Churchill Morgan, Clementz Mark T
Department of Geology and Geophysics, University of Wyoming, Laramie, Wyoming, USA; Program in Ecology, University of Wyoming, Laramie, Wyoming, USA.
Anat Rec (Hoboken). 2015 May;298(5):878-902. doi: 10.1002/ar.23082. Epub 2015 Apr 6.
Pinnipeds (seals, sea lions, and walruses) show variation in tooth morphology that relates to ecology. However, crown size and spacing are two aspects of morphology that have not been quantified in prior studies. We measured these characters for nearly all extant pinnipeds and three fossil taxa and then determined the principal sources of variation in tooth size and spacing using principal components (PCAs) and hierarchical cluster analysis (HCA). PCA and HCA showed that species sorted into three groups: taxa with small crowns and large diastemata, taxa with large crowns and small diastemata, and taxa that fell between these two extremes. We then performed discriminant function analysis (DFA) to determine if tooth morphology correlated with foraging strategy or diet. DFA results indicated weak correlation with diet, and stronger correlation with prey capture strategies. Tooth size and spacing were most strongly correlated with the importance of teeth in prey acquisition, with tooth size decreasing and tooth spacing increasing as teeth become less necessary in capturing food items. Taxa which relied on teeth for filtering prey from the water column or processing larger or tougher food items generally had larger crowns and smaller tooth spacing then taxa which swallowed prey whole. We found the fossil taxa Desmatophoca and Enaliarctos were most similar in tooth morphology to extant otariids, suggesting that both taxa were generalist feeders. This study established the relationship between tooth size and feeding behavior, and provides a new tool to explore the paleoecology of fossil pinnipeds and other aquatic tetrapods.
鳍足类动物（海豹、海狮和海象）的牙齿形态存在与生态相关的差异。然而，冠部大小和间距是形态学的两个方面，在以往的研究中尚未进行量化。我们测量了几乎所有现存鳍足类动物和三个化石类群的这些特征，然后使用主成分分析（PCA）和层次聚类分析（HCA）确定牙齿大小和间距变化的主要来源。PCA和HCA表明，物种分为三组：冠部小且间隙大的类群、冠部大且间隙小的类群，以及介于这两个极端之间的类群。然后，我们进行判别函数分析（DFA）以确定牙齿形态是否与觅食策略或饮食相关。DFA结果表明与饮食的相关性较弱，而与猎物捕获策略的相关性较强。牙齿大小和间距与牙齿在获取猎物中的重要性最密切相关，随着牙齿在捕获食物时变得不那么必要，牙齿大小减小而牙齿间距增大。依靠牙齿从水柱中过滤猎物或处理更大或更硬食物的类群，其冠部通常比整个吞下猎物的类群更大且牙齿间距更小。我们发现化石类群Desmatophoca和Enaliarctos在牙齿形态上与现存的海狮科动物最相似，这表明这两个类群都是广食性动物。这项研究建立了牙齿大小与摄食行为之间的关系，并提供了一种新工具来探索化石鳍足类动物和其他水生四足动物的古生态学。
