Give Plateosaurus Its Due

You could make a fascinating study (and many have) just looking at the history of which dinosaurs have held the foreground of popular culture when. The Iguanodon and Megalosaurus of the late 1800s, the Trachodon and Palaeoscincus of the earlier 1900s, the stratospheric rise of Velociraptor (sensu lato) with the release of Jurassic Park. And then there are those that never quite seem to get their dues. I've commented before on the odd relegation of Camarasaurus to the status of also-ran among famous sauropods. But perhaps the ultimate example of a dinosaur forced unfairly to the background is the should-be darling of the Late Triassic, Plateosaurus.

Plateosaurus 'engelhardti' in the Sauriermuseum at Frick, copyright Ghedoghedo.

Plateosaurus should, by all rights, be a superstar of dinosaur pop-culture. It was one of the first dinosaurs to reach massive size, extending up to nine metres in length and probably standing about as high (or slightly higher) than a tall man at the withers (Yates 2003). It is known from literally hundreds of specimens, many of them with large parts of the skeleton preserved, representing ages from juvenile to full maturity. Some of the bonebeds where it is found contain little but Plateosaurus and may have been formed in dramatic mass mortality events. Plateosaurus is easily the best known of the basal Sauropodomorpha, the 'prosauropods'. And yet, though Plateosaurus regularly appears in popular depictions, it rarely seems to make much more than a brief cameo. Why is this the dinosaur that gets no respect?

In part, it may be because it comes from a time period that gets less attention as a whole. The Triassic tends to get seen as a meer prelude to later, more 'exciting' parts of the Mesozoic. Plateosaurus itself, together with the other 'prosauropods', tends to also get overshadowed by its later, more eye-catching relatives, the sauropods. And when you get down to it, Plateosaurus may also be let down by the fact that it is perhaps the single most average dinosaur you could possibly imagine. Honestly, if you asked someone to depict a truly generic dinosaur, I don't think it would come out looking too different from Plateosaurus.

Reconstructed Plateosaurus, albeit in a now-obsolescent quadrupedal pose, copyright Elekes Andor.

All these criticisms aside, Plateosaurus is still a fascinating genus. Its remains have been found across central Europe, in Germany, Switzerland and France. The exact number of species in the genus has long been uncertain. As with other early-named dinosaur genera, 19^th Century palaeontologists named several species whose application has been subject to debate. Yates (2003) recognised two species in the genus, the earlier and smaller P. gracilis, and a larger, later species that Yates labelled P. engelhardti but which, due to various taxonomic shenanigans, should probably now be called P. trossingensis. Plateosaurus trossingensis is the better known of the two species, known from extensive bone-beds found at Trossingen and Halberstadt in Germany, and Frick in Switzerland (Lallensack et al. 2021). Some have questioned whether all these bone-beds represent a single species but Lallensack et al. found that examination of skulls from different locations failed to identify specific distinctions. Both Plateosaurus species would have been among the largest land animals of their times; even the smaller P. gracilis may have still reached lengths of five or six metres. Plateosaurus had a relatively long, narrow head though comparison of this feature with other prosauropods may be complicated by post-mortem distortion.

The life posture of Plateosaurus has historically been the subject of much dispute, whether it was bipedal, quadrupedal, or shifted freely between the two. However, recent models of the range of movement of the Plateosaurus hand and fore-arm have concluded that it was incapable of turning its hands palm-downwards, so it could not have supported itself comfortably on its fore limbs (Reiss & Mallison 2014). Obviously, the capacity for quadrupedal locomotion would evolve at some point in sauropodomorph evolution (in this day and age, I don't think anyone is proposing bipedal sauropods) but it was not before Plateosaurus.

Skeletal reconstruction of Unaysaurus talentinoi, copyright Maurissauro.

The phylogenetic relationships of Plateosaurus to other sauropods have been similarly disputed. Plateosaurus is, of course, the type genus of the family Plateosauridae but the concept of that family has varied significantly over time. For a large part of the twentieth century, 'Plateosauridae' was kind of a catch-all for all moderately large prosauropods, with Anchisauridae for the smaller species and Melanorosauridae for the giants. Redefinition of Plateosauridae to include only close relatives of Plateosaurus have significantly winnowed its contents. The current closest known relative of Plateosaurus is the recently described Issi saaneq, based on a pair of near-complete skulls from Greenland (Beccari et al. 2021). This species is close enough to Plateosaurus that its remains were previously assigned to P. englehardti. Offhand, "issi saaneq" is translated by the species' authors as "cold bone" in the local Kalaallisut language, but this looks to be another situation like "mei long" where a phrase was converted into a species name without considering that noun and descriptor order is reversed in biological names.

Other likely plateosaurids include two South American species, Unaysaurus tolentinoi and Macrocollum itaquii. The status of an Indian species Jaklapallisaurus asymmetrica is more uncertain. Beyond this, things become increasingly dodgy with little agreement over the details of prosauropod phylogeny. The overall conservative appearance of prosauropods means that phylogenetic studies are heavily reliant on fine details of the osteology that are debated between authors or not preserved in key taxa. Nevertheless, it does appear that the plateosaurids were widespread in the Norian epoch of the Triassic, and are bound to catch the attention of time travellers to the period.

REFERENCES

Beccari, V., O. Mateus, O. Wings, J. Milàn & L. B. Clemmensen. 2021. Issi saaneq gen. et sp. nov.—a new sauropodomorph dinosaur from the Late Triassic (Norian) of Jameson Land, central east Greenland. Diversity 13: 561.

Lallensack, J. N., E. M. Teschner, B. Pabst & P. M. Sander. 2021. New skulls of the basal sauropodomorph Plateosaurus trossingensis from Frick, Switzerland: is there more than one species? Acta Palaeontologica Polonica 66 (1): 1–28.
Reiss, S., & H. Mallison. 2014. Motion range of the manus of Plateosaurus engelhardti von Meyer, 1837. Palaeontologica Electronica 17 (1): 12A.

Yates, A. M. 2003. The species taxonomy of the sauropodomorph dinosaurs from the Löwenstein Formation (Norian, Late Triassic) of Germany. Palaeontology 46 (2): 317–337.

The Diversity of Neosauropods, or Pity Poor Camarasaurus

Articulated skeleton of juvenile Camarasaurus lentus in the Carnegie Museum of Natural History, photographed by Daderot.

Let me just get the obvious out of the way first: sauropods were huge. Mind-bendingly huge. In some cases, big enough to reduce a human to a sticky puddle under foot and not even break their stride. For close to 150 million years, they were the largest land animals anywhere in the world, and no other terrestrial animal at any time has come even close to rivalling their largest representatives in size. Being around for so long, it should also be no surprise that they were diverse: a large number of sauropod genera have been named, representing a wide variety of forms. Nevertheless, most people's idea of sauropods is encompassed within just four genera from the late Jurassic of North America: Diplodocus, Apatosaurus, Brachiosaurus and Camarasaurus.

These four genera all belong to the clade Neosauropoda, which has been defined as the smallest clade containing the genera Diplodocus and Saltasaurus (a late Cretaceous South American genus). Upchurch et al. (2004) diagnosed the neosauropods by a number of cranial features, together with a reduction in the fourth hind toe (part of a general trend towards toe reduction in sauropods as their feet became more columnar—see this article by Darren Naish for more on the subject). However, Upchurch et al. were writing before the recognition of the Turiasauria, a European clade that is probably the sister group of neosauropods (Royo-Torres et al. 2006), and I don't know how that clade would affect the synapomorphy distribution*. The neosauropods quickly became the dominant sauropod group after their appearance in the middle Jurassic, and the only non-neosauropod sauropods to make it into the early Cretaceous were the aforementioned turiasaurs and possibly Jobaria, an African genus that varying analyses place either just inside or just outside the Neosauropoda.

*There has been an annoying tendency in recent years for many papers featuring phylogenetic analyses to present us with the character data matrix and the final trees from the analysis, but not do anything to map character changes onto the tree. The only way to find that out would be by transcribing the entire matrix and re-running the analysis yourself.

Mounted skeleton of Amargasaurus cazaui in the Melbourne Museum.

The famed North American genera include representatives of each of the two main lineages within the Neosauropoda. Diplodocus and Apatosaurus belong the Diplodocoidea, and Brachiosaurus and Camarasaurus belong to the Macronaria. Diagnostic features of the diplodocoids according the Upchurch et al. (2004) include restriction of teeth to the front of the jaw and a subrectangular snout. This last feature reaches an extreme in the middle Cretaceous Nigersaurus, which was another of those animals that serves to remind us that, if God did indeed create all of nature, then he was taking the piss. Ludicrous diplodocoids also include the late Jurassic South American Brachytrachelopan, which took one look at the graceful, elongate necks of all the other sauropods and decided that it simply couldn't be having with all that.

Reconstruction of Saltasaurus loricatus, by Lady of Hats.

The name of the other lineage, Macronaria, means 'big nostrils', and one of the notable features of this clade is, indeed, a great expansion in the size of the nares, the opening for the nostrils in the skull (though whether the size of the nares directly corresponds to the size of the actual nostrils is, I suppose, another question). As well as Brachiosaurus and Camarasaurus, this clade includes the Titanosauria, a very successful group that included the last surviving sauropods, but whose significance was overlooked for many years because they had the poor judgement not to achieve their main diversity in North America. At least some titanosaurs, such as Saltasaurus pictured above, sported a skin reinforced by nodules of bone.

Which brings us to Camarasaurus. For some reason, of the 'Big Four' genera, this is the one that gets the least love. While the other three have each in their turn enjoyed roles as stars of stage and screen, I'm not aware of a single film in which Camarasaurus has even been given a name-drop*. In John Sibbick's illustration of Brachiosaurus and Camarasaurus together (scroll down a bit at the link) in Norman's (1985) The Illustrated Encyclopedia of Dinosaurs, Brachiosaurus marches confidently towards the front bearing a goofy leer, while Camarasaurus is forced to sulk towards the back. It's all blatantly unfair. It's not as if Camarasaurus is rare: in fact, Camarasaurus may just be the best known of all sauropods, represented in the Morrison Formation by a whole whack of remains, including what is perhaps the single most beautiful sauropod specimen ever found (the one with which I opened this post). It was no slouch in the size department, either: its maximum length of about 23 metres is similar to that of Apatosaurus, despite it having proportionally shorter appendages than the latter. Nor does it lack distinctiveness: the short, bulldog-like face of Camarasaurus instantly stands out in any neosauropod line-up. So after all this time, doesn't Camarasaurus deserve to be given the spotlight?

*Though it is a pity that the name 'Camarasaurus' won out in the priority stakes over its competitor 'Morosaurus', which to those of us from a New Zealand background suggests a dinosaur made out of chocolate.

REFERENCES

Norman, D. 1985. The Illustrated Encyclopedia of Dinosaurs. Salamander Books: London.

Royo-Torres, R., A. Cobos & L. Alcalá. 2006. A giant European dinosaur and a new sauropod clade. Science 314: 1925-1927.

Upchurch, P., P. M. Barrett & P. Dodson. 2004. Sauropoda. In: Weishampel, D. B., P. Dodson & H. Osmólska (eds) The Dinosauria, 2nd ed., pp. 259-322. University of California Press: Berkeley.

The Anchisaurs: Near-lizards or Near-sauropods?

Reconstruction of Anchisaurus polyzelus by Brian Franczak.

The 'prosauropods' are one group of dinosaurs that seemingly don't get no respect. While most other groups have their swarms of enthusiasts, there are relatively few inclined to shout their enthusiasm for non-sauropod sauropodomorphs from the roof-tops. Pop culture has a tendency to gloss them over: in the 1990s TV series Walking with Dinosaurs, for instance, their appearance was limited to a brief cameo at the end of the first episode. Despite this, they are perhaps the most 'dinosaur-y' of all dinosaurs, if comparisons with generic 'dinosaur' depictions are to be made.

The name 'Anchisauria' was introduced by Galton & Upchurch (2004) for the most exclusive clade uniting the genera Anchisaurus and Melanorosaurus. Galton & Upchurch were working under the framework that prosauropods formed a monophyletic sister group to the sauropods, but subsequent phylogenetic analyses have placed sauropods close to Melanorosaurus and hence within Anchisauria (Yates 2010; Yates et al. 2010; Pol et al. 2011). The name 'Anchisauria' can be translated as 'near lizards', but they are more properly near sauropods. Still, because this is to be a prosauropod-centred post, I will ignore the sauropods from this point on unless they insist on pushing their way in (presumably not a difficult task for a sauropod).

Reconstruction of Aardonyx celestae by Julius Csotonyi.
The two anchoring genera remain the most consistent non-sauropod members of the clade. The South American Riojasaurus, placed within Melanorosauridae by Galton & Upchurch (2004), has subsequently been placed outside Anchisauria. The Argentinian Lessemsaurus was also treated by those authors as a melanorosaurid, but may be a basal sauropod proper, while the status of the English Camelotia needs more work (Pol et al. 2011 were unable to resolve its position between Anchisauria and its close relatives). The Chinese Yunnanosaurus was placed within Anchisauria by Yates (2010), but other analyses have disagreed. Two recent genera, Aardonyx Yates et al. 2010 and Leonerasaurus Pol et al. 2011 are currently regarded as anchisaurians.

Mounted skeleton of Leonerasaurus taquetrensis, from here. Note that a large part of this skeleton is evidently reconstructed, as the described skeleton is much more fragmentary.

Anchisaurus polyzelus, from the early Jurassic of Connecticut, reached about four metres in length and is represented by the remains of a number of individuals. Some of these have been described as separate species such as Ammosaurus major and Yaleosaurus colurus, but Yates (2010) regarded them as representing a single species. This makes the '2.5 m' estimate of length given for this species by Galton & Upchurch (2004) too small, as based on a potential juvenile. Nevertheless, it was evidently such a good number that the fossil record apparently decided not to let it pass: the Argentinian anchisaur Leonerasaurus taquetrensis is about that size. The South African Aardonyx celestae was probably comparable to size to Anchisaurus* [Update: Spectacular reading fail on my part. A. celestae was about twice the size of Anchisaurus. See comments below].

*Actually, the scale bar given for the skeletal reconstruction of A. celestae by Yates et al. (2010) would seem to indicate that is must have been the smallest sauropodomorph ever. One can only assume that its size was meant to indicate 500 mm, not '500 µm' [Update: Ignore this. I am a twit. See comments below].

Reconstruction of Melanorosaurus readi, by Steveoc 86. Note that the four species illustrated in this post have been placed in order of increasing proximity to Sauropoda, as resolved by Pol et al. (2011).

Melanorosaurus readi was quite a bit larger, close to eight metres, and phylogenetic analyses have accordingly placed it as the closest relative to sauropods. Interestingly, M. readi was nevertheless quite a bit earlier than the other non-sauropod anchisaurs, being late Triassic rather than early Jurassic, and the smaller anchisaurs evidently survived the evolution of their larger cousins by some time. As well as its larger size, M. readi resembled sauropods in being an obligate quadruped. The other anchisaurs retained their plesiomorphic bipedality; the forelimbs of Aardonyx indicate that it was probably unable to adopt a comfortably quadrupedal stance (being unable to pronate its hands to a great degree, it would have had to rest them on their sides if it tried to do so). Pol et al. (2011) placed Leonerasaurus closer to the sauropods and Melanorosaurus than either Anchisaurus or Aardonyx, but the distal part of its forelimbs are unfortunately unknown.

REFERENCES

Galton, P. M., & P. Upchurch. 2004. Prosauropoda. In: Weishampel, D. B., P. Dodson & H. Osmólska (eds) The Dinosauria, 2nd ed., pp. 232-258. University of California Press.

Pol, D., A. Garrido & I. A. Cerda. 2011. A new sauropodomorph dinosaur from the Early Jurassic of Patagonia and the origin and evolution of the sauropod-type sacrum. PLoS One 6 (1): e14572.

Yates, A. M. 2010. A revision of the problematic sauropodomorph dinosaurs from Manchester, Connecticut and the status of Anchisaurus Marsh. Palaeontology 53 (4): 739-752.

Yates, A. M., M. F. Bonnan, J. Neveling, A. Chinsamy & M. G. Blackbeard. 2010. A new transitional sauropodomorph dinosaur from the Early Jurassic of South Africa and the evolution of sauropod feeding and quadrupedalism. Proceedings of the Royal Society of London Series B—Biological Sciences 277: 787-794.

The Ornithocheirids: Misunderstood Giants

The original specimen of Ornithocheirus simus, from Joseph Dinkel.

The pterosaurs of the Ornithocheiridae that lived between the Early and mid-Cretaceous were not the largest pterosaurs to ever live, but with a possible maximum known wingspan of about 7 m (Martill & Unwin 2011) they were certainly big enough (for comparison, an Australian pelican has a wingspan of about 2.5 metres). Ornithocheirids have been recorded from numerous parts of the world—Europe, South America, Africa and China—and, like the large seabirds that are perhaps their closest modern analogues (where 'closest' is a relative term), were probably found worldwide.

Reconstruction of Ornithocheirus mesembrinus, by Dmitry Bogdanov.

The 'misunderstood' in the title to this post refers specifically to the type genus, Ornithocheirus, which has suffered something of an identity crisis over the years. In the 1800s, 'Ornithocheirus' was used as a catch-all genus for almost all Cretaceous European pterosaurs, many known from only fragmentary remains. Eventually, the name came to be associated with a number of species centred around the British O. compressirostris. However, Unwin (2001) pointed out that, at its earliest publication, only one valid species was associated with Ornithocheirus, O. simus, and that species automatically becomes the type of the genus. Ornithocheirus simus is not currently regarded as congeneric with 'O.' compressirostris (and had for many years been treated under the name of Criorhynchus, e.g. Wellnhofer 1991), and so most species previously treated as Ornithocheirus are now treated as a genus Lonchodectes, and not ornithocheirids. Just to confuse matters further, however, some recent authors have continued to treat Ornithocheirus as typified by O. compressirostris, and refer to the 'Ornithocheiridae' of Unwin (2001) as the 'Anhangueridae'. On the other hand, some recent phylogenies have even suggested that Lonchodectes may itself be related to the Ornithocheiridae (e.g. Andres & Ji 2008).

Reconstruction of Coloborhynchus piscator, by Joseph Conway.

Ornithocheirus simus was originally described from a piece of the front of the rostrum found in the Cambridge Greensand of England. This piece was notably deep, and so O. simus was reconstructed as having a short, deep puffin-like skull. It wasn't until the later discovery of a more complete skull in a closely-related South American species, Ornithocheirus mesembrinus (alternatively known as Tropeognathus mesembrinus), that a more accurate reconstruction was possible: Ornithocheirus species had a long rostrum, similar to that found in related pterosaurs, but with prominent rounded dorsal and ventral crests at the distal end. Species of another ornithocheirid genus, Anhanguera (also known from England and South America), had rostral crests set further back and differently shaped. These crests most likely served some form of display function; suggestions that they may have aided in the capture of fish on the wing by easing the rostrum's passage through the water (Wellnhofer 1991) seem unlikely, as other ornithocheirid genera, such as Brasileodactylus and Barbosania, lacked rostral crests entirely (Elgin & Frey 2011). The possibility has been raised that some crested and crestless forms may represent different sexes of the same species, but unfortunately the fossil record of ornithocheirids may not be extensive enough to establish whether this is the case.

The skull of Ludodactylus piscator, via Darren Naish.

The phylogeny of pterosaurs remains a contentious issue but most studies have agreed that ornithocheirids form part of a clade that also includes the Istiodactylidae, Pteranodontidae and Nyctosaurus (though how exactly these taxa are interrelated has not been agreed upon). Ornithocheirids are distinguished from related forms by the arrangement of their teeth, with the first three pairs enlarged to form a terminal rosette. Most ornithocheirids are also distinguished from Pteranodontidae and Nyctosaurus by the absence of a crest on the back of the head. A noteworthy exception is Ludodactylus sibbicki, described by Frey et al. (2003) from a skull possessing a crest at least basally like that of Pteranodon (the skull is preserved on a slab of rock prepared commercially, and the distal portion of the crest [if it had been present] was removed when the slab was cut). However, it is worth noting that Ludodactylus has not (to my knowledge) been included in a formal phylogenetic analysis. Ludodactylus was identified as an ornithocheirid due to its tooth morphology, but the absence of teeth in Pteranodontidae and Nyctosaurus makes them incomparable in this regard. As the Istiodactylidae (with their broad, duck-like rostra) are also reasonably autapomorphic in their skull morphology, I can't help wondering whether the supposed ornithocheirid characters might be plesiomorphic for the larger pteranodontoid clade. But that, of course, is pure speculation on my part, and something only further study could establish.

REFERENCES

Andres, B., & Ji Q. 2008. A new pterosaur from the Liaoning Province of China, the phylogeny of the Pterodactyloidea, and convergence in their cervical vertebrae. Palaeontology 51 (2): 453-469.

Elgin, R. A., & E. Frey. 2011. A new ornithocheirid, Barbosania gracilirostris gen. et sp. nov. (Pterosauria, Pterodactyloidea) from the Santana Formation (Cretaceous) of NE Brazil. Swiss Journal of Palaeontology 130: 259-275.

Frey, E., D. M. Martill & M.-C. Buchy. 2003. A new crested ornithocheirid from the Lower Cretaceous of northeastern Brazil and the unusual death of an unusual pterosaur. In Evolution and Palaeobiology of Pterosaurs (E. Buffetaut & J.-M. Mazin, eds) Geological Society Special Publications 217: 55-63. The Geological Society: London.

Martill, D. M., & D. M. Unwin. 2011. The world’s largest toothed pterosaur, NHMUK R481, an incomplete rostrum of Coloborhynchus capito (Seeley, 1870) from the Cambridge Greensand of England. Cretaceous Research 34: 1-9.

Unwin, D. M. 2001. An overview of the pterosaur assemblage from the Cambridge Greensand (Cretaceous) of Eastern England. Mitt. Mus. Nat.kd. Berl., Geowiss. Reihe 4: 189-221.

Wellnhofer, P. 1991. The Illustrated Encyclopedia of Pterosaurs. Salamander Books: London (reprinted 2000, in The Illustrated Encyclopedia of Dinosaurs (D. Norman & P. Wellnhofer). Salamander Books).

A Question of Availability

About a year ago, I wrote a post discussing the potential difficulty of establishing whether a taxonomic work of restricted availability has been validly 'published'. If you head over to Mickey Mortimer's Theropod Database Blog, you'll be presented with a perfect (and perfecty 'orrible) example of just this issue, concerning the dinosaurological publications of one Stephan Pickering. Mickey has regarded the works as not validly published; Pickering himself has posted a number of comments to argue otherwise.

The arguments that have been made there about copyright (a completely separate issue from ICZN availability), private publication and peer review (in which the ICZN effectively has no interest) are irrelevant to the question of whether the works count as published for ICZN purposes. The important details in that regard are:

1. Pickering had 50 copies of each of the works professionally printed in 1995 (at least one was printed later in 1999). I have not personally seen the works in question, but the indications are that the diagnoses presented therein would satisfy ICZN requirements.

2. No printed copies of the works were deposited in institution libraries (and Pickering has objected strenuously to suggestions that he should have done so); however, copies were distributed to various recipients. At least some copies were distributed shortly after printing.

3. An excerpt or reprint of one of the works was distributed as an insert in 1996 with an issue of the popular magazine _Prehistoric Times_.

As a reminder, the ICZN requirements for a work to count as 'published' are:

8.1. Criteria to be met. A work must satisfy the following criteria:

8.1.1. it must be issued for the purpose of providing a public and permanent scientific record,

8.1.2. it must be obtainable, when first issued, free of charge or by purchase, and

8.1.3. it must have been produced in an edition containing simultaneously obtainable copies by a method that assures numerous identical and durable copies.

Do Pickering's works meet those requirements? 50 copies is low for a publication run but I don't think it can be argued to fail the requirements of 8.1.3. Publications existing in similar or lower numbers have been accepted as valid in the past. Similarly, the fact that Pickering distributed copies to various recipients suggests at least a nominal accordance with 8.1.2 (that most of these recipients, such as Michael Crichton and Stephen Spielberg, appear to have not been working palaeontologists is problematic but does not violate any explicit ICZN requirement). However, I think that a strong argument can be made that by refusing to place any copies in public depositories, Pickering has failed to meet the requirements of 8.1.1, a "public and permanent scientific record", whatever his original intentions may have been ("by their fruits you shall know them", to insert a touch of pretension). To provide a permanent scientific record, it is necessary that future researchers be able to evaluate the publication; if they are unable to gain access to a copy then they are unable to evaluate it. Unless any of the recipients of Pickering's publications take it upon themselves to secure the future availability of the works, they will end up being lost to history. As already noted by Mickey, the _Prehistoric Times_ insert, having had a much wider distribution, is a potential exception to this problem; my personal inclination would be to accept the names diagnosed therein as available though again the future availability of the work is a pending question.

Indeed, hovering over all of this is a much broader question about the publication requirements of the ICZN. Implicit in the current rules is the assumption that "once available, always available" but time, of course, is a great destroyer. In my earlier post, I discussed the rare Japanese journal Lansania, for some issues of which only a handful of (or even single) copies survive while others may have been lost entirely. There can be no doubt that the publisher of Lansania, Kyukichi Kishida, intended these issues to provide a "public and permanent scientific record"; they have evidently failed to meet that intention. What becomes of taxa whose original descriptions can no longer be evaluated?

Dinosaurs All Over the Place

Though once considered a contentious subject, most recent authors have agreed that dinosaurs represent a monophyletic group. However, a paper just released today (Parera et al., 2010) analyses the most extensive selection of reptilian taxa to date and turns the current scenario on its head, not only finding strong support for dinosaur (and particularly theropod) polyphyly but calling for significant changes to our images of Mesozoic reptiles. The failure of earlier studies such as Mortimer (2004) to recognise theropod polyphyly seems due simply to their failure to include enough taxa.

Animals traditionally regarded as 'dinosaurs' are placed by Parera et al. in three separate places in the reptile family tree. Ornithischians, sauropodomorphs and most theropods are in their usual place as sister to the clade including modern crocodiles and Parera et al. restrict the name 'Dinosauria' to this clade. However, dromaeosaurids and oviraptorosaurs clade with birds separately from the main dinosaur clade. Instead, this new clade (which Parera et al. simply refer to as 'Aves') appears as sister to the Triassic rhynchosaurs. While, to the best of my knowledge, such an arrangement has not been suggested before, it does not seem entirely incredible - for a start, both birds and rhynchosaurs have well-developed beaks.

The most surprising result of all, perhaps, is that compsognathids and therizinosaurs are also not dinosaurs. Instead, they form part of a large clade also including ichthyosaurs, plesiosaurs, pterosaurs and lepidosaurs for which Parera et al. resurrect the long-disused name Gryphi. This further corroborates the recent demonstration by Lingham-Soliar et al. (2007) that the supposed 'protofeathers' found in the compsognathid Sinosauropteryx are in fact collagen fibres from a thick insulating dermal layer. The supposed 'melanosomes' described from Sinosauropteryx by Zhang et al. (2010), cited as further evidence for a 'protofeather' interpretation of the fibres, are shown by Parera et al. (2010) to instead represent the eggs of skin-burrowing parasites that afflicted this poor individual.

The additional presence of preserved dermal fibres in ichthyosaurs and pterosaurs suggests that such a dermal layer was an ancestral feature of the Gryphi. The clade appears to have been ancestrally aquatic - aquatic lifestyles have been proposed previously for compsognathids by Bidar et al. (1972) and for pterosaurs by Wagler (1830), and Parera et al. further demonstrate the accuracy of these interpretations. The ancestors of lepidosaurs, found by Parera et al. to be sister to pterosaurs, must have at some point left the aquatic habitat and consequently lost their insulating dermal layer. However, perhaps the aquatic iguana of the Galapagos Islands represents the sole remnant of the Gryphi's long marine history?

REFERENCES

Bidar, A., L. Demay & G. Thomel. 1972. Compsognathus corallestris, nouvelle espèce de dinosaurien theropode du Portlandien de Canjuers (Sud-est de la France). Annu. Mus. Hist. Nat., Nice 1: 1–34.

Lingham-Soliar, T., A. Feduccia & X. Wang. 2007. A new Chinese specimen indicates that ‘protofeathers’ in the Early Cretaceous theropod dinosaur Sinosauropteryx are degraded collagen fibres. Proceedings of the Royal Society of London Series B - Biological Sciences 274 (1620): 1823-1829.

Mortimer, M. D. 2004. The phylogeny of Neotetanurae (Theropoda, Dinosauria). Annals of the Museum of Natural History at the University of Ohio at
Springfield 2004: 1-369.

Parera, A. S., H. M. Whio & T. V. Pari. 2010. A comprehensive analysis of reptile phylogeny demonstrates theropod polyphyly, with notes on the life habits of compsognathids and pterosaurs. Transactions of the Royal Society of Hull 238 (1): 4-136.

Wagler, J. G. 1830. Natürliches System der Amphibien. München, Stuttgart, Tübingen.

Zhang, F., S. L. Kearns, P. J. Orr, M. J. Benton, Z. Zhou, D. Johnson, X. Xu & X. Wang. 2010. Fossilized melanosomes and the colour of Cretaceous dinosaurs and birds. Nature 463: 1075-1078.

Ceratopsids: A Cretaceous Flash in the Pan

Leptoceratops, one of the latest-surviving ceratopsians. Reconstruction from here.

After the previous post on ceratopsians, Zach Miller asked if I could follow up my basal-ceratopsian-focused post with one on the more famous ceratopsids, which for various reasons, most significantly time, I had rather neglected.

Sorry, Zach - this is not that post.

But what I thought I would elaborate on was something I referred to offhand in that post about the significance of the basal ceratopsians compared to the ceratopsids proper. I mentioned that the small bipedal ceratopsians, despite their relative obscurity, actually persisted in North America for just as long as the giant ceratopsids, and were with them 'til the end. I would like to add to this that as surprising as it may sound to any readers who are only familiar with popular presentations of evolution and their tragic tendency to fall into the "March of Evolution" trap, this actually wasn't much of an achievement. For even though ceratopsids are one of the iconic dinosaur groups, instantly recognisable by 95% of the developed world's population, they weren't actually around for very long.

Most of you will have probably heard of the Triassic, Jurassic and Cretaceous periods that together make up the Mesozoic era of earth's history. While these periods are quite sufficient for broad generalisations about the history of life, palaeontologists generally find that they need finer-scale divisions to refer to more specific time periods. I recommend going to Palaeos.com if you want to see the subdivisions for the Jurassic and Cretaceous, because I'm going to have to refer to a few of them in the course of this post. I know I'll be checking back there regularly as I write this post, because personally I can never keep track of them all.


Yinlong downsi, the earliest known ceratopsian. Reconstruction by Andrey Atuchin.

I mentioned in the previous post that the earliest ceratopsians are known from the Late Jurassic. Specifically, Yinlong downsi comes from the Oxfordian, which started about 161 mya (million years ago). (Taxon ages for this post have been taken from Justin Tweet's Thescelosaurus! website.) In the rough grade system I used in the previous post, Yinlong would be a psittacosaur-grade ceratopsian*, but phylogenetically speaking it is the sister taxon to later ceratopsians. The earliest and most basal known protoceratopoid-grade ceratopsian, Liaoceratops yanzigouensis, comes from early in the Cretaceous, some time between the Valanginian (starting about 140 mya) and the early Barremian (130 mya). The earliest known Ceratopsidae, in contrast, didn't crash the party until the mid-Campanian (perhaps about 78 mya). Ceratopsians had been around for about 80 million years already by the time the ceratopsids appeared. Or to put it another way, less time separates us from the latest ceratopsids than separates the ceratopsids from the earliest ceratopsians! With their extinction at the end of the Cretaceous, about 65 million years ago, the Ceratopsidae are only known to have been around for about 15 million years - an impressively long time by human standards, but really not so very impressive when compared to the nearly 100 million years of ceratopsian history, or the more than 180 million years the Mesozoic lasted for in total.

*You may be wondering how the psittacosaur-grade ceratopsians fared in terms of longevity. Psittacosaurus is the latest well-established psittacosaur, and seems to have survived until about the end of the Early Cretaceous, about 100 mya. However, the analysis of Butler et al. (2008) suggests, albeit with rather low support, that the poorly-known (yet ambitiously-named) Micropachycephalosaurus hongtuyanensis might be a very basal ceratopsian. Despite this basal position, Micropachycephalosaurus actually dates from the Maastrichtian, the very last part of the Cretaceous. If Micropachycephalosaurus is indeed a ceratopsian (a proposition that should be taken very cautiously), then psittacosaur-grade ceratopsians survived at least relictually for almost the entirety of ceratopsian history.

True, the ceratopsids did attempt to cover up for lost time through rapid speciation, so that more ceratopsid taxa have been described from that last fifteen million years than all the non-ceratopsid ceratopsians over 100 million years, but this is like the rapid propagation of any fad - the flashy new designs may temporarily overshadow the old classics in the public eye, but the classics are still very much there.

REFERENCES

Butler, R. J., P. Upchurch & D. B. Norman. 2008. The phylogeny of the ornithischian dinosaurs. Journal of Systematic Palaeontology 6 (1): 1-40.

Big Horned Lizards

The ceratopsid Einiosaurus. Reconstruction from here.

Sometimes it's nice to write a post on something everyone's heard of, and I'm pretty sure almost everyone will have heard of this week's highlight taxon - the Ceratopsia. In one of my earliest posts on the Catalogue of Organisms, I nominated Triceratops horridus as one of the greatest of dinosaurs, rivalled as it is only by Tyrannosaurus rex and Apatosaurus ajax as an icon of all things dinosaur. And before anyone (I'm looking at you, Mike) weighs in to complain about the title to this post, I know that dinosaurs aren't lizards, the title was chosen in a spirit of tongue-poking and ribbing.

Ceratopsia is a very well-supported clade of dinosaurs. Not least of the characters uniting its members is the presence of the rostral bone - a small toothless bone at the tip of the upper jaw that is unknown from any other dinosaur and demonstrates the presence of a beak in the ceratopsians. Some sources have pointed out that the name Ceratopsia is actually mis-derived and argued for the name Ceratopia instead, as well as Ceratopidae and Protoceratopidae instead of the more commonly used Ceratopsidae and Protoceratopsidae, but in this case a long history of usage has won out over strict linguistic accuracy*. Most authors accept that ceratopsians form a clade called Marginocephalia with the Pachycephalosauria, but it is worth pointing out that while it is the best-supported hypothesis to date, the support for Marginocephalia is not overwhelming and the question is worth former investigation. While Sereno (1986) placed the Marginocephalia outside the ornithopods, a recent analysis by Butler et al. (2008) produced a phylogeny that nested Marginocephalia within a number of taxa that had been regarded in the past as ornithopods, suggesting that marginocephalians are derived from within the "hypsilophodontid" grade of dinosaurs. Interestingly enough, this is actually more congruent with older pre-cladistic theories of dinosaur relationships that had implicitly derived both ceratopsians and pachycephalosaurs from ornithopod ancestors. It also reduces the significant ghost lineage that Sereno's topology suggested for marginocephalians.

*Names ending in "-ops" have actually got a long history of being pains in the neck for zoological nomenclature. The ending "-ops" can be derived from the Greek word for "face", which is masculine, or for "appearance", which is feminine. Because many an author has ended a genus name in "-ops" without indicating which ending was intended, it is unclear for many such names whether they were meant to be masculine or feminine, a significant issue because it affects the form of any associated species names. It is because of this confusion that the ICZN has declared that all names ending in "-ops" are to be treated as masculine, regardless of derivation.


Reconstruction of Psittacosaurus by Pavel Riha.

The earliest known Ceratopsia date from the Late Jurassic. Ceratopsians can be divided into three distinct grades that have been classified as separate families in the past, but of which two are paraphyletic. These grades are the psittacosaurs, protoceratopoids and Ceratopsidae. The Ceratopsidae are the most familiar of the ceratopsians, and include the large horned quadrupedal forms. This group includes some of the first dinosaurs described from North America, albeit many from fragmentary remains which tragically means that such fantastic names as Agathaumus, Dysganus and (my personal favourite) Polyonax mortuarius, the "dead master of many", have been resigned to the oblivion of nomen dubium status. I'm going to leave the Ceratopsidae for some other time and introduce the more basal ceratopsians.

Psittacosaurs are the basalmost group of ceratopsians - small and at least facultatively bipedal, they look not too different from a basal ornithopod and were classified as such when first described (Osborn, 1924), though a connection between psittacosaurs and ceratopsians was also recognised quite early on (though again, in those pre-Hennigian days the separation of psittacosaurs from ceratopsians as part of a paraphyletic Ornithopoda was not really seen as a problem). The majority of psittacosaurs have been included in the genus Psittacosaurus - in fact, with over ten described species (though not all of these may be valid), Psittacosaurus provides a welcome exception to the tendency of dinosaur systematists to keep their genera as small as possible (while sixteen species have been referred to Triceratops, almost all of these are invalid - Ostrom & Wellnhofer, 1990). In recent years, a few other "psittacosaur-grade" genera have been described, such as Chaoyangsaurus and Yinlong. The frill formed by the extension of the bones of the back of the skull that is so characteristic of other ceratopsians is absent from psittacosaurs, though a slight rearward curve of the squamosal (as well as the short snout) does help give the skull of Psittacosaurus a distinctly boxy appearance. Psittacosaurus is actually one of the best-known of all dinosaurs, with literally hundreds of known specimens of all different ages. One specimen is known that preserves a row of long tubular bristles running down the tail of unknown function, probably display*.

*With the admission that "display" is all too often something of a cop-out explanation for unusual structures.


Mounted skeleton of Archaeoceratops oshimai, one of the basalmost protoceratopoids. Photo from here.

I'm using the name "protoceratopoids" (a term plucked more or less out of thin air) to refer to the taxa previously included in the Protoceratopsidae, a taxon now well established to be paraphyletic with regards to the Ceratopsidae (the two groups together forming the Neoceratopsia). Taxonomic concepts in this grade are currently a little unstable - there may be a more restricted Protoceratopsidae formed from taxa forming a monophyletic group with Protoceratops, while other protoceratopoids are parcelled off into families such as Leptoceratopsidae. In protoceratopoids we see the development of the frill characteristic of Neoceratopsia, albeit still fairly small in many species. Most protoceratopoids lack the horns of ceratopsids, and were also much smaller than the ceratopsids. Some protoceratopoids such as Leptoceratops (which if the run of available reconstructions is to be believed existed for no other purpose than to provide food for larger, meaner-looking reptiles) probably remained bipedal, but other lines became larger, heavier and eventually quadrupedal. Analyses differ as to how many times quadrupedality evolved in ceratopsians (You & Dodson, 2004). One very basal protoceratopoid, Archaeoceratops oshimai, was a very gracile impish-looking little form that actually looks better adapted as a runner than does Psittacosaurus. Though often dismissed as basal forms, the bipedal ceratopsians were to survive for just as long as the quadrupedal forms, and Leptoceratops was actually a contemporary of Triceratops, one of the latest Ceratopsidae.

Mention should also be made of the role of Protoceratops as an accessory to one of the biggest frame-jobs in the history of palaeontology. The first known specimen of the theropod Oviraptor was discovered overlying a nest of eggs that were identified as belonging to Protoceratops. It was this that gave Oviraptor its name ("egg thief"), and for many years Oviraptor was reconstructed mercilessly plundering protoceratopsid nests. It wasn't until fairly recently that it was discovered that the "Protoceratops" eggs didn't belong to that taxon at all, but were in fact Oviraptor eggs, and far from stealing them, the much-maligned Oviraptor had probably been a diligent mother incubating them! I did attempt to speak to Protoceratops about its role in this shameful affair, but it refused to comment on grounds of being extinct.

The majority of known basal ceratopsians - all psittacosaurs and most protoceratopoids - come from Asia, particularly northern Asia, and this is universally accepted to be the place of origin of this clade. The Ceratopsidae, in contrast, is only known from North America, as is the sister taxon to Ceratopsidae, Zuniceratops. It appears likely that their ancestors dispersed to North America from Asia before giving rise to the Ceratopsidae. Again, how many times this dispersal occurred is uncertain - members of the Leptoceratopsidae were also found in North America. The analysis of Xu et al. (2002) placed Leptoceratopsidae in a very basal position distant from Ceratopsidae, while that of You & Dodson (2004) found them as sister taxa (though I should point out that the latter analysis included significantly fewer taxa than the former). Two records of Ceratopsia from outside Laurasia are rather problematic. The South American Notoceratops, based on a single jawbone, was originally described as a ceratopsian but is suspected to have been a hadrosaur - unfortunately, this question will probably never be fully resolved because the type specimen has gone AWOL. The Australian Serendipaceratops is supposed to be very similar to Leptoceratops, but is known only from a single ulna.

REFERENCES

Butler, R. J., P. Upchurch & D. B. Norman. 2008. The phylogeny of the ornithischian dinosaurs. Journal of Systematic Palaeontology 6 (1): 1-40.

Osborn, H. F. 1924. Psittacosaurus and Protiguanodon: two Lower Cretaceous iguanodonts from Mongolia. American Museum Novitates 127: 1-16.

Ostrom, J. H., & P. Wellnhofer. 1990. Triceratops: an example of flawed systematics. In Dinosaur Systematics: Approaches and Perspectives (K. Carpenter & P. J. Currie, eds.) pp. 245-254. Cambridge University Press.

Sereno, P. C. 1986. Phylogeny of the bird-hipped dinosaurs (Order Ornithischia). National Geographic Research 2: 234–256.

Xu, X., P. J. Makovicky, X.-L. Wang, M. A. Norell & H.-L. You. 2002. A ceratopsian dinosaur from China and the early evolution of Ceratopsia. Nature 416: 314-317.

You H. & P. Dodson. 2004. Basal Ceratopsia. In The Dinosauria, 2nd ed. (D. B. Weishampel, P. Dodson & H. Osmólska, eds.) pp. 478-493. University of California Press.

Top Ten Follow-up

Paul W. complained that ten was too few for the previous post, so I'll add the runners-up to bring the total to twenty-four. They were:

Brachytrachelopan mesai: The short-necked sauropod of South America - a smashing little stunner that surprised us all. You've got to love the name, too.

Carnotaurus sastrei: Another real oddball. Combine the boxy horned skull with the ridiculously tiny forearms (it makes Tyrannosaurus look like a gorilla) and it's a mystery what this creature was doing for a living.

Diplodocus carnegii: Another classic sauropod. I think my scoring system favoured sauropods a little - they pretty much all scored highly in the 'impressiveness' box, but how are you going to call these giants anything else?

Microraptor gui: The 'four-winged' miniature marvel that inspired much passionate debate on its flying abilities (also, the first non-avian dinosaur to be claimed as a flier). Though there is still no agreement about whether the long feathers preserved on the legs formed functional wings, the evolution of flight in dinosaurs will never be viewed so simplistically again.

Opisthocoelicaudia skarzynskii: My favourite sauropod as a kid. Let's have that name again - Opisthocoelicaudia. Just kind of rolls off the tongue, doesn't it? Even better than Parasaurolophus.

Plateosaurus longiceps: Prosauropods are kind of the poor relative in the dinosaur family - never given much time, and about the only major group to not even have a cameo on a Jurassic Park movie. That said, Plateosaurus is the archetypal prosauropod (by definition, as it happens).

Stegosaurus ungulatus: Everyone knows this critter. As David Marjanovic has pointed out, the original thagomiser.

Turiasaurus riodevensis: Europe's largest known dinosaur, and type of a previously unknown group of sauropods. There's something vaguely funny about a previously unseen sauropod.

Centrosaurus apertus: It was either this one or Styracosaurus albertensis. Like Triceratops, but funkier.

Coelophysis bauri: When one is used to thinking of dinosaur finds as a few disarticulated remains, the Ghost Ranch deposit with more individuals of Coelophysis than can be counted are just stunning.

Herrerasaurus ischigualastensis: The prototype of later theropods. Herrerasaurus may no longer be the basalmost known dinosaur - recent workers favour a position very basal saurischian, plus there's always Eoraptor to trump it - but I still have a soft spot for the big lunk.

Pachyrhinosaurus canadensis: The ceratopsian that ditched the ceras, favouring a big ol' ugly boss instead. Still not to be messed with.

Psittacosaurus mongoliensis: I used this species as stand-in for the whole seemingly endless run of Psittacosaurus species. Every time I turn around there seems to be another one. They've been found huddled together in nests, they've been found with apparent long quills on the tail, they've been found halfway down a mammalian gullet. You can't escape them.

The Top Ten Dinosaurs - Triceratops beats Tyrannosaurus

Time it took me to do something hopelessly populist in order to try and draw more attention to the Catalogue of Organisms: 24 days. What can I do that's guaranteed to work up some steam?

In that light, I here present a list of my top ten dinosaurs, inspired by Don Robertson's Top 50 Birds (actually top eleven - some tied). Candidates for the list were rated completely subjectively on five factors: (1) Impressiveness - if I were to come across one of these critters, would the appropriate response be 'wow' or 'meh'? (2) Knowledge - how extensively the species has been studied and how well it is known. (3) History and Significance - if the discovery of this species had much significance, especially at the time it was discovered. This is also the category that was influenced by how much attention this species has received from the general public over time. (4) Controversy - has the species has inspired much debate over the years? (5) Special Factors - like Don Robertson did with his bird list, I also scored for an entirely subjective character of any special significance the species has that isn't really covered by the previous four categories. This category also reflected my own personal feelings about the animal in question (and whether or not I wanted it to win).

The list:

6th Equal:
Deinonychus antirrhopus: The little evil-looking buggers with the massive sickle claws on the feet. The description of Deinonychus has been directly credited with inspiring the renaissance in views on dinosaur metabolism. Older reconstructions of sluggish, low energy dinosaurs just made no sense when applied to this obvious speedster.

Euoplocephalus tutus: Everyone's favourite living tank. What more can you say about a creature so heavily armoured that even its eyelids would have clanged when it blinked? Not to mention the thagomiser at the end of the tail.*

*I'm not sure if the term thagomiser has ever been used formally, but it has a reasonable amount of informal currency as a term for an offensive structure at the end of a tail (like the ankylosaurid club, or the stegosaurid spike array). I believe it derives from a Far Side cartoon about cavemen, where it is named after the late Thag.

Falcarius utahensis: Apparently known from more specimens than you can shake a thagomiser at, this discovery of a couple of years ago represents the basalmost member of the therizinosaurs, gigantic (probably) herbivorous theropods with ridiculously oversized claws. Falcarius was a nice find because it perfectly slotted into the gap between derived therizinosaurs and their supposed relatives.

Iguanodon bernissartensis: The classic European dinosaur, one of the earliest discovered and possibly the earliest known from significant remains (this is the best known of the multiple Iguanodon species - while Iguanodon was one of the original three dinosaurs, the specific species involved there was Iguanodon anglicus, which is no longer regarded as identifiable).

Mononykus olecranus: Arguably the wierdest of all dinosaurs, with still no real idea about its lifestyle. A small bird-like theropod, Mononykus has greatly shortened yet very stout single-clawed forelimbs. The structure of the forelimbs appears suited for digging, yet the light cursorial form of the the rest of the body doesn't appear suitable for this.

Tyrannosaurus rex: Undoubtedly the best known of all dinosaurs. To be honest, I was kind of hoping old Tyrannosaurus would fall off the list - I think she's hogged the limelight for long enough. If you want to know more, a quick Google search will tell you more than you ever wanted to know - just pay no attention to the bit about coconuts.

2nd Equal:
Archaeopteryx lithographica: The Urvogel, the Missing Link (though obviously it's not missing anymore, is it?). Archaeopteryx was the original inspiration in recognising the connection between Cretaceous dinosaurs and modern birds. While later discoveries mean that Archie (as he is known to his friends) is now but one of many fossils demonstrating this link, he still retains one of the best represented by specimens, and his historical significance will never be lost.

Oviraptor philoceratops: The name means 'egg thief and lover of ceratopsians' - when the original specimen was found it was lying on a nest of eggs that were then believed to belong to Protoceratops, and it was thought to have died while attempting to predate them. It has since been found that the eggs belonged to Oviraptor itself, and not only was it not eating them, but it would have been sitting astride them bird-style to keep them warm - history's ugliest broody chicken. The true diet of the strange-looking, beaky Oviraptor is a cause of great debate.

Triceratops horridus: Another classic. There are few people who would not recognise this beast with its broad frill and intimidating spiky bits. You know you love him, just don't stick your hand near his mouth if you want to keep it.

And my choice for the Greatest Dinosaur Ever:

Brachiosaurus brancai (or Giraffatitan brancai, depending on whom you ask): What can one say when faced with a giant sauropod except WOW! There may be bigger sauropods than Giraffatitan, there may be prettier, but this is still the classic giant and one of the best-known. Besides, the difference between unbelievably mind-blowingly HUGE and stupidly unbelieveably mind-blowingly HUGE is not that great when you consider that both can reduce you to a small greasy puddle underfoot and barely even break their stride.