Deuterostomic development in the protostome Priapulus caudatus. Acoel development supports a simple planula-like urbilaterian. Dorsal or ventral: similarities in fate maps and gastrulation patterns in annelids, arthropods and chordates. Amphioxus mouth after dorso-ventral inversion. The study of Priapulus caudatus reveals conserved molecular patterning underlying different gut morphogenesis in the Ecdysozoa. Evolution of the bilaterian larval foregut. Inversion of dorsoventral axis? Nature 371, 26 (1994). Phylogenomic insights into animal evolution. Animal phylogeny and its evolutionary implications.
Teil 1: Einzeller und Wirbellose (eds Westheide, W. Invertebrates 3rd edn (Sinauer, Sunderland, MA, 2016). Animal Evolution: Interrelationships of the Living Phyla 3rd edn, (Oxford Univ. Die Gastraea-Theorie, die phylogenetische Classification des Thierreichs und die Homologie der Keimblätter. Generelle Morphologie der Organismen (Georg Reimer, Berlin, 1866).
Die systematische Einteilung des Tierreichs. We discuss remaining difficulties, and outline directions for future research. Available evidence indicates that stem bilaterians had a slit-like gastric opening that was partially closed in subsequent evolution, leaving open the anus and most likely also the mouth, which would favour amphistomy. Here we review comparative data on the identity and fate of blastoporal tissue, investigate how the formation of the through-gut relates to the major body axes, and discuss to what extent evolutionary scenarios are consistent with these data. Did the single gastric opening evolve into a mouth, with the anus forming elsewhere in the body (protostomy), or did it evolve into an anus, with the mouth forming elsewhere (deuterostomy), or did it evolve into both mouth and anus (amphistomy)? These questions are addressed by the comparison of developmental fates of the blastopore, the opening of the embryonic gut, in diverse animals that live today. However, there is no consensus on how this happened. It is widely held that the bilaterian tubular gut with mouth and anus evolved from a simple gut with one major gastric opening.
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