Okay, but pneumatic depressions seem to be present: [ref] p.
144: "The centrum [of the anteriormost preserved caudal, presumably
caudal 1] is transversely compressed, [...] and the excavation present
laterally on the base of the neural spine coincides with that seen in the last
sacral vertebra. [...] The centrum exhibits an elongate excavation
laterally." This makes sense considering that oviraptorosaur anterior
to mid-caudals as well as those of many extant birds are pneumatized. (True
pleurocoels = pneumatic foramina are present on a cervical, depressions like
mentioned above on mid-dorsals.)
Reference: Fernando E. Novas: Anatomy of Patagonykus
puertai (Theropoda, Avialae, Alvarezsauridae), from the Late Cretaceous of
Patagonia, JVP 17(1): 137 -- 166 (March
1997)
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