Spiekman Stephan N F, Foth Christian, Rossi Valentina, Gascó Martín Cristina, Slater Tiffany S, Bath Enright Orla G, Dollman Kathleen N, Serafini Giovanni, Seegis Dieter, Grauvogel-Stamm Léa, McNamara Maria E, Sues Hans-Dieter, Schoch Rainer R
Staatliches Museum für Naturkunde Stuttgart, Stuttgart, Germany.
Institut für Biowissenschaften, Allgemeine und Spezielle Zoologie, Universität Rostock, Rostock, Germany.
Nature. 2025 Jul;643(8074):1297-1303. doi: 10.1038/s41586-025-09167-9. Epub 2025 Jul 23.
Complex integumentary appendages such as avian feathers and mammalian hair play a principal role in tetrapod evolution, with critical functions in insulation, sensation, display and flight. Although feathers and hair originated in the stem-lineages of birds and mammals, respectively, their underlying gene regulatory network has much deeper amniote roots. The early evolution of amniote integumentary appendages, however, remains poorly understood because of the absence of fossil evidence. Here we present Mirasaura grauvogeli, a small-sized diapsid from the Middle Triassic epoch (about 247 million years ago) with a distinctive crest formed by elongate integumentary appendages extending serially along its back, similar to those of the poorly understood Triassic reptile Longisquama. Despite its superficially bird-like skull, Mirasaura is not closely related to avemetatarsalians but instead belongs to the exclusively Triassic reptilian clade Drepanosauromorpha. Melanosomes preserved in its integumentary appendages are consistent in geometry with melanosomes of feathers but not those of reptilian skin or mammalian hair. Nevertheless, the morphology of the integumentary appendages and phylogenetic placement of Mirasaura indicate that they are not structurally homologous to feathers or other integumentary appendages in living amniotes. Our findings show that complex integumentary appendages are not restricted to avemetatarsalians and mammaliaforms among amniotes and evolved in a lineage basal to all extant reptiles, challenging our understanding of the evolution of the reptilian integument.
复杂的皮肤附属器，如鸟类羽毛和哺乳动物毛发，在四足动物进化中发挥着重要作用，具有绝缘、感觉、展示和飞行等关键功能。尽管羽毛和毛发分别起源于鸟类和哺乳动物的主干谱系，但其潜在的基因调控网络在羊膜动物中有更深的根源。然而，由于缺乏化石证据，羊膜动物皮肤附属器的早期进化仍知之甚少。在此，我们介绍了米拉龙（Mirasaura grauvogeli），一种来自中三叠世时期（约2.47亿年前）的小型双孔类动物，其背部有由沿背部连续延伸的细长皮肤附属器形成的独特嵴，类似于了解甚少的三叠纪爬行动物长鳞龙（Longisquama）。尽管米拉龙的头骨表面类似鸟类，但它与鸟跖类动物并无密切关系，而是属于仅存在于三叠纪的爬行动物类群镰龙形目（Drepanosauromorpha）。保存在其皮肤附属器中的黑素体在几何形状上与羽毛的黑素体一致，而与爬行动物皮肤或哺乳动物毛发的黑素体不同。然而，米拉龙皮肤附属器的形态及其系统发育位置表明，它们在结构上与现存羊膜动物的羽毛或其他皮肤附属器并非同源。我们的研究结果表明，复杂的皮肤附属器并不局限于羊膜动物中的鸟跖类动物和哺乳形类动物，而是在所有现存爬行动物的一个基部谱系中进化而来，这挑战了我们对爬行动物皮肤进化的理解。
