河南明港—始新世鸟类形态观察

本文记述了一发现于河南明港始新世较小型涉禽类的尺骨和胫跗骨远端化石。依据尺骨远端腱凹窄而浅,桡骨凹大,外侧具一纵沟和胫跗骨外关节髁外侧面中央有一窄纵嵴等特征定一新属种:张沟明港鹮Minggangiachanggouensis gen.et sp.nov. 明港鹮的时代为晚始新世,它代表迄今为止我国发现的鹳形目最早的鸟类。

NEW FORM OF THE THRESKIONITHIDAE FROM THE UPPER EOCENE OF THE MINGGANG, HENAN

Among the collections of Upper Eocene fossil vertebrates excavated from Henan by the members of the second geological team in 1972 there are two bird bones including a distal end of the ulna and a distal end of the tibiolarsus. They were discoved from Lizhuang Formation at the locality named Xi Zhang-gou, in the Minggang area, Henan Province. Minggangia changgouensis gen. et sp. nov. Minggangia is a member of Threskiornthidae by possessing the following characteristics: The bird is a little smaller than the Threskiornis, the distal end of the ulna is laterally compressed; the tendinal groove is shallower and smaller than that in the Threskiornis; the lateral compressive distal extremity of the tibiotarsus is less marked, and the intcrcondylar tubercle tends to disappear more or less completely; the osseous supratendinal bridge is long, the canal for tendon passing the bridge is the small; the supratendinal bridge on the distal end of tibiotarsus is displaced internally ; tuberosity on bridge lies above the external side of canalis extensovius; and the intercondylar tubercle is not well devclped. Diagnosis of this fossil bird is as follows: A very small threskiornithid. Tendinal pit of the distal end of ulna narrow and shallow (fig. 1, 2) ; distal radial depression large, with a groove on the external side; tuberculum carpale taller than Threskionis, and the postrior trochlcar surface deep and wide. Inner condyle of tibiotarsus projects forwards prominently; external condyle wide, with a midcrest on external side (fig. 2, 1). Comments: The tibiotarsus is similar to those of Ibidopsis hordwelliensis, the only other Eocene threskiothid, and known as follow: supratendinal bridge is situated towards inner condyle, but is different in size that Ibidopsis hordwelliensis is bigger than Minggangia, and the tuberosity on bridge is small. The nearest relative of Minggangia is Threskiornis, but the two are differences in the size, Minggangia is smaller, the sulcus tendineus of the ulna, distal radial depression and in the intercondylar tubercle with external condyles. Minggangia is similar to Ardea in size and the construction of the intercondylar tubercle, but different from it in sulcus radialis, sulcus tendineus, tuberosity bridge and the distal end of tibiotarsus etc, therefore Minggangia can not belong to the Ardeidae. These feature make Minggangia distinguished from all the other genera. Thanks are due to Dr. P. V. Rich for sending me many references.