The vertebrates’ new head

Schlosser, Gerhard. (2021). The vertebrates' new head. In Gerhard Schlosser, Development of sensory and neurosecretory cell types: Vertebrate cranial placodes, Volume 1. Boca Raton: CRC Press.

Abstract

The first chapter introduces the vertebrate head. The chapter argues that the vertebrate head is an evolutionary novelty that originated only in the vertebrate lineage. This was first proposed by Northcutt and Gans in their “New Head” hypothesis, which suggested that the “New Head” evolved when filter-feeding ancestors adopted a more active and predatory life-style. These authors also highlighted that the novel structures of the vertebrate head develop from only two novel embryonic tissues, the neural crest and the cranial placodes. After sketching this proposal, the chapter gives a brief overview of vertebrate head development (early development, neural crest, cranial placodes, head segmentation). This is followed by a short survey of the sensory (inner ear and lateral line, olfactory organs) and neurosecretory organs (anterior pituitary) of the vertebrate head developing from cranial placodes. The eye is also briefly introduced here, because the lens develops from a placode and the photoreceptors of the retina are evolutionarily related to other, placode-derived sensory cells (as shown later in the book). A final section provides an introduction to cranial nerves, which are also partly placode derived.

Publisher

CRC Press

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Attribution-NonCommercial-NoDerivatives 4.0 International

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Zoology (Book Chapters)