Data from: Ancestor-descendant relationships in evolution: origin of the extant pygmy right whale, Caperea marginata

Ancestor–descendant relationships (ADRs), involving descent with modification, are the fundamental concept in evolution, but are usually difficult to recognize. We examined the cladistic relationship between the only reported fossil pygmy right whale, Miocaperea pulchra, and its sole living relative, the enigmatic pygmy right whale Caperea marginata, the latter represented by both adult and juvenile specimens. Miocaperea is phylogenetically bracketed between juvenile and adult Caperea marginata in morphologically based analyses, thus suggesting a possible ADR—the first so far identified within baleen whales (Cetacea: Mysticeti). The Miocaperea–Caperea lineage may show long-term morphological stasis and, in turn, punctuated equilibrium.

祖先-后代关系（Ancestor–descendant relationships, ADRs）涉及带有变异的传衍（descent with modification），是演化生物学的核心概念，但通常难以辨识。我们针对目前仅报道的化石小露脊鲸（pygmy right whale）——美丽拟小露脊鲸（Miocaperea pulchra），与其唯一现生类群、颇具神秘争议的小露脊鲸（Caperea marginata）之间的支序分类学关系展开了研究，后者涵盖成年与幼体两类标本。基于形态学的系统发育分析显示，美丽拟小露脊鲸在系统发育上被置于小露脊鲸幼体与成体之间，由此提示了一种潜在的祖先-后代关系——这是目前在须鲸（Cetacea: Mysticeti）中发现的首例此类演化关系。美丽拟小露脊鲸与小露脊鲸所属的支系可能呈现长期的形态停滞，进而体现出间断平衡（punctuated equilibrium）的演化特征。