Reinterpretation of Yunnanozoon as the earliest known hemichordate

  title={Reinterpretation of Yunnanozoon as the earliest known hemichordate},
  author={De-gan Shu and X. Zhang and L. Chen},
THE Chengjiang fossil Lagerstätte is one of the earliest and most important palaeontological sites from the Phanerozoic era1,2, about 530 million years ago3. It yields extremely abundant and remarkably preserved soft-bodied fossils and shells with soft parts of various kinds, including bradoriids4–6, trilobites7,8, crustaceans9, brachiopods, worms, sponges, algae and many unknown forms10–13. One of these fossils is Yunnanozoon14, which we reinterpret here as the earliest known hemichordate… 
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There is strong molecular evidence to indicate that lophophorates are very distant from hemichordates and echinoderms, in a different major branch of the animal phylogenetic tree, and there is weaker evidence that pterobranchs may be derived from acorn worms, and hence that the vermiform body plan may be ancestral within hemicordates.
A Pikaia-like chordate from the Lower Cambrian of China
A single specimen of a Lower Cambrian chordate, Cathaymyrus diadexus, new genus and species, that is similar to Pikaia but predates it by about 10 million years (Myr).
A pipiscid-like fossil from the Lower Cambrian of south China
A possible pipiscid, a metazoan previously known only from the Upper Carboniferous, is described from the Lower Cambrian of south China, and this discovery from the Chengjiang fossil-Lagerstätte indicates that the assignment of pipiscids to the Agnatha deserves to be reconsidered.
New data on the palaeobiology of the enigmatic yunnanozoans from the Chengjiang Biota, Lower Cambrian, China
This analysis reveals new details of the putative pharyngeal pores of Yunnanozoon lividum, and although there are similarities with the gill slits of deuterostomes, the question of their homology remains moot.
On the Phylum Vetulicolia
Since all vetulicolians share similar characters in their anterior section (pharynx), and on the basis of differences in their posterior section, a new classification system is proposed, with a new class, the Heteromorphida erected.
New sites of Chengjiang fossils: crucial windows on the Cambrian explosion
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The earliest history of the deuterostomes: the importance of the Chengjiang Fossil-Lagerstätte
The known diversity of Chengjiang deuterostomes are reviewed and it is argued that the vetulicolians and yunnanozoans represent very primitive deuterOSTomes, as well as new data to indicate that the yunncozoans are unlikely to be any sort of chordate.
Tentaculate Fossils from the Cambrian of Canada (British Columbia) and China (Yunnan) Interpreted as Primitive Deuterostomes
The evidence is suggested that the evidence is more consistent with the ambulacraria being primitive deuterostomes, with specific comparisons being made to the pterobranch hemichordates and pre-radial echinoderms.


Rhabdotubus, a Middle Cambrian rhabdopleurid hemichordate
Rhabdotubus is interpreted as the earnest known rhabdopleurid (Class Pterobranchia, Phylum Hemichordata), which may well have phylogenetic significance, but further knowledge of the Tuboidea and other sessile orders of the Graptolithina is required to clarify the early evolution of graptolites.
Composition and preservation of the Chengjiang fauna –a Lower Cambrian soft‐bodied biota
The Lower Cambrian Chengjiang fauna is reviewed and shown to be closely comparable with the younger Burgess Shale fauna. but with various differences in detail. A diverse group of more or less
Decay of Branchiostoma: implications for soft‐tissue preservation in conodonts and other primitive chordates
Decay experiments on the cephalochordate Branchiostoma lanceolatum (‘amphioxus’) demonstrate that the most decay resistant structures are the notochord sheath and the cartilaginous rods which support the gill bars, and cast light on the interpretation of a number of primitive fossil chordates.
A possible Early Cambrian chordate
The first chordate recorded from the Early Cambrian is the ceph-alochordate Yunnanozoon lividum from the 525 million-year-old Chengjiang fauna and predicts that other chordate clades (tunicates and craniates) had evolved by the Late Atdabanian, in the main burst of the Cambrian Explosion.
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New morphological evidence and homology analyses for several characters indicate an anteroposterior reversal of Hallucigenia and Microdictyon, and the taxonomic confusion surrounding the supposed radiolarian family Eoconchariidae is cleared.
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Soft parts of Isoxys auritus, such as antennae, biramous limbs, eyes, mouth, stomach and adductor muscle scars, have been discovered in material from the Early Cambrian Chengjiang fossil Lagerstatte
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The appearance of the multicellular animals, or Metazoa, in the fossil record about 600 million years ago marks a revolution in the history of life, and data on rapidly radiating animal groups place early metazoan evolution in a new perspective.
Invertebrates: a new synthesis.
Invertebrates with legs: the arthropods and similar groups, and the evolutionary history and phylogeny of the invertebrates, are studied.