Strange as it may sound, chickens are the closest living relatives to the famed T. rex. In spite of the large amount of attention the T. rex gets in Hollywood movies, scientists actually know very little about this fearsome dinosaur.
To get a better idea about how dinosaurs like the T. rex walked, a team of researchers from the Universidad de Chile conducted a study involving chickens with prosthetic tails. To simulate how a bipedal dinosaur would have walked, the researchers chose to attach prosthetic tails to a number of chicks. The scientists raised the chickens from chicks to adults to gather data on how growing up with the prosthetic tails affected the chickens' gait and physiology.
"Birds still share many traits with their dinosaur ancestors, making them the best living group to reconstruct certain aspects of non-avian theropod biology," said the researchers in the paper they published at the online journal PLOS ONE. "Bipedal, digitigrade locomotion and parasagittal hindlimb movement are some of those inherited traits."
To gather data for the study, the researchers formed three groups of chickens. The fist group were raised with wooden prosthetic tails. The tails were attached using modeling clay. To account for the chicken's growth, the researchers changed their tails every five days. For the second group, the researchers attached lead weights to the backs of the chickens to serve are the "control-weight" group. The last group of chickens was the control group and they were raised normally without any prosthetic tails or weights.
"Chickens raised wearing artificial tails, and consequently with more posteriorly located centre of mass, showed a more vertical orientation of the femur during standing and increased femoral displacement during locomotion," said the researchers.
A normal chicken walks on two legs using power derived primarily from the knees. For the chickens who grew up with prosthetic tails attached to their posteriors however, the research team discovered a shift to a more "hip-driven locomotion." This type of locomotion can be seen in some mammals, crocodilians and more importantly, dinosaurs.
"Our results support the hypothesis that gradual changes in the location of the centre of mass resulted in more crouched hindlimb postures and a shift from hip-driven to knee-driven limb movements through theropod evolution," said the team. "This study suggests that, through careful experimental manipulations during the growth phase of ontogeny, extant birds can potentially be used to gain important insights into previously unexplored aspects of bipedal non-avian theropod locomotion."
