Researchers have found evidence for evolutionary shifts in the rules that govern the relationship between color and the shape of pigment-containing organelles known as melanosomes.
The research revises the rules allowing scientists to decipher color in dinosaurs may also provide a tool for understanding the evolutionary emergence of flight and changes in dinosaur physiology prior to its origin.
At the same time, a research team from The University of Texas at Austin, the University of Akron, the China University of Geosciences and four other Chinese institutions, unexpectedly discovered that ancient maniraptoran dinosaurs, paravians, and living mammals and birds uniquely shared the evolutionary development of diverse melanosome shapes and sizes. (Diversity in the shape and size of melanosomes allows scientists to decipher color.)
The evolution of diverse melanosomes in these organisms raises the possibility that melanosome shape and size could yield insights into dinosaur physiology.
Melanosomes contain melanin, the most common light-absorbing pigment found in animals
According to the new research, color-decoding works well for some species, but the color of others may be trickier than thought to reconstruct.
Comparing melanosomes of 181 extant specimens, 13 fossil specimens and all previously published data on melanosome diversity, the researchers found that living turtles, lizards and crocodiles, which are ectothermic (commonly known as cold-blooded), show much less diversity in the shape of melanosomes than birds and mammals, which are endothermic (warm-blooded, with higher metabolic rates).
In the dinosaur lineage leading to birds, the researchers found an explosion in the diversity of melanosome shape and size that appears to correlate to an explosion of color within these groups. The shift in diversity took place abruptly, near the origin of pinnate feathers in maniraptoran dinosaurs.
The study has been published in the journal Nature.
