For almost 150 years, megascopic structures in siliciclastic sequences of terminal Precambrian age have been frustratingly difficult to characterize and classify. As with all other areas of human knowledge, progress with exploration, documentation and understanding is growing at an exponential rate. Nevertheless, there is much to be learned from following the evolution of the logic behind the biological interpretations of these enigmatic fossils. Here, I review the history of discovery as well as some long-established core members of widely recognized clades that are still difficult to graft on to the tree of life. These ‘orphan plesions’ occupy roles that were once held by famous former Problematica, such as archaeocyaths, graptolites and rudist bivalves. In some of those cases, taxonomic enlightenment was brought about by the discovery of new characters; in others it required a better knowledge of their living counterparts. Can we use these approaches to rescue the Ediacaran orphans? Five taxa that are examined in this context are Arborea (Arboreomorpha), Dickinsonia (Dickinsoniomorpha), Pteridinium plus Ernietta (Erniettomorpha) and Kimberella (Bilateria?). With the possible exception of Dickinsonia, all of these organisms may be coelenterate grade eumetazoans.

近 150 年来，前寒武纪末期硅质碎屑序列中的巨观结构一直难以表征和分类。与人类知识的所有其他领域一样，探索、记录和理解方面的进步正以指数速度增长。然而，从对这些神秘化石的生物学解释背后的逻辑演变过程中，我们可以学到很多东西。在这里，我回顾了发现的历史，以及一些公认的进化枝的长期核心成员，这些进化枝仍然难以嫁接到生命之树上。这些“孤儿病”占据了曾经由著名的前有问题的人担任过的角色，例如古菌、笔石和双壳类动物。在其中一些情况下，新性状的发现带来了分类学的启迪；在其他情况下，它需要更好地了解他们的生活同行。我们能用这些方法来拯救埃迪卡拉纪的孤儿吗？在这种情况下检查的五个分类群是Arborea (Arboreomorpha)、Dickinsonia (Dickinsoniomorpha)、Pteridinium plus Ernietta (Erniettomorpha) 和Kimberella (Bilateria?)。除了狄更斯氏菌之外，所有这些生物都可能是腔肠动物级的真后生动物。