Osteoderms are present in most tetrapod lineages with considerable lineage-specific variation. It has been hypothesized that osteoderms are a case of “deep homology” in craniates, but the embryonic origin of osteoderms -and other related postcranial exoskeletal elements- is still under debate. Most authors support its mesodermal origin, while others suggest that osteoderms are derived from neural crest scleroblastic cells in sauropsids. The armadillos (Xenarthra, Cingulata) are the only living mammals and the only extant synapsids with osteoderms. Here, we aim to identify skeletogenic neural crest cells in the dorsal skin of armadillos in order to assess if osteoderms have a neuroectodermal origin in mammals, similar to what is observed in sauropsids. For this purpose, skin samples from fetuses and newborn specimens of Dasypus hybridus were processed and the embryological development of osteoderms was characterized using different immunohistochemical markers (HNK-1, PDGFR α, S-100, and C5). For the first time, we report cell populations that were reactive to skeletogenic neural crest markers, indicating an ectomesenchymal origin of the mammalian osteoderms. Our results demonstrate similar molecular expression for mammals as in sauropsids and, therefore, this strongly suggests that osteoderms in both groups would have a homologous embryonic origin.

成骨细胞存在于大多数四足动物谱系中，谱系特异性差异很大。据推测，成骨细胞是颅骨中的“深层同源”，但成骨细胞的胚胎起源以及其他相关的颅后骨骼成分仍在争论中。大多数作者支持它的中胚层起源，而另一些人则认为成骨细胞来自蜥脚类动物的神经rest硬核细胞。犰狳（Xenarthra，Cingulata）是唯一活着的哺乳动物，并且是现存的唯一具有骨皮突触的突触。在这里，我们的目的是在犰狳的背部皮肤中鉴定出具有骨骼的神经rest细胞，以便评估在哺乳动物中骨皮是否具有神经外胚层起源，类似于在蜥脚类动物中观察到的情况。为此，从胎儿和新生儿标本的皮肤样本加工了Dasypus hybridus，并使用不同的免疫组织化学标记物（HNK-1，PDGFRα，S-100和C5）表征了真皮的胚胎发育。首次，我们报告了对骨骼形成性神经c标志物具有反应性的细胞群，表明了哺乳动物真皮的外源性起源。我们的结果证明了与蜥脚类动物相似的哺乳动物分子表达，因此，这有力地表明两组中的真皮都具有同源的胚胎起源。