Stem-Bird Files: Wading Chimera

Coelurosauria>Tyrannoraptora>Maniraptoriformes>Ornithomimosauria>Deinocheiridae>Deinocheirus>D.mirificus
Time: Early Maastrichtian (71-69 million years ago)
Length: 10-10.6 meters (32.8-34.7ft{MCP-D 100/127 and the holotype, respectively}). Maximum length est. 11.3 meters (37.0ft).
Height: 4.1-4.5 meters (13.4-14.7ft) at the top of the hump (MCP-D 100/127 respectively). Maximum height est. 4.8 meters (15.7ft).
Weight: 6.48-7.5t (5.8-6.8 long tons) based on related Garudimimus. Maximum weight est. ~8.1t (7.3 long tons).
Habitat: Nemegt Formation of Mongolia, Asia.
Ecology: Large terrestrial megaomnivore. Deinocheirus has a beak resembling those of ducks, which, combined with a smaller bite force than expected for an ornithomimid of this size and the environment it lived in, allowed it to crop soft water plants or browse near the ground like some hadrosaurs. A large tongue suggests that it was also a suction feeder, absorbing small prey from the bottom of freshwater bodies (gut contents of the animal support this hypothesis).
Diet: Multiple types of aquatic/wet-ground foliage, low-growing dry ground foliage (both angiosperms and gymnosperms) and fish of unknown size. It may occasionally have also eaten the waterfowl Teviornis and juvenile non-avian dinosaurs, but this is pure speculation.
Locomotion: Despite being an ornithomimosaur, a clade which includes some of the fastest extinct dinosaurs, the massive size and much bulkier form than its relatives means that Deinocheirus was not a fast runner. It likely had a similar or inferior running speed to that of large tyrannosaurs or hadrosaurs.
Potential predators: Hatchlings would be vulnerable to many small theropods, including Adasaurus, Borogovia, Tochisaurus and Zanabazar. Juveniles were likely prey for small tyrannosaurids Alioramus and Raptorex (which may or may not be a juvenile of another species), while adults had only to fear the massive tyrannosaurine Tarbosaurus (Tyrannosaurus baatar?).
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And here's your ultraduck. Only turns out very slightly smaller than I expected. The weight is my first attempt at creating original estimates for an animal's size (it is scaled up from Garudimimus based on body length, with an added 50% of mass because of the much bulkier body and high vertebrae that most likely supported a bison-like hump). You may notice that the Stem-Bird files are becoming more saurischian-centric, but c'mon... they're called STEM-BIRD files for Godzilla's sake, it's mostly gonna feature the suborder that actually includes birds.

I do not take credit for the skeletal references or silhouettes of any of these animals (I only fill them out with the life reconstruction and complement it with the info sheets).