Pronunciation: eh-ro-stee-on Meaning: Air bone Author/s: Sereno, Martinez, et al. (2009) Synonyms: None known First Discovery: Neuquen, Argentina Chart Position: 549
An allosauroid, specifically a neovenatorid allosauroid, and more specifically a megaraptoran neovenatorid allosauroid (though a position in Tyrannoauridae has recently been mooted), Aerosteon was a big boy at around nine meters in length, but was a bit of a lightweight because of what bods call "extensive pneumatization"—air holes in its bones—which prompted a bit of argy-bargy between lead author Paul Sereno and Matt Wedel. We won't bore you with details, link suffice to say no punches were pulled during heated handbag-throwing, but sadly none were thrown either, as is always the case when paleontologists puff their chests out. And speaking of puffing chests out; apparently Aerosteon couldn't because, unlike mammals, theropods had rigid lungs, so they needed another way to breathe.
In a manner similar to modern birds, Aerosteon's breathing seems to have been undertaken by a series of air sacks in its thorax and abdomen that bellowed air in a one way stream through a pair of fairly rigid lungs. The name-prompting "pneumaticity" was caused by outpockets of said air sacks invading the surrounding bones, thus reducing their weight. In birds, this bellow or "flow-through" system also provides a continuous airflow to power the insane metabolic rate required for powered flight, though how, or if, this feature would, or could, benefit an apex predator that weighed as much as a white rhino eludes us.
(Air bone from Rio Colorado) EtymologyAerosteon is derived from the Greek "aeros" (air) and "osteon" (bone) because of what bods call "pneumatized" bones—cavities in some of its bones, like the bubbles in an "Aero" chocolate bar, which would have been filled with air from invading air sacks attached fore and aft to its lungs. The species epithet, riocoloradensis, means "from Rio Colorado" in Latin. However, adjectives ending in "-ensis" may be either masculine or feminine, not both nor either, and as the Greek "osteon" is neuter gender the epithet must be neuter also. The correct epithet should be riocoloradense.[ref]
DiscoveryThe remains of Aerosteon were discovered at Cañadon Amarillo in the Anacleto Formation, (Río Colorado Subgroup, Neuquén Group), 1 km north of the Río Colorado near the southern border of Mendoza Province, Argentina, in 1996.
The holotype (MCNA-PV-3137) is a partial skeleton.