三记山东临朐中新世的鸟化石

在山东临朐解家河硅藻土矿中,此前曾先后出产过三件完整或部分完整的鸟化石,已分别经笔者研究,两次撰文发表(1977,1980)。1979年,临朐县文化馆又从该矿发现第四件完整的鸟化石,再次送与笔者研究,本文即此化石的研究报告。经鉴定、对比,认为该鸟化石应归鹤形目、秧鸡科,为一新属种,名为秀丽杨氏鸟。它是我国秧鸡科甚至鹤形目迄今已知保存最为完整、时代最早的化石代表。

THIRD NOTE ON FOSSIL BIRD FROM MIOCENE OF LINQU,SHANDONG

Before this note, three complete or partly complete specimens of fossil birds have been unearthed from the diatomacous bed of Linqu, Shandong, and were described respectively in two papers by the present author in 1977 and 1980. Recently, a fourth fossil bird was obtained again from the same locality and horizon by the members of Linqu County Museum, and was sent to the present author for study. It is an excellent specimen, and a third note of the group of this animal of Linqu County is therefore here proposed.Order Gruiformes Family Rallidae Genus Youngornis, gen. nov.Generic diagnosis——as for the species.Youngornis gracilis, sp. nov. (Pl. Ⅰ)Type A complete skeleton, but part of bones represent only by the concave prints in situ, skull roof missing, neck long, but indistinct, structures of trunk and girdles not so clear, anterior and posterior limbs well preserved.This specimen belongs to the Linqu County Museum, it will be sent back when the determination is made.Locality and Horizon Linqu County, Shandong Province; Middle Miocene (Shanwan Series).Diagnosis Size comparatively small, neck somewhat long. Bill short and stout, with its length shorter than that of tarsometatarsus. Humerus longer than ulna or radius. Bones of hind leg slender and long, but length of tarso-metatarsus still shorter than that of tibia. Four toes, three forward and one rearward, hind toe only slightly higher than others, and stands on same plane fundamentlly with front ones. Toes and claws thin and long, length of middle one (and its claw) longer than that of tarsometatarsus.Remarks At the first glance, the fossil bird here described has seemingly only three front toes, does it really have no hind toe? This is one of the important characters of birds in taxology. With the help of the magnifying glass, we found that there are two connected segments of concave prints situated slightly behind and higher to the inner toe of the right foot (see the enlarged part of the Plate I~*). The first segment is a phalanx, and the second is a claw, they are as long and slender as those seen in other toes forward. Furthermore, at the inner side of the lower part of tarsometatarsus, there projects slightly a small bone from which the concave prints mentioned above extend. The bone is here considered by the present author first metatarsus, and the concave prints hind toe. In the left foot, the same condition can be observed though the prints are not so clear as in the right one.The fossil bird takes a maximum height in preservation only in 202 mm. from its bill to the end of toe, it is a small bird. In view of its structures as a whole, especially the long and slender leg, we can consider it a member of grallatores (wading birds).Among the grallatores, the fossil bird differs clearly from many members by its bill. It also differs from some members of Charadriidae which do not bear a long bill by its developed hind toe. In view of the characters of the small size, the short and stout bill, the long and slender legs and toes, and the length of tarso-metatarsus longer than that of bill, but shorter than that of middle toe and its claw, the present specimen is comparable with some members of Rallidae of Gruiformes, especially those with a small size (such as Porzana).The fossil record of Rallidae is more numerous abroad, it is little known in our country except some fragments such as those from Quaternary of Choukoutien. The fossil bird here described hence represents the earliest and most complete one of Rallidae and even Gruiformes so far known in China, a new genus and species, Youngornis gracilis, of Family Rallidae is thus proposed. The generic name is in honour of my tuitor, late Prof. C. C. Young, who examined the diatomacous bed early in 1935, and named it for the first time "Shanwan Series", where the fossil birds and many other fossils were obtained.It is interesting to note that in the present specimen, on the surface of a place where the gizzard is situated under norma1 condition, some sands are gathered (see Plate I). The present author is hesitatingly to decide whether they are original "gastric sand" of the bird. If so, it would be truly a rare record in fossil bird, and the trunk of the specimen is really upward in preservation.A list of fossil birds so far known from Linqu, Shandong may be now grouped as follows:Galliformes Phasianidae Shandongornis shanwanensis Yeh, 1977 Linquornis gigantis Yeh, 1980 Anseriformes Anatidae Sinanas diatomas Yeh, 1980 Gruiformes Rallidae Youngornis gracilis, gen. et sp. nov.