Our understanding of the ecology and phylogenetic relationships of Pachycormiformes, a group of Mesozoic stem teleosts including the iconic Leedsichthys, has often been hindered by a lack of comprehensive morphological information. Micro‐CT scanning of an articulated, although flattened, cranium of the edentulous Martillichthys renwickae from the Middle Jurassic (Callovian) Oxford Clay of the UK reveals previously unknown internal details of the most complete suspension‐feeding pachycormiform skull known, including the palate, braincase and branchial skeleton. The latter preserves gill rakers with elongate, pointed projections similar to those of Asthenocormus, in contrast to the finer fimbriations associated with Leedsichthys. We also reinterpret some previously described features, including dermal bone patterns of the snout, skull roof and lower jaw, and the morphology of the ventral hyoid arch. These new anatomical data reinforce the phylogenetic placement of Martillichthys as part of the Jurassic clade of edentulous pachycormiforms. The elongate skull geometry of these Jurassic taxa is strikingly similar to that of Ohmdenia, the sister taxon to edentulous pachycormiforms, but contrasts sharply with the morphology of the Late Cretaceous edentulous pachycormiform Bonnerichthys, raising questions over the phylogenetic relationships among these taxa. Most significantly, Martillichthys shows specialized characters with a restricted phylogenetic distribution among suspension‐feeding pachycormiforms, including the distinctive gill rakers and a greatly extended occipital stalk. Our analysis of Martillichthys supports past interpretations of a close relationship with Asthenocormus, and provides a model for interpreting the less complete remains of other members of this enigmatic group of fishes.

中文翻译：

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中侏罗世（Callovian）Martillichthys renwickae（Neopterygii，Pachycormiformes）的颅骨骨科，并评价了无牙齿形pachycormiforms的进化和生态学

我们对Pachycormiformes（一组中生的硬骨鱼，包括标志性的Leedsichthys）的生态学和系统发育关系的理解常常因缺乏全面的形态学信息而受到阻碍。Micro-CT扫描了来自英国中侏罗纪（Callovian）Oxford Clay的无齿的Martillichthys renwickae的一个铰接但平坦的颅骨的颅骨，揭示了以前未知的最完整的悬吊式喂食性厚吻鳄头骨的内部细节，包括including，脑箱和branch骨骨架。后者保留了耙，它们具有细长的，尖锐的突起，类似于As蛇科的突起，而与利氏鱼相关的纤毛则相反。我们还重新解释了一些先前描述的特征，包括鼻子的真皮骨骼图案，颅骨顶和下颌骨，以及腹舌舌弓的形态。这些新的解剖学数据加强了Martillichthys的系统发育定位，使其成为无齿的草角形侏罗纪进化枝的一部分。这些侏罗纪类群的细长的头骨形状是惊人地相似的Ohmdenia，姐妹类群以缺牙pachycormiforms，但对比与晚白垩世无牙颌pachycormiform的形态急剧Bonnerichthys，提高了这些类群之间的亲缘关系的问题。最重要的是，Martillichthys表现出特殊的特征，在悬浮喂养的拟臀目鱼之间有有限的系统发育分布，包括独特的g耙和大大延长的枕茎。我们对Martillichthys的分析支持了过去对与Asthenocormus亲密关系的解释，并提供了一个模型来解释该神秘鱼类其他成员的残缺不全。