Volume 26, Issue 20, Pages 2779-2786 (October 2016) Extreme Modification of the Tetrapod Forelimb in a Triassic Diapsid Reptile  Adam C. Pritchard, Alan H. Turner, Randall B. Irmis, Sterling J. Nesbitt, Nathan D. Smith  Current Biology  Volume 26, Issue 20, Pages 2779-2786 (October 2016) DOI: 10.1016/j.cub.2016.07.084 Copyright © 2016 Elsevier Ltd Terms and Conditions

Current Biology 2016 26, 2779-2786DOI: (10.1016/j.cub.2016.07.084) Copyright © 2016 Elsevier Ltd Terms and Conditions

Figure 1 Forelimb Specimens of Drepanosaurus unguicaudatus from the Zorzino Limestone and Chinle Formation (A and B) Right forelimb of the holotype of Drepanosaurus unguicaudatus (MCSNB 5728) in photograph (A) and schematized line drawing (B). (C and D) Right forelimb of the Hayden Quarry Drepanosaurus unguicaudatus (GR 737) in 3D surface reconstruction of μCT scan data (C) and schematized line drawing (D). Interpretations of homologies of forelimb bones based on the current study. Scale bars represent 2 cm. See also Figure S1. Current Biology 2016 26, 2779-2786DOI: (10.1016/j.cub.2016.07.084) Copyright © 2016 Elsevier Ltd Terms and Conditions

Figure 2 Illustrated Forelimb of Drepanosaurus unguicaudatus and Exemplar Fossils from the Hayden Quarry Site Reconstruction of the forelimb of Drepanosaurus unguicaudatus based on the Hayden Quarry forelimb elements. Colors correspond to the following elements: green = humerus, orange = radius, red = ulna, blue = radiale, pale green = intermedium, purple = ulnare, magenta = second metacarpal, white = second manual ungual. (A) Proximal right humerus (GR 740) in anterior view. (B) Distal right humerus (GR 737) in anterior view. (C) Left radius and radiale (GR 736) articulated (image reversed) in lateral view. (D) Left second manual ungual (GR 712) in post-axial view. (E) Right ulna (GR 737) in lateral view. (F) Right intermedium, fused distal carpal complex, and ulnare (GR 737) in dorsal view. (G) Right second metacarpal (GR 738) in dorsal view. Scale bars represent 5 mm. See also Figures S2 and S3 and Table S1. Current Biology 2016 26, 2779-2786DOI: (10.1016/j.cub.2016.07.084) Copyright © 2016 Elsevier Ltd Terms and Conditions

Figure 3 Phylogenetic Affinities of Drepanosaurus unguicaudatus and Forelimb Diversity of Diapsida Strict consensus of six most-parsimonious trees resulting from this analysis (length = 127 steps, consistency index [CI] = 0.646, retention index [RI] = 0.812), with line drawings of the left forelimbs of select non-drepanosauromorph diapsids and drepanosauromorphs in dorsal view. Colors correspond to those in Figure 2. (A) Petrolacosaurus kansensis (based on [12]). (B) Thadeosaurus colcapani (based on MNHN MAP 360). (C) Protorosaurus speneri (based on SMNS cast of WMsN P 47361 and [20]). (D) Shinisaurus crocodilurus (based on [21]). (E) Sphenodon punctatus (based on [22, 23]). (F) Vallesaurus cenensis (based on MCSNB 4751; [16]). (G) Megalancosaurus preonensis (based on MFSN 1921; MPUM 6008, 8437). (H) Drepanosaurus unguicaudatus (based on MCSNB 5728; GR specimens described herein). (I) Silhouette of body plan of Drepanosaurus, based on MCSNB 5728 with head and neck based on Megalancosaurus preonensis (MFSN 1769). All forelimbs are illustrated in a state near maximum extension. See supplementary appendix 4 in the Supplemental Experimental Procedures for institutional abbreviations. See also Figure S4. Current Biology 2016 26, 2779-2786DOI: (10.1016/j.cub.2016.07.084) Copyright © 2016 Elsevier Ltd Terms and Conditions

Figure 4 Comparative Anatomy of Forelimb Contacts in Drepanosaurus and the Silky Anteater Cyclopes (A–J) Articular morphology of the bones of the Drepanosaurus (A–F) and Cyclopes forelimbs (G–J), illustrating osteological limitations to range of motion. Illustration of Cyclopes forelimb based on AMNH M 139228, YPM M 13499, and [42]. (A) Right glenoid fossa of GR 737 in lateral view, with strong dorsal and ventral margins limiting motion to protraction and retraction. (B) Right humerus of GR 737 in distal view, with strongly differentiated distal condyles. (C) Right radius and ulna of GR 737 in proximal view, with large and differentiated ulnar cotyles for reception of humeral condyles, restricting motion to flexion and extension. Also note the proximal process of the radius fitting into a notch in the ulna, restricting pronation and supination. (D) Right ulna (distal view) and right intermedium (proximal view of GR 737), with distinct ball-in-socket joint. (E) Left radius (distal view, mirrored) and left radiale (proximal view, mirrored) of GR 736, with screw-shaped articulation seemingly preventing any motion. (F) Right metacarpal II (distal view) of GR 738 and left manual ungual (proximal view, mirrored) of GR 697, illustrating well-differentiated condyles forming a hinge joint. (G) Right humerus of YPM M 13499 (distal view), showing well-differentiated condyles. (H) Right radius and ulna of YPM M 13499 (proximal view), showing well-differentiated cotyles. (I) Right manus of AMNH M 139228 in dorsal view, illustrating tight-fitting and motion-restricting articulations of metacarpophalangeal and interphalangeal joints of the expanded manual digit III. (J) Right penultimate phalanx of digit III of AMNH M 139228 in distal view, illustrating the well-differentiated distal condyles. Current Biology 2016 26, 2779-2786DOI: (10.1016/j.cub.2016.07.084) Copyright © 2016 Elsevier Ltd Terms and Conditions