Trophic position is a fundamental characteristic of animals, yet it is unknown in many extinct species. In this study, we ground-truth the 15 N/ 14 N ratio of enameloid-bound organic matter (δ 15 N EB ) as a trophic level proxy by comparison to dentin collagen δ 15 N and apply this method to the fossil record to reconstruct the trophic level of the megatooth sharks (genus Otodus ). These sharks evolved in the Cenozoic, culminating in Otodus megalodon , a shark with a maximum body size of more than 15 m, which went extinct 3.5 million years ago. Very high δ 15 N EB values (22.9 ± 4.4‰) of O. megalodon from the Miocene and Pliocene show that it occupied a higher trophic level than is known for any marine species, extinct or extant. δ 15 N EB also indicates a dietary shift in sharks of the megatooth lineage as they evolved toward the gigantic O. megalodon , with the highest trophic level apparently reached earlier than peak size.

中文翻译：

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新生代巨齿鲨占据了极高的营养位置

营养位置是动物的基本特征，但在许多已灭绝的物种中却是未知的。在这项研究中，我们将真实的15否/14牙釉质结合有机物的 N 比值 (δ15ñEB) 作为与牙本质胶原 δ 比较的营养级代表15N 并将此方法应用于化石记录以重建巨齿鲨（属耳蜗）。这些鲨鱼在新生代进化，最终形成巨齿鲨，一种最大体型超过 15 m 的鲨鱼，于 350 万年前灭绝。非常高的δ15ñEB值（22.9±4.4‰）的巨齿鲨来自中新世和上新世的研究表明，它占据了比已知的任何海洋物种更高的营养水平，无论是灭绝的还是现存的。δ15ñEB也表明巨齿鲨的饮食转变，因为它们向巨大的进化巨齿鲨, 最高营养级显然早于峰值大小。