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Wednesday, 27 May 2015

New takes on the Wealden Supergroup palaeobiota, part 1: Iguanodon, Neovenator, Eotyrannus and others

Regular readers will know that I'm prone to dabbling in palaeoart depicting the environments and animals of the Wealden Supergroup, the 18 million year stretch of Early Cretaceous time represented by mud-and sandstone deposits across the southern UK. Recently, I've been updating some existing Wealden work as well as producing some new stuff of other Wealden species. With no time to produce a new post of substance, here's a bumper 'picture of the day'-type post. Initially, I was going to chuck something like ten images on here, but time has run short and I'll have to split it in two.

If you like anything here, remember that you can buy prints of them all from my shop (there's now a Wealden section, too), which is now also browsable from the comfort of Facebook. OK, enough preamble: into the Wealden once again...

Iguanodon bernissartensis: thumb wars

Two Iguanodon bernissartensis, the quintessential Wealden iguanodont, decide to settle their differences, while members of their herd watch on.
Poor old Iguanodon doesn't get the attention it used to, and a lot palaeoart we do see of it tends to focus on tried and tested behaviours: lots of standing about and eating, but not much else. In this new painting, I've attempted to show two big Iguanodon individuals settling an intra-specific dispute via use of thumb spikes. Long-term readers may recall that we've covered iguanodont thumb spikes before, and that I. bernissartensis has especially big ones. Here, they've been swinging their thumbs at each other's soft bits, causing deep, bloody wounds. This might seem extreme, but there are plenty of modern animals which take intraspecific fights to similarly gory levels - elephant seals were a key inspiration here. I imagine battling Iguanodon would look like an armed sumo-wrestling match, albeit with longer tails and less rice. Note that you can see the breath of several animals here: Wealden winters are not meant to be especially warm.

Rebbachisaurids vs. Neovenator salerii redux

Carcharodontosaurian Neovenator salerii stalks a pair of rebbachisaurid sauropods, using darkness as cover.
A while back I posted about dinosaur predation, noting that modern animal predator acts are often far less gladiatorial and epic than we might imagine. It's this slow, considered approach to predation which I'm attempting to show here, as the carcharodontosaur Neovenator stalks two rebbachisaurid sauropods in the dead of night. The idea is that the Neovenator has much better eyesight than the sauropods, who know they're in trouble, but can't really respond adequately. Note the rain: some recent models of Wealden palaeoclimates suggest it was wetter than previously modelled (albeit with very high evaporation rates for much of the year).

Anteophthalmosuchus hooleyi vs. Hypsilophodon foxii, redux

Large goniopholidid Anteophthalmosuchus hooleyi takes advantage of a flooding river to hunt two stranded Hypsilophodon foxii.
Speaking of rain, we know that some parts of the Wealden were prone to flooding following particularly intense downpours. That's good news for animals adapted for powerful swimming, but less welcome to species which prefer dry land. Here, in this reworked painting, the large Wealden goniopholidid Anteophthalmosuchus hooleyi has found a stranded pair of adult and juvenile Hypsilophodon foxii, and is taking full advantage of the situation. Goniopholodids are a group of almost-crocodiles characterised by long forelimbs, interlocking scutes and overbitten jaws - you can read more about them here.

Eotyrannus lengi: firestarter, redux 

Early tyrannosauroid Eotyrannus lengi stalks the edge of such a wildfire. 
What else does rain bring? Sometimes, lightning. When introduced to a parched Wealden landscape, lightning strikes caused short-lived canopy fires which, ultimately, created conditions ideal for fossil preservation. In this reworked painting, a fully-feathered tyrannosauroid Eotyrannus lengi is prowling the periphery of a Wealden canopy fire to grab any animals flushed out by the flames.

The tiny wars of Wesserpeton evansae, redux 

Two Wesserpeton evansae get in each other's faces, because some animals are just jerks.
OK, enough about Wealden weather. Here's a reworked version of two of the Wealden's tiniest tetrapods - indeed, some of the smallest fossil tetrapods of all - facing off in leaf litter. Recently named Wesserpeton evansae, these are albanerpetontids, very small amphibians which only died out a few million years ago. The 35 mm snout-vent length of these animals did nothing to temper their ferocity, and numerous jaws of Wesserpeton have healed fractures and breaks from intraspecific tussles. The animals in this picture are speaking the aggressive body language of modern salamanders as a prelude to their conflict. Two sauropods hang around in the background because, hey, it's called the Age of Dinosaurs for a reason. Some people have suggested this image borders on the trippy and surreal. Stay off the shrooms, kids. 

Rebbachisaurids and chums

Lower Cretaceous rebbachisaurids and giant sauropod 'Angloposeidon' look for water in this desiccating Wealden lake.
I do like rebbachisaurids, that group of sauropods who didn't get the memo about long necks. They're only represented by scrappy remains in the Wealden (a scapula) which is enough to tell us they were there, but not substantial enough to carry a name. Here, a few individuals are digging around a rapidly drying lake-bed to find a substantial source of water: digging elephants were the inspiration for this scene. In the background, probable brachiosaurid 'Angloposeidon' struts its stuff. It's meant to be walking particularly tall - I like the idea that fossil animals would carry themselves in different, characteristic ways, just as modern animals do. A pink gnathosaurine pterosaur has snuck into the foreground, just because. 

A lesser-seen Wealden scene: the Hastings Beds palaeobiota


Finally for now, here's one more new painting. This is a reconstruction of a swollen river representing part of the Hastings Beds, the oldest deposits of the Wealden, complete with local reptile fauna. The animals shown here are really poorly known: titanosaur 'Pelorosaurus' becklesii (bits of forelimb), possible carcharodontosaurian Becklespinax altispinax (three dorsal vertebrae), eucryptodiran turtle Hylaeochelys belli (a shell), and the possible azhdarchoid previously known as 'Palaeornis cliftii' (humerus). So yes, take the 'restorations' of these animals with an evaporite mine of salt: they're really just better known, fairly 'generic' representatives of groups represented by these Wealden taxa, air-dropped into a Wealden setting. Becklespinax is obviously modelled closely on Concavenator, as they seem to be pretty closely related and have a similar taste in dorsal ornamentation. I gave Becklespinax a more vertical anterior sail margin however, as indicated by the fossil. There's an article waiting to be written on palaeoart like this - should we even bother 'reconstructing' poorly known scenes and species? I clearly think we should, but we'll have to discuss the reasons why another time. 

I'm just now realising that there's a lot of confrontation in these images. Come back soon for a more placid, relaxed set of pictures in part 2...

Monday, 11 May 2015

And I, for one, welcome our new wukongopterid pterosaur overlords (to Europe)

Upper Jurassic pterosaur Cuspicephalus scarfi, a species of some uncertain affinity, now confidently restored as a wukongopterid. How come? Read on. If you'd like a print of this image, please head to my print store.
One of the most significant pterosaur discoveries of recent years are the wukongopterids: small, upper Jurassic pterosaurs unknown before 2009 and most familiar in popular circles for Darwinopterus modularis. These pterosaurs are renowned for providing a morphological bridge between the two major stages of pterosaur evolution: the loose group of long-tailed species which dominated the Triassic and Jurassic phases of pterosaur history, and the Pterodactyloidea, short-tailed, large-skulled creatures which represent a second, better known phase of pterosaur evolution.

The manner in which wukongopterids link these groups will be familiar to many. Instead of showing a mosaic of basal and derived characteristics as expected from any species slotting into a evolutionary 'gap', their heads and necks developed a anatomies like those of pterodactyloids while their bodies and limbs retained features typical of earlier pterosaurs (Lü et al. 2010). Wukongopteridae is generally considered the sister taxon to the Pterodactlyoidea, the two forming the clade Monofenestrata after their shared attribute of combined nasal and antorbital openings. To date, all wukongopterids have been recovered from the Middle/Late Jurassic Tiaojishan Formation of China and, thanks to many complete specimens, their anatomy is already quite well known. The number of valid wukongopterid species remains uncertain: at least seven have been named, but some authors suggest these are oversplit to such an extent that they should all be synonymised into one species, D. modularis (Lü et al. 2012). This is yet to be investigated in detail but, if correct, note that wukongopterid posterboy D. modularis does not have nomenclatural priority. At least one other wukongopterid species was named a few months before D. modularis; two were if you take the 2010 paper version of the description as the ‘true’ publication date of D. modularis, not the 2009 online release.

Wukongopterids are not the only pterosaurs shedding light on the origins of the Pterodactyloidea. The recent discovery of another obviously ‘transitional’ taxon, the Late Jurassic, Solnhofen ‘Painten pro-pterodactyloid’ (Tischlinger and Frey 2014), seems to present a step towards pterodactyloid anatomy from that presented by wukongopterids. The only known specimen of this animal, which is privately owned and thus remains nameless, also shows some modularity of evolution with the body and limbs retaining hallmarks of earlier pterosaur evolution, while the skull has developed into something very similar to Jurassic ctenochasmatoids, especially Pterodactylus antiquus.

Monofenestratan pterosaur skulls. A, the wukongopterid Darwinopterus robustodens; B, likely pterodactyloid sister-taxon the ‘Painten Pro-pterodactyloid’; C, ctenochasmatoid Pterodactylus antiquus; D, azhdarchoid Tupuxuara leonardii; E, early dsungaripteroid Germanodactylus rhamphastinus; F, ornithocheiroid Ornithocheirus mesembrinus; G, early dsungaripteroid Germanodactylus cristatus. Scale bars represent 10 mm, except for D and F, which represent 100 mm. Note that neither A or B are pterodactyloids (the rest are), despite the similar skull shapes. Can we identify their skulls as non-pterodactyloidian without the help of postcranial anatomy? From Witton et al. 2015.
A crucial question concerning these new monofenestratan pterosaurs is how we recognise them without evidence of their combined ‘early pterosaur’ bodies and ‘pterodactyloid’ heads and necks. All current diagnoses of these pterosaurs rely on this combination of characteristics and, by necessity, need relatively complete specimens for identification. What can be done with fragmentary specimens, the likes of which comprise most pterosaur fossils? At least two teams of authors have suggested that limb proportions of non-pterodactyloid monofenestratans are characteristic so, as long as sufficient limb material is known, their isolated bodies have some chance of being identified. But what about their strikingly pterodactyloid-like skulls? In isolation, these bear so much resemblance to those of Jurassic pterodactyloids like Germanodactylus and Pterodactylus (above) that referral outside of Pterodactyloidea is unlikely without an associated, 'early-grade' body.

This is an issue my University of Portsmouth colleagues David Martill, Michael O’Sullivan and I tackled in a new (open access) paper, published today in Contributions to Zoology (Witton et al. 2015). Our interest in this problem is not purely theoretical, this paper picking up questions set down three years ago in the description of Cuspicephalus scarfi, a poorly-known British Jurassic monofenestratan (Martill and Etches 2012). Represented only from a partial skull (below) sharing similarities with both wukongopterids and the pterodactyloid Germanodactylus, Cuspicephalus remained of uncertain affinity when first described (Martill and Etches 2012 – an overview of this paper can be found at Dave Hone’s Archosaur Musings). In the same publication, Martill and Etches remarked that another European Jurassic pterosaur only known from cranial material (jaw tips), Normannognathus wellnhoferi (below), suffered similar problems to Cuspicephalus, its once sensible pterodactyloid identification (Buffetaut et al. 1998) now being questionable with wukongopterids on the scene. Taking the Martill and Etches study as our cue, we decided to take a closer look at the characteristics of non-pterodactyloid monofenestratan crania, and apply our findings to these two poorly-known European pterosaurs.

Jurassic pterosaur fossils aren't all complete skeletons and preserved soft-tissues - most of them look like this. A, MJML K1918, holotype skull of the long-snouted pterosaur Cuspicephalus scarfi Martill and Etches, 2013; B, MGCL 59’583, holotype of Normannognathus wellnhoferi Buffetaut et al., 1998. Scale bars represent 50 mm (A) and 10 mm (B). From Witton et al. 2015
I don’t want to rehash our anatomical comparisons in full here – the paper is free for all to read, so you can easily find these details there – but we concluded that yes, wukongopterid skulls are identifiable in isolation - we don't need associated postcrania to identify them. Their skulls are quite generalised in construction and best diagnosed by a combination of 16 character states relating to skull shape, features of the orbit, dentition and cranial crest anatomy, but we also found one character more-or-less unique to the group: an atypically long nasoantorbital fenestra. In exceeding 50% of the jaw length, only two derived Cretaceous pterodactyloid clades (istiodactylids and azhdarchoids) can boast longer nasoantorbital openings than wukongopterids. We also found that the ‘Painten pro-pterodactyloid’ also has its own take on monofenestratan cranial anatomy: like wukongopterids, it is best distinguished via a combination of features, but details of its dentition provide genuine apomorphies.

When applying these findings to our poorly-represented European specimens, we found virtually all evaluable features of Cuspicephalus (13 of 16) matched those of the wukongopterid character complex, it even bearing that especially long nasoantorbital fenestra. By contrast, it differs from the ‘Painten pro-pterodactyloid’ and ‘generic’-looking pterodactyloids such as Germanodactylus quite markedly. I’m happy that, as part of our means of demonstrating this, we managed to get some new details of Germanodactylus cristatus anatomy into the literature. There are specimens of this animal showing really big exoccipital processes (flaring projections anchoring neck muscles at the back of the skull - see illustration, above), but they remain relatively poorly documented. These processes not only have bearings on distinguishing Germanodactylus from Cuspicephalus, but might help resolve disputes about the placement of Germanodactylus among Pterodactyloidea (the relationships of this animal are controversial, but big exoccipitals are only known in dsungaripterid pterosaurs, one of the suggested phylogenetic homes of this taxon). The only feature really distinguishing Cuspicephalus from wukongopterids are some minor details of its anterior tooth placement, which we see as relatively little concern given strong similarities elsewhere and propensity for dental variation among even closely related pterosaurs. We conclude that the close relationship between Cuspicephalus and Darwinopterus suggested by Martill and Etches (2012) is likely, and go further in suggesting Cuspicephalus is a member of Wukongopteridae itself - the first to occur outside of China.

The picture is not so straightforward for Normannognathus however. Most of the characters once used to suggest Normannognathus was related to certain pterodactyloids are now realised as features seen across Monofenestrata, and, in being represented by only jaw tips and one tooth, there's not much to compare with other pterosaurs. A suite of features seen in Normannognathus (including crest height, upturned jaws, dental characteristics and midline jaw grooves) are found in ctenochasmatoid pterodactyloids, and we tentatively suggest it might have some link to this group. However, without more data, it’s hard to be certain exactly where in Monofenestrata this species belongs. Admitting defeat with Normannognathus suggests that our abilities to distinguish types of monofenestratan skulls remain a little limited, even after dedicated study – anything less than a near-complete skull (like the Cuspicepahlus holotype) might prove a challenge to identify.

Cuspicephalus was a relative giant compared to other wukongopterids: that's the second biggest wukongopterid (D. robustodens) on the left. Still, they're not enormous animals overall, as demonstrated by the use of a European robin (Erithacus rubecula) for scale. From Witton et al. 2015.
Are there any bigger-picture implications to our paper beyond taxonomy? Accepting that this is not a 'game changing' paper, we've at least started adding depth to our understanding of wukongopterid pterosaurs, which I’m happy about. Because these animals were previously only known from a very restricted pocket of space and time (Callovian/Oxfordian strata of China), their identification in Europe allows us to start appreciating the geographic and temporal range this group. Cuspicepahlus occurs in late-Kimmeridgian stage rocks, inferring that wukongopterids enjoyed at least 5-10 million years of evolutionary history, spread across Jurassic Laurasia.

Moreover, Cuspicephalus gives us an insight into the disparity of wukongopterids. It is the first wukongopterid with really obvious morphological distinction to previously known Chinese species, which are distinguished by such minor details that, as noted above, their taxonomy has been questioned. Cuspicephalus possesses a much longer, lower skull than any Chinese wukongopterid, as well as packing in more teeth at the anterior end of its jaws. It’s difficult to say what that means functionally, although we speculate that greater jaw reach and ability to handle small, slippery prey might be related to these features. Cuspicephalus is also considerably larger than its relatives in China, its skull exceeding 300 mm in length to make it one of the biggest Jurassic pterosaur skulls known. Interestingly, this does not translate into a particularly large animal overall: the heads of wukongopterids are proportionally large, and our wingspan estimate for Cuspicephalus (based on skull/wingspan ratios in other wukongopterids) is a relatively modest 1.2 m. The largest Jurassic pterosaurs span well over 2 m, so it remains moderately sized at best. However, its wingspan is still a lot larger than any other known wukongopterid however, which can be measured as spanning no more than 884 mm.

We're not quite done with Jurassic pterosaurs here yet: several on-going projects on the functionality of these pterosaurs, some of which are in the publication system, should be emerging in a few months. Hopefully, we won't be waiting long for them...

References

  • Lü, J., Unwin, D. M., Jin, X., Liu, Y., & Ji, Q. (2010). Evidence for modular evolution in a long-tailed pterosaur with a pterodactyloid skull. Proceedings of the Royal Society B: Biological Sciences, 277: 383–389.
  • Lü, J. C., Unwin, D. M., Zhao, B., Gao, C., & Shen, C. (2012). A new rhamphorhynchid (Pterosauria: Rhamphorhynchidae) from the Middle/Upper Jurassic of Qinglong, Hebei Province, China. Zootaxa, 3158, 1-19.
  • Martill, D. M., & Etches, S. (2012). A new monofenestratan pterosaur from the Kimmeridge Clay Formation (Kimmeridgian, Upper Jurassic) of Dorset, England. Acta Palaeontologica Polonica, 58(2), 285-294.
  • Tischlinger, H. & Frey, E. 2014. Ein neuer Pterosaurier mit Mosaikmerkmalen basaler und pterodactyoider Pterosaurier aus dem Ober-Kimmeridgium von Painen (Oberpfalz, Deutschland) [A new pterosaur with moasic characters of basal and pterodactyloid Pterosauria from the Upper Kimmeridgian of Painten (Upper Palatinate, Germany)]. Archaeopteryx 31, 1-13.
  • Witton, M. P., O’Sullivan M., & Martill, D. M. 2015. The relationships of Cuspicephalus scarfi Martill and Etches, 2013 and Normannognathus wellnhoferi Buffetaut et al., 1998 to other monofenestratan pterosaurs. Contributions to Zoology, 84(2), 115-127.

Friday, 10 April 2015

Mamenchisaurus youngi presents a money-off print offer and other links of interest

Jurassic sauropod Mamenchisaurus youngi was a pretty freaky looking thing: a weird, upturned tail base; some sort of 'sail' along the hip/tail junction; a hugely oversize neck and massive shoulders. Here, one is shown engaging in a bird-like threat display: head and neck down, vocalising, and elevating its tail. The other is engaging in bird-like can't-be-botheredness.   Prints of this image are available here.
With apologies for a post entirely devoted entirely to loosening money from your pockets, there are three items of newsworthiness I want to share here. Two of them are even for decent, well-meaning causes. The other is my livelihood, which I also consider a good cause, but I'm aware I have a biased opinion on that.

1. Lots of new art at my print store, and a 20% discount for savvy types

In addition to updating this blog and Twitter, I also regularly add new artwork to my online print store. Much as I try to give each piece full airing and discussion here, I struggle to do this for all my work in a timely fashion, and they end up on sale before an accompanying article can be produced. Recent additions include:


*Thanks to co-conspirators Robert Gay and ReBecca Hunt-Foster for concepts and assistance with these pieces!

If you'd like to own a high quality Giclée print of one of these, or any of the other 29 paintings in there, now is a good time to purchase one. Until the end of April you can obtain a 20% discount on the print costs by entering the promotional code 'APRIL2015' at the store checkout. The code doesn't apply to shipping costs, but knocks a hefty chunk off the prints themselves. Armed with this code, prices range from £16-40 instead of their £20-50. All purchases support the production of more art and articles, so every purchase is sincerely appreciated.

It's not official until there's a shareable image for social media.

2. It's fund-raising auction time at the Portsmouth's Natural History Museum!

My local natural history museum, Cumberland House, is attempting to raise money for a new bee hive exhibition via an eclectic auction next week. The auction takes place on April 15th and offers a huge range of stuff: furniture, artwork, days out, full-blown holidays, money off cruise fares and a whole lot more. There's lots of stuff here which will be of interest to those outside of the local area and bids can be made remotely - you don't have to attend the auction personally to obtain some of that cool stuff. There's even some palaeoart for sale - a framed print of my 'Tyrannosaurus vs. bees' painting. Details of this, and a full low-down on the lots, are available in the auction catalogue (here) and at the Friends of Cumberland House Facebook page

3. Mammoth is Mopey (again)

Yeah, I know I've mentioned this before, but it's such a good project that I want to make sure it's known as widely as possible. Mammoth is Mopey is a book for younger readers showing a different prehistoric animal for each letter of the alphabet, with each species accompanied by a fun, quirky illustration. In keeping with the sauropod themed opener of this post, here's the Mammoth is Mopey 'Boastful Brontomerus'.

From Mammoth is Mopey, which you can support here. Illustration by David Orr.
As you might tell by the inclusion of this relatively obscure species, Mammoth is Mopey is going to introduce children and their parents to a new suite of prehistoric animals in a very fun, memorable way. It's rare to see projects aimed at very young children trying to break new ground like this, and that alone seems good reason to support it. The book, by David and Jennie Orr (David being well known for founding Love in the Time of Chasmosaurs), is currently halfway through an Indiegogo campaign and received just over 50% funding. With outreach exercises also riding on the successful funding of this project, it would be great to see it meet the $10,000 target in the next 20 days.

Right, that's my attempt to fleece readers of their money done for now. Less commercially-minded posts will follow soon.

Thursday, 9 April 2015

The weird, awesome, and weirdly awesome, Triassic hindlimb-glider Sharovipteryx mirabilis

Sharovipteryx mirabilis, a tiny reptilian 'hindlimb glider' from the Late Triassic of Kyrgyzstan. A Triassic spider is thrown in for fun (spiders are a very ancient group, and were almost certainly present along the ancient lakes frequented by Sharovipteryx). Prints of this painting can be purchased here.
Sharovipteryx mirabilis is a mainstay of books on prehistoric animals, a Triassic Kyrgyz species mentioned frequently as a weird and wonderful, non-dinosaurian Mesozoic species. It is best known for its hindlimb-dominated approach to gliding, but also achieves some popularity via suggestions that it might be closely related to pterosaurs. This relationship is suggested by the possession of membranous flight organs in both lineages and some similarity in hindlimb structure. Recent studies have not looked favourably on this suggestion however, because the detailed anatomy of pterosaurs, distorted as it is by their flight adaptations, shows much greater similarity to that of dinosaurs and their immediate ancestors to that of Sharovipteryx. Moreover, with membranous gliding aids appearing and disappearing multiple times in the evolution of gliding species (including other fossil reptiles) their shared presence in Sharovipteryx and Pterosauria may have little evolutionary significance. Although the relationships of Sharovipteryx to other reptiles remain somewhat ambiguous (see below), most suggest they are part of Protorosauria, an early offshoot from the archosauromorphs which also includes weirdo taxa like Tanystropheus and the drepanosaurs.

The anatomy and proportions of Sharovipteryx are remarkable and unique. We only know of this species from a fossil discovered in 1965, later named and described in 1971 by Alexander G. Sharov. Initially called Podopteryx, it became Sharov’s namesake in 1981 when it was realised that a damselfly already existed with the former name. Our only specimen of Sharovipteryx is variably preserved – sometimes excellently, sometimes considerably less so. Although most of the skeleton is represented, some of the bones are crushed and the two bony slabs sharing the skeleton are split through the middle of some bones – most notably the skull. This has resulted in some controversy concerning detailed interpretations of Sharovipteryx anatomy and hindered discussions of its relationships to other animals. Some of these disagreements are significant, not the least being whether or not any material from the forelimbs is known. Some authors claim to have not only found elements of the arms, but enough to ascertain that that they were proportionally short. Others suggest there is no trace of them at all, and further interpretations suggest the arms were present, but damaged and modified during specimen preparation.

Holotype and only known specimen of Sharovipteryx mirabilis. From Gans et al. (1987).
Such details aside, many elements of Sharovipteryx appearance are relatively clear and can be crudely summarised as resembling a small (< 250 mm long, including tail), long-bodied lizard with enormous, membrane-bound legs. Skin impressions adjacent to the skull, torso and feet show the body was covered with small scales, some of which overlapped. The head was small (19 mm long) and narrow with a short snout, large eyes, small nostril openings and at least 15 small, sharp and widely-spaced teeth in each jaw. The neck and trunk are long and narrow, and of approximately equal length. The narrow tail was at least as long as the body and neck combined. Arm and shoulder bones, as indicated above, are at best very poorly known, or not known at all - depending who you ask. It is likely they were - like those of other protorosaurs - relatively short. It is a shame that we do not know them better: some protorosaur arms are adapted for unusual habits in truly bizarre ways, and given how strange many details of Sharovipteryx are, odd hand or forelimb anatomy would not be unexpected.

The legs of Sharovipteryx are, of course, the most striking feature of the animal. The crus is slightly longer than the thigh, with each bone being approximately as long, if not a little longer, than the torso. The five-toed feet are not especially slender however, although they are proportionally large and broad. Much of their size is devoted to the toes, which increase in size from digit I - V, while the body of the foot is rather short and robust.

Behind the legs and feet is a set of expansive, scale-less membranes extending from the base of the tail, along the posterior margin of the leg, and down to the large fifth toe. These membranes bear striations and folds radiating from the tightly-folded legs. The striations may be fibres within the membranes themselves, perhaps acting to control membrane flutter and aid neat membrane collapse, but the folds suggest Sharovipteryx membranes did not shrink entirely when the legs were folded in. Similarly folded membranes occur in some modern gliders, such as flying squirrels. It is widely thought that these membranes could be deployed as a gliding apparatus simply by extending the legs sideways, a posture clearly attainable in life given the fossilised pose of our sole Sharovipteryx specimen. It is unlikely that Sharovipteryx could flap its hindlimb wings however, its pelvis and hindlimb bones lacking suitable room and reinforcement for flapping muscle attachment.

Whether other membranes were present in front of the legs - or even along the arms - is debated. Some suggest they can be observed on the specimen, but this is not universally agreed on. There are aerodynamic reasons to suspect the posterior hindlimb membrane was not the sole flight surface, however. Studies modelling the glide performance of Sharovipteryx find that the centre of lift is located too far back along the body to safely glide and land without the aid of additional membranes. In other words, there is too much weight in front of the wing, and the animal would risk toppling forward in flight or landing at hazardous speeds. An anterior flight surface, perhaps along the front of the thigh or associated with the arms, would negate these issues and permit safer landings.

Alternative reconstructions of the flight apparatus of Sharovipteryx. Reconstruction 'd' not only provides the best glide path, but also makes flight safe enough to ensure happy landings. Scale bar is 20 mm. From Dyke et al. (2006).

How effective was hindlimb-dominated gliding? It is tempting to take the absence of this gliding mechanic from modern animals as a sign of inefficiency. After all, we see gliding and parachuting in fish, rodents, flying ‘lemurs’, frogs, snakes, lizards and more groups, and none rely on a gliding system approximating that of Sharovipteryx. Indeed, key similarities in gliding anatomies have developed within these groups, perhaps indicating certain 'optimal' gliding adaptations exist for vertebrates. For instance, both frogs and geckos glide on splayed tissues around their hands and feet. All gliding mammals sport extensive membranes between all four limbs. Gliding snakes and agamid lizards have mobile ribs which can expand their bodies into flattened aerofoils. Although the details of these structures differ – as would be expected given their development in such distantly related animals – it is nevertheless interesting that the same anatomical components have developed repeatedly into gliding organs. Perhaps the uniqueness of hindlimb-dominated gliding to Sharovipteryx indicates that it arose via an especially lax interval of natural selection and competition, and that it just doesn't cut the evolutionary mustard outside of the Triassic.

Flight models of the Sharovipteryx glide path conflict with this assessment, however. Indeed, some models of Sharovipteryx glide paths indicate more successful gliding abilities than skilled modern reptile gliders such as Draco, and potentially more manoeuvrability. The ability to control the principle flight membrane with movements of the legs and tail, along with additional (and hypothetical) assistance from forelimb membranes, likely conferred tight control over the glide path. It is notable that the uniqueness of Sharovipteryx gliding apparatus among animals is not carried over to human technology, its wing shape having been likened to delta wing aircraft - the sort of designs we see in fast, nimble fighter jets. In short, no experiments have suggested that the gliding apparatus of Sharovipteryx was ineffective or clumsy, and instead indicated quite the opposite.
Perhaps instead of viewing Sharovipteryx as an evolutionary oddball, we might wonder why more animals have not attained similar anatomies. I suspect the answer may lie in the need for a specific ancestral body form to become a hindwing-dominated glider. The legs must be relatively large to provide a suitable wing surface and possess greater potential for use as wings than the arms, as well as being able to project sideways. While there are plenty of animals with proportionally large hindlimbs, most are bipeds with hip joints particularly restrictive against lateral leg rotation. A small, lightweight body and head, probably reduced arms, long, balancing tail and perhaps climbing habits might also be ideal. It's difficult to think of species other than protorosaurs which might present such a combination of these characteristics, so the greatest potential for hindlimb gliders may have disappeared along with them at the end of the Triassic. Whatever the reason, the take home message is that Sharovipteryx as really a perfect recipe of genetic resources, adaptive pressures and animal behaviour to create a remarkable, unique and effective gliding animal, and not the result of an evolutionary wrong turn.

Of course, Sharovipteryx would not be gliding all the time: how did it move on land? Relatively little commentary exists on this point, but we might assume that terrestrial locomotion and climbing was used when foraging, perhaps for insects, given the absence of adaptations for aerial prey capture. Because the legs of Sharovipteryx are of such length, possibly much longer than the arms and support a large amount of soft-tissue, it is not unreasonable to wonder how walking and running was performed. Unfortunately, our lack of data on Sharovipteryx forelimb bones becomes a real issue here: modelling the terrestrial abilities of any extinct animal really has to start with knowing basic limb proportions. Protorosaurs seem to have been lizard-like quadrupeds, but the forelimbs of Sharovipteryx would have to be very long to operate in this fashion. Shorter forelimbs, as controversially-interpreted by some, do not strictly rule out quadrupedality, although they might require the adoption of frog- or rabbit-like hopping to work harmoniously with the enormous hindlimbs. Bipedality, of course, also cannot be excluded.

Quadrupedal or otherwise, the short, splaying foot of Sharovipteryx contrasts with the generally elongate feet of fast running animals. Despite its long limbs, Sharovipteryx was probably not adapted for routinely sprinting. This doesn’t completely rule out fast terrestrial locomotion of course – we see similar foot structure and limb proportions in rapidly running lizards like basilisks and frilled lizards – but we might assume it was not a regular part of Sharovipteryx habits. Climbing, however, like was: strongly built, asymmetrical feet with increasing lateral toe length like those seen in Sharovipteryx are common in climbing species. We might imagine Sharovipteryx as spending much of its time in tree canopies, and it is perhaps noteworthy that the fossil locality which yielded Sharovipteryx is also known for a diverse fossil flora. Artists might want to consider reconstructing Sharovipteryx with arms showing adaptations to climbing, given that climbing with hindlimbs alone might be very difficult - even for something as strange as Sharovipteryx. Strong feet may also be consistent with powerful leaping and impact absorption during landing, although – again – without knowing much about the Sharovipteryx forelimbs, reconstructing its landing cycle is difficult.

References

  • Dyke, G. J., Nudds, R. L., & Rayner, J. M. V. (2006). Flight of Sharovipteryx mirabilis: the world's first delta‐winged glider. Journal of Evolutionary Biology, 19(4), 1040-1043.
  • Gans, C., Darevski, I., & Tatarinov, L. P. (1987). Sharovipteryx, a reptilian glider?. Paleobiology, 415-426.

Wednesday, 25 March 2015

Tyrannosaurus and Triceratops - friends at last?

Tyrannosaurus and Triceratops, not locked in mortal combat. Something must be wrong.  Cretaceous interspecies adoption concept, mimicking similar behaviours seen in modern mammals and birds, by Chidumebi Browne. Prints are available here.
Is there a more iconic palaeontological scene than Tyrannosaurus facing down Triceratops? The artistic association of these taxa has existed since at least 1906 when the very first, highly influential restoration of Tyrannosaurus (by Charles Knight, of course) pictured these animals alongside each other (Glut 2008). This idea flowed into aspects the first dinosaur movies - The Ghost of Slumber Mountain (1918) and The Lost World (1925) (unsurprisingly, given how much these films are indebted to Knight) - and, by 1928, the year Knight completed the famous Field Museum mural of Tyrannosaurus and Triceratops, their adversarial relationship was truly cemented. Book illustrations, TV shows and films have so perpetually shown encounters between these species that it's difficult to think of a new angle on this scene. At least, that's what I thought until being contacted by Chidumebi Browne, who asked me about working up a second Tyrannosaurus picture for him, this time co-starring Triceratops. Instead of combat however, he wondered about likelihood of a juvenile Triceratops being 'adopted' by the tyrant, as some animals make the headlines for doing so today (see below). Clearly I liked the idea enough to carry out the commission (I try to avoid things I feel are too unreasonable), but is this pure speculation, playing on gaps in our knowledge, or is there something credible to this idea? Could Triceratops and Tyrannosaurus, after more than a century of conflict, learn to be friends?

The literature on animal adoption is vast, with something like 270 species of mammal and bird known to adopt juveniles of their own species (via kidnapping, accidental inheritance or other means - Riedman 1982; Avital et al. 1998). Interspecific adoption is far rarer however, and most records pertain to animals housed in zoos or wildlife park. These adoptions can work both ways: juveniles can 'recruit' surrogate parents as readily as parents adopt surrogate offspring (for instance, the bond between Owen, a young hippo, and Mzee, a century-old giant Aldabran tortoise, seems to mostly reflect efforts of the hippo). There is relatively little documentation of interspecies adoption in wild animals, however. The example everyone knows is the Kenyan lioness Kamunyak, who has become something of a sensation for her habit of adopting young oryx. She adopted at least six calves before she was last sighted in 2004, defending them from others - including predators, humans seeking to intervene, and oyrx mothers - as if they were her own cubs. At least one species of monkey, as well as wading, raptorial and passerine birds have also adopted and reared the juveniles of other species (Izar et al. 2006; Literak and Mraz 2011; Oswald et al. 2013). Brood parasitism - the offloading of parental duties to other species - clearly exploits this behaviour (Riedman 1982), and famously occurs in cuckoos, certain ducks and geese, cowbirds, fish and bees.

The significance and evolutionary purpose of these interspecific relationships remains mysterious in many cases. Of course, the internet is awash with suggestions that these species have become 'friends', typically accompanied by heavily-edited video footage showing two different species at their squeeful snugglywugilinest. If they feature predators engaging in joyful play or nurturing behaviour with usual prey species, all the better. According to those sagest of human beings - internet commenters - these examples of natural harmony show us - spiteful, war-making human beings - to be the real animals. Truly, we are awful.

In the real world, the causes of these relationships are considerably less fluffy. The fact that most interspecies adoptions develop in captivity is not surprising, likely resulting from the close quarters contact between individuals and the deficient of conspecifics. Desires for parents, mates or group behaviours in some animals may be so strong in some species that they become blinded to the clear differences between themselves and the only other individuals they know. It's difficult to know whether these examples provide good models for interspecific adoption in natural circumstances.

Pictured: trouble in the neighbourhood.
The rarity of wild cases of interspecies adoption makes it hard to draw any firm conclusions about its adaptive significance, if it even has any (Izar et al. 2006). Although juvenile animals may receive some benefit from being adopted (especially if the alternative is not having parents at all), most biologists consider interspecific adoption a mistake - 'misdirected parenting' from confused adults. For some instances of bird adoption, this might reflect the similar appearance of chicks within certain lineages: adults simply can't tell them apart (Oswald et al. 2013). The circumstances surrounding some 'adoptions' are truly bizarre, where adoptees are ex-prey items which have become surrogate offspring. This has certainly happened with sea eagles where, having brought local buzzard chicks back to their own nest, presumably to eat, they started rearing them instead (Literak and Mraz 2011). It is assumed that the appearance of a raptor chick in their nest overrode any feeding impulses of these eagles, and they successfully reared several buzzards in this fashion (Literak and Mraz 2011). The idea that these parenting 'misfires' reflect recognition errors is supported by at least one instance where Caspian terns, rearing Ring-billed gulls, dropped their degree of parenting as juveniles outgrew resemblance to typical tern offspring (Oswald et al. 2013).

It is less easy to explain adoption across taxonomic and ecological boundaries so wide that even passing resemblance is unlikely. It must be said here that peer reviewed literature on these cases is hard to find, at least in my experience, so much of what is reported online is found in documentaries and news stories - not the most ideal venues for discussing complex, unusual animal behaviour (this is not a sleight against the experts featured in such outlets, just that these things are highly-edited and narrative-hungry, which often leads to embellishment and distortion of facts). As an example of how highly selective these reports can be, some stories of lions 'adopting' prey animals result from 45 minutes of observation, receiving justified scepticism from biologists. 45 minutes of coexistence does not equal a clear case of adoption, especially in species renowned for toying with easily overpowered prey.

Where these cases carry more reliability - such as the widely verified case of Kamunyak and her oryx calves - behavioural factors remain unclear. It seems unlikely that a lioness would visually confuse an oryx calf was her own, except for the possibility that her eyesight was very poor. I see explanations that possible recent, traumatic loss of her (genetic) offspring as premature on the available evidence, most likely spurred on by a desire to project human values into a simplified narrative. The fact that Kamunyak ended up eating the starved carcass of one of her adoptees, and became a serial adoptee suggests her condition might be more complex and deeper-seated than a response to one recent event. Moreover, if cub death is the catalyst for this behaviour, would it not be more common in other lions? As far as I'm aware, cub death is a pretty frequent occurrence. It also strikes me that lots of medical conditions - head trauma, brain tumours, organ malfunction leading to hormone imbalances, even certain diseases - can drastically alter animal behaviour. As far as I'm aware, no assessment of Kamunyak's health was made before she disappeared. I wonder if an illness of some kind is a more parsimonious explanation of Kamunyak's condition than complex, psychological trauma.

Let's bring all this back to Chidumebi's concept: could extinct dinosaurs have engaged in inter-species adoption, especially species as different as Triceratops and Tyrannosaurus? We certainly know that modern animals can establish these weird relationships even between animals as different as large predators and tiny prey. We also know that dinosaurs are capable of inter-species adoption, because modern birds engage in this behaviour. On these analogies, a Tyrannosaurus adopting a Triceratops is not too far fetched. We might assume that their morphological distinctions are so great that the tyrant is not misidentifying the ceratopsid for offspring of its own, and thus must be a 'behaviourally abnormal' tyrannosaur: a Cretaceous Kamunyak, if you like. The background tyrants are meant to be behaviourally 'normal', and have sighted the Triceratops calf - I expect, as is reported for many of Kamunyak's adoptions, that the Triceratops infant would not last long.

So... is this the first picture of an obviously slightly unhinged tyrannosaur?
This exercise is hampered ultimately by a lack of knowledge about the parentage of fossil dinosaurs however, and particularly that of tyrannosaurs. Despite the relative wealth of knowledge on tyrant dinosaur palaeobiology (they are extremely well studied compared to other fossil groups), we still know very little, if anything, about tyrannosaur parental behaviour. Parenting is so varied among reptiles and birds that even phylogenetic brackets are of questionable use here. Strong parental instincts seem like a prerequisite for interspecific adoption, and the evidence is equivocal for such instincts in Tyrannosaurus. Until we know more about this, the likelihood of the scene above remains questionable. Of course, that doesn't mean the image composition is without merit: there are scenarios where predators and baby prey individuals coexist peacefully, such as when adult prey animals have run off and juveniles, being slower, have hidden instead. Indeed, such scenarios likely explain some hastily dubbed predator-prey 'adoptions' reported in the media. At least that provides a partial answer to our question, then: could Tyrannosaurus and baby Triceratops get along? Probably - at least until the former got hungry.

References

  • Avital, E., Jablonka, E., & Lachmann, M. (1998). Adopting adoption. Animal Behaviour, 55(6), 1451-1459.
  • Glut, D. (2008). Tyrannosaurus rex: a century of celebrity. In: Larson, P. and Carpenter, K. (eds) Tyrannosaurus rex, the tyrant king. Indiana University Press. 398-427
  • Izar, P., Verderane, M. P., Visalberghi, E., Ottoni, E. B., Gomes De Oliveira, M., Shirley, J., & Fragaszy, D. (2006). Cross‐genus adoption of a marmoset (Callithrix jacchus) by wild capuchin monkeys (Cebus libidinosus): case report. American Journal of Primatology, 68(7), 692-700.
  • Literak I, & Mraz J. (2011). Adoptions of young Common Buzzards in White-tailed Sea Eagle nests. The Wilson Journal of Ornithology 123(1), 174-176.
  • Oswald, S. A., Wails, C. N., Morey, B. E., & Arnold, J. M. (2013). Caspian Terns (Hydroprogne caspia) Fledge a Ring-billed Gull (Larus delawarensis) Chick: Successful Waterbird Adoption Across Taxonomic Families. Waterbirds, 36(3), 385-389.
  • Riedman, M. L. (1982). The evolution of alloparental care and adoption in mammals and birds. Quarterly Review of Biology, 405-435.

Sunday, 22 March 2015

More new-old art: Therizinosaurus, superpigeon, and Polacanthus, walking coffee table

Two Therizinosaurus cheliformis hanging out in Late Cretaceous Mongolia. The guy on the left thinks he's all that: she doesn't. Prints are available from my online store.

Time for more new takes on old pictures. First up, above, is a reworking of my 2013 image of two Therizinosaurus cheloniformis, giant therizinosaurids from Maastrichtian deposits of Mongolia. Before we knew just how bizarre Deinocheirus was, these pot-bellied, small-headed and scythe-clawed animals held the title of least expected anatomy in a non-avian theropod. The metre-long claws on their hands suggest they were dangerous, ferocious animals, and they are often restored with long arms and claws ready to lash out at passers by. I don't doubt that being clobbered by a Therizinosaurus would be an experience best avoided, but, being herbivores, they probably spent far more of their time eating and digesting that they did swatting other animals. For me, Therizinosaurus was figuratively 'de-clawed' for good in John Conway's restoration of them as squatting, shaggy 'feather mountains' harvesting leaves from trees. Since then, restorations of keen-eyed, 'scythe weilding' therizinosaurs have seen especially silly, even among other 'slasher pose' artwork.

My own restoration of these animals sides with the idea of Therizinosaurus being a large herbivore largely disinterested in the world around it. A clear source of reference for this painting were pigeons, specially the wood pigeon Columba palumbus. I find the proportions of these birds - tubby bodies, small feet, small heads - reminiscent of the anatomy of large therizinosaurs, and I thought it might be fun to mix the two together. The male animal on the left of the image is engaged in pigeon-like display behaviour, strutting around with a cocked head, inflated chest and making noises best described as 'übercoos'. The female, right, like most female pigeons presented with courting, couldn't be less interested (although, to be honest, it's hard to tell what pigeons find interesting: they always seem a bit confused to me. They're like avian Dougal McGuires).

Much as I normally try to avoid painting ancient animals in the clothes of modern species, I quite like the spin the pigeon-appearance puts on these animals. All too often Mesozoic dinosaurs are considered embodiments of savage natural selection and intense, often violent competition. There are few modern animals with characters further from this concept than pigeons, which succeed despite their apparent tendencies for confusion, pratfallery, and seemingly simple behaviour*. Transferring these qualities to the Mesozoic seems to put a different spin on ancient dinosaur lifestyles ecology.

*I say this with fondness: I find watching pigeons really interesting. I'm sure they're a lot more sophisticated than they often appear.

Wealden ankylosaur Polacanthus foxii and tiny feathered friends. Prints are available from my store.
Next up is another reworked 2013 piece, the large ankylosaur Polacanthus foxii on a Wealden hillock, with some speculative avians hitchikers. I was lucky enough to have a quick glimpse at some new Polacanthus material being worked on at the University of Southampton a few years back, including lots of limb and hip elements. The size of the specimens was really impressive (an impression helped, I guess, by the fact I'm used to working on much smaller, more gracile pterosaur bones) and it definitely seems that, like other ankylosaurs, Polacanthus was a 'walking coffee table': a low slung creature with a flattish back. The broad sacral shield of was probably an excellent place to put drinks, and experts have recently predicted that Polacanthus had very strict 'use a coaster' policy.

There are two species of birds show here: a flock of small, grey forms leaving the tree, and a suite of smaller brown birds hanging out on the Polacanthus itself. These animals are speculative additions to this Wealden scene as, while possible avialan teeth have from one Wealden formation (the Wessex) have been mentioned, I don't think they've been described or analysed in detail just yet. However, a diverse suite of small birds have been found in Lower Cretaceous deposits elsewhere in the world (including Wealden-equivalent deposits of Spain, and famously in China), so it's not a huge stretch to embellish a painting with such animals.

Thursday, 19 March 2015

Short-necked azhdarchid pterosaurs - say what?

LPV (FGGUB) R.2395, our unnamed short-necked azhdarchid from Maastrichtian deposits of the Hațeg basin. Prints of this chap are available.

Odds are that most regular readers of this blog are familiar with azhdarchid pterosaurs, the toothless, often gigantic flying reptiles which increasingly dominated pterosaur evolution in the Cretaceous. With a better fossil record than most pterosaur lineages, they are among the best understood and most researched of all flying reptiles. In recent years our understanding of their anatomy, distribution and palaeobiology has advanced considerably.

Since azhdarchids were recognised as a group in the 1980s it has been realised that their most striking and characteristic features pertain to their neck anatomy. In both relative and absolute terms they have the longest necks of any pterosaurs, stretching their mid-series cervical vertebrae to long tubes with reduced features. Cervicals IV - VI are especially long and tubular, with the mid-portions of the neural spines reduced to such a degree that they are effectively split into anterior and posterior sections. The only significantly developed features of these cervicals are bulbous zygopophyses and condyles, which nestle together so snugly that neck articulation seems limited. Regular readers will know that this has considerable bearing on the likely habits of these animals, probably precluding strenuous lifestyles such as skim-feeding or pelican-like scooping. The extremes of their neck bones - cervicals I - III, and the somewhat 'dorsalised' VIII - IX - are less modified, although some azhdarchid weirdness infects these too in terms of length, neural spine shape, or both.

With azhdarchid cervicals being so diagnostic, they can be identified when found in isolation and even when only poorly preserved. Indeed, many azhdarchid occurrences are represented by isolated cervicals - they compete with jaw tips for the most common type of azhdarchid fossil. In recent years, the complete neck osteology of the Santonian, central Asian azhdarchid Azhdarcho lancicollis has been documented in some detail (Averianov 2010), permitting some insight into which specific part of the neck sequence isolated neck bones represent. It can be a little tough to tell a cervical IV and V apart - they seem very similar, except that V is invariably the longer of the two (indeed, the longest of the entire neck) - but we can now at least tentatively identify bones from the rest of the sequence. This is a major breakthrough, meaning that isolated cervicals can tell us a lot more than just where an azhdarchid was preserved: their potential for taxonomic and biomechanical studies has been increased considerably.

Eyes to Romania

A lot of new azhdarchid material, including said isolated cervicals, has recently been emerging from various Maastrichtian deposits of Romania. These sediments represent the rivers and lakes which once ran through Hațeg island, an ancient setting famous for its dwarf dinosaurs and the enormous azhdarchid Hatzegopteryx thambema. The Hațeg pterosaurs, and their neighbours from Transylvania, have been the focus of a number of recent pterosaur papers and, this week, a team of researchers (including Mátyás Vremir, myself, Darren Naish, Gareth Dyke, Stephen Brusatte, Mark Norell, and Radu Totoianu) published another in American Museum Novitates (Vremir et al. 2015). It reports the discovery of just one bone* - the near-complete azhdarchid cervical LPV (FGGUB) R.2395, from Hațeg Basin red beds - but it's enough to cast new light on these otherwise familiar azhdarchid fossils, as well as the general evolution of azhdarchids themselves.

*So yes, the picture at the top is 1% fossil data, 99% palaeoart polyfiller.


Line drawing of LPV (FGGUB) R.2395, isolated azhdarchid cervical IV or V. It don't look like much, but it's got it where it counts. From Vremir et al. 2015.
R.2395 (above) is not a large vertebra, being an estimated 100 mm long and 44 mm across the prezygapophyses when complete (it's missing the posterior portion, including most of the condyle and postzygagpophyses, as well as the left prezygapophysis). Our paper provides a long discussion about the likely portion of the neck represented by R.2395, concluding that it is probably a cervical IV or V. In azhdarchids, these vertebrae are among the longest of all, sometimes being eight times longer than wide. R.2395 was clearly a lot stouter than this however, barely being twice longer than broad. This proportion is unique among azhdarchid CIV and Vs, and there was some discussion among our team as to whether or not this was sufficient to erect a new taxon. In the end we decided the material was too scant to support a name of its own, but it is almost certainly a new species.

The width of R.2395 suggests the neck owner was not a tiny animal. It's difficult to get a size estimate from a single neck bone, especially with cervical length varying so much taxonomically across Pterosauria, as well as ontogenetically. However, vertebral width is a little more stable with respect to overall body size, and that of R.2395 indicates an animal on the small size for an azhdarchid - an arm-wavy wingspan estimate of 3 m seems about right. When we plugged the length of R.2395 into a database of near-complete azhdarchid necks, we found the estimated CIII - CVIII length was a paltry 352–419 mm (the range depends on whether it represents a CIV or CV): 23-41% shorter than the estimated neck length of the similarly-sized Transylvanian azhdarchid Eurazhdarcho, langendorfensis and notably shorter than neck of the smaller (2.5 m wingspan) Chinese azhdarchid Zhejiangopterus linhaiensis  (measured neck length 502 mm). It seems R.2395 did indeed have a short, robust neck for an azhdarchid of its size.

The possibility that R.2395 represents a short-necked juvenile of a long-necked species was something we looked into. After all, pterosaur necks seem to increase in length disproportionately to body size, and a 3 m wingspan would leave a lot of growing room for several azhdarchid species. However, the bone texture of R.2395 is characteristically 'polished' and avascular where well preserved, which has been suggested for some pterosaurs as an indicator of skeletal maturity. This observation is bolstered by the sharply ossified anatomy of R.2395: young pterosaur skeleltons tend to have rounded, poorly defined features, but our vertebra shows a surprising amount of sharply-defined detail in its superficially simple form. We don't know how old R.2395 was when it died, but it did seem to have a very well-ossified skeleton: it was likely at, or very near to, full size, and further neck growth seems unlikely. 

What does it mean to find short necks in a clade thought to be defined by long necks? We have no idea how this plugs into azhdarchid evolution, although the retention of all azhdarchid cervical features apart from the enhanced length is of interest there. We might also conclude that suggestions azhdarchids were all anatomically similar (e.g. Witton and Naish 2008) are questionable. There are doubtless some functional and palaeoecological implications of this discovery as well - we speculate that neck mechanics and strength likely differed between long- and short-necked azhdarchids - but further remains are clearly needed to say anything substantial about specific functionality. And... in truth, I'm biting my tongue here: there's tons to say about this, but I don't want to scoop other papers which are in prep and review. Both myself and Darren Naish have been hinting at some of this short-necked azhdarchid stuff for a while now, and heavily implying that we have things to say about Haztegopteryx as well as this much smaller animal. Some readers may, therefore, be wondering why there's no discussion of giant pterosaurs here. We were both hoping that this would be out by now as well, but it turns out that this parallel-running project has been published first - that's just how these things work out sometimes! Further details on these finds is coming, with other publications in states of progress which will add to this picture. Watch this space, in other words.

To end on a less cagey note, it is worth briefly mentioning why the seemingly maximum size of R.2395 is rather interesting. It is often said that small pterosaurs are absent from the upper Cretaceous, a fact sometimes controversially attributed to competition with birds. If R.2395 really is an adult, it joins Eurazhdarcho and the 2.5 m wingspan Montanazhdarcho in suggesting that smaller pterosaurs were not absent, and perhaps even not uncommon, in the latest Cretaceous. Granted, these species are not as small as some pre-Cretaceous pterosaurs, but they are certainly size-consistent with taxa found in Lower Cretaceous Lagerstätten of China and Brazil. I do wonder if the lack of sites of exceptional preservation in the Late Cretaceous has resulted in under-sampling of smaller pterosaur species in Late Cretaceous rocks, and that drawing conclusions about the Cretaceous decline of diminutive pterosaurs, and associated competition with birds, is premature. An elephant in the room here is the scarcity of small, Late Cretaceous juvenile pterosaurs: we know they had to exist, and yet they are exceptionally rare fossils. There is clearly a preservation bias against these small individuals - can we rule out that the same bias was not acting against small adults, too? That might be nonsense, but I do wonder if  we sometimes take the - knowingly poor - fossil record of pterosaurs a bit too literally.

A quick plug for a good cause

Finally, some readers will know that I like to bang drums about Supporting Original Palaeoart, and that it's often independent artists who're providing some of the more interesting and creative palaeoart projects out there. One of these comes from David and Jennie Orr (David is perhaps best known around these parts for founding Love in the Time of Chasmosaurs, as well as a his unique, stylish artwork), who have launched an Indiegogo campaign to fund their book Mammoth is Mopey. It's a wonderfully illustrated book for younger readers showing a different prehistoric animal for each letter of the alphabet. The animals in question aren't the same tried-and-tested taxa we see in every kids book however: they're the likes of Brontomerus, Jeholopterus, Gorgonops and so on, and each is wonderfully illustrated in David's Bézier-curve-loving style. It looks great, and I've already pledged enough for two copies: one for my nephew, and another for me (hey, you're never too old to have an alphabet refresher, right?). An example image from the book is below - I can't wait to see the rest.

Artistic Ankylosaurus is artistic. From Mammoth is Mopey, which you can support here. Illustration by David Orr.

References

  • Averianov, A. O. (2010). The osteology of Azhdarcho lancicollis Nessov, 1984 (Pterosauria, Azhdarchidae) from the late Cretaceous of Uzbekistan. Proceedings of the Zoological Institute RAS, 314(3), 264-317.
  • Witton, M. P., & Naish, D. (2008). A reappraisal of azhdarchid pterosaur functional morphology and paleoecology. PLoS One, 3(5), e2271.
  • Vremir, M., Witton, M., Naish, D., Dyke, G., Brusatte, S. L., Norell, M. & Totoianu, R. 2015. A medium-sized robust-necked azhdarchid pterosaur (Pterodactyloidea: Azhdarchidae) from the Maastrichtian of Pui (Haţeg Basin, Transylvania, Romania). American Museum Novitates 3827, 1-16.