Yangtzedonta是双壳类吗?

IS YANGTZEDONTA A BIVALVE?

对Yangtzedonta pri mitivaYu模式标本(标本登记号:84430)的化石保存类型进行讨论,确认这应当是一枚单壳瓣实体标本,而非内模标本,由此判断,余汶(1985;Yu,2005)所描述的肌痕实际上是不存在的。所谓的"片状齿突"(余汶,1985)或"片状脊"(Yu,2005)很可能是外来的附加物,并非壳体的组成部分。无论如何,84430标本现有的形态证据尚不足于将它与双壳类联系在一起。

Yu Wen （1985, 2005） mistook the holotype （cat. NIGP 84430） of Yangtzedonta primitiva Yu, 1985 for an internal mould. Since the holotype has preserved both internal and external shell surfaces, it is a body fossil rather than an internal mould. All the muscle scars described by Yu （1985, 2005） are sheer fiction because they cannot be preserved on the external shell surface. It is a pity that the interior of the holotype is covered by sediments so that we could not see any internal features. Electronic probe analysis of the holotype indicates that the so-called ＂lamellar tooth＂ （Yu, 1985, p. 407） or ＂lamellar ridge＂（Yu, 2005, p. 770） should be secondary phosphate features formed during diagnosis rather than original hinge structures （Qian, 2001）. In addition, we do not know the whole outline of the holotype because both ends of the holotype are broken. In any case, the bivalve nature of Yangtzedonta primitiva Yu is not yet proved.