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. 2009 Mar 7;276(1658):879-86.
doi: 10.1098/rspb.2008.1429.

A new stem turtle from the Middle Jurassic of Scotland: new insights into the evolution and palaeoecology of basal turtles

Jérémy Anquetin  1 , Paul M Barrett, Marc E H Jones, Scott Moore-Fay, Susan E Evans
Affiliations

A new stem turtle from the Middle Jurassic of Scotland: new insights into the evolution and palaeoecology of basal turtles

Jérémy Anquetin et al. Proc Biol Sci. .

Abstract

The discovery of a new stem turtle from the Middle Jurassic (Bathonian) deposits of the Isle of Skye, Scotland, sheds new light on the early evolutionary history of Testudinata. Eileanchelys waldmani gen. et sp. nov. is known from cranial and postcranial material of several individuals and represents the most complete Middle Jurassic turtle described to date, bridging the morphological gap between basal turtles from the Late Triassic-Early Jurassic and crown-group turtles that diversify during the Late Jurassic. A phylogenetic analysis places the new taxon within the stem group of Testudines (crown-group turtles) and suggests a sister-group relationship between E. waldmani and Heckerochelys romani from the Middle Jurassic of Russia. Moreover, E. waldmani also demonstrates that stem turtles were ecologically diverse, as it may represent the earliest known aquatic turtle.

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Figures

Figure 1
Figure 1
Eileanchelys waldmani gen. et sp. nov. Stereophotographs of the skull NMS G 2004.31.15 (holotype) in (a,b) ventral and (c,d) posteroventrolateral view. Scale bars 1 cm. Abbreviations: acst, aditus canalis stapedio-temporalis; ap, antrum postoticum; bo, basioccipital; bs, basisphenoid; cc, posterior opening of the canalis cavernosus; co, condylus occipitalis; cs, crista supraoccipitalis; ex, exoccipital; feng, foramen externum nervi glossopharyngei; fja, foramen jugulare anterius; fm, foramen magnum; fnh, foramen nervi hypoglossi; fo, fenestra ovalis; fp, fenestra perilymphatica; ica, incisura columellae auris; op, opisthotic; pi, processus interfenestralis of the opisthotic; ppo, processus paroccipitalis of the opisthotic; pr, prootic; pt, pterygoid; qu, quadrate; tbo, tuberculum basioccipitale.
Figure 2
Figure 2
Eileanchelys waldmani gen. et sp. nov. (a,b) carapace NMS G 2004.31.16c in dorsal view and (c,d) shell NMS G 2004.31.16b in dorsal view. Scale bars 5 cm. Abbreviations: ce, cervical scute; c, costal; m, marginal scute; n, neural; nu, nuchal; p, peripheral; pl, pleural scute; py, pygal; sp, suprapygal; v, vertebral scute; *, supernumerary plate.
Figure 3
Figure 3
Phylogenetic relationships of E. waldmani gen. et sp. nov. (a) Strict consensus tree of 190 most parsimonious trees (MPTs) of 363 steps (analysis 1); 472 steps; consistency index (CI)=0.360; retention index (RI)=0.713; (b) strict consensus tree of 1800 MPTs of 366 steps (analysis 2); 511 steps; CI=0.333; RI=0.683; (c) Adams consensus tree of 1800 MPTs of 366 steps (analysis 2); 386 steps; CI=0.441; RI=0.800; (d) 50% majority rule consensus tree of 1800 MPTs of 366 steps (analysis 2); 370 steps; CI=0.460; RI=0.815. The clade Eucryptodira (sensu Joyce et al. 2004) is not detailed in trees (c,d).
Figure 4
Figure 4
Strict reduced consensus (SRC) tree derived by a posteriori pruning of C. antiqua from the set of 1800 MPTs generated by the second analysis. This tree reveals a strictly supported sister-group relationship between E. waldmani gen. et sp. nov. and H. romani. The clade Testudines (sensu Joyce et al. 2004) is not detailed (other SRC trees are provided in the electronic supplementary material).
Figure 5
Figure 5
The evolution of the vomer among basal turtles. (a,d) Proganochelys quenstedti, (b,e) E. waldmani, and (c,f) Chelydra serpentina. (a–c) Ventral view and (d–f) sagittal section. (a) Redrawn from Gaffney (: fig. 27) and (c) redrawn from Gaffney (: fig. 217). Abbreviations: ani, apertura narium interna; fon, foramen orbito-nasale; fp, foramen praepalatinum; fpp, foramen palatinum posterius; la, lacrimal; mx, maxilla; pal, palatine; pf, prefrontal; pm, premaxilla; pt, pterygoid; vo, vomer.
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References

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