Abstract
The small-sized sauropterygianKeichousaurus huiwas one of the most abundant marine reptiles from the Triassic Yangtze Sea in South China. AlthoughKeichousaurushas been studied in many aspects, including the osteology, ontogeny, sexual dimorphism, and reproduction, the dentition of this marine reptile was only briefly described in external morphology. In this study, we provide new information onKeichousaurustooth implantation, histology, and replacement based on a detailed examination of well-preserved specimens collected in the past decades. The tooth histology has been investigated for the first time by analyzing cross-sections of premaxillary teeth and the tooth attachment and implantation have been further revealed by X-ray computed microtomography. We refer the tooth replacement ofKeichousaurusto the iguanid replacement type on the basis of the observed invasion of small replacement tooth into the pulp cavity of the functional tooth. Given the resemblance to other extinct and modern piscivorous predators in the morphology and structure of teeth,Keichousaurusmight mainly feed on small or juvenile fishes and some relatively soft-bodied invertebrates (e.g., mysidacean shrimps) from the same ecosystem.
Highlights
Teeth are complex mineralized tissues that originated in jawed vertebrates more than 400 million years ago (Rücklin et al, 2012)
Represented by large quantities of well-preserved specimens, Keichousaurus has been studied in many aspects including the ontogeny, taphonomy, reproduction, sexual dimorphism, allometry, and living style (Lin and Rieppel, 1998; Cheng et al, 2004, 2009; Holmes et al, 2008; Fu et al, 2013; Xue et al, 2013; Motani et al, 2015)
Through a detailed examination of wellpreserved specimens, we aim to describe the tooth morphology, internal structure, and tooth histology of Keichousaurus and to discuss the tooth replacement, dental function, and food preference of this taxon
Summary
Teeth are complex mineralized tissues that originated in jawed vertebrates more than 400 million years ago (Rücklin et al, 2012). The teeth of Keichousaurus— significant organs for taxonomy and ethology (Radinsky, 1961; Handrigan and Richman, 2011; Hwang, 2011)—were only briefly described in their external morphology (Young, 1958, 1965; Lin and Rieppel, 1998; Jiang, 2002; Holmes et al, 2008; Fu et al, 2013) Compared with those in other marine reptiles (Maisch and Matzke, 1997; Motani, 1997; Rieppel, 2001; Ciampaglio et al, 2005; Caldwell, 2007; Maxwell et al, 2012; Neenan et al, 2014; Sassoon et al, 2015), the teeth of Keichousaurus remain poorly known in their internal structure, function, and replacement
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