Laboratório de Palinofácies e Fácies Orgânica (LAFO), Departamento de Geologia, Instituto de Geociências, Universidade Federal do Rio de Janeiro, Av. Athos da Silveira, 274, prédio do CCMN, sala J1020, Campus Ilha do Fundão, Cidade Universitária, Rio de Janeiro, RJ, CEP 21.949-900, Brazil.
Universidade de Coimbra, MARE - Centro de Ciências do Mare do Ambiente, ARNET - Aquatic Research Network, Departamento de Ciências da Terra, Rua Sílvio Lima, 3030-790, Coimbra, Portugal.
Sci Rep. 2023 Jan 23;13(1):1242. doi: 10.1038/s41598-022-26972-8.
Choanoflagellates are microeukaryotes that inhabit freshwater and marine environments and have long been regarded as the closest living relatives of Metazoa. Knowledge on the evolution of choanoflagellates is key for the understanding of the ancestry of animals, and although molecular clock evidence suggests the appearance of choanoflagellates by late Neoproterozoic, no specimens of choanoflagellates are known to occur in the fossil record. Here the first putative occurrence of choanoflagellates in sediments from the Cretaceous (Cenomanian-Turonian) is described by means of several cutting-edge petrographic techniques, and a discussion of its paleoenvironmental significance is performed. Furthermore, their placement in the organic matter classification systems is argued, with a placement in the Zoomorph Subgroup (Palynomorph Group) of the dispersed organic matter classification system being proposed. Regarding the ICCP System 1994, incorporation of choanoflagellates is, at a first glance, straightforward within the liptinite group, but the definition of a new maceral may be necessary to accommodate the genetic origin of these organisms. While modern choanoflagellates may bring light to the cellular foundations of animal origins, this discovery may provide an older term of comparison to their extant specimens and provide guidelines for possible identification of these organic components in other locations and ages throughout the geological record.
领鞭虫是一种微真核生物，栖息在淡水和海洋环境中，长期以来一直被认为是后生动物最接近的现存亲属。对领鞭虫进化的了解是理解动物祖先的关键，尽管分子钟的证据表明领鞭虫出现在晚新元古代，但在化石记录中尚未发现领鞭虫的标本。在这里，通过几种先进的岩相学技术首次描述了白垩纪（塞诺曼期-土仑期）沉积物中领鞭虫的假定出现，并对其古环境意义进行了讨论。此外，还对其在有机质分类系统中的位置进行了论证，提出将其归入分散有机质分类系统中的 Zoomorph 亚群（孢粉群）。关于 ICCP 系统 1994 年，在第一眼看来，领鞭虫很容易归入脂壳组，但可能需要定义一个新的镜质组来容纳这些生物体的遗传起源。虽然现代领鞭虫可能为动物起源的细胞基础带来启示，但这一发现可能为与其现存标本进行比较提供了一个更早的术语，并为在地质记录的其他地点和时代可能识别这些有机成分提供了指导。
