It’s an oddity that in eight years of SV-POW!, we’ve never written about one of the best of all the Wealden-formation sauropod specimens: the forelimb and associated skin impression NHMUK R1870 that is known as “Pelorosaurus” becklesii.
Let’s fix that. Here is all the bony material (i.e. everything except the skin patch) in a photo taken in the basement of the Natural History Museum back in 2007:
Left forelimb material of “Pelorosaurus” becklesii holotype NHMUK R1870. Left: humerus, in posterior view. Right, from top to bottom: ulna in anterior view; radius in anterior view. Yes, I should have turned the humerus over before taking this photo. What can I tell you? I was young and stupid then.
As you can see, the two lower-limb bones were broken back then (though I believe they have since been repaired), but the breaks are very clean, and it’s actually quite interesting to see inside the bones:
Breakage in bones of the lower left forelimb of “Pelorosaurus” becklesii holotype NHMUK R1870. Left: proximal part of radius in distal view. Right: proximal part of ulna in distal view.
I wish I knew enough about mineralisation to comment intelligently on what we can see there. If anyone has thoughts, do leave them in the comments.
We can look in more detail at those lower-limb bones in a subsequent post, but for now, here’s the humerus:
“Pelorosaurus” becklesii holotype NHMUK R1870, left humerus. Top row: proximal view, with anterior to the bottom. Middle row, from left to right: medial, anterior, lateral and posterior views. Bottom row: distal view, with anterior to the top.
As you can see it’s in really nice shape, and pretty distinctive. Way back in my 2007 Progressive Palaeo talk (Taylor 2007), I coded up the humerus (alone, without the other elements) in the Harris-based phylogenetic matrix that I’ve used repeatedly in other projects. It came out as the sister taxon to the titanosaur Malawisaurus (which in that matrix comes out fairly basal within Titanosauria): in fact, it could hardly do anything else, since the coding was exactly the same as that of Malawisaurus.
And indeed it’s been pretty widely accepted that “P.” becklesii is a titanosaur — one of the earliest known, and the only name-bearing one from the Wealden Supergroup, unless you count the extremely indeterminate Iuticosaurus, which predictably enough is based on a single eroded partial mid-caudal centrum. Still, the titanosaurian identity of “P.” becklesii has never been convincingly demonstrated — only inferred by non-cladistic means.
“Pelorosaurus” becklesii holotype NHMUK R1870, left humerus in anterodistal view (anterior to the left).
So why the quotes around the genus name “Pelorosaurus“? Because it’s long been recognised that, whatever this specimen might be, it ain’t Pelorosaurus, which is based on the “Cetiosaurus” brevis caudals and a much more slender humerus.
Here’s that humerus, so you can see how different it is from that of “Pelorosaurus” becklesii:
Right humerus of Pelorosaurus conybeari holotype NHMUK 28626. Top row: distal view, with anterior to bottom. Middle row, left to right: lateral, anterior and medial views. Bottom row: distal view, with anterior to top. Missing parts reconstructed from the humerus of Giraffatitan brancai (Janensch 1961: Beilage A)
Paul Upchurch recognised the generic distinctness of “Pelorosaurus” becklesii way back in his (1993) dissertation. But because of Cambridge University’s policy of only making copies of dissertations available for £65, that work is effectively unknown. (Perhaps we should all chip in a fiver, buy a copy and “liberate” it. Or maybe 22 years on, Paul would rather leave it in obscurity and let his reputation continue to rest on his impressive body of later work.)
What has happened to this specimen in the last 22 years? Very little has been published about it. It got a mention in the systematic review of sauropods in Dinosauria II (Upchurch et al. 2004), but
the only mention that is more than in passing, as far as I’m aware, is that of see Upchurch’s first published (1995) phylogenetic analysis. From page 380:
The only reliable Lower Cretaceous titanosaurid material, apart from Malawisaurus, comes from Europe, especially England. The earliest of these forms may be represented by the forelimb of ‘Pelorosaurus becklesii‘ (Mantell 1852) from the Valanginian of Sussex. This specimen was considered to be Sauropoda incertae sedis by McIntosh (1990b). However, a skin impression shows polygonal plates of a similar shape and size to those found in Saltasaurus (Bonaparte & Powell 1980). The ulna and radius are robust and the ulna bears the typical concavity on its anteromedial proximal process. Upchurch (1993) therefore argued that this form should be provisionally included within the Titanosauridae.
[Update: as Darren points out in the comment below, Upchurch et al. (2011) figure the specimen in colour and devote three pages to it. They leave it as Titanosauria, and “refrain from naming a new taxon until more comparative data are available” (p. 501).]
Given my interest in the Wealden, it’s surprising that we’ve never blogged about “Pelorosaurus” becklesii before, but it’s true: I’ve mentioned it three times in comments, but never in a post. It’s good to finally fix that!
Next time: the radius and ulna.
- Janensch, Werner. 1961. Die Gliedmaszen und Gliedmaszengurtel der Sauropoden der Tendaguru-Schichten. Palaeontographica (Suppl. 7) 3:177-235.
- Taylor, Michael P. 2007. Diversity of sauropod dinosaurs from the Lower Cretaceous Wealden Supergroup of southern England. p. 23 in Graeme T. Lloyd (ed.), Progressive Palaeontology 2007, Thursday 12th-Saturday 14th April, Department of Earth Sciences, University of Bristol. 38 pp.
- Upchurch, Paul. 1993. The Anatomy, Phylogeny and Systematics of Sauropod Dinosaurs. Ph.D dissertation, University of Cambridge, UK. 489 pages.
- Upchurch, Paul. 1995. The evolutionary history of sauropod dinosaurs. Philosophical Transactions of the Royal Society of London Series B, 349:365-390.
- Upchurch, Paul, Paul M. Barrett and Peter Dodson. 2004. Sauropoda. pp. 259-322 in D. B. Weishampel, P. Dodson and H. Osmólska (eds.), The Dinosauria, 2nd edition. University of California Press, Berkeley and Los Angeles. 861 pages.
- Upchurch, Paul, Philip D. Mannion and Paul M. Barrett. 2011. Sauropod dinosaurs. pp. 476-525 in: Batten, David J. (ed.), English Wealden Fossils. The Palaeontological Association (London).