Page:Countershading and Stripes in the Theropod Dinosaur Sinosauropteryx Reveal Heterogeneous Habitats in the Early Cretaceous Jehol Biota.pdf/5

 considering that theropods were most likely tri- or tetra-chromatic, like their extant counterparts the tetrachromatic birds [29, 30] and the trichromatic crocodiles [31], the Mesozoic predator-prey dynamic would likely have been much more visual than extant terrestrial biotas in which dichromatic mammals are highest in the food chain. It is therefore not surprising to observe camouflage patterns in a small Cretaceous theropod.

Although many of the vertebrates of the Jehol Biota were arboreal or scansorial, including a number of other theropods [11], owing to its anatomy Sinosauropteryx was likely restricted to an obligate terrestrial habit and thus did not have the option of retreating to the trees to escape predators. Further, color patterns beneficial as camouflage would have aided Sinosauropteryx in hunting its own prey, which likely also relied, at least in part, on visual cues to detect predators. The hypothesis that its color patterning was predominantly driven by a need to remain cryptic is therefore parsimonious in Sinosauropteryx. Alternative explanations for countershading in modern animals, such as thermoregulation, UV protection, and the costs of producing pigmentation, could also play a role in the color patterns observed in Sinosauropteryx. The relative importance of these possible functions and their interplay in modern animals is, however, poorly understood, and thus would be difficult to explore in an extinct animal. Despite potential limitations in our understanding of countershading function in modern animals, the correlation between habitat and countershading pattern nuances has been quantitively shown in numerous extant taxa and was likely also present in the past.

Habitat Preference

The Jehol Biota includes abundant and diverse floral remains alongside its fauna [11, 32]. High paleotemperatures may have aided the development of lush forested habitats thought to have existed in much of the area [11]. Speculation has been 3340