Skip to main content

Torvosaurus

I initially named this sketch Megalosaurus but then remembered that I've been relying on the proportions of Torvosaurus for the reconstruction, so it's been renamed to Torvosaurus. Torvosaurus is a North American "megalosaur" popularly used to aid in the reconstructions of the English Megalosaurus mostly because the long-held assumption that these two taxa are closely related. However, more recent phylogenetic analyses show that the traditional monophyletic Megalosauridae does not seem to exist anymore but rather a paraphyletic "Megalosauridae" with a paraphyletic grade of "megalosaurs" leading up to the Spinosauridae. Or something like that...there seems to be quite a lot of confusion in this area of the theropod phylogeny probably because of the lack of good specimens. Although, in a consensus tree of published trees, a fair chunk of the traditional "megalosaurs" still seem to come together in a smaller but yet monophyletic Megalosauridae.

Anyway, I quite like these basal tetanurans as they are so enigmatic. Megalosaurus has historically been used as a "waste-basket" taxon, i.e. if the affinities of a new taxon is indeterminable, then it is attributed to the genus "Megalosaurus". Some very famous taxa such as Dilophosaurus or Eustreptospondylus were initially attributed to Megalosaurus. In the 1960's to the 1970's many new Chinese theropods were also given the name Megalosaurus, which were subsequently reassigned to new genera. Because of this, Megalosaurus had the longest temporal range of all theropod genera starting at the Rhaetian in the Triassic ("M". cambrensis = Zanclodon cambrensis) all the way up to the Cretaceous ("M". crenatissimus = Majungasaurus crenatissimus). Of course Megalosaurus proper is fairly restricted to the Middle Jurassic.

Torvosaurus on the other hand is from the Late Jurassic of western North America and Portugal. In both settings, Torvosaurus was contemporaneous with other theropods: Allosaurus, A. fragilis in N. America and A. europaeus in Portugal; and Ceratosaurus in N. America. As with Ceratosaurus, Torvosaurus is relatively rare compared to Allosaurus.

Comments

Zach Miller said…
And according to Sereno, it formed an outgroup to the Spinosauridae, in a larger monophyletic clade called Spinosauroidea.

I don't know how sold I am on this idea. Thomas Holtz thinks that Megaraptor is a basal (but late-surviving) spinosauroid, which is just all kinds of awesome.

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…

R for beginners and intermediate users: reading and manipulating data

I had been preparing a comprehensive tutorial on how to plot in R (The R Project) with different groups differentiated in different colours, but Blogger stupidly erased my post and decided to automatically save my empty draft at that precise moment. Since I cannot reproduce the original post, I decided to break it up into a series of smaller topics.
There are plenty of R resources available in various places but I found that they are frequently one of two extremes; either too basic or too advanced.  I think of myself as an intermediate user (i.e., I can comfortably handle canned packages but want a bit more control than the default settings allow) so the type of info I find are not too helpful. So I thought it would benefit others like me if I summed up some of the simple things I learned over the last year or two.
As a first of such posts, I will deal with reading in and manipulating data.  These may be very simple and basic, but some of the things I wanted to do required a bit more th…