A field guide to mesozoic birds and other winged dinosaurs

Ostrom’s Menace-from-the-Clouds Bird Rahonavis ostromi
Time: 70 Ma ago Location: Mahajanga, Madagascar Habitat: Maevarano Formation Size:
WS >80cm (2.6ft); BL ~80cm (2.6ft); TL unknown Features: Very small compared to other
unenlagiines & relatively primitive, possibly representing a holdover from the ancestral
form. Wings very large. Legs long, with unreversed hallux & hyperextendable sickle clawed
second toe. Frond tail relatively short compared to the similar-looking microraptorians.
Biology: The very long, powerful wings bearing quill knobs suggest these were capable of
some limited flapping flight. Chiappe (2007) noted that like other unenlagiines, the wing
could be raised more vertically than in related groups, allowing them to flap. A primitive
powered flying stage for Unenlagiinae as a whole could help explain their distribution in
the southern hemisphere, which was not connected by land to the north during the Cretaceous.
R. ostromi was among the last of the aerial long-tailed birds.
Herman’s Tim Mimic Timimus hermani
Time: 106 Ma ago Location: Victoria, Australia Habitat: Eumeralla Formation, floodplains
and braided rivers in a temperate and seasonally cold antarctic environment. Size:
WS unknown; BL ~3m (9.8ft); TL unknown Features: Known only from isolated leg bones
& vertebrae, they indicate a large animal w/ long, slender legs adept at running. Biology:
Originally considered an ornithomimid, these are more likely eumaniraptorans, probably
unenlagiines.
Comahue Half Bird Unenlagia comahuensis
Time: 89 Ma ago Location: Neuquen, Argentina Habitat: Portezuelo Formation Size: WS
unknown; BL ~3m (9.8ft); TL unknown Features: Very large flightless unenlagiines w/
small but highly mobile wings. Internally, large ridge on deltopectoral crest supporting
strong wing musculature. Biology: Probably similar in ecology to other unenlagiines.
Paynemil’s Half Bird Unenlagia paynemilli
Time: 89 Ma ago Location: Neuquen, Argentina Habitat: Portezuelo Formation Size:
WS unknown; BL ~2.2m (7.4ft); TL unknown Features: Similar to U. comahuensis & also
known from fragmentary material. It differed in some internal anatomy of the shoulder
girdle & hip bones, & appears to have been smaller. Biology: Probably similar in ecology
to other unenlagiines.
94