Is Archaeopteryx a bird or not?

Just before Christmas I was inspired by a post by Jon Tennant on his blog, To bird or not to bird… about whether anyone knows whether Archaeopteryx lithographica is a bird or not a bird. Amongst palaeobiologists and biologists Archaeopteryx is the poster organism for evolution and if you’ve ever been to a natural history museum you’ve undoubtedly walked past a cast or two, it is after all one of our Bingo! animals. It was the first fossil that really enshrined the ideas about evolutionary change. Ever since it’s discovery in 1861 (although Archaeopteryx fossils were discovered before then but not recognised as such) it’s almost a rite of passage for palaeontologists to have a ponder or even publish trying to work out the affinities of the animal. Is it a bird? It’s probably not a plane. Is it a reptile? Is it a dinosaur? (and yes smarty pants I know you can be all three).

The scientific techniques used to work out the affinities of animals only known from fossil remains have developed greatly over the last 150 years yet the answer to this question still seems far from being resolved.

For many years, I’ve joked with colleagues that we need to make a lever like this to put in front of the Grant Museum’s Archaeopteryx cast and change it every time that a new paper decides one way or the other whether or not Archaeopteryx is a bird or not. I may pop down to the Institute of Making one of these days to turn this plan into a working prototype.

You’d think it would be easy to determine one way or another from characters shown in the dozen or so fossils of Archaeopteryx but here’s a breakdown of various authors’ designations of the animal. You’ll spot a few of the heavy hitters on the list. As I mentioned above, everyone’s had a punt at answering this question over the years. This information is largely sourced from UCL evolutionary embryologist Sir Gavin De Beer’s 1954 monograph on Archaeopteryx printed by the British Museum (Natural History) as it was known then. I’ve added links to biographies for some of the well known names and the more recent additions I’ve cobbled together myself.

Archaeopteryx, bird, non-avian, non-mammalian reptile or something else?

1857 The very first Archaeopteryx specimen, the Haarlem specimen is identified as a pterodactyl and remains so until 1970.
1861 J.A.Wagner, reptile. H. von Meyer, bird. There was disagreement straight off the bat, Wagner described the first skeleton as a feathered pterosaur.
1862 H. von Meyer, bird. H.Woodward,  bird. A. Oppel German Palaeontologist with a bit of the moon and a shrimp named after him, bird.
1863 D.F.Weinland, intermediary between reptiles and birds. R.Owen for it is he!, bird. J.D. Dana, bird. A. Milne Edwards, a bird related to chickens.
1864 E.E.Deslongchamps, bird.
1865 J.Edwards, bird.
1866 E.Haeckel, bird. O.des Murs, a swimming bird.
1867 T.H.Huxley, bird.
1868 T.H.Huxley, bird (two papers this year). J.V.Carus, bird.
1870 A.R.Wallace beating Charles Darwin to the punch (see below), bird.
1872 C.Darwin for it is he! bird. C.J.Sundervall, bird.
1877 K.Müller, bird.
1878 C.Gegenbaur, intermediary between reptiles and birds. R.Widersheim, intermediary between reptiles and birds.
1879 E. de Selys-Longchamps, reptile. C.Vogt, intermediary between reptiles and birds. E.Haeckel, bird. H.A. Nicholson, bird.
1880 A. Reichenow, intermediary between reptiles and birds. O.C.Marsh of ‘bone wars’ fame, bird.
1881 L.Dollo of Iguanodon and Dollo’s law fame, reptile. O.C.Marsh, bird. H.G.Seeley, bird.
1882 T.J.Parker, intermediary between reptiles and birds.
1883 R.Widersheim, intermediary between reptiles and birds (a second time). M.Fürbinger, bird.
1884 R.Widersheim, intermediary between reptiles and birds (third time lucky). R.Hoernes, bird. W.Dames, bird. W.A.Forbes, bird.
1885 R.Widersheim, intermediary between reptiles and birds (fourth time’s a charm). H.Woodward. Bird. M.Fübinger, bird. Fr.Aug.Quenstedt, bird. A.Newton, bird. B.Vetter, bird. G.Baur, bird. A.Pavlow, bird.
1886 R.Widersheim, intermediary between reptiles and birds (fifth time of trying).
1887. G.Baur, changing his mind from 1885, intermediary between reptiles and birds. M.von Menzbier, bird.
1888. M.Fübinger (a third paper), bird.
1908 W.Branca, intermediary between reptiles and birds.
1910 W.P.Pycraft, bird.
1919 O.Abel, bird.
1921 B.Petronievics, bird.
1925 F.Tornier, reptile.
1929 A.Wetmore, bird.
1933 K.Lambrecht, bird.
1935 P.R.Lowe, reptile.
1938 B.W.Tucker, a bird close to the true line to birds.
1941 M.Reichel, bird.
1944 P.R.Lowe, reptile (again).
1946 G.G.Simpson, a bird in the true line to birds.
1953 T.Felsztyn, reptile.
1954 G. de Beer, bird.
[Jumping nearly 30 years of similar bird, reptile, intermediary publishings]
1986 J. Gauthier, bird.
1999 P.C.Sereno, bird.
2000 T.R. Holtz Jr., bird.
2001 M.A.Norrell, J.M.Clark & P.J.Makovicky, bird.
2002 X.Xu, bird.
2003 O.W.M. Rauhut, bird.
2004 Z.Zhou, bird.
2007 A.H. Turner, D. Pol, J.A. Clarke, G.M. Erickson & M.A. Norell, bird. P. Senter, bird.
2008 F. Zhang, Z. Zhou, X. Xu, X. Wang & C. Sullivan, bird.
2010 X. Xu, Q.Y. Ma, & D.Y Hu, bird.
2011 Xing X, Hailu Y, Kai D & Fenglu H, not a bird, a Deinonychosaurian dinosaur. Barret, P, bird.
2012 M.S.Y. Lee, T.H.Worthy, bird.
2013 M.R.Spencer, E.Wilberg, maaaaaaaaybe a bird depending (and the subject of the original To bird or not to bird blog).

This list is by no means complete and the missing 30 year gap and a key period in dinosaur/bird palaeontology contains hundreds of references plumping for either bird or (non avian) reptile but you get the idea. Archaeopteryx has always been a contentious animal. Here we’re looking at whether it’s a bird or not but other areas of discussion are whether or not it was the first bird (dependent of course on whether it is a bird or not) and the flight capabilities of the animal. When it comes to the idea of scientific consensus, Archaeopteryx nicely highlights that even for a species studied so intensely over the last 150 years there’s far from a cut and dry consensus, although there are a higher number of authors going for bird in this extremely limited data set.

The Pressing Question

Returning to the original question. Is Archaeopteryx a bird or not? The ‘answer’ currently is tentatively probably yes but we’ll see what the next 150 years of research has in store for the original transitional fossil.

References.
Beer, Sir Gavin De. 1954. Archaeopteryx lithographica, a study based upon the British Museum specimen. London : British Museum, Natural history.
Xing, Xu., Hailu, You., Kai, Du & Fenglu, Han. 2011. An Archaeopteryx-like theropod from China and the origin of Avialae. Nature 475, 465–470.

Mark Carnall is the Curator of the Grant Museum of Zoology