First of all, many many thanks to everyone (both here and at SV-POW!) for the congrats regarding baby Emma. I am, shall we say, a little tired right now, but as you'll know if you've visited SV-POW! this morning, the good news as goes blogging is that I've been able to get lots of stuff prepared in advance. In theory, therefore, things won't be so different here on Tet Zoo. The one thing I haven't had time to prepare is 'the reveal' on that mystery picture from the other day, but I'll get round to that soon, thanks for your patience. Ok, to business...
I think I've said before that I tend not to cover dinosaur news on Tet Zoo. Mostly this is because dinosaurs are so absurdly popular that virtually all and any new publications are announced and discussed in the media, on blogs of all stripes, or at widely accessible web-locations like the Dinosaur Mailing List. However, maybe I have a 'special' perspective on this area because - like others in the dinosaur research community - I'm more dino-aware than most. In fact, while it might seem that everyone gets talking about new dinosaur discoveries when they appear, I suppose in many cases it might, actually, only be the few hundred dinosaur researchers round the world who are really talking about this stuff. What the hell, let's just throw this out there and see what happens.
We are now at a stage in the development of our science that not a month goes by without there being quite a few interesting and/or 'important' announcements. I thought it would be a nice idea to illustrate this by looking at one month alone, so here we go on the dinosaurs of January 2009. I'm also going to cover the pterosaurs of the month too.
Let's start with the theropods. One of the most exciting things from the past few weeks has been the publication of a second Beipiaosaurus specimen [the specimen is shown at the very top of the composite picture above [image from Xu et al. (2009)], and a close-up of its neck region is shown at bottom left of the composite. The image at bottom right in the composite is the tail of another specimen: read on. Scale bar in A = 50 mm]. Beipiaosaurus, originally named in 1999, is a basal therizinosauroid from the famous Yixian Formation of Liaoning Province. The first specimen (representing the new taxon Beipiaosaurus inexpectus) is mostly disarticulated, but it preserves dense patches of parallel integumentary structures in association with its lower arm and leg (Xu et al. 1999). Given that therizinosauroids are (while still of unsettled phylogenetic position: read on) definitely nested within Coelurosauria, we would certainly predict the presence of integumentary structures (meaning 'proto-feathers' and feathers proper) within the group, but it's always nice to have it confirmed. A pygostyle-like structure was later discovered in the holotype specimen (Xu et al. 2003)*. However, rectrices aren't preserved in the specimen and it was suggested that the fused distal caudals might have evolved for some function other than rectricial support. Image below shows the fused distal caudals of the Beipiaosaurus inexpectus holotype (distal is to the right). The fused distal end includes five vertebrae. It is straight but, unlike a true pygostyle, does not seem to be laterally compressed.
* The holotype was discovered in two phases. Limb fragments and dorsal and cervical vertebrae were discovered initially. The discovery site was re-excavated later on, and this time an articulated tail and partial pelvis were discovered. All come from the same individual.
In fact, the odd thing about Beipiaosaurus has always been that all of its integumentary structures are simple: none are true, vaned feathers, and perhaps they should be if therizinosauroids are maniraptorans close to oviraptorosaurs (which, like deinonychosaurs and birds, definitely did have true, vaned feathers). Here's where the new discovery comes in. A second specimen was published in January: it only consists of the front half of the animal, but it's in good shape (Xu et al. 2009). Because the authors couldn't be completely sure that it belongs to the same species as the holotype, they labelled it Beipiaosaurus sp. Again, it preserves a good covering of integumentary structures, and again most of them are simple, filament-like 'proto-feathers' resembling those seen on basal coelurosaurs like Sinosauropteryx.
But hold the press. Sprouting from its throat region, the back of its head, its neck and its back are much longer, thicker structures that look like they were stiff and spine-like. New preparation of the holotype reveals that the same structures are also present on the tail (though not associated with the pygostyle-like structure). Xu et al. term these 'elongated broad filamentous feathers' (or EBFFs... what is it with the need to invent acronyms for these structures?). Well, this is c-o-o-l. Previously, we've imagined therizinosauroids rearing up to full height and striking out with their long hand claws when confronted by predators. It's now possible that they were spiny and that the EBFFs served a defensive function, though as usual we don't really know what these structures were for and a role in display is equally likely [image below, from Xu et al. (2003), shows part of the jumbled holotype specimen on the right. Close-up of tail tip at left].
The presence of the EBFFs in Beipiaosaurus raises two interesting issues. Most recent phylogenetic studies have found therizinosauroids to be part of Maniraptora (the branch-based coelurosaur clade that includes all taxa closer to birds than to ornithomimids), and close to oviraptorosaurs (let's not mention that whole Enigmosauria thing). Oviraptorosaurs, deinonychosaurs and birds all possess true, vaned feathers, including remiges (the big feathers on the forelimb) and rectrices (the big feathers on the tail). We'd predict, therefore, that therizinosauroids would have such feathers too - I've previously illustrated them as such, as have others - so it's odd that they don't.
Ok, it's possible that like, say, kiwis (ha ha ha ha) they had degenerate integumentary structures, but... might it be that therizinosauroids aren't part of the oviraptorosaur + deinonychosaur + bird clade (ODBC) after all? As it happens this is exactly what a few workers - namely Sereno (e.g., 1998, 2001) and Senter (2007) - have found. Sereno has been recovering therizinosauroids as part of a clade that also includes ostrich dinosaurs and alvarezsaurids: I don't buy this at all and haven't ever found it in my own work (though I did recover an ornithomimosaur + alvarezsaurid clade). Senter, however, found therizinosauroids to be the most basal maniraptoran clade, more basal than alvarezsaurids and the ODBC. It's now tempting to suggest that the absence of vaned feathers in therizinosauroids supports the idea that they're outside of the ODBC. In other words, therizinosauroids lack big vaned feathers because they never had them, not because they lost them. We await further finds and further testing [cladogram below, taken from one of my theropod lectures, shows distribution of vaned feathers in Maniraptora. It's now out of date: vaned feathers are now known for troodontids (Jinfengopteryx: discussion here), and their presence in what are here labelled as dromaeosaurines has been confirmed via the discovery of quill nodes in Velociraptor. So - within the ODBC - only therizinosauroids now lack vaned feathers).
The second implication concerns the big picture. The EBFFs of Beipiaosaurus are strikingly simple, and the similarity they have with the 'stage 1' feathers hypothesised by Prum and Brush has not been lost on some. In fact Xu et al. (2009) go as far as noting that EBFFs are similar to the simple, unbranched filaments present in Psittacosaurus and pterosaurs: accordingly, they suggest that monofilamentous integumentary structures might have been present in the ornithodiran common ancestor [the psittacosaur with the tail bristles is shown below: this specimen was published by Mayr et al. (2002)]. This idea was also suggested by Bonde & Christiansen (2003), and of course has been mooted by various people before. Imagine for a moment that it's true. We know that animals like, say, big ornithopods and sauropods were scaly skinned, but here is mainstream support for the concept of furry baby sauropods and hadrosaurs, of quilly crests in small ornithopods, and of fuzzy coatings in silesaurus and marasuchians.
There's lots more stuff to say about the new Beipiaosaurus. The specimen is particularly neat in preserving a complete skull. As Adam Yates already noted over at Dracovenator, this skull looks superficially like that of an iguanodontian. Given that Beipiaosaurus is one of the most basal known therizinosauroids (Falcarius is more basal, and then there's controversial Eshanosaurus), here's more evidence showing that therizinosauroids evolved a bunch of specialisations (for whatever it was they were doing) early on in their history. This may have implications for the distribution and evolution of feeding styles in maniraptorans, particularly so if therizinosauroids are outside of the ODBC as discussed above. Anyway, I gotta stop there. Next: alvarezsaurids and Anchiornis.
Therizinosauroids have been covered on Tet Zoo before: go here. And for discussions of the fuzz and feathers of non-avian theropods see Feathers and filaments of non-avian dinosaurs, part I and part II.
Refs - -
Bonde, N. & Christiansen, P. 2003. The detailed anatomy of Rhamphorhynchus: axial pneumaticity and its implications. In Buffetaut, E. & Mazin, J.-M. (eds) Evolution and Palaeobiology of Pterosaurs. Geological Society Special Publication 217. The Geological Society of London, pp. 217-232.
Mayr, G., Peters, D. S. & Plodowski, G. 2002. Bristle-like integumentary structures at the tail of the horned dinosaur Psittacosaurus. Naturwissenschaften 89, 361-365.
Senter, P. 2007. A new look at the phylogeny of Coelurosauria (Dinosauria: Theropoda). Journal of Systematic Palaeontology 5, 429-463.
Sereno, P. C. 1998. A rationale for phylogenetic definitions, with application to the higher-level taxonomy of Dinosauria. Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen 20, 41-83.
- . 2001. Alvarezsaurids: birds or ornithomimosaurs? In Gauthier, J. & Gall, L. F. (eds) New Perspectives on the Origin and Early Evolution of Birds: Proceedings of the International Symposium in Honor of John H. Ostrom. Peabody Museum of Natural History, Yale University (New Haven), pp. 69-98.
Xu, X., Cheng, C., Wang, X. & Chang, C. 2003. Pygostyle-like structure from Beipiaosaurus (Theropoda, Therizinosauroidea) from the Lower Cretaceous Yixian Formation of Liaoning, China. Acta Geologica Sinica 77, 294-298.
- ., Tang, Z.-l. & Wang, X.-l. 1999. A therizinosauroid dinosaur with integumentary structures from China. Nature 399, 350-354.
- ., Zheng, X. & You, H. 2009. A new feather type in a nonavian theropod and the early evolution of feathers. Proceedings of the National Academy of Sciences 106, 832-834.
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It is rather strange that therizinosaurs do not have vaned feathers, but one has to also realize that an animals place in the family tree is not only due to integumentary features. There could be many explanations for this. First, perhaps therizinosaurs could be the most basal maniraptorans (I've actually heard this suggested somewhere), and the rest of the maniraptorans form a clade to the exclusion of Therizinosauroidea, say clade Ornithoptera or something.
Secondly, it could be that therizinosaurs do indeed form a clade with Oviraptorosauria, and oviraptors have merely developed their bird-like features independently. It wouldn't be the first time, oviraptors developed near-toothless beaks and pygostyles independently, so it probably wouldn't be so unusual, just a very creepy case of convergent evolution.
And of course, the kiwi example. I personally think this might be more likely, but perhaps therizinosaurs only grew vaned feathers during the "rut" or the mating season, using them to impress the opposite sex, or at some other time, and then shed them and resorted to a more drab plumage the rest of the year. Not able to fly, run particularly fast, or climb trees like other maniraptorans, having bright vaned feathers would be a hindrance for therizinosaurs, and those that only had them at some points of the year would survive. Of course, this is still just a theory. But then again, deer do grow massive antlers during the rut, and then lose them in winter. If we only found female deer and those who had lost their antlers, we would probably be wondering what the heck was going on there too!
I think the possibility of integumentary structures in non-coelurosaurian ornithodiran dinosaurs has been given too little attention. While it is obvious that dinosaurs like sauropods and hadrosaurs did not have feathers all over their body, I wouldn't be too sure to say they didn't have feather manes, as often portrayed by Luis V. Rey. After all, integumentary structures have been found in theropods (coelurosaurian dinosaurs), ceratopsians (Psittacosaurus and possibly Triceratops), and pterosaurs (Sordes and Jehol pterosaurs, among others). So why is it so hard to believe that the common ancestor of these animals (basal ornithodirans) didn't have proto-protofuzz of their own. In fact, if Longisquama turns out to be a basal ornithodiran, those weird scales might turn out to be a derived form of scale-like proto-protofuzz. Ironically, this would make Longisquama a cousin of the birds, just not how the "Birds Are Not Dinosaurs" people constantly claimed.
Good points there, thanks. On the distribution of integumentary structures in ornithodirans, it has been informally suggested that such structures as the dermal spines of diplodocoid sauropods might be homologous with theropod feathers (thanks to George Olshevsky for this one). Not testable and highly speculative, but not beyond the realms of possibility.
Interesting. It would not also be outside the realm of possibility that larger theropods, such as Allosaurus and Tyrannosaurus, had some sort of feathers as adults; whether it be polar species covered in fluff, or around the head and neck as display structures. The reason why other theropods that are known, such as abelisaurs, do not have feathers, is because they are firstly descended from ancestors that are hypothesized by some to be semi-aquatic (Ceratosaurus, seeing as it is the best non-abelisaur ceratosaur known), and the fact that it was probably very arid and warm in Cretaceous South America. But again, this is just postulating.
However, there is NO way therizinosaurs are derived ornithiscians, as some have suggested before the discovery of more complete species. Their hips are more suggestive of a maniraptoran (or perhaps basal maniraptoran) affinity, and their hands are very maniraptoran. I mean, as far as I know, there are no four fingered reaper dinosaurs out there.
It would also be interesting to see if the structures on the neck and back of diplodocus are indeed feathers. I would also say it raises the possibility that the spines on amargrasaurus are ossified feathers, but I assume that the spines are derived from some process on the vertebrae (I need to read more SV-POW!)
Another interesting possibility is that the feathers on the dinosaurs we do not currently have them in did not fossilize, and are more like the feathers of parrots. The paleontologists of the future would probably assume that parrots were scaly because their feathers are fragile and do not fossilize. Hopefully actual parrots will be around to prevent something like that from happening.
Wonderfull! this is why I check this blog three times a day, hoping against hope for a litttle dino treat from your table Darren. Thanks!!!
"I mean, as far as I know, there are no four fingered reaper dinosaurs out there."
Therizinosauroids have three digits, not four.
A lovely case of WFTP, and we may well see that therizinosauroids are more basal than other maniraptorans... :)
"The reason why other theropods that are known, such as abelisaurs, do not have feathers, is because they are firstly descended from ancestors that are hypothesized by some to be semi-aquatic..."
We do NOT need an Aquatic Theropod Hypothesis! Penguins, ducks, geese, even and especially tropical water fowl haven't lost their feathers because they get wet.
Next thing you know, we'll be hearing about the books Descent of a Hen and Hatchling.
I find your blogs on new finds very useful as anything from a news body (BBC etc) merely misreports the data or says very little beyond what a 5 year old would understand and the DML is often hard to follow, random and requires you to actually have access to the papers. Your style is both understandable, accurate and sensibly opinionated. Cheers.
At SVP last year, Zanno presented evidence, based on Falcarius, that therizinosaurs were the basalmost maniraptors and did not sit with oviraptors, too. So are the therizinosaur "quill" feathers elongated compy feathers, or are they totally different?
I'm not a big fan of the homology idea. The psittacosaur quills look more like porcupine quills than feather quills, and pterosaur fuzz is more like mammalian hair than feathers, isn't it? And then there's the scaley skin problem. A feathery coat implies smooth birdlike skin, right?
Metalraptor: Near-toothless pygostyles? How is that even possible?
(The Englese, she is the very difficult language to speak.)
It is interesting to note that, actually, there are not mid- to large sized ornithodirans bearing feather remains (Beipiaosaurus and Sinocalliopteryx are the largest known forms with non-scaly tegument preserved): given that feathers (and feather-like structures) are preserved only in limited taphonomic conditions, our knowledge of tegumentary diversity among dinosaurs could be distorted by a "taphonomic" bottleneck.
No chance. Probably it's not even a crown-group diapsid (in other words, the lizards are closer to the birds than Longisquama is).
Impossible -- feathers, like hairs, are just keratin that sticks out of the skin. The spines of Amargasaurus are simply the neural spines.
Nope. Phylogenetic Bracketing: parrots are derived birds, and thus inside a clade that is known to (whenever the integument is known) bear feathers. It follows that parrots either have inherited feathers from a feathered ancestor, or have lost the feathers; the latter possibility requires an extra event and is therefore less parsimonious -- less scientific.
I don't think that's actually known.
"Metalraptor: Near-toothless pygostyles? How is that even possible?"
Near toothless: Oviraptors, for some odd reason, had few to no teeth in their skull. However, they had powerful beaks, so they didn't exactly need teeth now did they?
Pygostyle: A lump of fused caudal verts at the end of the tail, which are usually the base of large display or flight feathers. In oviraptorosaurs that have this it is assumed to be the former.
"Impossible -- feathers, like hairs, are just keratin that sticks out of the skin. The spines of Amargasaurus are simply the neural spines."
That's why I said I might say that, but I thought they were derived spinal processes. Please don't quote me out of context.
"Nope. Phylogenetic Bracketing: parrots are derived birds, and thus inside a clade that is known to (whenever the integument is known) bear feathers. It follows that parrots either have inherited feathers from a feathered ancestor, or have lost the feathers; the latter possibility requires an extra event and is therefore less parsimonious -- less scientific."
So, whales are fully decked out in air-trapping fur like sea otters? I never knew that! (note: sarcasm)
We do NOT need an Aquatic Theropod Hypothesis! Penguins, ducks, geese, even and especially tropical water fowl haven't lost their feathers because they get wet.
Next thing you know, we'll be hearing about the books Descent of a Hen and Hatchling."
I wasn't saying all theropods. Firstly, I was only talking about the Abelisauroidea and its relatives, NOT the rest of theropoda. The reason I suggested this is because the one well known Ceratosaurid, Ceratosaurus, has been suggested to be semi-aquatic by some, due to anatomical features. Large aquatic animals often have a lack of hair or proto-fuzz, look at whales. But still, the Ceratosaurids are poorly known, other than Ceratosaurus proper. And new evidence could throw off old ideas. For example, I have heard rumors of new Middle Jurassic abelisaurs and ceratosaurs somewhere, but I don't know if there's any truth to them.
It is interesting to note that, actually, there are not mid- to large sized ornithodirans bearing feather remains (Beipiaosaurus and Sinocalliopteryx are the largest known forms with non-scaly tegument preserved): given that feathers (and feather-like structures) are preserved only in limited taphonomic conditions, our knowledge of tegumentary diversity among dinosaurs could be distorted by a "taphonomic" bottleneck."
I agree with you entirely.
"I'm not a big fan of the homology idea. The psittacosaur quills look more like porcupine quills than feather quills, and pterosaur fuzz is more like mammalian hair than feathers, isn't it? And then there's the scaley skin problem. A feathery coat implies smooth birdlike skin, right?"
Porcupine quills are derived from hair.
"Therizinosauroids have three digits, not four."
Once again, sarcasm
I'm going to be a huge tease. Darren (and readers), I can probably fill at least one of those 'blue gaps' for you from the IVPP - but I can't talk about it in public, sorry. ;-)
Where'd you get the long-veined Greg Paul illustration of Sinornithosaurus in the cladogram? I've never seen that before....
Zach, is that the beastie that's second from the right? I believe that's from Dinosaurs of the Air.
"Metalraptor: Near-toothless pygostyles? How is that even possible?"
Didn't you read the SV-POW about mamenchisaur tail clubs? ;)
Aargh! It says "near toothless beaks and pygostyles"! Oviraptorosaurs are known for having nearly toothless heads, except for primitive species like Incisivosaurus. The only thing that advanced species have in the way of teeth is a pair of fangs in the mouth, which were originally suggested to be used as egg eating tools, but now their status is in doubt. They could be egg eating tools, but they could also be used to crack open shellfish or nuts, or used like peccaries or pigs use their canines; for display and intraspecific combat.
Furthermore, the Oviraptor Nomingia is known to have a bird-like pygostyle, a lump of fused verts at the end of its tail used to support large, vaned feathers. Seeing as there is no evidence yet that oviraptorosaurs actually flew, it appears most likely that this supported a display structure, like a peacock's tail. Even odder is the fact that both of these traits are derived independantly of birds, birds themselves losing their teeth and gaining a pygostyle independantly.
Surprisingly, there might actually be something behind your mamenchisaur tail club thing. While many people (myself included) think that the club was a weapon, there is always the off chance it was a decoy based to lure predators away from the real head. A sinraptorid would come up to the tail, wondering "is that thing on the end a head?" And then, WHACK, the "head" smacks them upside the head.
As long as we don't have evidence to the contrary -- which we have; whales are 1) observable and 2) aquatic like sea cows (even hippos are pretty much naked) --, the most parsimonious and therefore preferable hypothesis is indeed that they retain the fur. It's just that falsification trumps parsimony.
Not by "some", by Bakker, who also considers spinosaurs "ocean-going" for (presumably) some reason, and AFAIK by nobody else; and the anatomical features that are compatible with some degree of tail-based swimming are considerably less numerous than the ordinary running adaptations. I'm not saying it didn't catch one of those mega-lungfish when it got the opportunity; I'm saying it probably didn't live off such pursuits.
And these are bony projections, not teeth.
Many thanks to all for comments. A select few responses...
Dave Hone said...
Whatever you're referring to, it sounds neat. But the point above is that the 'blue gaps' have already been filled now: we have a fully feathered troodontid (Jinfengopteryx), and evidence for vaned feathers in non-unenlagiine, non-microraptorine dromaeosaurs. That only leaves therizinosauroids, and as discussed here, it seems that they don't have vaned feathers at all.
Moving on... the resplendently feathered Greg Paul sinornithosaur is an updated version of the drawing from Dinosaurs of the Air. It appeared in...
Paul, G. S. 2003. Screaming biplane dromaeosaurs of the air. Prehistoric Times 60, 48-50.
This article includes a few drawings not reproduced elsewhere. One shows a sinornithosaur attacking a psittacosaur, another has two sinornithosaurs fighting while in flight (Paul maintains that sinornithosaurs could fly).
"fully feathered troodontid Jinfengopteryx".
Bugger, I forgot that, I still remember it as an avialian, which of course it almost certainly isn't. Also this comment largely gives away at least in one aspect what I was referring to.
Sorry misread your original post. My bad. But yes, there *is* something interesting on the horizon from China wrt feathers and maniraptorans.
I hope nobody is using the hypothesis discussed in my blog, that Majungasaurus was more adapted to amphibious life-style than other abelisaurids, as a support for an "Aquatic Whole-Ceratosauria"... Please, don't do that! My hypothesis was not a re-Bakkerian idea, but was based on the distribution of character conditions among abelisaurids, that seem to support the hypothesis that tail and hindlimb of Majungasaurus were ex-/ad-adapted for a partially amphibious lifestyle, absent in related forms.
But, it's only a suggestion (although, I'm collecting additional data...).
Ha - I knew it! Well, when you publish on a fully feathered Liaoning troodontid, I at least will pretend to look surprised :) Seriously, good luck with it.
Ceratosaurus has several features which point to it being more habitualy aquatic than other Morrison theropods. The feet and toes are long, similar to those of birds which frequent wet and watery areas. The tail is long, powerful, and flexible, especially compared to the other theropods that shared its environment (who were tetanurans). The teeth of Ceratosaurus, when a survey was done (yes, by Bakker) showed that most shed teeth were found in aquatic environments. There is other things, but I'll have to get back to you on that...
As for Ceratosaurus being aquatic, I said semi-aquatic, not obligate-fish-eater. Remember, that even today, few carnivores are picky about their diet, and just because an animal lives in a habitat doesn't mean it feeds exclusively on that areas most common food source. Look at the modern American alligator, who does eat fish, but also takes mammals, birds, and on occasion even plant matter. Or on the other side of the archosaurian family tree, the bitterns and falconiforms of the Everglades. While bitterns do feed on fish, they also eat insects, amphbians, and reptiles. And while some everglades hawks and falcons, like the osprey or bald eagle, do specialize in fish, many others feed very little on fish and instead eat small mammals.
While we cannot go back in time (yet) and record the percentage of what is what in Ceratosaurus' diet, the evidence seems to suggest it was a wetlands or riparian predator, and was at least habitually aquatic. Its diet did probably include a lot of crocs, lungfish, and other fist, but I don't think it would have passed up the chance to attack a small ornithopod or juvenile stegosaurus when it spotted one. Finally, I am not saying that all ceratosaurs were possibly semi-aquatic, just Ceratosaurus. You're a fool if you think that Carnotaurus was not an animal built for the land.
As for spinosaurs, yes, they were aquatic. I don't know about ocean going for sure, but they were definitely aquatic. Their teeth are conical and thin, and their snouts are long. The animals that have this sort of head today are predominantly fish eaters (crocodilians, dolphins, etc). While it might have also scavenged or occasionally killed small dinosaurs (as inferenced by the remains of a juvenile iguanodon inside the stomach of the holotype of Baryonyx), the majority of spinosaur's diet was definitely fish and marine reptiles.
"whales are 1) observable"
Sorry, but it appears that non-avian theropod dinosaurs are extinct.
"No chance. Probably it's not even a crown-group diapsid (in other words, the lizards are closer to the birds than Longisquama is)."
Longisquama has an antorbital fenestrae and a mandibular fenestra...
"I'm going to be a huge tease. Darren (and readers), I can probably fill at least one of those 'blue gaps' for you from the IVPP - but I can't talk about it in public, sorry. ;-)"
bet its some form of dromaeosaurid...
Dave could also mean someone's finally found an Ornithomimid/Ornithomimosaur with integument. That would be very cool, particularly if something other than the expected fuzzy protofeathers were found.
Karl: the 'blue gaps' on the cladogram only depict maniraptorans so, no, Dave wasn't referring to an ornithomimosaur. However... you're right that it's only a matter of time before a fuzzy/feathery ornithomimosaur turns up at Liaoning (Shenzhousaurus doesn't seem to preserve any integument). Pelecanimimus does preserve fibre-like structures that could be integumentary fibres, but no one has yet looked at them closely enough to work it out. For the background to all this please see the ornithomimosaur article here and the 'feathers and fibres' article here.
Ahh Darren, I see you're right. Shame on me for not being more perceptive. I have a hard time reading your diagrams - I have a very high screen resolution and your photos are always so small, and I just looked at it fast and assumed it showed integument for all Coelurosauria, not simply Maniraptora.
What is that at the base of your cladogram? Caudipteryx? Pedopenna? I can't make out the name at all.
Karl, sorry about the small image size: that diagram was designed as a powerpoint slide, plus I'm constrained to a maximum image width of 500 px. The animal at bottom left is Luis Rey's alvarezsaurid. You can see a bigger version here, or on p. 138 of Tom Holtz's outstanding Dinosaurs, reviewed here.
The labels on the cladogram are as follows (from base to tip, with names 'on branch' marked with *): Maniraptora*, Alvarezsauridae, Oviraptorosauria, Therizinosauroidea, Eumaniraptora*, Aves, Deinonychosauria*, Troodontidae, Dromaeosauridae*, Unenlagiinae, Microraptoria, Dromaeosaurinae.
So far, the only blue groups on the cladogram are the families Troodontidae and Dromaeosauridae, and the superfamily Therizinosauroidea. Members of Troodontidae with vaned feathers have been found (Sinovenator and Jenfengopteryx, among others). As for Therizinosauroidea, so far they appear to only have dino-fuzz rather than feathers (but you never know). The only group we know of left in the cladogram pictured above that is inferred to have vaned feathers, but the feathers themselves are not preserved, is the family Dromaeosauridae. As for myself, I too would be interested in a feathered ornithomimid. For some reason, paleoartists refuse to give the animals a feathery coat as they have other coelurosaurs (and I thought Shenzousaurus did have feathers?)
I'm sorry, did somebody say feathered diplodocids?
I learned how to read out of the Big Golden Book of Natural History, in which Diplodocus was painted as the bastard offspring of a salamander and the great, gray-green, greasy Limpopo River. Next thing I knew it was standing up straight, then somebody adjusted its neck (finally, after millions of years--wow, that has to have ached!) and when one strolled into view on Walking With Dinosaurs with its bizarre forest of whatsits growing along its spine, I turned to my husband and said, "I never thought much of Diplodocus, but look at that thing--it's almost spooky." And now its spinal ornaments may be feathers, or related to feathers? Truly we live in strange and wondrous times.
Then why does its skull, especially the teeth, look so tyrannosauroid? Wouldn't we expect something more torsion-resistant, like a spinosaur skull?
They clearly fed on aquatic prey, but that doesn't make them aquatic. Herons don't count as aquatic either; they just stand in the water, they don't swim.
No, these are almost certainly misinterpretations of breaks in the fossil.
Yes, that's a difference between them. For what they have in common, see the second point.
You can't put something bigger into a blog post, but you can still upload bigger images to ScienceBlogs and provide a link in a post. PZ does that all the time.
Soft parts don't get preserved in the river sediments that make up the lower part of the Yixian Fm, which is also where Incisivosaurus (isolated skull) and the family of 35 Psittacosaurus (complete skeletons and nothing else) come from.
Actually, the point I tried to make is a very different one: I tried to explain the conditions that trump phylogenetic bracketing. PB is for inferring a character state in the absence of direct evidence; direct evidence (such as observation of whales) is a condition that trumps PB. Another is functional morphology: several aquatic mammal clades have lost their fur, so whales can, with a significant probability, be assumed to have done the same. PB comes with an "all else being equal" disclaimer.
"They clearly fed on aquatic prey, but that doesn't make them aquatic. Herons don't count as aquatic either; they just stand in the water, they don't swim."
Pelicans also have a very spinosaur-like skull, albeit minus the teeth. Animals that tend to have spinosaur-like skulls (remingtonocetids, crocodilians, pelicans, etc.) all swim in the water after their food. Also please note that spinosaurs have long, powerful tails, which could be effective swimming aids.
Of course, the point could be overall moot, and we could both be right. Spinosaurs could have done all of the above, scouring the seashore for carrion, seabirds, seadactyls, and such; wading in the water to spear fish and small marine reptiles with their claws, and diving into shallow waters after fish and marine reptiles as well.
"Then why does its skull, especially the teeth, look so tyrannosauroid? Wouldn't we expect something more torsion-resistant, like a spinosaur skull?"
The teeth do not look tyrannosauroid. T-rex teeth are thick around and look like stakes. Ceratosaurus teeth are thinner and blade-like. If any theropod in the Morrison filled a tyrannosaurine tyrannosaur-like niche, it was the megalosaurs like Torvosaurus.
Nope, they don't. "Tetanurae" means "stiff tails". Stiff and rather thin throughout the rear half of the length of the tail, and pointy at the end rather than rounded like in crocodiles.
We are looking at an animal with ordinary theropod proportions, for example long legs which could have been used for wading.
Just today a poster was presented (I'm currently at this congress) showing that when spinosaurs open their jaws, the left and right lower jaws splay apart, so the spinosaur can swallow bigger prey. Think pelicans... and herons.
1) You can't tell from a skull if the animal swam.
2) Pelicans don't swim that much, actually. They mostly sit around on top of the water.
Good point. The only similarity is the unusual length.
Ironically, I wouldn't use blade-like teeth to bite on a lungfish. I'd use tyrannosaur or spinosaur teeth. Have you seen the scales of these animals?
Oops, please ignore the (wrong) link. I'm in Brussels, at the Darwin-Bernissart meeting, which is a special meeting of the European Association of Vertebrate Palaeontologists.
Sounds fun, David. I'd love more detail on the spinosaur poster. What causes the jaws to splay apart? And does the author (authors?) comment on its paleoecology? What spinosaur(s) did they use?
Zach: David is almost certainly referring to Christophe Hendrickx's work, previously mentioned here on Tet Zoo. Apologies in advance if I'm mistaken.
I would not use tyrannosaur teeth to bite on fish. The teeth would just batter the fish, and not hold onto it that well.
Plus, herons and other birds who wade and spear fish have a very long, pointed skull. Those who tend to swim out after fish have a longer snout, with a widened end. This includes species that feed on fish, like pelicans, as well as other species that swim out and dabble, like ducks. Also please note that spinosaurs could not have snagged fish in the exact same way as herons, because herons and similar birds, like the anhinga, spear their prey with their beaks themselves. While spinosaurs did have a mouth full of sharp teeth, they could not have speared it with their teeth. Their claws maybe, but not their teeth.
Pelicans do go out in the water after fish. Yeah, they do sit around on the surface a lot, but I'm saying they don't just wade in the water. You also cannot tell by the skull that an animal did not swim. However, it appears that by the way that spinosaurs appear in their local ecology, it would seem that they would go out into shallow waters to hunt fish. Look at the Early Cretaceous of Africa, there are numerous predators on the land, such as carcharodontosaurids, abelisaurs, and noasaurids. If all of these animals were able to coexist in some way, like how cheetahs, lions, and jackals do on the African savannah, it could be assumed that each of these animals differ in some way in their niches. And the bodies of spinosaurs suggest that they were aquatic, and ate fish.
And there are other ways and reasons to use a ceratosaur's blade-like teeth on lungfish and crocs. For example, using the powerful forelimbs of a ceratosaur to drag a croc or a lungfish out of the water, and then cut into the soft underbelly and other vulnerable parts with those wicked teeth.
Yep. How it works is that the jaw joint surface is screw-shaped, which somehow (I haven't checked how) causes the halves of the lower jaw to splay a bit apart when the jaw is opened; the quadrates themselves do not move in the process. The abstract of the poster follows:
Christophe Hendrickx & Ãric Buffetaut: Morphofunctional analysis of spinosaurid quadrates, p. 55 in Pascal Godefroit & Olivier Lambert (eds.): Tribute to Charles Darwin and Bernissart Iguanodons: New Perspectives on Vertebrate Evolution and Early Cretaceous Ecosysstems -- Brussels 2009 -- Programme, Abstracts and Field Trips Guidebook
"Five quadrates from the Early Cenomanian of the Kem Kem area (Morocco) are determined to be from juvenile and adult spinosaurids. Their morphology indicates two morphotypes and reveals the presence of two different taxa of spinosaurids in this site. Morphofunctional analysis of quadrate bones and their mandibular condyles has showed that the mechanics of the lower jaw of spinosaurids was [sic] specialized. The posterior parts of the mandible [were] displaced laterally when the jaw moved downwards thanks to a [sic] helicoidal shape of the mandibular articulation of the quadrate. Such a lateral movement of the rami was also possible thanks to a weak and short mandibular symphysis and allowed the pharynx to be widened. This jaw mechanic [sic] is present in some ornithocheiroid pterosaurs and living pelecanid birds, which are both adapted to piscivory and to swallowing large fish. Spinosaurids which were engaged in at least a partially piscivorous lifestyle were able to consume large fish and may have fed occasionally [on] other prey such as pterosaurs and juvenile dinosaurs."
For what it's worth, Christophe (pers. comm.) agrees with the heron analogy.
And such a widened end is not seen in spinosaurs (though not in gharials either).
Correct. Together with the simple size difference, I bet this explains the differences in skull shape between herons and spinosaurs.
To the contrary.
Lungfishes have no soft underbelly. No sarcopterygian which retains a serious scale cover has a soft underbelly, derived branchiosaurs and two or three other temnospondyls excepted. Lungfishes have big, hard scales all around their bodies.
(Yesterday there was a field trip to the Late Devonian locality of Strud, where a scale of a porolepiform (close relative of the lungfishes) has been found that is 10 cm in diameter.)
Crocodiles don't have a soft underbelly either. They have ventral osteoderms, too. Few aquatic animals that have any armor can afford a soft underbelly.
Incidentally, I was invited to speak at the Brussels meeting (on Lower Cretaceous theropods). Baby-issues meant that I had to say no, dammit.
"...it has been informally suggested that such structures as the dermal spines of diplodocoid sauropods might be homologous with theropod feathers (thanks to George Olshevsky for this one). Not testable and highly speculative, but not beyond the realms of possibility."
First, âspeculativeâ. There are times when we do need high confidence that something happened - we donât want to jail someone who just âmightâ have committed a crime.
But before that stage, as when police are still investigating a crime, each avenue explored does not need evidence for it before it is explored! How could it, when so often you need to consider a possibility before you can find evidence for it! This sort of thing has been academically well understood and handled for decades in disciplines dealing with search, which dinobirders can happily pretend donât exist because they donât know anything about them and no-one in their social group - âreal people who actually countâ - does either. In dinobird theorising we are still very much at the stage of considering all possibilities.
Never mind elementary philosophy of science - making sure we donât treat a possibility that is still wide open as if it were a proved falsehood is just a basic thinking skill.
The facile rhetorical ploy of simply chanting âspeculativeâ only became accepted because some discussions are at the stage where it is important that we are sure of something. More often though, the discussion is at the earlier stage, where no possibilities and influences should be rejected, and the accusation is totally inappropriate.
âTestableâ. What if we had a perfect sequence of animals that allowed us to generate a phylogeny we could all agree on? Say we found a handful of rich fossil deposits that illustrated all the crucial groups evolving amongst themselves and preserving soft tissues. Or say we analysed the DNA of extant archosaurs and discovered the age of certain genes that produced structures in the pterylae of crocs and birds. These and any number of alternatives could easily refute Olshevskyâs idea, and youâre a million miles away from demonstrating that nothing could ever disprove it, or any number of other ideas commonly and wrongly branded as âuntestableâ.
Of course, this whole âuntestableâ accusation is thrown by dinobird palaeontologists at any proposition that doesnât come out of a cladogenesis program - ironic since cladograms test nothing. The litmus test produces one observable output if one theory is true and another if an alternative is true. But if my theory of dinobirds is true, or yours, the same cladogram would be produced. It therefore doesnât distinguish between the theories and is therefore not a test. Unfortunately, since instead of producing some anodyne output such as simply changing colour, a cladogram actually gives an explicit detailed description of a possible theory, which easily confuses some people, but since it would do the same for multiple theories, it doesnât matter what the cladogram actually says, or how many people misunderstand its significance. A further irony is that that suggestions that a theory is untestable or speculative tend to carry the veiled implication that the theoryâs supporters have failed to understand some important aspects of the philosophy of science, whereas, for the reasons given above, the implication points firmly back at the accuser himself, who usually shows simply by the concepts and significant theorisers he fails to mention that he is not well-versed in the subject area.
I would like to appeal to someone like John Maynard Smith to help us resolve this, just as Woody Allen pulled Marshall McLuhan out of the cinema queue, but JMS has now joined the unemailable majority. However, I did once ask him âWhatâs the most devastating thing you can say to a creationist?â and he said that their theory wasnât testable. When I suggested that evolution wasnât either, he gave the example of a fossil rabbit in the Precambrian. Iâm sure he would enjoy finding tests for most theories within evolution as much as he did for the whole theory itself. Later of course I realised I should have replaced âcreationistâ with âcladistâ, so I effectively asked him the adjusted question, and Iâm pleased to say that like most true experts he had much the same view as me.
As you say though Darren, Olshevskyâs theory is not beyond the realms of possibility, and I appreciate your drawing attention to it. But those two words donât need to be mentioned as they put both you and the idea in an unnecessarily bad light.
But...sauropod spines are bony...right?
john jackson: what a long tedious waffle. it IS speculative and non-testable, at this stage, to claim that sauropod spines are homologous with protofeathers. End of discussion.
Have you ever heard of the principle of parsimony, sir?
Indeed not. They show which hypothesis is most parsimonious.
Aren't you the one non-Russian who believes in bird diphyly? If so, no cladogram would be compatible with that, unless perhaps if the data matrix was made in a very selective way.
There's an exceptionally well-preserved and more or less unpublished part of a diplodocid out there that has keratinous spines.
[from Darren: delayed by spam filter. Note that more than one url automatically puts a message into spam. Please note also that long urls don't work on the Sb platform - use tags to embed]
&ei"(Paul maintains that sinornithosaurs could fly)."
Thank you. (Dave cf. Hone blocked my comments to his blog with the farewell message that I was the only one who thought Dave cf. Sinornithosaurs could fly.) Iâve never seen a counterexample in modern birds to the rule that types with upper arm longer than the shoulder joint to hip joint distance can fly and other types canât. Roadrunner just obeys the rule; some big dromaeosaurs which clearly couldnât fly as adults have elbows just about halfway, and Sinornithosaurusâ elbow is clearly in the flying zone:
Roadrunner: p148 of DA (TZ readers probably have it but if not youâll want it).
Google books version: scroll up a bit from here.
To compare that with Sinornithosaurus, open a second window with that url and use the bar up the side to find the top illustration on DA page 13 (may take a minute to appear).
" "fully feathered troodontid Jinfengopteryx".
Bugger, I forgot that, I still remember it as an avialian, which of course it almost certainly isn't. Also this comment largely gives away at least in one aspect what I was referring to.
Sorry misread your original post. My bad. But yes, there *is* something interesting on the horizon from China wrt feathers and maniraptorans."
That last sentence is going to be true for the forseeable future. Nice to know weâve got a good man on the spot to tell us what it all means.
"Herons don't count as aquatic either; they just stand in the water, they don't swim."
, click on âsightings 2005â and search in your browser for âswimming Grey Heronâ.
Towards the end of: http://www.gobirding.eu/Photos/GreyHeron.php
OK, so they donât let their long necks topple them over, but they still lack oil glands and go the powder feathers route, so swimming is a bit surprising. I wonder if oil-gland-less frigate birds really canât swim? Google suggests not.
"what a long tedious waffle."
Sorry but there's a lot of rubbish to be cleared out, and I didn't put it there.
"it IS speculative and non-testable, at this stage, to claim that sauropod spines are homologous with protofeathers. End of discussion."
Well if you're leaving the discussion, fine. It isn't any more untestable than almost anything else in dinobird palaeontology, and half of science is speculation.
"Aren't you the one non-Russian who believes in bird diphyly?"
I don't believe in bird diphyly, and I didn't read any other bits of your comment. However, you might like to consider that when a new theory arrives there is at one stage only one person who believes it, and it stays in a minority until it becomes a majority, so counting heads doesn't help much.
Thanks, so herons do occasionally swimâ¦ still, they don't do it regularly, for a living. I'd be surprised if spinosaurs were completely incapable of swimming; still, I don't think they did it regularly, for a living.
Wow. You actually make an argumentum ad hominem. I wouldn't have believed that. :-o
What is your hypothesis like? Obviously I either misremember it, or we talk past each other because we don't use the term "bird" the same way, so please set me straight.
Yeah, sure, but why isn't that stage showing any signs of ever ending? It's been over 10 years since Kurochkin published.
Not quite sure how many people read late comments to older threads, but anyway...I wonder if anyone else is reminded of the Womble song:
He can fly
He can SWIM
He's a Hero[n]
:-) (My "[n]" of course.)
The next line... "He's got X-ray eyes!" rather overstates the allowance they famously make for diffraction.
But then there's this:
Just found this old thread, sorry to post and be petty but... I did NOT block John Jackson from commenting on my blog. I DID ask him to stop posting unverifiable nonsense based on his misunderstanding of cladistics. Not quite the same thing and I wanted to clarify this since he announced it here, though he did stop which was what I wanted.