(A–C) Correlates related to counteracting the forces generated by the forelimb digging apparatus (blue in whole-body illustration) are expressed in the neck (A), skull (B), and thoracic region (C).

(A) Cervical vertebrae (CM 86-341) in dorsal view showing the short, robust cervical centra with bulbous neural spines (ns) and exceptionally massive zygapophyses (zy) that are situated between the vertebral bodies (also see Figure S1 ).

(B) Skull (CM777) in dorsal view showing the short, spade shape with a broaded occipital region and closure of the upper temporal fenestrae.

(C) Trunk region (CM 86-341) in dorsal view showing the anteroposteriorly broadened thoracic ribs.

(D–I) Correlates related to the digging mechanism (red in whole-body illustration) are found in the forelimb (D–F) and shoulder girdle (G).

(D) Large manus (FPM 2014/269) in ventral view showing the short non-terminal phalanges and the large spatula-shaped terminal phalanges (red arrows) that are longer than the penultimate phalanges.

(E) Right humerus (USNM 23009) in anterior view showing the well-developed deltopectoral crest (red arrow).

(F) Left ulna (USNM 23009) in ventral view showing the well-developed olecranon process (red arrow).

(G) Ventrolateral view of the left shoulder girdle (CM777) showing the presence of a large acromion process (red arrow) on the scapula (sc) and a well-developed tubercle (red arrow) on the coracoid (c) for insertion of the triceps muscle. hh, humeral head; ic, interclavicle.

(H–J) Histological section from the proximal diaphysis of a humerus from a juvenile specimen (H; CGP/1/3000) and midshaft section of an ulna from a presumed sub-adult specimen (I; USNM 23009) both with exceptionally thick bone walls (>40% of total width) and abundant Sharpey’s Fibers (red arrows) dorsally and ventrally; both features are lacking in the histological section from the mid-shaft of the fibula from a sub-adult specimen (J; BP/1/7024).