Pliosaur Skull Links Dorking to Kansas

For much of the later stages of the Cretaceous, the area that is now known as the British Isles lay underwater.   Bad news if you are searching for evidence of terrestrial dinosaurs, however, the limestones and chalk deposits associated with southern England can still yield some exciting surprises for vertebrate palaeontologists.  Take for example, the research of Dr Roger Benson (University of Oxford, Dept. of Earth Sciences), who has been examining the fragmentary remains of pliosaurs associated with the lithostratigraphic unit of strata known as the Chalk Group.

Analysis of a Pliosaur Skull

Dr Benson’s analysis of a pliosaur specimen housed in the collection of the Dorking Museum and Heritage Centre reveals that the fossils may have been misidentified, by none other than Sir Richard Owen, the anatomist who is credited with the naming of the Order Dinosauria.

An Illustration from the Original 1858 Monograph by Richard Owen

One of the original lithographs from Owen’s 1858 paper.

Picture credit: The Pterosaur Database/Dr R Benson (Supplement (No. III) to the Monograph on the Fossil Reptilia of the Cretaceous Formations: 1858).

The illustration above shows some of the skull fossils and teeth described by Richard Owen as the pliosaur Polyptychodon interruptus.  The smaller illustrations to be found in the lower portion of the picture depict various pterosaur fossils.

What are Pliosaurs?

Pliosaurs, or those animals that make up the Pliosauridae clade, are an extinct group of marine reptiles, that along with the long-necked plesiosaurs make up the Order Plesiosauria.  Pliosaurs tend have short necks and large, broad skulls.  They have a worldwide fossil distribution and they first appeared during the Early Jurassic with many of these reptiles evolving into giants that specialised in hunting other marine vertebrates like today’s killer whales.  Famous prehistoric animals such as Liopleurodon and the Australian Kronosaurus are examples of pliosaurs.

An Illustration of a Typical Pliosaur (Pliosaurus brachydeirus)

A scale drawing of a pliosaurus.

Picture credit: Everything Dinosaur

Having dominated marine environments for the best part of a 100 million years, with many forms becoming apex predators, towards the early Late Cretaceous remains of these reptiles disappear from the fossil record.  Around ninety million years or so ago, these sea monsters died out.  Why the pliosaurs became extinct remains a mystery.

Studying Fossil Material

It is important for palaeontologists to gain as much information as they can from existing fossil specimens.  Perhaps, thanks to the careful research of Dr Benson and the presence of many fine fossil collections held in regional museums, one day scientists may have a more complete understanding of how these great reptiles evolved and radiated out into so many forms dominating a number of marine palaeoenvironments.  Scientists might even be able to provide information on why these leviathans went into decline and died out.

The Dorking Pliosaur Specimen

During the early part of the 19th century a number of fossils of marine reptiles were collected by amateur geologists and naturalists.  One such collection, which had been the amassed by the first Baron Ashcombe was donated to the Dorking Museum in 1948 by the first Baron’s grandson.  Amongst the specimens donated was the relatively complete skull of a pliosaur which had been discovered sometime in the 1850s.

The first Baron Ashcombe had used his influence to invite none other than Richard Owen to examine the fossil collection.  Richard Owen, who was later to help found the Natural History Museum (London), described this skull as an example of the pliosaur Polyptychodon interruptus (Po-lip-tie-ko-don in-terr-rupt-us), the name means ” broken apart fin shaped tooth”.

A Pliosaur Skull

When Dr Benson visited the Dorking Museum and Heritage Centre to inspect the skull material, he noted a number of similarities between this fossil specimen and the fossils of another pliosaur, known from North America.  In addition, Dr Benson’s study revealed that most other fossils of Polyptychodon species come from rocks that are much older than the ones found in the chalk pits in this part of Surrey (southern England).  This casts doubt over the original conclusions drawn by the celebrated anatomist Richard Owen.  It seems that the Dorking specimen may represent a type of pliosaur whose fossils are associated with Kansas.

A Fragment of the Lower Jaw

Individual tooth sockets (alveoli) can be made out along the jawbone.

Picture credit: Dr Roger Benson (Oxford University)

Affinities with Brachauchenius

Although Owen thought the Dorking specimen belonged to Polyptychodon the shape of the skull (morphology) suggests to Dr Benson that this specimen may actual be another type of pliosaur altogether.  Dr Benson concludes that the Dorking specimen shares many similarities with a pliosaur known as Brachauchenius (Brak-ow-ken-ee-us) whose fossils are mainly associated with the Western Interior Seaway of the early Late Cretaceous that covered most of the land that is now known as the United States.

According to Dr Benson’s research, most other specimens assigned to the Polyptychodon genus are around 115 million years old (Aptian age of the Cretaceous), but the Dorking fossil material comes from much younger strata, rocks that date from around 90-95 million years ago (Cenomanian to Turonian age).  This indicates that the pliosaur fossils within the collection of the Dorking Museum and Heritage Centre represents one of the last of the pliosaurs.

Part of the Lower Jaw Bone

A view of part of the pliosaur lower jaw.

Picture credit: Dr. Roger Benson (Oxford University)

Knowledge of the Pliosauridae

Our knowledge of the Pliosauridae has improved enormously since the time of Richard Owen, as has our knowledge of stratigraphy.  These collections, many of which are housed in small regional museums can still have a very significant role in research, for example, in this instance, helping to build up a better picture of an ancient marine fauna.

Everything Dinosaur stocks a wide range of pliosaur and plesiosaur models: Sea Monsters and Marine Reptile Models.

The Museum’s Chairman, Nigel Arch, commenting on Dr Benson’s visit stated that it was:

“A good example of the value of our collections and the fact that we can always learn more.  It is wonderful to think that the study of this specimen, found locally and collected by a local person, is still contributing to scientific knowledge today.” 

A Pliosaur Tooth of P. interruptus

Compare Dr Benson’s photograph to the pliosaur tooth depicted in Owen’s monograph.

Picture credit: Dr Roger Benson (Oxford University)

Dr Benson put his research into context, explaining:

“Pliosaurs were giant marine reptiles that could swim across oceans, specimens like the Dorking pliosaur show that this is true because similar fossils are also found in America”.

The Importance of Regional Museums

Regional museums such as the the Dorking Museum and Heritage Centre house many fine specimens assisting in the preservation of an amazing geological and fossil record.

Research using some of the specimens from within these collections can help to shed light on the diversity and distribution of pliosaur genera.  Who knows, perhaps locked away in some cabinet, part of the prized fossil collection of another regional museum may lay the fossilised bones of another mislabelled specimen, one that could provide clues as to the why the Pliosauridae became extinct.

Morelladon beltrani – A Spanish Sail-Backed Dinosaur

A team of Spanish scientists have published details of a new genus of plant-eating dinosaur which roamed the Iberian Peninsula about 125 million years ago (Early Cretaceous).  The dinosaur named Morelladon beltrani is believed to have been closely related to Iguanodon and the discovery helps to reinforce the belief held by many palaeontologists that the Ornithopoda were extremely diverse in Europe during this part of the Cretaceous.

Sail-backed Dinosaur

The dorsal vertebrae have large, extended neural spines a feature seen in other Early Cretaceous ornithopods, dinosaurs such as Ouranosaurus from Niger.  These spines may have supported a hump or perhaps a sail-like structure, the purpose of which remains open to debate.

An Illustration of Morelladon beltrani

An illustration of Morelladon.

Picture credit: Universidad Nacional de Educación a Distancia (Spain)

This new species of dinosaur has been named from the fossilised remains of a single animal, preserved bones consist of dorsal vertebrae, the sacrum, partial ribs, the pelvic girdle, isolated teeth from the lower jaw and the right tibia.

However, despite a lack of cranial material, the team of scientists from the Spanish equivalent of the Open University (Universidad Nacional de Educación a Distancia) and the Autonomous University of Madrid (Universidad Autónoma de Madrid), identified eight unique anatomical features (autapomorphic features) that enabled a new genus to be established.

Elongated Neural Spines

One of the unique anatomical features identified were the very elongated and tall neural spines of the dorsal vertebrae.  Such features are known in other plant-eating dinosaurs, such as the Ouranosaurus (Ouranosaurus nigeriensis) from the Early Cretaceous of Africa and although Morelladon is related to Ouranosaurus, a phylogenetic analysis carried out by the Spanish team suggests that this new Spanish dinosaur is more closely related to other western European dinosaur taxa.  Dinosaurs such as Iguanodon (I. bernissartensis) from Belgium and Mantellisaurus atherfieldensis (from England).

The Extended Neural Spines of the Dorsal Vertebrae

A photograph of the fossil material and accompanying line drawing.

Picture credit: Universidad Nacional de Educación a Distancia (Spain)/PLOS One

Close to the City of Morella

The fossils come from a dig site within a quarry about five miles south-west of the city of Morella (Castellón Province), on the eastern coast of Spain.  The specimen was excavated from a red clay bed dated to the Upper Barremian age (125 million years ago), part of the Arcillas de Morella Formation.  The dinosaur’s name means “Morella tooth”, after the location of the fossil find and in keeping with the naming of Iguanodon, which itself means “iguana tooth”.  The trivial name honours quarry owner, Víctor Beltrán who has been prominent in the excavation and research of a number of Cretaceous vertebrates from this part of Spain.

The Fused Sacral Vertebrae of the Specimen (Sacrum)

The sacrum (fused vertebrae over the hips) of Morelladon.

Picture credit: Universidad Nacional de Educación a Distancia (Spain)/PLOS One

Measuring up to six metres long and standing around 2.5 metres high at the hips, this new genus supports the hypothesis that the Iberian Peninsula in the Early Cretaceous was home to a large number of different types of Iguanodon-like herbivorous dinosaurs.

Why the Tall Neural Spines?

There have been a number of theories put forward to explain the presence of elongated neural spines in some types of dinosaur.  For example, one of the most famous of all the meat-eating dinosaurs – Spinosaurus had neural spines which supported a structure its back, often referred to as a “sail” that must have been more than two metres high.  The neural spines of Morelladon hint at a much smaller feature, around half a metre tall.

It has been proposed that since this dinosaur lived in a delta subject to distinct seasons the spines could have supported a fleshy hump where food reserves and fat could be stored to help the animal through leaner times.  Extant North American buffalo (Bison bison) have dorsal spines that support such structures.  The spines could also have supported a sail-like structure, perhaps this had a role in communication within the herd, or display.

Commenting on another potential purpose for the structure, Dr Fernando Escaso (Universidad Nacional de Educación a Distancia) stated:

“The “sail” could have helped in heat exchange [thermoregulation] by releasing excess body heat into the environment as do the ears of the modern-day elephants.”

An effective heat exchanger would have been useful for such a large-bodied animal.  Everything Dinosaur team members suspect that oxygen isotope analysis from the many different types of teeth found in eastern Spain in Early Cretaceous rocks, would provide palaeontologists with a lot of information about the palaeoclimate.  For instance, some researchers claim that there was an annual average temperature range of thirty-six degrees with temperatures in excess of 40 degrees Celsius being recorded with annual lows of around 4 degrees C.

What are Styracosternan Dinosaurs?

Other media sources have cited the comment that Morelladon represents a new member of the styracosternan sub-group of the clade Iguanodontia.  What does this mean?  In the mid 1980s it had become clear to many palaeontologists that the division of the Ornithopoda into large bodied forms such as Iguanodon and Dollodon and smaller forms such as Hypsilophodon was over simplistic.

A number of academics proposed new classifications of these bird-hipped dinosaurs, for example Paul Sereno (1986) proposed a new clade within the Ornithopoda called the Ankylopollexia “stiff thumbs”.  This clade included the camptosaurs, iguanodonts, Ouranosaurus and the hadrosaurids “duck-billed dinosaurs”.  This clade was further divided by Sereno et al (1986) into the Styracosterna, which included all the Ankylopollexia members with the exception of the camptosaurids (Camptosauridae family).

1. Ankylopollexia = a clade of the iguanodontian dinosaurs
2. Styracosterna = a clade of the iguanodontian dinosaurs the same as Ankylopollexia but with the camptosaurids excluded.

Therefore, the Styracosterna dinosaurs can be divided as a sub-group of the Iguanodontia clade that contains all the “duck-billed dinosaurs” and all the dinosaurs more closely related to them than to the Camptosauridae.

Phylogenetic relationships of Morelladon beltrani within the Iguanodontia Clade

Phylogenetic relationships of Morelladon beltrani with the Styracosterna.

Picture credit: PLOS One with additional annotation by Everything Dinosaur

The diagram above shows how the Styracosterna fit into the clade Iguanodontia.   Phylogenetic analysis places Morelladon beltrani firmly in the with the styracosternan dinosaurs but more closely related to Western European iguanodonts such as Iguanodon bernissartensis and Mantellisaurus atherfieldensis than to other Iberian styracosternans such as Delapparentia turolensis and Proa valdearinnoensis.

For models and replicas of ornithopods and other prehistoric animals: CollectA Age of Dinosaurs.

Sauropod Tracks Suggest a Preference for Water

For much of the 19th and 20th centuries, those behemoths of the Dinosauria, the sauropods, were depicted as aquatic animals, at home in the deep water of large lakes, where their enormously heavy bodies could be supported by the water and their weak, peg-like teeth could cope with the soft and lush lakeside vegetation.  A substantial amount of evidence was put forward by scientists to support this hypothesis, not least of which was trackway evidence.

Most sauropod tracks were associated with soft mud, the sort of conditions found close to large bodies of water.  Therefore, it seemed logical to depict these super-sized reptiles as animals at home in lacustrine (lakes), estuaries or riverine dominated habitats.  Thanks to some remarkable Middle Jurassic sauropod footprints, this idea of long-necked dinosaurs preferring to live near to water might just be resurrected and find favour once again in palaeontological circles.

Dinosaur Tracks (Sauropoda) Discovered on the Isle of Skye

Sauropod tracks in hyporelief (Isle of Skye).

Picture credit: University of Edinburgh/Scottish Journal of Geology

Went Out for An Ichthyosaur Came Back with an Ichnogenus!

A party of scientists from Edinburgh University in collaboration with local fossil experts were working on the northern part of the Isle of Skye conducting research into the fauna and flora preserved in strata that makes up the bay just south of the ruin of Duntulm Castle.  Although it is difficult to precisely date the vertebrate fossils found in these rocks, these sediments are believed to preserve evidence of life during the Middle Jurassic and since there are only a handful of highly fossiliferous sites dating from this time in geological history to be found anywhere in the world, the Isle of Skye represents an extremely important location for scientists.

Ironically, the team, which included Dr Steve Brusatte from the School of GeoSciences (Edinburgh University), had set out to recover some Ichthyosaurus fossils but the area where the marine reptile lay remained covered by the high tide.

Sauropod Tracks

Although disappointed, the team continued to document the variety of fossils located on the foreshore and as the light from the relatively low sun cast shadows along the rocky coastline, Dr Brusatte and his colleague Dr Tom Challands came across some large lumps of raised rock.  Protruding from one lump of rock were extensions of the material that gave the distinct impression of digits and substantial claws, particularly on digits I and II.  This pattern is diagnostic of the hind footprint from a sauropod dinosaur.

The Left Hind Foot (Pes) of a Sauropod Dinosaur Isle of Skye

a = dorsal view, whilst b = anterior view, the digits are marked. Lens cap = 5 cm.

Picture credit: University of Edinburgh/Scottish Journal of Geology

The picture above shows one of the rear feet of the sauropod (left pes), the digits are marked and the lens cap, in the picture to provide scale, measures five centimetres in diameter.  The prints are in hyporelief (convex and raised).  The tracks were found in three beds in total (bed 34 and 35 provided trackways, whilst bed 9 provided single prints identified as those from a sauropod plus additional individual tridactyl prints identified as having been made by a large theropod.

The footprints, the largest of which is around seventy centimetres in diameter were made by animals that were around fifteen metres in length and weighed in excess of ten tonnes.  The tracks are the first Sauropod tracks to be found north of the border and represent the largest dinosaur known from Scotland.

Long-Necked Dinosaurs Walking Across a Salt Water Lagoon

The beds from which the prints come from also contain shark teeth, and the remains of marine molluscs.  The strata does not exhibit any signs of mud cracks or drying out, so this evidence, along with the associated fossils, suggests that the sauropods were wading across a shallow salt water lagoon.  Although an ichnogenus has yet to be assigned to these tracks, the University of Edinburgh research team have proposed that the prints are similar to the ichnogenus Breviparopus or perhaps Parabrontopodus.

Sauropod Tracks Discovered on the Isle of Skye

Concave epirelief trackways in bed 35 (Isle of Skye).

Picture credit: University of Edinburgh/Scottish Journal of Geology

If you examine the picture above carefully, you can see that despite the size of the prints, they are quite close together.  The footprints of titanosaurs for example, tend to be much wider apart.  These are “narrow gauge” prints perhaps indicative of a cetiosaurid or a diplodocid dinosaur.

To view models and replicas of sauropod dinosaurs: Mojo Fun Prehistoric Animal Models.

Implications for the Habits of Sauropods

As sauropod prints are found in three different beds it could be suggested that these dinosaurs were frequent visitors to this sort of salt water habitat.  Although, it has to be pointed out that it is difficult to determine how much time elapsed between the deposition of the different beds.  The strata could have been laid down over a few centuries or there could be thousands of years between these bedding planes.  One thing that the scientists can be fairly confident about is that between some of the beds in this area there are large concretions of limestone.

The algae and other micro-fossils such as dinoflagellate and preserved palynomorph fossils indicate that these sediments date from the Bathonian age (167.7 to 164.7 million years ago approximately).

A Line Drawing of Some of the Epirelief Prints Showing the “Narrow Gauge” of the Dinosaur Tracks

A line drawing of the sauropod trackways from bed 35.

Picture credit: University of Edinburgh/Scottish Journal of Geology

Why Live Close to Salt Water?

Dr Challands described the moment when the team became aware of the significance of their discovery as an “epiphany”.  Details of the tracks have been published in the “Scottish Journal of Geology” and these trackways and others like them found elsewhere in the world (including England), have led some palaeontologists to re-examine the evidence for sauropods being entirely terrestrial animals.  The researchers writing in the journal state:

“The Skye site presents a confluence of evidence for sauropods living in the region of a submerged lagoon over multiple generations.”

There might have been a number of advantages for the sauropods if they lived close to large bodies of water, for example:

• Sandy beaches would have made natural thoroughfares for these large creatures providing access to the edge of forests adjacent to the shoreline.
• Open areas would have limited the chances of these plant-eating dinosaurs being ambushed by theropods.
• Lagoons are associated with abundant food supplies.
• By wading or wallowing in the water these creatures would have been able to cool their large bodies very effectively.
• The salt water and mud would have provided relief from biting insects.
• Few predators would have been prepared to venture out into the lagoon to hunt the sauropods.

The Isle of Skye in the Middle Jurassic

The Isle of Skye (Bathonian faunal stage).

Picture credit: Jon Hoad

The illustration above shows two sauropods on the mud flats of the lagoon, whilst in the foreground a small, theropod (Ornitholestinae subfamily) looks on warily.

A Significant Middle Jurassic Discovery

Commenting on the trace fossils and their importance to palaeontology, Dr Brusatte stated:

“The Middle Jurassic was a really interesting period in the history of life, when there was a whole lot of evolution going on. What is really frustrating is that we have a lot of fossils from different places with fossils from the Early Jurassic and the Late Jurassic, but there is relatively little fossil-bearing Middle Jurassic rock around.”

The Isle of Skye fossils pose some intriguing questions, these tracks most likely were made by primitive sauropods at a time when the Sauropoda were beginning to radiate, differentiate and evolve into a number of new forms.

In addition, the strata preserves evidence of multiple generations of sauropods inhabiting lagoonal environments, which suggests the intriguing possibility that these huge creatures might have sought out such habitats, preferring them to inland areas.

Do these tracks preserve evidence of Isle of Skye sauropods and their water world?

Scientists Use Chinese Cretaceous Turtle Fossils to “Crack” Turtle Evolution

Turtles and tortoises are representatives of a very ancient group of reptiles and scientists have much still to learn about their origins and how the Chelonia (the name given to tortoises, turtles and terrapins) evolved, but new research by a joint German, Hungarian and Chinese research team is helping to shed some light on these shelled creatures.  The scientists have been studying the beautiful, fossilised remains of Early Cretaceous turtles from north-eastern China in a bid to determine how the first sea turtles arose.

The extant sea turtles found today, represent just a tiny portion of what was once, a hugely diversified group.  There are just seven species, the majority of which are very vulnerable to extinction.  The first sea turtle fossils appear in Cretaceous aged rocks some 130 million  years old, it is very likely that these marine animals evolved from a common, freshwater ancestor, although this ancestor has yet to be identified.

A New Study of the Jehol Biota

In this new study, Dr Chang-Fu Zhou of the Shenyang Normal University of Liaoning and Dr Márton Rabi of the Biogeology Workgroup of the University of Tübingen and the Hungarian Academy of Sciences tried  to identify the ancestors of modern sea turtles from amongst the many excellent turtle fossils that represent the famous Jehol Biota of the Early Cretaceous of north-eastern China.

An Example of One of the Exquisitely Preserved Turtle Fossils Affiliated to the Jehol Biota

The newly-described fossil species, Xiaochelys ningchengensis from north-eastern China’s Jehol Biota; right: an illustration of the skeleton incorporating positive and negative impressions preserved in the layers of stone.

Picture credit: Chang-Fu Zhou

The picture above shows the slab and counter slab of the newly described Cretaceous turtle Xiaochelys ningchengensis from north-eastern China.  To the right of the photograph a line drawing has been produced to show the preserved features of the shell (scale bar = 20 mm).

The Importance of the Jehol Biota

The Jehol Biota is a rich Cretaceous ecosystem preserved in a multi-layered rock formation cropping out in the Chinese provinces of Liaoning, Hebei and Inner Mongolia.  The habitat represented is that of a temperate forest zone, with large lakes in situ.  Nearby, volcanoes occasionally covered the area in fine ash and this led to the exquisite preservation of many of the fossils to be found in these regions.  The most famous fossils associated with these strata are feathered dinosaurs, animals such as Sinosauropteryx, Sinornithosaurus, Microraptor and the recently described  Zhenyuanlong suni.

To read an article about the significance of the Jehol Biota: Unravelling the Sequence of Deposition in North-eastern China.

To read an article about the “winged dragon”  Zhenyuanlong suni: A New “Winged Dragon” from China.

North-eastern China Around 130-125 Million Years Ago

A rich and diverse environment dominated by small mammals, pterosaurs and feathered theropods.

Picture credit: Julia Molnar

Models of Prehistoric Animals

PNSO of China have created a range of prehistoric figures, many of which represent pterosaurs, dinosaurs and other creatures associated with the Jehol Biota: PNSO Age of Dinosaurs.

Ironically, despite this part of the world’s connection with feathered dinosaurs, the first vertebrate of the Jehol Biota to be described was a freshwater turtle (1942).

Xiaochelys ningchengensis – A New Species of Freshwater Turtle

The research team have described a new species of freshwater turtle, adding to the rich vertebrate assemblage known to have existed in this part of the world during the Early Cretaceous.  A study of the fossils of X. ningchengensis was undertaken to ascertain whether this ancient turtle, whose shell was not much bigger than a saucer, was a potential ancestor of today’s sea turtles.

Dr Zhou and Dr Rabi applied comparative morphological assessment techniques to try to map this turtle’s position in relation to other members of the Chelonia, this produced a comprehensive phylogeny diagram of turtle evolutionary relationships leading to today’s living turtle species.  The scientists wanted to test an earlier hypothesis that the Jehol Biota turtles belong to a lineage that eventually gave rise to extant marine reptiles.

Dr Zhou explained:

“According to our findings, the Jehol turtles are instead found on the lineage leading to the Cryptodiran turtles.”

An Illustration of Xiaochelys ningchengensis

An illustration of the freshwater turtle Xiaochelys.

Picture credit: W. S. Wang

Xiaochelys ningchengensis

In the picture above, the small, freshwater turtle Xiaochelys ningchengensis has caught a fish (Lycoptera spp.) fossils of these fish are associated with the same strata as the X. ningchengensis material.  Xiaochelys (pronounced sho-ow-key-lis) comes from the Chinese Pinyin “Xiao” a reference to the small size of this taxon and the Greek for turtle “chelys”.  The trivial name honours the type locality, Ningcheng County (Inner Mongolia).  The research has been published in the latest edition of the academic journal “Scientific Reports”.

The cryptodires, which also include sea turtles, are able to pull their heads and necks vertically into their shells using an S-shaped motion.  The statistical analysis only just placed the likes of Xiaochelys outside the ancestral line of modern turtles, so it is quite likely that this Cretaceous turtle was quite similar to those types of turtle that were ancestral to the modern forms.

Dr Zhou added:

“These well-preserved fossils give us insights into the origin of cryptodires.  About three-quarters of today’s turtles belong to that group.”

Evolutionary Changes

It is not clear however, just how the main adaptations of marine turtles arose.  These evolutionary changes included the reduction of their skeleton and the development of large, rigid paddles which enable the creatures to swim in a style which is best described as “flying underwater”.  The Chelonia, throughout their long evolutionary history seemed to have evolved into a myriad of forms with several lineages “flipping” between a terrestrial and fully aquatic existence.  Scientists still don’t really understand how the Chelonia evolved and changed since they first appeared many millions of years ago.

Everything Dinosaur acknowledges the help of Tübingen University in the compilation of this article.

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