科学家在阿根廷西北部发现了一具236百万年前的兽孔目动物化石，其中包含的生物学证据表明胎生繁殖在哺乳动物谱系中的出现时间远早于既有认识 [1]。这具属于物种Chiniquodon theotonicus的化石展现了新生长线和异常大的出生体型，与现代哺乳动物的繁殖特征相符 [1]。
首席作者、来自阿根廷国立科技研究委员会的Leandro Gaetano博士指出："我们首次证明，活胎生殖在至少一种哺乳动物祖先Chiniquodon theotonicus中存在，该物种生活在大约236百万年前" [1]。根据分析结果，这具新生个体体重约1.7公斤，成年体重约12公斤，新生体型占成年体质量的14% [1]。
Gaetano博士表示："这意味着早期兽孔目动物中的胎生繁殖在哺乳动物谱系中的起源，比之前认为的时间早95至90百万年" [1]。该研究成果已于2026年8月13日发表在《哺乳动物科学前沿》期刊上 [1]。
Scientists have uncovered evidence that live birth may have originated in the mammalian lineage roughly 95 to 90 million years earlier than previously believed.[1] A 236-million-year-old fossil of Chiniquodon theotonicus, a cynodont discovered in northwestern Argentina, displays growth lines and an unusually large birth size consistent with modern mammalian reproduction patterns.[1] Lead researcher Leandro Gaetano from Argentina's National Scientific and Technical Research Council (CONICET) stated: "We show for the first time that live birth was present in at least one mammalian ancestor, Chiniquodon theotonicus, which lived approximately 236 million years ago."[1]
The fossil's newborn weighed approximately 1.7 kilograms, while the adult specimen reached about 12 kilograms—meaning the offspring represented roughly 14 percent of adult body mass.[1] These proportions align with patterns seen in modern viviparous mammals, suggesting that reproductive strategy emerged far deeper in mammalian evolutionary history than previously recognized.[1] According to Gaetano, "This implies that viviparity among early cynodonts originated in the mammalian lineage at least 95 to 90 million years earlier than previously thought."[1] The findings were published in Frontiers in Mammal Science on August 13, 2026.[1]