Cenozoic megatooth sharks occupied extremely high trophic positions.
新生代巨齿鲨类占据极高营养级

Authors / 作者: Kast ER, Griffiths ML, Kim SL, Rao ZC, Shimada K, Becker MA, Maisch HM, Eagle RA, Clarke CA, Neumann AN, Karnes ME, Lüdecke T, Leichliter JN, Martínez-García A, Akhtar AA, Wang XT, Haug GH, Sigman DM.
Journal / 期刊: Science advances
Year / 年份: 2022
DOI: 10.1126/sciadv.abl6529
Publisher / 出版社: https://www.science.org/doi/10.1126/sciadv.abl6529
Abstract source / 摘要来源: https://europepmc.org/article/MED/35731884

Author abstract / 作者原文摘要
Trophic position is a fundamental characteristic of animals, yet it is unknown in many extinct species. In this study, we ground-truth the 15N/14N ratio of enameloid-bound organic matter (δ15NEB) as a trophic level proxy by comparison to dentin collagen δ15N 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 δ15NEB 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. δ15NEB 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.

Summary basis / 解读依据
摘要解读依据已查看的索引作者摘要；如已保存全文，可用于进一步阅读。
Summary based on the inspected indexed author abstract; archived full text, when available, is provided for further reading.

Key findings / 主要发现
研究校准牙釉样质结合有机质中的氮同位素作为营养级指标，并应用于耳齿鲨属化石。巨齿鲨极高的同位素值指示其营养位置高于已知海洋比较对象；该谱系的最高营养位置似乎早于最大体型出现。
The study calibrated tooth-enameloid-bound nitrogen isotopes as a trophic proxy and applied them to fossil Otodus sharks. Very high megalodon values indicate a trophic position above known marine comparators, and the lineage's highest trophic position apparently preceded its maximum body size.

Conclusions / 结论
巨齿鲨谱系经历显著食性转变并达到异常高的营养位置；同位素证据可补充单凭体型作出的推断，帮助重建灭绝动物食物网。
Megatooth sharks underwent major dietary shifts and reached exceptional trophic positions. The isotope results offer a way to reconstruct extinct food webs beyond estimates based only on body size.

Relevance / 关联说明
直接研究清单物种，或研究广义类群中的代表物种。
Direct research on the listed species or a representative of the broadly named group.