The Mother of All Dragons – Megachirella wachtleri

A team of international scientists, including palaeontologists from Bristol University, Midwestern University (Arizona) and the University of Alberta, have identified the world’s oldest lizard fossil, permitting fresh insight into the evolution of extant snakes and lizards (Squamata).  Writing in the journal “Nature”, the researchers, including co-author Dr Massimo Bernardi from MUSE – Science Museum, Italy and University of Bristol’s School of Earth Sciences, built the largest dataset of reptiles ever assembled in order to assess where in the evolutionary tree of the Reptilia a fossil from the Dolomites of Italy should be placed.

The Holotype Specimen of Megachirella wachtleri

The holotype of Megachirella wachtleri.

Picture Credit:  MUSE – Science Museum

Megachirella wachtleri

The fossil, consisting of an articulated partial specimen was discovered in marine sediments in the Dolomites of Italy and named Megachirella wachtleri in 2003.  Although, found in marine sediment, the fossil, which represented the front portion of the animal, showed no adaptations to an aquatic existence.  On the contrary, it had strong legs with claws and although small at around twenty centimetres in length, it was probably a capable climber.  It was concluded that the carcass of this reptile had been washed out to sea following a storm.

An analysis in 2013 concluded that Megachirella wachtleri was a member of the Lepidosauromorpha, a group of diapsid reptiles defined as being closer to Squamata than to the Archosauria.  Lepidosaurs include modern snakes and lizards, many extinct forms of reptile and the Order Rhynchocephalia, once very diverse, but now only represented by the tuatara of New Zealand.  This new research, which drew upon an enormous database of skeletal and molecular information about 129 different types of reptile, revealed that Megachirella had characteristics that are only found in the Squamata.  It was concluded that M. wachtleri was a stem squamate – think of it as being the “the mother of all dragons”.

Co-author Dr Randall Nydam of the Midwestern University in Arizona stated:

“At first I did not think Megachirella was a true lizard, but the empirical evidence uncovered in this study is substantial and can lead to no other conclusion.”

The 240-million-year-old fossil, Megachirella wachtleri, is the most ancient ancestor of all modern lizards and snakes discovered to date.  The study also found that geckoes are the earliest crown group squamates not iguanians as previously thought.

A Life Reconstruction of  Megachirella wachtleri

A life reconstruction of Megachirella wachtleri.

Picture Credit: Davide Bonadonna

The beautiful illustration of M. wachtleri produced by Davide Bonadonna is featured on the front cover of the journal Nature, which provides details of this scientific study.

The research team conclude that the Squamata probably evolved in the Late Permian and therefore, the ancestors of today’s snakes and lizards survived the most devastating mass extinction event known to science – the end Permian extinction.

Tiago Simões, lead author of the scientific paper and a PhD student at the University of Alberta (Canada), explained:

“The specimen is 75 million years older than what we thought were the oldest fossil lizards in the entire world and provides valuable information for understanding the evolution of both living and extinct squamates.”

10,000 Squamate Species

It has been estimated that there are around 10,000 species of lizards and snakes living today, twice as many different species as mammals.  Despite this modern diversity, scientists did not know much about the early stages of their evolution.

Student Tiago Simões added:

“It is extraordinary when you realise you are answering long-standing questions about the origin of one of the largest groups of vertebrates on Earth.”

Co-author of the study, Dr Michael Caldwell from the University of Alberta, explained that fossils represent the only accurate window into the ancient story of life on our planet.  The new understanding about Megachirella and its significance is but a point in deep geological time, it does tell us things about the evolution of lizards that we simply cannot learn from any of the extant species today.

Co-author Dr Massimo Bernardi from MUSE – Science Museum, Italy and University of Bristol’s School of Earth Sciences, commented upon the importance of such fossil specimens, stating:

“This is the story of the re-discovery of a specimen and highlights the importance of preserving naturalistic specimens in well maintained, publicly accessible collections.”

The scientific paper:

“The Origin of Squamates Revealed by a Middle Triassic Lizard from the Italian Alps” by T. Simões, M. Caldwell, M. Tałanda, M. Bernardi, A. Palci, O. Vernygora, F. Bernardini, L. Mancini and R. Nydam published in the journal Nature.

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

Inspiring Ichthyornis – Top of the Pecking Order

As a very young boy, I remember eagerly striving to complete my Brooke Bond “Prehistoric Animals” card collection.  This was a set of fifty cards to collect,  given away free with packets of tea.   One of the cards featured a pair of toothed, prehistoric birds, a large, reddish coloured Hesperornis which was being mobbed by a couple of tern-like birds, this was my first introduction to Ichthyornis.  Perhaps, the first time that I realised that birds (at least primitive, toothed birds), lived alongside dinosaurs.  How wonderful to read this week that Ichthyornis, thanks to a pieced together three-dimensional skull, may be providing palaeontologists with fresh insights into avian evolution.  The Hesperornis/Ichthyornis picture card may have been burned into my conscience long ago, but it is refreshing to think that this ancient bird may represent a pivotal moment in the transition from dinosaurs to modern-day birds and its significance has only just come to light.  A team of international scientists have published a paper proposing that Ichthyornis may have had one of the first, true bird-like beaks.

The Brooke Bond Picture Card

Hesperornis catching a fish, with Ichthyornis in close attention.

Picture Credit: Everything Dinosaur/Brooke Bond

Toothy Bird with the Beginnings of a Beak

Writing in the journal “Nature”, researchers report on the analysis of beautifully preserved three-dimensional Ichthyornis (I. dispar) fossil skull that is providing new evidence on the evolution of the avian head and how the skull and beaks of birds evolved from their dinosaurian ancestors.

A Three-Dimensional Image of Ichthyornis Skull Material Indicates the Tip of the Premaxillary Formed the First Beak

A computer generated image showing the life position of the fossil bones in the three-dimensional Ichthyornis skull.

Picture Credit: Yale Office of Public Affairs and Communications

Ichthyornis dispar

Known from fragmentary fossils from Kansas and named back in 1872 by Yale University’s Othniel Charles Marsh, it seems fitting that this new study into one of the first toothed birds described, has been led by scientists from Yale University.  Working in conjunction with colleagues from the University of Kansas, Fort Hays State University, Alabama Museum of Natural History and the McWane Science Centre (Alabama), the team report on new specimens with three-dimensional cranial remains, including one example of a complete skull and two previously overlooked cranial elements that were part of the original Yale specimen examined by Marsh.

Using CT scans and sophisticated computer modelling, individual skull and jaw bones were scanned and reproduced in three-dimensions.  This allowed a complete skull to be constructed revealing new details about the transition from dinosaur skull to a more modern bird skull.

Yale University palaeontologist and lead author of the study Bhart-Anjan Bhullar commented:

“Right under our noses this whole time was an amazing, transitional bird.  It has a modern-looking brain along with a remarkably dinosaurian jaw muscle configuration.”

Ichthyornis is part of the biota of the Western Interior Seaway, a shallow sea that split North America in two during the Late Cretaceous.  It has been regarded as an early version of a tern or gull, but its size is unknown as the few fossils found represent individuals of different sizes, however, it probably had a wingspan of no more than sixty centimetres, making Ichthyornis slightly smaller than today’s Common Tern (Sterna hirundo), a bird which fills the same ecological niche as the Mesozoic Ichthyornis.

Using the Latest Research, a New Reconstruction of Ichthyornis dispar was Produced

A life reconstruction of Ichthyornis.

Picture Credit: Yale Office of Public Affairs and Communications

The Evolution of a Beak

Having built a three-dimensional model of the skull and jaw bones, the researchers were able to note that the premaxillary bone in the upper jaw had become elongated and this, working in conjunction with a keratinous tip on the lower jaw formed the first “proto-beak”.  Ichthyornis dispar shows scientists what the first type of bird beak looked like.  This beak may have evolved as the function of the hands was increasingly limited as they were adapted to form a more effective wing.  The grasping hands of the maniraptoran dinosaurs were no longer able to grasp and manipulate objects so the jaws had to take on an additional function, secondary to their main function – dispatching and consuming prey.

The Beak of Ichthyornis

The beak of Ichthyornis evolving to replace grasping, functional hands and fingers.

Picture Credit: Yale Office of Public Affairs and Communications

Although maniraptoran dinosaurs may not have been able to pronate their hands like us and they lacked an opposable thumb, as forelimbs and hands evolved into wings, so the jaws took over the function of the digits and manus.

Bhart-Anjan Bhullar stated:

“The first beak was a horn-covered pincer tip at the end of the jaw.  The remainder of the jaw was filled with teeth.  At its origin, the beak was a precision grasping mechanism that served as a surrogate hand as the hands transformed into wings.”

The research team conducted its analysis using CT-scan technology, combined with specimens from the Yale Peabody Museum of Natural History; the Sternberg Museum of Natural History in Hays, Kansas, the Alabama Museum of Natural History; the University of Kansas Biodiversity Institute and the Black Hills Institute of Geological Research (South Dakota).

Bird Beaks versus Bird-hipped Dinosaur Beaks

The modern bird beak is a unique organ amongst vertebrates, although notably most derived Ornithischian (bird-hipped) dinosaurs possessed a beak, formed from the unique predentary bone in the lower jaw and a roughened, extension of the premaxilla (or the rostral in the case of Ceratopsians), in the upper jaw, which allowed the attachment of a keratinous tip which in conjunction formed the beak-like structure – believed to be an adaptation to assist with cropping vegetation.

This study of Ichthyornis suggests that the first bird beak was not the long organ seen in modern birds, but a little pincer tip to grasp and manipulate objects.

A Chasmosaurine Ceratopsian with the Roughened Rostral and the Predentary Forming a Plant-cropping Beak

The beak of a horned dinosaur is highlighted.

Picture Credit: Rapid City Journal with additional notation by Everything Dinosaur

Fresh Insight into the Evolution of Extant Bird Skulls

The scientists conclude that their study offers new insights into how modern birds’ skulls formed.  Along with its transitional beak, Ichthyornis dispar had a brain similar to that seen in extant birds but a temporal region of the skull that was reminiscent of a dinosaur.  This suggests that during the evolution of Aves, the brain transformed first, possibly to adapt to a volant (aerial) lifestyle, whilst the remainder of the skull retained the ancestral features associated with the Dinosauria.  Ichthyornis retained a large adductor chamber bounded at the top by substantial bony remnants of the ancestral reptilian upper temporal fenestra (hole in the skull).  This combination of features indicates that important attributes of the avian brain and palate evolved before the reduction of jaw musculature and the full transformation of the beak.

The Beak of Ichthyornis Grasping a Mollusc

An illustration of an Ichthyornis holding a mollusc in its beak.

Picture Credit: Michael Hanson/Bhart-Anjan Bhullar

I may never have completed my Brooke Bond card collection, but at least, thanks to this new Ichthyornis study, our understanding of the evolution of the beak in birds is more complete.