Nichollssaura borealis – Shaking its Neck from Side to Side

The long-necked plesiosaurs (Plesiosauroidea), are characterised (unsurprisingly), by their long necks, which in the case of the elasmosaurids were taken to extremes with some Late Cretaceous species having necks around seven metres in length, comprising 76 cervical vertebrae, but how did a plesiosaur use their necks?  What degree of movement did these long necks have?  These are questions that have been debated by palaeontologists for nearly two hundred years.

New research, published this week by the Royal Society, sheds light on the flexibility and neck movement in one plesiosaur, the Early Cretaceous leptocleidid Nichollssaura borealis.

The Fossilised Skeleton of a Jurassic Plesiosaur

Picture credit: Everything Dinosaur

Defining the Plesiosauria Clade

The Plesiosauria clade was very successful, originating in the Triassic and persisting until the very end of the Cretaceous.  This clade is split into three distinct groups, although palaeontologists debate the phylogeny between the Plesiosauria clade members.

1. The Plesiosauroidea – the long-necked marine reptiles, epitomised by short tails, broad bodies, four flippers, a small head and an elongated neck.
2. Pliosauridae – the short-necked plesiosaurs, with large heads, broad bodies, four flippers and much shorter necks than the Plesiosauroidea.
3. The Rhomaleosauridae – a sort of half-way house between the other two, typically possessing longer necks and smaller heads relative to the Pliosauridae, but have shorter necks and larger heads when compared to members of the Plesiosauridae.  Most known rhomaleosaurids are confined to the Early to Middle Jurassic of Europe, with most specimens assigned to this group having been found in England.

The Three Groups Within the Plesiosauria

Picture credit: Everything Dinosaur

For models and replicas of marine reptiles: CollectA Deluxe Prehistoric Life.

Studying One Member of the Plesiosauroidea – Nichollssaura borealis

The researchers from the Royal Tyrrell Museum and the University of Calgary, focused their study upon one specimen, a member of the Plesiosauroidea called Nichollssaura borealis.  This specimen was chosen as it represents a very nearly complete individual and the fossil is not distorted or crushed to any degree which might have comprised any research into neck flexibility.

There were two further, more practical reasons why N. borealis was selected.  Firstly, the specimen is housed at the Royal Tyrrell Museum and since one of the researchers involved in the study was Donald Henderson, a curator at the museum, accessing the specimen was not a problem.  In addition, with a total length of 2.6 metres Nichollssaura could squeeze into the medical CT scanner that was being used to create accurate three-dimensional images of the bones.

Once the specimen had been CT scanned, the subsequent three-dimensional models that were produced could be examined so as to conclude the range of movement afforded by the 24 bones in the neck of this plesiosaur (24 cervical vertebrae).

The Research Team Tested the Range of Neck Movement Using Three-Dimensional Models

Picture credit: Royal Society Open Science

Sideways Movement of the Neck

When the three dimensional models of the Nichollssaura borealis neck were examined the scientists discovered that the neck of this plesiosaur was indeed very mobile, but their results suggest a preference for lateral (sideways) movements of the neck in this species.  This supports the idea that these marine reptiles fed in or along the seafloor, using their small heads and long necks to probe into the sediment to find invertebrates and fish.

Unfortunately, no gut contents indicating potential prey have been preserved in association with the single fossil specimen of Nichollssaura, however, other researchers have found prey gut contents in other plesiosaurids that supports the idea that these animals fed by disturbing and catching animals that live on the sea floor (epifaunal).

To test the validity of the three-dimensional computer models, the scientists studied the range of neck movement in a extant species of monitor lizard, Dumeril’s monitor, a species from south-east Asia (Varanus dumerilii).  This species was chosen as it has a relatively long neck for a monitor lizard and a preserved specimen was available for study.

The researchers conclude that if this species of plesiosaurid (N. borealis) had a neck that was adapted to rapid sideways movements then this probably evolved in relation to feeding method and prey capture.  Different types of Plesiosauroidea with their different neck lengths very likely had different ecological roles within the ecosystem.  This study also demonstrates that three-dimensional modelling is an effective tool for assessing function morphology for structures where no good, living analogue for comparison exists.

Visit the Everything Dinosaur website: Everything Dinosaur.

Sauropod Trackways Discovered in Dorset

Scientists have been measuring and mapping a set of dinosaur tracks found in a quarry in Dorset.  The saucer-shaped tracks were made by a herd of long-necked sauropod dinosaurs that crossed a stretch of a tidal lagoon back in the Early Cretaceous.  The quarry is located close to the village of Worth Matravers, around three-and-a half-miles east of the coastal town of Swanage, on the Isle of Purbeck.

A View (Dorsal) of a Dinosaur Footprint (Sauropoda)

Picture credit: Bournemouth University

Giant Dinosaur Tracks

The group of large dinosaurs were walking slowly in a herd, leaving a series of parallel trackways.  They have been described as “giant saucer-shaped depressions just a few millimetres deep”, according to geologist Matthew Bennett from Bournemouth University who has been called in to study and map the fossilised tracks.

The quarry is the property of Lewis Quarries, one of a number in the area that provide valuable limestone blocks for the construction industry.

An Aerial View of the Dinosaur Tracks

Picture credit: Bournemouth University

Early Cretaceous Dinosaur Tracks

The footprints were made between 139 and 145 million years ago (Early Cretaceous), the tracks were infilled by lime rich muds, creating trace fossils.

David Moodie, a spokesperson for Lewis Quarries explained:

“It became apparent that we had come across something of historical interest, so working closely with the National Trust and Professor Matthew Bennett of Bournemouth University, we were able to move forward in the best way without stopping progress in the quarry itself.”

National Trust Lead Ranger Jonathan Kershaw added:

“The group of dinosaurs that made these tracks may be the same ones whose footprints can still be seen in situ just nearby at Keates Quarry just off the Priest’s Way bridleway.  It’s exciting to think that giant sauropods once roamed where today there are dry stone walls, skylarks and nesting seabirds.”

An Illustration of the Sauropods Crossing the Shallow Lagoon

Picture credit: Bournemouth University

In 2015, Everything Dinosaur reported on the discovery of a series of sauropod footprints and tracks on the Isle of Skye.  These tracks were made in similar circumstances as the Purbeck limestone prints, a group of sauropods crossed a shallow lagoon, however, the Isle of Skye prints are around thirty million years older and date from the Middle Jurassic.

To read more about the sauropod prints from the Isle of Skye: Isle of Skye Sauropods and their Watery World.

DigTrace Maps the Fossil Footprints

Using a process of photogrammetry and special freeware developed at Bournemouth University called DigTrace, Professor Bennett carefully documented the tracks in three dimensions.  The DigTrace technology was developed with a government grant and help from the Home Office and National Crime Agency.  Its principle aim is to forensically examine footprints and other tracks related to crime scenes, however, it is ideal for plotting the movements of extinct dinosaurs too.

Professor Bennett commented:

“This technology is now being used by the police to help track criminals via their footprints, but we can also use it to record and preserve rare footprints like these.  The beauty of capturing the tracks in 3D is that they can be analysed digitally and even printed in the future, no need to hold up the quarrying for long.”

Drawing Up a Conservation Plan for the Dinosaur Tracks

With the co-operation of Lewis Quarries and in collaboration with the National Trust and researchers at Bournemouth University, a conservation plan is being prepared.  It is hoped that the tracks will be lifted from their setting and put on public display once all the appropriate scientific steps (pardon the pun), have been taken.

The trackway surface is also exposed in nearby Keates Quarry where the National Trust maintains a small conservation area of similar tracks.

Professor Bennett concluded:

“What is remarkable, is that the tracks at both adjacent quarries were probably made by the same animals moving along the coast.  The dip of the beds, folded when the European Alps were pushed up, means that the tracks are closer to the ground in Keates Quarry and can be preserved but are much deeper at Lewis Quarries where in situ preservation is not possible.”

The Dig Site at the Dorset Quarry

Picture credit: Bournemouth University

Everything Dinosaur acknowledges the assistance of the media centre at Bournemouth University for the compilation of this article.

Visit the Everything Dinosaur website: Everything Dinosaur.