A Pikaia-like chordate from the Lower Cambrian of China

  title={A Pikaia-like chordate from the Lower Cambrian of China},
  author={De-gan Shu and Simon Conway Morris and X-L. Zhang},
THE earliest evolution of the chordates and their relationships with other deuterostomes remains controversial1–3. Rejuvenation of interest in the areas of molecular phylogeny4 and developmental genetics5–7 has not been matched by new insights from the fossil record, which for the Lower and Middle Cambrian remains exceptionally sparse. The supposed chordate Emmonsaspis8 has been shown to be a frond-like fossil9, and phosphatic sclerites of hadimopanellids, once compared with vertebrate dermal… 
Lower Cambrian vertebrates from south China
The discovery of two distinct types of agnathan from the Lower Cambrian Chengjiang fossil-Lagerstätte imply that the first agnathans may have evolved in the earliest Cambrian, with the chordates arising from more primitive deuterostomes in Ediacaran times (latest Neoproterozoic, ∼555 Myr BP), if not earlier.
Cambrian Chordates and Vetulicolians
The main objective of this review is to examine the Cambrian diversity of these two deuterostome groups, the chordates and the vetulicolians, which are of particular interest because of the link to vertebrates, andBecause of the enigmatic nature of vetULicolians.
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.
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.
Head and backbone of the Early Cambrian vertebrate Haikouichthys
Phylogenetic analysis indicates that Haikouichthys somewhat resembles the ammocoete larva of modern lampreys, this is because of shared general craniate characters; adult lampreys and hagfishes (the cyclostomes if monophyletic) are probably derived in many respects.
Conodonts, Calcichordates and the Origin of Vertebrates
Soft-part preservation of conodont animals, with V-shaped myomeres and a notochord, shows that they were segmented chordates, while probable eyes and teeth suggest that they was already on the vertebrate side.
Pikaia gracilens Walcott: stem chordate, or already specialized in the Cambrian?
  • J. Mallatt, N. Holland
  • Biology
    Journal of experimental zoology. Part B, Molecular and developmental evolution
  • 2013
A cladistic analysis showed the character interpretations of CMC are consistent with their wide-ranging evolutionary scenario, but that these interpretations leave unresolved the position of Pikaia within chordates.
The early history of the metazoa—a paleontologist’s viewpoint
  • A. Zhuravlev
  • Geography, Environmental Science
    Biology Bulletin Reviews
  • 2015
In the aggregate, modern data from molecular biology, palaeontology, and comparative embryology/morphology, having been revitalized by the introduction of new microscopy techniques, imply that the hypothesized planktotrophic gastrae-like common ancestor is the least likely of the diverse suggestions on the origins of the Metazoa.
A paleontological perspective of vertebrate origin
A five-step hypothesis for vertebrate origin is proposed, intended to bridge the longstanding gap between protostomes and vertebrates, and four of the five steps accord with established ideas current in modern evolutionary zoology.
Chordate evolution and the three-phylum system
It is proposed that an evolutionary occurrence of tadpole-type larvae is fundamental to understanding mechanisms of chordate origin and should be classified at the superphylum level, with the Chordata further subdivided into three phyla, on the basis of their distinctive characteristics.


Reinterpretation of Yunnanozoon as the earliest known hemichordate
Yunnanozoon is reinterpreted here as the earliest known hemichordate, and its typical tripartite body plan is broadly consistent with that of living balanoglossid hemichor-dates (enteropneusts).
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.
Details of the evolutionary history from invertebrates to vertebrates, as deduced from the sequences of 18S rDNA.
  • H. Wada, N. Satoh
  • Biology
    Proceedings of the National Academy of Sciences of the United States of America
  • 1994
Phylogenetic comparisons of the sequences of 18S rDNA suggest the monophyly of the deuterostomes, with the exception of the chaetognaths, and support the hypothesis that chordates evolved from free-living ancestors.
A phylogenetic test of the calcichordate scenario
The calcichordate scenario of Jefferies and colleagues purports to explain the origin and early evolution of the phyla Echinodermata and Chordata is tested, finding that it fails the erection of scenarios and fossils are unable to dictate the relationships among phyla.
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.
The Early Phylogeny of Chordates and Echinoderms and the Origin of Chordate Left–Right Asymmetry and Bilateral Symmetry
The history of the echinoderm stem group is reconstructed and left–right asymmetry in Dexiothetica results mainly from dexiothetism—an episode in their ancestry when an animal resembling the Recent pterobranch Cephalodiscus lay right-side-downwards on the sea floor.
Cambrian Centropleura vermontensis fauna of northwestern Vermont
INTRODUCTION HISTORY OF PREVIOUS WORK So many remarkable fossils have been found in the Cambrian rocks of northwestern Vermont that Franklin County has become classic ground for students of Early
Origin of euconodont elements
The ontogenetic development of the early euconodont elements shows striking similarities to the evolutionary development from paraconodonts to eu ConConmodonts, suggesting that evolution generally followed a peramorphic pattern ("recapitulation").
Conservation of Brachyury (T) genes in amphioxus and vertebrates: developmental and evolutionary implications.
It is proposed that roles of Brachyury in notochord differentiation are more ancient than roles in mesoderm formation, and that the latter are shared by cephalochordates and all vertebrates.
Evidence for Monophyly and Arthropod Affinity of Cambrian Giant Predators
Evidence indicates that anomalocaridids, Opabinia, and Kerygmachela form a monophyletic clade, and for this group an unnamed (sub)phylum-level taxon within an arthropod (super)Phylum is proposed.