A field guide to mesozoic birds and other winged dinosaurs

Ostrom & Mays’ Utah Predator Utahraptor ostrommaysorum
Time: 126 Ma ago Location: Utah, USA Habitat: Yellow Cat Member, Cedar Mountain
Formation. Open, marshy mud flats. Size: WS unknown; BL ~6.5m (21.3ft); TL unknown
Features: Legs short & powerful. Very large sickle claws. Tail relatively long. Biology: One
of the largest known winged dinosaur species. Probably carnivores specializing in large
prey such as ornithopods & juvenile sauropods. Extremely large size may have been attained
due to the lack of large carnosaurs in the ecosystem following the extinction of
allosaurids, megalosaurids, and ceratosaurids in the region, allowing eudromaeosaurians
to fill niches normally occupied by other theropods. The arrival of carcharodontosaurs
(Acrocanthosaurus atokensis) in the region corresponded with the extinction of U. ostrommaysorum.
Gigantic Achilles Tendon Hero Achillobator giganticus
Time: 90 Ma ago Location: Dornogovi, Mongolia Habitat: Bayan Shireh Formation.
Probably similar to the later Nemegt Formation, a well-watered but arid near-desert environment
dominated by low scrub, lakes, and dry woodland. Size: WS >1.2m (4ft); BL
~5m (16.5ft); TL unknown Features: Snout very high & squared. Body short & deep, w/
especially long pubis. Wings small but strongly clawed. Legs very short, giving a squat appearance.
Tail very long. Biology: May have used short but strong wings to grapple prey or
buffet rivals. Legs unusually short, w/ the tibia & tarsus each shorter than femur. Probably
slow-moving ambush predators.
Albertan Running Lizard Dromaeosaurus albertensis
Time: 75 Ma Location: Alberta, Canada Habitat: Dinosaur Park Formation. Seasonally
arid lowland plains dominated by braided river systems and small forests. Size: WS >unknown;
BL 1.7m (5.6ft); TL unknown Features: Head box-like in profile, w/ long, square
snout. Legs relatively long compared to contemporary S. explanatus. Tail more flexible
than most other eudromaeosaurians. Biology: Longer legs & stouter jaws & teeth indicate
that these may have been pursuit predators of larger prey than their contemporaries.
Marshall’s Savage Robber Atrociraptor marshalli
Time: 70 Ma Location: Alberta, Canada Habitat: Horseshoe Canyon Formation, seasonally
arid lowland plains w/ braided river systems and small forests. Size: WS unknown; BL
~1.7m (5.6ft); TL unknown Features: Head box-like in profile, with short, rounded snout.
Biology: Probably similar in habits to Dromaeosaurus. Heavy, square skull & robust teeth
indicate that these took relatively large prey.
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