近日，美国纽约自然博物馆无脊椎动物部的 Amane Tajika小组探讨了菊石的灭绝与鹦鹉螺的生存的原因。相关论文发表在2023年4月25日出版的《地质学》杂志上。

研究人员调查了这两组之间代谢率的差异，以进一步探索选择性灭绝的原因。研究使用一种新的代谢替代物——壳材料的稳定碳同位素比率(C_meta)中的代谢碳比率——来确定代谢率。使用这种方法，研究人员记录了现代头足类的显著差异。研究结果与基于耗氧量的估计相一致，表明这一指标是代谢率的可靠指标。研究人员使用这种方法确定生活在白垩纪(马斯特里赫特)末期菊石和鹦鹉螺目的代谢率。

研究结果表明，在白垩纪-古近纪大灭绝事件中幸存下来的鹦鹉螺目Eutrephoceras的代谢率低于共生的菊石。研究结论为，在希克苏鲁伯小行星撞击后的环境恶化时期(地表水酸化和导致浮游生物减少)，鹦鹉螺目动物的低代谢率是一个优势。

据悉，理解选择性灭绝的机制，对于预测人类活动引起的环境变化对当前生态系统的影响来说非常重要。白垩纪-古近纪大灭绝事件中有壳头足类动物的选择性灭绝经常被研究，但其机制仍有争议。

附：英文原文

Title: Ammonoid extinction versus nautiloid survival: Is metabolism responsible

Author: Amane Tajika, Neil H. Landman, J. Kirk Cochran, Kozue Nishida, Kotaro Shirai, Toyoho Ishimura, Naoko Murakami-Sugihara, Kei Sato

Issue&Volume: 2023-04-25

Abstract: Understanding the mechanism of selective extinction is important in predicting the impact of anthropogenic environmental changes on current ecosystems. The selective extinction of externally shelled cephalopods at the Cretaceous-Paleogene (K-Pg) mass extinction event (am-monoids versus nautiloids) is often studied, but its mechanism is still debated. We investigate the differences in metabolic rate between these two groups to further explore the causes of selective extinction. We use a novel metabolic proxy—the fraction of metabolic carbon in the stable carbon isotope ratio of shell material (Cmeta)—to determine metabolic rate. Using this approach, we document significant differences in C_meta among modern cephalopod taxa (Nautilus spp., Argonauta argo, Dosidicus gigas, Sepia officinalis, and Spirula spirula). Our results are consistent with estimates based on oxygen consumption, suggesting that this proxy is a reliable indicator of metabolic rate. We then use this approach to determine the metabolic rates of ammonoids and nautiloids that lived at the end of the Cretaceous (Maastrichtian). Our results show that the nautiloid Eutrephoceras, which survived the K-Pg mass extinction event, possessed a lower metabolic rate than co-occurring ammonoids (Baculites, Eubaculites, Discoscaphites, and Hoploscaphites). We conclude that the lower metabolic rate in nautiloids was an advantage during a time of environmental deterioration (surface-water acidification and resulting decrease in plankton) following the Chicxulub asteroid impact.

DOI: 10.1130/G51116.1

Source: https://pubs.geoscienceworld.org/gsa/geology/article/doi/10.1130/G51116.1/623007/Ammonoid-extinction-versus-nautiloid-survival-Is