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

  title={Body plan of turtles: an anatomical, developmental and evolutionary perspective},
  author={Hiroshi Nagashima and Shigehiro Kuraku and Katsuhisa Uchida and Yoshie Kawashima-Ohya and Yuichi Narita and Shigeru Kuratani},
  journal={Anatomical Science International},
The evolution of the turtle shell has long been one of the central debates in comparative anatomy. [] Key Result Comparing the spatial relationships of anatomical structures in the embryos of turtles and other amniotes, we have shown that the topology of the musculoskeletal system is largely conserved even in turtles. The positional changes seen in the ribs and pectoral girdle can be ascribed to turtle-specific folding of the lateral body wall in the late developmental stages.

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.

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 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.

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.

Evolution, Diversity, and Development of the Craniocervical System in Turtles with Special Reference to Jaw Musculature

A hypothetical model for ancestral states and gross morphology of the jaw adductor musculature in Proganochelys quenstedti (the earliest turtle with a complete shell) is proposed, an important step toward the understanding of the evolution of those muscles in turtles.

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.

Patterns of morphological evolution in the skull of turtles: contributions from digital paleontology, neuroanatomy and biomechanics

Using 3-D models and ancestral state reconstructions, the arrangement and gross morphology of the jaw adductor musculature in Proganochelys quenstendti, the earliest turtle with a complete shell, is inferred, an important step towards the understanding of the evolution of those muscles in turtles.

Emerging from the rib: resolving the turtle controversies.

Two of the major controversies in the present study of turtle shell development involve the mechanism by which the carapacial ridge initiates shell formation and the mechanism by which each rib forms

The early composition and evolution of the turtle shell (Reptilia, Testudinata)

The shell of the oldest true turtle (Testudinata) branch (Proterochersidae) from the Late Triassic (Norian) of Poland and Germany was built in its anterior and posterior part from an osteodermal



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.

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.

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.

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'.

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.

Hepatocyte growth factor is crucial for development of the carapace in turtles

It is concluded that the de novo expression of HGF in the turtle mesoderm would have played an innovative role resulting in the acquisition of the turtle‐specific body plan.

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.

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.

The Origin of the Turtle Body Plan: Bridging a Famous Morphological Gap

In pareiasaurs, the osteoderms represent the precursors of the chelonian shell and the morphology of the anterior region is consistent with the idea that the shoulder girdle in turtles has migrated posteriorly into the rib cage.