科研之友
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摘要
Although frequent in vertebrates (e.g. crocodylians, stem-tetrapods, turtles), the adaptive significance of bone ornamentation, that is the honeycomb-like pattern of pits and ridges that occur on the surface of dermal bones, remains poorly understood. In order to help assess the evolutionary history and ecological correlates of this character, ornamentation was quantified in 69 extant and extinct Pseudosuchia (taxa more closely related to crocodiles than to birds). This variable was related to the dominant habitat (terrestrial, amphibious, pelagic) of these taxa within a phylogenetic framework covering more than 250 Myr of evolution. The phylogenetic analyses reveal a significant correlation between the degree of bone ornamentation on the skull roof with lifestyle (terrestrial, amphibious, pelagic). A straightforward adaptive interpretation of these results is to be avoided because skull morphology has recently been shown to strongly influence local development of bone ornamentation in Crocodylia. Indeed, ornamentation in long-snouted amphibious forms scores low or nil values on the skull roof while scoring very high values on osteoderms. Our results also show that amphibious forms, whether marine or fluvial, have a high degree of ornamentation, whereas terrestrial and pelagic forms are either not ornamented or have a low level of ornamentation. It is hypothesized that the high development of ornamentation among semi-aquatic pseudosuchians has been positively selected because it improves basking efficiency in semi-aquatic ambush (i.e. poorly active) predators. This process would have occurred at the Triassic-Jurassic boundary.
- 出版日期2017-6-1
