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Morphological research on amniote eggs and embryos: An introduction and historical retrospective.

Authors
  • Blackburn, Daniel G1
  • Stewart, James R2
  • 1 Department of Biology and Electron Microscopy Center, Trinity College, Hartford, Connecticut, USA.
  • 2 Department of Biological Sciences, East Tennessee State University, Johnson City, Tennessee, USA.
Type
Published Article
Journal
Journal of morphology
Publication Date
Jul 01, 2021
Volume
282
Issue
7
Pages
1024–1046
Identifiers
DOI: 10.1002/jmor.21320
PMID: 33393149
Source
Medline
Keywords
Language
English
License
Unknown

Abstract

Evolution of the terrestrial egg of amniotes (reptiles, birds, and mammals) is often considered to be one of the most significant events in vertebrate history. Presence of an eggshell, fetal membranes, and a sizeable yolk allowed this egg to develop on land and hatch out well-developed, terrestrial offspring. For centuries, morphologically-based studies have provided valuable information about the eggs of amniotes and the embryos that develop from them. This review explores the history of such investigations, as a contribution to this special issue of Journal of Morphology, titled Developmental Morphology and Evolution of Amniote Eggs and Embryos. Anatomically-based investigations are surveyed from the ancient Greeks through the Scientific Revolution, followed by the 19th and early 20th centuries, with a focus on major findings of historical figures who have contributed significantly to our knowledge. Recent research on various aspects of amniote eggs is summarized, including gastrulation, egg shape and eggshell morphology, eggs of Mesozoic dinosaurs, sauropsid yolk sacs, squamate placentation, embryogenesis, and the phylotypic phase of embryonic development. As documented in this review, studies on amniote eggs and embryos have relied heavily on morphological approaches in order to answer functional and evolutionary questions. © 2021 Wiley Periodicals LLC.

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