Yet another entry from the fieldguide (though substantially updated and enlarged)...
What might be one of the strangest Cretaceous birds was described in 2004. I refer of course to Aberratiodontus wui of the Jiufotang Formation of Liaoning Province, China.
Named for a near-complete specimen, Aberratiodontus was regarded by its describers (Gong et al. 2004) as one of the most unusual of the enantiornithines or 'opposite birds' (though read on!). In keeping with the tradition of Linnaean taxonomy, they gave it its own eponymous 'family' and 'order' (these being 'Aberratiodontuidae' and 'Aberratiodontuiformes', respectively). If you know anything about fossil birds you'll know that the useless practice of creating redundant higher taxa for distinctive species has been all too common [adjacent skull reconstruction from Gong et al. (2004): read on].
While the Aberratiodontus holotype specimen is reasonably complete [holotype specimen LHV0002 shown below (though LHV0001a and LHV0001b are given as the accession numbers in the body of the text), from Gong et al. (2004)], many of its bones are poorly preserved and have broken surfaces, making confident interpretation rather difficult. In fact, many of the claims made in the descriptive paper are arguable and unlikely to be correct. Gong et al. (2004) identified prefrontals and a robust postorbital, for example, but the excellent photos they provided show that the 'prefrontals' may just be parts of the nasals (prefrontals actually seem to be absent in birds anyway) while the 'postorbital bar' is not definitely complete as they showed in their reconstruction (that's rather ironic, as the 'diapsid status' of the skull was used in the title, as if it were one of the most significant details of the specimen). A complete postorbital bar is seen elsewhere in Mesozoic birds: confuciusornithids and the enantiornithine Protopteryx possess it; Archaeopteryx seems to have one (Tischlinger 2005), and at least a few others do too.
The relatively short toe claws suggest that Aberratiodontus was not a habitual percher, and the proportions of its hindlimbs and its relatively long neck suggest that it was a terrestrial forager. Its large sternum and wing proportions indicate that it was a capable flier. Perhaps it preyed on large arthropods, small vertebrates and other animals (it was reasonably large for a Cretaceous bird, with a skull about 58 mm long and neck 88 mm long). I make all of these assertions without having done any of the appropriate quantitative comparisons, however...
Its most unusual feature is its dentition: it was regarded by its describers as being heterodont. Gong et al. (2004) claimed that 21 teeth can be seen to line each maxilla, but again this is difficult to be confident about, as only a handful of maxillary teeth are actually visible (somewhere round about 8 or 9). Poor preservation of the premaxillary margins mean that the number there can't be asserted with confidence either (though 4 teeth in each premaxilla is a good guess). There are about 24 teeth in each dentary. This is unusually high (12 or so is more typical for toothed Mesozoic birds [many had less]) and could be diagnostic. What is obvious is that the teeth at the front of the maxilla are smaller than the premaxillary teeth, and than those in the posterior part of the maxilla. The teeth are reported to differ in terms of possession or absence of carinae, but the terminology used in the paper is highly idiosyncratic and difficult to make sense of [the holotype skull is shown here: you might like to compare it to Gong et al.'s reconstruction, shown at the very top].
The sternum of Aberratiodontus has strongly divergent posterolateral processes that have slightly expanded ends. This is reminiscent of what's seen in various enantiornithines and other Mesozoic birds, though the posterolateral processes aren't normally as divergent as they are in Aberratiodontus [speculative life restoration of Aberratiodontus shown below].
At the risk of spending more time commenting on the paper than on the taxon it describes, I must also note that the authors interpreted the style of tooth replacement inferred in Aberratiodontus as being more similar to that of crocodilians than that of non-avian theropods; on the basis of this, the authors implied that birds might not be dinosaurs*. I think they were influenced by the fact that the new teeth of Aberratiodontus form concavities on the lingual sides of the older teeth's roots during their development. I don't understand why they think this tells you anything about the affinities of birds (exactly the same developmental pattern is seen in maniraptoran theropods).
* Actually, they wrote "It would be a new question about the dinosaurian hypothesis of bird origins accepted widely that meet a new challenge" (Gong et al. 2004, p. 6).
I note a strong and consistent link between (1) bizarre interpretations and poor descriptions and (2) BAND support (BAND = the Birds Are Not Dinosaurs movement). Sorry if that sounds mean, but it's true. If I were bolder and prepared to stick my neck out, I think I would say that the BAND movement only remains alive because of bad science, not because there are wise, ingenious authors making novel observations and forming strong arguments.
While it's true that enantiornithines have proved to be a diverse, speciose clade, the problem with such groups is that people soon come to assume that any and all new species are members of said groups. That may be exactly what's happened here. Enantiornithines can be identified by such characters as their distally projecting third metacarpal, distinctively large posterior trochanter on the femur, and narrow fourth metatarsal. Yet none of these features are visible, or have been reported, in Aberratiodontus.
It's... it's... another specimen of Yanornis?
Have any other opinions been expressed on Aberratiodontus since its description? Zhou et al. (2008) - in a footnote - doubted most of Gong et al.'s conclusions, and argued that Aberratiodontus can be excluded from Enantiornithes on the basis of its large cnemial crest. They went even further, and stated that Aberratiodontus is not a distinct taxon at all, but is actually synonymous with Yanornis [holotype of Yanornis martini shown here, from Zhou & Zhang (2001)]. Cau & Arduini (2008) included Aberratiodontus within a cladistic analysis of Mesozoic birds, and found it to be a close relative of Yanornis (see the comments for more on this).
And Yanornis isn't an enantiornithine - it's a member of a small clade of Cretaceous birds that are more closely related to neornithines than enantiornithines are (Clarke et al. 2006). Yixianornis grabaui and Songlingornis linghensis are the other identified members of the group: the existing names Yanornithidae Zhou & Zhang, 2001 or Yanornithiformes Zhou & Zhang, 2001 could be used for the group, but Clarke et al. (2006) chose not to use any name for the clade for some reason. And there's a lot that could be said about the 'yanornithids', but it'll have to wait to another time. The proposal that Aberratiodontus might be a misidentified member of this group is an interesting one that looks likely to be correct, but more work is needed to determine whether Aberratiodontus is a distinct taxon within this clade - as supported by Cau & Arduini (2008) - or synonymous with Yanornis, as suggested by Zhou et al. (2008).
For previous articles on enantiornithines and other Mesozoic birds see..
- Tet Zoo picture of the day # 24 [on archaeopterygids]
- The new Crato Formation enantiornithine
- A stunning new Mesozoic bird... well, new-ish
- Epidexipteryx: bizarre little strap-feathered maniraptoran
- Long and Schouten's Feathered Dinosaurs, a review
- Cyril Walker
- The Mesozoic birds with weird, plastic-strip-style tail structures
- Alexornis and other 'alexornithiforms'
And given that I've said negative things about the BAND movement, you might like to see...
- Publishing with a hidden agenda: why birds simply cannot be dinosaurs
- ... and this comment on the James & Pourtless paper.
Refs - -
Cau, A. & Arduini, P. 2008. Enantiophoenix electrophyla gen. et sp. nov. (Aves, Enantiornithes) from the Upper Cretaceous (Cenomanian) of Lebanon and its phylogenetic relationships. Atti della Societa Italiana di Scienze Naturali e del Museo Civico di Storia Naturale in Milano 149, 293-324.
Clarke, J. A., Zhou, Z. & Zhang, F. 2006. Insight into the evolution of avian flight from a new clade of Early Cretaceous ornithurines from China and the morphology of Yixianornis grabaui. Journal of Anatomy 208, 287-308.
Gong, E., Hou, L. & Wang, L. 2004. Enantiornithine bird with diapsidian skull and its dental development in the Early Cretaceous in Liaoning, China. Acta Geologica Sinica 78, 1-7.
Tischlinger, H. 2005. Neue Information zum Berliner Exemplar von Archaeopteryx lithographica H. v, Meyer 1861. Archaeopteryx 23, 33-50.
Zhou, Z., Clarke, J. & Zhang, F. 2008. Insight into diversity, body size and morphological evolution from the largest Early Cretaceous enantiornithine bird. Journal of Anatomy 212, 565-577.
- . & Zhang, F. 2001. Two new ornithurine birds from the Early Cretaceous of western Liaoning, China. Chinese Science Bulletin 46, 1258-1264.
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Is it just me, or does the skull in the reconstruction of Aberratiodontus look a lot like that of a coelophysoid. Parallel evolution maybe?
The genus name is oddly formed, but the family and order names are just hilariously crazy.
Is it just me, or are initial papers unveiling taxa, even today, pretty wrong on major things nearly half the time? It seems like this is a particular issue with some of the Chinese papers coming out (perhaps because they don't have access to as much of the contemporary literature as people in the West do), but I also wonder if it's because the discovery team can be just about anyone who stumbled upon the fossil/formation, and not experts in the particular clade.
On that note, could you do a post on Yandangornis some time soon? Its late age, along with it supposedly being a neoflightless long-tailed avialan, makes me suspect the initial analysis was shoddy and it's an Oviraptorosaur or something.
With all due respect, I've seen FAR WORSE papers in the paleomammalogy literature. How about Childs Frick's 1937 horned ruminant monograph, which violates the iCZN on almost every page (no diagnoses; subgenera that are not defined as to which genera they belong to; no useful descriptions or comparisons; terrible oversplitting of taxa, with each sample from a different hole in the ground named a new species?). Or how about the godawful pieces of shit that Schultz and Falkenbach published about oreodonts, as late as 1968 in the AMNH Bulletin? They grossly oversplit the taxonomy based on specimens that were laterally or dorsoventrally crushed; they knowingly falsified stratigraphic data; there are NO useful measurements or statistics to support their ideas; their stratigraphic concepts are grossly wrong, etc.--for 8 separate monographs! And of course we could go back to Henry Fairfield Osborn's weird taxonomic concepts, which caused him to misinterpret and oversplit brontotheres, proboscideans, etc. Once you've been in this biz a while, you find out who the incompetents were (Osborn, Frick, and Schultz), as opposed to talented scientists who dealt with the same quality of material but got it right (e.g., W.D. Matthew, G.G. Simpson, and just a few others...)
They did what?? Holy crap! Is this documented somewhere?
in my paper on Enantiophoenix (Cau and Arduini 2008), I included Aberrationdontus in a phylogenetic analysis of basal birds: it resulted the sister-group of the "Yanornis + Yixianornis" clade. Placing it in Enantiornithes produced a tree at least 12 steps longer than the most parsimonious topology, supporting its euornithine/ornithuromorph status.
Cau, A. and Arduini, P. (2008). "Enantiophoenix electrophyla gen. et sp. nov. (Aves, Enantiornithes) from the Upper Cretaceous (Cenomanian) of Lebanon and its phylogenetic relationships". Atti della Societa Italiana di Scienze Naturali e del Museo ivico di Storia Naturale in Milano 149 (2): 293-324.
@dartian: Yes, it is. A number of scientists have gone back to the field labels on original specimens, and found that S&F altered the info in the monographs to fit their preconceptions. In other words, if the specimen didn't look like what they expected, they assumed the field data was wrong and changed it in their monographs without mentioning the discrepancy. Several people have mentioned this in print, although it would take a while for me to find the citations....
Andrea (comment 6): my apologies, I had overlooked your inclusion of the specimen in your analysis. I'll go back and correct the article. Thanks!
"If I were bolder and prepared to stick my neck out, I think I would say that the BAND movement only remains alive because of bad science, not because there are wise, ingenious authors making novel observations and forming strong arguments."
^ You just said it. :P
However I agree. It seems most of the 'arguments' put forth fall into the 'one vague questionable trait trumping hundreds of other well supported traits' category.
Just looking at an average bird, I can't imagine how people didn't grasp it before. But then I'm a total uneducated amateur enthusiast.
At the risk of commenting more on the paper than on the bird... what Andreas (comment #2) said! The "u" in these names is etymologically un-called-for.
I have noticed that a number of Chinese paleontologists are a bit shaky on their Latin and Greek: failure of gender agreement between genus and species, for example. Considering the things they HAVE had to master before being able to publish in Western scientific journals, though, I suppose this is almost forgivable.
Donald Prothero (comment #4)-- I've JUST, in the last two or three days, been looking at your (very interesting!) papers in the "Evolution of Artiodactyls" volume you edited with Scott Foss. It sounded to me as if Childs Frick was at least consistent in following a principle-- perhaps a misguided principle, but a principle nonetheless: if specimens come from different localities, don't assume that they are the same species, but give them different names. ... Since later lumping (synonymization) can perhaps be done with less hassle than splitting (no problem figuring out what an earlier author had in mind after a lumping, whereas after a splitting you have to figure out WHICH of the new taxa the specimens referred belong to), it seemed as if there might almost be a motivation for his policy. A real contender for the "worst paper ever" title shouldn't even be consistent!
(Prothero & Foss "Evolution of Artiodactyls" -- library at my former university didn't have it and I'm just catching up with it now-- is a beautiful book! And it's a pity Pediomeryx couldn't have lasted a few million more years.)
Not to bang on, isn't "mirror birds" a more euphonious translation of "enantornithines" than "opposite birds" or the literal "in-front-of birds"? "Looking-glass birds" might be more appropriate to their antiquity.
I think the primary reason Clarke et al. have not applied a name for the clade they resolved, nor named a new clade in lieu of an older name they could have used, is because of something that Dave Hone hints at on his own blog:
In Phylogenetic Taxonomy, unlike Linnaean taxonomy, names are not associated with ranks, and certain conventions in Linnaean taxonomy allude to ranks even though the describer of said name did not intend it (which causes trouble downstream). Were Clarke et al. to support use of Yanornithidae/Yanornithiformes or any other name like these, the clade would be instantly labelled a ranked taxon, rather than simply a monophyletic, nonranked group.
In at least one way, they approach may be a "wait and see" technique, as the PhyloCode is around the corner, and its placement for non-ranked taxonomy as mainstream is picking up steam. At the point it becomes likely that any name will not be pegged immediately by mainstream taxonomists as a ranked one, then I think Clarke et al. would be secure in providing nomenclature for supraspecific taxa in the manner you request.
What I find most intriguing about Aberratiodontus are the caniniform teeth in the reconstruction. That's very rare for... ornithodirans in general. They're... much less clear in the grainy photos, but even without them, A. has awesome teeth for a bird, what with all those independent reductions and losses of teeth happening all over the bird tree! And carinae on the teeth? Cutting edges? That's just too cool.
Caniniform teeth? Where? Those look pretty homodont to me.
Hold on a sec... where is the idea of Largirostrisornis being an ornithuromorph coming from? You meant Songlingornis I'm sure.
As for worst paper ever, I submit Bruhathkayosaurus, Dandakosaurus, Timimus, Hou's 1997 Mesozoic Birds of China, anything from Czerkas' Feathered Dinosaurs volume...
The fourth tooth, in both (p?)mx and d, is distinctly enlarged.
(Again, I'm talking about the reconstruction. The photo is less clear, though it doesn't rule it out.)
Or Liaoningornis, which was described as a euornithine (...but may not be one).
Mickey - my bad, sorry. Yeah, I meant Songlingornis. Stupid Hou names :)
Re: "heterodonty" - first, it's a stretch to call that heterodonty. Second - let's say for a minute that the reconstruction IS right (which, it most likely is not, based on the actual photo of the specimen) - odds are this is a tooth that has just slipped out of it's socket a little bit.
Heterodonty has a loose meaning when it comes to general reptilian discussions. It is used, for example, to differentiate the anterior and middle teeth of a tyrannosaur upper jaw, as in the mandible of Ornitholestes, as in Proceratosaurus, etc. It simply refers to multiple "forms" of teeth. This is relatively distinct from the mammalian useage, in which it differentiates incisiform, caniniform, molar-like premolars, carnassial-like, and molariform; it also differentiated different forms of molariform, such as the bunodont or triconodont conditions.
If the enlarged teeth in Hou et al's illustration is accurate, it potentially differentiates two different sizes, but not two different morphologies, and size is not, to my understanding, part of any useage/definition for heterodonty (but this is not Darren's fault, anyway; it's Hou's).
Bad as it may be, this paper must surely yield the honours to Ann Elk's paper on the brontosaurus.
I think the term "anisodonty" is sometimes used for dentitions with such teeth of different sizes, though "heterodonty" is pretty commonly used, too, IIRC.
Anisodonty is used generally only in Mammology where it refers to the difference between the width of the upper molars versus the lower molars. If used generally, it would only refer to differential crown width, or differential tooth size in upper versus lower dentitions (which is a given in virtually all reptiles anyway).
Anisodonty can be positive if the lower molars (width-wise) are larger than the upper (and this is common in browsers), while the inverse would have negative anisodonty as seen in carnivorans (uppar carnassials can be an order of magnitude larger than their opposite).
Heterodonty is the commonly used term to refer to differential tooth sizes along a row, so that a variable dental series (excepting Z-spacing) with discrete regionalization via size would be "heterodont" in the weakest sense. This appears to occur in Aberratiodontus, but only in regards to the mesial dentary teeth [see previous post #20 for further examples of "heterodont" dinosaurs using this definition, though you can throw troodontids (sans Anchiornis) into this as well].
@Darren: That's very charitable of you to give Frick such a benefit of the doubt, but I've read nearly everything he wrote, and went through his unpublished work on many different groups, and there's no getting around it: Frick was rich but incompetent. He completely ignored the rules of taxonomy that were in force for many years by not diagnosing his taxa or even providing rudimentary descriptions; he was a a hypersplitting typological taxonomist of the bad old 19th century tradition, where nearly every specimen got a new name; and he couldn't make sense of anatomy and taxonomy, no matter how rich he was. I've been through his work with a fine-toothed comb, and he wasted (or I should say, he made his lackies waste) huge amounts of time measuring and comparison ratios of camel metapodials to toothrows--two simultaneously enlarging variables that would GUARANTEE systematic confusion! When I revised the early camels (1996), I spotted lots of synapomorphies in the skull and ear region that Frick missed entirely. Ask anyone who has had to deal with Frick's crap in the past few years, and they'll agree. About the only useful things in his publications are the stuff he paid competent people to do: the catalogues of specimens, the illustrations, etc. And most of it would probably never have been published if Frick hadn't been a millionaire son of a robber baron (Henry Clay Frick, Carnegie's partner) and a powerful rich trustee of the AMNH who got whatever he wanted because of his wealth. There's no reason to sugarcoat it, and our generation has been slowly trying to clean up the mess he left over 80 years ago...
Hi Don - very interesting message :) Just to clarify though: you imply in the first line that I was defending Frick somewhere... however, I haven't said anything about Frick in the comments here; you might be responding to someone else's comment perhaps? Anyway, I agree with your points entirely; well said.