The origin of giant ‘birds’: Tyrannosaurus, a giant Zhenyuanlong

Today we conclude our foray into giant birds with a non-bird.
I could not resist this one. Today’s taxa are not birds, but very convergent. Hope you like it as we revisit the very bird-like Zhenyuanlong, with its long wing feathers, and its giant descendant, Tyrannosaurus rex (Fig. 1). We looked at this heretical pair revealed by phylogenetic analysis for the first time in the large reptile tree earlier here.

Figure 1. Zhenyuanlong compared to scale with the foot of T-rex and a another overall view of T-rex to a similar overall length.

Figure 1. Zhenyuanlong compared to scale with the foot of T-rex and a another overall view of T-rex to a similar overall length.

Tyrannosaurus rex (Osborn 1905) Late Cretaceous, 65 mya, 12.3 m in length, was derived from a sister to Sinocalliopteryx and was a sister to bird-like dinosaurs in the large reptile tree. Several varieties are known. Some are more robust. Others are gracile and smaller.

Zhenyuanlong suni (Lü and Brusatte 2015, JPM-0008) Early Cretaceous, 122 mya, over 1m in length, was derived from a sister to Tianyuraptorand is an ancestral sister to Tyrannosaurus. The fossil preserves wing feathers and so was considered the largest of the Chinese winged dromaeosaurs. Click here to see the list of traits shared with tyrannosaurs not with dromaeosaurs and to learn more. Note the short torso and tall, narrow orbit. This fossil shows that tyrannosaurs once had flight feathers.

We also looked at
the tiny arms of T-rex earlier here. They were tiny wings.

Figure 0. Taxa ancestral to tyrannosaurs beginning with the CNJ7 specimen of Compsognathus.

Figure 0. Taxa ancestral to tyrannosaurs beginning with the CNJ7 specimen of Compsognathus.

References
Lü J and Brusatte SL 2015. A large, short-armed, winged dromaeosaurid (Dinosauria: Theropoda) from the Early Cretaceous of China and its implications for feather evolution. Scientific Reports 5, 11775; doi: 10.1038/srep11775.
Osborn HF 1905. Tyrannosaurus and other Cretaceous carnivorous dinosaurs. Bulletin of the AMNH (New York City: American Museum of Natural History) 21 (14): 259–265.

wiki/Tyrannosaurus
wiki/Zhenyuanlong

2 thoughts on “The origin of giant ‘birds’: Tyrannosaurus, a giant Zhenyuanlong

  1. I was looking at a bird today, and it occurred to me that a wing-claw/digit or two could still be very useful and needn’t really impede flight significantly. So what was the evolutionary ‘filter’ that removed them? Could the tiny and possibly almost non-functional hands of _T. rex_ somehow provide a clue, since the same factor(s) may have worked in parallel here ???

  2. Several birds retain wing claws actually. Rhea (the rhea), Anser (the goose), Coccyzus (the cuckoo) and the screamer (Chauna) among others. All are able to flap and strike enemies and only the cuckoo is arboreal, not to mention hoatzin juveniles (Opisthocomus). Given present data, when birds became arboreal they no longer were beset by enemies that could be struck with flapping wings. Not a hard fast rule. Just a trend and a hypothesis looking for validation with exceptions at this point.

    Your thoughts?

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