Sed by deformation and a thick covering of scales. The ossified radius of M. pelikani first appears as a featureless, rectangular bone with no processes and flat, indistinct proximal and distal ends (Fig 19A). The first morphogenetic change to occur is the development of a distinctly waisted shaft with expanded proximal and distal ends (Fig 19B). Throughout ontogeny, the distal end of the radius is equal to or broader than the proximal qhw.v5i4.5120 end. The ends of the radius also become rounded (convex). During the next stage of morphogenesis, the medial surface of the distal end Actidione site slants inward to form the intermedial facet (Fig 19C). The radiale facet is not well developed in any specimens, though St.207 and NHMW1894_2399 may show preliminary differentiation of that region. Early in ontogeny, the ulna of M. pelikani also starts out undifferentiated, although the proximal end of the element is always at least slightly broader than the distal end (Fig 20A). As growth increases, the proximal end becomes much broader than the distal end (Fig 20B). Despite a Thonzonium (bromide)MedChemExpress Thonzonium (bromide) contrary report [1], the olecranon process becomes ossified during ontogeny. Preliminary development of that process is manifest as a medial slant in the proximal surface of the ulna (Fig 20C). As the olecranon process becomes more developed, the rounded, high portion that articulates with the lateral surface of the humerus becomes distinct from the level surface of the proximal end of the ulna (Fig 20D). A well-developed intermedial facet does not appear to form in M. pelikani, but an ulnare facet may be partially developed in NHMW1894_2399, which also exhibits a partially developed olecranon process. Pelvic Girdle and pnas.1408988111 Hindlimb. The ilium of M. pelikani forms relatively early in skeletal development [16]. At first, the ilium has a straight and relatively rectangular dorsal processPLOS ONE | DOI:10.1371/journal.pone.0128333 June 17,28 /Skeletal Morphogenesis of Microbrachis and HyloplesionTable 1. Features of the humerus during ontogeny in M. pelikani. specimen NHMW1983_32_66 MB.Am.809 CGH267 St.190 NHMW1894_2400 NHMW1983_32_59 NHMW1898_x_29 St.193 NHMW1983_32_50 52 NHMW1898_X_33 St.204 MB.Am.821.1? M1381 NHMW1899_III_8 MB.Am.827 St.199 St.208 NHMW1898_X_30 M1700 NHMW1983_32_64 74 CGH139 M1681 MB.Am.811 M1686 NHMW1983_32_72 MB.Am.825.1? M4883 MB.Am.823 CGH727 MB.Am.810.1? Amnh2557 M1694 MB.Am.814 M 4884 NHMW1894_2332 NHMW1983_32_49ab St.198 CGH34 CGH254 M3321-3322 CGH2098 NHMW1894-2364 M1688 CGH251 M4886 NHMW1983_32_67 MB.Am.822.1 = MB.Am.17 Sl 7 . 8.2 9.4 . . 10 11 13 13 13.2 14 14 14.5 14+ 15 15 15 15.5 15.7 15+ 15+ 16 16.5 17 17 17 17 17 17 17.5 17+ 18 19 19 19? 19 19.5 20? 20.1 22 22 25 26 26 27.5 28 Tl . 45 . 46 46 47+ 54 52 58? 68? 53 65 65 . . 67 . 70? 71 . 71 80 76+ . . . 74 71+ . 80 69 79 . . 77.5 79.5 . . 73 . 82 . . . 115 . . dor? dor dor or ven? ven and dor ? ven ? ant or post ant ven dor ven and ant post or ant ven and ant ant post vent to post ant or post ven or dor dor to ant ven to post ven ant ven ant to ven ant or post post post ventral ven ven and post ant or post ant ven post to ven post to ven ant or post ven to post post ant or post ven view dor ven post dor dor? Dpc N N N N N S,P N N N S,P ? S,P B S,P S,P N? N? S,P S,P S,P S,P L,D S,P S,P B L,P S,D B S,D S,P S,D L,D S,P S,D ? B L, D L, D L,D B,D L,P L,B L,D B,D L,D L, P? B Scs N N S N N S N B N S S? S B S S N? S S S S L L S S B L S ? L S S L L S ? ? L L L B L ? L L L L B Dcd N N N N N N N pDiff? N N N N N ? ? N? pDiff pDiff pD.Sed by deformation and a thick covering of scales. The ossified radius of M. pelikani first appears as a featureless, rectangular bone with no processes and flat, indistinct proximal and distal ends (Fig 19A). The first morphogenetic change to occur is the development of a distinctly waisted shaft with expanded proximal and distal ends (Fig 19B). Throughout ontogeny, the distal end of the radius is equal to or broader than the proximal qhw.v5i4.5120 end. The ends of the radius also become rounded (convex). During the next stage of morphogenesis, the medial surface of the distal end slants inward to form the intermedial facet (Fig 19C). The radiale facet is not well developed in any specimens, though St.207 and NHMW1894_2399 may show preliminary differentiation of that region. Early in ontogeny, the ulna of M. pelikani also starts out undifferentiated, although the proximal end of the element is always at least slightly broader than the distal end (Fig 20A). As growth increases, the proximal end becomes much broader than the distal end (Fig 20B). Despite a contrary report [1], the olecranon process becomes ossified during ontogeny. Preliminary development of that process is manifest as a medial slant in the proximal surface of the ulna (Fig 20C). As the olecranon process becomes more developed, the rounded, high portion that articulates with the lateral surface of the humerus becomes distinct from the level surface of the proximal end of the ulna (Fig 20D). A well-developed intermedial facet does not appear to form in M. pelikani, but an ulnare facet may be partially developed in NHMW1894_2399, which also exhibits a partially developed olecranon process. Pelvic Girdle and pnas.1408988111 Hindlimb. The ilium of M. pelikani forms relatively early in skeletal development [16]. At first, the ilium has a straight and relatively rectangular dorsal processPLOS ONE | DOI:10.1371/journal.pone.0128333 June 17,28 /Skeletal Morphogenesis of Microbrachis and HyloplesionTable 1. Features of the humerus during ontogeny in M. pelikani. specimen NHMW1983_32_66 MB.Am.809 CGH267 St.190 NHMW1894_2400 NHMW1983_32_59 NHMW1898_x_29 St.193 NHMW1983_32_50 52 NHMW1898_X_33 St.204 MB.Am.821.1? M1381 NHMW1899_III_8 MB.Am.827 St.199 St.208 NHMW1898_X_30 M1700 NHMW1983_32_64 74 CGH139 M1681 MB.Am.811 M1686 NHMW1983_32_72 MB.Am.825.1? M4883 MB.Am.823 CGH727 MB.Am.810.1? Amnh2557 M1694 MB.Am.814 M 4884 NHMW1894_2332 NHMW1983_32_49ab St.198 CGH34 CGH254 M3321-3322 CGH2098 NHMW1894-2364 M1688 CGH251 M4886 NHMW1983_32_67 MB.Am.822.1 = MB.Am.17 Sl 7 . 8.2 9.4 . . 10 11 13 13 13.2 14 14 14.5 14+ 15 15 15 15.5 15.7 15+ 15+ 16 16.5 17 17 17 17 17 17 17.5 17+ 18 19 19 19? 19 19.5 20? 20.1 22 22 25 26 26 27.5 28 Tl . 45 . 46 46 47+ 54 52 58? 68? 53 65 65 . . 67 . 70? 71 . 71 80 76+ . . . 74 71+ . 80 69 79 . . 77.5 79.5 . . 73 . 82 . . . 115 . . dor? dor dor or ven? ven and dor ? ven ? ant or post ant ven dor ven and ant post or ant ven and ant ant post vent to post ant or post ven or dor dor to ant ven to post ven ant ven ant to ven ant or post post post ventral ven ven and post ant or post ant ven post to ven post to ven ant or post ven to post post ant or post ven view dor ven post dor dor? Dpc N N N N N S,P N N N S,P ? S,P B S,P S,P N? N? S,P S,P S,P S,P L,D S,P S,P B L,P S,D B S,D S,P S,D L,D S,P S,D ? B L, D L, D L,D B,D L,P L,B L,D B,D L,D L, P? B Scs N N S N N S N B N S S? S B S S N? S S S S L L S S B L S ? L S S L L S ? ? L L L B L ? L L L L B Dcd N N N N N N N pDiff? N N N N N ? ? N? pDiff pDiff pD.