Skip to main content

The taxonomic status of Megalosaurus bucklandii

A new paper by Roger Benson of Cambridge University and colleagues discuss the taxonomic status of Megalosaurus bucklandii.

Every dinosaur fan knows of Megalosaurus, the first dinosaur to be named by William Buckland in 1824. Megalosaurus is also historically significant as being one of the taxa that Richard Owen based his Dinosauria in 1842, the other taxon obviously being Iguanodon. The type species M. bucklandii was erected by Gideon Mantell in 1827. Buckland's original description of Megalosaurus in 1824 is based on a series of syntypes, one of which is the famous dentary (fig). Over the years, many other large theropod specimens from the Middle Jurassic were "unjustifiably (Benson et al. 2008)" attributed to M. bucklandii. Over the years, many authors noted the possibility that the syntype series and all subsequent referred specimens may belong to different taxa all together. Thus M. bucklandii is suggested to only refer to the lectotype dentary.

According to Benson et al. (2008) the lectotype dentary allows for a diagnosis of M. bucklandii thus making it a valid taxon. Although the systematic position of M. bucklandii is unresolved, Benson et al. (2008) regard it as a possible member of the clade comprising of Ceratosauria and Tetanurae but not an abelisaurid or coelophysoid. Further, the characteristic dentary morphology present in all known spinosauroids is absent in the lectotype dentary. Thus, Benson et al. (2008) recommend the discontinuation of allying Megalosaurus with Spinosauroidea and also the practice of referring any other taxa as "megalosaurid".

So I guess we should stop using Megalosauridae and "megalosaurids" and start referring to these taxa (with the exclusion of Megalosaurus) as spinosauroids...

In my opinion, just because of its historical importance to dinosaur research, the most significant discovery in the future would be the discovery of a more complete specimen indisputably assignable to Megalosaurus bucklandii - that is, the associated specimen of a M. bucklandii dentary with other cranial and postcranial materials. The discovery of such a specimen is probably the only way to resolve the systematic position of M. bucklandii and the taxonomy of all other unassociated materials previously referred to M. bucklandii.

Reference:
Benson, R. B. J., P. M. Barrett, P. Powell, and D. B. Norman. 2008. The taxonomic status of Megalosaurus bucklandii
(Dinosauria, Theropoda) from the Middle Jurassic of Oxfordshire, UK. Paleontology 51: 419-424


Abstract: The lectotype of the Middle Jurassic theropod dinosaur Megalosaurus bucklandii, a right dentary, can be diagnosed on the basis of two unique characters: a longitudinal groove on the ventral part of the lateral surface of the dentary and a slit-like anterior Meckelian foramen. This taxon, the first dinosaur to be scientifically described, is therefore valid. Currently, however, no further material can be referred to this species with any certainty. Megalosaurus bucklandii occupies an uncertain systematic position but is not an abelisaurid or coelophysoid. Additionally, it does not possess the diagnostic dentary characters that are present in all known spinosauroids. Owing to this uncertainty, use of the family Megalosauridae should be discontinued until such time as its systematic position becomes clearer.

Comments

Zach Miller said…
I'm not surprised that Megalosaurus is a chimaera, given the state of paleo in those days. And you're right, there's probably not going to be a whole lot of taxonomic re-shuffling. Everybody who used to be a megalosaur might either fall under Spinosauroidea or Sereno's Torvosauridae.
Mambo-Bob said…
Either way will be really cool - whether the traditional "megalosaurs" still form a monophyletic Torvosauridae (==Megalosauridae) or if there will be a paraphyletic grade of basal spinosauroids/spinosaurids...

Popular posts from this blog

R for beginners and intermediate users 3: plotting with colours

For my third post on my R tutorials for beginners and intermediate users, I shall finally touch on the subject matter that prompted me to start these tutorials - plotting with group structures in colour.

If you are familiar with R, then you may have noticed that assigning group structure is not all that straightforward. You can have a dataset that may have a column specifically for group structure such as this:

B0 B1 B2 Family
Acrocanthosaurus 0.308 -0.00329 3.28E-05 Allosauroidea
Allosaurus 0.302 -0.00285 2.04E-05 Allosauroidea
Archaeopteryx 0.142 -0.000871 2.98E-06 Aves
Bambiraptor 0.182 -0.00161 1.10E-05 Dromaeosauridae
Baryonychid 0.189 -0.00238 2.20E-05 Basal_Tetanurae
Carcharodontosaurus 0.369 -0.00502 5.82E-05 Allosauroidea
Carnotaurus 0.312 -0.00324 2.94E-05 Neoceratosauria
Ceratosaurus 0.377 -0.00522 6.07E-05 Neoceratosauria
Citipati 0.278 -0.00119 5.08E-06 Oviraptorosauria
Coelophysi…

The difference between Lion and Tiger skulls

A quick divergence from my usual dinosaurs, and I shall talk about big cats today. This is because to my greatest delight, I had discovered today a wonderful book. It is called The Felidæ of Rancho La Brea (Merriam and Stock 1932, Carnegie Institution of Washington publication, no. 422). As the title suggests it goes into details of felids from the Rancho La Brea, in particular Smilodon californicus (probably synonymous with S. fatalis), but also the American Cave Lion, Panthera atrox. The book is full of detailed descriptions, numerous measurements and beautiful figures. However, what really got me excited was, in their description and comparative anatomy of P. atrox, Merriam and Stock (1932) provide identification criteria for the Lion and Tiger, a translation of the one devised by the French palaeontologist Marcelin Boule in 1906. I have forever been looking for a set of rules for identifying lions and tigers and ultimately had to come up with a set of my own with a lot of help fro…

Top 10 scientifically important theropod dinosaurs of all time (off the top of my head)

I thought I'd do a fun post for once. And since list based articles are the norm for fun on the internet, I thought I'd do one on dinosaurs, but given that I know most about theropods, I've decided to restrict my list to theropods (...maybe in a future post, I'll do other clades).

My ranking is based mostly on scientific importance so it may not reflect awesomeness, and it is obviously subjective as to how I rank importance to science. For instance, interesting discoveries or unique palaeobiology are ranked relatively low compared to wealth of information and data or completely revolutionising our understanding of the evolution of theropods.

So here are my top 10 scientifically important theropod dinosaurs of all time (off the top of my head)

10. Megalosaurus

Being the first dinosaur to be named, Megalosaurus automatically deserves a spot on this list, but given the fragmentary nature of known fossil specimens, and being mostly useless as a meaningful source for biologi…