A field guide to mesozoic birds and other winged dinosaurs

Rare Hand Lizard Elmisaurus rarus
Time: 70 Ma ago Location: Omnogovi, Mongolia Habitat: Nemegt Formation (see above)
Size: WS unknown; BL ~1.8m (6ft); TL unknown Features: Known from wings, feet, &
possibly a partial skull. Distinguished from Chirostenotes pergracilis by the presence of
unique internal anatomy including a vascular opening in the tarsus & a prominent muscle
attachment point at the ankle. Biology: Probably similar to Chirostenotes and/or Avimimus
in terms of ecology. This was the first caenagnathid species known from both wing & foot
bones, allowing the various pieces of Chirostenotes (previously attributed to different animals)
to be brought together.
Thin Narrow Hand Chirostenotes pergracilis
Time: 75 Ma ago Location: Alberta, Canada Habitat: Dinosaur Park Formation, seasonally
arid lowland plains dominated by braided river systems and small forests. Size: WS
unknown; BL ~1.5m (5ft); TL unknown Features: Known from isolated jaw, hands & hind
legs, but very similar to (though significantly smaller than) the later Lancian caenagnathids.
Lower jaw wide but narrow when viewed from the side, w/ long, slightly up-curved
beak. Upper jaw unknown, but likely similar to the Lancian species, w/ broad, somewhat
spoon-shaped bill. Alular digit short & stout w/ large, curved claw. Major & minor digits
long & relatively slender. Internally characterized by a middle metatarsal with a diamondshaped
cross-section. Biology: As with some other caenagnathids, two varieties are known
for this species: a slender morph and a robust morph. The slender morph has been given its
own name, Chirostenotes elegans, but the difference is probably due to sex.
Currie’s Higher Narrow Hand Epichierostenotes curreii
Time: 72 Ma ago Location: Alberta, Canada Habitat: Horseshoe Canyon Formation, seasonally
arid lowland plains dominated by braided river systems and small forests. Size: WS
unknown; BL ~1.7m (5.7ft); TL unknown Features: Known from a partial skeleton, very
similar to Chirostenotes pergracilis, differing only in size and time period, as far as it’s possible
to tell. Biology: Probably a direct descendant species of C. pergracilis.
Lancian Recent Jaw No scientific name (specimen number FMNH PR2081)
Time: 65.5 Ma ago Location: South Dakota, USA Habitat: Hell Creek Formation. Forested
near-coastal flood plains dominated by flowering shrub species and coniferous trees.
Size: WS >2m (6.6ft); BL 3.7m (12ft); TL unknown Features: Very large. Head long w/
prominent, large rounded casque. Beak straight but broad & rounded. Neck relatively long,
though not as long as some oviraptorids. Wings large & clawed. Legs long, but feet relatively
small. Tail short but very deep, with fused vertebrae at the tip. Biology: The fused,
pygostyle-like tail vertebrae may imply a large tail fan or may simply be the byproduct of
tail shortening. The broad, flat bill w/ straight edges suggests a mostly herbivorous diet,
though some degree of omnivory is likely, as in other caenagnathiformes. Chirostenotes
elegans specimens have been reported from the same formation, despite the ten million
years chronological gap. As with C. pergracilis, these “C. elegans” specimens probably represent
the smaller, more slender females of this species.
72