A Lower to Middle Jurassic Terrestrial Vertebrate Assemblageand its Implications for the Post-Triassic Radiation of Tetrapods

PI将研究三叠纪末期大灭绝后陆生四足动物多样化的特殊下侏罗世或中侏罗世脊椎动物组合的意义。来自墨西哥塔毛利帕斯州Huizachal峡谷La Boca组的脊椎动物组合提供了一个独特的测试，即快速适应性辐射是否发生在三叠纪后的全球脊椎动物动物群中，通常被推断为大规模灭绝之后。初步研究表明：a)根据脊椎动物生物地层学，该组合（包括新分类群）的年龄模糊为下侏罗统或中侏罗统；b)在独特的沉积条件下，在复杂的构造背景下形成的组合，阻碍了简单的岩石地层对比。为了将Huizachal组合整合到三叠纪后四足动物多样化的重建中，PI将a)研究该组合的系统古生物学，包括系统发育特征；b)建立惠萨恰尔峡谷岩石地层学，重建沉积环境；c)通过脊椎动物生物地层学以外的方法来限制惠扎查尔组合的年龄。在完成了这些先决条件之后，他们将把结果整合到基于系统发育的三叠纪后陆生生物多样性汇编中，以检验早侏罗世以陆生脊椎动物的快速辐射为特征的观点。

PI will study the implications of an exceptional Lower or Middle Jurassic vertebrate assemblage for the diversification of terrestrial tetrapods following the mass extinction(s) at the end of the Triassic. The vertebrate assemblage, from the La Boca Formation, Huizachal Canyon, Tamaulipas, Mexico, affords a unique test of whether rapid adaptive radiation, commonly inferred to follow mass extinctions, occurred in post-Triassic global vertebrate faunas. Preliminary work indicates that: a)based upon vertebrate biostratigraphy, the age of the assemblage (which includes new taxa) is ambiguously Lower or Middle Jurassic; and b)the assemblage accumulated under unique depositional conditions, in a structurally complex setting that hinders simple lithostratigraphic correlations. To integrate the Huizachal assemblage into a reconstruction of post-Triassic tetrapod diversification, PI will a)study the systematic paleontology of the assemblage, including a phylogenetic characterization; b)establish a lithostratigraphy for Huizachal Canyon involving the reconstruction of sedimentary environments; and c)constrain the age of the Huizachal assemblage by means other than vertebrate biostratigraphy. Having accomplished these prerequisites, they will integrate results into phylogenetically-based compilations of post-Triassic terrestrial diversity, to test the idea that the early Jurassic was characterized by a rapid radiation of terrestrial vertebrates.