First Evidence of Dinosaurian Secondary Cartilage in the Post-Hatching Skull of Hypacrosaurus stebingeri (Dinosauria, Ornithischia)
First Evidence of Dinosaurian Secondary Cartilage in the Post-Hatching Skull of Hypacrosaurus stebingeri (Dinosauria, Ornithischia)
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DOI：
10.1371/journal.pone.0036112
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发表时间：
2012-04-30
期刊：
影响因子：
3.7
通讯作者：
Horner, John R.
中科院分区：
文献类型：
--
作者：
Bailleul, Alida M.;Hall, Brian K.;Horner, John R.
骨骼和钙化的软骨可以成为化石并保存数亿年。虽然初级软骨在现存的和化石的生物体中得到了相当好的研究，但对化石中的次级软骨却知之甚少。在现存的鸟类中，为了适应机械应力，在胚胎时期的关节、缝合线和肌肉附着处形成了骨形成后的次级软骨。考虑到鸟类在恐龙中的系统发育，我们假设这种“鸟”组织起源于恐龙。为此，本研究采用组织学薄片技术，对非禽类恐龙亚冠龙的几个孵化后标本的脱节颅面单元的继发性软骨发生进行了研究。次级软骨存在于三个与咀嚼功能直接相关的膜骨上：(1)在上颌骨的背-尾侧面上形成结节；(2)在上颌骨的颊-尾侧面上形成结节；(3)在牙槽突内的牙齿间形成胰岛。这些部位的继发软骨形成与现存鸟类中继发软骨的位置一致，也与不同机械因素诱导软骨的形成一致--方骨关节产生的应力，韧带或肌肉插入的应力，以及牙齿形成的应力。因此，我们的研究首次揭示了非鸟类恐龙体内存在“鸟类”次级软骨的证据。它将这种“鸟”组织的起源深入到恐龙的祖先，暗示了更恰当的术语“恐龙”次级软骨的产生。
Bone and calcified cartilage can be fossilized and preserved for hundreds of millions of years. While primary cartilage is fairly well studied in extant and fossilized organisms, nothing is known about secondary cartilage in fossils. In extant birds, secondary cartilage arises after bone formation during embryonic life at articulations, sutures and muscular attachments in order to accommodate mechanical stress. Considering the phylogenetic inclusion of birds within the Dinosauria, we hypothesized a dinosaurian origin for this "avian" tissue. Therefore, histological thin sectioning was used to investigate secondary chondrogenesis in disarticulated craniofacial elements of several post-hatching specimens of the non-avian dinosaur Hypacrosaurus stebingeri (Ornithischia, Lambeosaurinae). Secondary cartilage was found on three membrane bones directly involved with masticatory function: (1) as nodules on the dorso-caudal face of a surangular; and (2) on the bucco-caudal face of a maxilla; and (3) between teeth as islets in the alveolar processes of a dentary. Secondary chondrogenesis at these sites is consistent with the locations of secondary cartilage in extant birds and with the induction of the cartilage by different mechanical factors -stress generated by the articulation of the quadrate, stress of a ligamentous or muscular insertion, and stress of tooth formation. Thus, our study reveals the first evidence of "avian" secondary cartilage in a non-avian dinosaur. It pushes the origin of this "avian" tissue deep into dinosaurian ancestry, suggesting the creation of the more appropriate term "dinosaurian" secondary cartilage.