The developmental cycles of early Cambrian Olivooidae fam. nov. (?Cycloneuralia) from the Yangtze Platform (China)

Embryology in Deep Time

“…Quadrapyrgites occurs in association with Olivooides , and in general terms its embryonic and postembryonic growth and developmental stages are identical to those described for Olivooides , with the principal distinction that Quadrapyrgites is tetraradial (Steiner et al 2014 ).…”

“…Concerns over differences in the pentaradial symmetry of Olivooides and the generally (but far from exclusively) tetraradiality of cnidarians may certainly be dismissed on the description of Quadrapyrgites , which differs materially from Olivooides only in terms of its tetraradial symmetry. Finally, the description of minute pentaradial strobilating medusae in association with Olivooides would appear to settle debate over its affi nity (though this is disputed by Steiner et al 2014 ). In sum, the available evidence supports the interpretation of the olivooids as medusozoan cnidarians, and their similarity to scyphozoans must represent either shared derived or shared primitive characteristics; only a better understanding of the interrelationships of extant cnidarians and morphological character evolution among them will aid a more precise classifi cation for the olivooids.…”

“…Debate over the affi nity of the olivooids has been wide-ranging, including echinoderms , scalidophorans (Steiner et al 2014 ), cnidarians (Bengtson and Yue 1997 ;Yue and Bengtson 1999 ;Han et al 2013 ), and diploblastic stem-eumetazoans (Yasui et al 2013 ). The hypothesis of echinoderm affi nity is based on little more than pentaradial symmetry and can be rejected since the olivooids lack key echinoderm apomorphies, not least a mineralised skeleton comprised of calcite stereom (Dong et al 2013 ;Han et al 2013 ;Steiner et al 2014 ).…”

“…The hypothesis of echinoderm affi nity is based on little more than pentaradial symmetry and can be rejected since the olivooids lack key echinoderm apomorphies, not least a mineralised skeleton comprised of calcite stereom (Dong et al 2013 ;Han et al 2013 ;Steiner et al 2014 ). The scalidophoran interpretation is based principally on the general similarity between the theca of olivooids and the lorica of loriciferans and larval priapulids, together with similarities in general symmetry and the requirement of the aperture to open and close akin to a scalidophoran introvert (Steiner et al 2014 ). However, these similarities are vague, and the demonstrable absence of a through gut and a scalid-bearing introvert are incompatible with a scalidophoran interpretation of the olivooids.…”

“…There was palpable excitement in these early days that an extra dimension to the fossil record had been revealed and evolutionary biologists would soon be integrating the embryology of trilobites, ammonites, and anomalocaridids, with that of their living kin, effecting tests of developmental evolution that would be as direct as possible without the aid of a time machine, settling centuries-old debates over the plesiomorphy of gastrulation modes and the like . Indeed, embryos and larvae of a great diversity of animals have been reported, including stem-metazoans (Hagadorn et al 2006 ), sponges (Chen et al 2000(Chen et al , 2009a, cnidarians (Bengtson and Yue 1997 ;Kouchinsky et al 1999 ;Yue and Bengtson 1999 ;Chen et al 2000Chen et al , 2002Chen et al , 2009aChen and Chi 2005 ;Dong et al 2013 ), ctenophores (Chen et al 2007 ), bilaterians generally (Chen et al 2000(Chen et al , 2006(Chen et al , 2009a, or, more specifi cally, arthropods and scalidophorans (Dong et al 2004Donoghue et al 2006a ;Steiner et al 2014 ), the majority of which are from the Ediacaran Doushantuo Formation and the Early Cambrian Kuanchuanpu Formation, both of South China. Not all of these interpretations have withstood scrutiny, principally because palaeobiologists and embryologists have been unprepared in interpreting these most remarkable of fossil remains.…”