Members of the Pterosauria Undergo Dental Examination

Visiting the dentist can be a daunting experience for some, but for seventeen different species of pterosaur, a microscopic analysis of wear on the teeth has provided palaeontologists with a fresh perspective on the diets and lifestyles of these enigmatic flying reptiles.

Scientists from the University of Birmingham and the University of Leicester’s Centre for Palaeobiology Research studied dental wear patterns preserved on the fossilised teeth of the specimens and then compared these wear patterns to those found on the teeth of living reptiles including crocodilians and monitor lizards whose diets are known.

A Newly Published Scientific Paper Reveals New Data on the Diets of Pterosaurs

Picture credit: Mark Witton

Studying Pterosaur Teeth

The researchers were able to demonstrate for the first time how microscopic dental wear analysis can be used to inform palaeontologists about the diet of an extinct animal but to also challenge existing ideas and perceptions about lifestyle and behaviour.

The scientific paper detailing their results are published in the academic journal “Nature Communications”.

Lead author of the study, Dr Jordan Bestwick (University of Birmingham’s School of Geography, Earth and Environmental Sciences), commented:

“Most existing ideas about what pterosaurs ate come from comparisons of the shapes of their teeth with those of living animals.  For example, if the animal had conical teeth like a crocodile, we might assume it ate fish.  But this approach has obvious shortcomings – the teeth of pandas and polar bears, for example, are similar, but comparing them wouldn’t give us an accurate picture of their diets.”

Did Some Super-sized Pterosaurs Eat Dinosaurs?

Picture credit: Mark Witton

Durophagus Diets

The analysis showed that modern reptiles with rougher wear on their tooth surfaces are more likely to have eaten crunchy things, such as shelled invertebrates – beetles or crabs.  Eating hard-shelled animals or creatures with a tough exoskeleton such as some types of insect is referred to as durophagy.  Reptiles which eat mainly soft items, such as fish, have smoother tooth surfaces, which show less wear.  By applying the technique to pterosaurs, the scientists were able to comment on the likely diet of each species.

Dr Bestwick added:

“Our analysis has yielded some fascinating insights into individual species, but also into some of the bigger questions around how these pterosaurs evolved and whether their lifestyles were more similar to those of extant birds or reptiles.  Evidence from dental microwear analysis can shed new light on this debate.”

Professor Mark Purnell, Professor of Palaeobiology at the University of Leicester explained:

“This is the first time this technique has been applied in this way to ancient reptiles, and it’s great to find it works so well.  Often, palaeontologists have very little to go on when trying to understand what extinct animals ate.  This approach gives us a new tool, allowing us to move from what are sometimes little more than educated guesses, into the realms of solid science.”

Examining the Diet of Rhamphorhynchus

In one example, the team examined the teeth of Rhamphorhynchus, a long-tailed pterosaur from the Jurassic period.  Researchers found that juvenile Rhamphorhynchus had insect-based diets, whereas their adult counterparts – about the size of a large seagull – were more likely to have eaten fish.  This suggests a species in which the adults took little care of their young (precocial behaviour) – a behaviour that is common in reptiles and is not exhibited by birds.

A Rhamphorhynchus Illustration (R. muensteri)

Picture credit: Everything Dinosaur

Looking at Pterosaur Evolution

The research team also investigated whether their analysis could shed light on how different species of pterosaurs evolved.  The first pterosaurs evolved during the Triassic and they survived until the very end of the Mesozoic some 66 million years ago, becoming extinct at the same time as their archosaur relatives the dinosaurs.  In that time, according to the dental microwear analysis, there was a general shift in diet from invertebrates such as insects, towards a more meat or fish-based diet.

Commenting on the potential significance of this dietary shift, Dr Bestwick stated:

“We found that the earliest forms of pterosaurs ate mainly crunchy invertebrates.  The shift towards eating fish or meat coincides with the evolution of birds.  We think it’s possible, therefore, that competition with birds could explain the decline of smaller-bodied pterosaurs and a rise in larger, carnivorous species.”

Birds Competing with Pterosaurs

It is an intriguing thought, although the fossil record of the Pterosauria is far from complete and there is a degree of bias towards the most productive pterosaur-fossil bearing strata such as deposits associated with the Crato and Santana Formations of the Early Cretaceous, which prevents a detailed assessment of pterosaur diversity over the duration of the Mesozoic from the Norian onwards.

Natalia Jagielska, a PhD researcher in pterosaur palaeontology based at the University of Edinburgh, (not involved in this study), commented that the research adds much-needed clarity to the behaviour and ecological role of pterosaurs in ancient food webs.

“Pterosaurs are a fascinating group of Mesozoic reptiles with astounding diversity in tooth morphology.  This study is important for contributing to the idea that young Rhamphorhynchus were independent invertebrate hunters before becoming fish consumers, rather than being fed and nurtured by parents, like birds.  Or that in pterosaur-rich environments, like the Late Jurassic Bavarian lagoons, pterosaur species have partitioned to occupy variations of dietary niches.”

The authors of the scientific paper are confident that this new research will provide a benchmark assisting in the interpretation of the diet of long extinct reptiles and in doing so, will lead to an improved understanding of ancient ecosystems.

Everything Dinosaur acknowledges the contribution of a media release from the University of Birmingham in the compilation of this article.

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A New Basal Abelisaurid – Spectrovenator ragei

Researchers from the Universidade de São Paulo (Brazil), in collaboration with colleagues from the Museo Paleontológico Egidio Feruglio (Argentina), have described a new species of basal abelisaurid from the Early Cretaceous of Brazil.  The theropod has been named Spectrovenator ragei, the genus name translates from the Latin as “Ghost Hunter” as the fossilised remains were found unexpectedly underneath the holotype of the titanosaur Tapuiasaurus macedoi when the fossils of this dinosaur were being partially prepared by the field team.

An Illustration of Spectrovenator ragei with Key Fossils Highlighted that Help to Define the Dinosaur’s Taxonomy

Picture credit: Zaher et al

Spectrovenator ragei

The species or trivial name honours the late Dr Jean-Claude Rage, an eminent French researcher who made a significant contribution to the study of South American Mesozoic vertebrates.

Described from a partially articulated skeleton including a virtually complete skull, the dinosaur is thought to have measured around 2.2 metres in length and it is the first Early Cretaceous abelisaurid known with an almost complete skull.  The cranial material has helped the researchers to demonstrate the evolution of abelisaurid skulls from the earliest, most basal Eoabelisaurus to the abelisaurids that existed in Gondwana during the later stages of the Cretaceous.

Views of the Skull with Accompanying Line Drawings

Picture credit: Zaher et al

A Dinosaur Skull to Study

With a beautifully preserved skull to study, the scientists have been able to compare the function of the skull and jaws of Spectrovenator with more derived members of the Abelisauridae.  The Early Cretaceous Spectrovenator (Barremian-Aptian), lacks the specialisations, such as a high occipital region and highly flexible jaw joints linked to a modified feeding strategy suggested for much later abelisaurids.  For example, some scientists, think that large-bodied abelisaurids such as Carnotaurus (C. sastrei) specialised in hunting titanosaurs (large prey).

The lack of these specialisations in the skull of Spectrovenator suggests this modified feeding strategy may be restricted to Late Cretaceous abelisaurids and linked to an increase in body size by this type of predatory dinosaur which occurred during the Cenomanian and through to the Maastrichtian.

Phylogenetic relationships of Spectrovenator within the Ceratosauria

Picture Credit: Zaher et al

Understanding the Abelisauridae

The discovery of Spectrovenator helps to fill a sizeable gap in the evolutionary history of the Abelisauridae.  The earliest member of the Abelisauridae described to date Eoabelisaurus (E. mefi), is known from the Middle Jurassic of Argentina (around 166 million years ago), whilst other abelisaurids such as Rugops and Skorpiovenator are known from Upper Cretaceous sediments (100 million years ago approximately).  Whereas Spectrovenator was found in strata that is approximately 120 million years old.

The scientific paper: “An Early Cretaceous theropod dinosaur from Brazil sheds light on the cranial evolution of the Abelisauridae” by Hussam Zaher, Diego Pol, Bruno Albert Navarro, Rafael Delcourt and Alberto Barbosa Carvalho published in Comptes Rendus Palevol.

The Everything Dinosaur website: Everything Dinosaur.

Sensitive Probe Feeding Pterosaurs

Whilst it is not always sensible to compare the Pterosauria to birds, they do have a number of things in common.  As vertebrates they may not be very closely related but both birds and pterosaurs share some common anatomical characteristics that have helped them to conquer the sky.  Their skeletons show special adaptations to assist with powered flight and if we focus on modern birds for a moment, we can see that many forms have evolved to occupy different niches in ecosystems.  For example, some birds such as vultures and condors are primarily scavengers, whilst others are active predators (eagles, hawks and falcons).

Yet more are omnivores and some such as flamingos (filter feeders), swifts (aerial insect hunters) and hummingbirds (nectar feeders) occupy very specialist roles within food chains.

Studying the Beaks of the Pterosauria

Although the known fossil record of the Pterosauria probably grossly under-represents these flying reptiles, palaeontologists are becoming increasingly aware of the diversity of this enigmatic clade.  Around 130 genera have been described, probably only a fraction of the total number of genera that evolved during their long history and recently a combination of fossil finds from Morocco in conjunction with a re-examination of fossils from a chalk pit near Maidstone in Kent (England), has led researchers to propose yet another environmental niche for pterosaurs.

Some pterosaurs evolved sensitive beaks that allowed them to probe sediments to help them find food just like many types of modern wading birds and members of the Aves such as the kiwi.

A Life Reconstruction of the Lonchodectid Lonchodraco giganteus Probing in the Mud to Find Food

Picture credit: Megan Jacobs (The University of Portsmouth)

Unusual Foramina in a Fossil Specimen

Researchers from the University of Portsmouth in collaboration with Dr Nicholas Longrich (University of Bath), took a close look at the fragmentary remains of the anterior of the rostrum (front of the jaws), of the pterosaur Lonchodraco giganteus (formerly referred to as Lonchodectes giganteus).  These fossils had been found in a chalk pit, close to the village of Burham, near Maidstone, Kent.  They were originally described as a species of Pterodactylus by the British naturalist James Scott Bowerbank in 1846.

Lonchodraco giganteus Holotype Jaws

Picture credit: Martill et al (Cretaceous Research)

Extremely Fragmentary Pterosauria Fossil Remains

Like many pterosaur fossils from southern England, the fossilised remains are extremely scrappy, more recent studies have assigned these remains to the little-known lonchodectid pterosaurs (Lonchodectidae family).  These types of pterosaurs are united by having low profile jaws, raised teeth sockets and uniformly small teeth.

In a study of the holotype rostrum and mandible of L. giganteus, dozens of tiny holes (foramina) were discovered in the beak tip.  These are thought to represent sensory areas on the beak, where nerves pass through the bone and make contact with the beak’s surface.  Although foramina have been observed in the Pterosauria before, the pattern identified on the tip of the rostrum of Lonchodraco is unique.

Lonchodraco giganteus Holotype (Anterior View)

Picture credit: Martill et al (Cretaceous Research)

Identifying Nerve Clusters

These types of nerve clusters are reminiscent to those found in living birds such as kiwis, sandpapers, spoonbills, geese, ducks and snipes.  These birds rely on their sense of touch when finding and catching food.  Typically, they either probe in water, mud, sand or soil to locate and catch prey.  This research, in combination with a second paper that also postulates on probe-feeding behaviour in the Pterosauria, suggests that just like modern birds, the pterosaurs were capable of evolving into a myriad of forms to exploit different food sources.

Concentration of Foramina at the Jaw Tips (Lonchodraco giganteus)

Picture credit: Martill et al (Cretaceous Research)

The scientific paper: “Evidence for tactile foraging in pterosaurs: a sensitive tip to the beak of Lonchodraco giganteus (Pterosauria, Lonchodectidae) from the Upper Cretaceous of southern England” by David M. Martill, Roy E. Smith, Nicholas Longrich and James Brown published in Cretaceous Research.

A Second Example of Probe Feeding

Recently, Professor David Martill, along with colleagues from Portsmouth University, pterosaur expert Samir Zouhri (Université Hassan II, Casablanca, Morocco) and Nicholas Longrich (University of Bath), published a paper in Cretaceous Research describing a new species of long-jawed pterosaur from Morocco that also could have been a probe feeder.

The flying reptile was described as having exceptionally long jaws for its body size, which terminated in a flattened beak with thickened bony walls.  The shape of these jaws superficially resembled the beaks of probing birds such as kiwis, ibises and curlews.  The research team hypothesised that like these living birds, this pterosaur probed in soft sediments in search of invertebrates.  The age of the fossils is not certain, although an Albian to Cenomanian age was postulated.  This pterosaur was tentatively assigned to the azhdarchoids, but if it is a member of the Azhdarchoidea, then it represents an extremely atypical form.

The scientists conclude that this Moroccan pterosaur adds to the remarkable diversity of the Pterosauria known from the Cretaceous.

Everything Dinosaur acknowledges the assistance of media releases from the University of Portsmouth and the University of Bath in compilation of this article.

The scientific paper: “A long-billed, possible probe-feeding pterosaur (Pterodactyloidea: ?Azhdarchoidea) from the mid-Cretaceous of Morocco, North Africa” by Roy E. Smith, David M. Martill, Alexander Kao, Samir Zouhri, and Nicholas Longrich published in Cretaceous Research.

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Oksoko avarsan – New Species of Oviraptorosaur with Two Fingers

That inappropriately named clade of “Egg Thief Lizards”, the Oviraptorosauria has a new member.  Standing around one metre high at the hips, the newly described Oksoko avarsan (Oak-soak-oh), which had just two digits on each hand, instead of the default Oviraptor setting of three, is helping palaeontologists to understand the radiation and success of these feathered dinosaurs.

A Life Reconstruction of the Newly Described Oksoko avarsan

Picture credit: Michael Skrepnick

The First Evidence of Digit Loss in the Oviraptorosaurs

Over the last forty years or so, lots of new oviraptorosaur theropods have been named and described, principally from fossil finds made in China and Mongolia.   These feathered dinosaurs were highly successful and although their origins are uncertain, this type of dinosaur probably evolved in the Early Cretaceous of northern China and by the Late Cretaceous they had spread across much of Asia and into North America.

Whilst most palaeontologists confronted with the wealth of fossil material would concede that these theropods were geographically widespread, little research has been undertaken to ascertain the reasons for their evolutionary success.  The discovery of Oksoko with its reduced forelimb with only two functional digits suggests that this group could alter their diets, behaviours and habits which enabled them to diversify and multiply.  In essence, variation in forelimb length and hand morphology provides another example of niche partitioning in oviraptorosaurs, which may have contributed to their incredible diversity in the latest Cretaceous of Asia.

The Holotype Block Containing Three Specimens of O. avarsan

Picture credit: Funston et al (Royal Society Open Science)

Gregarious Behaviour in Oviraptorids

Oksoko is known from four specimens, a group of three (see picture above) and a fourth specimen found in the same crouched position that is believed to come from the same location.  All the fossil material was confiscated from poachers so the exact discovery site of these fossils remains unknown.  However, the researchers have confidently assigned them to the Nemegt Formation of the Gobi Desert and the material is estimated to be around 68 million years old.

It had long been suspected that oviraptorosaurs were gregarious social animals.  The finding of three individuals preserved together represents the first, definitive evidence that these animals probably lived in groups and that they were gregarious.  The fossil bones of all four individuals have provided the researchers with an almost complete skeleton of this two-metre-long dinosaur to study.

Key Fossils Representing the Anatomy of Oksoko avarsan

Picture credit: Funston et al (Royal Society Open Science)

Oksoko avarsan – A Three-headed Eagle

The scientists which included Dr Gregory Funston (Edinburgh University) and Phil Currie (University of Alberta), named this dinosaur after the three-headed eagle of Altaic mythology, a reference to the holotype block which contains the skulls of three individuals.  The species or trivial name is from a Mongolian word for “rescued”, it alludes to the fact that these fossils were recovered from poachers.

The remarkably well-preserved fossil material provides the first documented evidence of digit loss in the usually three-fingered Oviraptorosauria.  The holotype block material represents the remains of three dinosaurs that were approximately the same size and bone histology reveals that these animals died when they were around a year old.  The fourth specimen is believed to represent an older animal that died around the age of five.

Commenting on the discovery, Dr Funston remarked:

“Oksoko avarsan is interesting because the skeletons are very complete and the way they were preserved resting together shows that juveniles roamed together in groups.  But more importantly, its two-fingered hand prompted us to look at the way the hand and forelimb changed throughout the evolution of oviraptors — which hadn’t been studied before.  This revealed some unexpected trends that are a key piece in the puzzle of why oviraptors were so diverse before the extinction that killed the dinosaurs.”

Finger Loss in a Dinosaur Family

Oksoko is the sixth genus of the Oviraptoridae family to be named from fossils associated with the Nemegt Formation.  This demonstrates the diversity of these types of dinosaurs in the Late Cretaceous of China.

The other five oviraptorids known from the Nemegt Formation of Mongolia as stated by Everything Dinosaur team members are:

• Rinchenia mongoliensis
• Nomingia gobiensis
• Nemegtomaia barsboldi
• Gobiraptor minutus
• Conchoraptor gracilis

In addition, a number of closely related dinosaurs are known from the Nemegt Formation including the caenagnathid Elmisaurus rarus

The scientists produced a phylogeny of the Oviraptorosauria based in a reduction in size and eventual loss of digit III as shown in the most derived form described to date (O. avarsan) and a corresponding increase in size and robustness of digit I.  They concluded that the arms and hands of these dinosaurs changed radically in conjunction with migrations into new geographical areas and presumably different habitats – specifically to what is now North America and the Gobi Desert.

Plotting the Change in Hand Morphology and the Radiation of the Oviraptorosauria

Picture credit: Funston et al (Royal Society Open Science)

To read a related article that considered the holotype block as evidence for communal roosting in oviraptorids: Three Theropods Preserved in a Resting Pose.

The scientific paper: “A new two-fingered dinosaur sheds light on the radiation of Oviraptorosauria” by Gregory F. Funston, Tsogtbaatar Chinzorig, Khishigjav Tsogtbaatar, Yoshitsugu Kobayashi, Corwin Sullivan and Philip J. Currie published in Royal Society Open Science.

The award-winning Everything Dinosaur website: Everything Dinosaur.

Juravenator and a “Tale” of Sensory Scales

Researchers writing in the academic journal “Current Biology”, have revealed how dinosaurs may have made sense of their surroundings using special sensory nodes embedded in the scales on their skin.  A new paper focusing on the small, theropod Juravenator starki from the Torleite Formation (upper Kimmeridgian), Solnhofen, Bavaria, (Germany), reports on the discovery of dermal structures along the side of the dinosaur’s tail resembling the integumentary sense organs found in extant crocodiles.

Getting a Sense of Dinosaur Senses

Picture credit: Bell et al Current Biology with additional annotation by Everything Dinosaur

Juravenator starki

Once thought to be a close relative of the contemporary Compsognathus longipes, Juravenator is known from a single, beautifully preserved fossil specimen (JME Sch 200), found in a limestone quarry in 1998.  Although squashed flat, the specimen is mostly articulated and complete with only some caudal vertebrae missing.  It is a juvenile and as such, placing it within the Theropoda has proved problematic.  The taxonomic position is uncertain, but it has been suggested that it could represent a basal member of the Coelurosauria or perhaps a primitive member of the Maniraptora.

The genus name is derived from the Bavarian Jura mountains and “venator” – Latin for “hunter”.  The species (trivial) name honours the Stark family who owned the quarry where the sixty-centimetre-long dinosaur fossil was discovered.

Soft tissue representing body scales have been identified associated with the lower leg bones and between the 8th and 22nd caudal vertebrae.  Other soft tissue structures have been found probably representing preserved tendons and ligaments.  It is these dermal structures that have been the centre of this new study.

A Life Reconstruction of the Late Jurassic Theropod Juravenator starki

Picture credit: Jake Baardse

Specialised Scales

Scientists are aware that early in the evolution of the first truly terrestrial tetrapods epidermal scales evolved to provide an effective barrier against ultraviolet radiation and to prevent excessive water loss.  This evolutionary development meant that stem reptiles were no longer constrained by having to stay close to freshwater like their amphibian ancestors.  Epidermal scales in extant reptiles are not simple, inert structures but can perform a suite of functions and assist in how the animal senses its environment.

Researchers Dr Phil Bell (University of New England) in Armidale, Australia along with his colleague Dr Christophe Hendrickx, from the Unidad Ejecutora Lillo in San Miguel de Tucumán, (Argentina), both specialists in dinosaur dermatology, identified a unique scale type with distinctive, prominent circular nodes on the preserved integumentary covering on the tail of Juravenator. They interpret these raised nodes as integumentary sense organs, analogous to those found today in living crocodilians.

Dr Bell commented:

“Few people pay much attention to dinosaur skin, because it is assumed that they are just big, scaly reptiles.  But when I looked closely at the scales on the side of the tail, I kept finding these little ring-like features that didn’t make sense; they were certainly unlike other dinosaur scales.”

Integumentary Sense Organs Identified in a Dinosaur

Picture credit: Bell et al Current Biology

The First Direct Evidence of Integumentary Sense Organs

The surprising presence of such structures suggests the tail of Juravenator played a role in how this dinosaur sensed the world around it.  This is the first direct evidence of such structures being present on the skin of a dinosaur.

The shape and the orientation of the teeth, especially those in the upper jaw suggest Juravenator ate fish (piscivore).  During the Late Jurassic, this part of Europe was covered by a warm, tropical, shallow sea with numerous small islands.  This archipelago was home to a number of dinosaurs including the famous “urvogel” Archaeopteryx.  As crocodiles are aquatic predators, the research team speculate that Juravenator may have been an aquatic hunter too.

Alligators have integumentary sense organs on their snout, whereas crocodiles have these special scales all over their body including the tail.  These sensory nodes help these reptiles to detect temperature changes, chemical signals in the water as well as having tactile properties.  Although the entire integumentary covering of Juravenator is unknown, this lithe dinosaur could have submerged its tail to help it detect the movement of prey underwater.

To read an article about the sense of smell in the Dinosauria: Don’t Get Sniffy About Dinosaur Sense of Smell.

The scientific paper: “Crocodile-like sensory scales in a Late Jurassic theropod dinosaur” by Phil R. Bell and Christophe Hendrickx published in Current Biology.

The Everything Dinosaur website: Everything Dinosaur.