Eosauropus

Main evolutionary steps proposed for the morphofunctional and postural changes of the sauropod pedes. (A) Sauropod body mass through time (in metric tons) based on the sauropod body mass estimations of (41) (NB: data lacking for the second half of the Upper Cretaceous so illustrated here faded, in continuity with the data recorded in the Cretaceous). Schematic outlines of selected large specimens illustrated in the curve, including (from left to right) P. engelhardti, Vulcanodon karibaensis, R. brownei, G. brancai, Cedarosaurus weiskopfae, and Notocolossus gonzalezparejasi. (B) Projected evolutionary changes occurring in the sauropod pes associated with trend in body mass, including 1, skeletal and functional digitigrade pedal posture among basal non-sauropod sauropodomorphs with an incipient soft tissue pad (ISP) (see figs. S34 and S35); 2 and 3, expansion of a well-developed soft tissue pad beneath the elevated pedal bones (SP), resulting in a functionally plantigrade pes + retention of skeletal posture within a range of digitigrady; 4, retention of a soft tissue pad and yet undetermined trend toward more elevated bones; 5, conservation of the neomorphic soft tissue pad within all lineages. Selected examples of well-preserved non-sauropod sauropodomorph and sauropod pedal tracks illustrated above the trends, including (from left to right) Evazoum siriguii; Pseudotetrasauropus bipedoida, Eosauropus isp., Lavinipes cheminii; Kalosauropus pollex, Liujianpus shunan, Polyonyx gomesi; Parabrontopodus mcintoshi; Brontopodus birdi; Titanopodus mendozensis; and unnamed Asian sauropod track. Source of adapted drawing and notes are listed in table S9 and data S2.

Main evolutionary steps proposed for the morphofunctional and postural changes of the sauropod pedes. (A) Sauropod body mass through time (in metric tons) based on the sauropod body mass estimations of (41) (NB: data lacking for the second half of the Upper Cretaceous so illustrated here faded, in continuity with the data recorded in the Cretaceous). Schematic outlines of selected large specimens illustrated in the curve, including (from left to right) P. engelhardti, Vulcanodon karibaensis, R. brownei, G. brancai, Cedarosaurus weiskopfae, and Notocolossus gonzalezparejasi. (B) Projected evolutionary changes occurring in the sauropod pes associated with trend in body mass, including 1, skeletal and functional digitigrade pedal posture among basal non-sauropod sauropodomorphs with an incipient soft tissue pad (ISP) (see figs. S34 and S35); 2 and 3, expansion of a well-developed soft tissue pad beneath the elevated pedal bones (SP), resulting in a functionally plantigrade pes + retention of skeletal posture within a range of digitigrady; 4, retention of a soft tissue pad and yet undetermined trend toward more elevated bones; 5, conservation of the neomorphic soft tissue pad within all lineages. Selected examples of well-preserved non-sauropod sauropodomorph and sauropod pedal tracks illustrated above the trends, including (from left to right) Evazoum siriguii; Pseudotetrasauropus bipedoida, Eosauropus isp., Lavinipes cheminii; Kalosauropus pollex, Liujianpus shunan, Polyonyx gomesi; Parabrontopodus mcintoshi; Brontopodus birdi; Titanopodus mendozensis; and unnamed Asian sauropod track. Source of adapted drawing and notes are listed in table S9 and data S2.

Original figure caption: Trackway S1 (Eosauropus sp.), here attributed to a sauropod trackmaker based on pedal synapomorphies; trackmaker is moving towards the south-west. Two consequtive pes impressions of a tridactyl Grallator [i.e. a theropod] trackway can be seen left to the S1 trackway. Note: The tracks are preserved on a bedding plane of a thin siltstone bed of the Late Triassic Fleming Fjord Formation of East Greenland. A) shows a photograph of the trackway(s) as preserved on the bedding plane (i.e. as concave epireliefs); B) shows a color shaded relief map based on a high-resolution photogrammetric 3D-model of the bedding plane; C) is an interpretative outline drawing of the S1 trackway; abbreviations: LM = left manus (i.e. forefoot), LP = left pes (i.e. hindfoot), RM = right manus, RP = right pes, numbers increase in walking direction.

Cast of the holotype trackway of Eosauropus, a probable sauropodomorph dinosaur ichnogenus, on display at the Museum of Western Colorado’s Dinosaur Journey Museum in Fruita, Colorado