Collaborative Research: Phylogeny of the Triassic-Recent Nautilaceae (Cephalopoda)

小行星9614285 鹦鹉螺目头足类包括超过二十个属和数百个命名的物种，跨越近2.3亿年（三叠纪-最近）。 鹦鹉螺类的历史和演化已被人们所熟知，近50年来，鹦鹉螺类的系统学基本上没有变化，但有三个基本原则没有受到挑战：1）鹦鹉螺类在进化上是保守的，自三叠纪末以来形态变化不大;最后演化的成员是现存的鹦鹉螺，演化于更新世或上新世。 然而，在过去的十年中，新的信息表明，一个彻底的重新评估的系统发育的解释和分类的组是在秩序。 现在看来，后侏罗纪鹦鹉螺类物种已大大过度分裂;新的化石发现表明，鹦鹉螺属至少可以追溯到白垩纪中期;最近的调查表明，几个新的字符，将有助于在该集团的分支评估;鹦鹉螺科的初步系统发育分析与过去的解释形成鲜明对比。 我们建议开发一套形态特征，使我们能够进行支序分析的组，以发展的进化关系的理解，并评估的有效性命名的化石类群在我们的理解的变化和物种和属的概念，在现存的类群。 我们将使用共享的衍生字符的存在，开发一个分类系统的组，基于进化关系，而不是形态相似性。 此外，我们建议使用主成分分析（PCA），以便：a）量化和跟踪形态变化和多样性，随着时间的推移，B）确定是否（哪些）特定的壳形态类型是首选和理论和占领的形态空间之间的关系在一个非常长的时间跨度（200我）;以及c）评估这些形态如何响应生物危机，重点关注三叠纪末和白垩纪灭绝事件。 我们的调查结果将直接影响到了解这个特定谱系的进化历史，这是最长的软体动物分支之一，从最近到三叠纪（约2.3亿年）。 结果将有关系的解释宏观进化变化的形态多样性和丰富性，以及形态的生物危机的反应，在近2亿年的规模。

9614285 Saunders Nautilacean cephalopods include more than a score of genera and hundreds of named species spanning almost 230 million years (Triassic-Recent). Their history and phylogeny have been thought to be well understood, and their systematics have remained relatively unchanged for ~50 years, during which three tenets have remained unchallenged: 1) nautilaceans were evolutionarily conservative, showing little morphological change since the end of the Triassic; 2) most genera can be differentiated by only one or two characters; and 3) the last-evolved member is extant Nautilus, having evolved in the Pleistocene or Pliocene. In the last decade, however, new information suggests that a radical re-evaluation of both the phylogenetic interpretation and the classification of the group are in order. It now appears that post-Jurassic nautilacean species have been vastly over-slit; new fossil finds show that the genus Nautilus dates back at least to the middle Cretaceous; recent investigations demonstrate several new characters that will aid in the cladistic evaluation of the group; and preliminary phylogenetic analysis of the Nautilaceae stands in marked contrast to past interpretations. We propose to develop a suite of morphologic characters that will permit us to undertake cladistic analysis of the group, in order to develop understanding of evolutionary relationships, and to assess the validity of named fossil taxa in the light of our understanding of variation and species-and generic concepts in extant taxa. We will use the presence of shared derived characters to develop a classification system of the group, based on evolutionary relationships, rather than morphological similarity. In addition, we propose to use principal components analysis (PCA) in order to: a) quantify and to track morphologic variation and diversity through time; b) determine whether (which) particular shell morphotypes were preferred and the relationship between theoretical and occupied morphospace over an extremely long time span (200 my); and c) assess how these morphologies responded to biotic crisis, focusing on the terminal Triassic- and Cretaceous extinction events. The results of our investigation will bear directly on understanding the evolutionary history of this particular lineage, one of the longest ranging of molluscan clades, extending from the Recent to the Triassic (~230 million years). The results will have bearing on the interpretation of macroevolutionary change in morphologic diversity and richness, and to morphologic responses to biotic crisis, on a scale of nearly 200 million years.