YouTube.com brings us a 95-minute presentation
on the history of the discovery of Mesozoic birds by Dr. Jingmai O’Connor
O’Connor notes historic difficulty in defining birds
starting with Huxley (1868) who said Archaeopteryx was a bird and a theropod dinosaur, but that hypothesis fell out of favor.
Then, DeBeer (1954) ‘Pulled a Larry Martin‘ by listing traits restricted to birds that turned out to be more widely distributed in dinosaurs that were described after 1954.
Then, Ostrom (1969a, b) described Deinonychus as an Archaeopteryx relative, but one that lived later, in the Early Cretaceous, so that was considered temporal discontinuity in the pre-software days of phylogenetic analysis.
Finally, the deluge of Chinese bird fossils is what tipped the paleo-community toward Huxley’s and Ostrom’s correct hypotheses, according to O’Conner. And sadly, belatedly, she’s correct.
O’Connor supports the hypothesis that birds are living troodontids,
but she mistakenly includes the scansoriopterygid bird, Mei long, and pre-bird anchiornithids. These are not troodontids in the LRT (Fig. 2) as we learned just a few days ago here. Moreover, O’Connor mistakenlynests all 13 Solnhofen birds into Archaeopteryx, thereby missing out on the variation that was present on those Late Jurassic islands.
O’Connor looked at members of the Scansoriopterygidae
and noted cladistic analysis puts them most closely related to birds.
In the LRT scansoriopterygids ARE birds, some experiencing reversals.
O’Connor brought up and bought into the Yi qi and Ambopteryx rmembrane wing hypothesis. That misidentified entirely new bone (not found in any preceding tetrapod) is just a displaced forearm bone (Fig. 1), an ulna in the case of Ambopteryx, which lacks a matching novel elongate wrist bone on the articulated right wing where the ulna is EXACTLY as long and wide as the left disarticulated ulna (= se or styliform element). The left radius was split lengthwise during crushing causing it to be misidentified as two extremely thin ante brachial bones, which is just silly and untenable.
By the way,
misinterpreting a broken bone is not pseudoscience. It’s a simple mistake.
According to O’Connor,
pre-wings developed for sexual selection. As proto-wings the forelimbs had incipient flying abilities (thrust + lift). That’s is widely agreed upon, even here. She cites Ken Dial’s studies on pre-volant birds flapping while climbing near-vertical tree trunks.
O’Connor believes there were 3 to 5 separate origins of flight
- Yi qi and Ambopteryx
- and one other due to be described in an upcoming paper.
A more comprehensive, wider-gamut phylogenetic analysis
would help Dr. O’Connor. She would not need to ‘Pull a Larry Martin‘ by seeking a single ovary in fossils (some fossorial snakes also lose one ovary) and a crop (pre-stomach with stones might also be found in plesiosaurs) as the only remaining traits she found unique to birds not otherwise found in dinosaurs. Traits don’t matter. Where a taxon or clade nests is all that matters. The last common ancestor (LCA) of all birds is also a bird, by definition.
If you want to list the traits of that LCA taxon,
you may, but you should note where convergence appears in unrelated taxa (i.e. just take a look at the distribution of toothed taxa in Fig. 2).
de Beer GR 1954. Archaeopteryx lithographica: a study based upon the British Museum specimen. Trustees of the British Museum, London.
Huxley TH 1868. On the animals which are most nearly intermediate between birds and reptiles. Geol. Mag. 5: 357–65.; Annals & Magazine of Nat Hist 2, 66–75; Scientific Memoirs 3, 3–13.
Ostrom JH 1969a. A new theropod dinosaur from the Lower Cretaceous of Montana. Postilla. 128: 1–17.
Ostrom JH 1969b. Osteology of Deinonychus antirrhopus, an unusual theropod from the Lower Cretaceous of Montana. Peabody Museum of Natural History Bulletin. 30: 1–165.
Ostrom JH 1976. Archaeopteryx and the origin of birds. Biological Journal of the Linnean Society 8 (2): 91–182.