Every now and again – speaking here as someone who’s published some number of articles, books and technical papers – I find it worthwhile to look back at the completed works of the past. For whatever reason, I’m doing that a fair amount right now, and today I want to talk about a peculiar short paper of mine that appeared in 2000…
Caption: juvenile Deinonychus in the trees! Image: Darren Naish.
Titled ‘Theropod dinosaurs in the trees: a historical review of arboreal habits amongst nonavian theropods’ and featured in the German journal Archaeopteryx, the paper concerned provides a brief overview of published comments on the subject before evaluating the concept of the tree-climbing (non-bird) theropod (Naish 2000a). I tried to make clear in the paper that while evidence for arboreality in non-bird theropods lacked support, I found it likely that scansoriality was plausible (Naish 2000a). Arboreality refers specifically to living in the arboreal environment and scansoriality to the ability to climb in trees; the two are not synonymous.
Caption: a physical copy of the paper – Naish (2000a) – that’s the focus of the article here. Unusually, I own both the specific issue of the journal and reprints of the paper itself. That’s a fluke and I can’t recall now how and where I got hold of the whole issue. Incidentally, the same issue also features John Videler’s paper on the idea that Archaeopteryx might have been capable of running over the surface of water, basilisk-style. Images: Darren Naish.
And – rightly or not – one of my foundational assumptions was that some degree of scansoriality should be expected or assumed for non-bird theropods given that avian origins likely involved use of trees. We’ll come back to that.
In fact, the article basically opens by noting that tree-climbing (non-bird) theropods are “currently popular in the non- and semi-technical palaeontological literature” (Naish 2000a, p. 35), my idea being that Greg Paul’s tree-climbing Ornitholestes from Predatory Dinosaurs of the World (Paul 1988) was a seminal image of the time. That’s arguable, given that many researchers interested in dinosaur palaeobiology neither pay attention to what people like Greg Paul were and are saying, nor remember or receive influence from artistic reconstructions. In my defence, I was seeing things more from the perspective of a social historian interested in palaeoart than that of a palaeobiologist: my understanding that Paul, Robert Bakker and the palaeoartists inspired by their writings and reconstructions had a paradigmatic impact on views of Mesozoic life (Naish 2021) is still partly at odds with that of many palaeontologists, especially here in the UK.
Caption: Greg Paul’s illustration of a climbing Ornitholestes, from Predatory Dinosaurs of the World (Paul 1988). The style of printing used in that book means that the illustrations do not photograph well: the original drawing is grey, not just black and white as it looks here. A 2024 update of this illustration, included in the third edition of Paul’s The Princeton Field Guide to Dinosaurs, has a modified head and lacks a nasal horn. Image: (c) Greg Paul.
Also on an introspective note, I very much regret the way in which I framed the view of 1980s/90s dinosaur palaeobiology discussed above: I said that we partly owed the concept of tree-climbing dinosaurs “to the highly artistic members of the ‘dancing dinosaur’ school” (Naish 2000a, p. 35). The term ‘dancing dinosaurs’ had been used by Bakker himself but the implication that there was a ‘dancing dinosaur school’ looks derogatory, and I shouldn’t have used it.
Anyway, the idea that certain smaller dinosaurs might have been capable of tree-climbing certainly goes back much further than the 1980s, and was mentioned here and there – mostly in connection with the Wealden ornithischian Hypsilophodon – during the 1910s, 20s and 30s. During archival research on the theropods of the English Wealden, I was interested to find that the Reverend William Fox – finder of several of the Isle of Wight Wealden Supergroup theropods I was working on – mentioned this idea in his brief articles on the enigmatic theropod Calamospondylus oweni, published in 1866 (Fox 1866a, b). This makes him the first person, so far as we know, to suggest tree-climbing in non-bird dinosaurs, though it should be said that he proposed this idea on quite spurious grounds, namely the perceived lightness and pneumaticity of the bones (Fox 1866a, b).
Fox’s idea was commented on favourably by William Swinton in 1936, one of the few researchers to keep dinosaur studies alive in the UK during the quiet, post-Victorian period (Martill et al. 2001). Swinton published several articles on Wealden dinosaurs during the 1930s and 40s and is also credited with writing the first ever dinosaur textbook, namely his 1934 The Dinosaurs: A Short History of a Great Group of Extinct Reptiles.
Caption: illustrations from Naish (2000a) that are relevant to the issue of scansoriality in non-bird theropods. Carnivorans like wolverines are not specialist climbers, but the flexibility of their limbs, sharpness of their claws and so on mean that they can climb if need be (this drawing is based on a photo). Theropods and carnivorans are fundamentally different, and what goes for one is not necessarily applicable to the other. Nevertheless, this is not a wholly invalid analogy. At right, a figure devoted to toe pad specialisations in trunk-climbing passerines, the idea being that we might test for trunk-climbing should we find preserved toe pads on non-bird dinosaurs (we now have, and the relevant specialisations are not present). Images: Darren Naish.
Hypsilophodon and Galton. Skip on a few decades to the 1970s, and tree-climbing in non-bird dinosaurs was mentioned again, albeit in a very different context. Peter Galton’s redescription of Hypsilophodon led to his re-evaluation of the scansorial hypothesis promoted by Othenio Abel, Swinton and those beforehand (Galton 1969, 1971a, b, 1974). Hypsilophodon did not, it turns out, have the opposable hallux, prehensile hands and feet and especially flexible forelimbs that earlier authors said it did, and its anatomy was instead that of a more cursorial animal committed to fully terrestrial life. Hypsilophodon is not, of course, a theropod, but it’s not irrelevant here because reconsideration of its alleged climbing abilities meant that Galton (1971a, b) did credit the idea that scansoriality remained a possibility for certain smaller non-bird dinosaurs, at least.
Caption: during the first half of the 20th century, Hypsilophodon was interpreted as scansorial or arboreal, and it’s possible that this led workers of the time to look especially favourably at the idea that other dinosaurs, like small theropods were tree-climbers too. For all that, only a few reconstructions of the time show these animals among the branches. Galton’s papers of the 1970s ultimately showed that Hypsilophodon lacked climbing adaptations and was fully terrestrial, as depicted in the images at left (from Galton 1974; the illustration is by Bakker). At right, we see (E) Galton’s reconstruction of the Hypsilophodon foot versus (F) Othenio Abel’s ‘grasping’ reconstruction of the foot from 1912. Images: Galton (1971, 1974).
Ostrom and beyond. Also on theropods, John Ostrom argued in his work on Archaeopteryx and bird origins that both archaic birds (like Archaeopteryx) and near-bird theropods (like Deinonychus) lacked structures that might suggest any adaptation for climbing (Ostrom 1974, 1979); these animals were “ground-dwelling cursorial bipeds with no obvious scansorial or arboreal adaptations” (Padian & Chiappe 1998, p. 19).
And that’s the ‘mainstream’ view that’s remained prevalent today. It’s notable that other suggestions from the late 20th century pertaining to scansoriality in non-bird theropods – there’s Anatoly Rozhdestvensky’s 1970 suggestion of climbing in ostrich dinosaurs and Sankar Chatterjee’s and Svend Palm’s 1990s proposals of trunk-clinging in Deinonychus-like maniraptorans (Naish 2000a, b) – have come from ‘outside’ voices not influential to the mainstream.
Caption: in his 1997 book The Rise of Birds (and in technical papers too), Sankar Chatterjee argued that “The elongated forelimbs and swivel wrist joint in proavian dromaeosaurs can best be interpreted as features evolved for the climbing of vertical tree trunks” (Chatterjee 1997, p. 166) (excuse the teleological framing); the diagrams at left were featured in the context of that claim. Also in 1997, Svend Palm’sThe Origin of Flapping Flight in Birds argued that ‘tree-mounting’ behaviour evolved in dinosaurs, and it was in this setting that bird flight evolved (Palm 1997). Hypothetical pre-birds like those shown at right were featured in this work. Images: Chatterjee (1997), Palm (1997).
Several studies of claw curvature and digit proportions in non-bird theropods have been published since my 2000 article appeared, and as a generalisation they conclude that none of these animals were regular climbers (e.g., Birn-Jeffery et al. 2012)… with the possible exception of the very odd, very small scansoriopterygids (Dececchi et al. 2016). By quirk of fate, the first member of this group to become known to science was announced and discussed at conferences at about the time that a follow-up article to Naish (2000a) went to press (Naish 2000b).
Caption: the partial skeleton (part at left; counterpart at right) of the tiny scansoriopterygid Scansoriopteryx heilmanni Czerkas & Yuan, 2002, today generally considered synonymous with Epidendrosaurus ninchengensis Zhang et al., 2002. This animal is tiny, with a total length estimated at about 16 cm. It’s generally agreed that scansoriopterygids were climbers, and probably arboreal. Images: Czerkas & Yuan (2002).
Why Archaeopteryx anyway? My decision to publish this article in the pages of Archaeopteryx also deserves comment, since I know today that this journal is considered obscure, off the radar for most researchers, and hard to get as well.
Fact is, I just didn’t appreciate that at the time. One of my many failings as a young academic is that I didn’t have a clue on what I was doing, and I certainly didn’t follow any sensible course of action when it came to where or how I published things. And I wasn’t part of a research group where we were told or encouraged to aim for the top, or to ‘standard’ journals in the field… things were far more, shall we say, provincial. I chose to submit an article to Archaeopteryx because it seemed like a venue where articles on matters relevant to bird origins might be welcome. Indeed, a few articles devoted to the possibility of climbing in Mesozoic theropods had recently been published there (Chiappe 1997, Yalden 1997).
And that brings things to a close. Naish (2000a) is here online; it’s a weird little paper but not an especially bad one, and it’s been cited a few times where appropriate. It’s been missed a few times too, but that’s understandable in view of my comments above.
For previous Tetrapod Zoology articles on climbing dinosaurs, bird origins, hypotheses of bird ancestry and other connected issues, see…
A quick history of tree-climbing dinosaurs, July 2008
Epidexipteryx: bizarre little strap-feathered maniraptoran, October 2008
Did Velociraptor and Archaeopteryx climb trees? Claws and climbing in birds and other dinosaurs, December 2012
Yi qi Is Neat But Might Not Have Been the Black Screaming Dino-Dragon of Death, May 2015
The Second Edition of Naish and Barrett’s Dinosaurs: How They Lived and Evolved, November 2018
Heilmann, Thompson, Beebe, Tetrapteryx and the Proavian, January 2019
Alan Feduccia’s Romancing the Birds and Dinosaurs: Forays in Postmodern Paleontology, October 2023
Refs - -
Chatterjee, S. 1996. The Rise of Birds. The Johns Hopkins University Press, Baltimore and London.
Chiappe, L. M. 1997. Climbing Archaeopteryx? A response to Yalden. Archaeopteryx 15, 109-110.
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.
Fox, W. 1866a. Another new Wealden reptile. Athenaeum 2014, 740.
Fox, W. 1866b. Another new Wealden reptile. Geological Magazine 3, 383.
Galton, P. M. 1969. The pelvic musculature of the dinosaur Hypsilophodon (Reptilia: Ornithischia). Postilla 131, 1-64
Galton, P. M. 1971a. Hypsilophodon, the cursorial non-arboreal dinosaur. Nature 231, 159-161.
Galton, P. M. 1971b. The mode of life of Hypsilophodon, the supposedly arboreal ornithopod dinosaur. Lethaia 4, 453-465.
Galton, P. M. 1974. The ornithischian dinosaur Hypsilophodon from the Wealden of the Isle of Wight. Bulletin of the British Museum (Natural History) 25, 1-152.
Martill, D. M., Naish, D. & Hutt, S. 2001. Introduction. In Martill, D. M. & Naish, D. (eds) Dinosaurs of the Isle of Wight. The Palaeontological Association (London), pp. 11-24.
Naish, D. 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.
Ostrom, J. H. 1974. Archaeopteryx and the origin of flight. Quarterly Review of Biology 49, 27-47.
Ostrom, J. H. 1979. Bird flight: how did it begin? American Scientist 67, 46-56.
Padian, K. & Chiappe, L. M. 1998. The origin and early evolution of birds. Biological Reviews 73, 1-42.
Palm, S. 1997. The Origin of Flapping Flight in Birds. Svend Palm, Ballerop.
Yalden, D. W. 1997. Climbing Archaeopteryx. Archaeopteryx 15, 107-108.
