Posts Tagged 'taxonomy'

Noripterus returns – sorting out some pterosaur taxonomy

New reconstruction of Noripterus by Rebecca Gelerenter. This is a composite based on all the material we have from various specimens (known material is in white).

New reconstruction of Noripterus by Rebecca Gelerenter. This is a composite based on all the material we have from various specimens (known material is in white).

Immediately after the Munich pterosaur meeting ended in 2007, I moved to Beijing to take up a postdoctoral position at the IVPP. Perhaps the first bit of mail I has there was from the now late Wann Langston thanking me for setting up the Munich Flugsaurier (which he had attended) and sending me a photocopy of his notes and some old photographs he’d taken on a trip to China back in the 80s. This was of a superbly preserved pterosaur hindlimb, and one he wanted to know more about but which had since not been seen by any researcher he knew, or been in the literature.

This was a specimen of Noripterus, a small dsungaripterid from China found by, and then named by, C.C. Young back in 1973. The original description of this was both a bit sparsely described, and in Chinese which is a shame as Young mentions a number of specimens, and illustrates or measures only part of some of them. I asked around the curators at the IVPP but no one knew the location of the material and it was suggested to have been borrowed and not returned.

Fast forward a couple of years and while Paul Barrett was visiting the IVPP he had been directed by a colleague to a little used set of cabinets in the collection, where apparently some mislaid dinosaur material was residing. I happened to be looking over a specimen in the collections at the time so inevitably was keen to see what might turn up. On opening the case, Paul found his specimens, but one thing I spotted was immediately recognisable from Wann’s photos – the lost Noripterus foot. Accompanying it was quite a lot of other pterosaur specimens with similar specimen numbers – Noripterus was back.

Since then I’ve been working on and off on a number of projects on these specimens (hampered by my no longer being in China) and the first is finally out as part of the volume from the back of the 2015 Flugsaurier meeting in Portsmouth. A more full description is in the work but this is the first and important step because the taxonomy of the Asian dsungaripterids has been an issue that’s been problematic for quite a while, and much of it hinges on Noripterus.

Things have been difficult to resolve because as noted, the original description doesn’t give that much information on the material (and less if you don’t speak Chinese – I am indebted to my collaborators here as you may imagine). If you want to sort out how various other species and genera relate to it (or not) you really need to know what it actually is anatomically and taxonomically, and so having the specimens available means we can make some significant updates to Young’s identification and how other more recent discoveries might relate to it.

First off the bad news – what was originally designated as the holotype is mostly still missing. Only a fragment of the jaws remain and they are not in great condition. Still, they are diagnostic which helps us to define Noripterus better. On the good news side of things, there is a lot of nice associated material as Young collected multiple specimens from just a few sites and despite the lack of overlap in some areas, there’s some good reasons to think they are all the same thing. Noripterus is known from several superbly preserved specimens including a near complete set of limbs and girdles preserved in 3D. There will be more on this in the future, but obviously it’s very useful material to have.

A superb set of limbs from one specimen of Noripterus

A superb set of limbs from one specimen of Noripterus

Working out quite which specimen was which however actually took quite some time and detective work. The field numbers on the bones and the specimen numbers on the boxes they were in, did not always line up with the identities given in Young’s paper (either illustrations or the few measurements).  Eventually though we got this sorted out and so one part of the paper gives some new specimen numbers and sorts out the various specimens into their (hopefully) correct sets.

The main issue though is the taxonomy itself of these animals. Noripterus was only the second dsungaripterid identified (you may not be shocked to learn Dsungaripterus was the first) and so it might not be a surprise that it’s considered a valid taxon. It is rather smaller than it’s more famous relative, and has straight rather than curved jaws, as well as rather more narrow teeth. That’s the easy bit.

Then we have ‘Phobetor’ from Mongolia, named from some very fragmentary material that has never been described in detail. More recently there’s more Mongolian stuff from 2009 called the ‘Tatal pterosaur’ that was used to link together that material, ‘Phobetor’ and Noripterus all under the latter name. On top of that we have the Chinese genus Longchognathosaurus known from little more than a few bits. Clearly lining these up and working out if there were one, two or three genera was going to prove difficult while 2 of these 4 sets of specimens were fragmentary and most had never been described or illustrated properly. In this context, getting to see Noripterus was clearly very useful in terms of making some meaningful comparisons of key characters.

So, what did we find? Well, actually the Tatal material and the original ‘Phobetor’ are very similar based on the limited descriptions of each suggesting they are the same taxon. However, they have some consistent differences with the Noripterus material which suggests they represent a valid and separate genus and should not be synonymised with it. That also means that ‘Phobetor’ is still lacking a name (it’s preoccupied by a fish). Finally, Longchognathosaurus has at least a couple of the supposedly diagnostic characters present in the holotype of Noripterus and while it’s not necessarily the same thing, it is hard to justify it being unique at this point.

Clearly all of this is provisional, and lacking a good skull for Noripterus (or at least the rest of the holotype) would really help firm all of this up, not least when the Tatal specimens include a good skull and Longchognathosaurus is based mostly from cranial material. In fact given how much good Noripterus material there is, it is an oddity that there’s so little of the head, but hopefully more will turn up. In the meantime, this should help move things forwards and provide a better basis for sorting out these taxa and some curiosities about their relationships to other pterosaurs (in particular Germanodactylus which may or may not be an early dsungaripterid). Now we just need some more detailed descriptions of all the other Asian dsungaripterids (and yes, more on Noripterus too) but this is a start.

 

TLDR: We have a good amount of Noripterus back. ‘Phobetor’ is probably separate and valid and the same thing as the ‘Tatal pterosaur’ material. Longchognathosaurus is probably not valid.

 

Pterosaur ontogeny

 Not too long ago, Matt Wedel had an SV-POW! post that talked about ways of diagnosing an adult vs non-adult sauropod. Inspired by this and the fact that I have recently been playing around with issues of ontogeny in pterosaurs, I decided to write something similar for the non-avian Mesozoic fliers. If you have a pterosaur specimen in front of you, just how do you know if it’s an adult or not?

Obviously there are some general indicators that are pretty good for vertebrates as a whole that will get you quite a long way (even if this is a new species). Size is obviously rarely a great indicator, but if you have a pterodactyloid with a 20 cm wingspan then it’s going to be a juvenile, and likewise if you have a rhamphorhynchoid coming in close to the 2 m mark it’s very unlikely to be anything but a big adult. Young animals (and especially very young animals) tend to have big heads compared to their body and especially very big eyes compared to the size of the head. A bunch of fusions are absent in young pterosaurs that are present in adults too, just as you’d expect for most animals. The sutures between the centrum and neural arch of the vertebrae will be open in juveniles and closed in adults, and similarly the elements of the pelvis and sacrum, and the scapula and coracoid will be separate in young animals and fused together in adults.

Pterosaurs also have some characters of ontogenetic change that are rather more peculiar to them than vertebrates in general. Very young pterosaurs also tend to have a very grainy texture to the surfaces of their longbones, despite the fact that even embryonic pterosaurs have a pretty ossified set of bones (unlike many young animals). Smaller pterosaurs also tend to have various parts of the skeleton being less ossified and rather amorphous compared to those of adults. The tarsals are often not well ossified and can be missing (well don’t preserve) and if present may be very simple shapes. The carpals tend to look more ‘blobby’ and lack the detailed morphology seen in adults and will be separated into multiple elements whereas in adults the wrist will primarily be formed of just two massive elements (plus the pteroid). Finally, while obviously you would expect skulls to fuse up during ontogeny, pterosaurs do tend to take it one step further than most. Rather like birds, in adult pterosaurs the sutures all but disappear, or even go entirely, such that the skull looks like a single smooth piece of bone. Also as in some birds, bigger pterodactyloids have a notarium and this only fuses up and fully develops in adults. Similar to the point above about absolute size, the presence and development of some form of head crest is indicative, but not a great indicator of age. Yes a massive and elaborate crest in an animal is indicative that it’s an adult, but there could be a fairly well developed crest in an animal that is close to becoming and adult and of course there are taxa without crests and in at least once case it appears that females don’t have crests.

As in mammals, but unlike dinosaurs and birds, pterosaur also have epiphyses. The growing plates at the ends of the long bones physically separate the main shaft of the bone from the proximal and distal ends, so things like the femur can appear to be in three pieces. Obviously as growth slows towards maturity these epiphyses slowly disappear as they fuse into the single element that you would expect to see.

So in short, something that is small, with grainy textured bones, a big head, with big eyes, unossified tarsals, amorphous carpals, no crest, clear sutures in the skull, no notarium, and separated scapulocoracids, pelvis, epiphyses and neurocentral sutures is going to be a young juvenile. And the close these various features get to the opposite condition the closer the animal is likely to be to adulthood.

As ever with such things these are not absolutes, but merely guides. Good guides, certainly – you simply won’t see a notarium in a very young pterosaur, or open neurocentral arches in a big, old adult. However, in terms of determining more subtle difference in age it will be tricky – one animal may have fused up the notarium, but may have incompletely ossified tarsals and another could have the reverse. Although at least some characters do seem to have a bit of a pattern (the scapulocoracoid seems to fuse pretty early in most things) a general lack of numerous specimens of different ages makes it hard to do any more detailed analysis. Still, in terms of gross age (hatchling – young – adolescent – adult) even for a specimen of a previously unknown species with no obvious close relatives, it should be relatively easy to determine the approximate age of the animal.

Butterflies & moths

Another little display from the Carnegie I’ve had sat in my files for too long. OK so there’s nothing here that’s linked to archosaurs, or even evolution in general. But what it does do is address just the kind of question that often bugs people. I think a very big proportion of the public would recognise that moths and butterflies are close relatives and that they are different, but aside from the diurnal / nocturnal split and the fact that butterflies tend to be more colourful, they would probably struggle to say how you could tell them apart, or for that matter what linked them together.

My experiences with Ask A Biologist suggest this kind of thing is really common. People have bits of knowledge and part of the full picture, but don’t realise they have only part of the story and even if they did, don’t know how to go about filling in the gaps or putting their knowledge into context. In the case of AAB, someone has realised that don’t know the full picture, or has had their interest piqued by some incident.

In the case it’s actively prompting people – it’s easy to imagine someone looking at this and thinking “Oh yeah, what *is* the difference?”. The headline is a nice attention grabber and it’ll get people to read the short captions below and, hopefully, get them thinking a little more about taxonomy and diversity (if not in those terms) and the world around them. In short, neat idea, well done. I can easily see this being a nice series too – a line of panels of ‘What’s the difference between a shark and a fish?’ or frogs vs toads, newts vs salamanders, goats vs sheep and the like.

What is also nice about this is how much that is conveyed in such a small amount of space and few words. Maximum communication but without filling the place or making people struggle through dense text to get the message across, and all the time filling in other gaps in their knowledge with little extras like the addition of skippers or the relative numbers of species. Great stuff.

Lego

A link to this went up on Facebook the other day (I can’t remember who it was, sorry about that). Those unable to click will want to know that it goes to the Lego website and their yet-to-be-released line of dinosaur based toys. I’m all for Lego and like most people had plenty of it when I was younger and used it a lot, in fact it seems to be universally popular and that bring me to this post.

Eagle-eyed / nerdy / geeky / pedantic / whatever (delete as appropriate) will spot that they (shock, horror) haven’t italicised the taxonomic names properly. For all my pendantry (it comes with the  bundle pack of cynicism when you start a PhD) I’d normally write this off. After all, it’s all too commonly done even by people who should know better, so a toy company can easily be excused.

However, what I see here is an opportunity. Lego is enjoyed by millions of children, and I can’t see Lego dinosaurs being unpopular this coming year. Kids love learning and generally do spot and retain details. Lego have always struck me a rather ethical company who know full well their responsibilities to children and learning as well as playing. Given that the line has not actually been released yet, I wonder if a polite letter from a concerned group of palaeontologists might get them to change this? Sure, it’s a very minor issue, but for them it’s not exactly a redesign of the packaging or toys, and what it will do is reach a huge and engaged audience.

So I don’t think there’s any harm in at a least asking, but I’d be intrigued to see what others think. If I put something together, would any of you lot be interested in adding your name as a ‘we the undersigned’?

 

“Pterasaur Dinosaur Teeth”

Such was the headline of some teeth for sale I came across on a website the other day. While you can understand that a commercial site might not differentiate a pterosaur from a dinosaur, or would want to assocaite them together as the average punter may not know what a pterosaur is, the spelling is still not a great start. The description of the teeth though is truly bizarre:

“Genuine Pterasaur dinosaur tooth. These teeth are 2-4cm and are C-grade, economy price. They are of the dinosaur Rebbachisaurus, and Cretaceous age. They come from Morocco.”

I am *most* interested to learn that sauropods could fly, or that pterosaurs were 20 ton terrestrial grazers. Hardly fills you with confidence about their ability to identify other bones does it? (It was incidentally, as far as I could tell, a pterosaur tooth). What’s more odd was that the next item in their list were Rebbachisaurus teeth which were correctly identified as belonging to a sauropod dinosaur.

Long dead musicians

Following on from yesterday’s guest post, I thought it timely to remember a few other musicians who are honoured in palaeontology. It’s really quite common in taxonomy for famous people to have things named after them and especially in some fields when single workers are often near drowned in alpha taxonomy and can run out of names.

I did some of my taxonomic training under someone who worked on parasitoid wasps and these things are enormously diverse. But with only a handful of people worldwide working on them, it wasn’t uncommon for my tutor to name several *dozen* species a year. When it’s happening at that rate, names don’t mean as much as they do to say a palaeontologist who can only do one or two a year or a modern mammologist who might only manage a couple in their whole career.

In addition to Qiliania graffini the most obvious example would be the dinosaur Masiakasaurus knopfleri named for Mark Knopfler of Dire Straits. Trilobites I know cover the Beatles in some detail (even Pete best gets one!) and there are ones for the Grateful Dead and Mick Jagger too. After that I’m running out fast I admit, but I’m sure there are others I don’t know about.

Taxonomic practice and publications

Thanks to some reviews I have been writing, papers I’m working on, conversations with colleagues and a recent blog post, I’ve been thinking much about the practices of myself and my colleagues when it comes to taxonomy. Obviously I’ve written about the how-s and what-s to a degree in the past, but this is a little more specific.

The main point I’d make (as a referee / editor and recipient of referee reports) is one roughly in the line of Voltaire. I disagree with your taxonomy, but I defend your right to publish it.

Now obviously this has limits. You’re specimen must be genuinely diagnostic. You’ll have to use consistent characters. They must be well defined and not vary ontogenetically or be subject to excessive intraspecific variation (or be so massive as to not make this an issue). Or if you are trying to synonymise a bunch of taxa then you’ll need to show that other diagnoses were flawed or didn’t stick to these rules etc.

However, I may think you are overly splitting or lumping something, but I still think you should be allowed to publish (as indeed, so should I). There really are no hard or fast rules as to exactly what constitutes a genus or species. Exactly how many characters you need for one or the other, or whether some are better than others. Taxonomy really does work by consensus and the starting point of any discussion will be the publication of a new taxon / synonymy of an old one. Not allowing such a paper actively inhibits discussion / research.

A paper that on balance few people agree with will soon fall by the wayside. But it’s mere existence will allow a greater depth of discussion by getting people to examine and evaluate the characters at hand and compare them more thoroughly. So let these be published. The authors get a paper, the journal gets a paper, and the worst thing to happen is that a few people quibble about it, everyone gets some citations and we move on, but with a better understanding of the issues.

Here is something I wrote in a review of a paper that intended to name a new species (and has now been published):

I actually tend towards ‘splitting’ over ‘lumping’ myself, and I would not wish to prevent the author erecting a new taxon here if he feels it is necessary, but I would say that I do not think it is required and in the same position I would not erect one myself…. The author does effectively concede all of these points in his text, and clearly still feels the erection of a new taxon is necessary and appropriate and I am happy for him to make that call from a superior position of knowledge, but I do offer a contrary position.

This is a position I wish far more people would take. Make your points and give your opinion, but let the author make their decision and allow for the fact that they have been putting more time and effort into this that you have and know the material better.

On a similar note, I notice a tendency by some (admittedly often online rather than necessarily with respect to the literature, either published or at the review level) to second guess people working on specimens. Now for sure, people with detailed anatomical knowledge of specimens can see certain errors that others will miss (or that at least need to be verified more carefully) based on photos or drawings or descriptions alone. There is nothing wrong at all with making that clear. But I have seen people in the past second-guess authors based on things that haven’t seen. It is most frustrating to be told by someone 5 thousand miles away that you have got something wrong when you have the material in your hands and have been looking at it for months and all they have is a black and white photo of it. (And on that note, there’s a huge difference between asking someone to recheck and telling them it’s wrong. Ultimately the message is the same but the first is polite and the second isn’t. And of course you risk looking very foolish if you are wrong).

This is something raised by Larry Witmer in his excellent recent blog post about the tiny Tarbosaurus. His team commented extensively on the potential taxonomic issues of their work and explicitly which specimens / taxa this might effect and even how. But they also pointedly didn’t make any revisions. With none of them having looked in detail at any of the key specimens, they felt it unwise (and I would suggest, even impolite, impertinent, or maybe even unprofessional) to have done so. I wholeheartedly agree (as you probably guessed form the contents of those parentheses).

Yes there are exceptions to every rule, but as with the above point, I think you have to be careful before messing around with taxonomy and however much you disagree, respect the interpretations and work of your colleagues. If there are huge and obvious errors, then point them out do. But I’d avoid any kind of formal synonymy without having seen critical material first hand. There is, after all, nothing quite like seeing a fossil.

Discovery rates

I talked yesterday about the rate of discovery for dinosaurs and the almost overwhelming mass on new taxa that are constantly appearing. While this is inherently important, what’s more interesting is what this can (or rather cannot) tell us about the total number of dinosaur species that might be out there. In short, 175-ish years since dinosaurs first started being found and recognised as such there has been no real sign of discoveries slowing down and in fact the rate looks to be picking up. With new and important localities in Australia, Argentina and Asia looking very profitable, this might accelerate still further. Even allowing for synonymy we are obviously getting quite a lot of new dinosaurs right now.

In the past people have attempted to predict the total number of dinosaur species that might be out there to be recovered (and obviously that;s not the same as how many there were – not all of them would have entered the fossil record or be identifiable). However, this rather relies on knowing how the discovery rate is changing and also it might change in the future. The rate of discovery of species of all kinds (both living and fossil) follow pretty similar patterns (as shown here rather well on Tet Zoo). They start slow, then shift into an exponential phase and eventually as researchers get near the limit of species to be found, this tails off and flattens out as it takes more and more work to find fewer and fewer species.

The thing is, as long as you are in the exponential phase of discovery, it’s impossible to tell when then tail off is going to be hit. It could be in a couple of years, or it could continue for decades. For the moment, all we can say is that it’s still going up, fast, and with no tail off in sight, we can expect these kinds of discoveries to keep coming. It’ll be some time yet before we can start to think about knowing just how many dinosaurs are out there to add to our taxonomic list.

Dinosaur discoveries

The other day I was shamelessly self-googling Zhuchengtyrannus to keep an eye on how it was spreading through the web. I’ve been surprised at the longevity the story has had and the fact that (admittedly increasingly short and obscure) reports and blog posts are appearing.  One thing that did crop up was the appearance of ZT on a Wikipedia list of new dinosaurs for 2011. While of course this includes various things that are still ‘in press’, it’s only just hit May and already we are at some 26 new genera, and 2010 apparently produced 61 with another 44 from 2009. We are then averaging around 1 a week or even more for new dinosaurs (and by the way, about 1 a month for pterosaurs too). That is really quite something to keep up with and I freely admit that I really struggle.

There are already well over a thousand valid dinosaur genera and about 150 for pterosaurs and I certainly can’t remember all of them, let alone add another half dozen per month. (And don’t forget that of course there are hundreds more invalid names too). Plus a name’s not that much use on it’s own, for it to be of much purpose in your daily work you should at least try to know who described it, where it’s from, how old it is, and which group it belongs to. I also feel like I’m falling further and further behind since I was never really on top of them as it was, and the rate of discovery is massive and seems to be growing.

This is in part perhaps, driving the trend towards specialisation in palaeontology. That compendium of dinosaur biology ‘The Dinosauria’ listed just 8 troodontid taxa back in 2004 (and most of them were known from incomplete remains), but there are now at least 15 of them known and at least a couple more on the way, many of which are known from multiple specimens, and with feathers etc. also preserved. To be an expert on them now takes a great deal more knowledge and study than it did even 5 years ago – someone doing a PhD on them could find the field has tripled in the time it takes them to write a thesis!

That is not something that is conducive to effective cross-referencing of literature. I find it quite common that between my submission of a paper and it’s return from review or time to publication a new taxon has appeared or a directly relevant new paper is published. Integrating this into your work is not always as easy at you might think and sadly I have found some referees to be quite niggly about this (one individual admonished me for not including a paper that hadn’t been published until after I had submitted my manuscript – it seems precognition is now also a requisite for academia). It does make life hard when the rate of research actively exceeds the publication turnaround time and if we keep to, or even accelerate past, one taxon a week, that will only get worse.

Traditional taxonomic rankings

Everyone on here is probably familiar with the old taxonomic ranks of kingdom, phylum, class, order, family, genus and species that was a mainstay of school biology classes and of course was a fundamental part of taxonomic work for, well, pretty much centuries. However, with the advent of cladistics more and more specific groupings of taxa were possible based on branching nature of phylogenetic trees. While there were sub-ranks of subfamilies, superorders, tribes and the like, these were rarely invoked and I think people shied away from them because they implied a level of detail that couldn’t really be inferred based on how these groups were generally formalised.

However, many of the intermediate ranks are rapidly falling by the wayside because they simply are no longer useful or don’t make sense. Kingdoms and phyla are still useful and major groups of taxa that represent fundamental divisions, and of course genera and species are the basis of all taxonomy, but that stuff in the middle? Doesn’t fit.

To take an excellent example (floated my way by Mike Taylor, despite the fact that it should have been obvious to me) birds are in Class Aves, we now accept that birds are dinosaurs but more specifically that means they sit within the traditional Superorder Dinosauria, Order Saurischia, Suborder Maniraptora and (depending on your favoured phylogeny / family definition) Family Paraves. So a Class ends up sitting in half a dozen groups that are supposed to be subordinate to it. And all the various orders and families of birds also sit in there. Oh.

We are increasingly getting close to building the Tree of Life – a single vast and unified trees that put whole phyla together at the species level in clades that most experts generally agree on. No longer are new or odd species somewhat arbitrarily assigned to families or have new families erected for them because they are special. We simply don’t think of trees and relationships in those terms anymore – not everything has to sit in a family, and it’s no longer the case that just a couple of researchers look at their clade and split up the taxa with no reference to related clades or other, wider patterns. As such, while at a conversational level, it still makes sense to use and discuss things like the ‘cat family’ or ‘dog family’ increasingly these are being abandoned for their formal names (Felidae and Canidae in this case) though the endings of various names betray their origins as the –idea, -inae, -oidea, and so on demonstrate. These now represent successive ranks rather than ‘families’ and ‘tribes’ as once they would.

Notes on the taxonomy and identity of Zhuchengtyrannus

After the quick intro to the new taxon, now it’s time to talk in a bit more detail about the bones of Zhuchengtyrannus. All we have is a maxilla and a dentary but that’s actually quite useful. A few ribs and some caudal vertebrae wouldn’t have told us much as these are rather conservative in tyrannosaurs, but happily maxillae are not and have lots of useful and important taxonomic characters in them. It is also worth remembering that pretty much any bone, or even part of one, that is diagnostically different from everything else out there is reasonable to use as the basis for erecting a new taxon (like Brontomerus and various others).

I should of course add, before I go much further, that this is a blog, not a paper. There is more detail and commentary in the actual publication than here in internet land and if you really want to dive in then go read the paper (though again the paper as it stands online is an uncorrected proof, and that has cut off part of the taxonomy stuff!!!). This here is little more (as ever) than a surface discussion of the issues for general consumption and if anything more general than normal as I hope (expect?) that a few more people than normal will be finding the Musings right now as a result of the media coverage.

For those that don’t know their tyrannosaur taxonomy as well as they’d like it’s worth noting that Zhuchengtyrannus is a tyrannosaurine and that puts it in the group of especially large and derived tyrannosaurs and as part of a Late Cretaceous group that was restricted to eastern Asia and North America. We can tell this at least in part because it is a huge theropods from the end Cretaceous of China, but the relatively straight anterior edge of the maxilla supports this, and the shape of the teeth and dentary put it well within the tyrannosaurs in general.

Zhuchengtyrannus teeth. From Hone et al., in press

At this juncture, it’s worth remembering that there are different ways of identifying species, or more specifically, distinguishing them from others. Obviously with a fossil we’re working on a morphological species concept (that is, identifying a species buy it’s anatomy), but more specifically we can separate out differences in different ways. First off we can look for genuinely unique features – a giant tooth in socket 5, only one finger on the hand, a skull twice as long as tall etc. Things that appear in our new species that don’t appear in any others (or at least any other close relatives – stripes are characteristic of tigers since even though other cats are stripey, you’d never confuse the two because of the obvious size differences etc.). Secondly though, you can look for unique combinations of characters. One species may have a long and wide skull, another a short and narrow skull. The characters of ‘long’, ‘short’, ‘wide’ and ‘narrow’ are all in play here, but you could distinguish a possible new species with a clearly distinct combination of ‘long and narrow’ or ‘short and wide’.

So onto Zhuchengtyrannus. This is diagnosed in our paper by two unique characters – a short of shelf on the anterior part of the maxilla and an odd notch in the maxillary fenestra (see figure below). Neither of these does, to our knowledge (or indeed that of the referees or various other colleagues we consulted), turn up in any other tyrannosaur specimen ever. There is also a unique combination of characters to further separate it from other tyrannosaurs in the position of the antorbital fossa and size of the maxillary fenestra.

Drawing of the Zhuchengtyrannus maxilla. The unique shelf is labelled 'S' and the notched fenestra 'mf'. From Hone et al., in press

Although the specimen was not entirely complete when recovered (and sadly the maxilla was later damaged as can be seen from the picture of the maxilla in the previous post) it was initially in very good condition. We have good reason to think therefore that all of these characters are valid ones. The bones were not broken (well they are a bit, but not where the critical characters appear) or distorted or altered and there was no sign of disease or pathologies. This is also not an issue of ontogeny (age-related changes). The animal is easily big enough that it’s hard to credit that it was anything other than an adult, and possibly a large one at that. Moreover, there is a decent literature on both ontogenetic changes in tyrnanosaur skulls and on intraspecific variation. Zhuchengtyrannus exhibits several characters that are normally only seen in adult tyrannosaurs (like the heavy sculpting on the maxilla, more on that later) and the characters we use in our diagnoses are not known to vary either through growth, or within putative populations.

For all of this, lumping taxonomists out there might well not regard this as valid (“To synonymy, and beyond!”). There are those who would still have Tarbosaurus as ‘just’ a species of Tyrannosaurus and I can only suspect they won’t like this much as a result (though I don’t know for sure of course). All I can say is that we are happy with the distinctions, and the referees and other colleagues who have examined the material were too. Taxonomy really does operate at little more than a consensus level and while this can all change, already (from what I have seen and discussed so far) the consensus is that this is a perfectly valid taxon. Of course there’s also a good chance that we will get more material of this species (indeed as noted previously, we may already, even if referral is currently an issue) which will help our cause. Given what bones we currently have, Zhuchengtyrannus seems to be as diagnostic as any other large tyrannosaur and while it could be better (we don’t have that much material), it is sufficient.

Even so, this is only the second tyrannosaurine from China and one that very probably overlaps in time, and space, with Tarbosaurus. As such, it is worth making special note of the differences between these two and again there are some more in the palatal shelf and at the back of the maxilla. In short, it should be very hard to confuse the two if you have a maxilla of either in your hands and there is even better reason to think the two are different and thus again that Zhuchengtyrannus is a genuinely new genus.

I was also reminded in comments in yesterday’s post about ‘Tyrannosaurus zhuchengensis‘ which is detailed in the paper, but initially forgotten here! Whoops. back in the 1970’s several tyrannosaurus-like teeth were recovered from this quarry and, in the manner of the day, named as a new species: Tyrannosaurus zhuchengensis. Later on a single isolated metatarsal (foot bone) was assigned to this species. What of this? Well none of these teeth or the metatarsal show any unique features that would make them diagnostic from any other tyrannosaurin short, if you got a Tarbosaurus or Tyrannosaurus tooth or metatarsal and compared them to the T. zhuchengensis material, you wouldn’t seen any real difference. As such we cannot consider this to be valid and we therefore call Tyrannosaurus zhuchengensis a ‘nomen dubium’ –  a dubious name that should never have been created and should no longer be used (and hence the use of quote marks around it in it’s initial appearance here). Of course this material might be a much earlier record of Zhuchengtyrannus, but we can’t be sure, it might belong to the second taxon, or who knows, even another tyrannosaur!

That’s rather more than I intended to say so I’ll cut it ‘short’ there. More to come tomorrow where I’ll delve into the ecology of ZT and then we’ll be onto the glorious artwork and its genesis and importance in science communication.

What can you do with a fragment?

Having already talked about naming fragments a great many moons ago, it seemed about time I wrote a little more on this subject. Fossil archosaurs of course can be represented by complete articulated skeletons down to just parts of single bones or isolated teeth. As I have discussed before, obviously not of these are equally valuable, or equally valueless, but it might seem obvious that small bits are typically of little use.

The key point here of course is just how diagnostic that ‘fragment’ is (and a fragment here can really be ¾s or more of a large bone). You can probably tell if that distal end of a femur is from a tyrannosaur and that means you must have tyrannosaurs (or for a real example, a pubis). When this might be the only evidence of an entire clade it’s obvious that this is important.

It should therefore be of interest to realise just how diagnostic individual bones, or even parts of bones can be. Chevrons for example all look pretty much alike (or at least there is very significant overlap in morphology over very different taxa) so half of one of them really won’t tell you much, but even there at least some in hadrosaurs for example look rather different to those of theropods or sauropods and can be of some use. Ribs are understandably often of little use, but humeri or maxillae say can be identified to small clades or even species in some cases and so too can little bones like the astragalus and of course neomorphs like pteroids are great.

That mean that while yeah, sure, there are some really rubbish fossils out there that are not really worth collecting, even small bits of small bones can be really important. You may not see much in them, but someone coming through the collection might well be in a position to say “Holy Cow! That can only be left tracularsplanknick bone from a derived pseudomadeupia and they don’t appear in the fossil record for another 50 million years!”. Fragments can be really important.


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