摘要
文中记述了华南鱼类两个新属,即 Gantarostrataspis gengi gen. et sp. nov. 和 Gumuaspis rostrata gen. et sp. nov.,同时对含鱼层的时代进行了讨论.
The specimens of Huananaspids described in this paper were collected from Gumu district, Southeast of Yunnan by Dr. Geng Baoyin, Institute of Botany, Academia Sinica. Their description covers 2 new species, 2 new genera. Besides, one new Family of Huananaspiformes is proposed. Occurred in the same bed are some yunnanolepids and some scales of crossopterygians and some plants, all of the fossils shows that the age of Posongchong Formation is from upper Gredinian to lower Siegenian. Description Order Huananaspiformes Janvier, 1975 Family Gantarostrataspidae Fam. nov. Diagnosis Medium sized Huananaspids with very well developed rostral process which is very long and wide, and very similar to duck's mouth in shape. Interzonal part of cephalic sheild very short. Sensory system displying non-typical pattern of polybranchiaspids. Gantarostrataspis gen. nov. G. gengi sp. nov. (Fig. 1; Pl. 1,2) Type A complete cephalic shield and its mould, V9758. Locality and Horizin Gumu, Yunnan; Posongchong Formation, Lower Devonian. Diagnosis Medium sized Huananaspiformes, cephalic shield fundamentally rectangle in shape with a maximum breadth of 40mm, shorter than length of shield. External margin (except the posterior margin) of cephalic shield with triangle spines. Rostral process well developed, very long and wide and very like duck's mouth in shape. Nostril rhombus, situated dorsally. Orbits are laterally placed as notches in edges of the cephalic shield. Pineal opening situated behind orbits. The length of rear-pineal about 1/4 of the length of propineal. The maximum breadth of rostral process about 1/3 of the length of rostral process. Sensory system displaying non-typical pattern of polybranchiaspids in which there is no median dorsal commissure between the longitudinal lateral canal, but the anterior ends of longitudinal lateral canal joined to form 'U'-shaped upside down, each longitudinal lateral canal with 4 lateral transversal canal without dichotomous ends, among which the last one is very short, every lateral transversal canal with some short longitudinal canal which connect both neighbours make the sensory system to be a cobweb on cephalic shield. Having 10 branchials sacs in each side. Remarks The new Huananaspids differs much from all genera of Huananolepidae, anqilepidae and Sanchiaspidae in well developed rostral process which is very long and wide, and very similar to duck's mouth in form. The form of nostril and the particular sensory system, which have never been seen in all known genera of Huananaspiformes, distinguish from all known genera of galeaspids. So that the material dealt with in this paper is named as a new form Gantarostrataspis gengi gen. et sp. nov., and a new Family was erected on the basis of the new material. Gantarostrataspis means the form of rostral process is very similar to duck's mouth; gengi, after Dr'. B. Y. Geng who is the collecter of this material. Discussion Before this paper, the sensory system pattern on the carapace in Eugaleaspiformes was considered to be quite stable, which consists of the supraorbital system, the infraorbital system and median dorsal commissure. The supraorbital system is 'V' in shape which do not contact immediately with the median dorsal commissure. On the basis of the pattern there are some changes that belong to the Family, genera or specific ones, for example, a short longitudinal canal connect with 'V'-shaped canal and median dorsal commissure in Sanchaspidae, and the supraorbital system not grown 'V'-shaped which is very like to 'funnel' in shape that is to say the posterior end of supraorbital do not contact each other in Cyclodiscaspis and Damaspis. There are important changes in the sensory system of Gantarostrataspis: the anterior end of longitudinal lateral canal had been joined each other to form the 'U'-shaped upside down, disprolonging forward to the lateral of the orbital opening, so the supraorbital canal and lateral transversal canal 1 is in contact with the 'U'-shaped part of longitudinal lateral canal at about rigth angle; the transversal lateral canal 1 and 2, 3 and 4 are connected by some short canals that made the sensory system to be a cobweb on the carapace. As a general rule in galeaspids, the sensory system pattern in which there is a median dorsal commissure between the two longitudinal lateral canal which situated in the place between transversal lateral canals 2 and 3, and the supraorbital canal itself never contact with the median dorsal commissure. But in Gantarostrataspis, the 'U'-shaped canal situated in front of the transversal lateral canal 1 and the superaorbital canal is in contact with the 'U'-shaped canal. So, the authors consider that the 'U'-shaped canal consists of the anterior part of longitudinal lateral canal, for this reason the median dorsal commissure is absent in the sensory system of Gamarostrataspis. In this new form the region from the pineal opening to the posterior margin of carapace is very short which has caused the disappearence of the median dorsal commissure, this condition is very similar to that the supraorbital sensory canal is degeneration or absent which was caused by the orbits very closer in Antiarchs and Osteostraci. Family Huananaspidae Liu, 1973 Gumuaspis gen. nov. G. rostrata gen. et sp. nov, (Fig. 2; Pl. II, 1,2) Type an incomplete cephalic shield in internal and external mould, V979.1,2. Locality and Horizon Gumu, Yunran; Posongchong Formation, Lower Devonian. Diagnosis Medium sized Huananaspidae. Cephalic shield fundamentally triangular with a long rostral process, about 80-90 mm in length, 65mm in breadth. Nostril opening ovel, but the length longer than breadth, situated at the top of a hillock dorsally. Rostral process well developed. Orbital opening ovel in shape, medium-sized, situated dorsally behind the rostral opening. Pineal opening perforating the carapace. Sensory system displaying polybranchiaspids pattern, but the longitudinal lateral canal unprolonging backward into the pectoral corners, transversal lateral canal without dichotomous or small radial polygon ends, each longitudinal lateral canal with 5 transversal lateral canals, among which the last one is very short. Having 9 branchials sacs each side. Ornamentation consisting of stellate like tubercles. Remarks Gumuaspis is a very peculiar fish among Huananaspidea in having a long rostral process, in this way the new material is very similar to Laxaspis rostrata, but the transversal lateral canal without small radial polygon ends and the nostril opening situated in the top of a hillock, so it is very easy to distinguish them. Therefore the new material dealt with in this paper is named as a new form, Gumuaspis rosrtata gen. et sp. nov. Gumuaspis means the fossil locality, rostrata shows the new form has a long rostral process.
出处
《古脊椎动物学报》
CSCD
北大核心
1992年第3期185-194,252-253,共10页
Vertebrata Palasiatica
关键词
云南文山
早泥盆世
无颌类
Wenshan, Yunnan
Early Devonian
Agnatha
