Kapes bentoni Saved by a Scan

The fossilised remains of a little reptile that roamed the land we now know as Devon has helped make links with the prehistoric vertebrate fauna of the Middle Triassic of Russia.  Thanks to the use of computerised tomography (CT) scans, palaeontologists have had the rare opportunity to study the skull and postcranial elements of a procolophonid reptile.  The fossil was found by co-author of the scientific paper, Dr Rob Coram of Swanage in November 2014, from a foreshore exposure of the Pennington Point Member of the Otter Sandstone Formation located close to the town of Sidmouth on the south Devon coast.

The Triassic sandstone deposits in these cliffs, which ironically form part of the famous UNESCO World Heritage site the “Jurassic Coast” contain vertebrate remains, but they are quite rare and often show signs of extensive weathering and transportation prior to burial and fossilisation.

The Fossil Specimen (BRSUG 29950-13) and Two Computer Generated Images

Picture credit: Bristol University/Papers in Palaeontology

Procolophonid Reptiles (Procolophonidae)

The reptile has been identified as an example of Kapes bentoni, several species are included in this genus, all of which, including the type species K. amaenus, which was named in 1975, come from Russia.  Procolophonids looked superficially like lizards, but they are not closely related to the Squamata.  They are parareptiles, which evolved in the Permian and had a wide distribution during the Triassic, before becoming extinct shortly before the Triassic came to an end.  When Dr Coram tried to clean and prepare the fossil, he found that the fossil material was too fragile and conventional preparation techniques would have resulted in permanent damage to the fossil bones.

Dr Coram commented:

“I tried everything I could.  I have had a lot of experience of removing rock from fossils using a fine needle and working under the microscope, but this was a nightmare.  When I touched it with a needle, small pieces of bone fell off.”

CT Scanning the Devon Fossil

In order to allow the fossil to be studied, Dr Coram contacted colleagues at Bristol University and a CT scan of the small fossil was organised.  The job of interpreting the scans and the resulting computer generated images was given to PhD student Marta Zaher, who was at the Bristol University for a few months, normally she is based in Zagreb (Croatia).  The three-dimensional scans of the skull and postcranial material turned out to be far better than the scientists had hoped.  Even wear facets on the tiny teeth of the Kapes specimen could be discerned and studied.

Once all the scans had been compiled the researchers could examine the procolophonid fossil in great detail.  Most of the procolophonid fossils from England are highly fragmentary, but the scans revealed the presence of a skull, cervical vertebrae, the shoulder girdle, forelimbs and the front half of the torso.

An Illustration of the Skeleton of Kapes bentoni (Lateral and Dorsal Views)

Picture credit: Bristol University/Papers in Palaeontology

Spectacular CT Scans of a Triassic Specimen

Student Marta explained:

“The scans are amazing.  They show every detail of the tiny, five-centimetre (two inch) long skull.  You can see each tooth, and even the wear patterns.  Almost all the tiny bones of the palate and braincase are there.”

She added:

“This identifies the animal without question as a procolophonid.  These lived worldwide at the time, and they were important plant-eaters, with broad teeth fused to their jaws, and which wore down under grinding from the tough plant food.”

Several years ago, less complete specimens of the procolophonid had been found in the Devon rocks, and two academics then at the University of Bristol, Patrick Spencer and Glenn Storrs, had suggested the Devon animal was the same as Kapes from central Russia.

A spokesperson from Everything Dinosaur commented:

“Thanks to the use of computerised tomography, the researchers were able to get an unprecedented insight into the anatomy of an anapsid.  This non-destructive technique has helped scientists to identify that this Devon specimen is very closely related to other reptiles, fossils of which come from the terrestrial red beds of Russia.”

A Diagram of the Skull Produced from the CT Scan Data

Picture credit: Bristol University/Papers in Palaeontology

Co-author of the scientific paper published in “Papers in Palaeontology”, Professor Mike Benton (Bristol University) stated:

“The new study confirms that the two animals are very close relatives, two species of the genus Kapes.  This is most unusual, to have evidence of a biogeographic connection over thousands of kilometres.  In the Middle Triassic, there was dry land in the UK and in Russia, but the area in between was filled with the Muschelkalk Sea, covering Germany and much of central Europe.”

Kapes bentoni

Many of the early procolophonids were insectivorous, however, Kapes bentoni was a plant-eater.  This idea is reinforced by the heavy wear on the teeth as observed in the CT scans from this study.  K. bentoni had a short, stocky body and it may have been fossorial (lived in a burrow).  The spines on the skull have provided the scientists with a bit of a puzzle.  It has been suggested that these spines had a defensive function, making the reptile seem bigger and more intimidating to a potential predator.  The spines would also have obstructed any predator attempting to swallow Kapes head-first.

A Life Reconstruction of the Procolophonid Kapes bentoni

Picture credit: Marta Zaher

The scientific paper: “The Middle Triassic Procolophonid Kapes bentoni: Computed Tomography of the Skull and Skeleton” by Marta Zaher, Robert A. Coram and Michael J. Benton published by Papers in Palaeontology.

Everything Dinosaur acknowledges the assistance of a press release from Bristol University in the compilation of this article.

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Plotting the Evolution of the Alvarezsauridae with Bannykus and Xiyunykus

A team of international scientists writing in the journal “Current Biology” have published details of two new Chinese alvarezsaurid dinosaurs that will help palaeontologists to better understand the evolution of this group of bizarre theropods.  Some later genera becoming the  prehistoric equivalents of today’s aardvarks and anteaters.  The dinosaurs have been named Bannykus and Xiyunykus and their fossilised bones are proving handy, as palaeontologists seek to understand how the alvarezsaurian dinosaurs reduced and lost most of their digits, except the thumb, which became very large and robust.  These sleek, fast-running and very bird-like dinosaurs seemed to have become very specialised over some ninety million years.

Two Newly Described Chinese Dinosaurs Help to Plug an Evolutionary Gap in the Alvarezsauridae

Picture credit: Viktor Radermacher

Chinese Alvarezsaurid Dinosaurs

The Alvarezsauroidea have a long history, basal forms such as Haplocheirus lived in Asia around 160 million years ago and the very last members of the Alvarezsauridae family were present in the Late Cretaceous, a temporal range of at least ninety million years.

The last of these bizarre, very bird-like dinosaurs have been classified into the sub-clade Parvicursorinae and these animals seem to have been very specialised insect eaters, with a strong single thumb digit with an oversized claw, powerful arm and chest muscles (although the length of the arm was much reduced), long snouts, with thin narrow jaws.  It has been speculated that these dinosaurs could rip apart the nests of termites or dig into logs to find insects.  It has even been suggested that they evolved a long tongue to help them lap up their prey in the same way that an extant anteater does.

The earliest alvarezsaurids were not insectivores, dinosaurs like Haplocheirus were probably hunters of small vertebrates.  Haplocheirus (H. sollers), had the teeth of a typical meat-eating theropod and grasping hands to catch prey.  Only later alvarezsaurids had much reduced teeth and evolved a hand with a single, large curved thumb claw.

Digit Reduction in Tetrapods

The loss of fingers and toes has occurred numerous times amongst tetrapods.  Perhaps the most famous example of all, is the evolution of the foot of the horse.  It was the notable American palaeontologist Charles Othniel Marsh, who plotted the evolution of equines by studying the toe bones of ancient horses.  Marsh was able to demonstrate how primitive horses gradually lost their toes evolving into the single-toed, fast running animal we know today.

To read more about the contribution of Marsh and the evolution of horses: The Contribution of Othniel Charles Marsh.

Both Bannykus and the slightly smaller Xiyunykus are important because they show transitional steps in the process of alvarezsaurs adapting to new diets.

Mapping the Evolutionary History of the Alvarezsauroidea

Picture credit: Current Biology

The image (above) shows the temporal position of the two, newly described species.  Both Xiyunykus and Bannykus lived during the Early Cretaceous, their fossils are helping to bridge a seventy million year gap between Late Jurassic basal forms and the advanced and highly specialised Late Cretaceous forms.

Xiyunykus pengi

Xiyunykus was the first of these new dinosaurs to be discovered.  Its fossils were found in 2005, by an international expedition to the Junggar Basin (Xinjiang Uyghur Autonomous Region of north-western China).  The fossil remains consist of a partial, disarticulated skeleton and the material has been dated to the Barremian-Aptian faunal stages of the Early Cretaceous.  The researchers, including Xu Xing from the Institute of Vertebrate Palaeontology and Palaeoanthropology (IVPP) have estimated that this dinosaur weighed around fifteen kilograms.

Skeletal Remains of Xiyunykus pengi

Picture credit: Current Biology

A cross-sectional analysis of lower leg bone (B) in the image above, indicates that this dinosaur was around nine years of age when it died and probably a sub-adult.  The genus name is from “Xiyu”, the Mandarin for denoting the western regions of Central Asia and from the Greek “onyx” meaning claw.  The trivial name honours Professor Peng Xiling, who has played a significant role in the study of the geology of this region.

 Bannykus wulatensis

The second alvarezsaurid was discovered in 2009 in western Inner Mongolia.  The fossils come from the Bayingobi Formation  (Aptian faunal stage of the Early Cretaceous).  Histological analysis of a cross-section of bone taken from the fibula indicates that this dinosaur was around eight years of age when it died. It, like the Xiyunykus specimen, was probably a sub-adult.

Skeletal Remains of Bannykus wulatensis

Picture credit: Current Biology

The genus name comes from the Mandarin “Ban” meaning half, a reference to the transitional anatomical features seen in this dinosaur and “onyx”, from the Greek for claw.  The trivial name refers to Wulatehouqi (Wulate Rear Banner), the county-level administrative division in which the type locality is situated.

Long Arms and Grasping Hands to Reduced Arms and Digits

These two newly described Alvarezsaurian dinosaurs have helped to determine that these peculiar Theropods very probably originated in Asia, before migrating to other parts of the world such as North and South America over their long evolutionary history. Bannykus and Xiyunykus are important because they show transitional steps in the process of alvarezsaurs adapting to new ecological niches, Bannykus, which may have lived slightly later than Xiyunykus, is showing signs of that mechanically efficient forearm, a more robust and powerful upper arm and an enlarged thumb.

The Manus (Hand) of Bannykus Showing a Transitional Stage in Alvarezsaurid Evolution

Picture credit: Current Biology

Still a Puzzling Group of Bird-like Dinosaurs

The discovery and scientific description of these new members of the Alvarezsauridae is very significant.  These fossils will help scientists to better understand the evolution of the specialised hand of alvarezsaurids and provide assistance when it comes to phylogenetic placement for group members.

Lead author of the scientific paper, Xu Xing commented on the evolutionary changes that had been highlighted stating:

“This transition plays out in an incremental fashion over more than 50 million years.  It could one day potentially serve as a classic example of macroevolution akin to the ‘horse series’ of North America.”

These dinosaurs are some of the more bizarre and peculiar forms of theropod.  Ancestral forms seemed to have anatomical features quite typical of carnivorous dinosaurs, before evolving much more specialised forms, probably in response to exploiting a particular ecological niche.

Co-author James Clarke (George Washington University), added:

“The fossil record is the best source of information about how anatomical features evolve and like other classic examples of evolution such as the “horse series,” these dinosaurs show us how a lineage can make a major shift in its ecology over time.”

Chinese Alvarezsaurid Dinosaurs – A Puzzle

The alvarezsaurian dinosaurs remain a puzzle.  They may have evolved into specialist insectivores, but they retained their long legs and the ability to run fast throughout their evolutionary history.  The forelimbs, hands and digits may have undergone a radical change, but these dinosaurs always seem to have remained quite graceful and agile animals.

Why these animals retained their ability to run very quickly when their prey was to be found in a termite mound or a rotting log is not clear.  However, it is likely, that the ability to run fast was continued to be selected for in this group as an adaptation to avoiding being eaten by larger predatory dinosaurs.

Palaeontologists Xu Xing and James Clarke Searching for Dinosaur Fossils

Picture credit: Xu Xing

The scientific paper: “Two Early Cretaceous Fossils Document Transitional Stages in Alvarezsaurian Dinosaur Evolution” by Xing Xu, Jonah Choiniere, Qingwei Tan, Roger B.J. Benson, James Clark, Corwin Sullivan, Qi Zhao, Shuo Wang, Hai Xing and Lin Tan published in Current Biology.

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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.  Slowly but surely scientists are learning more about turtle evolution.

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

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

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.

Turtle Evolution

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

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.

Chinese Fossil Discovery

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.

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