Header

UZH-Logo

Maintenance Infos

Fossorial origin of the turtle shell


Lyson, Tyler R; Rubidge, Bruce S; Scheyer, Torsten M; de Queiroz, Kevin; Schachner, Emma R; Smith, Roger M H; Botha-Brink, Jennifer; Bever, G S (2016). Fossorial origin of the turtle shell. Current Biology, 26(14):1887-1894.

Abstract

The turtle shell is a complex structure that currently serves a largely protective function in this iconically slow-moving group [1]. Developmental [2, 3] and fossil [4-7] data indicate that one of the first steps toward the shelled body plan was broadening of the ribs (approximately 50 my before the completed shell [5]). Broadened ribs alone provide little protection [8] and confer significant locomotory [9, 10] and respiratory [9, 11] costs. They increase thoracic rigidity [8], which decreases speed of locomotion due to shortened stride length [10], and they inhibit effective costal ventilation [9, 11]. New fossil material of the oldest hypothesized stem turtle, Eunotosaurus africanus [12] (260 mya) [13, 14] from the Karoo Basin of South Africa, indicates the initiation of rib broadening was an adaptive response to fossoriality. Similar to extant fossorial taxa [8], the broad ribs of Eunotosaurus provide an intrinsically stable base on which to operate a powerful forelimb digging mechanism. Numerous fossorial correlates [15-17] are expressed throughout Eunotosaurus' skeleton. Most of these features are widely distributed along the turtle stem and into the crown clade, indicating the common ancestor of Eunotosaurus and modern turtles possessed a body plan significantly influenced by digging. The adaptations related to fossoriality likely facilitated movement of stem turtles into aquatic environments early in the groups' evolutionary history, and this ecology may have played an important role in stem turtles surviving the Permian/Triassic extinction event.

Abstract

The turtle shell is a complex structure that currently serves a largely protective function in this iconically slow-moving group [1]. Developmental [2, 3] and fossil [4-7] data indicate that one of the first steps toward the shelled body plan was broadening of the ribs (approximately 50 my before the completed shell [5]). Broadened ribs alone provide little protection [8] and confer significant locomotory [9, 10] and respiratory [9, 11] costs. They increase thoracic rigidity [8], which decreases speed of locomotion due to shortened stride length [10], and they inhibit effective costal ventilation [9, 11]. New fossil material of the oldest hypothesized stem turtle, Eunotosaurus africanus [12] (260 mya) [13, 14] from the Karoo Basin of South Africa, indicates the initiation of rib broadening was an adaptive response to fossoriality. Similar to extant fossorial taxa [8], the broad ribs of Eunotosaurus provide an intrinsically stable base on which to operate a powerful forelimb digging mechanism. Numerous fossorial correlates [15-17] are expressed throughout Eunotosaurus' skeleton. Most of these features are widely distributed along the turtle stem and into the crown clade, indicating the common ancestor of Eunotosaurus and modern turtles possessed a body plan significantly influenced by digging. The adaptations related to fossoriality likely facilitated movement of stem turtles into aquatic environments early in the groups' evolutionary history, and this ecology may have played an important role in stem turtles surviving the Permian/Triassic extinction event.

Statistics

Citations

9 citations in Web of Science®
10 citations in Scopus®
Google Scholar™

Altmetrics

Downloads

9 downloads since deposited on 27 Jul 2016
4 downloads since 12 months
Detailed statistics

Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Paleontological Institute and Museum
Dewey Decimal Classification:560 Fossils & prehistoric life
Language:English
Date:2016
Deposited On:27 Jul 2016 12:12
Last Modified:01 Sep 2017 00:00
Publisher:Cell Press (Elsevier)
ISSN:0960-9822
Publisher DOI:https://doi.org/10.1016/j.cub.2016.05.020
Related URLs:http://www.media.uzh.ch/de/medienmitteilungen/2016/Schildkr%C3%B6te-.html (Organisation)
PubMed ID:27426515

Download

Download PDF  'Fossorial origin of the turtle shell'.
Preview
Content: Accepted Version
Filetype: PDF
Size: 5MB
View at publisher