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

  title={Evolution of the Turtle Body Plan by the Folding and Creation of New Muscle Connections},
  author={Hiroshi Nagashima and Fumiaki Sugahara and Masaki Takechi and Rolf Ericsson and Yoshie Kawashima-Ohya and Yuichi Narita and Shigeru Kuratani},
  pages={193 - 196}
Shelling Turtles In almost all vertebrates, the shoulder girdle (scapula) lies outside the ribs. The turtle is unique in that the carapace, the dorsal part of the shell, which is formed from the ribs, encapsulates the scapula. To understand the origin of the turtle-specific body plan, Nagashima et al. (p. 193; see the cover; see the Perspective by Rieppel) compared chicken, mouse, and the Chinese soft shelled-turtle, Pelodiscus sinensis. Modern embryos were studied via whole-mount… 

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.

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.

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 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.

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

The turtle body plan can be explained with knowledge of vertebrate anatomy and developmental biology, consistent with the evolutionary origin of the turtle suggested by the recently discovered fossil species, Odontochelys.

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.

The endoskeletal origin of the turtle carapace

This work examines turtle embryos and finds that the costal and neural plates develop not within the dermis, but within deeper connective tissue where the rib and intercostal muscle anlagen develop.

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.

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.

Development of the turtle plastron, the order-defining skeletal structure

It is suggested that the early osteogenic fate adopted by the ventral mesenchyme prevents the chondrogenic sternal development in turtles and that this was a critical step in forming the ossification centers for this new type of vertebrate structure.



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.

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.

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.

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.

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'.

An ancestral turtle from the Late Triassic of southwestern China

A new 220-million-year-old turtle from China is described that documents an intermediate step in the evolution of the shell and associated structures and shows that the turtle shell is not derived from a fusion of osteoderms.

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.

Development of an evolutionarily novel structure: fibroblast growth factor expression in the carapacial ridge of turtle embryos.

Data is presented suggesting that carapace formation is initiated by co-opting genes that had other functions in the ancestral embryo, specifically those of limb outgrowth, and there is divergence in the signaling repertoire from that involved in limb initiation and outgrowth.

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.