New discoveries of lepidosteoid scales from the Upper Cretaceous in Songliao Basin, China

This study explores the morphological and histological characteristics of isolated rhomboid scales recovered from the Late Cretaceous Nenjiang Formation in Northeast China. Six distinct scale morphotypes were identified and compared with scales of various Holostei taxa. Macroscopic observations reveal that most scale exhibit small or completely absent peg-and-socket articulations and lack of tubercles and denticles. Histologically, these scales display lepidosteoid-type ganoid scale characteristics: a multi-layered enameloid layer forms the ganoine covering, which overlies the isopedine layer. The isopedine layer is densely penetrated by numerous Williamson's canals and contains abundant well-developed osteocyte lacunae. Although these isolated scale fossils resemble primitive Holostei scales, they cannot be confidently assigned to any known neopterygian taxa. The detailed morphological and histological analyses of these isolated Cretaceous scale fossils provide more precise data, advancing our understanding of Mesozoic fish diversity and evolutionary trends in the Songliao Basin. (c) 2025 Elsevier Ltd. All rights are reserved, including those for text and data mining, AI training, and similar technologies.