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首页> 外文期刊>Paleontological journal >A New Petalodont Chondrichthyan from the Bear Gulch Limestone of Montana, USA, with Reassessment of Netsepoye hawesi and Comments on the Morphology of Holomorphic Petalodonts
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A New Petalodont Chondrichthyan from the Bear Gulch Limestone of Montana, USA, with Reassessment of Netsepoye hawesi and Comments on the Morphology of Holomorphic Petalodonts

机译：来自美国蒙大纳州熊沟石灰石的新的花瓣状软骨石，通过对Netsepoye hawesi的重新评估和对全形花瓣状石的形态的评论

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摘要

A new holomorphic petalodont from the Bear Gulch Limestone, Obruchevodus griffithi, is described and features of the related Netsepoye hawesi are reinterpreted. Comparison of these taxa with the holomorphic petalodonts Janassa bituminosa, Belantsea montana, and Siksika ottae provide insight into petalodont anatomical form and variation. All holomorphic material supports holostyly and nested, subcranial branchial arches. Teeth occur in families with linguo-labial replacement but alignment of most families relative to the jaw ramus results in a staggered tooth alignment between adjacent tooth families. Symphysial teeth are the exception to this pattern. Tooth retention is clearly indicated only in the homodont Janassa bituminosa. In contrast there is no evidence of tooth retention in examined petalodonts with a heterodont dentition. There is variation in styles of squamation among all forms; sexual dimorphism in scale development and distribution are suggested as well. Despite depressiform and compressiform conditions there is commonality in possession of a lobular, anteriorly extended and high aspect ratio pectoral fin, large pelvic fins, and absence of fin spines. Pectoral fins provide the primary means of locomotion. Variation in the ventral aspect of the pelvic girdle anatomy exists between that interpreted for Janassa and that documented by Obruchevodus and Netsepoye. Male claspers are long and highly flexible. Laterally compressed body forms display two dorsal fins (first being largest) that are variable in their vertical expanse along the length of the fin. Cranial anatomy shows some correspondence to general features of the Holocephali. Meckel's cartilage is dorso-ventrally deep, as in extant chimaeroids, with contralaterals in symphysial fusion. Mandibular labial cartilages, when present, may be sexually dimorphic.
机译：描述了一种来自熊沟石灰石的新全形花瓣状牙齿，即Obruchevodus griffithi，并重新解释了相关的Netsepoye hawesi的特征。将这些类群与全形花瓣齿科的Janassa bituminosa，Berantsea montana和Siksika ottae进行比较，可以深入了解花瓣齿科的解剖形式和变异。所有全同质材料均支持完整的和嵌套的颅下branch弓。牙齿发生在唇阴唇置换的家庭中，但是大多数家庭相对于下颌支的对齐导致相邻牙齿家庭之间交错的牙齿对齐。对称的牙齿是该模式的例外。仅在同齿亚纳萨沥青中清楚地表明了牙齿固位。相比之下，在检查的异齿牙列的花瓣牙上没有牙齿保留的迹象。各种形式的皮肤鳞状都有差异。还建议在规模发展和分布中存在性二态性。尽管有凹陷状和压缩状的情况，但小叶状，向前方延伸且长宽比高的胸鳍，大​​骨盆鳍和无鳍棘的情况很普遍。胸鳍是运动的主要手段。盆腔带解剖学的腹侧方面存在差异，Janassa所解释的与Obruchevodus和Netsepoye所记录的之间。公扣子很长，而且高度灵活。横向压缩的身体形态显示了两个背鳍（第一个最大），它们的垂直宽度沿鳍的长度可变。颅骨解剖显示与头颅的一般特征有些对应。 Meckel的软骨与现有的类痔一样背腹深，在对侧融合中有对侧。下颌唇软骨存在时，可能是性二态。

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