A critical reappraisal of the fossil record of the bilaterian phyla

Biological Reviews

Volumn 75, Issue 2, 2000, Pages 253-295

  Budd, Graham E ^a   Jensen, SÖREN ^b  

^a UPPSALA UNIVERSITY   (Sweden)

^b UNIVERSITY OF CAMBRIDGE   (United Kingdom)

Author keywords

Bilateria; Body size; Cambrian; Functional morphology; Molecular clocks; Origins; Phyla; Planktotrophy; Stem groups; Trace fossils

Indexed keywords

EVOLUTION; FOSSIL; GEOLOGY; MORPHOLOGY; NONHUMAN; PHYLOGENY; PRESERVATION; REVIEW; TAXONOMY;

EID: 0034081946     PISSN: 14647931     EISSN: 1469185X     Source Type: Journal    
DOI: 10.1111/j.1469-185X.1999.tb00046.x     Document Type: Article

References (278)

1. Abele, L. G., Kim, W. & Felgenhauer, B. E. (1989). Molecular evidence for the inclusion of the phylum Pentastomida in the Crustacea. Molecular Biology and Evolution 6, 685–691.
2. Adoutte, A., Balavoine, G., Lartillot, N. & de Rosa, R. (1999). Animal evolution: The end of the intermediate taxa Trends In Genetics 15, 104–108.
3. Aguinaldo, A. M. A., Turbeville, J. M., Linford, L. S., Rivera, M. C., Garey, J. R., Raff, R. A. & Lake, J. A. (1997). Evidence for a clade of nematodes, arthropods and other moulting animals. Nature 387, 489–493.
4. Arthur, W. (1997). The Origin of Animal Body Plans: A Study in Evolutionary Developmental Biology. Cambridge University Press, Cambridge, UK.
5. Atkinson, H. J. (1980). Respiration in nematodes. In Nematodes as Biological models, vol. 2 (ed. B. N. Zuckerman), pp. 101–142. Academic Press, New York.
6. Ausich, W. I. & Babcock, L. C. (1998). The phylogenetic position of Echmatocrinus brachiatus, a probable octocoral from the Burgess Shale. Palaeontology 41, 193–202.
7. Ax, P. (1985). The position of the Gnathostomulida and Platyhelminthes in the phylogenetic system of the Bilateria. In The Origins and Relationships of Lower Invertebrates (ed. S. Conway Morris, J. D. George, R. Gibson and H. M. Platt), pp. 168–199. Oxford University Press, Oxford.
8. Ayala, F. J. (1999). Molecular clock mirages. BioEssays 21, 71–75.
9. Ayala, F. J. & Rzhetsky, A. (1998). Origin of the metazoan phyla: Molecular clocks confirm paleontological estimates. Proceedings of the National Academy of Sciences, USA 95, 606–611.
10. Balavoine, G. & Adoutte, A. (1998). One or three Cambrian radiations Science 280, 397–398.
11. Bengtson, S. & Urbanek, A. (1986). Rhabdotubus new genus, a middle Cambrian rhabdopleurid hemichordate. Lethaia 19, 293–308.
12. Benton, M. J. (1993). The Fossil Record 2. Chapman & Hall, London.
13. Berg, G. (1985). Annulonemertes gen. nov., a new segmented hoplonemertean. In The Origins and Relationships of Lower Invertebrates (ed. S. Conway Morris, J. D. George, R. Gibson and H. M. Platt), pp. 200–209. Clarendon Press, Oxford.
14. Bergström, J. (1997). Origin of high-rank groups of organisms. Palaeontological Research 1, 1–14.
15. Bergström, J., Naumann, W. W., Viehweg, J. & Marti Mus, M. (1998). Conodonts, calcichordates and the origin of vertebrates. Mitteilungen aus dem Museum für Naturkunde in Berlin, Reihe Geowissenschaften 1, 81–92.
16. Boaden, P. J. S. (1989). Meiofauna and the origin of the Metazoa. Zoological Journal of the Linnean Society of London 96, 217–227.
17. Boxshall, G. (1997). Comparative limb morphology in major crustacean groups: The coxa-basis joint in postmandibular limbs. In Arthropod Relationships (ed. R. A. Fortey and R. H. Thomas), pp. 155–167. Chapman & Hall, London.
18. Brasier, M. (1998). Animal evolution — From deep time to late arrivals. Nature 395, 547–548.
19. Brasier, M. D. & McIlroy, D. (1998). Neonereites uniserialis from c. 600 Ma year old rocks in western Scotland and the emergence of animals. Journal of the Geological Society of London 155, 5–12.
20. Bridge, D., Cunningham, C. W., Schierwater, B. & de Salle, R. (1992). Class-level relationships in the phylum Cnidaria: Evidence from mitochondrial genome structure. Proceedings of the National Academy of Sciences, USA 89, 8750–8753.
21. Briggs, D. E. G. (1978). The morphology, mode of life, and affinities of Canadaspis perfecta (Crustacea, Phyllopoda), Middle Cambrian, Burgess Shale, British Columbia. Philosophical Transactions of the Royal Society of London B 281, 439–487.
22. Briggs, D. E. G. (1992). Phylogenetic significance of the Burgess Shale crustacean Canadaspis. Acta Zoologica (Stockholm) 73, 293–300.
23. Briggs, D. E. G. & Collins, D. (1988). A Middle Cambrian chelicerate from Mount Stephen, British Columbia (Canada). Palaeontology 31, 779–798.
24. Bromham, L., Rambaut, A., Fortey, R. A., Cooper, A. & Penny, D. (1998). Testing the Cambrian explosion hypothesis by using molecular dating technique. Proceedings of the National Academy of Sciences, USA 95, 12386–12389.
25. Bromley, R. G. (1996). Trace Fossils: Biology, Taphonomy and Applications. Chapman & Hall, London.
26. Brower, A. V. Z. & Schawaroch, V. (1996). Three steps of homology assessment. Cladistics 12, 265–272.
27. Bryant, C. (ed.) (1991). Metazoan Life without Oxygen. Chapman & Hall, London.
28. Budd, G. E. (1996). The morphology of Opabinia regalis and the reconstruction of the arthropod stem-group. Lethaia 29, 1–14.
29. Budd, G. E. (1997). Stem group arthropods from the Lower Cambrian Sirius Passet fauna of North Greenland. In Arthropod Relationships (ed. R. A. Fortey and R. H. Thomas), pp. 125–138. Chapman & Hall, London.
30. Budd, G. E. (1998a). Arthropod body plan evolution in the Cambrian, with an example from anomalocaridid muscle. Lethaia 31, 197–210.
31. Budd, G. E. (1998b). Bonnet's challenge. Lethaia 31, 167–168.
32. Budd, G. E. (1999a). The morphology and phylogenetic significance of Kerygmachela kierkegaardi Budd (Buen Formation, Lower Cambrian, North Greenland). Transactions of the Royal Society of Edinburgh: Earth Sciences 89, 249–290.
33. Budd, G. E. (1999b). Does evolution in body patterning genes drive morphological change — or vice versa BioEssays 21, 326–332.
34. Buss, L.W. & Seilacher, A. (1994). The Phylum Vendobionta: A sister group of the Eumetazoa. Paleobiology 20, 1–4.
35. Butterfield, N. J. (1997). Plankton ecology and the Proterozoic-Phanerozoic transition. Paleobiology 23, 247–262.
36. Canfield, D. E. & Teske, A. (1996). Late Proterozoic rise in atmospheric oxygen concentration inferred from phylogenetic and sulphur-isotope studies. Nature 382, 127–132.
37. Chen, J. Y., Dzik, J., Edgecombe, G. D., Ramskold, L. & Zhou, G. Q. (1995). A possible Early Cambrian chordate. Nature 377, 720–722.
38. Chuang, S. H. (1991). Common and evolutionary features of recent brachiopods and their bearing on the relationships between, and the monophyletic origin of, the inarticulates and the articulates. In Brachiopods Through Time, Proceedings of the 2nd International Brachiopod Congress, University of Otago, Dunedin, New Zealand, 1990 (ed. D. I. MacKinnon, D. E. Lee and J. D. Campbell), pp. 11–14. A. A. Balkema, Rotterdam.
39. Clark, R. B. (1964). Dynamics in Metazoan Evolution. Clarendon Press, Oxford.
40. Cloud, P. (1968). Pre-metazoan evolution and the origins of the Metazoa. In Evolution and Environment (ed. E. T. Drake), pp. 1–72. Yale University Press, New Haven.
41. Cloud, P. (1976). Beginnings of biosphere evolution and their biogeochemical consequences. Paleobiology 2, 351–387.
42. Cohen, B. L. & Gawthorp, A. B. (1997). The brachiopod genome. In Treatise on Invertebrate Paleontology, Part H, revised Brachiopoda (ed. R. L. Kaesler), pp. 189–211. The Geological Society of America and the University of Kansas, Boulder and Lawrence.
43. Conklin, E. G. (1932). The embryology of Amphioxus. Journal of Morphology 54, 69–118.
44. Conway Morris, J. & Chen, M. (1991). Cambroclaves and paracarinachitids, early skeletal problematica from the Lower Cambrian of South China. Palaeontology 34, 357–397.
45. Conway Morris, S. (1977). Fossil priapulid worms. Special Papers in Palaeontology 20, 1–95.
46. Conway Morris, S. (1979). Middle Cambrian polychaetes from the Burgess Shale of British Columbia. Philosophical Transactions of the Royal Society of London B 285, 227–274.
47. Conway Morris, S. (1986). The community structure of the Middle Cambrian phyllopod bed (Burgess Shale). Palaeontology 29, 423–467.
48. Conway Morris, S. (1993). The fossil record and the early evolution of the Metazoa. Nature 361, 219–225.
49. Conway Morris, S. (1997). Molecular clocks: Defusing the Cambrian ‘explosion’ Current Biology 7, 71–74.
50. Conway Morris, S. (1998a). Early metazoan evolution: Reconciling palaeontology and molecular data. American Zoologist 38, 867–877.
51. Conway Morris, S. (1998b). Eggs and embryos from the Cambrian. BioEssays 20, 676–682.
52. Conway Morris, S. (1998c). The Crucible of Creation. Oxford University Press, Oxford.
53. Conway Morris, S. & Peel, J. S. (1995). Articulated halkieriids from the Lower Cambrian of North Greenland and their role in early protostome evolution. Philosophical Transactions of the Royal Society of London B 347, 305–358.
54. Cooper, A. & Fortey, R. A. (1998). Evolutionary explosions and the phylogenetic fuse. Trends in Ecology and Evolution 13, 151–156.
55. Crimes, T. P. (1987). Trace fossils and correlation of late Precambrian and early Cambrian strata. Geological Magazine 124, 97–119.
56. Crimes, T. P. (1994). The period of evolutionary failure and the dawn of evolutionary success: The record of biotic changes across the Precambrian-Cambrian boundary. In The Palaeobiology of Trace Fossils (ed. S. K. Donovan), pp. 105–133. John Wiley & Sons, Chichester.
57. Dahl, E. (1984). The subclass Phyllocarida (Crustacea) and the status of some early fossils: A neontologist view. Videnskabelige Meddelelser fra Dansk naturhistorisk Forening 145, 61–76.
58. David, B. & Mooi, R. (1996). Embryology supports a new theory of skeletal homologies for the phylum Echinodermata. Comptes rendus de l'Académie des Sciences, Paris, Sciences de la vie/Life Sciences 319, 577–584.
59. Davidek, K., Landing, E., Bowring, S. A., Westrop, S. B., Rushton, A. W. A., Fortey, R. A. & Adrain, J. M. (1998). New uppermost Cambrian U-Pb date from Avalonian Wales and the age of the Cambrian-Ordovician boundary. Geological Magazine 135, 303–309.
60. Davidson, E. H. (1991). Spatial mechanisms of gene regulation in metazoan embryos. Development 113, 1–26.
61. Davidson, E. H., Peterson, K. J. & Cameron, R. A. (1995). Origin of bilaterian body plans — evolution of developmental regulatory mechanisms. Science 270, 1319–1325.
62. de Pinna, M. C. C. (1991). Concepts and tests of homology in the cladistic paradigm. Cladistics 7, 367–394.
63. de Robertis, E. M. (1997). The ancestry of segmentation. Nature 387, 25–26.
64. Donoghue, P. C. J., Purnell, M. A. & Aldridge, R. J. (1998). Conodont anatomy, chordate phylogeny and vertebrate classification. Lethaia 31, 211–219.
65. Droser, M. L., Fortey, R. A. & Li, X. (1996). The Ordovican radiation. American Scientist 84, 122–131.
66. Droser, M. L., Gehling, J. G. & Jensen, S. (1999). When the worm turned: Concordance of early Cambrian ichnofabric and trace fossil record in siliciclastics of South Australia. Geology 27, 625–628.
67. Dunlop, J. A. & Selden, P. A. (1997). The early history and phylogeny of the chelicerates. In Arthropod Relationships (ed. R. A. Fortey and R. H. Thomas), pp. 221–235. Chapman & Hall, London.
68. Durham, J. W. (1978). A lower Cambrian eocrinoid. Journal of Paleontology 52, 195–199.
69. Durman, P. N. & Sennikov, N. V. (1993). A new rhabdopleurid hemichordate from the Middle Cambrian of Siberia. Palaeontology 36, 283–296.
70. Dzik, J. (1995). Yunnanozoon and the ancestry of chordates. Acta Palaeotologica Polonica 40, 341–360.
71. Dzik, J. (1999). Organic membranous skeleton of the Precambrian metazoans from Namibia. Geology 27, 519–522.
72. Dzik, J. & Lendzion, K. (1988). The oldest arthropods of the East European platform. Lethaia 21, 29–38.
73. Edgecombe, G.D. & Ramsköld, L. (1999). Relationships of Cambrian Arachnata and the systematic position of Trilobita. Journal of Paleontology 73, 263–287.
74. Edlinger, K. (1991). The mechanical constraints in mollusc constructions - the function of the shell, the musculature, and the connective tissue. In Constructional Morphology and Evolution (ed. N. Schmidt-Kittler and K. Vogel), pp. 359–374. Springer-Verlag, Berlin.
75. Edlinger, K. (1998). Konstruktionsprobleme der Miniaturisierung im Tierreich. Zur Unumkehrbarkeit konstruktiven Wandels. Natur und Museum 128, 139–151.
76. Edlinger, K. & Gutmann, W. F. (1997). Molluscs as evolving constructions: Necessary aspects for a discussion of their phylogeny. Iberus 15, 51–66.
77. Ehlers, U. (1985). Das Phylogenetische System der Plathelminthes. Gustav Fischer, Stuttgart.
78. Eibye-Jacobsen, J. (1997). New observations on the embryology of the Tardigrada. Zoologischer Anzeiger 235, 201–216.
79. Erwin, D. H. (1993). Early introduction of major morphological innovations. Acta Palaeontologica Polonica 38, 281–294.
80. Erwin, D. H. (1999). The origin of bodyplans. American Zoologist 39, 617–629.
81. Erwin, D. H., Valentine, J. W. & Jablonski, D. (1997). The origin of animal body plans. American Scientist 85, 126–137.
82. Fedonkin, M. A. (1983). Besskeletnaya fauna podol'skogo pridnestrov'ya [Non-skeletal fauna of Podolia (Dniestr River Vally).]. In Vend Ukrainy (ed. V. A. Velikanov, M. A. Aseeva and M. A. Fedonkin), pp. 128–139. Naukova Dumka, Kiev.
83. Fedonkin, M. A. (1990). Precambrian Metazoans. In Palaeobiology. A Synthesis (ed. D. E. G. Briggs and P. R. Crowther), pp. 17–24. Blackwell Scientific Publications, Oxford.
84. Fedonkin, M. A. (1992). Vendian faunas and the early evolution of Metazoa. In Origin and early evolution of the Metazoa (ed. J. H. Lipps and P. W. Signor), pp. 87–129. Plenum Press, New York & London.
85. Fedonkin, M. A. & Runnegar, B. N. (1992). Proterozoic metazoan trace fossils. In The Proterozoic Biosphere: A Multidisciplinary Study (ed. J. W. Schopf and C. Klein), pp. 389–395. Cambridge University Press, Cambridge.
86. Fedonkin, M. A. & Wagonner, B. M. (1997). The Late Precambrian fossil Kimberella is a mollusc-like bilaterian organism. Nature 388, 869–871.
87. Fenton, M. A. & Fenton, C. L. (1934). Scolithus as a fossil phoronid. Pan-American Geologist 61, 341–348.
88. Fortey, R. A., Briggs, D. E. G. & Wills, M. A. (1996). The Cambrian evolutionary ‘explosion’: Decoupling cladogenesis from morphological disparity. Biological Journal of the Linnean Society 57, 13–33.
89. Fortey, R. A., Briggs, D. E. G. & Wills, M. A. (1997). The Cambrian ‘explosion’ recalibrated. BioEssays 19, 429–434.
90. Fortey, R. A. & Owens. (1990). Evolutionary radiations in the Trilobita. In Major Evolutionary Radiations (ed. P. D. Taylor and G. P. Larwood), pp. 139–164. Clarendon Press, Oxford.
91. Ganfornina, M. D. & Sanchez, D. (1999). Generation of evolutionary novelty by functional shift. BioEssays 21, 432–439.
92. Gee, H. (1996). Before the Backbone (Views on the Origin Chordates). Chapman & Hall, London.
93. Gehling, J. G. (1987). Earliest known echinoderm; a new Ediacaran fossil from the Pound Subgroup of South Australia. Alcheringa 11, 337–345.
94. Gehling, J. G. (1991). The case for Ediacaran roots to the metazoan tree. Geological Society of India Memoir 20, 181–224.
95. Gehling, J. G. (1999). Microbial mats in Terminal Proterozoic siliciclastics: Ediacaran death masks. Palaios 14, 40–57.
96. Gehling, J. G., Narbonne, G. M., Jensen, S. & Droser, M. L. (1999). Simultaneous appearance of Ediacaran trace fossils and bilateral body fossils: Implications for animal evolution. Geological Society of America, Abstracts with Programs 31(7), A362.
97. Gellon, G. & McGinnis, W. (1998). Shaping animal body plans in development and evolution by modulation of Hox expression patterns. BioEssays 20, 116–125.
98. Gerhart, J. & Kirschner, M. (1997). Cells, Embryos and Evolution: Towards a Cellular and Developmental Understanding Phenotypic Variation and Evolutionary Adaptability. Blackwell Sciences, Malden, USA.
99. Geyer, G. & Streng, M. (1998). Middle Cambrian pelecypods from the Anti-Atlas, Morocco. Revista Espanola de Paleontologia No. extr. Homenajae al Prof. Gonzalo Vidal, 83–96.
100. Glaessner, M. (1984). The Dawn of Animal Life — a Biohistorical Study. Cambridge University Press, Cambridge
101. Glaessner, M. F. & Wade, M. (1966). The late Precambrian fossils from Ediacara, South Australia. Palaeontology 9, 599–628.
102. Glaessner, M. F. & Wade, M. (1971). Praecambridium - a primitive arthropod. Lethaia 4, 71–77.
103. Goldring, R. & Seilacher, A. (1971). Limulid undertracks, and their sedimentological implications. Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen 137, 422–442.
104. Golikov, A. N. & Starobogatov, Y. I. (1975). Systematics of prosobranch gastropods. Malacologia 15, 185–232.
105. Goloboff, P. A. (1997). Self-weighted optimization: Tree searches and character state reconstructions under implied transformation costs. Cladistics 13, 225–245.
106. Gould, S. J. (1989). Wonderful Life: The Burgess Shale and the Nature of History. W. W. Norton, New York.
107. Green, A. S. & Chandler, T. (1994). Meiofaunal bioturbation effects on the partitioning of sediment-associated cadmium. Journal of Experimental Marine Biology and Ecology 180, 59–70.
108. Hagadorn, J. W. & Bottjer, D. J. (1999). Restriction of a late Neoproterozoic biotope: Suspected microbial structures and trace fossils at the Vendian-Cambrian transition. Palaios 14, 73–85.
109. Halanych, K. M. (1995). The phylogenetic position of the pterobranch hemichordates based on 18S DNA sequence data. Molecular Phylogenetics and Evolution 4, 72–76.
110. Halanych, K. M. (1996). Testing hypotheses of Chaetognath origins: Long branches revealed by 18S ribosomal DNA. Systematic Biology 45, 223–246.
111. Halanych, K. M., Bacheller, J. D., Aguinaldo, A. M. A., Liva, S. M., Hillis, D. M. & Lake, J. A. (1995). Evidence from 18S ribosomal DNA that the lophophorates are protostome animals. Science 267, 1641–1643.
112. Hammen, C. S. (1991). Anoxibiosis in living Metazoa: An overview. In Metazoan Life Without Oxygen (ed. C. Bryant), pp. 271–278. Chapman & Hall, London.
113. Hanken, J. & Wake, D. B. (1993). Miniaturization of body size: Organismal consequences and evolutionary significance. Annual Review of Ecology and Systematics 24, 501–519.
114. Harper, E. M. (1998). The fossil record of bivalve molluscs. In The Adequacy of the Fossil Record (ed. S. K. Donovan & C. R. C. Paul), pp. 243–267. Wiley, Chichester.
115. Haszprunar, G. (1988). On the origin and evolution of major gastropod groups, with special reference to the Streptoneura. Journal of Molluscan Studies 54, 367–441.
116. Haszprunar, G. (1996). The Mollusca: Coelomate turbellarians or mesenchymate annelids? In Origin and Evolutionary Radiation of the Mollusca (ed. J. Taylor), pp. 1–28. Oxford University Press, Oxford.
117. Haszprunar, G., Salvini-Plawen, L. V. & Rieger, R.M. (1995). Larval planktotrophy - a primitive trait in the Bilateria Acta Zoologica (Stockholm) 76, 141–154.
118. Hawkins, J. A., Hughes, C.E. & Scotland, R. W. (1997). Primary homology assessment, characters and character states. Cladistics 13, 275–283.
119. Hertweck, G. (1972). Georgia coastal region, Sapelo Island, USA: Sedimentology and biology. V. Distribution and environmental significance of lebenspuren and in-situ skeletal remains. Senckenbergiana Maritima 4, 125–167.
120. Hinz, I. (1987). The Lower Cambrian microfauna of Comley and Rushton, Shropshire/England. Palaeontographica A 198, 41–100.
121. Hochachka, P. W. S. & Somero, G. N. (1973). Strategies of biochemical adaptation. W. B. Saunders, Philadelphia.
122. Holmer, L. E. & Popov, L. E. (1996). Early Palaeozoic radiation and classification of organo-phosphatic brachiopods. In Brachiopods (ed. P. Copper and J. Jin), pp. 117–121. A. A. Balkema, Rotterdam.
123. Hou, X. & Bergström, J. (1994). Palaeoscolecid worms may be nematomorphs rather than annelids. Lethaia 27, 11–17.
124. Hou, X. & Bergström, J. (1997). Arthropods of the Lower Cambrian Chengjiang fauna, southwest China. Fossils & Strata 45, 1–116.
125. Hou, X., Ramsköld, L. & Bergström, J. (1991). Composition and preservation of the Chengjiang fauna - a Lower Cambrian soft-bodied biota. Zoologica Scripta 20, 395–411.
126. Hou, X., Siveter, D. J., Williams, M., Walossek, D. & Bergström, J. (1996). Appendages of the arthropod Kunmingella from the early Cambrian of China: Its bearing on the systematic position of the Bradoriida and the fossil record of the Ostracoda. Philosophical Transactions of the Royal Society of London B 351, 1131–1145.
127. Hyman, L. H. (1959). The Invertebrates: Vol. V. Smaller Coelomate Groups. McGraw-Hill, New York.
128. Israelsson, O. (1997). …and molluscan embryogenesis. Nature 390, 32.
129. Israelsson, O. (1999). New light on the enigmatic Xenoturbella (phylum uncertain): Ontogeny and phylogeny. Proceedings of the Royal Society of London B 266, 835–841.
130. Jaanusson, V. (1981). Functional thresholds in evolutionary progress. Lethaia 14, 251–260.
131. Jacobs, D. K., Lee, S. E., Dawson, M. N., Staton, J. L. & Raskoff, K. A. (1998). The history of development through the evolution of molecules: Gene trees, hearts, eyes and dorsoventral inversion. In Molecular Approaches to Ecology and Evolution (ed. R. de Salle and B. Schierwater), pp. 323–356. Birkhauser Verlag, Basel.
132. Jägersten, G. (1972). Evolution of the Metazoan Life Cycle. Academic Press, London.
133. Janvier̈ P. (1999). Catching the first fish. Nature 402, 21–22.
134. Jefferies, R. P. S. (1979). The origin of chordates - a methodological essay. In The Origin of the Major Invertebrate Groups (ed. M. R. House), pp. 443–477. Academic Press, London.
135. Jenkins, R. J. F. (1996). Aspects of the geological setting and paleobiology of the Ediacara assemblage. In Natural History of the Flinders Ranges (ed. M. Davies, C. R. Twidale and M. J. Tyler), pp. 33–45. Royal Society of South Australia., Richmond.
136. Jenner, R. A. & Schram, F. R. (1999). The grand game of metazoan phylogeny: Rules and strategies. Biological Reviews 74, 121–142.
137. Jensen, P. (1992). Cerianthus vogti Danielssen, 1890 (Anthozoa: Ceriantharia). A species inhabiting extended tube systems deeply buried in deep-sea sediments off Norway. Sarsia 77, 75–80.
138. Jensen, S. (1997). Trace fossils from the Lower Cambrian Mickwitzia sandstone, south-central Sweden. Fossils & Strata 42, 1–111.
139. Jensen, S., Gehling, J. G., Runnegar, B. N. & Droser, M. L. (1999). Trace fossils and bioturbation in the Proterozoic. Journal of Conference Abstracts, 4, 264–265.
140. Jensen, S., Saylor, B. Z., Gehling, J. G. & Germs, G. J. B. (in press). Complex trace fossils from the terminal Proterozoic of Namibia. Geology 28.
141. Kasting, J. F. (1991). Box models for the evolution of atmospheric oxygen - an update. Global and Planetary Change 97, 125–131.
142. Kemp, T. S. (1982). Mammal-like Reptiles and the Origin of Mammals. Academic Press, London.
143. Kemp, T. S. (1985). Synapsid reptiles and the origin of higher taxa. Special Papers in Palaeontology 33, 175–184.
144. Kemp, T. S. (1988). Haemothermia or Archosauria? The interrelationships of mammals, birds, and crocodiles. Zoological Journal of the Linnean Society, London 92, 67–104.
145. Kennedy, M. J., Runnegar, B., Prave, A. N., Hoffmann, K.-H. & Arthur, M. A. (1998). Two or four Neoproterozoic glaciations Geology 26, 1059–1063.
146. Kimmel, C. B., Ballard, W. W., Kimmel, S. R., Ullmann, B. & Schilling, T. F. (1995). Stages of embryonic development of the zebrafish. Developmental Dynamics 203, 253–310.
147. Knoll, A. H. (1996). Daughter of time. Paleobiology 22, 1–7.
148. Knoll, A. H. & Carroll, S. B. (1999). Early animal evolution: Emerging views from comparative biology and geology. Science 284, 2129–2137.
149. La Barbera, M. & Vogel, S. (1982). The design of fluid transport systems in organisms. American Scientist 70, 54–60.
150. Lacalli, T. C. (1999). Tunicate tails, stolons, and the origin of the vertebrate trunk. Biological Reviews 74, 177–198.
151. Landing, E., Bowring, S. A., Davidek, K. L., Westrop, S. R., Geyer, G. & Heidemaier, W. (1998). Duration of the Early Cambrian; U-Pb ages of volcanic ashes from Avalon and Gondwana. Canadian Journal of Earth Sciences 35, 329–338.
152. Lee, M.-S.-Y. & Doughty, P. (1997). The relationship between evolutionary theory and phylogenetic analysis. Biological Reviews 72, 471–495.
153. Lieberman, B. S. (1998). Cladistic analysis of the early Cambrian Olenelloid trilobites. Journal of Paleontology 72, 59–78.
154. Lieberman, B. S. (1999). Testing the Darwinian legacy of the Cambrian radiation using trilobite phylogeny and biogeography. Journal of Paleontology 73, 176–182.
155. Long, J. A. & Stricker, S. A. (1991). Brachiopoda. In Reproduction of Marine Invertebrates, Vol. 6 (ed. A. Geise, J. S. Pearse and V. B. Pearse), pp. 47–84. Blackwell Scientific, Malden.
156. Lynch, M. (1999). The age and relationships of the major animal phyla. Evolution 53, 319–325.
157. McHugh, D. (1997). Molecular evidence that echiurans and pogonophorans are derived annelids. Proceedings of the National Academy of Science, USA 94, 8006–8009.
158. McIlroy, D. & Logan, G. A. (1999). The impact of bioturbation on infaunal ecology and evolution during the Proterozoic-Cambrian transition. Palaois 14, 58–72.
159. Mooi, R., David, B., Marchand, D. (1994). Echinoderm skeletal morphologies: Classical morphology meets modern phylogenetics. In Echinoderms Through Time (ed. B. David, A. Guille, J. P. Féral, M. Roux,), pp. 87–95. Balkema, Rotterdam.
160. Moore, J. & Willmer, P. (1997). Convergent evolution in invertebrates. Biological Reviews 72, 1–60.
161. Narbonne, G. M. (1998). The Ediacara biota; a terminal Neoproterozoic experiment in the evolution of life. GSA Today 8(2), 1–6.
162. Narbonne, G. M. & Aitken, J. D. (1990). Ediacaran fossils from the Sekwi Brook area, Mackenzie mountains, Northwestern Canada. Palaeontology 33, 945–980.
163. Narbonne, G. M., Myrow, P. M., Landing, E. & Anderson, M. M. (1987). A candidate stratotype for the Precambrian- Cambrian boundary, Fortune Head, Burin Peninsula, south- eastern Newfoundland (Canada). Canadian Journal of Earth Sciences 24, 1277–1293.
164. Nichols, D. (1972). The water-vascular system in living and fossil echinoderms. Palaeontology 15, 519–538.
165. Nielsen, C. (1991). The development of the brachiopod Crania (Neocrania) anomala (O. F. Müller) and its phylogenetic significance. Acta Zoologica (Stockholm) 72, 7–28.
166. Nielsen, C. (1995). Animal Evolution: Interrelationships of the Living Phyla. Oxford University Press, Oxford.
167. Nielsen, C. & Nørrevang, A. (1985). The trochaea theory: An example of life cycle phylogeny. In The Origins and Relationships of Lower Invertebrates (ed. S. Conway Morris, J. D. George, R. Gibson and H. M. Platt), pp. 28–41. Oxford University Press, Oxford.
168. Norén, M. & Jondelius, U. (1997). Xenoturbella's molluscan relatives. Nature 390, 31–32.
169. Nursall, J. R. (1959). Oxygen as a prerequisite to the origin of the Metazoa. Nature 183, 1170–1172.
170. O'Brien, N. R. (1987). The effects of bioturbation on the fabric of shale. Journal of Sedimentary Petrology 57, 449–455.
171. Olive, P. J. W. (1985). Covariability of reproductive traits in marine invertebrates: Implications for the phylogeny of the lower invertebrates. In The Origins and Relationships of Lower Invertebrates (ed. S. Conway Morris, J. D. George, R. Gibson and H. M. Platt), pp. 42–59. Oxford University Press, Oxford.
172. Ott, J. & Schiemer, F. (1973). Respiration and anaerobiosis of free-living nematodes from marine and limnic sediments. Netherlands Journal of Sea Research 1, 233–243.
173. Paterson, D. M. (1994). Microbiological mediation of sediment structure and behaviour. In Microbial Mats (ed. L. J. Stal and P. Caumette), pp. 97–109. Springer-Verlag, Berlin.
174. Patterson, C. (1988). Homology in classical and molecular biology. Molecular Biology and Evolution 5, 603–625.
175. Peel, J. S. (1991a). Functional morphology of the Class Helcionelloida nov., and the early evolution of the Mollusca. In The Early Evolution of Metazoa and the Significance of Problematic Taxa. (ed. A. M. Simonetta and S. Conway Morris), pp. 157–175. Cambridge University Press, Cambridge.
176. Peel, J. S. (1991b). The Classes Tergomya and Helcionelloida, and early molluscan evolution. Bulletin Grønlands geologiske Undersøgelse 161, 11–65.
177. Peel, J. S. & Horny, R. J. (1999). Muscle scars and systematic position of the Lower Palaeozoic limpets Archinacella and Barrandicella gen. n. (Mollusca). Journal of the Czech Geological Society 44, 97–115.
178. Pelman, Y. L. (1977). Ranne i srednekembriiskjie bezzamkovje brakhiopody Sibirskoy Platformy [Early and Middle Cambrian inarticulate brachiopods of the Siberian Platform]. Trudy Instituta Geologii geofiziki Sibirskogo Otdelenjia 36, 1–168.
179. Peterson, K. J., Cameron, A. & Davidson, E. H. (1997). Setaside cells in maximal indirect development: Evolutionary and developmental significance. BioEssays 19, 623–631.
180. Peterson, K. J., Cameron, R. A., Tagawa, K., Satoh, N. & Davidson, E. H. (1999). A comparative molecular approach to mesodermal patterning in basal deuterostomes: The expression pattern of Brachyury in the enteropneust hemichordate Ptychodera flava. Development 126, 85–95.
181. Pflüger, F. P. & Gresse, P. (1996). Microbial sand chips - a non-actualistic sedimentary structure. Sedimentary Geology 102, 263–274.
182. Qian, Y. & Bengtson, S. (1989). Palaeontology and biostratigraphy of the Early Cambrian Meishucunian Stage in Yunnan Province, South China. Fossils & Strata 24, 1–156.
183. Raff, R. A. & Raff, E. C. (1970). Respiratory mechanisms and the metazoan fossil record. Nature 228, 1003–1005.
184. Ramsköld, L. & Chen, J.-Y. (1998). Cambrian lobopodians: Morphology and phylogeny. In Arthropod Fossils and Phylogeny (ed. G. Edgecombe), pp. 107–150. Columbia University Press, New York.
185. Ramsköld, L. & Hou, X. (1991). New Early Cambrian animal and onychophoran affinities of enigmatic metazoans. Nature 351, 225–228.
186. Raup, D. (1983). On the early origins of major biologic groups. Paleobiology 9, 107–198.
187. Reichelt, A. C. (1991). Environmental effects of meiofaunal burrowing. In The Environmental Impact of Burrowing Animals and Animal Burrows (ed. P. S. Meadows and A. Meadows), pp. 33–52. Clarendon Press, Oxford.
188. Rieger, R. (1985). The phylogenetic status of the acoelomate organization within the Bilateria: A histological perspective. In The origins and relationships of lower invertebrates (ed. S. Conway Morris, J. D. George, R. Gibson and H. M. Platt), pp. 101–122. Oxford University Press, Oxford.
189. Rieger, R. M. (1994). Evolution of the ‘lower’ Metazoa. In Early Life on Earth (ed. S. Bengtson), pp. 475–488. Columbia University Press, New York.
190. Rieger, R. M., Haszprunar, G. & Schuchert, P. (1991). On the origin of the Bilateria; traditional views and recent alternative concepts. In The Early Evolution of Metazoa and the Significance of Problematic Taxa. (ed. A. M. Simonetta and S. Conway Morris), pp. 107–112. Cambridge University Press, Cambridge.
191. Rieppel, O. (1988). Fundamentals of Comparative Biology. Birkhauser Verlag, Berlin.
192. Rigby, S. (1997). A comparison of the colonization of the planktic realm and the land. Lethaia 30, 11–17.
193. Rigby, S. & Milsom, C. (1996). Benthic origins of zooplankton: An environmentally determined macroevolutionary effect. Geology 24, 52–54.
194. Rowell, A. J. (1977). Early Cambrian brachiopods from the south-western Great Basin of California and Nevada. Journal of Paleontology 51, 68–85.
195. Rowell, A. J. (1982). The monophyletic origin of the Brachiopoda. Lethaia 15, 299–307.
196. Ruiz Trillo, I., Riutort, M., Littlewood, D. T. J., Herniou, E. A. & Baguna, J. (1999). Acoel flatworms: Earliest extant bilaterian metazoans, not members of Platyhelminthes. Science 283, 1919–1923.
197. Runnegar, B. (1982a). A molecular clock model for the origin of animal phyla. Lethaia 15, 199–205.
198. Runnegar, B. (1982b). Oxygen requirements, biology and phylogenetic significance of the late Precambrian worm Dickinsonia, and the evolution of the burrowing habit. Alcheringa 6, 223–239.
199. Runnegar, B. (1991b). Precambrian oxygen levels estimated from the biochemistry and physiology of early eukaryotes. Palaeogeography, Palaeoclimatology, Palaeoecology 97, 97–111.
200. Runnegar, B. (1991a). Oxygen and the early evolution of Metazoa. In Metazoan Life Without Oxygen (ed. C. Bryant), pp. 65–87. Chapman & Hall, London.
201. Runnegar, B. (1995). Vendobionta or Metazoa? Developments in understanding the Ediacara ‘fauna’. Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen 195, 303–18.
202. Runnegar, B. (1996). Early evolution of the Mollusca: The fossil record. In Origin and Evolutionary Radiation of the Mollusca (ed. J. Taylor), pp. 77–87. Oxford University Press, Oxford.
203. Runnegar, B. & Pojeta, J. (1992). The earliest bivalves and their Ordovician descendants. American Malacological Bulletin 9, 117–122.
204. Runnegar, B., Pojeta, J., Morris, N. J., Taylor, J. D., Taylor, M.E. & McClung, G. (1975). Biology of the Hyolitha. Lethaia 8, 181–191.
205. Ruppert, E. E. & Carle, K. J. (1983). Morphology of metazoan circulatory systems. Zoomorphology 103, 193–208.
206. Ruppert, E. E. & Smith, P. R. (1988). The functional organization of filtration nephridia. Biological Reviews 63, 231–258.
207. Salvini-Plawen, L. v. (1998). The urochordate larva and archichordate organization: Chordate origin and anagenesis. Journal of Zoological, Systematic and Evolutionary research 36, 129–145.
208. Saylor, B. Z., Kaufman, A. J., Grotzinger, J. P. & Urban, F. (1998). A composite reference section for terminal Proterozoic strata of Southern Namibia. Journal of Sedimentary Research 68, 1223–35.
209. Scheltema, A. H. (1996). Phylogenetic position of the Sipuncula, Mollusca and the progenetic Aplacophora. In Origin and Evolutionary Radiation of the Mollusca (ed. J. Taylor), pp. 53–58. Oxford University Press, Oxford.
210. Schmidt-Rhaesa, A., Bartolomaeus, T., Lemburg, C., Ehlers, U. & Garey, J. R. (1998). The position of Arthropoda in the phylogenetic system. Journal of Morphology 238, 263–285.
211. Schram, F. R. (1973). Pseudocoelomates and a nemertine from the Illinois Pennsylvanian. Journal of Paleontology 47, 985–989.
212. Schuchert, P. (1993). Phylogenetic analysis of the Cnidaria. Zeitschrift für Zoologische Systematik und Evolutionsforschung 31, 161–173.
213. Schöttler, U. & Bennet, E. M. (1991). Annelids. In Metazoan Life without Oxygen (ed. C. Bryant), pp. 165–185. Chapman & Hall, London.
214. Schwenk, K. (1995). A utilitarian approach to evolutionary constraint. Zoology 98, 251–262.
215. Seilacher, A. (1984). Late Precambrian and early Cambrian metazoa: Preservational or real extinctions? In Patterns of Change in Earth Evolution (ed. H. D. Holland and A. F. Trendall). Springer-Verlag, Berlin.
216. Seilacher, A. (1997). Fossil Art An Exhibition of the Geologisches Institut Tuebingen University. Royal Tyrrell Museum of Paleontology, Drumheller.
217. Seilacher, A. (1999). Biomat-related lifestyle in the Precambrian. Palaios 14, 86–93.
218. Seilacher, A., Bose, P. K. & Pflüger, F. (1998). Triploblastic animals more than 1 billion years ago: Trace fossil evidence from India. Science 282, 80–83.
219. Seilacher, A. & Pflüger, F. (1994). From biomats to benthic agriculture: A biohistoric revolution. In Biostabilization of Sediments (ed. W. E. Krumbein, D. M. Paterson and L. J. L. J. Stal), pp. 97–105. Bibliotheks- und Informationssystem der Universität Oldenburg, Oldenburg.
220. Sepkoski, J. J., Bambach, R. K. & Droser, M. L. (1991). Secular changes in Phanerozoic event bedding and the biological overprint. In Cycles and Events in Stratigraphy (ed. G. Einsele et al.), pp. 298–312. Springer-Verlag, Berlin.
221. Shu, D. G., Zhang, X. & Chen, L. (1996b). Reinterpretation of Yunnanozoon as the earliest known hemichordate. Nature 380, 428–430.
222. Shu, D. G., Conway Morris, S. & Zhang, X. L. (1996a). A Pikaia-like chordate from the Lower Cambrian of China. Nature 384, 157–158.
223. Shu, D. G., Luo, H. L., Conway Morris, S., Zhang, X. L., Hu, S. X., Chen, L., Han, J., Zhu, M., Li, Y & Chen, L. Z. (1999). Lower Cambrian vertebrates from South China. Nature 402, 42–46.
224. Signor, P. W. & Vermeij, G. J. (1994). The plankton and the benthos: Origins and early history of an evolving relationship. Paleobiology 20, 297–319.
225. Simonetta, A. M. (1988). Is Nectocaris pteryx a chordate Bollettino di Zoologia 55, 63–68.
226. Simonetta, A. M. & Insom, E. (1993). New animals from the Burgess Shale (Middle Cambrian) and their possible significance for the understanding of the Bilateria. Bollettino di Zoologia 60, 97–107.
227. Siveter, D. J. & Williams, M. (1997). Cambrian bradoriid and phosphatocopid arthropods of North America. Special Papers in Palaeontology 57, 1–69.
228. Slack, J. M. W., Holland, P. W. H. & Graham, C. F. (1993). The zootype and the phylotypic stage. Nature 361, 490–492.
229. Sleigh, M. A. & Blake, J. R. (1977). Methods of ciliary propulsion and their size implications. In Scale Effects in Animal Locomotion (ed. T. J. Pedley) pp. 243–256. Academic Press, London.
230. Smith, A. (1994). Systematics and the Fossil Record: Documenting Evolutionary Pathways. Blackwell Scientific, Oxford.
231. Smith, M. P., Sansom, I. J. & Repetski, J. E. (1996). Histology of the first fish. Nature 380, 702–704.
232. Snodgrass, R. E. (1935). Principles of Insect Morphology. McGraw-Hill, New York.
233. Sokolov, B. S. (1967). Drevnejshie pogonofory. Doklady Akademii Nauk SSSR 177, 201–204.
234. Sprinkle, J. & Collins, D. (1998). Revision of Echmatocrinus from the Middle Cambrian Burgess Shale of British Columbia. Lethaia 31, 269–282.
235. Strathmann, R. R. & Slatkin, M. (1983). The improbability of animal phyla with few species. Paleobiology 9, 97–106.
236. Szaniawski, H. (1982). Chaetognath spines recognized among Cambrian protoconodonts. Journal of Paleontology 56, 806–810.
237. Szaniawski, H. & Bengtson, S. (1993). Origin of euconodont elements. Journal of Paleontology 67, 640–654.
238. Telford, M. J. & Holland, P. W. H. (1993). The phylogenetic affnities of the chaetognaths: A molecular analysis. Molecular Biology and Evolution. 10, 660–676.
239. Thomas, A. L. R. (1998). Trace fossils and the Cambrian explosion - reply. Trends in Ecology and Evolution 13.
240. Towe, K. M. (1970). Oxygen-collagen priority and the early metazoan fossil record. Proceedings of the National Academy of Sciences, USA 65, 781–788.
241. Truemann, E. R. & Brown, A. C. (1993). Evolution of burrowing in gastropods: The behaviour of the rocky-shore whelk Burnupena catarrhacta on sand. Journal of Molluscan Studies 59, 261–63.
242. Tucker, R. D. & McKerrow, W. S. (1995). Early Paleozoic chronology: A review in light of new U-Pb zircon ages from Newfoundland and Britain. Canadian Journal of Earth Sciences 32, 368–379.
243. Turbeville, J. M., Field, K. G. & Raff, R. A. (1992). Phylogenetic position of phylum Nemertini, inferred from 18S rRNA sequences: Molecular data as a test of morphological character homology. Molecular Biology and Evolution 9, 235–49.
244. Turbeville, J. M. & Ruppert, E. E. (1983). Epidermal muscles and peristaltic burrowing in Carinoma tremaphoros (Nemertini): Correlates of effective burrowing without segmentation. Zoomorphology 103, 103–120.
245. Valentine, J. W. (1973). Evolutionary Paleoecology of the Marine Biosphere. Prentice-Hall, New Jersey.
246. Valentine, J. W. (1994). Late Precambrian bilaterians: Grades and clades. Proceedings of the National Academy of Sciences, USA 91, 6751–6757.
247. Valentine, J. W. (1995). Why no new phyla after the Cambrian? Genome and ecospace hypotheses revisited. Palaios 10, 190–194.
248. Valentine, J. W., Collins, A. G. & Meyer, C. P. (1994). Morphological complexity increase in metazoans. Paleobiology 20, 131–142.
249. Valentine, J. W., Erwin, D. H. & Jablonski, D. (1996). Developmental evolution of metazoan bodyplans: The fossil evidence. Developmental Biology 173, 373–381.
250. Valentine, J. W. & Hamilton, H. (1997). Body plans, phyla and arthropods. In Arthropod Relationships (ed. R. A. Fortey and R. H. Thomas), pp. 1–9. Chapman and Hall, London.
251. Vannier, J. & Abe, K. (1995). Size, body plan and respiration in the Ostracoda. Palaeontology 38, 843–873.
252. Wada, H. (1998). Evolutionary history of free swimming and sessile lifestyles in urochordates as deduced from 18S rDNA molecular phylogeny. Molecular Biology and Evolution 15, 1189–1194.
253. Wada, H. & Satoh, N. (1994). Details of the evolutionary history from invertebrates to vertebrates, as deduced from the sequences of 18S rRNA. Proceedings of the National Academy Sciences, USA 91, 1801–1804.
254. Waggoner, B. M. (1996). Phylogenetic hypotheses of the relationships of arthropods to Precambrian and Cambrian problematic fossil taxa. Systematic Biology 45, 190–222.
255. Waller, T. R. (1998). Origin of the molluscan class Bivalvia and a phylogeny of major groups. In Bivalves: An Eon Evolution - Paleobiological Studies Honoring Norman D. Newell (ed. P. A. Jonhston and J. W. Haggart), pp. 1–45. University of Calgary Press, Calgary.
256. Walossek, D. (1995). The Upper Cambrian Rehbachiella, its larval development, morphology and significance for the phylogeny of Branchiopoda and Crustacea. Hydrobiologia 298, 1–13.
257. Walossek, D. (1999). On the Cambrian diversity of Crustacea. In Crustaceans and the Biodiversity Crisis (ed. F. R. Schram and J. C. von Vaupel Klein), pp. 3–27. Brill, Leiden.
258. Walossek, D. & Müller, K. J. (1990). Upper Cambrian stemlineage crustaceans and their bearing upon the monophyletic origin of Crustacea and the position of Agnostus. Lethaia 23, 409–428.
259. Walossek, D. & Müller, K. J. (1998). Early arthropod phylogeny in light of the Cambrian ‘Orsten’ fossils. In Arthropod Fossils and Phylogeny (ed. G. D. Edgecombe), pp. 185–231. Columbia University Press, New York.
260. Wang, Y.-C., Kumar, S. & Blair Hedges, S. (1999). Divergence time estimates for the early history of animal phyla and the origin of plants, animals and fungi. Proceedings of the Royal Society of London B 266, 163–171.
261. Warwick, R. M. & Price, R. (1979). Ecological and metabolic studies on free-living nematodes on free-living nematodes from an estuarine mud-flat. Estuarine and Coastal Marine Science 9, 257–271.
262. Westheide, W. (1985). The systematic position of the Dinophilidae and the archiannelid problem. In The Origins and Relationships of Lower Invertebrates (ed. S. Conway Morris, J. D. George, R. Gibson and H. M. Platt), pp. 310–326. Oxford University Press, Oxford.
263. Westheide, W. (1997). The direction of evolution within the polychaeta. Journal of Natural History 31, 1–15.
264. Whittington, H. B. (1978). The lobopodian animal Aysheaia pedunculata Walcott, Middle Cambrian, British Columbia. Philosophical Transactions of the Royal Society of London B 280, 165–197.
265. Willis, J. C. (1940). The Course of Evolution by Differentiation or Divergent Mutation, Rather than by Selection. Cambridge University Press, Cambridge.
266. Willmer, P. (1990). Invertebrate Relationships. Cambridge University Press, Cambridge.
267. Wills, M. A. (1998). Cambrian and Recent disparity: The picture from priapulids. Paleobiology 24, 177–199.
268. Wingstrand, K. G. (1985). On the anatomy and relationships of Recent Monoplacophora. Galathaea Report 16, 7–94.
269. Wray, G. A., Levinton, J. S. & Shapiro, L. M. (1996). Molecular evidence for deep pre-Cambrian divergences among metazoan phyla. Science 214, 568–573.
270. Xiao, S. H., Zhang, Y. & Knoll, A. H. (1998). Threedimensional preservation of algae and animal embryos in a Neoproterozoic phosphorite. Nature 391, 553–558.
271. Yatsu, N. (1902). On the development of Lingula anatina. Journal of the College of Science, Imperial University, Tokyo, Japan 17, 1–112, pls 1–8.
272. Yochelson, E. L. (1979). Early radiation of Mollusca and mollusc-like groups. In The Origin of Major Invertebrate Groups (ed. M. R. House), pp. 323–358. Academic Press, London.
273. Yochelson, E. L. (1981). Fordilla troyensis Barrande: ‘the oldest known pelecypod’ may not be a pelecypod. Journal of Paleontology 55, 113–125.
274. Yu Wen (1984). On merismoconchids [in Chinese]. Acta Palaeontologica Sinica 23, 432–446, pls 1–3.
275. Yu Wen (1987). Yangtze micromolluscan fauna in Yangtze region of China with notes on Precambrian-Cambrian boundary. Stratigraphy and Palaeontology of Systemic Boundaries in China. Precambrian-Cambrian Boundary 1, 19–275, pls 1–68.
276. Yu Wen (1990). The first radiation of shelled molluscs. Palaeontologia Cathayana 5, 139–170.
277. Zimmer, R. L. (1980). Mesodermal proliferation and formation of the protocoel and metacoel in early embryos of Phoronis vancouverensis (Phoronida). Zoologische Jahrbücher, Abteilung Anatomie 103, 219–232.
278. Zimmer, R. L. (1997). Phoronids, brachiopods and bryozoans. In Embrology: Constructing the Organism (ed. S. F. Gilbert and A. M. Raunio), pp. 279–305. Sinauer Associates, Sunderland.