All about dinosaurs, fossils and prehistoric animals by Everything Dinosaur team members.
23 08, 2018

Turtle Evolution – Complicated

By | August 23rd, 2018|Dinosaur and Prehistoric Animal News Stories, Dinosaur Fans, Main Page, Palaeontological articles, Photos/Pictures of Fossils|0 Comments

Oldest Turtle with a Beak but No Shell – Eorhynchochelys sinensis

A beautifully preserved and very nearly complete fossilised skeleton of a turtle is helping scientists to unravel the evolutionary story of these ancient reptiles.  However, it seems that the evolution of turtles, tortoises and terrapins (the Order Testudines, sometimes referred to as the Chelonii), may be even more complicated than previously thought, just like a large terrapin in a small aquarium, the discovery of this new fossil, might just have muddied the water somewhat.

A Life Reconstruction of the Newly Described Late Triassic Turtle Eorhynchochelys sinensis

Eorhynchochelys sinensis life reconstruction.

A life reconstruction of Eorhynchochelys sinensis.

Picture Credit: Yu Chen (Institute of Vertebrate Palaeontology and Palaeoanthropology)

Early Turtle From the Late Triassic

The skeleton was excavated from Upper Triassic rocks in Guanling County, (Guizhou Province, south-west China).  It has been named Eorhynchochelys sinensis, the name means “dawn turtle with a beak from China”.  As the scientific name suggests, this is the oldest turtle ever found with a toothless beak.  Its discovery might help to close a gap in the evolutionary history of the Chelonii, as although it did not have a shell (the fossil lacks a carapace or plastron), the skull is very similar to the skull of extant turtles, but the rest of the animal’s skeleton resembles that of an earlier basal turtle that lived some ten million years previously.  Eorhynchochelys was over two metres long and it lived in an estuarine environment, it was most likely amphibious and the presence of strong claws and well-developed forelimbs suggests that this ancient animal may have lived in a burrow.

A View of the Fossil Material E. sinensis

Eorhynchochelys sinensis fossil - an early turtle without a shell.

Eorhynchochelys sinensis fossil (dorsal view).

Picture Credit: National Museums of Scotland

Mosaic Evolution

The researchers, which included scientists from the National Museums of Scotland, the Chicago Field Museum, the Canadian Museum of Nature and the Institute of Vertebrate Palaeontology and Palaeoanthropology in Beijing, were intrigued by the modern-looking turtle skull with its characteristic edentulous (toothless) beak.  This feature had not been seen in early fossil turtles before and the dating of  Eorhynchochelys indicates that this trait seems to have disappeared in some lineages and reappeared millions of years later.  This suggests that the evolutionary development of the Chelonii was much more complicated, after all, here was a Late Triassic ancestral turtle with a modern-looking skull but lacking a shell, although the broad, enlarged ribs and other anatomical features of the skeleton indicated that this type of reptile was on the way to evolving such a feature.

The fact that Eorhynchochelys developed a beak before other early turtles but didn’t have a shell is evidence of mosaic evolution, the idea that characteristics can evolve independently from each other and at a different rate and that not every ancestral species has the same combination of these traits.  All living turtles have both shells and toothless beaks, the evolutionary path that led to these traits was not a simple linear progression.  Some ancient turtles evolved partial shells, whilst others evolved beaks, eventually the genetic mutations and natural selection that allowed these traits to develop became unifying characteristics of the group as a whole.

A Life Reconstruction of the Head of Eorhynchochelys

Eorhynchochelys sinensis with its beak.

An illustration showing the head of Eorhynchochelys sinensis with its beak.

Picture Credit: Institute of Vertebrate Palaeontology and Palaeoanthropology

Family Links

Although the discovery of Eorhynchochelys sinensis helps to provide further information on the evolution of turtle traits, it does not resolve a long-standing argument about where in the Class Reptilia the Testudines (Chelonii), should be placed.  However and whenever these reptiles evolved their characteristic features might be complicated, but it seems that by around 210 million years ago, the turtle body plan with its carapace, plastron and beak had come about and this group have remained relatively unchanged since.  The Testudines seem to lack a feature that is common in most other reptiles, a pair of holes (fenestrae), in their skulls behind the eyes.  For many years, turtles were thought to be anapsids (members of the  Anapsidae), a very primitive subclass of the Reptilia.  Genetic studies have suggested that turtles, tortoises and terrapins are closely related to diapsid reptiles and their close relatives, Archosaurs such as crocodilians, dinosaurs and birds.  However, other studies have concluded that turtles and their kind might actually, be more closely related to snakes and lizards (Squamata).

Eorhynchochelys had a single pair of holes behind its eye sockets, this might suggest an anapsid origin or it might indicate that Eorhynchochelys is a transitional form that evolved from diapsid ancestors.

Commenting on the taxonomic position of the Chelonii in the light of this new Chinese fossil discovery, co-author of the research, Xiao-Chun Wu (Canadian Museum of Nature), explained that when the physical characteristics of Eorhynchochelys were considered in an analysis with other fossilised reptiles, it is likely that turtles are not closely related to either the Archosauria or the Squamata, but it is more likely that they are an offshoot from earlier, more primitive reptiles.

In the absence of more fossils, this debate is not going to be resolved anytime soon.

To read an article from 2013 looking at research into the evolution of Chelonians: How the Turtle Got Its Shell

For an article that discusses the discovery of Pappochelys rosinae a basal turtle that lived some 20 million years earlier than Eorhynchochelys, that has been classified as a diapsid but had the beginnings of a plastron: Pappochelys – The Grandfather of the Chelonii

23 08, 2018

William Draws Dinosaurs

By | August 23rd, 2018|General Teaching|Comments Off on William Draws Dinosaurs

Dinosaur Drawings By William

Our thanks to young dinosaur fan William who kindly sent in a drawing of two of his favourite dinosaur models.  At Everything Dinosaur, we get sent lots of dinosaur and prehistoric illustrations and we like to post these up in our warehouse.  William wrote to thank Everything Dinosaur team members for supplying the dinosaur figures.

William’s Dinosaur Drawing

William's drawing of dinosaur models.

A drawing of dinosaur models sent to Everything Dinosaur by William.

Picture Credit: William

Not only has William chosen to illustrate some dinosaurs for us, but he has produced a lovely copy of our company logo, a large letter “e” that represents a three-toed dinosaur footprint as well as the first letter of our company’s name.  Congratulations to William, for the drawings and for the clear and well-spaced writing.

Drawing the Armoured Dinosaur Ankylosaurus

Lots of children are fascinated by dinosaurs and many schools utilise this love of all things dinosaur as they deliver dinosaur-themed term topics.  Learning about ferocious and thankfully, extinct creatures from the past can really help to motivate and enthuse young learners when it comes to gaining confidence with numbers and improving writing skills.  William for example, as chosen to illustrate one of his favourite dinosaur models – Ankylosaurus.  It we compare William’s drawing to a model of this armoured dinosaur, it is clear that William has taken great care over his work.

William Draws an Ankylosaurus

William draws Ankylosaurus.

William’s Ankylosaurus drawing compared to the Ankylosaurus model.

Picture Credit: William/Everything Dinosaur

William Draws the Fearsome Mapusaurus

In addition, to his armoured dinosaur illustration, William chose to draw a picture of a Mapusaurus.  Mapusaurus, (as we are sure William will know), was a large, carnivorous dinosaur, fossils of which come from Argentina. It was probably the largest predator in its environment, with some palaeontologists estimating that Mapusaurus weighed around six tonnes and measured more than twelve metres long.

William Draws Mapusaurus

William draws Mapusaurus.

William’s Mapusaurus drawing compared to the Mapusaurus model.

Picture Credit: William/Everything Dinosaur

Once again, we congratulate William on the accuracy of his drawing, team members at Everything Dinosaur were able to recognise that this was an illustration of the CollectA Mapusaurus dinosaur model.

Our thanks to William for his drawing and to his kind mum Anna who gave it to us.  We hope you liked the fact sheets that accompanied the models that we supplied.

We noted the suggestion for CollectA to produce a model of a Sabre-tooth Cat cub, this suggestion along with the illustration will be forwarded onto our chums at CollectA.

The CollectA range of prehistoric animal figures that helped inspire William can be viewed here: CollectA Prehistoric Life Models and Figures

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