Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, University Avenue, Glasgow, UK.
Anat Rec (Hoboken). 2012 Jul;295(7):1147-58. doi: 10.1002/ar.22491. Epub 2012 May 11.
Metriorhynchidae was a peculiar but long-lived group of marine Mesozoic crocodylomorphs adapted to a pelagic lifestyle. Recent discoveries show that metriorhynchids evolved a wide range of craniodental morphotypes and inferred feeding strategies. One genus, Dakosaurus, is arguably the most aberrant marine crocodylomorph due to its large, robust, ziphodont teeth; very low tooth count; and brevirostrine/oreinirostral snout. We here report an additional unusual feature of Dakosaurus that is unique among marine crocodylomorphs: tightly fitting tooth-to-tooth occlusion, whose inference is supported by reception pits along the upper and lower tooth rows, indicative of vertically orientated crowns that were in close contact during occlusion, and three distinct types of dental wear. These include irregular spalled surfaces near the apex (probably caused by tooth-food contact), semi-circular wear near the base, and elongate surfaces extending along the mesial and distal margins of the teeth, obliterating the carinae (including the denticles). Scanning electron micrographs show that these latter surfaces are marked by parallel apicobasal striations, which in extant mammals reflect tooth-tooth contact. As such, we interpret the carinal wear facets in Dakosaurus as being formed by repeated tooth-tooth contact between the mesial and distal margins of the teeth of the upper and lower jaw. We posit that this increased the available shearing surface on their high crowns. Together, these wear patterns suggest that occlusion in Dakosaurus was specialized for cutting large and abrasive prey items into portions small enough to swallow, making it a prime example of an aquatic reptile with macrophagous feeding habits.
长吻鳄科是一类奇特但长寿的中生代海洋鳄形目爬行动物，适应远洋生活。最近的发现表明，长吻鳄科进化出了广泛的颅齿形态和推断的摄食策略。一个属，达科龙，由于其大而粗壮的栉齿状牙齿、极低的牙齿数量和短吻/短吻口鼻部，被认为是最异常的海洋鳄形目爬行动物。我们在这里报告达科龙的一个额外的不寻常特征，这在海洋鳄形目爬行动物中是独一无二的：牙齿之间紧密贴合的咬合，这一推断得到了上颌和下颌齿列上的接收凹坑的支持，表明垂直定向的冠部在咬合时紧密接触，以及三种不同类型的牙齿磨损。这些包括在牙尖附近出现不规则剥落表面（可能是由牙齿与食物接触引起的）、基部附近的半圆形磨损以及沿牙齿的近中和远中边缘延伸的长形表面，从而消除了齿嵴（包括小齿）。扫描电子显微镜显示，这些后一种表面具有平行的顶底纹，在现生哺乳动物中反映了牙齿之间的接触。因此，我们将达科龙的齿嵴磨损面解释为上颌和下颌牙齿的近中和远中边缘之间反复接触形成的。我们假设这增加了高冠牙齿的可用剪切表面。这些磨损模式表明，达科龙的咬合专门用于将大而粗糙的猎物切成足够小的碎片以便吞咽，使其成为具有食腐习性的水生爬行动物的典型代表。
