What ever happened to Monoclonius?

In the offices at Everything Dinosaur, we have a large collection of prehistoric animal and dinosaur books, many of them quite rare and out of print.  These have been collected over the years and in our quieter moments it is great to be able to thumb through them and look at the way our knowledge and the way in which dinosaurs are depicted has changed.

One of our favourites is “Dinosaurs and other Prehistoric Reptiles” written by Jane Werner Watson and featuring the wonderful illustrations of Rudolph Zallinger.  Mr Zallinger was commissioned to produce a mural showing the evolution of dinosaurs by the Yale Peabody museum.  His work went on display in 1947 and although our view of these animals has changed dramatically over the last 70 years; his artwork remains stunning.  His highly detailed vistas of the Mesozoic landscape have inspired many to enter this field of science.  They really are quite beautiful.

An Endearing Ceratopsian Image

One endearing image is a ceratopsian called Monoclonius (single horn). It is depicted in the (typical for the time), bent leg posture facing an approaching Gorgosaurus.  However, scientists debate whether or not the name Monoclonius is valid, perhaps remains ascribed to Monoclonius should be re-classified to Centrosaurus.

A Juvenile Centrosaurus – Is the Monoclonius Genus Valid?

A replica of a juvenile Centrosaurus. The validity of the Monoclonius genus continues, the ontogeny of horned dinosaurs complicates the issue.

Complicated Taxonomic History

The taxonomic history of these two genera have been mingled together for nearly 100 years.  In many situations, it is the lack of fossil evidence that cause problems for palaeontologists, however, with this particular group of Ceratopsidae the opposite is true.  There is so much material to study that the case for acknowledging Monoclonius as a separate genus becomes blurred.  Extensive Centrosaurinae bonebeds are known from the Dinosaur Park Formation (and other geological formations) of Alberta, Canada.

These sites have provided vast amounts of material, including complete specimens, as well as articulated remains and many skulls.  Dodson provided the first review of the status of these two taxons in 1990 Dodson, P. “On the status of the ceratopsids Monoclonius and Centrosaurus”.  He concluded that Centrosaurus and Monoclonius were sufficiently different from each other to be classified as separate genera.  However, in 1997 Sampson and Tanke assisted by Michael Ryan reviewed this material, focusing their studies on the ontogenetic evidence from the Alberta bonebeds.

The bonebeds provide fossils of Centrosaurines of different ages, from young individuals to mature adults.  This study built on the earlier work of Charles Sternberg and his report on the horned dinosaurs of Alberta that had been published in 1940.  Sampson et al concluded that fossils that had previously been described as Monoclonius (M. crassus); showed evidence of belonging to immature individuals lacking adult characteristics.  Based on this evidence the 1997 team declared Monoclonius a “nomen dubium”.  Nomen dubium is a term used to describe an animal or plant whose validity is in doubt.  Effectively, the fossils of Monoclonius were classified as belonging to young, sub-adult Centrosaurus.

Missing Monoclonius

The term Monoclonius continues to be used by dinosaur enthusiasts and some professional palaeontologists.  The name was first used by Sir Edward Drinker Cope, the eminent American palaeontologist who named and described the first Monoclonius (M. crassus) in 1876.  Thanks to the inclusion of the Monoclonius illustration by the likes of Rudolph Zallinger in many books, the name has seeped into popular culture and is perhaps better known than Centrosaurus.

The story of Monoclonius is far from over, a lot of indeterminate cceratopsian material from Canada and the USA is still referred to as belonging to Monoclonius.  The largest skull of any centrosaurine yet found (CMN 8790), part of the Canadian Museum of Nature collection has been classified as Monoclonius lowei and as such might represent a valid specimen of Monoclonius.

As centrosaurines matured so their cranial ornamentation changed.  Mature centrosaurs such as Centrosaurus apertus saw changes in the shape and size of their frill epoccipitals (the lumps and bumps of bone that were found on the edges of their neck frills).  The first pair of epoccipitals became enlarged as the animal aged and formed hooks that curved over the opening in the skull (parietal fenestra).  They resembled small bent horns, a feature picked up by Zallinger and included in his 1947 illustration of Monoclonius.

Beasts of the Mesozoic Models and Figures

The popular Beasts of the Mesozoic model series features several replicas of horned dinosaurs including centrosaurines.  To view this range: Beasts of the Mesozoic Models and Figures.

Raised crests on the Nasals make Neovenator a very peculiar looking Theropod

Sunday and we are back in the office working on some new fact sheets in preparation for the launch of the new Procon/Collecta range of dinosaur models.  We first saw the prototypes of this new set of six prehistoric animals about 12 months ago.  The team at Everything Dinosaur had been asked to examine them and make suggestions regarding anatomical accuracy, also to comment on the choice of dinosaurs that were going to make up the series.  The six dinosaurs featured are Spinosaurus (seems every manufacturer wants to come up with one of these), Eustreptospondylus, Augustinia, Baryonyx, Allosaurus and Neovenator.  As a British based company, it is very rewarding to see UK dinosaurs featured in the new collection, especially ones such as Eustreptospondylus and Neovenator which are known from only one major fossil find, plus a few scattered bones.

Neovenator Illustration

We have been working with an accomplished and very well respected American illustrator called Mike Fredericks.  He has been providing us with sketches of the new models that we can use to produce scale drawings in our fact sheets.  We find it is all very well saying that Neovenator could be up to 7 metres long and 2 metres tall, this does not mean much to some of our younger dinosaur fans but if you put a scale model of their dad in the drawing then the impressive size of some of these animals is made much clearer.

Interesting to note that the actual size of Neovenator salerii is still debated, despite it being 30 years since the only relatively complete skeleton of this animal was discovered.  The 50% complete specimen (MIWG.6348), which began to be excavated in 1980, two years after its discovery on the Isle of Wight, indicates an animal about 7 metres long.  However, an isolated pedal phalanx (toe bone), also from the Isle of Wight (MIWG.4199) and attributed to Neovenator may indicate that this allosaur reached lengths in excess of 10 metres.

A Sketch of Neovenator – With the Muzzle like Face

Picture courtesy of Mike Fredericks

Neovenator has been classified as an allosaurid and is the largest allosaur discovered so far in Europe.  The end of Neovenator’s ischium has an “expanded boot”, this feature is seen in a particular group of allosaurs called the carcharodontosaurids, although other features of the fossil remains enable Neovenator to be classified into its own genus.  If Neovenator is classified as a close relative of carcharodontosaurids it implies that this particular group of meat-eating dinosaurs originated in Europe before spreading into Africa (Carcharodontosaurus), South America (Giganotosaurus) and North America (Acrocanthosaurus).  The carcharodontosaurids may turn out to comprise the largest meat-eaters the world has ever known (not withstanding the latest information on the huge tyrannosaur skull unearthed in the US by Kevin Rigby).  So Europe might be the birthplace of the really big theropods and not Asia or the Americas as previously thought.

Neovenator

Neovenator was a bizarre looking carnivore.  The main elements of the skull and jaws recovered from the Isle of Wight consist of the left premaxilla and left maxilla.  These bones made up what was the snout of the animal and they indicate that it had a broad muzzle with raised nasal crests.  In life these features would have given the impression that Neovenator had a broad beak.  Why did Neovenator have these unusual features?

A number of suggestions have been put forward, this large hunter may have used its beak to knock down prey that it was pursuing.  It could have butted them with its head and knocked them off balance, this may have been a successful hunting strategy of young Iguanodontids as they ran away on their hind legs.

The muzzle could also have been used for display purposes.  Scientists have speculated whether these large Theropods lived in packs and the nasal crests could have been an ontogenetic feature (changes with age), with only one specimen found so far this is a difficult theory to prove. The muzzle shape in combination with any colour changes that occurred as the animal reached maturity could indicate social standing in the pack.

From the size of the naris (which is very large), it seems that sense of smell was very important to Neovenator, perhaps the muzzle shaped evolved to permit extended nasal passages giving this animal an improved sense of smell.  If more material is discovered then palaeontologists may be able to shed more light onto this mystery.

Ironically, there may be fossils of Neovenator already in museums, especially the Natural History museum – London.  For many years isolated fragments and individual theropod bones had been ascribed to the Megalosauridae group.  Indeed, some palaeontologists claim that this taxon has become a “dumping ground” for any miscellaneous meat-eating dinosaur fossils.  So there may be more Neovenator remains already in museum draws, these may provide more information on the size of the animal plus shed more light on the structure of the skull.

Neovenator Models and Figures

Everything Dinosaur stocks a variety of theropod models and figures including replicas of Neovenator.

View the CollectA Prehistoric Life model range: CollectA Prehistoric Life Model Range.

CollectA Deluxe: CollectA Deluxe Prehistoric World Models.