分类： 生物学 >> 人类学 提交时间： 2024-03-06
摘要： The inference of Mesozoic avialan bird diets previously relied on traditional methods such as morphological comparisons among taxa and direct evidence such as identifiable stomach contents. However, the application of these approaches has been limited because of uncommon preservation of relevant fossil evidence. We searched for additional informative characteristics to help develop new methods to assess the diet of fossil birds. In particular, the morphology of the avialan neck is highly modularized and plays roles in multiple functions including food acquisition. The structure of and variation among the cervical vertebrae likely reflects the demands of feeding ecology in fossil and extant birds because the avialan neck evolved to, at least in part, replace the forelimbs by assisting with activities such as cranioinertial feeding and other ecological functions. Here, we utilize morphometric and statistical analyses to establish an initial quantitative relationship between cervical morphology and dietary modes in both extant and extinct birds. This morphometric framework derived from the cervical morphology of living birds is used as a basis to estimate the diet categories of five taxa of Mesozoic birds. The results indicate that there is a quantitative correlation between cervical morphology differentiation and their interrelated feeding modes. The enantiornithine taxa examined exhibit cervical morphologies similar to extant insectivorous or carnivorous birds. The ornithurine species show cervical morphologies that are more aligned with generalist or herbivorous birds, and exhibit preliminary morphological features tied to aquatic adaptions. These findings are consistent in part with other direct fossil evidence, as well as hypotheses developed from other skeletal comparisons. Therefore, the cervical vertebral series, as a skeletal system closely linked to food acquisition, can serve as one of the valuable metrics to provide information for inferring the diet of long extinct Mesozoic birds.
分类： 生物学 >> 动物学 提交时间： 2017-11-07 合作期刊: 《古脊椎动物学报》
摘要： A new fossil specimen from the early Middle Eocene of an Irdin Manha Formation equivalent (Erden Obo Section) in Nei Mongol (Inner Mongolia), China appears to be derived from an ameghinornithid-like species, and may represent the first record of the Ameghinornithidae in Asia. This new specimen exhibits the subcircular lateral condyle outline, the absence of an ossified supratendinal bridge, an enlarged flattened tubercle lateral to the extensor sulcus, and other features shared among known ameghinornithid and ameghinornithid-like birds. The Nei Mongol fossil is roughly contemporaneous with the oldest records of the ameghinornithids from Europe (~48 Ma). The absence of this group of birds from North America, and their occurrence in Europe and Asia during the Eocene contrasts with the contemporaneous Nei Mongol mammalian fauna that is comprised largely of Asian taxa with a few distinct linkages to North America. Along with the record of an ameghinornithid-like bird from the early Oligocene deposits of the Fayum area in Egypt, it seems that this extinct bird group had a much larger geographic distribution than previously recognized.
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