Supplemental Information. Extreme Modification of the Tetrapod Forelimb. in a Triassic Diapsid Reptile

Current Biology, Volume 26 Supplemental Information Extreme Modification of the Tetrapod Forelimb in a Triassic Diapsid Reptile Adam C. Pritchard, Alan H. Turner, Randall B. Irmis, Sterling J. Nesbitt, and Nathan D. Smith

Supplemental Figure Legends FIG S1. Line drawings of the right forelimb of the holotype specimen of Drepanosaurus unguicaudatus (MCSNB 5728) with homology assessment of A) Pinna [S1] and B) Renesto [S2] and Renesto et al. [S3]. Related to Figure 1. FIG S2. Drepanosaurid forelimb bones from the Upper Triassic Chinle Formation. Right scapulocoracoid (glenoid fossa) of Drepanosaurus (GR 737) in A) posterior and B) lateral views. C) Glenoid region of the drepanosaurid pectoral girdle from the Coelophysis Quarry (GR 113) in anteroventral view. D) Right humerus of Drepanosaurus (GR 740) in anterior view, with focus on exposed distal cross-section. 3D reconstruction of the right ulna of Drepanosaurus (GR 737) in E) medial and F) posterior views. 3D reconstruction of the right radius of Drepanosaurus (GR 737) in G) medial and H) posterior views. 3D reconstruction of right intermedium, ulnare, and distal carpal complex of Drepanosaurus (GR 737) in I) palmar and J) dorsal views. Left radiale of Drepanosaurus (GR 736) in K) palmar and J) dorsal views. The scalebar for E, F, G, H, I, and J is found in the center of the figure. Abbreviations: cl, clavicle; dc, distal carpal ossification; di, distal tab of radiale; dl, dorsal lip of glenoid fossa; dp, deltopectoral crest; dt, distal tuberosity of radius; ft, tubercle for forearm flexors; ga, gap between scapulocoracoid and clavicle; im, intermedium; po, post-axial articular facet of radiale; pr, proximal articular surface of radiale; pt, proximal tuberosity of radius; rf, facet for radial condyle of humerus; tr, trabeculae; ue, ulnare; vl, ventral lip of glenoid fossa. Related to Figure 2. FIG S3. Second manual unguals of Drepanosaurus from the Upper Triassic Hayden Quarry. Right ungual (GR 712) in A) medial, B) dorsal, and C) palmar views. Left ungual (GR 697) in D) medial and E) proximal views. Abbreviations: ex, extensor surface; fl, flexor tubercle; ft, insertion points of flexor tendons; kg, groove for keratin sheath; pc, proximal articular cotyle; pot, post-axial tuberosity; prt, preaxial tuberosity. Related to Figure 2. FIG S4. Strict consensus results of parsimony analyses run in TNT 1.1 [S58]. A) included the fragmentary specimens GR 113 and the holotype of Dolabrosaurus aquatilis. B) excluded these fragmentary taxa. The latter is reproduced in Figure 3 of the main text. Numbers above branches indicate Bremer support values, whereas numbers below branches indicate frequency differences resulting from a Jackknife analysis. Related to Figure 3.

Specimen # Identification GR 665 distal carpal complex GR 666 distal carpal complex GR 667 distal carpal complex GR 668 distal carpal complex GR 669 distal carpal complex GR 670 distal carpal complex GR 671 distal carpal complex GR 672 distal carpal complex GR 673 distal carpal complex GR 674 distal carpal complexes (2), proximal radius GR 675 drepanosaurid ICB, proximal radius, partial MC II, fragments GR 740 humerus, proximal; atlantal arch? GR 676 humerus, distal GR 677 humerus, distal GR 678 humerus, distal condyles GR 679 intermedium fused to distal carpal complex GR 680 intermedium fused to distal carpal complex GR 681 intermedium fused to distal carpal complex GR 682 intermedium fused to distal carpal complex GR 683 intermedium fused to distal carpal complex GR 684 intermedium fused to distal carpal complex; intermedium, distal, fused to distal carpal complex; distal carpal complexes (3), caudal vertebrae (3), partial dorsal vertebra, fragment GR 685 intermedium, distal, fused to distal carpal complex GR 686 intermedium, distal, fused to distal carpal complex GR 687 intermedium, distal, fused to distal carpal complex GR 688 intermedium, distal, fused to distal carpal complex GR 689 intermedium, distal, fused to distal carpal complex GR 690 intermedium, distal, fused to distal carpal complex GR 691 intermedium, distal, fused to distal carpal complex GR 739 intermedia, distal, fuseed to distal carpal complexes (3) GR 692 intermedium, fragmentary GR 693 intermedium, proximal GR 694 manual ungual (small) GR 695 manual ungual (small)

GR 741 manual ungual (small) GR 696 GR 697 GR 698 GR 699 GR 700 GR 701 GR 702 GR 703 GR 704 GR 705 GR 706 GR 707 GR 708 GR 709 GR 710 GR 711 GR 712, ungual (small) GR 713 manual unguals (2) GR 714 manual unguals (2) GR 715 metacarpal II GR 716 metacarpal II GR 717 metacarpal II GR 718 metacarpal II GR 719 metacarpal II GR 720 metacarpal II GR 721 metacarpal II GR 722 metacarpal II GR 738 metacarpal II GR 723 metacarpal II, distal GR 724 metacarpal II, partial GR 725 metacarpal II, partial GR 726 metacarpal II, partial GR 727 metacarpal II, proximal GR 728 metacarpal II, proximal GR 729 radius GR 730 radius

GR 742 GR 731 GR 732 GR 733 GR 734 GR 735 GR 736 GR 737 radius, proximal; 4 bone fragments ulna ungual, partial ungual, partial ungual, partial ungual, proximal articulation - Badly crushed left humerus with partially preserved head and ulnar condyle - Left humeral fragment with radial condyle - Left radius - Proximal articulation of left ulna, preserving two cotylar surfaces. - Left radiale. - Proximal portion of left second metacarpal. - Second manual ungual articulated to distal end of second metacarpal. - Complete phalanx? in two pieces. - 3 distal phalangeal fragments, preserving 3 ginglymoid articular fragments. - Distal end of flattened metacarpal? - Dorsal vertebra with fused ribs. - Over a dozen unidentifiable bone fragments. - Glenoid fossa of right scapulacoracoid - Distal end of right humerus. - Right radius. - Right ulna. - Proximal articular surface of right radiale. - Post-axial articular surface of right radiale. - Right intermedium, ulnare, and distal carpal articulated. - Proximal portion of right second metacarpal. - Right second manual ungual articulated with distal end of second metacarpal. - Distal end of small, flattened metacarpal? - 2 proximal metacarpals. - Caudal centrum fragment. - Small bone fragments.

Supplemental Table Legends TABLE S1. All specimens identified as Drepanosaurus sp. from the Hayden Quarry site. All specimens listed are field numbers of specimens accessioned with the Ruth Hall Museum of Paleontology. Related to Figure 2.

Supplemental Experimental Procedures SUPPLEMENTARY APPENDIX 1. Past hypotheses for the homologies of the Drepanosaurus forelimb. Pinna [S1] first described the Drepanosaurus unguicaudatus holotype and presented a hypothesis for the homologies of its forelimb bones (Fig. S1; [S1 3]). Pinna hypothesized that both the left and right forelimbs were disarticulated in an identical way. The clavicle and interclavicle were considered to be massive and robust, whereas they identified ambiguously in the subsequent hypotheses. Pinna [S4,5] reiterated this hypothesis. Renesto [S2] was the first to suggest that the forelimb in the Drepanosaurus holotype was still in articulation. He argued that the elements identified by Pinna as the clavicle and interclavicle were actually the articulated scapulocoracoid. The centrally placed elements identified as the scapula and coracoid by Pinna were reidentified as bones of the forearm. The hourglass-shaped bone described as the scapula by Pinna was reidentified as a radius by Renesto. However, the massive and crescent-shaped bone identified as the coracoid by Pinna proved more difficult. Renesto [S2] provided two hypotheses for the crescent-shaped bone. First, he suggested that it might represent an enormous process of the radius [S2]: 254). Under this hypothesis, the slender complex of bones positioned distal to the crescent-shaped element are identified as a single ulnar ossification. However, he questioned why both the left and right ulnae would be displaced from the humerus in the same way. He postulated that the relative hypertrophy of the radius might have displaced the ulnae from their articulation with the humerus [S2]: 254). He noted that this hypothesis would preclude the possibility of pronation and supination of the forelimb. Renesto s second hypothesis identified the crescent-shaped bone as a bizarrely shaped ulna (S1; [S2,3]. Based on that identification, he suggested that there were two bones distal to the crescent. These he suggested as the?ulnare and?intermedium ([S2]: 255. He considered this hypothesis problematic, noting that the radioulnar contact in the Drepanosaurus holotype resembled a suture, which would also preclude pronation and supination albeit in a very different way from the homologies suggested in Renesto s first hypothesis. Senter [S6]) followed this hypothesis in developing characters for his phylogenetic analysis of drepanosaurs and other diapsids. He also considered the elongation of the carpals in Drepanosaurus to be homologous to the subtly elongated ulnare and intermedium in Megalancosaurus preonensis, a comparison that Renesto [S2,3] did not make. Renesto et al. [S3]) reviewed the record of drepanosauromorphs. He redescribed the forelimb of the Drepanosaurus holotype, offering two hypotheses for the forelimb bone homologies (Fig. S1B). The first hypothesis was identical to the second hypothesis offered by Renesto [S2], with the crescent-shaped bone identified as an expanded ulna. The second hypothesis of Renesto et al. ([S3] suggested that the crescent-shaped bone was an accessory ossification, which is possibly the more feasible option [S3]: 4). Under this hypothesis, the accessory ossification would meet an elongate, slender ulna distally. SUPPLEMENTARY APPENDIX 2. Geologic age of the Hayden Quarry specimens & the holotype of Drepanosaurus. Hayden Quarry All specimens described here come from the Hayden Quarry (HQ), a series of closely associated localities in the Petrified Forest Member of the Chinle Formation of northern New Mexico, U.S.A., consisting of three paleochannels (in ascending stratigraphic order: H4, H2, H3). A U-Pb radioisotopic date from H2 indicates a maximum depositional age of 211.9 ± 0.7 Ma, suggesting a middle Norian age [S7]. Holotype The type specimen of Drepanosaurus unguicaudatus was collected from the Calcare di Zorzino (Zorzino Limestone) of the Aralalta Group in Lombardy, northern Italy [S1,8]. The lack of ammonoid fossils and/or radioisotopic dates means that the age of this unit is not well constrained. Palynomorphs from the Calcare di Zorzino and correlative units [S9,10] indicate a Norian age given the presence of the index taxon Granuloperculatipollis rudis [S11]. The lack of Microreticulatisporites fuscus, which is present in overlying strata [S9,10], suggests that the Calcare di Zorzino is not Alaunian in age [S11], which would make it no younger than ~216 Ma [S12]. However, the lack of a single taxon is generally not a strong biostratigraphic argument. Conodonts from the overlying Argillite di Riva di Solto [S13] also provide a minimum age constraint. The presence of Misikella hernsteini in the upper Argillite di Riva di Solto [S13] 1

indicates that the Calcare di Zorzino cannot be uppermost Norian in age, because the Tethyan first appearance datum of that conodont species is during the late Norian, ~210-212 Ma [S14 16]. Thus, conservatively, the Calcare di Zorzino could be as old as ~227 Ma (base of the Norian), or as young as ~210 Ma (upper Norian). Further east in Friuli, northern Italy, are outcrops of the Dolomia di Forni, which shares with the Calcare di Zorzino the presence of the drepanosaurid Megalancosaurus preonensis, archosauromorph Langobardisaurus pandolfii, and pterosaur Eudimorphodon ranzii [S8,17]. The Dolomia di Forni preserves the conodont taxon Mockina (Epigondolella) slovakensis, and possibly M. (E.) bidentata [S18,19]; discussed in [S17], but both of these species have long biostratigraphic ranges from the middle Norian to the lower Rhaetian in the Tethys region [S15,16,16]. Thus, the co-occurrence of the aforementioned vertebrate taxa in the Dolomia di Forni does not help constrain the age of the Calcare di Zorzino other than to suggest that a middle Norian age is slightly more likely than a lower Norian age. SUPPLEMENTARY APPENDIX 3. µct scan parameters and CT reconstruction methodology. Prior to preparation, one of the articulated forelimbs (GR 737) was µct scanned at the American Museum of Natural History using a GE Phoenix Vtome xs model CT scanner at a slice thickness resolution of.03996 millimeters for a total of 1400 slices (170 kv, 110 µa). Segmentation of CT data and generation of the 3D surface reconstructions of individual forelimb bones were made in Avizo 7.0 (FEI Software). SUPPLEMENTARY APPENDIX 4. Parameters of Phylogenetic Analysis Museum Abbreviations (for specimen identification) AMNH American Museum of Natural History (New York, NY, U.S.A.) CMNH Carnegie Museum of Natural History (Pittsburgh, PA, U.S.A.) GR Ruth Hall Museum of Paleontology (Abiquiu, NM, U.S.A.) MCSN Museo Civico di Storia Naturali Milano (Milano, Italy) MCSNB Museo Civico di Scienze Naturali Enrico Caffi (Bergamo, Italy) MFSN Museo Friulano di Storia Naturale (Udine, Italy) MNHN Muséum National d Histoire Naturelle (Paris, France) MPUM Museo di Paleontologia Università di Milano (Milano, Italy) NHMUK Natural History Museum of the United Kingdom (London, UK) PIMUZ Paleontological Institut und Museum (Zürich, Switzerland) SAM Iziko Museum (Cape Town, South Africa) SMNS Staaliches Museum für Naturkunde Stuttgart (Stuttgart, Germany) UA Université d Antannanarivo (Antannanarivo, Madagascar) USNM United States National Museum of Natural History (Washington, DC, U.S.A.) WMsN Westfäliches Museum für Naturkunde, Münster (Münster, Germany) Taxon List Petrolacosaurus kansensis [S20]. Claudiosaurus germaini MNHN MAP 1; SAM K8263, K8266; [S21,22]. Thadeosaurus colcapani MNHN MAP 360; [S21,22]. Hovasaurus boulei MNHN MAP 336; [S21,23]. Protorosaurus speneri USNM 442453; SMNS cast of WMsN P 47361; [S24]. Azendohsaurus madagaskarensis Hundreds of specimens accessioned with Université d Antannanarivo. Forelimb codings primarily based on UA 7-16-99-607. Macrocnemus bassanii MCSN BES SC 111, V 457; PIMUZ T/2472, 2477, 4355, 4822. Tanystropheus longobardicus MCSN BES SC 265, 1018, V 3730; PIMUZ T/1277, T/2819; 56. Saurosternon bainii NHMUK 1234, 1235; [S25]. Shinisaurus crocodilurus [S26,27]. Sphenodon punctatum [S28 34] Hypuronector limnaios AMNH FARB 1721, 7759; [S35]. Vallesaurus cenensis MCSNB 4751; [S36]. Dolabrosaurus aquatilis CMNH 28589; [S37]. 2

Megalancosaurus preonensis MFSN 1721; MPUM 6008, 8437;[S3,38]. Drepanosaurus unguicaudatus MCSNB 5728; [S3]. GR 113 Includes all drepanosaurid material preserved on a small block of matrix from the Coelophysis Quarry. Initially described by [S39]. Character List This matrix is a modification of Pritchard et al. [S40] and its subsequent expansion for Nesbitt et al. [S41]. The matrix is publicly available as Project 2495 on Morphobank (www.morphobank.org). Characters describing the ingroup relationships of drepanosaurids have been integrated (see below). References to characters from Renesto et al. [S3] refer specifically to the novel character set developed to assess the ingroup relationships of Drepanosauromorpha, the results of which are presented on pages 55 through 59 of that text. The.tnt file containing this data matrix is available as Project 2495 on Morphobank (www.morphobank.org). 1. Premaxilla, posterodorsal process (=maxillary process, = subnarial process): absent, such that premaxilla contributes a small ventral margin for the naris (0); posterodorsal process present, framing the posteroventral margin of the naris. (1). Character 4 in Pritchard et al. [S40] and Nesbitt et al. [S41]. Derived from similarly informative characters in Benton [S42], Gauthier et al. [S43], Rieppel [S44], DeBraga and Rieppel [S45], Jalil [S46], Merck [S47], Dilkes [S48], Müller [S49], and Nesbitt [S50]. 2. Lacrimal, facial contribution: forms a portion of lateral surface of the face, reaching anteriorly to the external naris (0); forms a portion of the lateral surface of the face, but does not reach naris (1); limited to orbital margin (2). Character 11 in Pritchard et al. [S40] and Nesbitt et al. [S41]. Derived from similarly informative characters in Gauthier [S51], Benton [S42], Gauthier et al. [S52], Benton and Allen [S53], DeBraga and Rieppel [S45], Jalil [S46], Merck [S47], Dilkes [S48], Müller [S49], and Conrad [S54]. ORDERED. 3. Frontals, degree of fusion: (0) unfused (suture patent), (1) fused in the midline. Character 14 in Pritchard et al. [S40] and Nesbitt et al. [S41]. Derived from similarly informative characters in Benton [S42], Gauthier et al. [S52], and Merck [S47]. 4. Frontal, shape of contact with parietal in dorsal view: (0) roughly straight in transverse plane; (1) frontal exhibits posterolateral processes, forming anteriorly curved U-shaped contact. Character 16 in Pritchard et al. [S40] and Nesbitt et al. [S41]. Derived from similarly informative characters in Benton and Allen [S53], Merck [S47], and Müller [S49]. 5. Postorbital, medial contact with frontal and parietal: (0) present, (1) absent with postfrontal fitted in between. Character not included in Pritchard et al. [S40] and Nesbitt et al. [S41]. Derived from similarly informative characters in Gauthier et al. [S52], Dilkes [S48], and Müller [S49]. 6. Parietals, degree of fusion: (0) unfused (patent suture), (1) fused at midline. Character 19 in Pritchard et al. [S40] and Nesbitt et al. [S41]. 3

Derived from similarly informative characters in Benton [S42], Gauthier et al. [S52], Merck [S47], Dilkes [S48], and Müller [S49]. 7. Parietal, dorsal surface: parietal skull table flattened (0); dorsal exposure of parietal forms a raised margin, elevated above lateral excavation for jaw adductor musculature (1); thin, blade-like sagittal crest (2). Character 20 in Pritchard et al. [S40] and Nesbitt et al. [S41]. Derived from similarly informative characters in Gauthier et al. [S52], DeBraga and Rieppel [S45], Dilkes [S48], Müller [S49], and Nesbitt [S50]. ORDERED. 8. Postorbital, posterior process, length: (0) contributes to lateral margin of supratemporal fenestra, but does not reach the posterior aspect of that opening; (1) contributes to the entire length of the supratemporal fenestra, reaching the posterior aspect of that opening. Modified from Character 28 in Pritchard et al. [S40] and Nesbitt et al. [S41]. Derived from similarly informative characters in Gauthier et al. [S52], Benton and Allen [S53], DeBraga and Rieppel [S45], Merck [S47], and Müller [S49]. 9. Squamosal, size of descending process: forms massive flange that covers the quadrate entirely in lateral view (0); anteroposteriorly slender (1). Character 34 in Pritchard et al. [S40] and Nesbitt et al. [S41]. Derived from similarly informative characters in Gauthier [S51], Benton [S42], Gauthier et al. [S52], Rieppel [S44], DeBraga and Rieppel [S45], and Merck [S47]. 10. Squamosal, posterior lamina: (0) posterior lamina present, covering much of posterior aspect of quadrate; (1) posterior lamina absent, posterior aspect of quadrate exposed in occipital view. Modified from Character 35 in Pritchard et al. [S40] and Nesbitt et al. [S41]. Derived from similarly informative characters in DeBraga and Rieppel [S45] and Müller [S49]. 11. Quadratojugal: (0) present, (1) absent. Character 38 in Pritchard et al. [S40] and Nesbitt et al. [S41]. Derived from similarly informative characters in Benton [S42], Gauthier et al. [S52], Benton and Allen [S53], Merck [S47], Dilkes [S48], and Müller [S49]. 12. Quadrate, shape of posterior margin: straight, vertical posterior margin (0); concave, excavated posterior margin (1). Character 43 in Pritchard et al. [S40] and Nesbitt et al. [S41]. Derived from similarly informative characters in Gauthier [S51], Benton [S42], Gauthier et al. [S52], Rieppel [S44], DeBraga and Rieppel [S45], Jalil [S46], Merck [S47], and Müller [S49]. 13. Quadrate, lateral flange (=tympanic crest): (0) absent, quadrate has no lateral expansion; (1) present, flattened lateral crest projects from lateral surface of quadrate. Character 43 in Pritchard et al. [S40] and Nesbitt et al. [S41]. Derived from similarly informative characters in Gauthier et al. [S52], Jalil [S46], Merck [S47], Dilkes [S48], and Müller [S49]. 14. Stapes, foramen within shaft: (0) present, (1) absent. Character 77 in Pritchard et al. [S40] and Nesbitt et al. [S41]. Derived from similarly informative characters in Benton [S42], Gauthier et al. [S43], Laurin [S55], and Merck [S47]. 15. Angular, exposure on lateral mandibular surface: (0) dorsoventrally broad, (1) limited to dorsoventrally narrow, posteroventral sliver by dentary and surangular. Character 82 in Pritchard et al. [S40] and Nesbitt et al. [S41]. Derived from similarly informative characters in Gauthier et al. [S52], Jalil [S46], Merck [S47], and Müller [S49]. 4

16. Angular, exposure on lateral mandibular surface: (0) terminates anterior to the glenoid, (1) extends to the glenoid. Character 83 in Pritchard et al. [S40] and Nesbitt et al. [S41]. Derived from similarly informative characters in Gauthier [S51], Gauthier et al. [S52], and Merck [S47]. 17. Retroarticular process: (0) present as extension of articular and adjacent bones posterior to quadrate articulation, (1) absent. Character 86 in Pritchard et al. [S40] and Nesbitt et al. [S41]. Derived from similarly informative characters in Benton [S42], Gauthier et al. [S52], Jalil [S46], Merck [S47], Dilkes [S48], Müller [S49], and Senter [S6]. 18. Marginal dentition, implantation: (0) teeth situated in shallow groove (pleurodonty + thecodonty), (1) teeth on dorsal surface of tooth-bearing bones (acrodonty). Character 94 in Pritchard et al. [S40] and Nesbitt et al. [S41]. Derived from similarly informative characters in Benton [S42], Gauthier et al. [S52], Dilkes [S48], and Müller [S49]. 19. Marginal dentition, lingual surface: (0) teeth walled by minimal lingual wall, (1) no lingual wall (=pleurodonty). Character 95 in Pritchard et al. [S40] and Nesbitt et al. [S41]. Derived from similarly informative characters in Benton [S42], Gauthier et al. [S52], Dilkes [S48], and Müller [S49]. 20. Cervical ribs, anterior process: absent (0); present (1). Character 105 in Pritchard et al. [S40] and Nesbitt et al. [S41]. Derived from similarly informative characters in Benton [S42], Gauthier et al. [S43], Rieppel [S44], DeBraga and Rieppel [S45], Jalil [S46], Merck [S47], Dilkes [S48], and Müller [S49]. 21. Cervical vertebrae, intercentra: present (0); absent (1). Character 106 in Pritchard et al. [S40] and Nesbitt et al. [S41]. Derived from similarly informative characters in Benton [S42], Gauthier et al. [S43], Rieppel [S44], DeBraga and Rieppel [S45], Merck [S47], Dilkes [S48], and Nesbitt [S50]. 22. Anterior post-axial cervical vertebrae, shape of anterior margin of neural spine in lateral view: (0) straight and linear, (1) anterodorsal process present forming an anterior notch. Character 115 in Pritchard et al. [S40] and Nesbitt et al. [S41]. Derived from similarly informative characters in Benton [S42], Jalil [S46], Merck [S47], Dilkes [S48], and Müller [S49]. 23. Dorsal vertebrae, intercentra: (0) present, (1) absent. Character 128 in Pritchard et al. [S40] and Nesbitt et al. [S41]. Derived from similarly informative characters in Benton [S42], Gauthier et al. [S43], Benton and Allen 80, Jalil [S46], Merck [S47], Dilkes [S48], and Müller [S49]. 24. Dorsal vertebra, accessory zygosphene-zygantrum articulations: (0) absent, (1) present. Character 130 in Pritchard et al. [S40] and Nesbitt et al. [S41]. Derived from similarly informative characters in Gauthier et al. [S52], Jalil [S46], Merck [S47], and Müller [S49]. 25. Second sacral rib, shape: (0) rib is a single unit, (1) rib bifurcates posteriorly into anterior and posterior processes. Character 131 in Pritchard et al. [S40] and Nesbitt et al. [S41]. Derived from similarly informative characters in Gauthier et al. [S52], Merck 75, Dilkes [S48], and Müller [S49]. 5

26. Caudal vertebrae, autotomic septa within the centrum: (0) absent, (1) present. Character 135 in Pritchard et al. [S40] and Nesbitt et al. [S41]. Derived from similarly informative characters in Gauthier et al. [S52], and Merck [S47]. 27. Chevron, shape of hemal spine: (0) tapers along its proximodistal length; (1) broadens slightly along its length; (2) broadens distally, forming inverted T shape; (3) broadens distally, forming subcircular expansion. Character 136 in Pritchard et al. [S40] and Nesbitt et al. [S41]. Derived from similarly informative characters in Benton [S42], Merck [S47], and Müller [S49]. 28. Interclavicle, shape of anterior surface anteromedial to clavicular articulations: (0) smooth margin, (1) prominent notch in margin. Character 143 in Pritchard et al. [S40] and Nesbitt et al. [S41]. Derived from similarly informative characters in Merck [S47], Dilkes [S48], and Müller [S49]. 29. Humerus, ectepicondyle, morphology of radial nerve groove: groove has no roof (0); groove roofed, forming ectepicondylar foramen (1). Character 151 in Pritchard et al. [S40] and Nesbitt et al. [S41]. Derived from similarly informative characters in Gauthier [S51], Benton [S42], Gauthier et al. [S43,52], Rieppel [S44], Benton and Allen [S53], Jalil [S46], and Dilkes [S48]. 30. Humerus, entepicondyle morphology: (0) foramen absent, (1) foramen present. Character 153 in Pritchard et al. [S40] and Nesbitt et al. [S41]. Derived from similarly informative characters in Jalil [S46], Dilkes [S48], Merck [S47], and Müller [S49]. 31. Ulna, ossified olecranon process: present (0); absent (1). Character 157 in Pritchard et al. [S40] and Nesbitt et al. [S41]. Derived from similarly informative characters in Benton [S42], DeBraga and Rieppel [S45], Merck [S47], and Müller [S49]. 32. Medial centrale of hand: absent (0); present (1). Character 158 in Pritchard et al. [S40] and Nesbitt et al. [S41]. Derived from similarly informative characters in Gauthier [S51], Benton and Allen [S53], Jalil [S46], and Dilkes [S48]. 33. Distal carpal five: absent (0); present (1). Character 159 in Pritchard et al. [S40] and Nesbitt et al. [S41]. Derived from similarly informative characters in Merck [S47] and Nesbitt [S50]. 34. Ulnare and intermedium, perforating foramen between elements: (0) present, (1) absent. Character 161 in Pritchard et al. [S40] and Nesbitt et al. [S41]. Derived from similarly informative characters in Benton [S42] and Merck [S47]. 35. Puboischiadic plate, fenestration: no fenestra (0); thyroid fenestra within plate (1). Character 163 in Pritchard et al. [S40] and Nesbitt et al. [S41]. Derived from similarly informative characters in Benton [S42], Gauthier et al. [S52], Rieppel [S44], Benton and Allen [S53], DeBraga and Rieppel [S45], Jalil [S46], Merck [S47], Dilkes [S48], and Müller [S49]. 36. Ilium, long axis of orientation for iliac blade in lateral view: horizontal orientation (0); posterodorsal orientation (1); anterodorsal orientation (2). Character 164 in Pritchard et al. [S40] and Nesbitt et al. [S41]. Derived from similarly informative characters in Gauthier et al. [S52], Merck [S47], and Renesto et al. [S3]. 6

37. Astragalus-calcaneum, extent of co-ossification: (0) present as distinct ossifications, (1) co-ossified. Character 185 in Pritchard et al. [S40] and Nesbitt et al. [S41]. Derived from similarly informative characters in Benton [S42], Gauthier et al. [S52], Jalil [S46], Merck [S47], Müller [S49], and Renesto et al. [S3]. 38. Astragalus-calcaneum, perforating foramen at contact: (0) present, positioned between astragalus and calcaneum, (1) absent, no foramen evident between astragalus and calcaneum. Character 186 in Pritchard et al. [S40] and Nesbitt et al. [S41]. Derived from similarly informative characters in Benton and Allen [S53] and Merck [S47]. 39. Distal tarsal four, morphology of proximal contact: (0) smooth contact surface for proximal tarsals, (1) prominent process for contact with proximal tarsals. Character 191 in Pritchard et al. [S40] and Nesbitt et al. [S41]. Derived from similarly informative characters in Gauthier et al. [S52], DeBraga and Rieppel [S45], Merck [S47], Dilkes [S48], and Müller [S49]. 40. First distal tarsal: present (0); absent (1). Character 193 in Pritchard et al. [S40] and Nesbitt et al. [S41]. Derived from similarly informative characters in Gauthier [S51], Benton [S42], Gauthier et al. [S43], Rieppel [S44], Benton and Allen [S53], DeBraga and Rieppel [S45], Jalil [S46], Dilkes [S48], Müller [S49], and Nesbitt [S50]. 41. Second distal tarsal: present (0); absent (1). Character 194 in Pritchard et al. [S40] and Nesbitt et al. [S41]. Derived from similarly informative characters in Gauthier [S51], Benton [S42], Gauthier et al. [S52], Benton and Allen [S53], Dilkes [S48], and Nesbitt [S50]. 42. Fifth distal tarsal: present (0); absent (1). Character 195 in Pritchard et al. [S40] and Nesbitt et al. [S41]. Derived from similarly informative characters in Gauthier [S51], Benton [S42], Gauthier et al. [S43], Rieppel [S44], DeBraga and Rieppel [S45], Jalil [S46], Merck [S47], and Müller [S49]. 43. Metatarsal five, shape of proximal postaxial margin: smooth, curved margin (0); prominent, pointed process (outer process sensu [S56]) (1). Character 196 in Pritchard et al. [S40] and Nesbitt et al. [S41]. 44. Cervical vertebrae, hypapophysis: absent, ventral surface of centrum unexpanded posteroventrally (0); posteroventral surface of centrum exhibits massive, posteroventrally projecting crest (1). Derived from character 4 in Renesto et al. [S3]. 45. Terminal caudal vertebra(e): similar in morphology to other posterior caudals (0); modified into clawlike element (1). Derived from character 37 in Senter [S6] and character 40 in Renesto et al. [S3]. 46. Anterior chevrons, hemal spine morphology element forms single spine (0); element bifurcates ventrally (1). Derived from character 41 in Senter [S6] and character 37 in Renesto et al. [S3]. Taxa coded as 0 for character 32 are coded as inapplicable ( - ) for character 33. 47. Anteriormost chevrons, hemal spine morphology: bifid spines remain separate ventrally (0); bifid spines recontact ventrally, forming foramen (1). Derived from character 41 in Senter [S6] and character 37 in Renesto et al. [S3]. 48. Posterior chevrons, proximal articulation: articulate intervertebrally (0); contact anteroventral margin of centrum (1). 7

Derived from character 39 in Renesto et al. [S3]. 49. Chevrons, proximal articular morphology: chevrons remain separate from centra (0); chevrons fuse to centra (1). NOVEL character. Describes the fusion of the chevrons and caudal centra throughout the tail in all known drepanosaurs. Well-preserved examples of this condition include the holotypes of Vallesaurus cenensis (MCSNB 4751), Dolabrosaurus aquatilis (CMNH 28589), and Drepanosaurus unguicaudatus (MCSNB 5728). 50. Chevrons, hemal spine length: similar in length or shorter than caudal neural spines (0); substantially longer than caudal neural spines (1). Derived from character 40 in Senter [S6] and character 38 in Renesto et al. [S3]. 51. Caudal vertebrae, anterior neural spines: spines unexpanded dorsally (0); spines exhibit slender anterior/posterior projections, forming T-shape (1). Derived from character 36 in Senter [S6] and character 33 in Renesto et al. [S3]. 52. Anterior dorsal vertebrae, pedicel height: substantially shorter than respective centra (0); taller than respective centra (1). NOVEL character, describing the substantial height of the vertebral pedicels in Vallesaurus and drepanosauromorphs more derived than it. By contrast, the pedicels of the anterior dorsal vertebrae in Hypuronector (AMNH FARB 1721) and other diapsids in this analysis are shorter than their respective centra. 53. Anterior dorsal vertebrae, neural spine expansion: spines similar in morphology to posterior dorsal neural spines (0); spines dorsally broader anteroposteriorly than spine base (1); third dorsal spine anteroposteriorly expanded into hatchet shape (2). ORDERED. Derived from character 31 in Senter [S6] and character 9 in Renesto et al. [S3]. We have modified this character to accommodate and intermediate condition, in which the anterior dorsal neural spines exhibit a slight anteroposterior expansion at their dorsal tips, rather than the extreme expansion that produces the pseudonotarium condition of multiple fused neural spines (19). 54. Second manual ungual: similar in morphology to other manual unguals (0); substantially taller and more massive than other manual unguals (1). Derived from character 21 in Renesto et al. [S3]. Describes the extreme asymmetries in ungual size in Drepanosaurus unguicaudatus and the HQ fossils. We employ this character to homologize the enormous second ungual in MCSNB 5728 and those in the HQ sample. 55. Ulna, shape: similar to radius, with elongate shaft (0); flattened in pre-axial-post-axial plane, forming enormous crescent (1). Derived from character 18 in Renesto et al. [S3]. Describes the bizarre shape of the ulna in Drepanosaurus unguicaudatus (MCSNB 5728) and the HQ fossils. Note below that we do not employ a character to describe the extreme elongation of the ulnare and intermedium, as such 56. Radius, proximal tab: absent (0); prominent tab for articulation with ulna present (1). NOVEL character. Describes the postaxial proximal expansion of the proximal radial articular surface in Drepanosaurus. Although a number of Permo-Triassic diapsids exhibit an inflexion of the proximal radial surface (e.g., Trilophosaurus buettneri, TMM 31025-140; Azendohsaurus madagaskarensis, UA 7-16-99-607), no other taxon has developed the interlocking tab-slot mechanism seen in Drepanosaurus. 57. Scapula, curavture of long-axis of blade: blade directed dorsally (0); blade curves anterodorsally (1). Derived from character 44 in Senter [S6]. 58. Mid dorsal ribs, fusion to respective centra: fusion absent (0); fusion present (1). Derived from character 11 in Renesto et al. [S3]). 8

59. Calcaneum, lateral projection, ventral margin: margin is convex and continuous with the lateral margin of the projection (0); margin is concave, sharply angled relative to lateral margin of the projection (1). NOVEL character. Describes the characteristic ventral concavity of the lateral expansion of the calcaneum in drepanosaurids. 60. Chevrons, hemal spine curvature: spines roughly straight (0); spines convex anteriorly (1). Derived from character 141 of Dilkes [S48]. 61. Ulnare and intermedium, elongation: (0) longer proximodistally than in pre-axial-post-axial plane; (1) short proximodistally, equivalent in proximodistal and pre-axial-post-axial length. Derived from similarly informative characters in Merck [S47], Senter [S6], and Renesto et al. [S3]. 62. Third manual digit, phalangeal formula: (0) multiple phalanges, (1) single, non-ungual phalanx. Derived from similarly informative characters in Merck [S47] and Senter [S6]. 63. Dentary, contribution to lateral mandibular surface: (0) terminates at or near to posterior terminus of tooth row; (1) extends posteriorly to overlap coronoid; (2) extends well posterior to coronoid. ORDERED. Derived from similarly informative characters in Conrad [S54]. 64. Cervical ribs: present (0); absent (1). Derived from character 5 of Renesto et al. [S3]. 65. Pedal digit three (III), number of phalanges: four (0); three (1). Derived from character 28 of Renesto et al. [S3]. 66. Post-axial cervical vertebra, morphology of intervertebral articulations (for amphicoelous taxa): circular/elliptical articulations appressed to one another (traditional amphicoely) (0); saddle-shaped articulations (heterocoely) (1). NOVEL character. Describes the complex, saddle-shaped intervertebral articulations within the cervical region of drepanosauromorphs (e.g., [S57]. 68. Vertebrae, notochordal canal: present (0); absent (1). Derived from similarly informative characters in Gauthier [S51] (lepidosaur dataset), Gauthier et al. [S43], Laurin [S55], Merck [S47], Dilkes [S48], and Müller [S49]. 69. Humerus, distalmost end: (0) collinear with proximal shaft; (1) primary axis curves anteriorly relative to primary humeral shaft. NOVEL character. Describes the moderate angling of the humeral shaft in the Italian Drepanosaurus holotype and the Hayden Quarry humeri. 70. Palatine, anterior transverse expansion: (0) absent, producing anteriorly curved suborbital fenestrae; (1) present, producing anteriorly tapered suborbital fenestrae. Derived from similarly informative characters in Gauthier et al. [S52]. 71. Scapula & coracoid, position of glenoid fossa: at or near base of scapular blade 0); located far ventral of base of scapular blade 1). NOVEL character. Describes the distance between the base of the primary scapular blade and the glenoid fossa in Drepanosaurus unguicaudatus, the HQ Drepanosaurus, and GR 113. This character was not noted by Renesto et al. [S3], in which GR 113 was referred to Drepanosaurus sp. 72. Humerus, epicondyles, proximal origination: positioned distal to midshaft (0); positioned at/near midshaft (1). NOVEL character. We employ this character to describe the substantial differences in shape and robusticity between the humeri in early-diverging drepanosauromorphs and Drepanosaurus unguicaudatus. 9

The proximal humeral specimen from the Hayden Quarry (GR 740) suggests similarly robust epicondyles with a similar proximal origination to the holotype of Drepanosaurus unguicaudatus. 73. Supraneural ossification, bone growth positioned anterodorsal to anterior dorsal neural spines: absent (0); present (1). NOVEL character. It has been recognized that several drepanosauromorphs (Vallesaurus cenensis, Megalancosaurus preonensis, Drepanosaurus unguicaudatus) exhibit a prominent ossification anterodorsal to the neural spines of dorsal vertebrae 2 and 3. The homology and three-dimensional osteology of this structure remains poorly understood. As its identification is difficult in disarticulated skeletons, this character is coded only for taxa in which a well-preserved, articulated anterior trunk region is known. 74. Scapulacoracoid, glenoid fossa, construction: oriented posterolaterally, ventral margin extends posterior of dorsal margin (0); oriented laterally, ventral margin positioned directly underneath to dorsal margin (1). NOVEL character. Harris and Downs [S39] and Renesto et al. [S3]. noted that the long axis of the coracoid in GR 113 and Drepanosaurus unguicaudatus is verticalized, relative to the plesiomorphic, horizontalized coracoid in Hypuronector, Vallesaurus, and Megalancosaurus. In the former two taxa, this appears to result in the glenoid fossa becoming similarly verticalized, with a prominent dorsal margin completely overhanging the ventral margin. We employ this morphological feature to describe this character, as the fragmentary pectoral material available from the Hayden Drepanosaurus includes a verticalized glenoid fossa. 75. Scapula, blade, dorsoventral height-anteroposterior length (at base of blade) ratio: >.4 (0).4.25 (1).25 0 (2). ORDERED. Derived from similarly informative characters of Dilkes [S48], and Renesto et al. [S3]. We employ multiple ratio categories to describe the difference between the slender scapula of Hypuronector and the relatively longer scapulae in Vallesaurus, Megalancosaurus, and Drepanosaurus. Parameters of Phylogenetic Analysis To investigate the affinities of the HQ Drepanosaurus and develop hypotheses for forelimb evolution in Drepanosauromorpha, we developed a new phylogenetic analysis incorporating all named drepanosauromorphs and a number of non-drepanosauromorph diapsids 20 taxa, 75 characters). All analyses are run in TNT v. 1.1 [S58], employing the Traditional Search options including 10,000 replicates of Wagner trees (using random addition sequences), followed by tree bisection and reconnection (TBR) holding 10 trees per replicate. The best trees obtained at the end of the replicates were subjected to a final round of TBR branch swapping. We employed Rule 1 of Coddington and Scharff ([S59]) for collapsing zero-length branches. We employed the STATS.RUN TNT script to obtain the Consistency Index and Retention Index for all trees and the BREMER.RUN script for decay indices. The analysis presented in Fig. 4 recovered 7 most-parsimonious trees of 126 steps in length (CI = 0.659; RI = 0.817). We also ran a jackknife analysis (10,000 replicates, 20% character removal probability), the results of which are presented as GC values (frequency differences). The initial analysis included all taxa listed, including Dolabrosaurus aquatilis and GR 113, the most incomplete drepanosaur specimens. That analysis produced 7 most parsimonious trees of 126 steps found in 10,000 out of 10,000 replicates (strict consensus presented in Fig. S4A). The CI = 0.659 and RI = 0.817. For a second iteration of the analysis (the strict consensus of which is presented in Figure 3 of the main text), we excluded GR 113 and Dolabrosaurus aquatilis. The incomplete nature of these taxa makes the transitions in forelimb anatomy ambiguous between the internodes within Drepanosauromorpha in the first analysis. The results of this analysis were otherwise congruent with the first iteration. This analysis produced 7 most parsimonious trees of 126 steps found in 10,000 out of 10,000 replicates (strict consensus presented in Fig. S4B). The CI = 0.659 and RI = 0.817. References [S1] Pinna G. Drepanosaurus unguicaudatus, nuovo genere nuova specie di Lepidosauro del Trias Alpino (Reptilia). Atti Della Soc Ital Sci Nat 1980;121:181 92. 10

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