Evolutionary developmental perspective for the origin of turtles: the folding theory for the shell based on the developmental nature of the carapacial ridge

  title={Evolutionary developmental perspective for the origin of turtles: the folding theory for the shell based on the developmental nature of the carapacial ridge},
  author={Shigeru Kuratani and Shigehiro Kuraku and Hiroshi Nagashima},
  journal={Evolution \& Development},
The body plan of the turtle represents an example of evolutionary novelty for acquisition of the shell. [] Key Result The growth of the ribs is arrested in the axial part of the body, allowing dorsal and lateral oriented growth to encapsulate the scapula.

Origin of the Turtle Body Plan: The Folding Theory to Illustrate Turtle-Specific Developmental Repatterning

This developmental sequence of the modern turtles aligns with a stepwise evolutionary process in the group, which is supported by the anatomy of a recently discovered fossil species, Odontochelys.

Body plan of turtles: an anatomical, developmental and evolutionary perspective

Comparative developmental data allow us to hypothesize the gradual evolution of turtles, which is consistent with the recent finding of a transitional fossil animal, Odontochelys, which did not have the carapace but already possessed the plastron.

The evolutionary origin of the turtle shell and its dependence on the axial arrest of the embryonic rib cage.

Both paleontological and genomic evidence suggest that the axial arrest is the first step toward acquisition of the turtle body plan, which is estimated to have taken place after the divergence of a clade including turtles from archosaurs.

The origin and loss of periodic patterning in the turtle shell

It is shown that scutes develop from an array of patterned placodes and that these placodes are absent from a soft-shelled turtle in which scutes were lost secondarily, and how two coupled reaction-diffusion systems reproduce both natural and abnormal variation in turtle scutes is shown.

The Turtle Evolution: A Conundrum in Vertebrate Evo-Devo

The stepwise, not necessarily saltatory, evolution of turtles is hypothesized, consistent with the recent finding of a transitional fossil animal, Odontochelys, that did not have the carapace but already possessed the plastron.

Comparative study of the shell development of hard‐ and soft‐shelled turtles

No evidence was found that would support a neural crest origin in the dorsal shell development of the hard‐shelled turtles, and the ventral portion of the shell, on the other hand, contains massive dermal bones.

Evolution of the turtle bauplan: the topological relationship of the scapula relative to the ribcage

The topological relationship of the shoulder girdle relative to the ribcage is analysed within a broader phylogenetic context and it is determined that the condition found in turtles is also found in amphibians, monotreme mammals and lepidosaurs.

On the homology of the shoulder girdle in turtles.

The history of the debate on the homology of the shoulder girdle in turtles is traced and based on the integrative aspects of developmental biology, comparative morphology, and paleontology, acromion and procoracoid identities for the two ventral processes are suggested.

Comparative analysis of pleurodiran and cryptodiran turtle embryos depicts the molecular ground pattern of the turtle carapacial ridge.

It is suggested that the turtle shell probably originated concomitantly with the co-option of the canonical Wnt signaling pathway into the CR in the last common ancestor of the turtle.

Evolutionary Origin of the Turtle Shell




Evolution of the Turtle Body Plan by the Folding and Creation of New Muscle Connections

This work proposes that the evolutionary origin of the turtle body plan results from heterotopy based on folding and novel connectivities, and suggests that some limb muscles establish new turtle-specific attachments associated with carapace formation.

The Development and Evolution of the Turtle Body Plan: Inferring Intrinsic Aspects of the Evolutionary Process from Experimental Embryology

Surgical perturbations were designed to test the causal connection between the epithelial-mesenchymal interaction in the body wall and the unusual placement of the ribs in turtles.

On the carapacial ridge in turtle embryos: its developmental origin, function and the chelonian body plan

It is concluded that the CR is a true embryonic novelty among amniotes and, because of the specific expression of regulatory genes, it functions in the marginal growth of the carapacial primordium, thereby inducing the fan-shaped arrangement of the ribs.

Morphogenesis of the turtle shell: the development of a novel structure in tetrapod evolution

An anatomical investigations into plastron and carapace formation in the red‐eared slider, Trachemys scripta, and the snapping turtle, Chelydra serpentina suggest that the rib is organizing dermal ossification by secreting paracrine factors.

Development of the carapacial ridge: implications for the evolution of genetic networks in turtle shell development

Molecular evidence is shown supporting a dermomyotomal identity for the mesenchyme of the turtle carapacial ridge and establishes a new role for this mesodermal compartment and highlights the importance of changes in genetic regulation in the evolution of morphology.

How the turtle forms its shell: a paracrine hypothesis of carapace formation.

It is shown here that the carapacial ridge (CR) is critical for the entry of the ribs into the dorsal dermis, and that the maintenance of the CR and its ability to attract the migrating rib precursor cells depend upon fibroblast growth factor (FGF) signaling.

Development of the turtle carapace: Implications for the evolution of a novel bauplan

  • A. Burke
  • Biology
    Journal of morphology
  • 1989
Embryos of Chelydra serpentina were studied during stages of carapace development and tissue morphology, autoradiography, and indirect immunofluorescent localization of adhesion molecules indicate that the outgrowth of the embryonic carapACE occurs as the result of an epithelial–mesenchymal interaction in the body wall.

Correlated progression and the origin of turtles

It is shown that certain pareiasaurs—dwarf, heavily armoured forms such a Nanoparia—approach the chelonian morphology even more closely than previously thought, suggesting that the rigid armoured body of turtles evolved gradually, through 'correlated progression'.

Turtle–chicken chimera: An experimental approach to understanding evolutionary innovation in the turtle

It is concluded that chicken and P. sinensis share the developmental programs necessary for the early differentiation of somites and that turtle-specific traits in muscle patterning arise mainly through a cell‐autonomous developmental process in the somites per se, however, the mechanism for turtle‐specific cartilage patterning, including that of the ribs, is not supported by the chicken embryonic environment.

Msx genes are expressed in the carapacial ridge of turtle shell: a study of the European pond turtle, Emys orbicularis

The embryonic expression of Msx genes in the European pond turtle, Emys orbicularis is studied and observations may indicate that common mechanisms participate in limb bud and CR early development, but that pre-differentiation steps differ between shell and other skeletal structures and involve other gene activities than that ofMsx genes.