The idea that non-avian dinosaurs might have been able to climb trees is (I assume) not all that familiar to people outside the field of dinosaur research, but within the field of dinosaur research it has become an increasingly familiar idea within recent decades. Thanks to the discovery of such theropods as Microraptor and Epidendrosaurus, we do now have small forms exhibiting some features suggestive of a tree-climbing (or scansorial) way of life. Perhaps surprisingly however, the idea that dinosaurs might have climbed trees goes back a long way, and well pre-dates the dinosaur renaissance of the 1960s and 70s...
Rightly or wrongly, the idea of scansoriality in non-avian dinosaurs has been considered a 'fringe' idea, and it's partly for this reason that, prior to 2000, nobody had attempted any sort of review on the thoughts that had been published about the subject. As someone interested both in 'fringe'/'non-standard' theories and in Wealden theropod dinosaurs, I had the opportunity during the late 1990s to do something about this, and I published two articles on the subject (Naish 2000a, b) and even gave a conference presentation on it (the special relevance that Wealden theropods have for this subject will become clear in a moment). The more formal of my articles was published in the journal Archaeopteryx, a venue I chose because it seemed like an appropriate one for this sort of paper (back in those days we didn't worry about such things as pdf availability, online access or impact factors... at least, I didn't anyway). The problem with this otherwise fine idea is that Archaeopteryx is very hard to get hold of, and its contents often remain all but unknown to the majority of researchers. I asked Greg Paul, for example, why he didn't cite Naish (2000a) in Dinosaurs of the Air, and he told me that he would have done had he been aware of it [image below is Gerhard Heilmann's 'fighting proaves' reconstruction. Note the trunk-climbing 'proaves' in the background. From Early Bird].
The oldest reference to scansoriality in a dinosaur that I was able to find came from William Fox, the Isle of Wight curate and amateur fossil collector, who in 1866 proposed that Calamospondylus oweni from the Lower Cretaceous Wessex Formation of the Isle of Wight might have been in the habit of 'leaping from tree to tree' (Fox 1866). The Calamospondylus oweni specimen that Fox was writing about now seems to be lost, and hence we can't be sure what type of animal it was, but there are various reasons for thinking that it was a theropod (Naish 2002). However, it's not entirely accurate to regard Fox's ideas about Calamospondylus as directly relevant to modern speculations about tree-climbing dinosaurs given that, if Fox imagined Calamospondylus oweni as resembling anything familiar, it was probably as a lizard-like reptile, and not as a dinosaur as they are currently understood.
During the early decades of the 20th century the idea of tree-climbing dinosaurs became reasonably popular as Othenio Abel, Gerhard Heilmann and others used comparisons with birds, tree kangaroos and monkeys to argue that the small ornithopod Hypsilophodon (also from the Wessex Formation of the Isle of Wight) was scansorial. Heilmann produced some beautiful life restorations of tree-climbing hypsilophodonts, though by the time he wrote his seminal The Origin of Birds in 1926 (first published in 1916 as Vor Nuvaerende Viden om Fuglenes Afstamning) he had come to disagree with this idea and now regarded Hypsilophodon as terrestrial. Anyway, William Swinton favoured the idea of a scansorial Hypsilophodon, concluding that 'it would be able to run up the stouter branches and with hands and tail keep itself balanced until the need for arboreal excursions had passed' (Swinton 1936a, p. 577), and in a 1936 review of Isle of Wight dinosaurs mentioned the idea that small theropods might also have used their clawed hands to hold branches when climbing (Swinton 1936b).
During the 1970s, Peter Galton was able to show that all of the claims made about the forelimb and hindlimb anatomy of Hypsilophodon supposedly favouring a scansorial lifestyle were erroneous, and that this animal was in fact well suited for an entirely terrestrial, cursorial lifestyle (Galton 1971a, b). Nevertheless, for several decades Hypsilophodon was consistently depicted as a tree-climber, and even people my age (early 30s) will recall reconstructions whereby small ornithopods were shown poised in trees, opposable hallux gripping the branch like a thumb, and sometimes pictured alongside hypothetical proto-birds (as shown here).
Deinocheirus the slothosaur
Something else very interesting happened during the 1970s. An entirely new dinosaur was brought into the tree-climbing story: the immense Late Cretaceous coelurosaur Deinocheirus mirificus, known only from its arms and shoulder girdles (and from a few ribs too). Generally imagined as a gigantic ornithomimosaur (ostrich dinosaur), Rozhdestvensky (1970) proposed that Deinocheirus was a sloth-like climbing form with shortened hindlimbs. I'm reliably informed that Rozhdestvensky even went so far as to produce a reconstruction of a sloth-like Deinocheirus clambering about in a tree, but I couldn't find this in the literature and ended up creating my own hypothetical climbing Deinocheirus (Naish 2000b).
Given that Deinocheirus has been estimated at between 6 and 12 tons (its arms were about 2.4 m long), it seems unlikely to say the least that it really was a climber. Admittedly, these mass estimates assume that it was built like the ostrich dinosaurs we know of from better remains, whereas if it was the short-legged slothosaur that Rozhdestvensky imagined it may well have weighed much less. However, there's no reason at all to take such an idea seriously and it's a grotesque speculation unsupported by evidence. In support of the climbing hypothesis, Rozhdestvensky pointed, not only to the large claws and sloth-like forelimb proportions, but also to the fact that the palms of Deinocheirus must have faced inwards (we now think that this configuration was common to pretty much all theropods). He also proposed that Deinocheirus had a small, lightly constructed skull, and that it might have fed on fruits and leaves 'and also, possibly, on the eggs, or even nestlings both of birds and pterosaurs nestling [sic] in trees, or on any other small animals' (Rozhdestvensky 1970, p. 123). Furthermore, when out of the trees and walking on the ground, he imagined that 'these dinosaurs must have walked relying on their long forelimbs - more precisely, on the hind part of the hand, as do the sloths' (Rozhdestvensky 1970, p. 124).
In one of the first analyses of theropod forelimb function, Osborn (1917) had noted that the forelimbs of the ostrich dinosaur Struthiomimus superficially resembled those of two-toed sloths, and this led him to propose that they were used for 'drawing down the smaller branches' while foraging. Osborn's paper included comments from William King Gregory: Gregory considered the possibility that the sloth-like arms might indicate a climbing habit, but he concluded that Struthiomimus couldn't really be a climber because it was too big, and with hindlimbs suited for terrestrial running, not for climbing (Osborn 1917). This all sounds pretty sensible. However, Rozhdestvensky (1970) chose to take notice of the forelimbs alone, and proposed that ostrich dinosaurs like Struthiomimus were climbers after all, which doesn't seems at all likely given their ratite-like hindlimb anatomy. Nevertheless it was resurrected by Chatterjee (1997). More on Chatterjee's scansorial theropods in a minute.
Hypothetical little climbers
In recent decades, Greg Paul has been undoubtedly influential in arguing that small theropods were capable climbers, and he not only argued for and illustrated scansorial abilities in coelurosaurs (Paul 1988: an Ornitholestes climbing in a tree is illustrated therein), he also proposed that as-yet-undiscovered maniraptorans were highly proficient climbers and included the ancestors of birds. The hypothesised existence of small arboreal theropods that are as yet unknown from the fossil record later proved integral to George Olshevsky's 'birds come first' (BCF) hypothesis (Olshevsky 1991, 1994, 2001a, b). Olshevsky argued that all dinosaurs, and in fact all archosaurs, descend from small, scansorial ancestors, and that it is these little climbing reptiles which are the direct ancestors of birds.
The existence of hypothetical scansorial dinosaurs was also proposed by Nessov (1995) who thought that therizinosauroids - the mostly large to gigantic coelurosaurs often likened to ground sloths - might have gone through an arboreal phase in their evolution. Supposedly, these small, tree-climbing sloth dinosaurs were necessary (in the theoretical sense) given the absence from the fossil record of early, primitive members of the therizinosauroid lineage. Implied by Nessov's hypothesis is the idea that the large, ground sloth-like therizinosauroids must have descended from tree sloth-like ancestors, but there isn't really any reason to agree with this. Furthermore, we do now have fossils of basal therizinosauroids (like Beipiaosaurus Xu et al., 1999, Nothronychus Kirkland & Wolfe, 2001, Falcarius Kirkland et al., 2005, and Suzhousaurus Li et al., 2007) and they don't match Nessov's predictions.
The ideas promoted by Rozhdestvensky and Nessov have essentially remained restricted to obscure, specialised literature and there hasn't been much opportunity for them to become widely known (articles by Naish notwithstanding). However, Sankar Chatterjee - perhaps best known for his publications on the alleged Triassic bird Protoavis - has brought wide attention to ideas about scansorial theropods by publishing them in a book and in well known, mainstream journals, and by speaking about them at conferences. Among maniraptoran theropods, Chatterjee (1997) proposed that the stiffened dromaeosaurid tail functioned as a prop, functionally analogous to the stiffened rectrices of woodpeckers and other trunk-climbing birds, and he also noted that the opisthopubic pelvis and strongly hooked manual claws allowed these dinosaurs to be proficient climbers. Rather than restricting tree-climbing to those theropods closest to birds, however, Chatterjee (1997, 1999) went on to propose that scansoriality was primitive for all coelurosaurs, and he has even promoted the downright unlikely idea that such animals as compsognathids and ornithomimosaurs were tree-climbers.
In a similar but far less well known hypothesis, Svend Palm (1997) proposed that small, climbing coelurosaurs used their hooked manual and sharp pedal claws to climb the vertical trunks of cycad-like plants, regarding the crowns of such plants as providing ideal hiding and nesting places for such dinosaurs (Palm 1997). Palm compared his little scansorial proto-birds with the non-dinosaurian proto-birds imagined by Gerhard Heilmann, and - like Palm - Heilmann had reconstructed his hypothetical animals as well able to ascend vertical trunks [one of Palm's hypothetical climbing proto-birds is shown below, from Palm (1997)].
While there are a few additional mentions of tree-climbing dinosaurs here and there in the literature, that's essentially it. As discussed here, most of these ideas can be discounted for being extremely unlikely (e.g., scansorial ornithomimosaurs) or for being too speculative (e.g., hypothetical early therizinosauroids). But they can't all be discounted in this way, and we should still take seriously the idea that such theropods as dromaeosaurids might have been capable climbers. Furthermore, as mentioned earlier we now know of at least a couple of small theropods that may even have been specialised climbers. To look at the climbing abilities of these animals further we'd need to carefully examine their anatomy and compare them with what we know about living animals. I might do that some time, but not right now. Some comments on this subject can already be found in Naish (2000a, b). Goats in trees, wolverines, big-headed turtles, pygmy parrots and so on.
Refs - -
Chatterjee, S. 1997. The Rise of Birds. The Johns Hopkins University Press, Baltimore.
- . 1999. Feathered coelurosaurs and the early evolution of birds. Journal of Vertebrate Paleontology 19 (supp to 3), 37A.
Fox, W. 1866. Another new Wealden reptile. Athenaeum 2014, 740.
Galton, P. M. 1971a. Hypsilophodon, the cursorial non-arboreal dinosaur. Nature 231, 159-161.
- . 1971b. The mode of life of Hypsilophodon, the supposedly arboreal ornithopod dinosaur. Lethaia 4, 453-465.
Naish, D. 2000a. Theropod dinosaurs in the trees: a historical review of arboreal habits amongst nonavian theropods. Archaeopteryx 18, 35-41.
- . 2000b. 130 years of tree-climbing dinosaurs: Archaeopteryx, 'arbrosaurs' and the origin of avian flight. The Quarterly Journal of the Dinosaur Society 4 (1), 20-23.
- . 2002. The historical taxonomy of the Lower Cretaceous theropods (Dinosauria) Calamospondylus and Aristosuchus from the Isle of Wight. Proceedings of the Geologists' Association 113, 153-163.
Nessov, L. A. 1995. Dinozavri severnoi Yevrazii: Novye dannye o sostave kompleksov,. ekologii I paleobiogeografii. Institute for Scientific Research on the Earth's Crust, St. Petersburg State University, St Petersburg.
Olshevsky, G. 1991. A Revision of the Parainfraclass Archosauria Cope, 1869, Excluding the Advanced Crocodylia. Publications Requiring Research, San Diego.
- . 1994. The birds first? A theory to fit the facts. Omni 16 (9), 34-86.
- . 2001a. The birds came first: a scenario for avian origins and early evolution, 1. Dino Press 4, 109-117.
- . 2001b. The birds came first: a scenario for avian origins and early evolution. Dino Press 5, 106-112.
Osborn, H. F. 1917. Skeletal adaptations of Ornitholestes, Struthiomimus, Tyrannosaurus. Bulletin of the American Museum of Natural History 32, 133-150.
Palm, S. 1997. The origin of flapping flight in birds. Svend Plam, Ballerop [available online here].
Paul, G. S. 1988. Predatory Dinosaurs of the World. Simon & Schuster, New York.
Rozhdestvensky, A. K. 1970. Giant claws of enigmatic Mesozoic reptiles. Paleontology Journal 1970 (1), 117-125.
Swinton, W. E. 1936a. Notes on the osteology of Hypsilophodon, and on the family Hypsilophodontidae. Proceedings of the Zoological Society of London 1936, 555-578.
- . 1936b. The dinosaurs of the Isle of Wight. Proceedings of the Geologists' Association 47, 204-220.
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More like this
I expected to see Chris Glen's paper mentioned here
Neat. I'd never really thought about it.
So despite having seen a number of the tree climbers in the past it's like their new again!
A tree climbing Deinocheirus would be way too neat...
Very nice post as usual. I have also several books of tree-climbing little Hypsilophodons, I own even the german version of the book from which your picture is. It is really highly interesting how the views on different dinosaurs have changed over the last decades. I´m a good bit younger than you and even I have seen this change. I grew up with amphibius sauropods and a lot of big theropods walking upright and using their tail like a third leg.
Weight would not disqualify a climber if it climbed only or primarily when young.
Wouldn't it be really, really cool if someone did a book on how views about dinosaurs have changed over time? Huh, wouldn't it? Wouldn't it? :) Back to work...
PS - John, no mention of Glen & Bennett (2007) because it doesn't include any speculations on tree-climbing, only claw curvature data. Their data supported ground foraging in both non-avian theropods and Mesozoic birds. It's one of Alan Feduccia's favourite papers :)
Ref - -
Glen, C. L. & Bennett, M. B. 2007. Foraging modes of Mesozoic birds and non-avian theropods. Current Biology 17, 911-912.
The idea of some small therapods being able to climb/jump into trees doesn't seem that odd - especially after the first time I saw a moorhen walking along some branches as I stood there suprised
what, no arboreal sauropods?
I mean those elongate tails were clearly prehensile and Wedel (2003) demonstrated how helium filled air-sacs allowed sauropods to adjust their buoyancy, right?
You're drawing of the arboreal Deinocheirus reminds me of Henry Gee's speculation in "A Field Guide to Dinosaurs: The Essential Handbook for Travelers in the Mesozoic" about deinocheirs having juveniles with the long, prehensile tails, that move like sloths in trees.
Wait, isn't that the book illustrated by Luis Rey? I have that book, and I don't remember baby therizinos having prehensile tails. I'm gonna have to recheck...
Seems to me that the paravian ancestor (something close to Mahakala was probably arboreal. Basal deinonychosaurs show plenty of arboreal potential, and of course birds do, too. Interesting that both dromaeosaurs and troodontids went "back" to the ground, perhaps to avoid competition from the flourishing bird populations?
Question: Has there been any work done on Epidendrosaurus/Scansoriopteryx since the intital announcement papers? Does that critter have a place on the maniraptor family tree? And where are all the adults? :-D
Any smaller herbivores which had no hooves and could fill the role of monkeys and sloths?
I've ever found strange that a group so diversified as the dinosaurs didn't include arboreal members. Probably many Maniraptorans will fill this gap...
Pleasure to get the chance to read your stuff again.
As to the tree-climbing Deinocheirus, we can always hope that we find one that got stuck in amber I suppose.
neil: hydrogen, not helium.
Let us not neglect scansorial plesiosaurids, ancestors of the modern "treetops Nessie".
tdh is onto something. (I particularly like to imagine infant tyrannosaurids swinging on vines, ululating.) Support by clawed hands seems unnecessary; modern birds do without, and I recall a bird on Attenborough that doesn't fly, but hops about in trees. Still, squirreliness would be a valuable adaptation. Would fossilized reversible ankles be recognizable as such?
Deinocheirus a tree-climber? Those would have to be some awfully big trees. I wouldn't park my car under one of those.
I'm reliably informed that Rozhdestvensky even went so far as to produce a reconstruction of a sloth-like Deinocheirus clambering about in a tree, but I couldn't find this in the literature and ended up creating my own hypothetical climbing Deinocheirus (Naish 2000b).
Yeah...we're gonna need to see that. Follow-up post?
Even I grew up with arboreal Hypsilophodon, and I'm just 26 years old. BTW, you probably managed to find the ugliest illustration of such a beast ever. It oozes 70s flair -- "an epoch marked by brutal ugliness", as the Austrian magazine profil called it in the late 90s. Ugh.
Very easily.
BTW, people, please stop calling sickle claws an adaptation for climbing. They're an adaptation to cutting off the branch on which you're standing. And all evidence that Microraptor was a climber are the phalangeal proportions of the toes, which are not quite cursorial.
The much more clearly arboreal Epidendrosaurus/Scansoriopteryx may have been a bird or almost a bird...
In the original Jurassic Park novel, 'hypsilophodonts' like Othnielia are portrayed as being semi-arboreal; their depiction reminded me of tree kangaroos (given that when on the ground, they supposedly fled by 'hopping'). Microceratops were also depicted in the novel as being arboreal, *leaping* from branch to branch like monkeys.
And in The Lost World (the sequel to Jurassic Park), one scene has unseen creatures in the trees above the protagonists, one of whom doubts that these creatures are monkeys.
To Zach Miller: Yes, that's the book illustrated by Luis Rey, but its the Deinocheirus, not the therizinosaur, that has the babies with prehensile tails that climb around in trees.
And for you who don't have the book: it's not always fact based, in fact, there is a lot of liberties taken (so don't take it too seriously ;) ).
And about the Scansoriopteryx/Epidendrosaurus affair, Stephen Czerkas thinks that it isn't a theropod, but another dinosaur sister-group that is the true bird ancestor group. Whether he has published anything technical on it, I don't know. I don't think he even thinks maniraptorans are dinosaurs, similar to Alan Feduccia, who now claims that maniraptorans had feathers, but that they aren't dinosaurs---a dubious idea. So I don't know how credible Czerkas is; it seems he has a similar "Birds First" idea to George Olshevsky, except Czerkas doesn't accept dinosaurs as descendants.
Thanks for this post; in Rob Bakker's novel 'Raptor Red' the Utah-Raptor protagonists figure out how to climb a tree during a flood, and while I'm sure this is one of the many liberties he took in the book rather than a quality hypothesis, it left me with an interest in the subject ever since I read it multiple times as a kid.
Actually, I guess Czerkas believes that Maniraptora is a sister-group to the Theropoda. Here is the pdf link to the article, if anybody wants it: http://www.dinosaur-museum.org/featheredinosaurs/arboreal_maniraptoran…
Zach Armstrong: Oh yes, that book certainly takes plenty of creative license... A lot of the 'information' in the book had me doing a double take, and wondering what sort of real-life examples could have inspired some of the bizarre traits that were presented.
Thomas M.: Ah, here's a painting Luis Rey did based on that scene.
http://www.luisrey.ndtilda.co.uk/html/1kflood.htm
Darren, you wrote:
Admittedly, these mass estimates assume that it was built like the ostrich dinosaurs we know of from better remains, whereas if it was the short-legged slothosaur that Rozhdestvensky imagined it may well have weighed much less.
[...]
it might have fed on fruits and leaves 'and also, possibly, on the eggs, or even nestlings both of birds and pterosaurs nestling [sic] in trees, or on any other small animals' (Rozhdestvensky 1970, p. 123).
If Deinocheirus was an herbivore or frugivore, it would have been a good deal more massive than a terrestrial carnivore of the same size, simply because the bone structure and gut anatomy would increase the weight of the animal, it would need a much larger gut to accomodate the diet. Such an animal would not be a climber, as in extinct ground sloths with plant-grasping forelimbs.
Real Deinocheirus don't climb trees, they level the forest... ;)
Anybody knows (checked?) what range of movements had these arms? If you depict it as fighting, pulling branches or climbing whatever, it would be good to know.
Thanks to all for comments, much appreciated. Some select responses..
Zach Miller asked if any work had been done on the phylogenetic placement of Epidendrosaurus/Scansoriopteryx. Yes, Senter (2007) found epidendrosaurs to be basal members of Avialae (because Avialae has been given a branch-based definition it is more inclusive than even the most inclusive node-based version of Aves). As for further work on this group, stay tuned is all I will say...
Jerzy asked if there were any small dinosaurian herbivores which might have played at occupying monkey- or sloth-like roles. No, non-avian dinosaurs didn't go in for this so far as we can tell from the fossil record (though note that it's a requirement of Olshevsky's BCF hypothesis that they did, and that multiple small, arboreal 'dino-birds' actually existed. They would have resembled the arbrosaurs of Dixon's The New Dinosaurs). In answering the question 'where are the Jurassic and Cretaceous climbers?', Naish (2000b) says 'One possible answer is that small pterosaurs, lizards and mammals like dryolestoids were the dominant arboreal animals at this time. If so, dinosaurs may only have begun their arboreal 'career' with the earliest birds, currently represented only by Late Jurassic Archaeopteryx' (p. 23). When this article was written, however, epidendrosaurs were unknown (or, at least, were just a rumour).
Tree-climbing Deinocheirus: you've all seen my imagined version of this, it's the big animal on the left in the picture shown at top. Baby Deinocheirus are indeed described in Gee & Rey's A Field Guide to Dinosaurs as having 'arms and legs of equal length, as well as long prehensile tails' and as being sloth-like climbers (p. 131), but unfortunately there are no illustrations of them. Adults are depicted as super-sized ostrich dinosaurs of course.
Zach Armstrong mentioned Stephen Czerkas's ideas about the affinities of the epidendrosaurs. It's hard to think of a more ridiculous argument: Czerkas & Yuan (2002) argued that epidendrosaurs/scansoriopterygids are allied to maniraptorans and birds, yet at the same time aren't part of Theropoda. They go on to say that maniraptorans diverged from the base of Saurischia and can't be included in Theropoda because theropods cannot include tree-climbing forms, and because the unusual epidendrosaur hand bars them from inclusion within Theropoda. This is illogical nonsense and it's been rightly panned by everyone who's considered it since. It's similar to the idea now being promoted by Feduccia and colleagues (yes, they are STILL at it: Feduccia et al. 2007): despite arguing for decades that non-avian maniraptorans cannot possibly be allied to birds, they now want these animals to be part of the avian radiation... yet still not part of Theropoda. Duh?
Jaime noted how a heavy herbivore with big guts would not be a climber. Given that Deinocheirus would certainly have weighed in the range of tons rather than just kg, I think that's a given. Note however than big herbivores like large extinct orangutans and giant lemurs, projected weights up to c. 350 kg, were climbers. Gorillas climb more than people seem to think, and some reasonably big megalonychid sloths had climbing specialisations (Pujos et al. 2007). Furthemore, lions and tigers and bears can climb to some extent (some lions do so regularly). The idea promoted by some (Larry Martin et al.) that non-avian maniraptorans like Deinonychus (which weighed, at most, 50 kg or so) can be excluded from climbing on size alone is clearly an invalid argument that shouldn't be used.
Jerzy: range of forelimb movement in ostrich dinosaurs was described by Nicholls & Russell (1985). They showed that these animals had extensive reaching abilities, little rotational ability, and a hook-like hand function. This is all good for such activities as hooking onto foliage and pulling down branches.
Refs - -
Czerkas, S. A. & Yuan, C. 2002. An arboreal maniraptoran from northeast China. In Czerkas, S. J. (ed) Feathered Dinosaurs and the Origin of Flight. The Dinosaur Museum (Blanding, Utah), pp. 63-95.
Feduccia, A., Martin, L. D. & Tarsitano, S. 2007. Archaeopteryx 2007: quo vadis? The Auk 124, 373-380.
Nicholls. E. L. & Russell, A. P. 1985. Structure and function of the pectoral girdle and forelimb of Struthiomimus altus (Theropoda: Ornithomimidae). Palaeontology 28, 643-677.
Pujos, F., de Iuliis, G., Argot, C. & Lars, W. 2007. A peculiar climbing Megalonychidae from the Pleistocene of Peru and its implication for sloth history. Zoological Journal of the Linnean Society 149, 179-235.
Senter, P. 2007. A new look at the phylogeny of Coelurosauria (Dinosauria: Theropoda). Journal of Systematic Palaeontology 5, 429-463.
"In answering the question 'where are the Jurassic and Cretaceous climbers?', Naish (2000b) says 'One possible answer is that small pterosaurs, lizards and mammals like dryolestoids were the dominant arboreal animals at this time."
These groups are mostly insectivores, maybe small predators and omnivores. Where are mesosoic specialised medium-sized to big arboreal herbivores, to eat all these stems and leaves? Equivalent of todays monkeys, sloths, tree kangaroos, koalas etc.
Hi Jerzy. We don't know of any Mesozoic equivalents of the animals you have in mind. Some Mesozoic mammals (like ptilodontid multituberculates for example) combined herbivory with scansorial abilities, and some Cretaceous birds seem to have eaten seeds/fruit on occasion (as evidenced by stomach contents in Jeholornis, for example). Some pterodactyloid pterosaurs - specifically tapejarids - might have been herbivorous (some discussion here). But that's about it. Remember that there may have been fewer ecological opportunities for arboreal herbivores in the Mesozoic.
Darren, (please excuse me asking... it's hard for me to resist such an opportunity for wild pedantry)...
You said
Goats in trees, yes - I know that's true (seen the ad). But...
Goats in wolverines? I know wolverines are called gluttons, but still... or is that metaphorical, like, sheep in wolves clothing?
Goats in big-headed turtles? Well I guess the turtle's head would need to be big, and maybe with snake-like dislocatable jaws, to swallow a goat whole.
Goats in pygmy parrots? Oh come on. Now if you'd said giant extinct cursorial predatory parrots, maybe... but pygmy? Unless you know of an obscure strain of pygmy, PYGMY goat, that's too much to swallow. Now I know you're just winding us up. Again.
(Couldn't wait till next April 1st to follow up your 'amphisbaenid origin of mammals' coup, huh?)
;-D Only kid-ding... Graham
Thanks Darren! I'm sure they must be around.
It seems odd to not have proof of primarily scansorial/arboreal dinosaurs. I seem to remember reading that komodo dragons, when young, tend to favor the trees as both a means of raiding nests and avoiding their larger family members...I guess it could hold true that certain dinosaurs might have had a similar idea. Still, that's only temporary. But then again, new stuff is popping up all the time.
I'm aware of Czerkas' idea (I have the book) regarding maniraptors as Theropoda sister-group, and it's got to be some kind of April Fool's joke. Now you've got me at the edge of my seat, Darren, with that "stay tuned" comment about epidendrosaurs.
Question: Which name should I be using--Epidendrosaurus or Scansoriopteryx? Is there a concensus?
Imagine a lion with its jaws locked on a bear being dragged up into a tree by a tiger. All together they might mass as much as a juvenile deinocheirus. The tree ferns must have been stout in those days.
By the way: "oh my!" I'll never know how Darren managed to avoid writing that.
I think it's possible that certain species climbed trees when they were chicks (cubs?) and stopped as adults. It isn't unheard of. Look at brown bears. Look at us, for that matter; Gregory S. Paul has pointed out that anatomically speaking, small children are semi-arboreal primates. It would depend on local conditions, I guess.
Speaking of which--do you have any speculation on what might have been out there that didn't fossilize? Could there have been, oh, Early Cretaceous multituberculates that glided like flying squirrels, but lived on terrain that did not favor fossilization? Or a genus of pterosaur that tended to go flightless on oceanic islands, the way rails did later? A tiny, fluffy dinosaur with nutcracker jaws that lived among the dwarfed conifers on high mountain slopes, harvesting the nutrient-rich seeds for winter?
Zach asked....
There is a consensus: Epidendrosaurus. Should we need a name for the clade that includes Epidendrosaurus and any close relative, it should, according to the ICZN, be called Scansoriopterygidae.
Jenny said...
There's lots of stuff out that almost definitely existed, but we have yet to find. There should be lots of little Jurassic maniraptorans that pre-date the archaeopterygids and more small, early tyrannosaurs and ostrich dinosaurs. Some of the maniraptorans will probably be climbers. We know that non-avian dinosaurs evolved dwarf island endemics (e.g., the brachiosaur Europasaurus), but we should expect more to turn up. Miniaturised carnosaurs, diplodocoids, iguanodontians and stegosaurs for example. A lineage of arboreal folivorous ornithischians would be cool, as would cursorial, hypercarnivorous ceratopsians with eagle-like beaks. And of course Stratoposeidon...
Zach,
Czerckas' book is no prank. The writing and the science may be atrocious, and the authorship on the various "papers" withing shaky, but the books' premises are on the whole intended.
"It's similar to the idea now being promoted by Feduccia and colleagues (yes, they are STILL at it: Feduccia et al. 2007): despite arguing for decades that non-avian maniraptorans cannot possibly be allied to birds, they now want these animals to be part of the avian radiation... yet still not part of Theropoda. Duh?"
Theropoda is a phylogeny-defined concept...which of course assumes a particular phylogeny. It needn't - and indeed doesn't - make any sense in a markedly different phylogeny - since obviously different animals will be included. Czerkas, myself, and Feduccia are each now trying to dot the 'i's and cross the 't's of theories that are BCF in the Cretaceous (a la Paul) and also (I think this includes Czerkas et various al) BCF in the Triassic (contra Paul). From my position, a "theropoda" that included everything from the last joint ancestor of say Coelophysis and Deinonychus, would be huge. Czerkas and Feduccia seem to have avoided this by using a smaller theropoda which includes only the earlier forms.
It has long been a perfectly reasonable theory that troodonts and dromaeosaurs are descended from Archaeopteryx or something close to it. For those who want to judge theories on a personal basis, Holtz has this option pencilled in in his lecture notes, and Mortimer and many others are open-minded about it, as well as committed BCF'ers. Since in this view troodonts and dromaeosaurs can't be ancestral to Ax since they are its descendants, what bauplan would you prefer as its ancestor? An un-feathered relatively short-armed compsognathid, or something more like a scansoriopterygid? Well, if you think the former, fine, but I really think those who disagree don't deserve "Duh". It's either the truth, or not that bad a mistake if that's what it is, and rendering theropoda meaningless is a pretty inescapable consequence of just the K version of BCF.
The part of the theory that Feduccia "is STILL at" is that birds are not descended from dinosaurs, and whether it's right or wrong it's a damn good theory, especially these days. He isn't still at the all-maniraptorans-from-birds position; as stated above, he's only just upgraded to that in the last few years, and just being able to make such a change late in a career is quite admirable I think. But maybe he prefers to hone and adjust his theories in the light of new evidence over a few decades than to be wrong forever which is the way a lot of dinobirders will stay.
As for Olshevsky's version requiring arboreal non-avian dinosaurs which the fossil record may not show, versions of BCF such as mine require arboreal dinobird *ancestors* - and the fossil record is entirely consistent with that view whether people want to call Scansoriopteryx, Protoavis etc dinosaurs or theropods or a chimera or not. (Incidentally an earlier form of Protoavis would have been hypothesised even if it hadn't been discovered, and the type is as fabulous a gift for Triassic BCF as Ax is for K BCF.)
Dynamically evolving systems staying within the same region have attractors. If you were evolution, how many different types of predatorial bauplans would you invent from reptilian bipedal warm-blooded ancestors? Big teeth at the front, legs in the middle, tail for balance. The slashing claw option was an amazing divergence and even those versions still look like "theropods".
It's important to remember that theories different from the ones you hold yourself will not just be different in a few obvious ways, but also in subtle details. Also, any differences in belief (including such subtle unexpected differences) are not ridiculous just because they are unfamiliar to you.
You may as well apply yourselves properly to understanding full-on BCF, folks, because it's going to win out. If you are going to argue against it, then if you care how posterity sees you, it's better to use good arguments.
Nice to see a ref to Palm's paper - doesn't get mentioned much..
I'm sure nobody checks the comments on posts this old anymore, but I just wanted to throw this in.
I forget who the authors were, but there was a presentation at SVP bashing the "climbing theropods" idea. Using Microraptor, the team concluded that the little theropod lacks adaptations for climbing seen in claw-climbers (like squirrels and nuthatches) and grip-climbers (monkeys, sloths). They suggested that dromaeosaurs might get UP the trees just fine, but getting down would be a major problem, as it is in cats.
Of course, Microraptor developed its own way of getting down from trees (gliding/flight), so I was disappointed that the presentation focused so heavily on one animal.
Oh yeah, and a very good presentation it was. I don't think it focused all that heavily on Microraptor; it just mentioned it several times because it has often been considered the most arboreal of them all.
(Nobody checks out such old threads -- but the latest 10 comments are accessible from a sidebar... when I'm already here, I might as well comment on the one above yours:)
And huge it is, what with 12,000 extant species and all.
That would require making Theropoda paraphyletic -- except that Czerkas and Feduccia simply deny that.
Try that of Jinfengopteryx, perhaps with longer arms.
Oh no. The compsognathids are far away phylogenetically, and feathers extend down the tree at least that far.
What do you mean by "meaningless"? That the birds are included? That's inevitable anyway.
Then why does it have every single piece of evidence against it?
(Besides, it's way too small to be called a theory. It's a hypothesis. A theory is for example the theory of evolution by natural selection.)
Uh, no, it should be expected from any scientist if the evidence requires it... speaking of which, did I mention that the evidence is against ABSRD and MANIAC?
I haven't seen such an embarrassing statement since "the fundamentals of our economy are strong". The good man has already had a few decades to start noticing that birds are dinosaurs, and still persists in ignorance and embarrassing rationalizations...
Oh man. Did you read the relevant chapter in the Ostrom Symposium Volume -- just to remind you, it came out seven years ago? Did you completely miss all the DML discussions about how the neck is from a drepanosaurid? Did you even fail to compare Chatterjee's (1997) drawings to the photos at the end of that very same book? Protoavis is a really obvious chimera. Check it out -- the lower limbs are way too big for the thighs!
Scansoriopteryx, on the other hand, is not just not a chimera, it's close to the origin of birds, and, yes, shows arboreal adaptations. Adaptations that Archie lacks. I think we're looking at a separate invasion of the trees.
That looks like a great point, but it isn't. Check out Effigia. The ankles and hips scream "rauisuchian" -- the resemblance to theropods is superficial.
Oh no. The evidence decides what is ridiculous.
And McCain was going to win out because the PUMA voters, the disappointed Hillary supporters, were going to vote for him. All three of them.