Data from: Endoskeletal structure in Cheirolepis (Osteichthyes, Actinopterygii), an early ray-finned fish

As the sister lineage of all other actinopterygians, the Middle to Late
Devonian (Eifelian–Frasnian) Cheirolepis occupies a pivotal position in
vertebrate phylogeny. Although the dermal skeleton of this taxon has been
exhaustively described, very little of its endoskeleton is known, leaving
questions of neurocranial and fin evolution in early ray-finned fishes
unresolved. The model for early actinopterygian anatomy has instead been
based largely on the Late Devonian (Frasnian) Mimipiscis, preserved in
stunning detail from the Gogo Formation of Australia. Here, we present
re-examinations of existing museum specimens through the use of
high-resolution laboratory- and synchrotron-based computed tomography
scanning, revealing new details of the neuro-cranium, hyomandibula and
pectoral fin endoskeleton for the Eifelian Cheirolepis trailli. These new
data highlight traits considered uncharacteristic of early
actinopterygians, including an uninvested dorsal aorta and imperforate
propterygium, and corroborate the early divergence of Cheirolepis within
actinopterygian phylogeny. These traits represent conspicuous differences
between the endoskeletal structure of Cheirolepis and Mimipiscis.
Additionally, we describe new aspects of the parasphenoid, vomer and
scales, most notably that the scales display peg-and-socket articulation
and a distinct neck. Collectively, these new data help clarify primitive
conditions within ray-finned fishes, which in turn have important
implications for understanding features likely present in the last common
ancestor of living osteichthyans.

作为所有其他辐鳍鱼类（actinopterygians）的姐妹支系，中至晚泥盆世（艾菲尔阶—弗拉斯阶）的掌鳍鱼属（Cheirolepis）在脊椎动物系统发育中占据关键地位。尽管该分类单元的外骨骼已被详尽描述，但其内骨骼的已知信息极少，导致早期辐鳍鱼类神经颅骨和鳍演化的问题悬而未决。早期辐鳍鱼类解剖学模型反而主要基于晚泥盆世（弗拉斯阶）的拟鱼属（Mimipiscis），其化石在澳大利亚戈戈组（Gogo Formation）中保存极为详尽。在此，我们通过高分辨率实验室及同步辐射计算机断层扫描（synchrotron-based computed tomography）对现有博物馆标本进行了重新检查，揭示了艾菲尔阶特拉尔掌鳍鱼（Cheirolepis trailli）神经颅骨、舌颌骨及胸鳍内骨骼的新细节。这些新数据凸显了早期辐鳍鱼类中被认为不典型的特征，包括未被包裹的背主动脉和无孔的前鳍骨，并证实了掌鳍鱼属在辐鳍鱼类系统发育中的早期分化。这些特征体现了掌鳍鱼属与拟鱼属内骨骼结构之间的显著差异。此外，我们描述了副蝶骨、犁骨及鳞片的新特征，其中最显著的是鳞片具有榫卯关节（peg-and-socket articulation）和明显的颈部。这些新数据共同助力阐明辐鳍鱼类的原始状态，进而对理解现生硬骨鱼类（osteichthyans）最近共同祖先可能具备的特征具有重要意义。