Misinterpreting Zhongornis

A few years ago
O’Connor and Sullivan 2014 took another look at a small bird-like theropod, Zhongornis, originally identified as a bird. They thought they saw “striking resemblances to both Oviraptorosauria and Scansoriopterygidae.” According to Wikipedia, “The authors reinterpreted Zhongornis as the sister taxon of scansoriopterygids, and further suggested that this clade (Zhongornis + Scansoriopterygidae) is the sister group of Oviraptorosauria.”

The original paper by Gao, et al. 2008
(O’Connor was a co-author) considered Zhongornis a bird, “the sister group to all pygostylia,” which is an invalid clade in the LRT. Several disparate clades developed pygostyles in the LRT.

Figure 4. Confuciusornithiformes to scale. Note the lack of a pygostyle in the majority of taxa.

Figure 4. Confuciusornithiformes to scale. Note the lack of a pygostyle in the majority of taxa.

By adding more relevant taxa,
in the large reptile tree (LRT, 1315 taxa) Zhongornis nested between Archaeopteryx (= Wellnhoferia) grandis and Confusciusornis (Fig. 1). Scansoriopterygids, in the LRT, are descendants of the Solnhofen bird, ‘Archaeopteryx‘ #12.

Figure 2. Zhongornis in situ.

Figure 2. Zhongornis in situ, skull reconstructiion, pes, manus and tail.

Zhongornis haoae (Gao et al. 2008; D2455; Early Cretaceous). Lack of fusion and bone texture indicate the Zhongornis holotype is a juvenile. The femoral heads and necks are not visible, perhaps not yet ossified. Even so, the wing feathers are well-develped, so the specimen is not a hatchling, but close to fledging, according to Gao et al.

Figure 3. Zhongornis pectorals as traced here and as traced by O'Connor and Sullivan (right).

Figure 3. Zhongornis pectorals as traced here and as traced by O’Connor and Sullivan (right).

The problem with the O’Connor and Sullivan paper was…
taxon exclusion. They did not test all Solnhofen birds, but considered them all Archaeopteryx and selected one to test. They did not realize that various Solnhofen birds are basal to ALL later bird clades, even those that gave up flying and grew to large to fly.

Figure 4. Zhongornis pelvic and tail area as traced here and as traced by O'Connor and Sullivan.

Figure 4. Zhongornis pelvic and tail area as traced here and as traced by O’Connor and Sullivan. The red bones are pubes. The green ones are ilia or impressions thereof.

We talk about elongate coracoids
when we talk about birds (Aves).

O’Connor and Sullivan 2014 report, “The coracoid is not well-preserved and is largely overlapped by other elements, making it difficult to confirm the original description (Gao et al., 2008) of this bone as strut-like; in DNHM D2456 it appears short, robust, and trapezoidal, a primitive morphology that characterizes oviraptorosaurs and scansoriopterygids, as well as dromaeosaurids, troodontids, Archaeopteryx and sapeornithiforms.”

In contrast
Zhongornis clearly has two elongate, barbell-shaped coracoids (Fig. 3), as in Confuciusornis.

In ReptileEvolution.com the coracoids of scansoriopterygids and Archaeopteryx have elongate coracoids. By contrast, Sapeornis and other sapeornithiforms have relatively short coracoids, reduced along with the forelimbs as the body size increased. This is sometimes called a reversal. Short coracoids can also be found in extant flightless birds.

Don’t judge or nest a taxon on just a few or a few dozen traits.
Always let the unbiased software place the taxon. To put limits on your taxon list.

References
Gao C-L, Chiappe LM, Meng Q-J, O’Connor JK, Wang X, Cheng X-D and Liu J-Y 2008. A new basal lineage of early Cretaceous birds from China and its implications on the evolution of the avian tail. Palaeontology 51(4):775-791.
O’Connor J-M and Sulivan C 2014.
Reinterpretation of the Early Cretaceous maniraptoran (Dinosauria: Theropoda) Zhongornis haoae as a scansoriopterygid-like non-avian, and morphological resemblances between scansoriopterygids and basal oviraptorosaurs. Vertebrata PalAsiatica 52(1)1–9.

wiki/Changchengornis
wiki/Confuciusornis
wiki/Zhongornis

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