辽宁早白垩世早期—鸟化石

A NEW FOSSIL BIRD FROM LOWER CRETACEOUS OF LIAONING

本文记述了发现于辽宁朝阳地区早白垩世早期一新的鸟类。这是继三塔中国鸟(Sinornis santensis)、燕都华夏鸟(Cathayomis yandica)之后报道的辽宁中生代第三种鸟化石,它的脊柱和腰带与始祖鸟和恐龙相似,但其肋骨又具有现代鸟类的性状,这是早期鸟类化石的又一新材料。

This paper describes a recently discovered fossil bird from the early Early Cretaceous of Chaoyang, Liaoning Province. Its morphological characteristics suggest that it is a new representative of early birds. The pelvis of the new bird is primitive and resembles that of Archaeopteryx, and its vertebral ribs are similar ro thoes of Hesperornis, Ichthyonis and modern birds, but differs from those of Sinornis and Cathayornis. Chaoyangia gen. nov. Chaoyangia beishanensis sp. nov. Holotype An incomplete skeleton, no skull and forelimb. Institute of vertebrate paleontology and paleoanthropology collection number V9934. Locality and horizon Chaoyang, Liaoning, Jiufotang Formation. Diagnosis Centrum non-heterocelous, sacral vertebrae more than 8 in number, and not fused, longitudinal groove present in proximal end of vertebral rib. Well ossified uncinate processes on ribs. Bones of pelvis not fused, pubis and ischium posteriorly inclined, shaft of pubis hollow with distal end fuesd, ilium nephroid, longer anterior to acetabulum than posterior to it, posterior part of ilium not constricted. Femur advanced, the fourth trochanter absent, femoral caput and femoral collum well developed. Tibial crest developed. Discussion This new fossil bird was collected from the Jiufotang Formation. Titherto, at least 20 well-preserved fossil bird specimens have been discovered from the locality. Chaoyangia is different from all the other specimens. Chaoyangia has the following primitive characters: 1) Centrum is non-heterocelous; 2) Sacral vertebrae are not fused; 3) Ilium, ischium and pubis are not fused; 4) The distal end of pubis is fused. Chaoyangia has the following evolutionary derived characters: 1) Ribs have well ossified uncinate processes; 2) Presence of ossified sternal rib; 3) Long bones are thin-walled and their shafts are hollow; 4)Sacral vertebrae are more than 8 in number; 5) Femoral caput is large and the fourth trochanter is absent; 6) Tibial crest is developed. Chaoyangia has the following characters in comparison with the other early birds: 1) The vertebral rib has a longitudinal groove on the proximal end; 2) The ilium is nephroid, and longer anterior to the acetabulum than posterior to it; 3) The pubis has a hollow-shaft and long fused distal end. Chaoyangia has more strong sternal part, specialized flyers than Sinornis and Cathayornis.