Origin of birds mitochondrial uncoupling protein, UCP1, which is thermogenic. In mammals, UCP1 functions within brown adipose tissue to protect newborns against hypothermia. In modern birds, skeletal muscle serves a similar function and is presumed to have done so in their ancestors. In this view, bipedality and other avian skeletal alterations were side effects of muscle hyperplasia, with further evolutionary modifications of the forelimbs, including adaptations for flight or swimming, and vestigiality, being secondary consequences of two-leggedness. "Archaeopteryx" has historically been considered the first bird, or "Urvogel". Although newer fossil discoveries filled the gap between theropods and "Archaeopteryx", as well as the gap
Specimens of Archaeopteryx Pohl, who was able to find an anonymous donor willing to offer up the funds. After an initial period of display and scientific study in Germany, the specimen would then be given to the WDC on a long-term loan. After a period of research (Mayr et al. 2005, 2007), the fossil was transferred to the Wyoming Dinosaur Center of Thermopolis, Wyoming, where it has remained since June 2007. The export out of Germany of this specimen—widely considered to be one of the best "Archaeopteryx" fossils known—has caused some concern among German paleontologists and the public. Though no formal legality was