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I read a lot of books in 2010, and mostly enjoyed all of them. Among my favourites was Luis Chiappe’s Glorified Dinosaurs: The Origin and Early Evolution of Birds, and in the lengthy review article below (currently in press for Historical Biology) you can find what I thought of it. Note that Glorified Dinosaurs is not especially new (it appeared in 2007): it typically takes a few years for lengthy written reviews of large books to see completion (or, ha, it does in my case anyway).
One more thing to note: some of what I say here (e.g., about the relationship between birds and other dinosaurs, about Alan Feduccia [et al.'s] claims, and about the strong morphological similarity between deinonychosaur-like birds and bird-like deinonychosaurs) will make familiar reading if you’ve read any of my stuff before (especially my review of Gary Kaiser’s The Inner Bird). Sorry about that, but the same points had to be made.
Glorified Dinosaurs: The Origin and Early Evolution of Birds, by Luis M. Chiappe, John Wiley and Sons, 2007, x + 263 pp., ISBN 0-471-24723-5
For all their current popularity as objects of research interest, fossil birds remain chronically under-represented in the popular literature. Only one book aims to cover all of avian palaeontology: Alan Feduccia’s The Origin and Evolution of Birds (1996, and republished 1999; itself an expanded version of Feduccia’s 1980 The Age of Birds [images of both books shown below]). However, Feduccia’s views on such topics as avian origins, the phylogeny and biology of Mesozoic birds, and the affinities of the major modern bird groups are idiosyncratic and do not accurately represent the status of palaeornithological knowledge. A significant gap in the market therefore remains. Until now perhaps, for Luis Chiappe’s new book – Glorified Dinosaurs: The Origin and Early Evolution of Birds – fills that gap for Mesozoic birds, at least. As I hope to show here, the book is beautiful, superbly written, authoritative and comprehensive.
Two things are emphasised from the beginning: a strong reliance on cladistics, and the dinosaurian origin of birds [Deinonychus shown here; by Arthur Weasley, from wikipedia. Like it or not, Deinonychus really did look like a giant, flightless Archaeopteryx]. Chiappe spends considerable time (103 of the book’s 263 pages) covering these subjects. Keen to get to the book’s extensive coverage of Mesozoic birds, I found the discussion of geological time, reptile evolution, and non-avialian dinosaur diversity over-long and unnecessary. Authors of palaeontological texts do of course have to set the main focus of their attention within the broader context of geological and evolutionary history, but if you’ve read a lot of popular texts on vertebrate evolution you end up feeling that you’ve heard the same story all too many times before.
As Chiappe shows, the evidence linking birds to other maniraptoran theropods is outstandingly good. He uses many of the recently discovered Cretaceous fossils from Liaoning Province and Mongolia to show how features once thought unique to birds all evolved earlier on in other maniraptorans. These features include morphological attributes such as complex feathers, a particular type of wrist folding, and distinctive eggshell microstructure, as well as aspects of brooding behaviour and the habit of laying egg clutches over many days.
The best evidence supporting the theropod origin of birds remains the detailed anatomy of maniraptorans and other coelurosaurs, and since the 1990s our knowledge and appreciation of coelurosaur anatomy has increased exponentially. New specimens of long-known taxa like Velociraptor have been described in detail, but we also have such new fossils as the oviraptorosaurs Caudipteryx, Protarchaeopteryx and Citipati, the troodontid Mei, and the dromaeosaurids Sinornithosaurus [the sinornithosaur NGMC 91 shown here] and Microraptor. Non-maniraptoran coelurosaurs like Sinosauropteryx and Dilong have shown that a simple, filamentous integument appeared before true feathers did, therefore providing fossil support for the model of feather origins proposed by Prum (1999). This discovery adds to the evidence indicating that feathers did not evolve from scales, but rather represent evolutionary novelties (Brush 1996).
An origin of birds from within coelurosaurian theropods would seem to suggest that bird flight originated on the ground, rather than among the trees. But the possibility that such maniraptorans as small dromaeosaurids and early birds were capable of at least some climbing still appears reasonable to some workers. Chiappe is well known for advocating the origin of flight in ground-running maniraptorans (Burgers & Chiappe 1999), and he includes discussion here of the wing-assisted running hypothesis. He is also highly critical of the idea that Archaeopteryx and other maniraptorans might have been scansorial or arboreal. Claims that Archaeopteryx possesses a claw geometry indicating an arboreal lifestyle (Feduccia 1993) are contradicted by newer analyses (Hopson 2001, Glen & Bennett 2007), and virtually all non-avialian maniraptorans lack features indicative of a climbing lifestyle [some very old drawings of archaeopterygids (and the Korean confuciusornithid arm) shown below].
Despite these arguments, it is likely that we will never be able to disprove the possibility that such maniraptorans as early birds, microraptorines and scansoriopterygids climbed at least occasionally; more importantly, such behaviour remains plausible based on our knowledge of living tetrapods that climb (some of which definitely lack climbing adaptations). Indeed, despite his initial argument, Chiappe does not dismiss the possibility that bird ancestry did involve the ascent of trees and other high places, and he ends this section of the book by discussing Dial’s wing-assisted incline running (WAIR) hypothesis in favourable terms.
I found the discussion of another controversial topic – manual digit homology – quite satisfying. The argument from embryology (that the tridactyl avian hand must represent digits II-IV) has never been sound, relying on the identification of ambiguous embryonic structures as putative digits, and on the conservation of the embryonic fourth digit as the primary axis of condensation in the developing hand. New data from Hox genes indicates that the digit that looks like a thumb in bird embryos really is a thumb (Vargas & Fallon 2005), in which case the primary axis of condensation has shifted to another digit.
Once you do get to the birds in Glorified Dinosaurs, you’re treated to sumptuously illustrated chapters on Archaeopteryx (Chapter 4), Rahonavis and other long-tailed forms (Chapter 5), the short-tailed, toothless confuciusornithids (Chapter 6), the diverse enantiornithine radiation (Chapter 7), flightless Patagopteryx and other stem-ornithuromorphs (Chapter 8), the bizarre marine hesperornithines (Chapter 9), and, finally, carinates and the origins and phylogeny of modern birds (Chapter 10) [adjacent composite shows, from top to bottom, Sapeornis, the enantiornithine Longipteryx (by Nobu Tamura, from wikipedia) and Patagopteryx (by FunkMonk, from wikipedia)].
Anyone who has been following our developing knowledge of Mesozoic birds for even just a few decades will know that the once enormous gap between long-tailed Archaeopteryx and the Late Cretaceous seabirds Hesperornis and Ichthyornis is now filled by a diverse assemblage of species, virtually all of which are short-tailed and hence united by most workers in the clade Pygostylia. Less well known is that a number of peculiar, long-tailed Lower Cretaceous birds now seem to help ‘fill the gap’ between Archaeopteryx and pygostylians; Chiappe’s book is one of the first non-technical sources to include substantial discussion and illustration of these forms.
Responding to the ‘Birds Are Not Dinosaurs’ movement (again)
One thing that everybody knows about the study of Mesozoic birds is that it is a field fraught with controversy and disagreement. As a confident cladist who has always emphasised the theropodan origins of birds, Chiappe has participated in numerous debates in the literature. These have involved Mesozoic bird biology, behaviour, relationships and origins, and have often been fought against a group of authors who contend that (1) birds are not theropod dinosaurs, but descend from another group of reptiles, (2) Archaeopteryx and other Mesozoic birds were much like modern birds in morphology and perhaps behaviour, (3) Archaeopteryx, confuciusornithids and enantiornithines are close relatives, forming a Mesozoic radiation (known as Sauriurae) that occurred in parallel with the one that led to modern birds, and (4) modern birds (neornithines) descend from an obscure group dubbed the ‘transitional shorebirds’ that underwent a major bottleneck at the end of the Cretaceous before exploding in diversity at the start of the Cenozoic.
Like most Mesozoic specialists, familiarity with the evidence leads me to conclude that these arguments are naïve, incorrect and based on misinterpretation or sheer ignorance. As discussed above, the morphological evidence nesting birds deep within coelurosaurian theropods is tremendously robust, the skeleton of Archaeopteryx shows that the earliest birds were much like their dromaeosaurid relatives, evidence for the monophyly of ‘Sauriurae’ is out-weighed by better evidence supporting a different topology, and fossil and molecular evidence indicate that the neornithine radiation did not involve hypothetical ‘transitional shorebirds’, and began during the Late Cretaceous, not after it.
Glorified Dinosaurs gives Chiappe a good chance to tackle the assertions made by other workers where they are contradicted by the evidence. I like the fact that he doesn’t pull his punches. Take the section on bird ancestry. Keen to find any Mesozoic non-dinosaurian reptile that might be a potential bird ancestor, Feduccia, Larry Martin, John Ruben and colleagues have proposed that the bizarre Triassic reptiles Cosesaurus, Megalancosaurus and Longisquama might somehow be involved in bird origins (Feduccia 1996, Jones et al. 2000) even though they are emphatically not bird-like and lack all of the characters shared by birds and other theropods [Megalancosaurus and Longisquama shown here, by me]. Chiappe sees red, dismissing each of these wonderful little creatures as potential protobirds in turn, concluding “In the end, claims for the origin of birds from this stock of small Triassic reptiles seems to adopt a formula more apt for the world of art than for scientific endeavour, as the identity of the object (the ancestor) is defended more by its symbolism than by its own physical attributes” (p. 39).
Including the alvarezsaurids
The inclusion of a chapter about alvarezsaurids might raise a few eyebrows given that nobody supports the inclusion of these animals within the bird clade anymore. The initial suggestion that these short-armed, long-legged maniraptorans were aberrant flightless birds was immediately rejected by some, mostly because Mononykus [shown above; photo by Thomas Cowart, from wikipedia] seemed just too weird to be a bird, but also because some of its bird-like features were deemed convergences resulting from a fossorial lifestyle (Zhou 1995). As Chiappe explains, these criticisms were never logical or satisfactory. Mononykus might indeed be weird compared to Archaeopteryx, but weird lineages have evolved in many clades. As for the idea that the bird-like characters of Mononykus result from convergence, this would need to be demonstrated, not just asserted in lieu of a favoured behavioural hypothesis. As Chiappe notes, the suggestion that alvarezsaurids might be birds only amounts to the position of the lineage with respect to the node shared by Archaeopteryx and neornithines. Perle et al. (1993) found Mononykus to be one step inside this clade, but a position one, two or three nodes away would hardly be outside a margin of error, even when Perle et al.’s phylogenetic hypothesis seemed favourable. It is only a substantive issue to those who regard birds and non-avialian theropods to be well apart on the tree of life.
Nevertheless, new data and new studies agree that alvarezsaurids are not birds, though exactly where they do belong within Coelurosauria remains contentious. So, it seems strange today to include alvarezsaurids within a book on Mesozoic birds, but it’s only right that – for historical reasons, at least – they be included. Numerous new taxa (including Shuvuuia, Parvicursor, Achillesaurus, Ceratonykus [skull shown here], Albertonykus, Xixianykus and Kol*), the recognition that some long-known specimens belong to the group, and studies of alvarezsaurid functional morphology have made this fascinating group the focus of continued attention.
* Jurassic Haplocheirus is an early member of the alvarezsaurid lineage, excluded from Alvarezsauridae by its describers.
The inclusion of Rahonavis from the Upper Cretaceous of Madagascar also looks somewhat peculiar. While originally described as a late-surviving relative of Archaeopteryx (Forster et al. 1998), more recent studies of maniraptoran phylogeny have found it to be a dromaeosaur closely allied to the South American taxa Buitreraptor and Unenlagia (Makovicky et al. 2005). I assumed that Rahonavis had – like the alvarezsaurids – been kept in the book for historical reasons, but it turns out that Chiappe (who is well aware of these recent studies and refers to them in his text) still thinks it likely that Rahonavis “ranks among the most primitively known birds”.
A few other maniraptorans included by Chiappe in his chapter on long-tailed birds may also not be birds. Jinfengopteryx was originally described as another close relative of Archaeopteryx. However, with its closely packed teeth, proportionally robust snout and short forelimbs, Jinfengopteryx looks likely to be a troodontid (again, Chiappe is aware of this and mentions it in passing). Highlighting the great similarity between basal birds and the early members of closely related lineages is the fact that another small, early troodontid – Anchiornis – was also originally described as an early bird [adjacent Anchiornis illustration by Matt Martyniuk. Spectacular feathered specimens show that the animal really did look this like. More proof, if ever if were needed, that early members of the lineages close to birds were extremely bird-like].
There are a lot of confuciusornithid fossils these days
Among the most significant of Mesozoic bird discoveries made within recent years is that of huge numbers (possibly thousands) of the Early Cretaceous Chinese bird Confuciusornis. The enormous sample known for this taxon has provided us with a wealth of information on its palaeobiology, though again there are major disagreements between what you might regard as the ‘two schools’ of Mesozoic palaeornithology. Chiappe takes issue with the idea that Confuciusornis was a tree-climber that walked with a primate-like, erect-bodied pose. He also argues that the proportions of its toes indicate a ground-foraging lifestyle, not that of a percher. While the data indicating a ground-foraging habitus for Confuciusornis appears reasonable (Hopson 2001), the bird remains an enigma, as stomach contents show that it ate fish (Dalsätt et al. 2006): a diet difficult to reconcile with a supposed ground-foraging lifestyle [life restoration of Eoconfuciusornis below; by Nobu Tamura, from wikipedia. There is some doubt over the distinction of Eoconfuciusornis relative to Confuciusornis].
The reasonable amount of variation observed among the many Confuciusornis specimens has predictably resulted in suggestions that several species might be present, and that sexual dimorphism is evident. However, the morphological features used to support the validity of some of the additional species are, Chiappe argues, based on misinterpretation. One species – the apparently distinct C. dui (notable for its slightly upcurved upper jaw) – was named for a specimen kept in a private collection. Chiappe notes that the large amount of size variation present in Confuciusornis (interpreted by some as support for the multi-species model) might simply be indicative of slower growth than that seen in neornithines, resulting in the presence of subadult individuals that are living independently and alongside skeletally mature individuals. The same, Chiappe argues, might be true of Archaeopteryx and other non-neornithine Mesozoic birds.
In a few places, I do feel that Chiappe spends too much time on issues that could have been reviewed more succinctly. One example concerns his section on the long tail feathers present in some Confuciusornis specimens [long-feathered Confuciusornis shown below; by Laikayiu, from wikipedia]. This seems to stretch on for about three pages, the main point being that we cannot be sure that these long plumes are really evidence of sexual dimorphism. A series of to-ings and fro-ings in the technical literature have thrashed this issue to death with no obvious resolution (Chiappe et al. 2008, 2010, Peters and Peters 2009, 2010).
The chapter on enantiornithines does a good job of reviewing the substantial diversity now recorded for this clade. Species within this Cretaceous group ranged from the size of a finch to that of a turkey vulture, and the anatomy of their feet and rostra suggest specialisation in some lineages for wading, mud-probing, swimming, perching, fish grabbing, seed-eating and even sap-eating. The sections on hesperornithines and Ichthyornis collate a great deal of information otherwise only available in the technical literature. The volume ends with a discussion of neornithine origins. At least some neornithine clades have their roots in the Cretaceous, but the Neogene radiation of perching birds and so many others is – understandably – mentioned only in passing.
Chiappe’s writing style is very enjoyable and the editing is of excellent standard. The many diagrams and photographs really are superb and the book is a visual feast, packed with huge, wonderful images (printed on high-quality glossy paper) of most of the relevant specimens. There are a few minor glitches in some of the diagrams: spaces surrounding skeletons were not correctly in-filled by the background colour. Regarding the artwork, the few reconstructions produced by Ed Heck look too cartoony, while the cover art (depicting a pot-bellied, sunken-faced dromaeosaur and a confusiuornithid with fictional wing-spurs rather than clawed fingers) bears the hallmark of an artist unfamiliar with the animals they were aiming to depict. Everything else, however, really does look great [skeleton of the rather poorly understood Chinese Cretaceous bird Jibeinia luanhera shown below].
A few details in the book are inaccurate; most concern the non-birds Chiappe discusses in the introduction. The name Lagosuchus talampayensis is used for the animal now known as Marasuchus (the Lagosuchus holotype is non-diagnostic and a referred specimen – typifying the animal that everyone had in mind when they were discussing ‘Lagosuchus‘ – was named as the new taxon Marasuchus by Sereno and Arcucci (1994)). The archaic saurischian Herrerasaurus is said, incorrectly, to exhibit skeletal pneumaticity. Finally, Chiappe uses the term ‘iguanodontids’ for the ornithopod clade that includes Camptosaurus, Iguanodon and the hadrosaurs: if Iguanodontidae is to be used at all, it must be restricted to the small clade that includes Iguanodon and its closest relatives; the group Chiappe is referring to is either Iguanodontia, or its sub-group Ankylopollexia (sometimes called Camptosauria).
Glorified Dinosaurs: The Origin and Early Evolution of Birds does not disappoint. Written by one of the world’s leading experts on Mesozoic birds, it is comprehensive in its coverage and lavishly illustrated. It should be obtained by everyone interested in avian history and origins, but will also be enjoyed by people interested in birds in general. Now for the production of a volume that provides similar treatment to the far more substantial Cenozoic avian record!
Glorified Dinosaurs: The Origin and Early Evolution of Birds
For previous Tet Zoo articles on Mesozoic birds (and alvarezsaurids and such), and on some of the controversies surrounding them, see…
- Tet Zoo picture of the day # 24 [on archaeopterygids]
- The new Crato Formation enantiornithine
- A stunning new Mesozoic bird… well, new-ish
- Epidexipteryx: bizarre little strap-feathered maniraptoran
- A month in dinosaurs (and pterosaurs): 2, of alvarezsaurids and avialians
- Cyril Walker
- Limusaurus: awesome and wonderful, with or without the hands (includes discussion of manual digit homology)
- Publishing with a hidden agenda: why birds simply cannot be dinosaurs (on the ‘birds are not dinosaurs’ movement)
- The Mesozoic birds with weird, plastic-strip-style tail structures
- Alexornis and other ‘alexornithiforms’
- Aberratiodontus: worst paper ever?
- The Cretaceous birds and pterosaurs of Cornet: part I, the birds
And for previous Tet Zoo book reviews relevant to Mesozoic birds, see…
Refs – -
Brush, A. H. 1996. On the origin of feathers. Journal of Evolutionary Biology 9, 131-142.
Burgers, P. & Chiappe, L. M. 1999. The wing of Archaeopteryx as a primary thrust generator. Nature 399, 60-62.
Chiappe, L. M., Marugán-Lobón, J., Ji. S. & Zhou, Z. 2008. Life history of a basal bird: morphometrics of the Early Cretaceous Confuciusornis. Biology Letters 4, 719-723.
Chiappe, L. M., Marugán-Lobón, J. & Chinsamy, A. 2010. Palaeobiology of the Cretaceous bird Confuciusornis: a comments on Peters & Peters (2009). Biology Letters 6, 529-530.
Dalsätt, J., Zhou, Z., Zhang, F. & Ericson, P. G. P. 2006. Food remains in Confuciusornis sanctus suggest a fish diet. Naturwissenschaften 93, 444-446.
Feduccia, A. 1993. Evidence from glaw geometry indicating arboreal habits of Archaeopteryx. Science 259, 790-793.
Feduccia, A. 1996. The Origin and Evolution of Birds. Yale University Press: New Haven & London.
Forster, C. A., Sampson, S. D., Chiappe, L. M. & Krause, D. W. 1998. The theropod ancestry of birds: new evidence from the Late Cretaceous of Madagascar. Science 279, 1915-1919.
Glen, C. L. & Bennett, M. B. 2007. Foraging modes of Mesozoic birds and non-avian theropods. Current Biology 17, 911-912.
Hopson, J. A. 2001. Ecomorphology of avian and nonavian theropod phalangeal proportions: implications for the arboreal versus terrestrial origin of bird flight. 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. Yale University (New Haven): Peabody Museum of Natural History. p. 211-235.
Jones, T. D., Ruben, J. A., Martin, L. D., Kurochkin, E. N., Feduccia, A., Maderson. P. F. A., Hillenius, W. J., Geist, N. R. & Alifanov, V. 2000. Nonavian feathers in a Late Triassic archosaur. Science 288, 2202-2205.
Makovicky, P. J., Apesteguía, S. & Agnolín, F. L. 2005. The earliest dromaeosaurid theropod from South America. Nature 437, 1007-1011.
Perle, A., Norell, M. A., Chiappe, L. M. & Clark, J. M. 1993. Flightless bird from the Cretaceous of Mongolia. Nature 362, 623-626.
Peters, W. S. & Peters, D. S. 2009. Life history, sexual dimorphism and ‘ornamental’ feathers in the Mesozoic bird Confuciusornis sanctus. Biology Letters 5, 817-820.
Peters, W. S. & Peters, D. S. 2010. Sexual size dimorphism is the most consistent explanation for the body size spectrum of Confuciusornis sanctus. Biology Letters 6, 531-532.
Prum, R. O. 1999. Development and evolutionary origin of feathers. Journal of Experimental Zoology 285:291-306
Sereno, P. C. & Arcucci, A. B. 1994. Dinosaurian precursors from the Middle Triassic of Argentina: Marasuchus lilloensis, gen. nov. Journal of Vertebrate Paleontology 14, 53-73.
Vargas, A. O. & Fallon, J. F. 2005. Birds have dinosaur wings: the molecular evidence. Journal of Experimental Zoology (Mol Dev Evol) 304B, 86-90.
Zhou, Z. 1995. Is Mononykus a bird? The Auk 112, 958-963.
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