How does the curvature of the upper beak bone reflect the overlying rhinotheca morphology?
How does the curvature of the upper beak bone reflect the overlying rhinotheca morphology?
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上喙骨的曲率如何反映上面的鼻甲形态？
DOI：
10.1002/jmor.20799
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发表时间：
2018
影响因子：
1.5
通讯作者：
Shin-ichi Fujiwara
中科院分区：
文献类型：
--
作者：
Yukine Urano;Kyo Tanoue;Ryoko Matsumoto;Soichiro Kawabe;Tomoyuki Ohashi;Shin-ichi Fujiwara
在许多四足动物中，包括现存的龟鳖目和鸟类，喙都是伴随着无齿现象独立进化的，其形态和功能也发生了很大的变化。喙由喙骨和覆盖在其上的角质覆盖物形成，尽管它们的轮廓彼此不同。因此，很难可靠地重建整个轮廓的喙在灭绝的类群，其角质组织很少保存。为了阐明喙骨和上覆角质层之间的形态学关系，我们使用CT扫描比较了66个现存的龟类和鸟类标本（鸟类：33属，24科;龟类：12属，7科）的上喙骨和上覆角质层（鳃鞘）的曲率分布。喙骨和腹鞘的曲线在吻侧的某个点处几乎是恒定的，该点被定义为过渡点，并且腹鞘和喙骨的过渡点彼此靠近。喙鞘和喙骨喙部到它们的过渡点的轮廓在曲率和长度上是不同的。然而，喙鞘和喙骨的曲率之间的比率与喙骨的喙侧沟轮廓的弧角密切相关。利用上述喙骨和鸟鞘之间的关系，可以更可靠地重建已灭绝类群的上喙轮廓。
The beak has independently been evolved accompanied by the edentulism in many tetrapod linages, including extant Testudinata and Aves, and its form and function have been greatly diversified. The beak is formed by beak bones and the overlying keratinous cover, although their profiles are different from each other. Therefore, it is difficult to reliably reconstruct the entire profile of the beak in extinct taxa, whose keratinous tissues are rarely preserved. For elucidation of the morphological relationship between beak bone and overlying keratinous cover, we compared the curvature distribution of the culminal profiles of the upper beak bone and the overlying keratinous cover (rhinotheca) with each other using CT‐scan, in 66 extant testudinatan and avian specimens (Aves: 33 genera, 24 families; Testudinata: 12 genera seven families). In both, rhinotheca and beak bone, the curvature of the profile was nearly constant rostral to a certain point, which was defined as the transition point, and the transition points of the rhinotheca and beak bone were close to each other. The profiles of the rhinotheca and beak bone rostral to their transition point were different in curvature and length. However, the ratio between the curvatures of rhinotheca and the beak bone strongly correlated with the arc angle of the rostral culminal profiles of the beak bone. The upper beak profile in extinct taxa is expected to be reconstructed more reliably using the abovementioned relationship between the beak bone and the rhinotheca.