Citipati vs Therizinosaurus
Meandering rivers and low wet areas are interspersed through thick vegetation and patches of forest. It is the late Cretaceous in what would be north central Alberta, and the Wapiti Formation is being deposited in layers of sand and silt (Fanti and Catuneanu 2010). Vegetation grows prolifically during the long northern summers, and many dinosaurs and other animals use this time to put on weight and get into breeding condition. Abundant insects like mayflies (Bell et al. 2013) provide food for the smaller vertebrates in the ecosystem as well, supporting a thriving community.
Into this busy environment, Therizinosaurus wanders, slowly moving across the landscape, following his nose to fresh vegative growth (Lautenschlager et al. 2012). The plants are all putting out a flush of green, preparing to take advantage of long hours of daylight. Herbivores like Therizinosaurus go into high consumption mode, and like some modern animals, may have been able to temporarily disable their sense of being full, allowing them to pack on the pounds. Behavioural adaptations also allow Therizinosaurus to maximize food acquisition using the specialized set of cutlery sprouting from his hands, pulling down top branches full of tender leaves.
Meanwhile, nestled into a shady hollow under some trees, Citipati is feeling content. She recently finished building a nest out of dry fern fronds and other vegetation, and has just laid her first pair of eggs into the shallow bowl (Yang et al. 2019). She has been feeding well lately on small vertebrates, fallen fruits, insects, and carrion. She will continue to lay eggs in pairs, until there are multiple layers arranged in a rising spiral.
Her feathers combined with her brooding behaviour provide an excellent environment for the development of her eggs. She sits calmly, listening to the various sounds of the forest around her. She can hear small birds chattering above her somewhere, and something large thumping and crashing down near the edge of the tree line.
Therizinosaurus is plowing along through the trees, cracking branches as he yanks them down with his powerful forearms and claws. His narrow head can then precisely crop the best leaves using his sharp beak, swallowing and transferring them down his long neck to the large processing center that is his stomach. Unknowingly, he is moving closer and closer to the area where Citipati has laid her nest. She hears the thump of his heavy footfall getting closer and closer, and starts to become nervous. Finally, she can see the trees moving, and stands up to get a better look.
Something very large is coming her way. She hesitates briefly, then begins to fluff up her feathers, flipping her tail fan over her back, and vocalizing as loud as she can. Therizinosaurus barely even notices however, and continues to rip down branches for his meal. He steps up to the next tree and reaches up. His large foot has landed squarely on the next of Citipati, squashing the whole thing flat. Citipati had already moved aside when the lumbering giant showed no reaction to her display. She has lost another nest. With nothing left to keep her in the area, she heads out to search for a less busy part of the forest to start over again with a new nest.
Bell, P. R., Fanti, F., Acorn, J., & Sissons, R. S. (2013). Fossil mayfly larvae (Ephemeroptera, cf. Heptageniidae) from the Late Cretaceous Wapiti Formation, Alberta, Canada. Journal of Paleontology, 87(1), 147-150.
Fanti, Federico, and Octavian Catuneanu. “Fluvial sequence stratigraphy: the Wapiti Formation, west-central Alberta, Canada.” Journal of Sedimentary Research 80.4 (2010): 320-338.
Lautenschlager, S.; Emily, J. R.; Perle, A.; Lindsay, E. Z.; Lawrence, M. W. (2012). “The Endocranial Anatomy of Therizinosauria and Its Implications for Sensory and Cognitive Function”. PLOS ONE. 7 (12): e52289.
Yang, T. R., Wiemann, J., Xu, L., Cheng, Y. N., Wu, X. C., & Sander, P. M. (2019). Reconstruction of oviraptorid clutches illuminates their unique nesting biology. Acta Palaeontologica Polonica, 64(3).