Fig 1.
Saurodersmus robertsoni NHMUK PV OR 28877, right femur and associated rock fragment before they were separated.
“Drawn by J. Stiven, from a specimen found at Linksfield by Alexr. Robertson Esqr. Inverugie F. G. S. Elgin 1840”. Watercolour. Note the bone is figured upside-down (proximal end towards the bottom of the page). Reproduced by permission of the Geological Society of London.
Table 1.
Cynodont taxa allowing morphological comparisons with NHMUK PV OR 28877 and relevant literature references and original specimens examined personally, as 3D models, or in previously unpublished photographs.
Fig 2.
Saurodersmus robertsoni NHMUK PV OR 28877, right femur (A–B, D–I, K, L) in anterior (A, D), posterior (B, F), lateral (E), medial (G), proximal (H), and distal (I) view, closeup of the natural cross-section through the shaft (K, L), and associated rock fragment with natural mould of the posterior surface of the bone (A, C, J) with the bone in place (A) and removed (C), and backside (J). Two historical labels on the rock read “? Spec. referred to by Prof. Owen in Brit. Ass. Rep. 1841 p. 168” and “Unique Chelonian Bone from Linksfield, near Elgin” (J) Panels C–I are presented with the Radiance Scaling (Lit Sphere) shader enabled to enhance the geometric detail.
Fig 3.
Simplified phylogenetic tree of Amniota showing taxa discussed in the text, including groups that Saurodesmus robertsoni was referred to in the past.
Composite topology based on various sources, including [155–159]. See Acknowledgements for the sources of images.
Fig 4.
Comparison of Saurodersmus robertsoni NHMUK PV OR 28877 with humeri of turtles.
Ectepicondylar grooves/foramina indicated by red arrowheads. Not to scale.
Fig 5.
Comparison of Saurodersmus robertsoni NHMUK PV OR 28877 with femora of turtles.
Not to scale.
Fig 6.
Comparison of Saurodersmus robertsoni NHMUK PV OR 28877 with femora of non-diapsid reptiles.
Not to scale.
Fig 7.
Comparison of Saurodersmus robertsoni NHMUK PV OR 28877 with humeri of archosaurs and with humerus and femur of a rhynchocephalian.
Ectepicondylar groove or foramen indicated by red arrowheads, entepicondylar foramen indicated by green arrowheads. Not to scale.
Fig 8.
Comparison of Saurodersmus robertsoni NHMUK PV OR 28877 with femora of non-cynodontian synapsids.
Not to scale.
Fig 9.
Comparison of Saurodersmus robertsoni NHMUK PV OR 28877 with femora of non-probainognathian cynodonts.
Not to scale. Note the variable development of the hooked greater trochanter in cynognathians.
Fig 10.
Comparison of Saurodersmus robertsoni NHMUK PV OR 28877 with femora of non-tritylodontid probainognathian cynodonts.
Not to scale.
Fig 11.
Comparison of Saurodersmus robertsoni NHMUK PV OR 28877 with femora of tritylodontid cynodonts.
Three dorsal eminences proximal to condyles and the epicondyle shared by Saurodesmus robertsoni and Bienotherium yunnanense indicated by red arrowheads. Note that the middle eminence is located nearly at the level of the long axis of the bone. Not to scale.
Fig 12.
Cynodont phylogeny (compiled from [264–266], taxa with femora preserved mentioned in the text) with appearances of femoral characters discussed in the text mapped within the Prozostrodontia.
Note that exact distribution of characters is difficult to establish due to scarcity of femoral characters used in phylogenetic analyses and some specimens not referred to the genus level and not included in previous phylogenies.