Pattern and process of serrations and denticles of reptilian teeth

锯齿的大小和形状经常被用来作为兽脚亚目恐龙的诊断特征。对这些性状种内变异的研究很少。这主要是因为没有一种合适的方法来描述这些变化，并对它们进行统计检验。本研究旨在建立种内变异的数字图像数据库，并探索一种合适的形态测量方法。选取现存爬行动物Varanus和Iguana两种，以及已灭绝爬行动物Velociraptor一种，测量齿冠的基本长度、宽度、高度和锯齿或小齿的基本长度。选择瓦拉努斯恐龙是因为它被认为是兽脚亚目恐龙的最佳相似物之一。对鬣蜥进行了测量，并将其齿齿与瓦拉努斯的锯齿进行了比较。迅猛龙是一种节肢恐龙，之所以被测量是因为它的锯齿有派生特征。在所有三种的四次测量中，锯齿/齿尖的变化最大。使用中的功能牙齿与同一牙位的替代牙齿在锯齿/小齿基长上存在差异。迅猛龙标本没有显示出衍生的特征状态。这些发现强烈建议人们在使用锯齿和/或牙齿上的字符时应该谨慎。几种形态计量学分析试图描述牙齿特征的变化。由于在锯齿/小齿中观察到的高度变化，形态计量学方法被证明不适合描述。

Size and shape of the serrations are often used as a diagnostic character in the theropod dinosaurs. There are very few studies of intraspecific variations of these characters. It is largely because there is not an appropriate method to describe the variations and to test them statistically. This study was to create digital image database for intraspecific variations and it was also to explore a suitable morphometric method. Two species of extant reptiles, Varanus and Iguana, and one species of an extinct reptile, Velociraptor, were chosen to measure tooth crown basal length, width, height, and serration or denticle basal length. Varanus was chosen because it is considered as one of the best analogues for theropod dinosaurs. Iguana was measured to made a comparison of its denticles to the serrations of Varanus. Velociraptor, a thropod dinosaur, was measured because it has a derived character in the serrations. Variations of serrations/denticles were the greatest among the four measurements taken in all the three species. A functional tooth in use shows differences in serration/denticle basal length from a replacement tooth in the same tooth position. The Velociraptor specimen did not show a derived character state. These findings strongly suggest that one should exercise caution on the use of characters on serrations and/or denticles. Several morphometric analyses were attempted to describe variations in dental characters. Due to high variations observed in serrations/denticles, morphometric methods turned out to be not suitable for the description.