article about a potential terrestrial ancestor of whales: Deer-like Fossil Confuses Early Cetacean Evolution

To read an article about a huge, Pliocene toothed whale that swam in the waters around Australia: Giant Aussie Whale a Terror of the Pliocene Seas

Reconstructing the Brains of Ancient Lungfish

Comparing the Brains of Extant Lungfish to their Ancient Relatives

The lungfish might be regarded by some as a “living fossil”, a term that we at Everything Dinosaur prefer not to use, as it implies that a species has remained present in the fossil record for a very long time.  However, the six species of lungfish alive today, do represent an extremely long lineage of fishes, that have remained relatively unaltered since they first evolved back in the Devonian.  How similar extant lungfish are to their ancient counterparts has been determined by a team of researchers from South Australia (Flinders University) and Sweden (Uppsala University) who have used a combination of computerised tomography and computer modelling to map and compare the brains of living lungfish species with fossils dating back some 365 million years.

A Very Ancient Lineage of Fishes – Lungfish

A lungfish from Australia.

A living Australian lungfish (Neoceratodus forsteri).

Picture Credit: Getty Images/Tom McHugh

Ancient Vertebrates

Lungfish belong to the Class Sarcopterygii part of the huge bony fish group of vertebrates, that is most closely related to Tetrapods and that includes our own species H. sapiens.  Today’s lungfish, all six species, are becoming increasingly rare and scientists still do not know a great deal about them, their behaviours and how they are able to survive in extreme environments.  One thing we do know, is that for a fish, they are relatively big brained.  Of course, brain size does not necessarily reflect cognitive function, but lungfish brains tend to occupy about 80 percent of their cranial cavity.  Compare this to the somewhat more sedentary and a close relative of lungfish, the Coelacanth (Latimeria).  Studies of Latimeria have shown that less than 5% of their cranial cavity is occupied by their brains.

Using Technology to “Brain-warp” Lungfish Fossils

Having a cranial cavity which is mostly filled by brain tissue is a trait more associated with mammals than with fish.  Knowing this, scientists can use the endocast of lungfish fossils that have been preserved in three-dimensions to map the brains of these ancient creatures.  That is exactly what the Swedish and Australian researchers did and their paper has been published on line in the open source directory of the Royal Society.

The fossilised remains of a Late Devonian lungfish (Rhinodipterus) excavated from the Gogo Formation of western Australia have been subjected to high resolution computerised tomography and the data has been used to “brain-warp” cranial soft tissues so the brains of long extinct creatures can be constructed.

A Three-dimensional Skull Fossil of the Sarcopterygian Rhinodipterus from the Gogo Formation

A Skull of the Lungfish Rhinodipterus.

A three-dimensional Rhinodipterus skull from the Gogo Formation.

Picture Credit: ABC

The picture above shows a right lateral view of the skull of Rhinodipterus excavated from the famous Gogo Formation .  The three-dimensional preservation of fossils has permitted the cranial research to take place.

Flinders University evolutionary biologist and lead author of the scientific paper, Alice Clement commented:

“These fishy cousins of ours offer a great insight into our ancient ancestors who first crawled out of water and onto land some 370 million years ago.”

The research team used the endocast from a fossil lungfish to form a three-dimensional diagram of the brain and surrounding tissue.  From this, the scientists could develop ideas regarding brain function and phylogeny of the lungfish family as a whole.  An ancient lungfish brain reconstructed in virtual reality is one thing, built in conjunction with the team’s own sophisticated and novel distance mapping software, but it is hoped these techniques can be applied elsewhere in the fossil record.

Mapping the Brains of Lungfish

Brain mapping in Lungfish.

The Queensland Lungfish brain compared to an ancient relative (Rhinodipterus).

Picture Credit: The Royal Society

The picture above shows brain comparisons between an extant Queensland lungfish (Neoceratodus) and the extinct lungfish Rhinodipterus of the Late Devonian.   Colour coded distance map (a) for the relationship between brain and cranial cavity in Neoceratodus, (b) a three-dimensional endocast of Rhinodipterus.  The reconstructed brain of Rhinodipterus (c) presented as a colour coded brain endocast distance map and (d), a spatial overlap of the reconstructed Rhinodipterus brain (grey) with the endocast (pale red).  The reconstructed brain of Rhinodipterus viewed from the top (dorsal view) is diagram (e).

Brains are Difficult Things to Study

The new “brain-warp” method is important because when it comes to ancient anatomy, brains are extremely difficult to study.  Soft tissue such as brains is highly unlikely to fossilise, although brain shape and structure can be inferred if the bones that surround the brain are preserved.  By examining the hollow, a lot of information about brain morphology can be obtained.

Palaeontologist John Long, an expert on the fossils of the Gogo Formation and co-author of the scientific paper commented:

“Animals’ soft tissue usually breaks down, so discovery of a fossilised brain is very rare.”

The Strategic Professor of Palaeontology at Flinders University went onto explain that lungfishes have a very long evolutionary history, first evolving some 410 million years ago and having a peak diversity of about a hundred species during the latter part of the Silurian and through to the Devonian.

Weird Facts about Lungfishes

  • Molecular studies using living lungfishes and the Latimeria genus of Coelacanth have shown that lungfishes are more closely related to Tetrapods than Coelacanths.
  • Six species of lungfish are know, the Queensland lungfish (Neoceratodus forsteri) from Australia, four species from Africa and one species from South America.
  • The South American lungfish (Lepidosiren paradoxa) when first scientifically studied in the mid 1830’s was thought to be a reptile due to its close affinity with Tetrapods.
  • The West African lungfish (Protopterus annectans) can go without food for more than three years.  When this lungfish was scientifically described by Sir Richard Owen, it was placed at first with the Class Amphibia (amphibians).

One in the Eye for Jurassic Mammals

Early Mammals May Have Evolved Night Vision as a Jurassic Survival Strategy

Over the last few days a number of articles have been published detailing the research of scientists from the University of Alberta and the National Eye Institute of the United States who have been studying the light detecting photoreceptors in the retinas of mammals.  It turns out that night-time vision, an ability to see in very low light levels, evolved millions of years ago in early mammals during the Jurassic.  Many of these articles have emphasised the possibility that night vision evolved to help the mammals adjust to a nocturnal lifestyle in order to avoid the dinosaurs that dominated during the day.  However, the real significance of the research might be a unique genetic ability in mammals to transform some types of light receptors in the eye.   This could have huge implications when it comes to restoring sight in people with damaged eyes.

Adapted to a Life in the Dark – Most Mesozoic Mammals

Sabre-Toothed Mammal that lived amongst Dinosaurs

Sabre-Toothed Mammal that lived amongst Dinosaurs.

Picture Credit: Associated Press

Rods and Cones

Mammalian eyes are complex organs.  Light enters the eye through the cornea, passes through the pupil and into the lens, where it is focused and then directed back to photo sensitive cells that line the retina at the back of the eye.  These light sensitive cells covert the light into electrical signals that are carried to the brain by optic nerves and the brain then decodes them and provides vision.  The retina contains two main types of distinctive photoreceptor cells – the rods and cones.  Rods are thinner than the cones and they are distributed differently across the retina, but the chemical process in each that supports the interpretation of light to electrical signals is very similar.

  • Rods – are sensitive to low light levels making then highly suited for night vision.
  • Cones – are less sensitive and not capable of operating effectively in low light but they are much better at being able to pick up broader wavelengths of light across the colour spectrum and therefore they are responsible for colour vision and image resolution in bright light.

Student Phil Oel (University of Alberta) One of the Authors of the Scientific Paper

New insight into mammalian eye evolution.

Helping to work out the photoreceptor layout of the mammalian eye.

Picture Credit: The University of Alberta

When the structure of rods and cones are compared, it would appear that the rods are the more primitive and ancient of the two types of light sensitive cell, but this is not the case.  Researchers have long suspected that the light detecting cone cells came first and the rods evolved later.  In the study of the retinas of mice, the researchers found evidence to support the idea of a cone to rod transition.  They found the vestiges of short-wave cones (those responsible for detecting the shorter wave lengths in the visual light spectrum, the blues and violets), in developing rod photosensitive cells.  This would confirm the idea that had persisted for decades that there was a cone-to-rod transition, that the cones came first.

Co-author of the new study, published in the academic journal “Developmental Cell”, PhD candidate Phil Oel (University of Alberta), stated:

“We found evidence in the mouse that these rods were coming from cones, and thought we’d figured it out at that point.”

Enter the Zebrafish – Fresh Insight

When the scientists looked at zebrafish, a member of the most ancient of all the vertebrate lineages, the fish, they found that there was no evidence for short wave cones having converted into rods.  In zebrafish rods did not show any signs of having developed from cones.

Student Phil Oel, explained:

“When we looked for the same thing in zebrafish, we found no evidence for the same feature, that any rods were ever coming from cones.”

The discovery that mice have the ability to convert some types of cone cell into rods is significant in itself, the lack of this feature in zebrafish has helped the researchers solve a seventy-year-old evolutionary puzzle.

If cones provide colour vision and rods vision in low light, it would be reasonable to assume that diurnal (daytime functioning) animals would have a cone cell dominated retina to provide them with optimal daytime vision.  However, studies of mammalian evolution have shown that mammals have a rod dominated retina, better suited for vision at night or a very low light levels, even with diurnal species like H. sapiens.  In humans we have something like 20 rod cells for every 1 cone cell in our retina.

The “Nocturnal Bottleneck”

Evolutionary biologists have traced the origins of a rod dominated mammalian retina to the Late Jurassic and referred to as the “nocturnal bottleneck theory”.  This theory suggests that many mammalian traits such as excellent hearing, a good sense of smell, a rod cell dominated retina, whiskers and a highly developed sense of touch can be explained by the fact that mammals were confined to the dark, poorly lit undergrowth or to a nocturnal existence, so long as the terrestrial reptiles, most notably the dinosaurs, existed.  It was only with the extinction of the non-avian dinosaurs at the end of the Cretaceous that led to mammals diversifying to occupy diurnal niches in ecosystems.  Even today, the majority of the 8,000 species of mammals on our planet are nocturnal.

Recently, the idea that the mammals were restricted to only a few niches and that they were relatively small has been challenged as new fossil finds suggest that during the Cretaceous the mammals were much more diverse and speciose then previously thought.

To read more about this study: Time to Debunk Mammals Totally Dominated by Dinosaurs Myth

Lead author of the research, Ted Allison, Associate Professor in the Department of Biological Sciences at the University of Alberta commented:

“During the Jurassic period, mammals are diversifying, or about to diversify.  The concept that’s been in the literature for years is that mammals took on a nocturnal habit to survive this period, and escaped the daytime roaming dinosaurs by being more active at night.”

Associate Professor Ted Allison (right) and his PhD student Phil Oel

Scientists providing an insight into mammalian evolution.

PhD student Phil Oel and his supervisor Associate Professor Ted Allison.

Picture Credit: The University of Alberta

Those mammals that were best able to exploit the nocturnal way of life, were the ones that survived, going on to radiate and diversify and eventually, after the dinosaur extinction, replacing the Dinosauria as the dominant terrestrial megafauna.  One intriguing question remained, if the mammals were somehow able to produce extra rod cells to help with night-time vision, then where did they come from?

The Associate Professor explained:

“What we’ve proposed here for the first time is a mechanism for how mammals survived that initial nocturnal stage, how they were able to make many rods and exploit that nighttime adaptation.  This nocturnal bottleneck has been theorised now for some 70-odd years, so it’s a big vision mystery solved.”

The findings not only have important implications for evolutionary biologists, but this new understanding may have clinical applications in the future.  If mammals have a way of converting cone photoreceptors to rod cells then it may be possible to apply this research to help develop ways of restoring vision in humans.

The paper: “Recruitment of Rod Photoreceptors from Short-Wavelength-Sensitive Cones during the Evolution of Nocturnal Vision in Mammals.”

Scientists “Root Out” Oldest Plant Root Cells

Oldest Plant Roots Identified

Scientists from Oxford University and the Departamento de Biología Molecular de Plantas, Instituto de Biotecnología, Universidad Nacional Autónoma de México (Mexico), have identified the oldest known population of plant root cells in a 320 million-year-old fossil.  This study, published as an on line, open access article, highlights the importance of historical collections such as the Oxford University Herbaria, which as part of the University’s Plant Sciences Department, houses an extensive botany collection, with some specimens within the archive over 300 years old.

A Slide Showing Preserved Plant Remains from the Oxford University Herbaria Collection

Carboniferous root structures preserved in a thin slice (slide)

A slide made over 100 years ago preserves evidence of fossilised root structures.

Picture Credit: Oxford University Herbaria

The picture above shows a thin soil slice prepared on a slide over 100 years ago and part of the Oxford University Herbaria collection.  The fossilised soil is estimated to be around 320 million-years-old and shows the cellular anatomy of plants which were growing and decaying in the fossil soil underlying the Carboniferous coal swamp forests.

The scientists have not only revealed the oldest plant root stem cells found to date, the research also marks the first time an actively growing fossilised root has been discovered and it shows that plant root cell division in the past may have been more diverse than today.

Roots and Shoots – Getting to the Root of the Problem

The roots and shoots of plants develop from specialised groups of cells called meristems.  These self renew and produce cells that undergo differentiation.  The organisation of these cells changes when growth stops, so up until this research was published, it was impossible to compare the fossil record with the cellular structure of actively growing meristems.  Using slides from the Oxford University Herbaria that represent thin sections of fossilised soils taken from Carboniferous coal balls, researchers were able to identify the fossilised remains of an actively growing root meristem and examine in detail the stem cells and their structure.  They found that the cellular organisation of the fossilised root tip is unique.  Roots and shoots of ancient plants from the Carboniferous may have grown in a broadly similar way to modern plants such as the angiosperms (flowering plants), but the unique cellular order and structure demonstrates that the meristem growth we find today may only represent a proportion of the root and shoot growth diversity that once existed.  This research indicates that some of the biological processes and systems controlling the root development of plants have now become extinct.

A Highly Magnified Image Showing the Growing Root Apex Assigned to the Species Radix carbonica

The holotype fossil of Radix caronica (growing root).

The dark horseshoe-shaped structure is the root cap protecting the growing root apex as it pushes through the soil.

Picture Credit: Oxford University Herbaria

The structures preserved in the fossil record are similar to those found in extant species, but they are different, they represent a unique cellular arrangement not known in modern plants.

Commenting on the study, one of the authors of the paper, Oxford Plant Sciences PhD student Alexander (Sandy) Hetherington stated:

‘I was examining one of the fossilised soil slides held at the University Herbaria as part of my research into the rooting systems of ancient trees when I noticed a structure that looked like the living root tips we see in plants today.  I began to realise that I was looking at a population of 320 million-year-old plant stem cells preserved as they were growing – and that it was the first time anything like this had ever been found.  It gives us a unique window into how roots developed hundreds of millions of years ago.’

The First Global Tropical Wetland Forests

The fossil soil slides and the root structures they contain are extremely important as they provide a record of our planet’s first global tropical wetland forests.  The Carboniferous swamps and wetlands were to form the extensive coal deposits found in much of the world today, including most of the coal in the United Kingdom, exploitation of which fuelled the industrial revolution.  From a biological point of view, these huge, lycopsid (club mosses), pteridosperm (seed fern) and sphenopsid (horsetails) dominated forests represent the first time deep rooting structures evolved on Earth.  These root systems increased the rate of chemical weathering of the silicate minerals in rocks, a chemical reaction that pulled carbon dioxide out of the atmosphere, leading to a period of global cooling – climate change on a worldwide scale.  Of the 139 slides studied, two root caps were identified.  The first was assigned to a known species Lyginopteris oldhamia, a seed fern (pteridosperm), the second was an unknown species, this has been named Radix carbonica, this translates as “coal root”.

Professor Liam Dolan, (Department Head of Plant Sciences, Oxford University) and lead author of the academic paper, explained:

“These fossils demonstrate how the roots of these ancient plants grew for the first time.  It is startling that something so small could have had such a dramatic effect on the Earth’s climate.  This discovery also shows the importance of collections such as the Oxford University Herbaria, they are so valuable, and we need to maintain them for future generations.”

A Highly Magnified Image Showing the Root Cellular Structure

A close up of the fossilised root structure (Radix carbonica).

Fossilised root structure preserves record of ancient root growth.

Picture Credit: Oxford University Herbaria

From examining the size and number of cells which radiate out from the tip the researchers were able to establish that the root was actively growing at the time it was fossilised.  This makes the finding the first and only discovery to date of the fossilised remains of an actively growing root meristem.

The Root Growth of Radix carbonica is Unique Compared to Living Plant Root Meristems

The schematic diagram below shows the cellular organisation of a typical member of the gymnosperm group (conifers, ginkgos and cycads).  The colours show various major tissue types within the meristem.

Mapping the Evolution of Root Systems

The origin of root evolution in the Plantae.

New study suggests different types of root growth in plants took place in the past.

Picture Credit: Current Biology with additional annotation by Everything Dinosaur

The diagram above shows (A and C) the meristem of a typical gymnosperm, compared with (B and D) the meristem of Radix carbonica.

Yellow = the root cap

Pink = the promeristem (yellow lines in the R. carbonica promeristem indicate the positions of anticlinal cell divisions within the promeristem)

Orange = ground tissue

Blue = epidermis

Green = procambium

A simplified cladogram showing the hypothesised origin of roots based on this new study (E).  The meristems of different types of lycopsids are compared to the evolution of ferns, gymnosperms and the path towards the flowing plants (angiosperms), that evolved later.

Everything Dinosaur acknowledges the help of a press release from the press team at Oxford University in the compilation of this article.

The paper “Unique Cellular Organization in the Oldest Root Meristem”  is published in Current Biology. DOI: 10.1016/j.cub.2016.04.072

Sorting Out Lucy’s Neighbours

Pliocene Hominin Diversity – Neighbours for Lucy

Anthropologists have discovered that the human family tree, that branch of the hominins that led ultimately to our own species H. sapiens, is very complicated.  We might like to think that our own evolution was pre-destined, once the first apes that left the trees and started to walk upright on a regular basis, our big-brained species was bound to come along, but that does not seem to be the case.  For example, scientists have now concluded that there were at least four species of hominin present in Europe and Asia up until relatively recently.  In a new paper, published in the “Proceedings of the National Academy of Sciences”, researchers have reviewed Late and Middle Pliocene hominin fossils and concluded that there were multiple species of early hominins around between 3.8 and 3.3 million years ago.  It seems that “Lucy” the most famous example of Australopithecus afarensis had company – lots of company in fact.

Late Miocene and Pliocene Hominin Chronological Distribution

A number of early hominin species have been identified.

Late Miocene and Pliocene hominin diversity.

Picture Credit: PNAS with additional annotation by Everything Dinosaur

All Early Hominin Fossils Packed into a Suitcase

Four decades ago, the number of early hominin fossils discovered in eastern Africa was very low.  We recall anthropologists joking, but with some degree of truth, that the entire east African hominin fossil record could be packed into a single, large suitcase.  However, recent fossil discoveries have greatly increased the amount of fossil material known and raised the possibility that early hominins in Africa were at least as speciose as later members of the human family tree.

The graph above plots the current recognised species of Late Miocene and Early Pliocene hominin species over the last seven million years or so.  The different coloured columns represent different taxa and the length of each column equates to the approximate length of time that each taxon is known to have existed.  Dotted parts indicate uncertainty in the age of a taxon or the absence of fossils from that particular time span.  Lucy, as a member of the Australopithecines (southern apes), and an A. afarensis represents a species that lived from approximately 3.9 million years ago to around 3 million years ago.  The solid, black line forming a rectangle shape on the timeline around 3.6 million years ago shows the presence of multiple hominin species during the Middle Pliocene.  It seems that Australopithecus afarensis had lots of other hominin species for company.

In the diagram above, the dashed rectangle situated around the 6 million years ago mark, indicates possible hominin diversity as far back as the Late Miocene, if the three earliest named hominin species represent different taxa.

An Update on Pliocene hominin fossils from Africa

The authors of the scientific paper, Dr. Yohannes Haile-Selassie and Dr. Denise Su (The Cleveland Museum of Natural History), in collaboration with their colleague Dr. Stephanie Melillo (Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany), have compiled a detailed review of the current fossil material of early hominins, collating data from fossil discoveries from Ethiopia, Chad and Kenya.  This review demonstrates the complexity of the early hominin evolutionary tree and it raises the intriguing question, how did these early humans relate to each other?  For example, was there niche partitioning taking place?  How did these different species compete for resources?

Lead author of the report, Dr. Yohannes Haile-Selassie (Curator of Physical Anthropology at The Cleveland Museum of Natural History), commented:

“It is now obvious that more than one species of early hominin co-existed during Lucy’s time.  The question now is not whether Australopithecus afarensis, the species to which the famous Lucy belongs, was the only potential human ancestor species that roamed in what is now the Afar region of Ethiopia during the middle Pliocene, but how these species are related to each other and exploited available resources.”

Australopithecus deyiremeda

The idea that a number of Australopithecines co-existed is not new.  Back in 2015, Everything Dinosaur reported on the discovery of Australopithecus deyiremeda by a team of researchers led by Dr. Yohannes Haile-Selassie.  This new species was named after four fragmentary pieces of fossil jaw bone complete with teeth, which represented three individuals had been discovered in the Woranso-Mille area of the Afar region in March 2011.

Dr. Yohannes Haile-Selassie Holds a Cast of the Jaws of Australopithecus deyiremeda

A cast of the jaws of A. deyiremeda.

A cast of the jaws of A. deyiremeda an Australopithecine from northern Ethiopia.

Picture Credit: Laura Dempsey

To read about the Australopithecus deyiremeda research: A New Face to the Human Family Tree

Putting an Evolutionary Foot In It!

The paucity of the fossil record and the highly fragmentary nature of most of the known fossil material makes interpreting the fossil record extremely difficult.  Perhaps the most compelling evidence for the presence of more than one type of early human species in eastern Africa between 3.8 and 3.3 million years ago, was the discovery of a partial foot (the Burtele foot), in the Woranso-Mille region of Afar, the same area where the jaws of A. deyiremeda were discovered.

The Burtele Foot Fossil (Afar Region of Ethiopia)

A partial right foot with an opposable big toe representing an as yet not described species of early human.

Picture Credit: The Cleveland Museum of Natural History/ Dr. Yohannes Haile-Selassie

The specimen (BRT-VP-2/73), is photographed above in the correct anatomical position.  These bones represent the right foot and the bones on the left of the picture are the big toe (hallux).  Researchers have concluded that this digit was opposable, so the foot was also used for grasping.  The foot bones, referred to as the “Burtele foot”,  come from strata that is little younger than the strata where the jaw bone fossils of Australopithecus deyiremeda were found.  However, it is possible that these two species may have co-existed.

The foot represents a species that was contemporaneous with A. afarensis and probably several other early hominin species too.  Assessment of the walking abilities of the creature represented by the Burtele foot, indicates that its locomotion was different from that of A. afarensis, perhaps the foot bones provide evidence to support the idea that a more ancient human-like species, Ardipithecus ramidus persisted much longer than previously thought, or these foot bones could represent an as yet unknown species.

Commenting on the need to continue to explore eastern Africa to help unravel this early human puzzle, Dr. Stephanie Melillo of the Max Planck Institute stated:

“We continue to search for more fossils.  We know a lot about the skeleton of A. afarensis, but for the other Middle Pliocene species, most of the anatomy remains unknown.  Ultimately, larger sample sizes will be the key to sorting out which species are present and how they are related.  This makes every fossil discovery all the more exciting.”

Kulindadromeus Gets Its Coat of Feathers

Reconstructing the Feathered Kulindadromeus zabaikalicus

The remarkable Kulindadromeus (K. zabaikalicus), the earliest known member of the Ornithischia (bird-hipped dinosaurs), to have been feathered has been reconstructed as part of a dinosaur exhibition currently on display in Japan.  The beautifully made, life-size model of this early Middle Jurassic herbivore will provide visitors with an opportunity to see for themselves how some of the Ornithischia evolved into feathered forms.  Kulindadromeus suggests that perhaps, the majority of dinosaurs, not just the Theropods were covered in a coat of feathers.

A Life Size Model of Kulindadromeus zabaikalicus

A scale model of the feathered dinosaur Kulindadromeus.

A 1:1 scale model of Kulindadromeus.

Picture Credit: T. Hubin/RBINS

It was back in the summer of 2014 that Everything Dinosaur reported upon the discovery of an extensive bone-bed that preserved the fossilised remains of a number of specimens of this dinosaur.  The rocks represent strata that was laid down sometime between 175 and 160 million years ago (Middle Jurassic Period).

To read an article by Everything Dinosaur on the discovery of Kulindadromeus: Did All Dinosaurs Have Feathers?

The Kulindadromeus fossil material comes from a site on the banks of the River Olov in the TransBaikal region of Siberia.  Dr. Pascal Godefroit (Royal Belgian Institute of Natural Sciences), one of the scientists responsible for naming this little, one-metre-long dinosaur back in 2014, has commissioned the reconstruction of a life-sized model of this feathered animal along with a replica of its skeleton.

A Model of the Skeleton of Kulindadromeus

A replica of the skeleton of Kulindadromeus.

A model of the Kulindadromeus skeleton

Picture Credit: T. Hubin/RBINS

Kulindadromeus was very probably bipedal and it may have lived in flocks, just like many birds do today, but it was not very closely related to Aves (birds).  It had filamentous structures covering most of its body, including its head, chest and neck.  The more complex feather-like structures were restricted to the upper arms and the top of the legs, an arrangement of feathers found in many fossils of small Theropod dinosaurs excavated from Lower Cretaceous strata in the famous Lioaning Province of China.  The long tail, that made up at least forty percent of the animal’s entire length may have been completely devoid of feathers, just covered in scales, giving this dinosaur a “rat-tailed” appearance.

Kulindadromeus Could Not Fly

Standing around sixty centimetres high a the hips, this fast-running dinosaur could not fly.  Instead, the feathers probably served as insulation to help keep this active, little animal warm.

Visitors Will Get the Chance to Look into the Eyes of Kulindadromeus

A life-size replica of the dinosaur Kulindadromeus from Siberia.

Kulindadromeus life-size replica.

Picture Credit: T. Hubin/RBINS

Fossils of this curious dinosaur were uncovered in a series of field expeditions between 2010 and 2013, one of the leading researchers was Dr. Sofia Sinitsa (Institute of Natural Resources, Ecology and Cryology) from the Siberian city of Chita.  When the discovery of Kulindadromeus was announced, it led to wide speculation that all dinosaurs could have possessed some form of integumental covering.  Currently, Dr.  Maria McNamara of Cork University (Ireland), is working on a study of the microstructure of the animal’s “proto-feathers”.  A scientific paper detailing this research is due to be published soon.

Commenting on the significance of Kulindadromeus, Dr. Godefroit stated:

“It is a big discovery.  It has completely changed our vision of dinosaurs.  The animal had a short snout, long hind legs, short arms and five strong fingers.  It had reptile-like scales on its tail and shins, with short bristles on its head and back.”

Hundreds of Bones Excavated

During the course of the summer expeditions, the joint Belgian-Russian team excavated a vast amount of Kulindadromeus fossil material, as well as insect and plant fossil remains.

Kulindadromeus Fossil Material from the River Olov Site

Preserved Kulindadromeus bones in a volcanic ash deposit.

Kulindadromeus fossil material.

Picture Credit: T. Hubin/RBINS, V. Shevchenko

In the field photograph of one of the fossil slabs from the dig site (above), Kulindadromeus bones can be made out in the bottom right hand corner of the piece of rock.  Danielle Dhouailly, an expert on bird feathers from the Universite Joseph Fourier in La Tronche (France) explained:

“The feathers look like down feathers from some modern chickens.  When we compare them with the leg scales, it looks as if the scales are aborted feathers, an idea that has been suggested to explain why modern birds also have scaly, bare legs.”

The wonderful Kulindadromeus replica is currently being displayed at the Tokyo National Museum of Nature and Sciences.

 Dr. Pascal Godefroit added:

“I was really amazed when I saw this.  We knew that some of the plant-eating Ornithischian dinosaurs had simple bristles and we couldn’t be sure whether these were the same kinds of structures as bird and Theropod feathers.  Our new find clinches it, all dinosaurs had feathers, or at least the potential to sprout feathers.”

The discovery of Kulindadromeus and the identification of feathered Ornithischians raises the tantalising possibility that the common ancestor of both the Theropoda and the Ornithischian dinosaurs, which might have lived more than 235 million years ago, may have been covered in feathers.

Early Cretaceous Crocodile from Brazil Subjected to Shrink Ray

Susisuchus anatoceps – Probably a Dwarf Crocodile

A team of Brazilian based scientists have concluded that the Early Cretaceous crocodile Susisuchus (S. anatoceps) may not have been as large as previously thought, writing in the on line, open access journal PLOS One, the researchers suggest that this species may have grown to less than one metre in length.  It had been thought that specimens collected to date represented juveniles but analysis of growth rings preserved in the fossilised bones of one individual, believed to have died when it was around seventeen years old, suggests that this reptile rarely exceeded seventy centimetres in length.

Early Cretaceous Crocodile Subjected to Palaeontologist Shrink Ray

Susisuchus anatoceps scale drawing.

A modified scale drawing of the Cretaceous crocodile Susisuchus.

Picture Credit: University of Queensland with additional annotation by Everything Dinosaur

Originally described in 2003 from a partial skeleton representing an individual whose desiccated carcase probably laid out on an ancient riverbed for some considerable time before eventual burial, Susisuchus anatoceps is known from about ten fossil specimens, which from their small size were all thought to represent young animals.  However, the scientists, which included lead author of the scientific paper Juliana M. Sayão  from the Universidade Federal de Pernambuco (north-eastern Brazil), analysed the internal structures of a two bones (a rib and a bone from the lower front limb – an ulna) from a Susisuchus and concluded that this specimen represented an animal that was a sub-adult and therefore nearly fully grown.  This research suggests that these crocodiles were small bodied and comparable to extant dwarf crocodiles.

The Fossil Specimen Studied Showing Location Where Bone Samples Were Taken and Close up Views of the Bone Structure

Calculating the age of Susisuchus anatoceps.

A close up of the rib and limb bone fragment used to assess the age of a Susisuchus anatoceps crocodile specimen.

Picture Credit: PLOS One

The picture above shows (A) the fossil specimen of Susisuchus (MPSC R1136), which is part of the vertebrate fossil collection of the Museu de Paleontologia da Universidade Regional do Cariri (Santana do Cariri, Ceará State, Brazil).  The scale bar for (A) is five centimetres.  The area in red (marked B) and green (marked C) with arrows (corresponding to rib and ulna respectively) indicate where the cuts were made for the bone sample collection. (B) View of the cross section of the ulna. (C) View of the cross section of the rib.  In the scientific journal the scale bar for B and C is reported as being 5 mm but we suspect that this scale is inaccurate for both photographs.

Susisuchus anatoceps

Fossils of this ancient crocodile come from the Crato Formation of Brazil and indicate that Susisuchus lived around 112 to 100 million years ago.  Similar crocodile fossils have been discovered in Australia suggesting that these types of crocodiles may have migrated using river systems that linked these parts of the super-continent Gondwana.  Although, now known to be small, when it comes to Crocodylomorphs Susisuchus punches way above its weight as it is one of the oldest crocodilians with a dermal skeleton very similar to that seen in extent crocodilians (members of the Eusuchia), comprising a dorsal shield comprising of at least six longitudinal rows of osteoderms (dermal armour).  This suggests that Susisuchus is phylogenetically very close to the origin of Eusuchia – modern day crocodiles, caiman, alligators and gharials.

Susisuchus anatoceps  – On the Road to Modern Crocodylians

The fossilised remains of the ancient crocodile Susisuchus anatoceps.

Susisuchus anatoceps fossil material.

Picture Credit: University of Queensland

Despite the wealth of vertebrate fossil material associated with the Crato Formation, crocodile fossils are relatively rare.  Many palaeontologists believe that the Crato Formation deposits, the majority of which represent a brackish, lagoonal type environment was not the natural habitat of Susisuchus, instead the bodies of animals were washed downstream into the lagoon and therefore the carcase may have travelled extensively before final deposition.  It is probable that Susisuchus lived in freshwater environments further inland and it fed on small fish, molluscs and amphibians.

Comparing the Size of Brazilian Cretaceous and Early Palaeocene Crocodiles

Scale comparison of Brazilian Cretaceous Crocodylomorpha.

Comparative size of Susisuchus anatoceps to other Brazilian Cretaceous and Palaeocene Crocodylomorphs.

Picture Credit: PLOS One

The diagram above shows Susisuchus anatoceps (4) compared to three other Brazilian Crocodylomorphs from the Cretaceous and Early Palaeocene namely:

1).  Baurusuchus salgadoensis a 4.5 metre long terrestrial predator named in 2005 kwon from the Adamantina Formation of Brazil which lived around 90-83 million years ago.

2).  Guarinisuchus munizi a 3 metre long marine crocodile known from the Early Palaeocene.

3).  Mariliasuchus amarali a  one metre long, highly terrestrial crocodile known from the  upper part of the Adamantina Formation indicating a Late Cretaceous age (possibly Campanian or perhaps Maastrichtian faunal stage)

Strange Tusked Dicynodont from Brazil

Rastodon procurvidens – A Permian “Tusker” from Brazil

Palaeontologists wanting to learn more about a bizarre group of Permian/Triassic therapsids known as Dicynodonts usually head to the famous Karoo Basin of South Africa, a part of the world famous for its reptile fossils.  So abundant are the various Dicynodont fossils in the strata that make up the Permian and Triassic components of the Karoo Basin Supergroup, that their fossil remains are used to date the rocks in which they are found.  There is no doubting that the Dicynodonts were a very successful group, but what about the rest of Pangaea and their fossil record?

An Illustration of a Typical Dicynodont

A Dicynodont model.

A model of a Dicynodont (therapsid).

Scuttle forward Rastodon procurvidens, only the second Permian Dicynodont to be identified from the Paraná Basin of Brazil.  A team of international scientists writing in the on line, open access journal PLOS One describe Rastodon from a beautifully preserved, albeit slightly crushed fossil skull that was found on a private residence (Boqueirão farm outcrop), located in the municipality of São Gabriel (Catuçaba district), approximately in the central part of the Rio Grande do Sul State, in south-eastern Brazil.

The researchers, which include scientists from the Federal University of Rio Grande do Sul and the Museum für Naturkunde (Berlin, Germany), studied the holotype material, which consists of most of the skull with attached lower jaws and named the animal “Rasto – tooth” in honour of the Rio do Rasto Formation from which the fossils came.  Ironically, as a synapsid reptile, Rastodon is more closely related to mammals such as ourselves than it is to modern reptiles like crocodiles, snakes and lizards.

Left Lateral View of the Skull of Rastodon procurvidens

Rastodon fossil skull from Brazil.

A view of the skull of the therapsid Rastodon.

Picture Credit: Felipe Lima Pinheiro

Odd Tusks

Many types of Dicynodont had enlarged tusks in the upper jaw.  The tusks of Rastodon seem to be extremely unusual, even for this bizarre group of ancient herbivores.  They are very small and curve forwards with the tip of each tusk angled towards the front of the snout.  Phylogenetic analysis indicates that R. procurvidens is the earliest and most basal member of Bidentalia, a cosmopolitan clade that includes Permian and Triassic Dicynodonts whose dentition is usually reduced to a pair of maxillary tusks.   The authors of the scientific paper note that the shape and position of the tusks were not due to post-mortem crushing of the skull bones or due in any part to the fossilisation process.   Both tusks look symmetrical when the skull is viewed from the front end (anterior view) and in addition, each tooth fits neatly into a groove in the lower jaw.  The presence of this embayment or recess confirms that the teeth position and morphology are just about unchanged from when this quadruped scuttled around this part of Brazil the best part of 260 million years ago.  The odd tusks of Rastodon have inspired the trivial name which means “curved forward tooth”.

To read an article about another bizarre Therapsid from BrazilBizarre Sabre-Toothed Permian Herbivore from Brazil

As to the specific function of these strange teeth, well, that remains somewhat of a mystery.

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