CT Scanner Helps Palaeontologists to Map the Braincase of a Marine Reptile

A farmer’s field in Warwickshire was the site of a remarkable fossil discovery more than sixty years ago.  Thanks to the application of advanced medical science and computer modelling, a team of researchers including scientists from Manchester University, have been able to unlock secrets from inside the skull of a giant, Early Jurassic marine reptile.  The almost 200 million-year-old fossil, was found at Fell Mill Farm (Warwickshire, England), in 1955.  The material included a nearly one-metre-long skull of an ichthyosaur, it had been preserved in three-dimensions permitting scientists a rare glimpse into the internal workings of a prehistoric animal’s skull.

The Beautifully Preserved and Now Fully Restored Skull Specimen

Picture credit: Thinktank, Birmingham Science Museum

Revealing New Information About a Rarely Preserved Marine Reptile Braincase

Most ichthyosaur cranial material is crushed, flattened and distorted during the fossilisation process.  This specimen permitted the research team which included Dean Lomax (Manchester University), skilled fossil preparator Nigel Larkin and Laura Porro (University College London), to study a near complete and undistorted three-dimensional skull providing new insights into ichthyosaur cranial anatomy and the morphology of the braincase.  Despite the fossil specimen’s excellent preservation, it had never been formally studied prior to this research.

Co-author of the paper, Nigel Larkin explained:

“Initially, the aim of the project was to clean and conserve the skull and partially dismantle it to rebuild it more accurately, ready for redisplay at the Thinktank Museum [Birmingham].  But we soon realised that the individual bones of the skull were exceptionally well preserved in three dimensions, better than in any other ichthyosaur skull we’d seen.  Furthermore, that they would respond well to CT scanning, enabling us to capture their shape digitally and to see their internal details.  This presented an opportunity that couldn’t be missed.”

Computed Tomography (CT) Scans

To help unlock the information contained inside the skull, the specimen was subjected to computed tomography (CT) scans using a large medical scanner located at the Royal Veterinary College (London).  The powerful X-rays in conjunction with computer modelling allowed a three-dimensional and highly accurate digital reconstruction of the fossil to be made.  This is the first time a digital reconstruction of a skull and mandible of a large marine reptile has ever been made available for research purposes and to the public.

Going Through the CT Scanner

Picture credit: Nigel Larkin photograph taken at Royal Veterinary College, London

Further computed tomography analysis (micro-CT scanning) took place at the University of Cambridge.

Study Clears Up Marine Reptile Fossil Identification

When originally labelled several decades ago, the ichthyosaur was classified as an example of the species Ichthyosaurus communis.  Indeed, when Everything Dinosaur wrote an article about this remarkably well-preserved skull back in 2016, the specimen was still being described as Ichthyosaurus.  However, lead-author and ichthyosaur expert, Dean Lomax became convinced as the research progressed, that this specimen represented a much rarer species.  He identified it as an example of an ichthyosaur called Protoichthyosaurus prostaxalis, the type species of this genus had originally been named in 1979.

To read the 2016 article that describes the skull and shows the post cranial material associated with this specimen: One of Britain’s Largest Ichthyosaurs Goes on Display.

With a skull almost twice as long as any other specimen of Protoichthyosaurus, this is the largest specimen known to science.

Research Team Members View the Results of the CT Scans

Picture credit:  Nigel Larkin, taken at the University of Cambridge

Lead-author Dean Lomax stated:

“The first time I saw this specimen I was puzzled by its excellent preservation.  Ichthyosaurs of this age (Early Jurassic), are usually ‘pancaked’, meaning that they are squished so that the original structure of the skull is either not preserved or is distorted or damaged.  So, to have a skull and portions of the skeleton of an ichthyosaur of this age preserved in three dimensions, and without any surrounding rock obscuring it, is something quite special.”

Protoichthyosaurus prostaxalis

Protoichthyosaurus was first erected by the British palaeontologist Robert Appleby forty years ago.  Prior to his research, the fossil material that Dr Appleby assigned to the new genus had been placed in the Ichthyosaurus genus.  Indeed, subsequent research challenged this assessment and for some time, the validity of the Protoichthyosaurus genus remained in doubt.

In 2017, Dean Lomax along with colleagues Professor Judy Massare (State University of New York) and Rashmi Mistry (Reading University), conducted a re-examination of the fossil material and carried out extensive comparisons between ichthyosaur and suspected Protoichthyosaurus specimens.  The researchers concluded that Protoichthyosaurus was indeed, a valid genus: Reaffirming Protoichthyosaurus as a Valid Genus.

A Life Reconstruction of the Ichthyosaur Protoichthyosaurus prostaxalis

Picture credit: Bob Nicholls @Paleocreations

Back to the Braincase

The skull is not quite complete, but several bones that make up the braincase, which are very rarely preserved in the Ichthyosauridae, are present.  The micro-CT scanning conducted at Cambridge University provided crucial data to help reconstruct the internal anatomy of the animal’s skull and brain.  The fossil only preserved bones from the left side of the braincase, however, using CT scans these elements were digitally mirrored and 3-D printed at life size to provide a complete braincase.

Commenting on how the use of modern technologies, such as medical scanners, have revolutionised the way in which palaeontologists are able to study and describe fossils, Dr Laura Porro stated:

“CT scanning allows us to look inside fossils – in this case, we could see long canals within the skull bones that originally contained blood vessels and nerves.  Scans also revealed the curation history of the specimen since its discovery in the ‘50s.  There were several areas reconstructed in plaster and clay, and one bone was so expertly modelled that only the scans revealed part of it was a fake.  Finally, there is the potential to digitally reconstruct the skull in 3-D.  This is hard (and risky) to do with the original, fragile and very heavy fossil bones; plus, we can now make the 3-D reconstruction freely available to other scientists and for education.”

An Image of the Three-Dimensional Scan of the Protoichthyosaurus Skull Material

Picture credit: University of Manchester/Thinktank

Dean Lomax added:

“It’s taken more than half a century for this ichthyosaur to be studied and described, but it has been worth the wait.  Not only has our study revealed exciting information about the internal anatomy of the skull of this animal, but our findings will aid other palaeontologists in exploring its evolutionary relationship with other ichthyosaurs.”

Visit the Everything Dinosaur website: Everything Dinosaur.

A New Tiny Dromaeosaurid Ichnogenus Dromaeosauriformipes

Catching up with our reading of scientific papers over the weekend and our attention was caught by the description of tiny, two-toed prints from South Korea that reaffirm the growing conviction amongst scientists that some types of non-avian dinosaur were very small, not much bigger than sparrows. The footprints might be the smallest dinosaur tracks discovered to date.

Writing in the academic journal “Scientific Reports”, researchers from South Korea, in collaboration with colleagues from Australia, China, Spain and the USA, describe eighteen diminutive, didactyl tracks that are attributed to either juveniles or tiny adult dinosaurs that may have had a hip height of around five centimetres.

Dinosaur Tracks

The tracks have been ascribed to a new ichnogenus – Dromaeosauriformipes (D. rarus), the name translates as similar in form to Dromaeosauripus*, small and rare.

A Life Reconstruction of the Recently Described Dromaeosauriformipes rarus

Picture credit: Anthony Romilio (Queensland University)

Dromaeosauripus* is an earlier described ichnogenus representing a larger set of tracks, three ichnospecies have been assigned to this ichnogenus to date.

Dromaeosauriformipes rarus – A Microsaur

The tracks were originally found by Professor Kyung Soo Kim (Chinju National University of Education, South Korea), one of the authors of the paper.  The tracks come from a series of remarkable multiple track-bearing horizons from the JinJu Formation of the south-eastern part of the Korean peninsula.  The deposits represent lakeshore sediments (Lower Cretaceous) and date from approximately 115 million years ago (Aptian faunal stage).

The trackways criss-cross an area that was once soft mud and the eighteen tracks are interpreted as representing an estimated 6 to 10 individual trackways possibly made by a similar number of different individuals.  It is suggested that the prints could resemble a Microraptor-like dromaeosaurid (microraptorine).  Some scientists have suggested that Microraptor was piscivorous (fish-eating).  The tracks found in association with a lakeshore, could represent a Microraptor-like dinosaur searching for food, but equally the tracks could represent other types of activity.

Microraptorine Activity in Lakeshore Setting (D. rarus)

Picture credit: Scientific Reports  – original photo (A) by Professor Kim

The picture shows (A), the seven print trackway of the diminutive dromaeosaurian Dromaeosauriformipes rarus.  A line drawing of the trackway is shown (B) and (C) shows a line drawing of the track-bearing surface showing two tiny tracks but trackway 2 has a much bigger stride length indicating greater velocity than recorded in trackway 1.  Pictured below are seven photographs recording the individual prints.

One of the authors of the scientific paper, Dr Anthony Romilio from the University of Queensland stated:

“They are the world’s smallest dinosaur tracks.  These new tracks are just one centimetre in length, which means the dinosaur that made them was an animal you could have easily held in your hand.”

Hatched from Tiny Eggs

To estimate the size of the dinosaur that made the tracks, the team measured the footprint length and multiplied the value by 4.5 to get an approximate hip height.  The maker(s) of these tiny tracks would have had a hip height of around five centimetres.  The two-toed prints are definitively dromaeosaurid, as the second toe, the killing claw, is held off the ground as the dinosaur moves about, hence just two toe impressions are left behind in each print.  In the paper, the scientists comment upon the fact that these tiny dinosaurs must have hatched from very small eggs.

Back in 2016, Everything Dinosaur featured the discovery of tiny three-toed theropod prints that had been discovered in Lower Cretaceous sediments from south-western China.  As a result, a new “tiny-saurus” ichnogenus was erected – Minisauripus.  The South Korean prints assigned to Dromaeosauriformipes rarus are even smaller.

To read about the earlier discovery of tiny dinosaur footprints from south-western China: Minisauripus – the Smallest Dinosaur Known?

Professor Kyung Soo Kim commented that the lake deposits at this location created ideal conditions that allowed for the preservation of tiny footprints, rarely found anywhere else in the world.

Professor Kim added:

“In addition to tiny dinosaur tracks, we have footprints made by birds, pterosaurs, lizards, turtles, mammals, and even frogs.”

Comparing the Tracks of Dromaeosauriformipes rarus with Dromaeosauripus jinjuensis

Picture credit: Scientific Reports

The image above compares illustrations of the tracks of  Dromaeosauriformipes rarus to the size of the trackways assigned to Dromaeosauripus jinjuensis.  Note the raised second toe which produces the characteristic two-toed print.  D rarus tracks suggest a much smaller dromaeosaur produced the tracks.  The image in the upper left is a colour photogrammetric image of Trackway 1 which helps to define track depth and characteristics.  This is compared to the photogrammetric colour image showing the type trackway of D. jinjuensis (right).

Are These Tiny Dinosaurs or Newly-Hatched Dinosaurs from a Much Larger Species?

The tracks support the idea that there may have been lots of very small dinosaurs, but their small bones would not necessarily be preserved in the fossil record so there may be a bias towards larger members of the Dinosauria due to their greater preservation potential.  However, if conditions are right, then diminutive prints and tracks can be preserved, providing tantalising evidence to support the idea of a much more diverse Theropoda then previously thought.  The researchers raise two fascinating questions in their published paper:

1. What is the size range of “raptor” tracks based on footprints or inferred from skeletal remains?
2. How might diminutive tracks of juveniles be distinguished from the prints made by tiny adults (microsaurs)?

Co-author Dr Martin Lockley (University of Colorado Denver’s College of Liberal Arts and Sciences), suggests that these tiny trackways could represent the prints of adult dinosaurs.

He commented:

“Rapidly growing dinosaurs don’t remain small or leave little footprints for very long.  But of all of the footprints we’ve found of the Minisauripus, none grew larger than one inch; a preponderance of evidence of a small species and not babies.  There’s a chance that we just found something smaller.”

For models and replicas of “raptors” and other prehistoric animals: Beasts of the Mesozoic Models and Figures.