C. Nielsen

Publications65
h-index28
Citations3,004
Highly Influential Citations171
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Animal Evolution: Interrelationships of the Living Phyla
Kingdom Animalia early animal radiation prelude: phylum choanoflagellata phylum porifera phylum placozoa eumetazoa phylum cnidaria tripoblastica phylum ctenophora phylum bilateria protostoma spiralia…
The Development of the Brachiopod Crania (Neocrania) anomala (O. F. Müller)and its Phylogenetic Significance
TLDR
Both groups have originated from a creeping ancestor with a straight gut and the ventral curving of the settling larva and the formation of both valves from dorsal epithelial areas indicate that the brachiopods have a very short ventral side as opposed to the phoronids.
Six major steps in animal evolution: are we derived sponge larvae?
  • C. Nielsen
  • Biology
    Evolution & development
  • 1 March 2008
TLDR
A review of the old and new literature on animal morphology/embryology and molecular studies has led me to the following scenario for the early evolution of the metazoans, where the metazoan ancestor was a pelagic sphere consisting of choanocytes.
Tentacle structure and filter-feeding in Crisia eburnea and other cyclostomatous bryozoans, with a review of upstream-collecting mechanisms
TLDR
The differences in structure and functlon between the tentacles of ectoprocts and those of phoronids, brachiopods and pterobranchs support the idea that the 2 types of tentacle crowns are not homologous.
Trochophora larvae: cell-lineages, ciliary bands, and body regions. 1. Annelida and Mollusca.
  • C. Nielsen
  • Biology
    Journal of experimental zoology. Part B…
  • 15 January 2004
TLDR
The trochophora concept and the literature on cleavage patterns and differentiation of ectodermal structures in annelids ("polychaetes") and molluscs are reviewed, showing conspicuous similarities between the early development of the two phyla, related to the highly conserved spiral cleavage pattern.
Structure and Function of Metazoan Ciliary Bands and Their Phylogenetic Significance
TLDR
The trochaea theory predicts that Porifera and Cnidaria have only monociliate cells and lack ciliary bands used in filter-feeding, and that the gastroneuralian larvae have downstream-collecting ciliated bands with prototroch and metatroch of compound cilia on multiciliate cells.
Trochophora larvae: cell-lineages, ciliary bands and body regions. 2. Other groups and general discussion.
  • C. Nielsen
  • Biology
    Journal of experimental zoology. Part B…
  • 15 September 2005
TLDR
The embryology of sipunculans, entoprocts, nemertines, platyhelminths, rotifers, ectoproCTs, phoronids, brachiopods, echinoderms and enteropneusts is reviewed with special emphasis on cell-lineage and differentiation of ectodermal structures.
Animal phylogeny in the light of the trochaea theory
TLDR
Ultrastructural similarities unite Choanoflagellata and Metazoa as the Kingdom Animalia and proposes that Gastroneuralia and Notoneuralia evolved independently from the trochaea, a blastaea with the blastopore surrounded by a ring of compound cilia, which were both locomotory and particle collecting.
Larval and adult brains.
TLDR
A review of the literature indicates that this small ganglion is the "brain" of the early larva, and it seems probable that it represents the brain of the ancestral, holopelagic ancestor of all eumetazoans, the gastraea.
The Phylogenetic Position of Entoprocta, Ectoprocta, Phoronida, and Brachiopoda1
  • C. Nielsen
  • Biology
    Integrative and comparative biology
  • 1 July 2002
TLDR
The Lophophorata, purported to be held together by the presence of a “lophophore,” is a polyphyletic assemblage and the word should disappear from the zoological vocabulary, just as "Vermes" disappeared many years ago.
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