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.

Baby Dinosaurs

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 models of Diplodocus and other sauropod dinosaurs, take a look at the huge range of models in the CollectA series: CollectA Age of Dinosaurs Prehistoric Life.

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.

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 dauropod, 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.

Large Sauropods Breeding Strategies

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 80 cm 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.

Leedsichthys – Getting Shrunk Down to Size

There seems to be a trend in palaeontology, perhaps it is the public’s obsession with the fastest, the fiercest, the biggest and such like, but over the years a number of extinct genera have been subjected to a shrinking effect once more is known about them.  Liopleurodon for example, portrayed by the BBC as the largest carnivore of all time, weighing a colossal 150 Tonnes, an exaggeration given the fossil evidence.  Now even a gentle filter feeder such as Leedsichthys (Leedsichthys problematicus) has been subjected to a shrinking ray.

For models of sea monsters including prehistoric fish replicas: Models of Sea Monsters.

Leedsichthys

Leedsichthys was a member of the Pachycormidae, a group of ray-finned fishes.  The first fossils of this Jurassic fish were discovered in the mid 1880’s near Peterborough (Cambridgeshire, England), although something like seventy fossils of this marine giant are known, they are all very incomplete and fragmentary.  The best evidence for claiming this fish to be the largest ever comes from reconstructions as scientists try to piece together what remains of the fish they do have.  As the skeleton of Leedsichthys was made of cartilage and not bone, it is very difficult to piece together what fragments scientists do have.  However, thanks in part to a chance discovery of a reasonable number of Leedsichthys fossils found in a cupboard in a Glasgow museum, lengths of up to 27 metres have been ascribed.

Is Leedsichthys the largest fish that ever lived?  To read more about this ancient creature, a marine giant from the Age of Reptiles: Leedsichthys – The Largest Fish Ever?

Formerly described by many scientists as “Blue Whale sized”, the problem occurs as scientists attempt to scale up Leedsichthys by comparing what elements of the skeleton are known with more complete but much smaller Pachycormidae specimens.  Based on simple comparisons some researchers have concluded that certain individuals, perhaps females; could reach sizes in excess of 35 metres, however, recent research has indicated that Leedsichthys was probably nearer to 35 feet long than 35 metres, with one or two exceptional individuals reaching lengths of 55 feet or more.  This would put this extinct animal in the size bracket of the extant Whale Shark (Rhincodon typus), largest living fish on the planet.

More Prehistoric Filter Feeding Fish

Recently, the discovery of more fossils of filter feeding fish has enabled scientists to “plug” an evolutionary gap in ancient eco-systems, as up until recently, there was very little fossil evidence to indicate the presence of large plankton feeding vertebrates between the time of Leedsichthys and the evolution of modern fishes and baleen whales to fill this ecological niche.

To read an article about this: Evidence of a “Leedsichthys Legacy” – Fossil Discovery fills 100 million year old Gap.