Ontogeny and evolution of the elasmosaurid neck highlight a greater diversity of Antarctic plesiosaurians

The Antarctic plesiosaurian record is critical for understanding the evolution of elasmosaurids in the southern hemisphere. Elasmosaurids exhibit some of the most remarkable modifications of the vertebrate axial skeleton given their extreme elongation of the cervical region. Despite a considerable amount of information available on vertebral counts within Plesiosauria throughout the decades, we have a considerably more limited understanding of the diversity of cervical vertebral shapes in elasmosaurids and how these have changed throughout ontogeny and phylogeny. Here, we compile the largest known morphometric dataset on elasmosaurid cervical vertebrae, including data on juveniles and adults, to answer some of those long-standing questions. This dataset also includes newly recovered materials from Antarctica, which we describe herein. Using multivariate statistical approaches, we find that the two major elasmosaurid cervical morphotypes, the elasmosaurine anteroposteriorly elongate (can...

南极蛇颈龙目（Plesiosaurian）的化石记录对于理解南半球薄板龙科（Elasmosaurids）的演化至关重要。
薄板龙科动物因其颈部区域的极度延长，展现出脊椎动物轴向骨骼中最为显著的形态特化之一。
尽管数十年来关于蛇颈龙目椎体数量的信息已较为丰富，但我们对薄板龙科颈椎形态的多样性及其在个体发育（ontogeny）和系统发育（phylogeny）过程中的变化仍知之甚少。
在此，我们汇编了目前已知规模最大的薄板龙科颈椎形态测量数据集，涵盖幼体与成体的数据，旨在解答这些长期悬而未决的问题。
该数据集还包含了来自南极的新发现材料，我们将在此对其进行描述。
通过多变量统计方法，我们发现薄板龙科的两种主要颈椎形态型——薄板龙亚科前后向伸长的（can...