1 Supplementary Information 2 3 A new two-fingered dinosaur sheds light on the radiation of Oviraptorosauria 4 5 Funston, Gregory F., Chinzorig, Tsogtbaatar, Tsogtbaatar, Khishigjav, Kobayashi, 6 Yoshitsugu, Sullivan, Corwin, Currie, Philip J. 7 8 Contents 9 1. Expanded Diagnosis 10 2. Histological Results and Age Estimation 11 3. Expanded Statistical Methods 12 4. Phylogenetic Results 13 5. History of the Specimens 14 6. Referral of Specimens 15 7. Provenance of the Poached Specimens 16 8. Taphonomy of the Holotype 17 9. Table of age ranges 18 10. Measurements of Oksoko avarsan 19 11. Character List 20 12. Character States of Oksoko avarsan 21 13. Supplementary References 22 14. Supplementary Figures 23 1 24 1. Expanded Diagnosis 25 Oksoko avarsan can be distinguished from citipatiine oviraptorids by the enlarged 26 first manual digit and reduced second and third manual digits. It can be distinguished 27 from most heyuanniine oviraptorids by the presence of a cranial crest (Fig. S1). Two 28 heyuanniines are known which possess a cranial crest: Nemegtomaia barsboldi and Banji 29 long. In both of these taxa, the cranial crest is composed primarily of the nasals and 30 premaxilla, whereas in Oksoko avarsan the rounded, domed crest is composed primarily 31 of the nasals and frontals. 32 Two other oviraptorids possess similar cranial crests: Rinchenia mongoliensis and 33 Corythoraptor jacobsi, both of which are currently considered citipatiine oviraptorids. 34 The skull of Oksoko avarsan can be distinguished from Rinchenia mongoliensis 1 by the 35 position of the naris dorsal to the orbit; a proportionally greater contribution of the frontal 36 to the cranial crest; a longer tomial part of the premaxilla; a relatively smaller 37 infratemporal fenestra; and a non-interfingering contact between the jugal and 38 quadratojugal (Fig. S2). Postcranially, Oksoko avarsan differs from Rinchenia 39 mongoliensis in possessing a posteriorly concave axis; elongate, rather than plate-like 40 distal chevrons (Fig. S3); a more strongly everted acromion process of the scapula; and a 41 less dorsoventrally expanded ilium with an accessory brevis ridge (Fig. S4). 42 Unfortunately, the forelimb of Rinchenia is incompletely known, and its manus cannot be 43 compared to that of Oksoko. Oksoko avarsan can be distinguished from Corythoraptor 44 jacobsi 2 by a convex, rather than concave anterior surface of the premaxilla; an ovoid, 45 rather than slit-like naris; a relatively shorter neck composed of procoelous cervical 46 vertebrae with large epipophyses; a reduced forelimb with antebrachium subequal to 47 humerus; and by its short manus with an enlarged first digit and vestigial third digit. 48 These features are consistent between the ontogenetic stages of Oksoko avarsan, and it is 49 unlikely that the radical differences in the skull or forelimb are the result of individual 50 variation. Little is known about ontogenetic changes in the crests of oviraptorosaurs, but 51 evidence from juvenile Conchoraptor gracilis3 and embryonic Citipati osmolskae4 52 suggest that the presence of a crest and its constituent bones are consistent throughout 53 ontogeny. Norell et al.4 first suggested that crests may have been ontogenetic because 54 they were as yet unknown in small oviraptorids. The presence of well-developed cranial 55 crests in clearly juvenile Oksoko avarsan fills this gap and, alongside the small, crested 56 Banji long, argues against ontogenetic development of crests in oviraptorids. 57 58 59 2. Histological Results and Age Estimation 60 MPC-D 102/11—The femur and fibula differ in the degrees of secondary 61 remodeling, but both lack any lines of arrested growth. The femur (Fig. S5) is entirely 62 composed of primary fibrolamellar bone with no secondary osteons. Vasculature is 63 primarily arranged longitudinally, although there are some regions of reticular 64 vasculature. A zone of parallel-fibred bone occurs towards the periosteal surface of the 65 bone. This zone is similar to a growth mark described in a caenagnathid tibia from the 66 Horseshoe Canyon Formation of Alberta5, and likely represents the same phenomenon. 67 The fibula has considerably more secondary remodeling than the femur, but it is still 68 predominantly primary bone. On the lateral side, the cortex is mostly remodeled, except 69 for a region of primary bone near the periosteal surface that has numerous Sharpey’s 2 70 fibers (Fig. S6a). On the medial side, there is primary osteonal bone towards the 71 endosteal surface and avascular parallel-fibred bone near the periosteal surface. The 72 medullary cavity and endosteal lamellae are both well developed. Like the femur, there is 73 an annulus developed towards the periosteal surface that probably represents the first 74 growth mark. Based on these data, MPC-D 102/11 is best regarded as a young juvenile 75 approximately one year of age. 76 MPC-D 102/110.a—The fibula (Supplementary Fig. S5) is composed mostly of 77 primary fibrolamellar bone, but there are some secondary osteons on the medial side. 78 There is a high proportion of woven bone with dense, plump osteocyte lacunae (Fig. 79 S6b). The medullary cavity is small but has defined edges and in some places, there are 80 endosteal lamellae. There are no obvious zones of parallel-fibred bone or lines of arrested 81 growth. Towards the periosteal surface on the anterior side of the fibula there is a region 82 of reduced vasculature, but no obvious annulus is present and this zone cannot be traced 83 around the entire cortex. This may be incipient development of the annulus recorded in 84 the other individuals. It is unlikely that a growth mark has been obscured by secondary 85 remodeling because secondary osteons are sparse and primary bone is visible between 86 them. However, the sampling location may have affected the preservation of growth 87 marks. The predominance of primary bone and absence of a growth mark suggest this 88 individual is a young juvenile, but no age assessment can be made. 89 MPC-D 102/110.b—Two fragments of the fibula (Fig. S5) were sectioned and 90 both have similar histological texture. Neither fragment shows the medullary cavity, but 91 this may be because the samples were taken distally. Both are composed predominantly 92 of primary fibrolamellar bone, but each has some secondary osteons endosteally. 93 Vasculature is mostly longitudinal, but there are some small zones of reticular canals. 94 Near the periosteal surface there is a zone of avascular, parallel-fibred bone similar to that 95 in MPC-D 102/11. It likely represents the first growth mark, although no distinct rest line 96 is visible. Like MPC-D 102/11, this specimen was likely a young juvenile approximately 97 one year of age. 98 MPC-D 102/12—The fibula (Fig. S5) and a fragment of the femur were 99 sectioned. The fibula has more secondary remodeling, and therefore some of the growth 100 record has been erased (Fig. S6c). The medullary cavity is well formed and lined by 101 multiple generations of endosteal lamellae. Several other erosive cavities also excavate 102 the cortex; these are separated by trabeculae or endosteal lamellae. Vasculature is 103 longitudinally oriented, and towards the medial surface these canals are arranged into 104 circumferential rows. At least three lines of arrested growth are recorded on the medial 105 surface, but it is likely that more have been obscured by secondary remodeling and 106 expansion of the medullary cavity. 107 The femur exhibits less secondary remodeling, all of which is concentrated in a 108 vertical column extending perpendicular to the periosteal surface (Fig. S6d). The primary 109 bone in this column contains larger, more densely packed osteocyte lacunae, and well- 110 developed Sharpey’s fibers towards the periosteal surface (Fig. S6d). Accordingly, it 111 likely represents a zone of muscle insertion. A small strip of endosteal lamellae marks the 112 edge of the medullary cavity, indicating that the entire cortex is preserved. Vasculature 113 changes from predominantly reticular endosteally through plexiform towards a zone of 114 parallel-fibred bone about halfway through the cortex. A faint cement line is visible 115 within this zone of parallel-fibred bone, indicating that it represents a growth mark in the 3 116 form of an annulus. External to this annulus, vasculature is laminar and decreases towards 117 the periosteal surface. At least four more annuli are visible in the external part of the 118 cortex, and have decreased spacing periosteally. Whereas a zone of fibrolamellar osteonal 119 bone separates the first, second, and third annuli, the spaces between the third, fourth, and 120 fifth annuli are composed of parallel-fibred bone. This forms a continuous band of 121 parallel-fibred bone on the periosteal surface of the cortex. Although no distinct lines of 122 arrested growth can be distinguished in this area, this is likely the result of the light 123 colour of the bone and the reduced thickness of the slide. In any case, the dominance of 124 parallel-fibred bone at the periosteal surface indicates that this individual was growing 125 slowly6–10. The presence of five annuli and the low growth rate suggest that this 126 individual was an adult at least five years old and was approaching maximum body size. 127 128 129 3. Expanded Statistical Methods 130 To trace the patterns of digit and limb reduction in oviraptorids, a proxy for digit 131 size was developed. We follow the conventional nomenclature for manual digits of digits 132 I, II, and III, because those are the phenotypes expressed, although we realize these may 133 be homologous to digits II, III, and IV 11. Measurements for 73 complete digits (digit I, n 134 = 32; digit II, n = 29; digit III, n = 12) of 31 oviraptorosaur specimens (15 taxa) showed 135 that straight-line length of the ungual was strongly correlated to the pre-ungual length of 136 that digit (0.81<R2>0.88; Fig.