Haplocheirus
The holotype of Haplocheirus
- Xinjiang (China)
Haplocheirus (Size: haplocheir = simple hand) was a small dinosaur from the Upper Jurassic ( Oxfordian ). A very good, three-dimensionally preserved fossil was found in the Shishugou Formation in the Junggar Basin in Xinjiang (China). Haplocheirus is placed in the relationship of Alvarezsauridae.
The only way is Haplocheirus sollers. The Style epithet Sóller (Latin: = talented ) was awarded because of the still existing gripping ability of the forequarters.
Features
Haplocheirus was about 1.90 to 2.30 meters long, the exact size is unknown, since the end of the tail is missing. His graceful, low skull is 14 cm long. Of all Alvarezsauriden, of which there are nearly complete skeletons, it is the largest genus.
On the maxillary 30 teeth are present, more than any other Alvarezsauriden. The teeth are not tapered, curved like other Alvarezsauriden, but backwards and slightly serrated. The teeth decrease in size from front to back. This also applies to the teeth in the dental, the front bears some major unsawn teeth. Probably Haplocheirus malnourished even meat from larger animals, while the later Alvarezsauridae insectivores were.
In contrast to developed Alvarezsauriden whose third and fourth fingers of the forequarters were greatly reduced and their enlarged claw of the second finger was converted to a grave claw Haplocheirus could grasp with his hand still. However, the hand of Haplocheirus already shows the subsequent development, the second finger was thickened, thin, the third greatly extended the other two.
System
Haplocheirus is a close relative of Alvarezsauridae, little bird -like dinosaur whose systematic position has been very uncertain. His discovery extends the stratigraphic evidence of the group around 63 million years into the past and shows that the Alvarezsauridae were no birds, as is often assumed shortly after its discovery, but that the bird-like features have repeatedly developed within the Maniraptora.
The systematic position cladogram shows the following:
Haplocheirus
Alvarezsauridae
Therizinosauroidea
Oviraptorosauria
Avialae (birds in the wider sense )
Troodontidae
Dromaeosauridae