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金龙鱼属(Scleropages: Osteoglossomorpha)一新种

发表日期:2019-12-13来源:放大 缩小

编辑:张江永 

摘要:记述了金龙鱼化石新材料,标本产于广东三水盆地华涌组,定为骨舌鱼科金龙鱼属一新种: 三水金龙鱼Scleropages sanshuiensis sp. nov.。新种在头部骨骼、尾骨骼、各鳍的形状和位置以及具有网状鳞片等方面与中华金龙鱼(Scleropages sinensis)和现生金龙鱼(Scleropages)极为相似,因而归入该属。而在金龙鱼属的四个现生种和中华金龙鱼之中,三水金龙鱼和中华金龙鱼在以下特征上更为接近:鼻骨前内侧有一凹陷,口缘前端的牙齿显著大于后端的,前鳃盖骨上端没有被围框骨完全覆盖,鳃盖骨后腹缘有一内凹,胸鳍长大,胸鳍内侧有一爪状骨,各鳍鳍条数目相同,脊椎数目相同,第一尾下骨宽大,鳞片大小相同,侧线鳞数目相似。但是,三水金龙鱼在下列特征上明显不同于中华金龙鱼:鼻骨上有纹饰,感觉管在鼻骨前端开孔于凹槽、在后端位于鼻骨内,感觉管进入眶前骨上端的凹槽小,第三眶下骨略小于第四眶下骨,鳃盖骨后腹缘的内凹浅,胸鳍往后延伸到腹鳍起点,躯椎上的神经棘不愈合,椎体横突长,第二尾下骨和第一尾椎不相接。三水金龙鱼与现生的金龙鱼也有相似之处,如鼻骨有纹饰、椎体横突长。同样,中华金龙鱼也有与现生金龙鱼相似的地方,如第三眶下骨略大于第四眶下骨、大多数躯椎上的神经棘愈合。尚不清楚三水金龙鱼和中华金龙鱼中哪一个与现生种更接近,这两个化石种可能处于相同的进化水平。中生代骨舌鱼类主要发现于中国,始新世骨舌鱼类化石在中国的发现也在逐渐增多,金龙鱼属(Scleropages)和骨舌鱼属(Osteoglossum)的共同祖先在始新世以前可能生存于东亚,并随后扩散到澳洲和世界其他地方。华涌组的骨舌鱼类和洋溪组的可以直接比较,因此,本项研究支撑华涌组的时代为早始新世的观点。关键词:三水盆地、广东,早始新世,华涌组,骨舌鱼科,骨舌鱼超目
卷期:第58卷,第2期

 

A New Species of Scleropages (Osteoglossidae, Osteoglossomorpha) from the Eocene of Guangdong, China

ZHANG Jiang-Yong

Abstract  A new species of Scleropages, an extant genus of Osteoglossidae, is described from the lower Eocene Huachong Formation in Sanshui Basin, Guangdong, China. The new species, Scleropages sanshuiensis sp. nov., was attributed to Scleropages for that it possesses the diagnostic features of the genus in skull bones, caudal skeleton, the shape and position of fins, and reticulate scales. Compared with the four extant and one fossil species of Scleropages, the new species is most similar to the fossil one, Scleropages sinensis in: the teeth on the anterior oral margin are much larger than those on the posterior; the upper limb of the preopercle is not completely covered by posterior infraorbitals; the posteroventral margin of the opercle is concave; the pectoral fin is very long; the ray number of all the fins is equal respectively; vertebrae are same in number; hypural 1 is very deep; scales are similar in size. However, S. sanshuiensis sp. nov. is different from S. sinensis in many aspects: the nasal is ornamented; the sensory canal of the nasal is exposed in a groove on the anterior half of the bone but is in a tube in the posterior half; dorsally the circumorbital sensory canal enters the antorbital via a small groove; the third infraorbital is slightly smaller than the fourth; the posteroventral margin of the opercle is slightly concave; the pectoral fin extends just to the beginning of the pelvic fin; the distal ends of the neural arches on abdominal centra are not fused; the parapophyses are much longer than in S. sinensis; the hypural 2 is probably unconnected with ural centrum 1. S. sanshuiensis sp. nov. is closer to S. sinensis but it shares two characters with the living species (ornamented nasal and long parapophyses) while S. sinensis shares two characters with the extant ones too (the third infraorbital slightly larger than the fourth and the distal ends of the neural arches on most abdominal centra fused). In addition to the rich Mesozoic osteoglossomorphs, many Eocene ones were also found from China. The common ancestor of Scleropages and Osteoglossum may live before the Eocene in East Asia and then dispersed to Australia and other places of the World. Huachong Formation and Yangxi Formations are comparable and possibly deposited contemporaneously. Therefore, this work supports the view that the Huachong Formation is of early Eocene.
Key words Sanshui Basin, Guangdong, China; Early Eocene; Huachong Formation; Osteoglossidae; Osteoglossomorpha

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