It’s no secret – at least, not if you’re a regular SV-POW! reader – that the Lower Cretaceous Wealden Supergroup of southern England includes more than its fair share of enigmatic sauropod remains (see Mystery sauropod dorsals of the Wealden part 1, part 2, part 3). Poor taxonomic decisions, a dearth of adequate descriptive literature, and (perhaps) the vague concept that sauropod diversity in the Lower Cretaceous of Europe must be low have combined to prevent adequate appraisal. Recent comments on Wealden sauropods have been provided by Naish et al. (2004), Naish & Martill (2007), Taylor & Naish (2007) and Mannion (2008).

Chondrosteosaurus_R46870_resized

One of the most interesting Wealden sauropods – and I mean ‘interesting’ in an entirely subjective, historiographical sense – is Chondrosteosaurus gigas. This taxon has a rather confusing history that I don’t want to repeat here. The type series consists of two cervical vertebrae: BMNH R46869 and BMNH R46870 (and it is BMNH R46870, despite the occasional use in the literature of ‘46780’). We’ve looked at BMNH R46869 before. This time round I want to briefly talk about BMNH R46870. Anyone familiar with the literature on Wealden sauropods will know that this specimen was sectioned and polished. However, to date, only half of BMNH R46870 has been published (Owen 1876, plate V; Naish & Martill 2001, text-fig. 8.4), on both occasions as a mirror-image of the actual specimen. Previously unreported is that both halves of the specimen were polished, and both are in the Natural History Museum’s collection today. And here they are, shown together for the first time ever. I screwed up on the lighting, so sorry for the poor image quality [images © Natural History Museum, London].

A little bit of science has been done on this specimen. Chondrosteosaurus has had a mildly controversial history: it’s been suggested at times to be a camarasaur, but its camellate interior show that it’s a titanosauriform. Because the exact ratio of bone to air can be measured, the specimen lends itself particularly well to an Air Space Proportion analysis of the sort invented by Matt. Indeed, Matt did some ASP work on the figured half of BMNH R46870 in his thesis, finding an ASP of 0.70 (Wedel, Phd thesis, 2007). The average ASP of sampled neosauropod vertebrae is 0.61, and an ASP of 0.70 for the mid-centrum (as opposed to the condyle or cotyle) is most similar to the values present in camarasaurs and brachiosaurs. Mid-centrum ASP values of titanosaurs seem to be lower (Wedel, Phd thesis, 2007).

Chondrosteosaurus_R46870_closeup_resized

Anyway, more on Wealden sauropods – hopefully, a lot more – in the future.

References

  • Mannion, P. 2008. A rebbachisaurid sauropod from the Lower Cretaceous of the Isle of Wight, England. Cretaceous Research 30, 521-526.
  • Naish, D. & Martill, D. M. 2001. Saurischian dinosaurs 1: Sauropods. In Martill, D. M. & Naish, D. (eds) Dinosaurs of the Isle of Wight. The Palaeontological Association (London), pp. 185-241.
  • Naish, D. & Martill, D. M. 2007. Dinosaurs of Great Britain and the role of the Geological Society of London in their discovery: basal Dinosauria and Saurischia. Journal of the Geological Society, London, 164, 493-510.
  • Naish, D., Martill, D. M., Cooper, D. & Stevens, K. A. 2004. Europe’s largest dinosaur? A giant brachiosaurid cervical vertebra from the Wessex Formation (Early Cretaceous) of southern England. Cretaceous Research 25, 787-795.
  • Owen, R. 1876. Monograph on the fossil Reptilia of the Wealden and Purbeck Formations. Supplement 7. Crocodilia (Poikilopleuron). Dinosauria (Chondrosteosaurus). Palaeontographical Society Monographs, 30, 1-7.
  • Taylor, M. P. & Naish, D. 2007. An unusual new neosauropod dinosaur from the Lower Cretaceous Hastings Beds Group of East Sussex, England. Palaeontology 50, 1547-1564.

We have sometimes neglected tails on SV-POW!, in favour of the more obviously charismatic charms of presacral vertebrae, but every now and then you come across a caudal vertebra so bizarre that it just cries out to be blogged.

One such is this specimen, which may or may not be BMNH R 2144:

Sauropod caudal with co-ossified chevrons, lateral view

Sauropod caudal with co-ossified chevrons, right lateral view

Sauropod caudal with co-ossified chevrons, right posterolateral view

Sauropod caudal with co-ossified chevrons, right posterolateral view

The reason I’m not sure whether this is BMNH R2144 is that I noticed this at the very last minute while visiting the NHM collections to see a different specimen, and just had time to take a couple of quick photos before kicking-out time.  The label on the side of the vertebra has the unexplained number 2144 written on it, so I am guessing this is the specimen number, but I wouldn’t stake my life on it.

(By the way, both these photographs are copyright the NHM.)

The interesting thing about this vertebra is of course that that the chevrons are co-ossified with the centrum — an extremely rare condition in sauropods, in fact unique as far as I know.  As we’ve shown here and here, among other places, the chevrons are usually separate bones from the vertebrae.

This vertebra caught my eye not only because it’s, well, weird, but also because I’d seen it a couple of times in published figures.  It’s in Mantell’s (1850) description of Pelorosaurus, where it appears as figure 11 in plate XXIII, and is considered to belong to Pelorosaurus; and also in Owen (1859: plate V: figs. 3-4).  Owen seems pretty confused about the identity of this element, and in this paper alone assigns it to Streptospondylus (p. 22), Iguanodon(!) (p. 25) and implicitly Cetiosaurus (p. 34).  So what is it?  Well, its provenance is vague in the extreme, so given that it’s not associated with any more diagnostic material, about the best we can say with any honesty is that it’s Sauropoda incertae sedis.

Let’s take a look at those old figures:

Mantell (1850: plate XXIII, fig. 11)

Mantell (1850: plate XXIII, fig. 11)

Owen (1850: plate V, figs 3-4)

Owen (1850: plate V, figs 3-4)

If you’re like me, your first thought was that Owen’s figures are simply mirror images of Mantell’s.  I checked this out by Photoshopping the two sets of figures, flipping them horizontally, scaling and rotating as necessary, and found to my mild surprise that Owen’s figures are in fact redrawn, despite the startling resemblance they bear to Mantell’s.  As it happens, the same is true with the Owen 1859 plate that is the humerus of Pelorosaurus figured by Mantell 1850, and in that case Owen’s figure is rather better than Mantell’s, so let’s give a bit of credit to Owen here.  Most embarrassing for Mantell (not that he cares, having been dead for 157 years) is that Owen’s flipped images seem to be correct (at least, as best I can judge from the photographs I took) — looks like Mantell or his illustrator badgered this up.

So what is going on with these co-ossified chevrons?  As is so often the case, we just don’t know.  Some possibilities: this might be a pathology of an individual, caused either by injury or infection; it might be a natural ontogenetic character in very old individuals; or it might by a taxonomically significant character of a taxon we’ve not yet found — or one that we have found, but don’t yet recognise as being the same thing.  It’s perfectly possible that this is a chevron of Xenoposeidon, for example, but until someone finds a nice complete specimen we’ll never know.

Not much is known about skeleton fusion in sauropods, and most of what’s in the literature is anecdote.  That is set to change, I am pleased to say, as Matt is putting together a paper with his colleague Elizabeth Rega that will survey and interpret the various fusions known in sauropod vertebrae.  I’m looking forward to seeing what they have to say about this vertebra.

References

  • Brusatte, Stephen L., Roger B. J. Benson, and Stephen Hutt.  2008.  The osteology of Neovenator salerii (Dinosauria: Theropoda) from the Wealden Group (Barremian) of the Isle of Wight.  Monograph of the Palaeontographical Society 162 (631): 1-166.
  • Calvo, Jorge O., Juan D. Porfiri, Claudio Veralli, Fernando Novas and Federico Poblete.  2004.  Phylogenetic status of Megaraptor namunhuaiquii Novas based on a new specimen from Neuquen, Patagonia, Argentina.  Ameghiniana 41 (4): 565-575.
  • Mantell, Gideon Algernon.  1850.  On the Pelorosaurus: an undescribed gigantic terrestrial reptile, whose remains are associated with those of the Iguanodon and other saurians in the strata of Tilgate Forest, in Sussex.  Philosophical Transactions of the Royal Society of London 140: 379-390.
  • Owen, R.  1859a.  Monograph on the fossil Reptilia of the Wealden and Purbeck formations.  Supplement no. II (pages 20-44 and plates V-XII): Crocodilia (Streptospondylus, &c.) [Wealden].  Palaeontographical Society, London.

Update

Thanks to Mickey Mortimer for pointing out that this kind of centrum-chevron fusion is known in the theropod Megaraptor.  Here is the relevant figure from Calvo et al.’s (2004) revision of that genus:

Calvo et al. (2004: fig. 5). Caudal vertebrae of Megaraptor with co-ossified chevron

Calvo et al. (2004: fig. 5). Caudal vertebrae of Megaraptor with co-ossified chevron

The strange thing is this comment in the text (p. 569): “Two articulated caudal vertebrae are preserved (figure 5), slightly laterally compressed.  Their centra and the neural arches are firmly co-ossified, as well as their respective haemal arches [i.e. chevrons].  This fusion, not infrequent among dinosaurs, may be pathological.”  Not infrequent?  Is this going on all over the place and I’ve just never noticed it?  Anyone have any more examples?

Update 2

Here is that pair of fused Neovenator caudals with a co-ossified chevron, which Darren mentions in the comments below.

Brusatte et al. (2008: fig. 16d), fused Neovenator caudals with co-ossified chevron

Brusatte et al. (2008: fig. 16d), fused Neovenator caudals with co-ossified chevron

It’s been a while since we looked at everybody’s favourite partial dorsal vertebra, and there may be those who feel we’ve said all that can be said about it, but there is one feature of Xenoposeidon that we’ve never really highlighted here and which is well worth a look.

For anyone who’s not up to speed, a super-brief resumé: Xeno is an indeterminate neosauropod which Darren and I named in 2007 on the basis of a single element, a superbly preserved partial dorsal vertebra loaded with distinctive features that make it very clearly distinct from any other named taxon.  For anyone who wants more background, the original paper is freely available, as is a page summarising the story for the media, some unnofficial supplementary information, and a whole week’s worth of SV-POW! posts.

Here is the canoncial Xenoposeidon photo: the specimen in left lateral view.  (Don’t worry, this old chestnut is not your Picture of the Week — it’s just setting the scene.)

Xenoposeidon holotype BMNH R1095, left lateral view

Xenoposeidon holotype BMNH R1095, left lateral view. Copyright the NHM.

Up near the top of the preserved part of the vertebra, where the neural arch is broken off, there is a distinctive “V”-shaped pair of laminae, which we identified as accessory infraparapophyseal and infrapostzygapophyseal laminae. The more posterior of the two (on the right as we look at at it here) has a very distinctive wrinkled texture, and that’s what I want to show you today:

Xenoposeidon holotype BMNH R2095, left lateral view. Detail of accessory infrapostzygapophyseal lamina showing wrinkled bone texture

Xenoposeidon holotype BMNH R2095, left lateral view. Detail of accessory infrapostzygapophyseal lamina showing wrinkled bone texture. Copyright the NHM.

Now I’ve heard different things said of those wrinkles: I’ve never seen them on any other specimen of anything before, but then I’ve not seen a whole lot of material. Other people have told me that this kind of thing is pretty common, though I don’t recall anyone ever having told me a specific other specimen that has it.  What is completely clear is that no-one seems to know what it is or what it means.  It’s very hard to see how this could be the result of any kind of post-mortem distortion, so this must be what the bone was like when the animal was alive.  What are the possibilities?

  • I wondered whether it could be some kind of pneumatic feature, perhaps the trace left by a diverticulum or set of diverticula; but IIRC Matt doesn’t think that’s likely.
  • Could it be the result of some sort of infection?  Maybe neontologists, or for that matter doctors, see this kind of thing all the time but we poor palaeontologists are ignorant.
  • Er … what else?  Seriously, I am out of ideas here.

So, comments are open.  Enlighten me.  What is the cause of this distinctive texture?

Oh, and finally — for some reason, I don’t think I’ve ever mentioned that I uploaded most of the Xenoposeidon news spots onto Youtube a while back.  So if anyone wants to hear me talking about my favourite subject, and arguing with the Channel 4 News guy, or indeed just wants to see how mainstream media can get a science story completely right when we trouble to give them good information, get over to http://www.youtube.com/user/Mirk101

Happy Xenoposeidon day!  Today, November 15, 2008, is the one-year anniversary of the publication of Xenoposeidon Taylor and Naish 2007.

By happy coincidence, I’ve just been sent a courtesy copy of Kids Only, a new guide-book for the Natural History Museum … and there is Xenoposeidon on page 5, exemplifying dinosaur diversity.  Rock!

nhm-kids-only-p5-xenoposeidon-500px

It’s good to see our baby out there educating people!

For much more of Xeno, see Xenoposeidon week.

Today, we bring you the long-overdue third installment in everyone’s  favourite Mystery Sauropod Dorsals serial, our trawl through the NHM’s collection of mostly isolated elements from the Wealden Supergroup.

Many of these elements are too bashed up to be diagnostic (with the Xenoposeidon holotype R2095 being an honourable exception).  But there are one or two that are much better preserved, and arguably the best of these are the pair of elements BMNH R88/R89, which in some sense belong to “Eucamerotus” (read on).  These are difficult to photograph well, because they are in a glass case in the public gallery, but fortunately Hulke (1880: plate IV) illustrated the more anterior and better preserved of the two:

plate IV)

Like far too many British sauropod specimens, this one is mired in a taxonomic hell-hole. It was described by Hulke as belonging to Ornithopsis, a genus based on a horribly non-diagnostic type specimen, and it is this name that appears on the exhibit label (along with the incorrect specimen numbers R89/90 … oh well, One Out Of Two Ain’t Bad.)

Here is my least bad photo of R88 and R89, in left lateral view, with R88 on the left:

dscn1431-500px

Blows (1995) referred this pair of dorsals, and a bunch of other specimens, to another ancient British name, Eucamerotus — in fact, he nominated them as paratypes — but didn’t give any reason for doing so.  (He also referred to the R88/R89 pair jointly as R90, thus further muddling the specimen numbering.)  Blows’s reassignment to Eucamerotus is puzzling, because while the Eucamerotus type specimen is also pretty undiagnostic, consisting only of a partial neural arch, it does have one obvious apomophy, which is huge robust parapophyses supported on what I like the call The Prezygaparapophyseal Laminae Of Doom.  (Remind me to show you this specimen some time.)  That feature, of course, R88 and R89 completely lack.

So what are they?  I don’t think they can be referred with any confidence whatsoever to either Ornithopsis or Eucamerotus, two questionable genera of which at least the first is invalid.  So perhaps the right thing to do would be to torpedo those names and raise R88/89 as the type specimen of a new taxon?  There’s more work to do before taking such a step, not least an exhaustive trawl through the historical literature, but I think that might eventually prove the way to go.

Based on general proportions and overall “gestalt”, these vertebrae appear to be brachiosaurid — but I put them in a cladistic analysis a while back (so far unpublished) and they didn’t clade unambiguously with Brachiosaurus, so we’ll have to see how that develops when I finally get around to adding my thirty-odd new characters of the dorsals.  Don’t hold your breath.  At least, these elements are much more convincingly brachiosaurid than anything else I’ve seen from the Wealden.  So do they consitute Britain’s best brachiosaur?

Well, maybe.  Not if you count The Archbishop, Migeod’s Tendaguru brachiosaur, which I’ve been working on for waaay too long now, but really, really will describe Real Soon Now.  (Amazingly, this specimen has yet to appear on SV-POW!, unless you count my T-shirt in one of the photos of our Oxford Museum visit.)  But since this specimen is from the Tendaguru Formation of Tanzania, it should probably be discounted from the BBB competition.

In fact, Britain’s Best Brachiosaur is probably the “Barnes High Sauropod” from the Isle of Wight. But that’s in private hands and the ownership/availability situation is complex.  For that reason, no-one has yet published on it, and in fact I have never seen any of the material except what’s embedded in a wall-mount at Dinosaur Isle.  I’m not sure what’s happening with this specimen (I don’t think anyone is) but if I ever get a chance to find out, I will!

References

  • Blows, William T.  1995.  The Early Cretaceous brachiosaurid
    dinosaurs Ornithopsis and Eucamerotus from the Isle of
    Wight, England.  Palaeontology 38 (1): 187-197.
  • Hulke, J. W.  1880.  Supplementary Note on the Vertebræ of Ornithopsis, Seeley, = Eucamerotous, Hulke.  Quarterly Journal of the Geological Society 36: 31-35.  doi:10.1144/GSL.JGS.1880.036.01-04.06

In this article I’d like look at something that I’ve just spoken about at a conference: the ‘Dinosaurs – A Historical Perspective’ meeting held in London on May 6th and 7th (my thoughts on the conference can be found here and here). Mike attended too (and, like me, gave a talk), but Matt couldn’t make it. Anyway…

 

 

Today, the idea that sauropods (and non-avian theropods) were pneumatic animals is well established and universally accepted (a minority view – promoted by those who insist that birds cannot be dinosaurs – maintains that non-avian dinosaurs were not pneumatic, but I see no indication that the workers concerned know what they’re talking about). Indeed, sauropod pneumaticity has been discussed a lot here at SV-POW! But have people always regarded sauropods as pneumatic? As someone particularly interested both in pneumaticity and in the dinosaurs of the Lower Cretaceous Wealden Supergroup of southern England, the whole ‘Pneumaticity: the Early Years’ story is of special interest to me. I hope you get something out of it too…

 

Actually, the very first dinosaur (not just sauropod, but dinosaur) identified as exhibiting skeletal pneumaticity is from the Wealden, and it’s a theropod: it’s the large tetanuran Becklespinax altispinax, discovered prior to 1855 in the Hastings Beds Group of East Sussex (the Hastings Beds Group is the oldest unit in the Wealden Supergroup: for more see the Tet Zoo article here). Consisting only of three articulated posterior dorsal vertebrae, Becklespinax exhibits deep fossae on the sides of the neural arches (by now you’ll all be familiar with the names for the different vertebral laminae present in saurischians, but the fossae have names too: in Becklespinax, we’re talking about the infraprezygapophyseal fossa, the infradiapophyseal fossa, and the infrapostzygapophyseal fossa). The key thing is that, in describing these vertebrae, Richard Own (1804-1892) realised that these fossae were probably pneumatic as they are in birds, and in his 1856 article on Megalosaurus (he assumed that the Becklespinax vertebrae belonged to Megalosaurus), he wrote that ‘Three deep depressions, probably receiving parts of the lungs in the living animal, divide these lamelliform butresses from each other’ (Owen 1856, p. 5). His ‘lamelliform butresses’ are what we call laminae. This is the very first reference to pneumaticity in any Mesozoic dinosaur (Britt 1993), so Becklespinax is the first non-avian dinosaur for which pneumaticity was ever suggested.

 

The next milestone in pneumaticity came from Harry Seeley (1839-1909) in his description of the Wealden sauropod Ornithopsis hulkei (Seeley 1870). O. hulkei was named for two dorsal vertebrae: BMNH R2239 from East Sussex and BMNH R28632 from the Isle of Wight, but the former was later removed from O. hulkei (then becoming the type for Bothriospondylus elongatus), leaving BMNH R28632 alone associated with this name and as the lectotype* [the specimen is shown below, from Seeley 1870]. The strong opisthocoely, large lateral foramina and camellate internal anatomy show that BMNH R28632 is from a titanosauriform (it can’t really be identified more precisely than that and whether it’s diagnostic is arguable: see Naish & Martill 2007. For previous SV-POW! comments on the specimen go here). It’s often noted that Seeley suggested that these vertebrae belonged to an animal ‘of the Pterodactyle kind’. However, he did not think that these vertebrae belonged to a giant pterosaur (as, oops, Naish & Martill (2001) said): rather, he thought that O. hulkei represented something entirely new, the first member of a ‘new order of animals which will bridge over something of the interval between birds and Pterodactyles, and probably manifest some affinity with the Dinosaurs’ (Seeley 1870, p. 280).

 

* When a species is erected for more than one specimen, the specimens are all called syntypes. When one syntype from a series is later elected to serve as the type specimen for the species, it is called the lectotype.

 

 

 

Seeley – who has been described as ‘the most defiant’ of Victorian palaeontologists, of exhibiting ‘anarchic tendencies’, and of being considered ‘strikingly individualistic’, even in his own day (Desmond 1982) – gets a lot of flack these days, in particular for his rampant taxonomic splitting and naming of new dinosaur and pterosaur species, and also for his unusual views on how vertebrate groups were related to one another. But I often think that his conclusions on lifestyles and comments on palaeobiology are really not unreasonable in view of what we think today, and in fact often seem quite far-sighted.

 

Here’s where we come back to pneumaticity: Seeley (1870) was very impressed with the enormous lateral foramina present in O. hulkei (these were the main feature which led him to regard O. hulkei as allied to pterosaurs and birds), and he wrote: ‘Seeing that in living animals these foramina exist for the prolongation of the peculiarly avian respiratory system into the bones, and that no other function is known for them, we are compelled to infer for this animal bird-like heart and lungs and brain’ (Seeley 1870, p. 280). In describing the worn condyle of BMNH R28632, Seeley noted the presence within the bone of ‘enormous honeycomb-like cells of irregular polygonal form … divided by exceedingly thin and compact films of bone’ (Seeley 1890, p. 281). Elsewhere in the paper, he referred to the internal cavities as ‘air-cells’, and he also wrote of the Ornithopsis vertebrae (both BMNH R2239 and BMNH R28632) as ‘being constructed after the lightest and airiest plan’. He never explicitly stated it, but I infer from these statements that Seeley imagined the internal cavities of the centrum to be pneumatic: he was describing what today we call the camellae (that is, the numerous small pneumatic cavities that occupy the centrum in mamenchisaurs and titanosauriforms). So, all in all, I say well done Seeley for correcting inferring vertebral pneumaticity in O. hulkei.

 

Like most Victorian palaeontologists, Seeley did not get on particularly well with the most prolific, most respected and most politically powerful Victorian palaeontologist, Richard Owen [although it’s not really accurate to regard Owen just as a palaeontologist: sure, he did palaeontology, but his contribution to mainstream zoology and anatomy was massive and equally significant, if not more so]. In 1876, Owen described another Wealden sauropod and, like the O. hulkei lectotype (BMNH R28632), it was from the Isle of Wight’s Wessex Formation: it’s based on two cervical vertebrae (BMNH R46869 and BMNH R46870: one is shown below). Today, it is obvious that these vertebrae are from sauropods, and their enormous lateral foramina and camellate internal anatomy show that they’re from titanosauriforms (and not from camarasaurs as has been suggested in the past: see Naish & Martill 2001, 2007). However, Owen couldn’t be this confident that identified the material as ‘Dinosauria (?)’.

 

 

 

The big deal for our story is that these vertebrae have massive lateral fossae housing large lateral foramina, and again Owen correctly interpreted them as pneumatic, writing: ‘The whole of the side of the centrum is occupied by a deep oblong depression which, probably, lodged a saccular process of the lung’ (Owen 1876, p. 6). So far so good. But Owen had one of these two Wessex Formation specimens (BMNH R46870) sectioned, revealing its incredible (and beautiful) interior [it’s the image shown at the very top]. The internal anatomy of this specimen illustrates camellate texture so well that it’s almost becoming a poster-child in talks and articles on sauropod vertebrae. But while, as we just saw, Seeley had implied that camellae were pneumatic, Owen interpreted them quite differently. He wrote ‘I deem it much more probable that the large cancelli obvious at every fractured surface of this vertebra were occupied in the living reptile by unossified cartilage, or chondrine, than by air from the lungs, and consequently have no grounds for inferring that the whale-like Saurian, of which the present vertebrae equals in length the largest one of any Cetacean recent or fossil, had the power of flight, or belonged to either Pterosauria or Aves’ (Owen 1876, p. 6). To reflect the presence of ‘chondrine-filled’ spaces in the vertebrae of this animal, Owen coined for it the new name Chondrosteosaurus gigas, meaning ‘giant cartilage and bone lizard’.

 

Quite why Owen was happy with pneumatic lateral fossae, but not with pneumaticity within the body of the centrum itself, seems odd, especially when Owen was very familiar with avian anatomy (he specifically referred to the internal anatomy of avian vertebrae in, for example, his 1859 article on pterosaur vertebrae [Owen 1859]). As you can see in Tutorial 3, the internal anatomy of bird and sauropod centra are so similar that it is difficult not to conclude that what applies for one applies for the other. However, it is clear from Owen’s quote given above that, when interpreting C. gigas, he was not just doing an objective description, but also had an axe to grind: he was specifically refuting Seeley’s statements on O. hulkei, hence the rejection of the idea that C. gigas might have been capable of flight, or that it might be allied to pterosaurs or birds. For whatever reason, Owen was also making note of the fact that he disagreed with Seeley’s idea of a pneumatic vertebral interior: the name Chondrosteosaurus itself almost seems like a snub to Seeley.

 

Despite this one-upmanship, ultimately, both Seeley and Owen come out of this early phase in research pretty well, as both workers still win citations for having made key early statements on saurischian pneumaticity (e.g., Wedel 2003, O’Connor 2006). Edward Cope (1840-1897), who liked Seeley and said nice things about him, was to note during the 1870s that sauropod vertebrae were probably pneumatic, and Othniel Marsh (1831-1899) did likewise. What happened in the field of dinosaur pneumaticity after this? Well, that’s a story for another time: for the time being I will direct you to Wedel (2003).

 

References

 

  • Britt, B. 1993. Pneumatic Postcranial Bones in Dinosaurs and Other Archosaurs. Unpublished PhD thesis, University of Calgary (Alberta).
  • Desmond, A. J. 1984. Archetypes and Ancestors: Palaeontology in Victorian London 1850-1875. The University of Chicago Press, Chicago. 
  • Naish, D. & Martill, D. M. 2001. Saurischian dinosaurs 1: Sauropods. In Martill, D. M. & Naish, D. (eds) Dinosaurs of the Isle of Wight. The Palaeontological Association (London), pp. 185-241.
  • Naish, D. & Martill, D. M. 2007. Dinosaurs of Great Britain and the role of the Geological Society of London in their discovery: basal Dinosauria and Saurischia. Journal of the Geological Society, London 164, 493-510.
  • O’Connor, P. M. 2006. Postcranial pneumaticity: an evaluation of soft-tissue influences on the postcranial skeleton and the reconstruction of pulmonary anatomy in archosaurs. Journal of Morphology 267, 1199-1226.
  • Owen, R. 1856. Monograph on the fossil Reptilia of the Wealden and Purbeck Formations. Part III. Dinosauria (Megalosaurus). Palaeontographical Society Monographs 9, 1-26.
  • Owen, R. 1859. On the vertebral characters of the Order Pterosauria, as exexmplified in the genera Pterodactylus (Cuvier) and Dimorphodon (Owen). Philosophical Transactions of the Royal Society of London 149, 161-169.
  • Owen, R. 1876. Monograph on the fossil Reptilia of the Wealden and Purbeck Formations. Supplement 7. Crocodilia (Poikilopleuron). Dinosauria (Chondrosteosaurus). Palaeontographical Society Monographs 30, 1-7.
  • Seeley, H. G. 1870. On Ornithopsis, a gigantic animal of the pterodactyle kind from the Wealden. Annals and Magazine of Natural History, Series 4, 5 279-283.

Invading the postzyg

March 30, 2008

7306-fossa-medial-side-postzyg-resized.jpg

Again, another exclusive peek at an interesting specimen: the MIWG.7306 vertebra, aka ‘Angloposeidon’ (Naish et al. 2004). Apologies if, by now, you’re bored of my show-casing of this specimen, but – not only is it the only sauropod vertebra of which I personally have multiple unpublished images – it is also a really nice demonstration of the fact that, even in just a single vertebra, there are multiple interesting, bizarre, and sometimes under-studied or even un-studied details.

What we’re looking at here is the medial (‘inside’) surface of the left postzygapophysis, with the centrum down below the bottom of the image, and the cotyle off to the left (the opposite side of what’s shown here). The image below should help with orientation. The focus of interest is the unusual matrix-filled space in the middle of the image: just what is it? Because it has sharp, clean edges, I am pretty convinced that it’s natural, and I assume it’s a pneumatic foramen. Similar structures are present on the medial side of the right postzygapophysis, and are different in position and shape (Naish et al. 2003, p. 790). We think, based on several lines of evidence, that the space between the postzygapophyses (limited anteriorly by the neural spine) was occupied by an air-sac (Schwarz & Fritsch (2006) called this the interspinal diverticulum), so is this evidence that diverticula from the interspinal air-sac invaded the bodies of the postzygapophyses on their medial sides? If so, was this just a one-off in MIWG.7306, or was it widespread in brachiosaurs, in macronarians, in neosauropods, or even in sauropods as a whole? I admit that I haven’t yet taken the time to check properly, but the big problem is that this part of the vertebra – the medial surface of the postzygapophysis – is rarely figured. Based on what has been published, I have yet to see a similar structure, even in Brachiosaurus (which is very well figured, as sauropods go).

miwg7306-prezyg-fossa-composite-resized.jpg

I’m sure that someone is now going to make me look very, very silly. But, whatever. I can’t pretend to know everything. Note that, again, this is a world first. Yes, all of this stuff should be published… and in time in will, in time.

References

  • Naish, D., Martill, D. M., Cooper, D. & Stevens, K. A. 2004. Europe’s largest dinosaur? A giant brachiosaurid cervical vertebra from the Wessex Formation (Early Cretaceous) of southern England. Cretaceous Research 25, 787-795.
  • Schwarz, D. & Fritsch, G. 2006. Pneumatic structures in the cervical vertebrae of the Late Jurassic Tendaguru sauropods Brachiosaurus brancai and Dicraeosaurus. Eclogae geol. Helv. 99, 65-78.