关键词: 华南地区, 中泥盆世, 四足形类, “骨鳞鱼类”, 系统发育分析, 形态学测量

Abstract:

Tetrapodomorpha comprises all terrestrial vertebrates and their closest fish relatives. The oldest and most basal tetrapodomorphs are known from the Early Devonian of South China, suggesting that South China was a center for the origin of the tetrapod lineage. However, the phylogenetic relationships among early members of the lineage, particularly “osteolepids” (that is equivalent to Osteolepididae), remain poorly resolved. Here we describe a new tetrapodomorph specimen from the Middle Devonian Pearl River Source Scenic Area, Qujing, Yunnan, China. The material includes two anterior cranial portions and a lower jaw, which show overall similarity to Thursius wudingensis from the Middle Devonian of Wuding, Yunnan. High-resolution computed tomography (HRCT) reveals that the skull roof and dermal surface of the lower jaw of the material closely resemble those of T. wudingensis. In contrast, the neurocranial anatomy of the new material differs from those of other Thursius, especially in the morphology of the parasphenoid and the position of the buccohypophyseal foramen. Phylogenetic analysis recovers the new material as a possible sister taxon to T. wudingensis, while the interrelationships of “osteolepids” remain poorly resolved. To further assess the morphological variation and evolutionary relationship among the osteolepiforms, a principal component analysis (PCA) of parietal shield morphology for “osteolepiforms” was conducted, including representatives of Osteolepididae, Canowindridae, and Megalichthyidae. The PCA results are consistent with the phylogenetic analysis, placing the new material in close proximity to T. wudingensis. The new tetrapodomorph material from the Middle Devonian of the Pearl River Source Scenic Area provides new insights into the early evolution of the tetrapod lineage.

Key words: South China, Middle Devonian, Tetrapodomorpha, Osteolepiformes, phylogeny, morphometrics