Embryogenesis and ossification of Emydura subglobosa (Testudines, Pleurodira, Chelidae) and patterns of turtle development

Abstract

Using the Standard Event System (SES) to study patterns of vertebrate development, we describe a series of 17 embryos of the pleurodire turtle Emydura subglobosa. Based on a sequence heterochrony analysis including 23 tetrapod taxa, we identified autapomorphic developmental shifts that characterise Testudines, Cryptodira, and Pleurodira. The main results are that Testudines are characterised by an autapomorphic late neck development, whereas pleurodires and cryptodires show a different developmental timing of the mandibular process. Additionally, we described the ossification pattern of E. subglobosa and compared the data to those of five other turtles. Pleurodires show the epiplastron to ossify before or simultaneously with maxilla and dentary. In contrast, cryptodires show a later ossification of this bone. Because evolutionary developmental studies on turtles have previously focused only on ''model organisms'' that all belong to Cryptodira, we underline the necessity to include a pleurodire taxon for a more comprehensive, phylogenetically more informative approach.

Revision of the Triassic European turtlesProterochersisandMurrhardtia(Reptilia, Testudinata, Proterochersidae), with the description of new taxa from Poland and Germany

“…the row of suprapygals and pygal was also incomplete. These elements are absent in Odontochelys semitestacea, and in modern turtles they are (along with peripheral bones) the last elements to ossify (Gilbert et al, 2001;Scheyer, Br€ ullmann & S anchez-Villagra, 2008;Werneburg et al, 2009;Lima et al, 2011). This late ontogenesis may possibly reflect their relatively late evolutionary origin.…”

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

“…Turtle skeleton formation has been studied in multiple species from hardshelled to soft-shelled turtles and from side-necked (Pleurodira) to hidden-neck turtles (Cryptodira) (33,(36)(37)(38)(39)(40). These studies have emphasized the development of the carapacial skeleton, following the order of mineralization of skeletal elements during late embryogenesis and comparing carapace development between different species of turtles.…”

Recent insights into the morphological diversity in the amniote primary and secondary palates

“…A) E11.5 mouse ( Mus musculus ); B) 10-day crocodile ( Crocodilus niloticus (Peterka et al, 2010); C) stage 28 chicken ( Gallus gallus - (Hamburger and Hamilton, 1951); D) stage 4 turtle ( Emydura subglobosa - (Werneburg et al, 2009); E) stage 34 chameleon ( Chamaeleo calyptratus (Blanc, 1974). A’) High magnification of mouse fusion zone depicting the lambdoid (λ) junction as white dashed lines at the boundary where all three prominences meet.…”