Despite the diverse morphology of the adult squamate naso-palatal complex – consisting of the nasal cavity, vomeronasal organ (VNO), choanal groove, lacrimal duct and superficial palate – little is known about the embryology of these structures. Moreover, there are no comprehensive studies concerning development of the nasal cavity and VNO in relation to the superficial palate. In this investigation, we used X-ray microtomography and histological sections to describe embryonic development of the naso-palatal complex of iguanian lizard, the brown anole (Anolis sagrei). The purpose of the study was to describe the mechanism of formation of adult morphology in this species, which combines the peculiar anole features with typical iguanian conditions. Considering the uncertain phylogenetic position of the Iguania within Squamata, embryological data and future comparative studies may shed new light on the evolution of this large squamate clade. Development of the naso-palatal complex was divided into three phases: early, middle and late. In the early developmental phase, the vomeronasal pit originates from medial outpocketing of the nasal pit, when the facial prominences are weakly developed. In the middle developmental phase, the following events can be noted: the formation of the frontonasal mass, separation of the vestibulum, appearance of the lacrimal duct, and formation of the choanal groove, which leads to separation of the VNO from the nasal cavity. In late development, the nasal cavity and the VNO attain their adult morphology. The lacrimal duct establishes an extensive connection with the choanal groove, which eventually becomes largely separated from the oral cavity. Unlike in other tetrapods, the primordium of the lacrimal duct in the brown anole develops largely beyond the nasolacrimal groove. In contrast to previous studies on squamates, the maxillary prominence is found to participate in the initial fusion with the frontonasal mass. Moreover, formation of the choanal groove occurs due to the fusion of the vomerine cushion to the subconchal fold, rather than to the choanal fold. The loss or significant reduction of the lateral nasal concha is secondary. Some features of anole adult morphology, such as the closure of the choanal groove, may constitute adaptations to vomeronasal chemoreception.

中文翻译：

---

鳞状鼻腭复合体的发育：棕色 anole Anolis sagrei（Squamata：Iguania）犁鼻器官和鼻腔的详细 3D 分析

尽管成人鳞状鼻腭复合体的形态多种多样——由鼻腔、犁鼻器 (VNO)、后鼻孔、泪管和浅腭组成——但对这些结构的胚胎学知之甚少。此外，没有关于鼻腔发育和VNO与浅腭相关的综合研究。在这项调查中，我们使用 X 射线显微断层扫描和组织切片来描述鬣蜥蜥蜴的鼻腭复合体的胚胎发育，棕色 anole (Anolis sagrei)。该研究的目的是描述该物种成虫形态的形成机制，将特有的 anole 特征与典型的鬣蜥条件相结合。考虑到 Iguania 在 Squamata 中的系统发育位置不确定，胚胎学数据和未来的比较研究可能会为这种大型鳞状进化枝的进化提供新的线索。鼻腭复合体的发育分为早期、中期和晚期三个阶段。在早期发育阶段，犁鼻坑起源于鼻窝的内侧外突，此时面部突起发育较弱。在发育中期，可以注意到以下事件：额鼻肿块的形成、前庭的分离、泪管的出现和后鼻孔的形成，这导致 VNO 从鼻腔中分离出来。在晚期发育中，鼻腔和 VNO 达到成人形态。泪管与后鼻沟建立广泛的连接，最终与口腔分离。与其他四足动物不同，棕色 anole 的泪管原基在很大程度上超出了鼻泪沟。与之前对鳞状动物的研究相反，发现上颌突参与了与额鼻肿块的初始融合。此外，由于犁骨垫与甲骨下皱襞融合，而不是与后颅骨皱襞融合，形成了后鼻孔。侧鼻甲的丢失或显着减少是次要的。anole 成人形态的一些特征，例如后鼻孔的闭合，可能构成对犁鼻化学感受的适应。与之前对鳞状动物的研究相反，发现上颌突参与了与额鼻肿块的初始融合。此外，由于犁骨垫与甲骨下皱襞融合，而不是与后颅骨皱襞融合，形成了后鼻孔。侧鼻甲的丢失或显着减少是次要的。anole 成人形态的一些特征，例如后鼻孔的闭合，可能构成对犁鼻化学感受的适应。与之前对鳞状动物的研究相反，发现上颌突参与了与额鼻肿块的初始融合。此外，由于犁骨垫与甲骨下皱襞融合，而不是与后颅骨皱襞融合，形成了后鼻孔。侧鼻甲的丢失或显着减少是次要的。anole 成人形态的一些特征，例如后鼻孔的闭合，可能构成对犁鼻化学感受的适应。