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5 January 2023 Observation of Claw Use and Feeding Behavior of the Red-Legged Seriema and Its Implication for Claw Use in Deinonychosaurs
Taylor Oswald, Brian Curtice, Mikayla Bolander, Cristy Lopez
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The red-legged seriema (Cariama cristata) is unique among extant birds in that they possess prominent recurved sickle claws on the second pedal digits which are held off the ground, outwardly similar to the claws of the extinct deinonychosaurs and basal avialans, and probably convergently evolved due to similar lifestyle/feeding habits. Thus, the way in which seriemas use their claws has the potential to shine additional light on how deinonychosaurs used theirs. Though formerly thought of as slashing weapons, it has also been hypothesized that deinonychosaurs used their claws to pin and grasp rather than slash. This newer hypothesis has been called the Raptor Prey Restraint (RPR) hypothesis. Our observations of claw use in simulated and real feeding behavior of red-legged seriemas at the Wildlife World Zoo, Aquarium, and Safari Park in Phoenix, AZ, and the Tracy Aviary and Botanical Gardens in Salt Lake City, UT, are consistent with the RPR hypothesis. The seriemas were observed using their feet, with special preference given to digit II, to pin objects/prey, which were torn at in tandem with the beak. Given the high degree of similarity between the claws of seriemas and the claws of deinonychosaurs, as well as their shared paravian ancestry and similar predatory cursorial lifestyles, it is likely that seriemas are among the best extant proxies for deinonychosaur claw use. That they use their claws in a manner so consistent with hypothesized deinonychosaur claw use is further evidence that the RPR hypothesis is most likely the best hypothesis for the function of the digit II “killing claws” of deinonychosaurs.

Taylor Oswald, Brian Curtice, Mikayla Bolander, and Cristy Lopez "Observation of Claw Use and Feeding Behavior of the Red-Legged Seriema and Its Implication for Claw Use in Deinonychosaurs," Journal of the Arizona-Nevada Academy of Science 50(1), 17-21, (5 January 2023).
Published: 5 January 2023
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