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）涉及带有变异的传代（descent with modification），是演化生物学的核心概念，但通常难以辨识。本研究针对目前仅见报道的化石侏儒露脊鲸Miocaperea pulchra，与其唯一现生近亲、颇具争议的侏儒露脊鲸Caperea marginata开展了支序分类关系分析，后者的标本涵盖成体与幼体两类个体。基于形态学的系统发育分析结果显示，Miocaperea pulchra的系统发育位置介于Caperea marginata的幼体与成体之间，这提示二者可能存在祖先-后代关系——这是目前须鲸类（鲸目：须鲸亚目，Cetacea: Mysticeti）中已发现的首例此类亲缘关系。Miocaperea pulchra与Caperea marginata所在的演化支可能呈现长期形态停滞现象，进而可为间断平衡（punctuated equilibrium）理论提供佐证。