隆德鱼的新材料及其系统关系的初步分析——辽宁西部晚中生代地层和鱼群研究之一

A REVIEW OF LONGDEICHTHYS (TELEOSTEI:?CLUPEOCEPHALA) FROM NORTHERN CHINA

依据辽宁西部三个地点的新材料和宁夏、内蒙古的标本,对罗家峡隆德鱼(Longdeichthys luojiaxiaensis Liu,1982)的形态特征作了补充描述和修订,并初步分析讨论了“薄鳞鱼类”的研究现状以及隆德鱼的系统关系。认为隆德鱼可能已是鲱头鱼派(Clupeocephala)的成员,与德国和法国基末里期的Leptolepides sprattiformis(Blainville)最为相近。

The late Mr. Liu Zhicheng (1982) established a new leptolepid-level fish——Longdeichthys luojiaxiaensis, based on the specimens from the "Upper Jurassic" of Ningxia (V2333) and Nei Mongol (2334), and considered that this genus belongs to the family Leptolepidae.During the field works in 1990—1991, we have collected a large number of specimens of Longdeichthys from the Jiufotang Formation of Yixian, Chaoyang and Heishan of Liaoning Province (Northeastern China), of which the materials from Boluochi of Chaoyang are detached and scattered bones, partially well preserved, and concurrent with the early birds——Cathayornis Zhou, Jin and Zhang, 1992 etc.Subdivision Teleostei Cohort? Clupeocephala Family indet. Longdeiehthys Liu, 1982Emended diagnosis Medium-sized fusiform teleost fish. Large triangular frontals. Parietals small and not separated by the supraoccipital. Supraorbital sensory canal not extending onto the parietal, and middle pitline not crossing dermopterotic. Parasphenoid with regressive basipterygoid processes. One supraorbital, seven infraorbitals (including antorbital and dermosphenotic). Infraorbital sensory canal with only a few branches, and not extending to the antorbital. No suborbital bones. Two supramaxillae. Lower jaw composed of dentary with high coronoid process, fused angulo-articular, and independent retroarticular excluded from the joint surface for the quadrate. No teeth on jaw, palatopterygoids and parasphenoid. Preopercular sensory canal with 5—6 tubules and no bifurcations. Vertebrae made up of chordacentral, autocentral, and arcocentral elements with smooth surface and with autogenous neural and haemal arches. Dilpospondylous always present in caudal vertebrae, of which the precentrum bearing the neural and haemal arches. Supraneurals and epineurals present, but no epipleurals. Six uroneurals, and the anterior four extending forwards beyond U2. Three epurals. Eight hypurals, and parallelly aligned with caudal fin ray bases. Cycloid scales with grooves in the posterior field.Type and only species Longdeichthys luojiaxiaensis Longdeichthys luofiaxiaensis Liu Text-flgs. 1—81982 Longdeichthys luojigxigensis Liu, pp. 187—195, figs 1—5, pls. Ⅰ—ⅡDiagnosis As for genus. About 2/3 of specimens back convexed, the other 1/3 nearly straight. Length of skull larger than body depth, and being about 1/4 in total body length. Number of vertebrae 45—46, of them 20—21 in caudal region. Dorsal fin inserted between pelvic and anal fins, origin of anal fin nearly opposite the insertion of the last dorsal ray. Fin formula: P. ⅰ+14; V. ⅰ+10; D. ⅲ-ⅳ 11—12; A. ⅳ—ⅴ 19—20; C. ⅹⅱ 10+9 ⅹⅱ.Holotype A complete fish, catalog number of IVPP: V2333.1.Localities, horizons and age Luojiaxia, Longde County, Ningxia Huizu Autonomous Region; Heshangpu Formation (V2333.1—34). Wujiermiao, Hangjinqi, Nei Mongol; Member 6 of Zhidan Group (V2334.1—27). Pijiagou, Yixian (V10168.1—13), Boluochi, Chaoyang (V10169.1—14), Shuangshanzi, Heishan (V10170.1—5), Liaoning Province; Jiufotang Formation. Late Late Jurassic-early Early Cretaceous.Remarks Liu (1982) distinguished Longdeichthys luojiaxiaensis from other leptolepids by "the diplospondylous in the caudal region, the size and relative position of unpaired fins."The recent works by Patterson and Rosen (1977), Taverne (1975a, 1975b, 1977a, 1982), Arratia and Shultze (1985), and Arratia (1991) etc. have proved that many representatives of leptolepids belong to other different teleostean groups. In other words, the traditional group Leptolepidae is no longer monophyletic.The cladistic framework of certain pholidophorids, leptolepids, other Mesozoic lower teleosts, and the four extant groups by Patterson and Rosen (1977) could be taken as the initial basis to assign Mesozoic fossils phylogenetically. Of the 48 characters which specified 8 monophyletic taxa (Patterson & Rosen, 1977: pp. 128—130), Longdeichthys has all the features 1—20 of Leptolepis coryphaenoides and lower forms (apart from nos. 14—16 unknown in the present genus), three of the features of Tharsis dubius and higher groups: mid pitline groove never crossing dermopterotic, no suborbital bones, and autocentra (no sculptures in Longdeichthys). But at the T. dubius node, Longdeichthys lacks two devrived features: epipleurals and differentiated uroneurals, a condition much like those of the distribution of derived features by some well-known lower fossils, such as "Leptolepis" talbragarensis, Pachythrissops, Ascalabos voithii (cf. Patterson & Rosen, 1977). However, all the Me sozoic osteoglossomorphs found in China and Hiodon do not have epipleurals, and the uroneurals in the same alignment (per. obs.; Taverne, 1977b). Furthermore, many euteleostean groups (e.g. Siluriformes) lack the epipleural character either (cf. Arratia & Schuhze, 1985: p. 58), and most Mesozoic teleosts near or over the T. dubius node, such as P. propterus (Nybelin, 1971: Fig. 6B), "L." talbragarensis (Cavender, 1970: Fig. 1B), Luisichthys vinalensis (Arratia, 1991: Fig. 11), have undifferentiated uroneurals. Hence, epipleurals may be independently acquired by T. dubius and some higher groups, but differentiated uroneurals are possibly possessed by only a few forms.Longdeichthys is similar to Lycoptera davidi in the vertebral configuration, and the connection between hypurals and caudal fin ray bases. The caudal vertebrae of both Longdeichthys and Lycoptera are diplospondylous, the precentrum of which bears the neural and haemal arches (for Lycoptera, cf. Saito, 1936: p. 9; Gaudant, 1968: Fig. 13B and Arratia, 1991). In Longdeichthys, the caudal centra in the largest individual and even some precaudal vertebrae can be discriminated to be diplospondylous. This kind of vertebrae configuration is quite different from that of Amia calva and Pholidophorus bechei, in the latter form, the postcentrum bears the arches (Arratia, 1991: Fig. 1; Patterson, 1968: Fig. 1). But, the systematic significance of this difference is Unknown for lack of knowledge on the vertebral ontogeny of both extinct and extant teleosts.Although Longdeichthys has some similarities with primitive osteoglossomorphs, it can be easily distinguished from them by the distinct skull pattern, no complete neural spine on Pul, and 19 principal caudal fin rays etc..Longdeichthys lacks the derived feature of Elopocephala (there are still four uroneurals extending forward beyond U2 in the Chinese genus), but has three of the features of higher group Clupeocephala: fused angulo-articular, independent retroarticular excluded from the joint surface for the quadrate, and a membranous outgrowth on the antero-dorsal margin of Unl. The mosaic combination of characters in Longdeichthys makes its relationships rather perplexing.On the basis of present knowledge of teleostean phylogeny, it is equivocal to place Longdeichthys in a position like Tharsis dubius or within Clupeocephala in the cladogram of Patterson and Rosen (1977: Fig. 54) for its part possession of derived features of Osteoglossomorpha and Clupeocephala (see Tab. 1). For the time being, we prefer to ascribe Longdeichthys to Clupeocephala artificially.Within Clupeocephala, Leptolepides sprattiformis, from the Kimmeridgian of France and Germany, shows a particular similarity to Longdeichthys in skull skeleton (cf. Taverne, 1981: Fig. 2 with this paper, Fig. 1), and both share most of the derived features of Tharsis, Osteoglossomorpha, Elopocephala, and Clupeocephala (Tab. 1). However, Leptolepides differs from Longdeichthys in having epipleurals, differentiated uroneurals, fewer than 7 hypurals, only Unl extending forward beyond U2, but the retroarticular not excluded from the joint surface, that is, Leptolepides is more like a chpeocephalan than Longdeichthys.Longdeichthys. just like Leptolepides, lacks characters of Clupeomorpha and Euteleostei.