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.

26 Responses to “Notes on the taxonomy and identity of Zhuchengtyrannus”


  1. 1 ronen 01/04/2011 at 1:44 pm

    “Even so, this is only the second tyrannosaurine from China and one that very probably overlaps in time, and space, with Tarbosaurus.”

    What about the polyspecific *Alioramus* from Mongolia?

    • 2 David Hone 01/04/2011 at 1:53 pm

      Well Ive seen that fall in and out of tyrannosaurines so it could go either way. Though more to the point this is significnatly bigger and rather differently built to Alioramus so there’s no real risk of confusion, unlike, potentially, Tarbosaurus.

    • 3 Dave Howlett 01/04/2011 at 4:02 pm

      Although the only described material is somewhat scanty, another potentially coeval tyrannosauroid – though probably not tyrannosaurid – is Alectrosaurus. Again, probably a different niche from Tarbosaurus and Zhuchengtyrannus.
      I hope that the undescribed material I recall hearing about once gets examined at some point – especially now we have more skeletal remains of Alioramus to compare it to.

      • 4 David Hone 01/04/2011 at 4:05 pm

        It’s already under examination and description. The papers have been split to facilitate our writing them, but the work was being some somewhat in parallel. Don’t worry, we’re not going to stop with this one!

  2. 5 Tim Donovan 01/04/2011 at 1:49 pm

    Sure, Zhuchengtyrannus was probably coeval with Tarbosaurus. And it overlapped in space in the sense of being an Asian form. I assume, though, that Tarbosaurus was adapted to drier, central Asian habitats with, perhaps, more ankylosaurs and sauropods.

    • 6 David Hone 01/04/2011 at 1:55 pm

      Well until we have a better idea of the fauna and climate of the ZT site, we can’t say for sure. And in any case, some modern predators at least have colossal ranges and live in massively different ecosystems and habitats (think of pumas or leopards or wolves). So I’d not be surprised say if Tarbosaurus turned up here, or in another, similar site somewhere else.

      • 7 Tim Donovan 01/04/2011 at 3:27 pm

        Of course, Zhuchengtyrannus isn’t the only new form from those beds. I wonder if nodosaurs are present. Judging by North America, it seems like the right kind of environment, and the Udurchukan yielded one.

      • 8 David Hone 01/04/2011 at 4:12 pm

        Well without trying to give much away or spoil anyone’s party there are other new taxa in these quarries to be described and more excavations are happening. That’s about all I can say for now.

  3. 9 Matt k 01/04/2011 at 2:40 pm

    Chessbase (probably the biggest chess news site on the web) has a page up joking that Zhuchengtyrannus is named after the former women’s world champion, Zhu Chen. I think it’s intended as an April Fool’s day joke, and they do note the real etymology at the end. Anyway, that’s one way of getting the word out.

  4. 11 Tim Donovan 01/04/2011 at 4:17 pm

    Elsewhere someone mentioned ankylosaurs, albeit unidentified, are present in those beds. Well, WFTP. :)

  5. 12 Marc Vincent 01/04/2011 at 5:13 pm

    Hate to interrupt, but the Telegraph article is online, and it is predictably terrible. From the paper that brought you giraffe-sized flying dinosaurs: http://www.telegraph.co.uk/science/dinosaurs/8420106/T-Rexs-cousin-found-in-China.html

    • 13 David Hone 01/04/2011 at 5:18 pm

      I avoided reading it, and that of the Daily Mail. Against my better judgment, I *always* end up reading the comments and then getting very annoyed and then arrrgh! I had been tempted to note that in general what I had seen was pretty good and accurate and I was pleasantly surprised to see that most places kept our use of ‘tyrannosaurine’ over ‘tyrannosaur’, but clearly they are not all perfect.

    • 14 David Hone 01/04/2011 at 5:20 pm

      Oh dear. I even did a phone interview with them (well, someone from associated press, but those quotes come direct from it) which is rather cheeky as they only asked me to explain things, not provide direct quotes or soundbites which is rather different. The joys of the media.

  6. 15 Dave Howlett 01/04/2011 at 5:21 pm

    I suspect you misunderstood my earlier comment ;) though my slightly unclear writing style may have contributed – I was not referring to the undescribed material found in association with Zhuchengtyrannus, but undescribed material I have heard mentioned before elsewhere which is (allegedly) referrable to Alectrosaurus, which I was mentioning as another member of the tyrannosauroid clade which may have been contemporary with Zhuchengtyrannus.

    Good to hear that there is further tyrannosaur work coming from you and your collaborators, though! :)

    • 16 David Hone 01/04/2011 at 7:41 pm

      Ah gotcha. Sorry, I didn’t know of any other Alectrosaurus and obviously with us having that as yet undescribed tyrannosaur material I made the wrong connection.

  7. 17 Tim Donovan 01/04/2011 at 6:19 pm

    I have some doubts that Alectrosaurus was contemporary with Zhuchengtyrannus. Godefroit suggested Iren Dabasu correlates with the Nemegt formation based on ostracod and charophyte data but it has more in common with the Barun Goyot. Interestingly, Currie et al. referred an ankylosaur from Erenhot to Talarurus.

  8. 18 "Dr." S Beckmann 01/04/2011 at 9:57 pm

    Congrats Mr. Hone! I only read about this earlier today- April Fools Day!!
    I’ll be at the National Fossil Expo 33 in Macomb IL tomorrow should you or anyone want to sue me, er, see me… but I thought if you or anyone reading your blog (or your friends or your enemies) ever needed a somewhat good or maybe just average paleo-chuckle, you might want to check out the Center for Cretaceous Studies at http://c4cs.tripod.com and PLEASE don’t take anything on it as remotely serious.
    Thanks and best of luck!

  9. 20 Ben Chasteen 01/04/2011 at 11:18 pm

    RSS feed request to Before It’s News

    Hi, Mr. David Hone

    My name is Ben Chasteen and I’m the Science editor at Before It’s News http://www.beforeitsnews.com. Our site is a People Powered news platform with over  2,500,000 visits a month and growing fast.

    We would be honored if we could republish your blog RSS feed in our Science category. Our readers need to read what your Archosaur Musings blog has to say.

    Syndicating to Before It’s News is a terrific way spread the word and grow your audience. Many other organizations are using Before It’s News to do just that. We can have your feed up and running in 24 hours. I just need you to reply with your permission to do so. Please include the full name and email of the person who will be attached to the account, and let me know the name you want on the account (most people have their name or their blog name).

    You can also have any text and/or links you wish appended to the end or prepended to the beginning of each of your posts on Before It’s News. Just email me the text and links that you want at the beginning and/or ending of each post. If you know html you can send me that. If not, just send me the text and a link to your site. It should be around 200 characters or less (not including links).

    You can, if you like, create a custom feed for Before It’s News that includes multiple links back to your blog or web site. We only require that RSS feeds include full stories, not partial stories. We don’t censor or edit work.
    Thank you,

    Ben Chasteen
    
Editor, Before It’s News

    http://www.beforeitsnews.com

  10. 22 Robert Sloan 02/04/2011 at 12:23 am

    This is so great. I enjoy your blog anyway and it’s a delight to see you find and name something so extraordinary and newsworthy. Awesome work. Thanks for the very thorough write-up too and congratulate Bob on the beautiful illustration.

    I’m enjoying this and looking forward to more in the series.

  11. 24 Dave Godfrey 03/04/2011 at 9:07 pm

    Congratulations on the new paper.

    I have to admit I don’t quite understand why people want to synonymise Tarbosaurus and Tyrannosaurus (and perhaps by extension Zhuchengtyrannus) genera are arbitrary, and while these animals might all be very closely related in terms of communication renaming Tarbosaurus bataar/i> to Tyrannosaurus bataar doesn’t really help anyone.

    Does ZT shed any light on this? Or are there not enough characters to define a new species, but not do a decent cladistic analysis?

    • 25 David Hone 03/04/2011 at 10:12 pm

      Hi Dave, thanks. And yes i agree entirely, and in this case too, it has been noted by Tom Holtz and others that Tarbosaurus and Tyrannosaurus do have a hell of a lot of distinguishing characteristics, in fact more so that for several other tyrannosaur taxa. In other words they are arguably ‘more distinct’ than most of the others, and so are the least obvious candidates for synonymy (though of course their typical sister-taxon relationship complicates that a little).

      And yes to the second part, there;s enough to be diagnostic, but not enough to say much meaningful about their relationships, though we are looking into that for the second paper so we’ll see what happens later.


  1. 1 OK, so I’m just milking it now – final Zhuchengtyrannus roundup « Dave Hone's Archosaur Musings Trackback on 05/04/2011 at 10:00 am

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