Arratia Gloria, Schultze Hans-Peter
Museum of Natural History, and Department of Systematics and Ecology, The University of Kansas, Lawrence, Kansas 66045-2454.
J Morphol. 1990 Mar;203(3):247-282. doi: 10.1002/jmor.1052030302.
The formation of the unpaired structure ventral to the basibranchial region, the so-called urohyal, differs within osteichthyans. A cartilaginous preformed, unpaired "urohyal" is present in sarcopterygians. A three-tendon ossification is present in Polypterus. An "urohyal" or urohyal is absent in both Amia and Lepisosteus. The urohyal formed as an unpaired ossification of the tendon of the sternohyoideus muscle is a feature of teleosts. A new structure, the parurohyal, arises as a double ossification of the tendon of the sternohyoideus muscle in siluroids; during ontogeny an anterodorsal crest or cup-like structure derives from the anterior basibranchial region and the tendon bone; therefore, the parurohyal is compound in origin. Judging from their formation and their distribution within osteichthyans the cartilaginous preformed "urohyal" and the teleostean urohyal are nonhomologous, whereas the urohyal and parurohyal are homologous. The urohyal is connected by ligaments with the ventral hypohyals in most teleosts, whereas it articulates with the ventral hypohyals in teleosts such as Anguilla and Chanos. The parurohyal is a synapomorphy of siluroids. The parurohyal in siluroids is articulated with both ventral and dorsal hypohyals, and with the basibranchial region in catfishes such as diplomystids and ictalurids, whereas it articulates only with the ventral hypohyals in other catfishes such as trichomycterines. The passage of the hypobranchial artery through the hypobranchial foramen of the parurohyal is a unique feature of siluroids, like the absence of the basihyal bone. An ossified dorsal hypohyal appears late in ontogeny in Amia, as do tooth plates related to the medial side of the hyoid arch and branchiostegal rays in Amia, and tooth plates on the hyoid arch and branchiostegal rays in Elops (unique features within extant teleosts). Two ossified hypohyals, a synapomorphy of teleosts, are present early in ontogeny. There is intraspecific variation in the onset of ossification of the bones of the head, but the sequence of ossification between bones in a defined structural system is conserved (e.g., branchiostegal rays ossify first, then bones of the hyoid arch).
在基鳃骨区域腹侧形成的不成对结构，即所谓的尾舌骨，在硬骨鱼中存在差异。肉鳍鱼中存在一个软骨预制的不成对“尾舌骨”。多鳍鱼中存在三腱骨化。弓鳍鱼和雀鳝中均不存在“尾舌骨”。由胸骨舌骨肌肌腱的不成对骨化形成的尾舌骨是硬骨鱼的一个特征。一种新结构，即副尾舌骨，作为鲇形目胸骨舌骨肌肌腱的双重骨化出现；在个体发育过程中，一个前背嵴或杯状结构源自前基鳃骨区域和肌腱骨；因此，副尾舌骨起源复杂。从它们在硬骨鱼中的形成和分布来看，软骨预制的“尾舌骨”和硬骨鱼的尾舌骨不同源，而尾舌骨和副尾舌骨同源。在大多数硬骨鱼中，尾舌骨通过韧带与腹侧下舌骨相连，而在鳗鲡和遮目鱼等硬骨鱼中，它与腹侧下舌骨相关节。副尾舌骨是鲇形目的一个共衍征。鲇形目的副尾舌骨与腹侧和背侧下舌骨均相关节，在双须缺鳍鲶和斑点叉尾鮰等鲶鱼中还与基鳃骨区域相关节，而在其他鲶鱼如毛鼻鲶科中，它仅与腹侧下舌骨相关节。鳃下动脉穿过副尾舌骨的鳃下孔是鲇形目的一个独特特征，就像基舌骨的缺失一样。在弓鳍鱼个体发育后期出现一个骨化的背侧下舌骨，与弓鳍鱼舌弓内侧相关的齿板和鳃盖条骨以及海鲢舌弓和鳃盖条骨上的齿板情况相同（现存硬骨鱼中的独特特征）。硬骨鱼的一个共衍征是在个体发育早期出现两块骨化的下舌骨。头部骨骼骨化的起始存在种内变异，但在一个确定的结构系统中骨骼之间的骨化顺序是保守的（例如，鳃盖条骨先骨化，然后是舌弓的骨骼）。
