美国洛杉矶县自然历史博物馆恐龙研究所Lars Schmitz研究团队提出“早期巨人”揭示鱼龙体型的进化速度快于鲸类。相关论文发表在2021年12月24日出版的《科学》杂志上。

他们描述了新的巨型鱼龙Cymbospondylus youngorum sp. nov.，其带有来自美国内华达州中三叠纪化石山动物群的2米长的头骨，这表明了尽管缺乏许多现代初级生产者，但其大小也能快速进化。令人惊讶的是，化石山动物群在大小范围方面可与现代海洋哺乳动物群的组成相媲美，而能量通量模型表明，在鱼龙起源后不久，中三叠世海洋食物网能够在高营养水平上支持几种大型鱼龙生存。

据了解，海洋羊膜动物的体型跨越六个数量级，但支配这种多样性进化的因素在很大程度上是未知的。现代海洋的高初级生产力被认为是鲸类巨兽出现的先决条件，但这种情况无法解释三叠纪鱼龙的巨大体形。

附：英文原文

Title: Early giant reveals faster evolution of large body size in ichthyosaurs than in cetaceans

Author: P. Martin Sander, Eva Maria Griebeler, Nicole Klein, Jorge Velez Juarbe, Tanja Wintrich, Liam J. Revell, Lars Schmitz

Issue&Volume: 2021-12-24

Abstract: Body sizes of marine amniotes span six orders of magnitude, yet the factors that governed the evolution of this diversity are largely unknown. High primary production of modern oceans is considered a prerequisite for the emergence of cetacean giants, but that condition cannot explain gigantism in Triassic ichthyosaurs. We describe the new giant ichthyosaur Cymbospondylus youngorum sp. nov. with a 2-meter-long skull from the Middle Triassic Fossil Hill Fauna of Nevada, USA, underscoring rapid size evolution despite the absence of many modern primary producers. Surprisingly, the Fossil Hill Fauna rivaled the composition of modern marine mammal faunas in terms of size range, and energy-flux models suggest that Middle Triassic marine food webs were able to support several large-bodied ichthyosaurs at high trophic levels, shortly after ichthyosaur origins.

DOI: abf5787

Source: https://www.science.org/doi/10.1126/science.abf5787