采自云南昆明市海口地区下寒武统筇竹寺组的昆明鱼为活埋标本，其软躯体构造保存极为精美；来自同一层位的海口鱼为正常死亡后埋藏，除身体最后部略有腐烂外，整体特征保存良好。这两种鱼皆呈鱼形，不仅具带鳃软骨的原始头颅和比无头类简单“人”字形肌节更为复杂的双“人”字形肌节，而且还发育了原始偶鳍和围心腔构造，表明它们已演化成高等脊索动物有头类（Craniata）或称脊椎动物（V ertebrata）。另一方面， 它们的低骨化性（如尚未发育出真正的脊椎骨）和生殖系统演化的滞后性（仍具多对生殖腺）等原始特征，使它们呈现典型的镶嵌演化性。

The Early Cambrian Haikouichthys and Haikouella have been claimed to be related to contribute in an important way to our understanding of vertebrate origin, but there have been heated debates about how exactly they are to be interpreted. New discoveries of numerous specimens of Haikouichthys not only confirm the identity of previously described structures such as the dorsal and the ventral fins, and chevron-shaped myomeres, but also reveal many new important characteristics, including sensory organs of the head (e.g. large eyes), and a prominent notochord with differentiated vertebral elements. This "first fish" appears, however, to retain primitive reproductive features of acraniates, suggesting that it is a stem-group craniates. A new order (Myllokunmingiida) and a new family (Myllokunmingiidae) are erected, and a new species, Zhongjianichthys rostratus (gen. et sp. nov.), is described herein. Over 1400 newly-discovered specimens of Haikouella provide a wealth of anatomical information on this organism. It differs from chordates in many organs and organ systems, including the skin, muscles, respiratory, circulatory and nervous systems. In contrast, its body-design resembles that of vetulicolians, and the presence of a "transitional" nervous system with both dorsal and ventral nerve cords suggests an affinity with living hemichordates. On the basis of these and other recent findings of fossil deuterostomes, a five-step hypothesis for vertebrate origin is proposed, intended to bridge the long-standing gap between protostomes and vertebrates. Four of the five steps accord with established ideas current in modern evolutionary zoology. Evidence for the first step is obtainable only from fossils, and specifically from fossils found from South China, hence the crucial importance of S. China sites for our understanding of early vertebrate origins and evolution. Accordingly, South China is suggested as the oldest-known birthplace of the whole vertebrates.

早寒武世海口鱼和海口虫的发现涉及到脊椎动物起源这一重大论题，近年来引起了热烈的讨论。大量海口鱼新材料不仅证实了原先认识到的背鳍、腹鳍、“之”字形肌节等重要性状，而且还揭示出原始脊椎和头部感官两类关键性特征；这种仍保留无头类原始生殖器官特征的脊椎动物很可能就是有头类始祖。在无颚纲中建立了1个新目昆明鱼目和新科昆明鱼科，描述了一个新属种长吻钟健鱼。新发现的1400余枚海口虫标本提供的多方位解剖学信息显示, 其皮肤、肌肉、呼吸、循环等器官系统与脊索动物明显不同，相反，其躯体构型与古虫类相近，而兼有背、腹神经索的“过渡型”神经系统，与半索动物相一致。基于一系列最早期后口动物新发现，本文提出的脊椎动物起源分“五步走”的假说，在原口动物与脊椎动物之间架起了一座演化桥梁，其中后四步与现代动物谱系分析的“四步走”假说相一致，更增添了关键性的第一步；于是，华南便应该是世界上脊椎动物已知最早的发祥地。

Like the Burgess Shales of Canada, the Chengjiang Lagerstatte from the Lower Cmbrian of China is renowned for the detailed preservation as fossils of delicate, soft-bodied creaturse1-9, pro riding an insight into the Cambrian explosion, The fossils of possible hemichordate chordates5-7 and vertebrates9 have attracted particular attention. Tunicates, or urochordates, comprise the most basal chordate dade10, and details of their evolution could be important in understanding the sequence of character acquisition that led to the emergence of chordates and vertebrates11-15. However, definitive fossils of tunicates from the Cam brian are scarce or debatable4,9,19-24. Here we report a probable tunicate Cheungkongella ancestralis from the Chengjiang fauna. It resembles the extol ascidian tunicate genus Styela whose morphology could be usethl in understanding the origin of the vertebrates.

Exceptional fossil preservation is critical to our understanding of early metazoan evolution. A key source of information is the Burgess Shale-type faunas1-5. Fossils from these deposits provide important insights into metazoan phylogeny, notably that of stem-group protostomes2,3,6, and related topics such as trophic specialization7. Metazoan relationships are also being significantly reappraised in terms of molecular-based phylogenies8,9, but integration of these data with palaeontological systematics is not straightforward10,11. Moreover, molecular phylogenies are silent concerning the anatomies of stem-groups and the functional transitions that underpin the origin of different body plans2,6. Some hitherto enigmatic fossils possess unique character-state combinations that, although they can be shoe-horned into extinct phyla12, may be more profitably interpreted as defining major stem-groups2,3. Here we describe a possible pipiscid, a metazoan previously known only from the Upper Carboniferous13,14, from the Lower Cambrian of south China. Pipiscids are currently interpreted as being agnathan chordates13-15 but this discovery from the Chengjiang fossil-Lagerstaitte indicates that the assignment of pipiscids to the Agnatha deserves to be reconsidered.