Algal Bloom Toxins Poison Prehistoric Marine Mammals

It had been the subject of intense scientific study, a series of mass graves of prehistoric cetaceans and other vertebrates found in the remote Atacama Desert of Chile.  The assemblage of fossils included many pristine examples of prehistoric whales preserved in sediments dated to the Miocene Epoch, the majority of the skeletons were virtually complete, so what caused these mass graves of so many ancient creatures?

A Scientific Paper

In a paper published in the academic journal “The Proceedings of the Royal Society B. (Biology)”, scientists have finally been able to piece together the sequence of events that led to one of the most spectacular Miocene aged vertebrate fossil collections known anywhere in the world.  It seems that algal blooms occurred in the region and have been preserved in sediments dated as being between six and nine million years old.  These blooms of microscopic, single-celled and multi-celled phytoplankton produced large amounts of a deadly neurotoxin, which when breathed in or ingested by these animals led to rapid organ failure and sudden death.

The blooms were probably caused by a sudden increase in run-off from the Andes Mountains, perhaps as a result of violent storms.  The sediments entering the Pacific coastal area of Chile were saturated with iron and other minerals which led to the dramatic increase in algae and the eventual algal blooms that led to the devastation of local stocks of marine mammal fauna.

Prehistoric Marine Mammals

One clue to the cause of death lay in the position and orientation of the  majority of corpses.  Many of the whale skeletons were lying on their backs, it seems that these creatures had not become stranded but had been washed ashore already dead.  Baleen whales such as Fin and Humpback whales have a huge throat pouch.  When these animals die and the carcase starts to decompose, this pouch fills with gases created from the putrefying flesh.  This pouch acts as a huge flotation device, the belly-up post mortem position suggests that these cetaceans died out at sea and then got washed inshore.

To view models and replicas of a prehistoric whale (whilst stocks last) and other prehistoric animals: CollectA Prehistoric Life Models and Figures.

In addition, the extremely well preserved and relatively undisturbed layout of the fossilised bones suggest that these bodies were washed ashore quite quickly and that the corpses were not scavenged by predators such as sharks which were abundant in these ancient Miocene waters.  Once on land, the carcases were lifted out of the surf zone perhaps by exceptionally high tides and deposited high up the beach, once there, since there were very few large predators in the arid environment the corpses lay relatively undisturbed until they were buried by sand.

Commenting on the exceptional preservation of the fossilised remains, one of the lead researchers, Nicholas Pyenson (a palaeontologist at the Smithsonian National Museum of Natural History), stated:

“These big hunks of meat stranded on a tidal flat, yet there were no terrestrial predators like a bear, nothing really larger than a dog, that could dismember the carcases and carry the bones away”.

Fossil Algal Mats

Tell-tale signs of fossil algal mats found in proximity of the skeletons also suggest it was neurotoxins from a bloom of phytoplankton that killed these animals.  Such mats are produced when algae reproduces rapidly and the population grows to many times the normal levels.  These preserved mats are orange in colour a result of their high iron content.  This suggests that large amounts of iron was dissolved in the offshore waters of Chile, most likely as a result of large amounts of iron-rich sediment reaching the sea having been washed down from the nearby mountains, to the east of the fossil site’s location.

This incident does not seem to have been an isolated event.  Four distinct layers of fossils have been identified, this indicates that algal blooms leading to such high levels of marine vertebrate mortality must have happened at least on four separate occasions over a period of perhaps ten to sixteen thousand years.  The fossil site was originally revealed back in 2010 when the Pan-American highway was being widened, although the area had already revealed a number of whale skeletons and other prehistoric marine mammals, such a concentration of large baleen whale fossils is particularly rare.

Ten Different Kinds of Marine Vertebrates

The palaeontologists have identified ten different kinds of marine vertebrates including whales, marlins, billfish, at least two species of seal, a bizarre Odobenocetops, a whale with two tusks that made it resemble an extant walrus, plus the remains of an aquatic sloth have also been discovered.  Such a mixture of different vertebrates all meeting a sudden end, made the scientists discount a virus that may have led to the deaths of a number of animals of the same species but not such a wide range of different marine animals.

The Smithsonian based researchers have prepared and extensive record of the fossil material, the area is known locally as the Cerro Ballena (the hill of whales) and there may be many more whale carcases buried in this region, already the fossils mapped so far represent the richest and most concentrated whale fossil site known anywhere in the world.

Some Whale Fossils May be Put on Display in Museums

The magnificent ancient whales gallery at the Frankfurt Natural History Museum (Germany). Picture credit: Everything Dinosaur.

Picture credit: Everything Dinosaur

Dr Pyenson went onto add:

“The condition and arrangement of the bones, the presence of algal mats on some fossils and the fact that there are multiple species of marine animals at the site, all point to killer algae as really the only plausible explanation.  In today’s world, harmful algal blooms happen all the time.  This is the first time we can pin it down in the fossil record for marine mammals.”

The discovery also has implications for a number of extant marine mammal species.  Such algal blooms could devastate already vulnerable populations of rare inshore dolphins, dugongs and manatees.

Huge Pachyrhinosaurus Dinosaur Skull Discovered in Alberta

Many different types of horned dinosaur are known from Upper Cretaceous deposits of Canada and the United States, one of the best represented of all the ceratopsian genera in Canada is Pachyrhinosaurus, a member of the centrosaurine group.

Fossil Discoveries

Despite a lot of fossil discoveries over the last seventy years or so, finding cranial fossil material from a pachyrhinosaur is still a significant event.  A team of researchers from the University of Calgary have reported finding an enormous skull of an old, mature Pachyrhinosaurus, this fossil material might represent the largest skull specimen of a Pachyrhinosaurus discovered to date.

The specimen was found back in October 2013, close to the town of Drumheller, a part of Alberta, that team members at Everything Dinosaur know very well.  Assistant Professor Darla Zelenitsky, a leading vertebrate palaeontologist, was conducting a routine survey of one of the very many fossil deposits in the area when the discovery was made.  What at first glance looked like an outcrop of rock, was actually the partially exposed remains of a dinosaur’s skull.  The skull is believed to measure around two metres in length.

Commenting on the importance of the University’s fossil find, Assistant Professor Zelenitsky stated:

“Based on our preliminary estimates, the dinosaur’s head would have been well over two metres long and was likely of a mature or older individual.  The skull of this animal has an enormous bony structure over the snout that would have made for a very strange looking individual.”

The Assistant Professor from the University’s department of Geosciences went on to add:

“It is very rare to find such a complete skull specimen of this size and type in the region.”

Three Species Recognised

Currently, three species of pachyrhinosaur have been assigned to the Pachyrhinosaurus genus, at this stage Everything Dinosaur team members have proposed that as this material comes from the famous Horseshoe Canyon Formation, it is likely to represent a Pachyrhinosaurus canadensis, although if the fossil material is from a older component of this formation it could be a skull from the species which was described in 2008 and known as Pachyrhinosaurus lakustai.

The pachyrhinosaurs were one of the last of the great horned dinosaurs to evolve, P. canadensis for example, is known from fossil bearing strata that has been dated to around seventy million years ago.  Growing to lengths in excess of six metres and perhaps weighing as much as three tonnes, these herbivores were sizeable dinosaurs.

Palaeontologist Darla Zelenitsky with the Newly Discovered Pachyrhinosaur Fossil Material

Darla with the dinosaur skull.

Picture credit: University of Calgary

Pachyrhinosaurus

The picture shows Darla with part of the skull exposed and the remainder still sitting in its jacket of burlap.  Behind the fossil is an illustration of a Pachyrhinosaurus (artwork by Julius Csotonyi).  After the initial discovery, the research team with the help of a number of field staff removed several thousand kilogrammes of surrounding rock to extract the skull material.  The skull has spent the last four months or so in a laboratory at the University being carefully prepared for study.

Explaining the preparation work that had been undertaken, Darla stated:

“So far, the upper part of the skull has been exposed and the skull will be flipped over to prepare the lower part, including the jaws.  There are still many months of work necessary in order to clean the entire skull.”

It has also been suggested that this pachyrhinosaur material could represent a new species, further examination will be required before any conclusions can be drawn.  Pachyrhinosaurus is already the most speciose of the centrosaurine genera and the problem with horned dinosaurs is that as these animals grew and matured, so their skull morphology and its ornamentation changed.

Combine this with any subtle distortion that may have occurred during the fossilisation process and determining a new species, even from an 85% complete skull will be no mean feat.

An Illustration of a Pair of Pachyrhinosaurs

Two adult pachyrhinosaurs.

Picture credit: Mike Fredericks

Associate Professor Zelenitsky outlined the team’s next steps:

“Our initial goal will be to determine if this specimen represents a new species.  Following that, the specimen will be measured and scanned to help document how the skull of pachyrhinosaurs changed during growth, particularly in the later stages of life.  A discovery of this nature will certainly add to our understanding of the biology of pachyrhinosaurs.”

Pachyrhinosaurs in the Spotlight

Pachyrhinosaurs have recently been very much in the spotlight when it comes to horned dinosaurs.  A herd of pachyrhinosaurs were the stars of the recent film “Walking with Dinosaurs in 3-D” in addition, Pachyrhinosaurus was named the ninth most popular prehistoric animal in Everything Dinosaur’s annual survey of prehistoric animal popularity.  Safari Ltd have recently introduced a highly acclaimed model of a Pachyrhinosaurus (believed to represent P. canadensis) into the popular Wild Safari Dinosaurs model range.

The Wild Safari Dinosaurs Pachyrhinosaurus Dinosaur Model

Horned dinosaur model.

Picture credit: Safari Ltd

For models and replicas of horned dinosaurs and other prehistoric animals: Wild Safari Prehistoric World Replicas.

It is hoped that once the skull material has been fully prepared and cleaned it will be put on permanent display at Calgary University.  The Geosciences department have plans to explore the vicinity of the skull fossil find, in case other elements from the skeleton of this dinosaur can be found.

Malaysia’s First Dinosaur Discovery – Potential Spinosaurid

On a scale of dinosaur discoveries a few isolated and worn teeth are not necessarily going to set the world of palaeontology alight but for the team of Malayan and Japanese researchers, the fragmentary fossils discovered at a secret location, deep in the heart of rural Pahang have finally put Malaysia on the map when it comes to the Dinosauria.

Malaysia’s First Dinosaur

Scientists from the University of Malaya working in collaboration with researchers from the Waseda and Kumamoto universities (Japan) have evidence of a potential spinosaur from Cretaceous aged deposits.  These are the first known dinosaur fossils to have been found in Malaysia.

Much of the central area of Pahang has exposed outcrops of Mesozoic aged strata, particularly sediments dating from the Cretaceous, however, this is the first time that evidence of dinosaurs having once roamed the peninsular of Malaysia has been found.  Field expeditions had been mapping likely sites since September 2012 and in a press conference, the excited scientists confirmed that they had indeed found dinosaur fossils and in all likelihood their discovery represents a new species of theropod dinosaur belonging to the Spinosauridae.

Commenting on the fossil finds, lead researcher Dr Masatoshi Sone stated:

“We have started our collaboration and carried out field expeditions to search for potential dinosaur deposits.  Recently, we have successfully confirmed the presence of dinosaur remains [fossilised teeth] in Pahang.”

Fossil sample number UM10575 is one of the team’s most spectacular finds, measuring just under an inch in length (23 mm) and 10 mm wide.  The shape and serrations have led the team to suggest that this tooth is that of a carnivorous dinosaur that specialised in hunting and eating fish.

Spinosaurid Fossils

A number of spinosaur fossil discoveries have been made from Australasia in recent years.  The spinosaurid known as Ichthyovenator (Ichthyovenator laosensis) was discovered in Laos in 2010, in Savannakhet Province, there have also been reports of potential spinosaur fossil material being found in Australia.

To read more about the potential Australian Spinosaur: Tiny Vertebra Re-Writes the History of Australian Dinosaurs.

It was Professor Ren Hirayama (Waseda University, Tokyo), who was given the task of identifying the creature that the teeth probably belonged to.  He describes specimen number UM10575 as having distinct carinae (front and rear edges), typical of the teeth from a spinosaur.  In addition, there are well-marked coarse ridges running down the tooth and the surface bears micro-ornamentation which when viewed under the microscope are characteristic of spinosaurids.

Dinosaur Tooth found in Malaysia.

Picture credit: University of Malaya

Dinosaur Tooth Fossil

It is very likely that there are substantial vertebrate fossil deposits in Malaysia and the Japanese/Malaysian team are confident that dinosaur bones will soon be discovered.  However, they are keeping the exact location of the teeth discovery under wraps.  There is a large black market in dinosaur fossils and a number of important sites in Thailand, Mongolia and Laos have been plundered as unscrupulous fossil dealers cash in on the high prices that such fossils can fetch.  

The scientists expressed the need for the authorities to protect such areas so that private fossil collectors and smugglers can be deterred.  As more fossils are found, it is hoped that Malaysia will one day have its very own Natural History Museum, perhaps in a building close to the University of Malaya in Kuala Lumpur.

Scientists Announce the Fossil Discovery

Academics announce dinosaur discovery.

Picture credit: University of Malaya

Left to right: Dean of Faculty of Science, Professor Dato Dr Mohd Sofian Azirun;  Adnan, Deputy Vice-Chancellor (Academic & International), Professor Dr Mohd Hamdi Abd. Shukor and Dr Masatoshi at the press conference where the fossil was unveiled.

Without any further body fossils it is not possible to reconstruct and image of what the dinosaur might have looked like.  It’s size cannot be estimated either, however, if there has been evidence of a large predator found, then it is very likely that other vertebrate fossils will be discovered.  Certainly, there will be other reptiles, crocodiles and turtles, as these creatures are often found in the lacustrine or estuarine deposits associated with spinosaur fossil discoveries.  In addition, if the habitat supported one large, specialised predator such as a member of the Spinosauridae it is very likely that other dinosaurs and flying reptiles were present.

Everything Dinosaur team members expect to hear more about dinosaur discoveries from this part of the world in the next few months.

An Illustration of the Spinosaur from Laos (Ichthyovenator)

A prehistoric scene featuring the CollectA Ichthyovenator dinosaur model.

Picture credit: Everything Dinosaur

For models and replicas of Asian theropod dinosaurs and other prehistoric animals: CollectA Prehistoric Life Models.

Conventions for Colouring Extinct Animals Using Melanosome Analysis Re-Written

Over the last few years there have been a number of research programmes with a focus on identifying and interpreting preserved melanosome structures in fossil specimens that may provide clues as to the colour of long extinct creatures.  We have had papers published on ginger coloured dinosaurs (Sinosauropteryx) and interpretations of Archaeopteryx (A. lithographica) with black feathers.

Colour of Dinosaurs

Establishing the colour of long extinct creatures, especially feathered dinosaurs has attracted a great deal of media attention lately.  However, new research from scientists based at the University of Akron and the University of Texas in collaboration with a number of Chinese scientific institutions including the China University of Geosciences, has questioned the presumptions made in previous studies.  In addition, this research team’s findings may provide new evidence as to a link between colouration of an animal and its metabolism.

Finding and analysing the shape of preserved melanosomes within fossil material has been at the centre of dinosaur colour analysis.  Melanosomes are specialised components within animal cells responsible for storage and transport of melanin, a natural pigment.  Fossils of animals with feathers, have in exceptional circumstances, been found to preserve remnants of melanosome structures and it is from their shape and arrangement that scientists have been able to infer the colouration of long extinct creatures.

Dark Pigmentation

However, the preponderance of preserved structures that indicate dark pigmentation has puzzled a number of palaeontologists.  The preservation process may favour these darker pigments and therefore the fossil record may show a bias towards dark colouration.  The interpretation of the colour of feathered dinosaurs has been challenged in a number of recently published articles.

To read more about an earlier paper challenging the interpretation of melanosome shape: Identifying the Colour of Dinosaurs – It’s All a Bit of a Blur.

This new Sino/American research takes melanosame studies in a new direction.  Not only does it challenge recently established conventions on fossil pigmentation analysis, this latest study may also provide a tool for understanding the evolution of powered flight and changes in dinosaur physiology that permitted the ability to fly to occur in members of the Dinosauria.  Publishing their work in the academic journal “Nature”, the scientists conducted an in-depth survey of the hair, skin and feathers of a number of extant vertebrates and compared these structures to those known from a number of Chinese vertebrate fossils.

Analysing Melanosomes

They found evidence for evolutionary shifts in the relationship between the shape of the melanosome and its likely colour.  In addition, the researchers discovered that warm-blooded vertebrates (endothermic animals such as birds and mammals) shared a pattern of diverse melanosome shapes that was different from those seen in extant cold-blooded creatures (ectothermic animals such as crocodiles, lizards and snakes).

The scientists discovered that when it came to melanosomes and dinosaurs, maniraptoran dinosaurs and paravians (those members of the Dinosauria believed to be very closely related to birds), also had a wide range of melanosome shapes and sizes.  These patterns mirrored what the researchers found in extant warm-blooded mammals and birds.  By examining how these different shaped and sized melanosomes evolved raises the intriguing possibility of melanosome shape, size and pattern yielding an insight into the physiology of dinosaurs.

Conventions in Melanosome Shape and Size Assessment Linked to Colour May Provide Clues to Dinosaur Physiology

Melanosomes in the fossil record potentially linked to understanding physiology of extinct animals.

Picture credit: Li et al (scientific paper authors)

Decoding the Colour Code

According to this particular piece of research, melanosome shape and size may help with the colour decoding for some species, but in the case of others, the melanosomes may actually be very misleading.  Over the course of their studies, the scientists compared melanosome structures of 181 living specimens with 13 extinct specimens and utilised a lot of the already published data on fossil melanosome diversity.  The team concluded that cold-blooded reptiles living today show  much less diversity in the shape of melanosomes than extant, warm-blooded birds and mammals.  This suggests a link between the evolution of a greater variety of melanosome structures, increasing colour complexity in fauna and higher metabolic rates.

The limited diversity in the shape of melanosomes in living, cold-blooded animals (ectotherms) shows very little correlation to body colour.  The same principle seems to hold true for fossil members of the Archosauria (the group of reptiles that includes the Pterosauria and the dinosaurs).  In short, when the spherical shape of fossilised melanosomes are considered in the preserved proto-feathers or pycnofibres of feathered dinosaurs, it may not be possible to determine the colour of these animals when they were alive, as modern reptiles only seem to have spherically shaped melanosomes but they come in many different colours and hues.

Contrast this to those feathered dinosaurs believed to be closely related to birds (Aves).  The research team found a huge range of different sized and shaped melanosomes, that may correlate to an explosion of colour within these groups.  The shift in melanosome diversity seems to have taken place abruptly, near to the origin of pinnate feathers in maniraptoran dinosaurs.

Commenting on the significance of this research work, one of the paper’s lead authors Julia Clarke (University of Texas) stated:

“This points to a profound change at a pretty discrete point.  We are seeing an explosion of melanosome diversity right before the origin of flight associated with the origin of feathers.”

Melanosome Diversity in the Maniraptora

The researchers were taken by surprise by the significance of the correlation in the pattern of melanosome diversity amongst maniraptoran dinosaurs, paravavians and extant mammals and birds.

Co-author Matthew Shawkey (University of Akron) added:

“Only in living, warm-blooded vertebrates that independently evolved higher metabolic rates do we see the melanosome diversity that we also see in feathered dinosaurs.”

It is now known that many of the genes involved in pigmentation have roles in other processes related to digestion, stress management and reproductive behaviours.  As a result, the evolution of diverse melanosome shapes may be linked to wider changes in the physical abilities of dinosaurs and their physiology.  By studying melanosomes preserved in the fossil record, scientists might be able to infer aspects of dinosaur behaviour related to the evolution of a warm-blooded metabolism.

The explosion of diversity in melanosome shape and structure seems to have taken place right at the origin of pinnate feathers, it may mark a “sea-change” in Dinosaurian physiology that occurred immediately prior to the origin of flight.

Two of the Feathered Dinosaur/Bird Specimens Used in the Study

Feathered dinosaur and bird fossils used in the melanosome study.

Picture credit: Li et al (scientific paper authors)

Beipiaosaurus Studied

The picture above shows two of the fossils analysed in the study.  The top picture shows a fossil of the feathered therizinosaur known as Beipiaosaurus.  This dinosaur shows the rounder melanosomes seen in extant crocodilians and lizards (enlarged area top right).  The bottom picture shows the preserved remains of a bird that lived in the Mesozoic.  Under the scanning electron microscope, a different melanosome shape is detected.  These “skinny” melanosomes are unique to living birds and mammals and many of the feathered dinosaurs such as maniraptorans.

Changes in the diversity of these melanin containing organelles may indicate a physiological shift in feathered members of the Dinosauria that are phylogenetically related to those members of the Dinosauria closest to the origins of powered flight.

Associate Professor Julia Clarke stated:

“We are far from understanding the exact nature of the shift that may have occurred.  But if changes in genes involved in both colouration and other aspects of physiology explain the pattern we see, then these precede flight and arise close to the origin of feathers.”

It is also possible, note the scientists, that colour variation between species and different individuals within species resulting from an increased diversity of melanosome shape and structure may have been due to increasing evolutionary pressure on populations as more and more complex visual signalling behaviours came about.

It is still very early days and palaeontologists have a long way to go when it comes to determining the exact relationship between melanosomes and endothermy.  Ironically, what may turn out to be rather crude attempts at determining the colour of dinosaurs could well have opened the door to a better understanding of dinosaur physiology.

For models and replicas of theropod dinosaurs and other prehistoric creatures: Dinosaur and Prehistoric Animal Models.

Primitive Ichthyosaur Chaohusaurus Provides New Data on Origins of Viviparity in Marine Reptiles

Scientists had thought that the ability to give birth to live young (viviparity) evolved in ancient reptiles that had fully adapted to a marine environment.  The ability to give birth to live young rather than to have to scramble ashore to lay eggs in a nest is known in a number of extinct genera of ichthyosaurs.  A series of fossils discovered last year have helped scientists learn more about the origins of the ichthyosaur group and one remarkable specimen has shed light on the origins of live birth.

Ichthyosaurs (Fish Lizards)

Ichthyosaurs (the name means “fish lizards”), or more correctly termed members of the Ichthyopterygia, are perhaps the most highly adapted to a marine habitat of all the types of marine reptile discovered to date.  Originating in the very Early Triassic, these reptiles evolved streamlined bodies, tails with flukes and flippers.  They superficially resemble today’s whales and dolphins.

An Illustration of a Typical Jurassic Ichthyosaur

An illustration of the ophthalmosaurid ichthyosaur Palvennia hoybergeti.

Picture credit: Everything Dinosaur

Ichthyosaur Genera

Fossils representing at least six different ichthyosaur genera have provided evidence of live birth in this particular group of reptiles, but until now it had been thought that as these reptiles adapted to a life in the sea, they gradually evolved the ability to give birth in the water rather than having to venture out onto land to lay eggs.  However, a group of Chinese and American scientists, in collaboration with an Italian based colleague, have published a paper on a series of Chaohusaurus fossils that indicate that viviparity may have evolved in the terrestrial ancestors of these animals.

The paper detailing the research work has been published in the academic, on line journal PLoS One (public library of science).

Basal Ichthyosaur Fossil

A field expedition to a fossil quarry that had exposed Lower Triassic strata, yielded over eighty different specimens of the primitive ichthyosaur known as Chaohusaurus  from a marine assemblage, representing sediments laid down in a relatively sheltered, shallow tropical sea.  The fossil site is located in south Majiashan,  near the city of Chaohu in Anhui province, approximately 150 miles east of the Chinese city of Shanghai.  The site had been extensively mapped in 2013 and when the U.S./Sino research team explored a slab of rock with preserved remains of the ray-finned fish Saurichthys contained within it, they discovered the fossilised remains of a female Chaohusaurus and her babies.

The position of the fossilised young indicate that the mother and offspring perished during the act of giving birth and the “head-first” orientation of the baby reptiles suggests that viviparity in these animals was inherited from terrestrial ancestors and not an adaptation to living in the sea.

Viviparity Inherited from Terrestrial Ancestors

The scientists which include researchers from the University of California, the Field Museum (Chicago), Peking University and Anhui Geological Museum, have stated how important these fossils are, as very few fossils of primitive, Early Triassic ichthyosaurs are known.  It is hoped that these specimens will help scientists to understand in more detail the transition from terrestrial reptiles to fully adapted marine animals.  The strata has been dated to around 248 million years ago and this indicates that ichthyosaurs were already very well adapted to marine habitats not long after the Permian mass extinction event.

Other fossils of Ichthyosaurs which are believed to show animals that died during the process of giving birth show babies emerging from the mother tail first.  This the usual orientation seen in the majority of air breathing marine vertebrates as being born tail first avoids suffocation.  However, in land-based animals that are viviparous, being born head-first is the norm.

The Slab of Chaohusaurus Ichthyosaur Fossil Material (Mother and Babies)

Chaohusaurus fossil specimen (maternal specimen).

Picture credit: PLoS One/Motani et al

The picture on top is the actual fossil slab, with a colour coded interpretation shown underneath.  Elements coloured black are the back bones of the mother.  The bones coloured blue represent a hind flipper and part of the pelvis of the mother, whilst embryos number one and two are coloured yellow and orange.  The bones coloured red indicate other material from new-born ichthyosaurs.  The bones coloured green are the ribs and gastralia of the maternal specimen.   The scale bar provided measures one centimetre.

Live-bearing Marine Reptiles

Commenting on the research Dr Motani (University of California), one of the lead authors of the scientific paper stated:

“We always assumed that live-bearing in marine reptiles evolved after they invaded the sea, partly because of this difference [evidence to suggest tail-first births].  Now the new fossil shows that the most primitive marine reptile gave birth head first.  This strongly suggests that they inherited live-bearing from their land ancestors.”

Perhaps one of the most famous examples of ichthyosaur live birth comes from Germany.

An Image Showing “Tail-First” Live Birth in Ichthyosauria

Detailed ichthyosaur figure. Temnodontosaurus platyodon.

Picture credit: CollectA

The picture above shows a Jurassic ichthyosaur model (Temonodontosaurus) in the act of giving birth. The baby is emerging from the mother tail first.

To view the CollectA range of not-to-scale models and figures: CollectA Prehistoric Life Figures.

The scientific paper: “Terrestrial Origin of Viviparity in Mesozoic Marine Reptiles Indicated by Early Triassic Embryonic Fossils” by Ryosuke Motani, Da-yong Jiang, Andrea Tintori, Olivier Rieppel and Guan-bao Chen published in PLoS One.