Monday, May 24, 2010

* Dinosaur legs are not similar

Notice that in almost every respect, dinosaur legs are different than modern bird legs.
"The change in musculature has been accompanied by equally significant changes to the bird’s [dinosaur's] leg. Dinosaurs have {1}two-unit limbs in the sense that {2} two long bones of roughly equal length form the leg above the foot. The weight of the body is borne by the toes and the {3} independent metatarsals of the foot are {4}relatively short.
A similar kind of leg appears in Archaeopteryx and Confuciusornis but in more advanced [modern] birds, {1}the femur is shorter than the tibia and {2}fused metatarsals form a new segment that is similar in length to the tibia. {3}Both the tibia and the metatarsals are fused with neighbouring bones from the joints and been renamed tibiotarsus and tarsometatarsus to reflect their new structure. In the bird’s {4}three-unit leg, the femur is held in a roughly horizontal position so that it functions more like a forward extension of the hip bones and contributes little to the length of the bird’s stride. The new arrangement is very useful when the after part of the abdomen is swollen by the presence of a very large egg. (see gallery of eggs and hips)."

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