Baby Faced Dinosaurs

Those animators at Disney who draw cartoon dinosaurs for various films and animated features with cute looking, large eyes may have been nearer the truth than they thought.  A new study comparing the skull of a juvenile Diplodocus to those of adult animals suggests that the babies had different shaped heads than those of their parents.  The American scientists who carried out the research, conclude that as the animals grew, their skulls changed dramatically, possibly indicating that young animals did not feed in the same way or on the same food as mature Diplodocids.

Juveniles possessing differently proportioned features to adults is a relatively common trait, particularly in higher animals such as mammals.  However, very little is known about how the skulls and faces of Sauropod dinosaurs changed as these animals grew and matured, unfortunately Sauropod skull material (whether adult or baby) is extremely rare in the fossil record.

Sauropods, were the giant, long-necked dinosaurs.  Some of these creatures were the largest animals ever to roam the Earth.  Unfortunately, despite many very famous dinosaurs belonging to this sub-order of Dinosauria, animals such as Brachiosaurus, Apatosaurus and Diplodocus itself; very little is known about the skulls of these animals.  When a Sauropod died, as the carcase rotted, the proportionately small head often fell off the neck and was lost, particularly if the carcase was transported any distance, as in being carried away by a flash flood or some other such natural occurrence.  Fossils of baby and juvenile Sauropods in particular are exceptionally rare in the fossil record.  Any such carcase, if not buried quickly would soon have been torn apart by many scavengers.

Diplodocus is perhaps one of the best known of all the dinosaurs.  Several species have been ascribed to this genus.  It is one of the longest type of Sauropods known, with some species believed to have attained lengths in excess of 30 metres.  The first Diplodocus bones were found in Colorado (western USA) by a famous American fossil hunter, Samuel Williston.  Although, far from complete it was clear that these large bones represented a new type of long-necked dinosaur.  Othniel Marsh formerly named and described Diplodocus in 1878.

An Illustration of Diplodocus

Picture Credit: Everything Dinosaur

To view a model of Diplodocus: Dinosaur Models for Girls and Boys

However, new research on the skull of a juvenile Diplodocus suggests that these dinosaurs had proportionally larger eyes and smaller faces when they were youngsters.

Young Diplodocids had Smaller, more Pointed Faces than Adult Diplodocids

Ontogeny in Diplodocids

Picture Credit: Mark A Klinger/ Carnegie Museum of Natural History

Jeffrey Wilson, assistant professor at the University of Michigan’s Geological Sciences department, along with palaeontologist colleague John Whitlock and Matthew Lamanna from the Carnegie Museum of Natural History (Pittsburgh, USA) have published their study of Diplodocid skulls in the scientific publication “The Journal of Vertebrate Palaeontology”.  The team conclude that young Diplodocids had radically different shaped skulls when compared to mature animals of the same species.

The discovery of the very well preserved skull of a juvenile Diplodocus in the Carnegie Museum’s storage vaults was the catalyst for this new research work.  It is not uncommon for rare and precious fossils to be “re-discovered” in the back office draws and storage rooms of a museum.  Often specimens from past excavations could have been wrongly described or labelled, or an artefact could simply have been lost as vast collections were catalogued.

Indeed, every now and then a brand new species is discovered after a re-examination of a long kept piece of fossil bone.  This is exactly what happened at the Natural History Museum in London, when a PhD student discovered a new species of Sauropod, by looking again at some fossils that had been held in the collection for many years.

To read more about this discovery: If you want to find a new dinosaur – try looking in the museum’s vaults

Up until recently, very little was known about the shape and facial proportions of Diplodocid skulls, however, the discovery of some very well preserved adult skull material has enabled scientists to piece together (literally), a picture of the facial features of these huge animals.  Scientists now know that the snout of Diplodocus was quite long and the jaws were square shaped and relatively broad.  It had been assumed that young Diplodocids had the same sort of faces, but that has changed in the light of the new data.

Assistant professor Wilson commenting on the broad, square jaws of an adult Diplodocus:

“Up until now, we assumed juveniles did too.”

Instead, this new research shows that the juvenile’s skull was shaped very differently from an adults.  The snout was much more pointed, the eyes larger in proportion to the rest of the face and the jaws were much less square.

When asked to explain the significance of the discovery of the skull of the juvenile Diplodocus, John Whitlock stated:

“Although this skull is plainly that of a juvenile Diplodocus, in many ways it is quite different from those of the adults.  What was unexpected was the shape of the snout – it appears to have been quite pointed, rather than square like the adults.”

This new research indicates that young Diplodocids were “baby faced” and suggest that as the animal grew and matured major changes would have occurred in the skull morphology.

The American researchers believe that the changes in skull shape might have been tied to feeding behaviour, with adults and juveniles eating different foods to avoid competition.  In the ground-breaking television documentary series “Walking with Dinosaurs”, one of the episodes (Time of the Titans), portrayed the life of a Diplodocus based on the then current scientific thinking.

It is thought that large Sauropods, laid nests of eggs close to the edge of forests and other areas of extensive cover.  These were no more than scrapes in the ground with the eggs carefully covered over again and then like most lizards, snakes and chelonians the nest was simply abandoned to its fate.  Hatch-lings, already up to 80cm long would then emerge together, perhaps under the cover of darkness and scurry off into the forests finding cover amongst the ferns and small plants of the forest floor.

This new paper, supports the storyline depicted in the television programme, the young animals would have lived in a forest environment feeding on a different range of plants, whilst adult and larger offspring could wander the fern plains in herds.  The narrower jaws of the young Diplodocus may also indicate that it was a fussier eater, perhaps selecting only the youngest, most nutritious leaves as their stomachs and digestive systems could not cope with the coarser plant material consumed by adults.

Studying how dinosaurs grew and changed as they got older has yielded many surprising facts about these amazing animals.  Recently, a number of research teams have studied the ontogeny (growth) of several dinosaur species, including members of the Diplodocidae.

To read more about the ontogeny of Dinosauria: The Joys of Working with Baby Dinosaurs

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