Morphological and Phylogenetic Study Based on New Materials of Anchiornis huxleyi (Dinosauria, Theropoda) from Jianchang, Western Liaoning, China

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1 Vol. 92 No. 1 pp.1 15 Feb Morphological and Phylogenetic Study Based on New Materials of Anchiornis huxleyi (Dinosauria, Theropoda) from Jianchang, Western Liaoning, China GUO Xiangqi 1, 2, *, XU Li 3 and JIA Songhai 3 1 Yunnan Provincial Museum, Kunming , Yunnan, China 2 Institute of Geology, Chinese Academy of Geological Sciences, Beijing , China 3 Henan Geological Museum, Zhengzhou , Henan, China Abstract: Anchiornis huxleyi, which is a member of the Middle Late Jurassic Yanliao Biota, is the smallest feathered dinosaur ever known. It has been described as a critical link between feathered dinosaurs and birds. Recent studies, including those of Anchiornis, Xiaotingia, Eosinopteryx and Aurornis, challenged Archaeopteryx as the most basal bird. The new Anchiornis huxleyi specimens that are described in this paper show some minor different characters compared to previously reported Anchiornis specimens, which has revised the character list of Anchiornis and indicates a different phylogenetic point from former opinions. Key words: Anchiornis, feathered dinosaur, non-avian dinosaur, Middle Late Jurassic, Yanliao Biota 1 Introduction Anchiornis huxleyi is a feathered theropod which was discovered in the Middle Late Jurassic Tiaojishan Formation of Jianchang County, Liaoning Province, China (Xu Xing et al., 2009). The discovery of this species provides great evidence for the origins of birds, flight capabilities and feathers. In 2009, skeleton and feather features of Anchiornis were described and the systematic position of Anchiornis was discussed, based on two specimens, IVPP V14378 (Xu Xing et al., 2009) which is the holotype, and LPM B00169 (Hu et al., 2009). However, the skeleton and feather characters need to be revised because the specimens were incomplete and included controversial characters. The systematic position of Anchiornis also requires further discussion because of different points for the classification (Hu et al., 2009; Xu Xing et al., 2009). include lissamphibians, transitional pterosaurs, feathered theropods and primitive mammals, indicating a close relationship with the Early Cretaceous Jehol Biota (Guo Xiangqi et al., 2012; Liu et al., 2012; Xu Xing et al., 2016; 2 Geological Setting Anchiornis is a member of Yanliao Biota, which is a Middle Late Jurassic terrestrial biota distributed in western Liaoning, northern Hebei and southeastern Inner Mongolia of China (Fig. 1). Yanliao Biota vertebrates * Corresponding author. xiangqi_guo@126.com Fig. 1. Localities of fossil vertebrates of the Yanliao Biota in western Liaoning and adjacent areas (modified from Guo Xiangqi et al., 2012, fig. 1)., localities of Anchiornis huxleyi;, other localities of fossil vertebrates of the Yanliao Biota Geological Society of China

2 2 Vol. 92 No. 1 Feb Gao Fuliang et al., 2017). 3 Systematic Palaeontology Class Theropoda Marsh, 1881 Order Maniraptor Gauthier, 1986 Genus Anchiornis Xu Xing et al., 2009 Anchiornis huxleyi Xu Xing et al., Materials Two nearly complete Anchiornis huxleyi specimens, 41HIII 0404 and 41HIII 0415 (housed in Henan Geological Museum), which were discovered in the Middle Late Jurassic Tiaojishan Formation of Jianchang, Liaoning Province, China, as other Anchiornis specimens. 41HIII 0404, which is 57.4 cm long, is a nearly complete skeleton missing the posterior part of skull, parts of the cervical and dorsal vertebrae, shoulder girdle and partial pelvic girdle (Fig. 2). Fortunately, elegant feathers distributed over the region of forelimbs, hind limbs, dorsal and caudal vertebrae and pelvic girdle were preserved in this specimen. 41HIII 0415, which is 37.5 cm long, is a nearly complete skeleton that is missing parts of the skull, mandible, vertebrae, shoulder girdle and pelvic girdle (Fig. 3). The closed neuro-central sutures suggest these both specimens are probably adult individuals. 5 Description and Comparison 5.1 Skull and mandible The skulls in new specimens are triangular in lateral view and have a relatively blunt snout, like LPM-B00169 (Hu et al., 2009). The posterior part of skull is unidentifiable in the new specimens (Fig. 4a). The length of the skull in 41HIII 0415 is 51.4 mm (Table 1). The maxillary process of the premaxilla extends posteriorly so that the premaxilla does not compose the posterior border of the external naris, different from some dromaeosaurids like Sinornithosaurus (Xu et al., 1999) (Fig. 4b). Anchiornis bears four sub-equal premaxillary teeth which are closely packed and are not strongly bent posteriorly. There is no serration on the anterior and posterior carine, as seen in some dromaeosaurids and troodontids like Sinornithosaurus (Xu et al., 1999; Liu Jinyuan et al., 2004), Xixiasaurus (Lü et al., 2010) and Microraptor (Xu et al., 2000, 2003). As seen in LPM-B00169, the antorbital fossa contains promaxillary fenestra, maxillary fenestra and antorbital fenestra, similar to most dromaeosaurids and troodontids like Sinornithosaurus (Xu et al., 1999; Liu Fig. 2. Specimen 41HIII 0404 of Anchiornis huxleyi. (a), photograph of specimen 41HIII 0404; (b), line drawing of specimen 41HIII Scale bars equal 5 cm. Abbreviations: boc, basioccipital; cav, caudal vertebrae; cev, cervical vertebrae; ch, chevrons; cr, cervical rib; dr, dorsal rib; dv, dorsal vertebrae; ept, eptipterygoid; fu, furcula; g, gastralia; hy, hyoid; last, left astragalus; lcal, left calcaneum; lco, left coracoids; lde, left dentary; lf, left femur; lfi, left fibula; lh, left humerus; lis, left ischium; ll, left lachrymal; lm, left maxilla; ln, left nasal; lp, left pubis; lpm, left premaxilla; lr, left radius; lsa, left surangular; lsc, left scapula; lspl, left splenial; lt, left tibia; lul, left ulna; mc, metacarpal; mt, metatarsal; rae, radiale; ran, right angular; rast, right astragalus; rcal, right calcaneum; rde, right dentary; rf, right femur; rfi, right fibula; rh, right humerus; ril, right ilium; ris, right ischium; rm, right maxilla; rp, right pubis; rpm, right premaxilla; rr, right radius; rsa, right surangular; rsc, right scapula; rt, right tibia; rul, right ulna; sec, semilunate carpal; v, vomer.

3 Feb Vol. 92 No. 1 3 Fig. 3. Specimen 41HIII 0415 of Anchiornis huxleyi. (a), photograph of specimen 41HIII 0415; (b), line drawing of specimen 41HIII Scale bars equal 5 cm. Abbreviations: cav, caudal vertebrae; cev, cervical vertebrae; dr, dorsal rib; dv, dorsal vertebrae; fr, frontal; fu, furcula; lco, left coracoids; lde, left dentary; lf, left femur; lfi, left fibula; lh, left humerus; lil, left ilium; lis, left ischium; ll, left lachrymal; lm, left maxilla; ln, left nasal; lpm, left premaxilla; lr, left radius; lsc, left scapula; lt, left tibia; lul, left ulna; mc, metacarpal; mt, metatarsal; pa, parietal; rae, radiale; rco, right coracoids; rde, right dentary; rf, right femur; rfi, right fibula; rh, right humerus; ris, right ischium; rpm, right premaxilla; rr, right radius; rsc, right scapula; rt, right tibia; rul, right ulna; sec, semilunate carpal. Jinyuan et al., 2004), Sinornithoides (Currie and Dong, 2001) and Aurornis (Pascal et al., 2013a) but different from Bambiraptor (Burnham et al., 2000) and Shanag (Turner et al., 2007a) (Fig. 4c). The number of maxillary teeth is close to ten, which is less than some dromaeosaurids and troodontids such as Xixiasaurus (Lü et al., 2010), Tsaagan mangas (Norell et al., 2006), Austroraptor (Novas et al., 2008), Sinornithoides (Russell and Dong, 1993), Sinusonasus (Xu Xing and Wang Xiaolin, 2004b), Jinfengopteryx (Ji Qiang et al., 2005) and Daliansaurus (Shen Caizhi et al., 2017). These teeth are not closely packed and not curved strongly, unlike some dromaeosaurids and troodontids like Microraptor (Xu et al., 2000, 2003), Sinovenator (Xu et al., 2002), Bambiraptor (Burnham et al., 2000), Sinornithosaurus millenii (Xu et al., 1999) and Shanag (Turner et al., 2007a). Furthermore, Anchiornis teeth lack serrations on both the anterior and posterior carinae and there is no distinct constriction between the crown and the root, as in Changyuraptor (Han et al., 2014). A small internarial bar appears at the joint part of the nasal area. The nasal area gradually widens posteriorly, reaching the anterior region of lachrymal, to be more specific, above the external nares, promaxillary fenestra, maxillary fenestra and antorbital fenestra. Like most dromaeosaurids and troodontids, such as NGMC-91 (Ji et al., 2001), T. mangas (Norell et al., 2006), Bambiraptor (Burnham et al., 2000), Linheraptor (Xu et al., 2010), Sinornithosaurus (Xu et al., 1999; Liu Jinyuan et al., 2004), Sinornithoides (Currie and Dong, 2001), Sinusonasus (Xu Xing and Wang Xiaolin, 2004b) and Xixiasaurus (Lü et al., 2010), the lachrymal is T-shaped in a lateral view. The maxillary process of the lachrymal is relatively short and directed anteroventrally, forming part of the dorsal border of the antorbital fenestra so that the shape of antorbital fenestra is a sub-triangle in a lateral view. The prefrontal process is shorter than the maxillary process and is directed posterodorsally, different from Aurornis (Pascal et al., 2013a) and Eosinopteryx (Pascal et al., 2013b). The lachrymal extends transversely in a dorsal view and bears a lateral ridge. The left and right frontal is sutured at the middle line and the joint slightly protrudes dorsally. In a dorsal view, the width of the posterior part of the frontal is about twice that of the anterior part. The lateral border of the frontal is thick and forms the upper boundary of the orbit. The length of the mandible is at 80% of the femur length. Both new specimens have a relatively complete well preserved mandible (Fig. 4d). The dentary length is at 67% of the mandible length. On the lateral surface of the dentary lies a horizontal groove that includes a row of neurovascular fenestra, resembling that of Sinovenator (Xu et al., 2002), Mei (Xu and Norell, 2004), Troodon (Currie, 1987), Byronosaurus (Makovicky et al., 2003), Austroraptor (Novas et al., 2008), Sinusonasus (Xu Xing and Wang Xiaolin, 2004b), Aurornis (Pascal et al., 2013a) and Daliansaurus (Shen Caizhi et al., 2017). What is

4 4 Vol. 92 No. 1 Feb Fig. 4. Skull, mandible and hyoid arch of specimen 41HIII 0404, premaxilla and maxilla of specimen 41HIII (a), photograph and line drawing of skull of specimen 41HIII 0404 (scale bar equals 1 cm); (b), photograph and line drawing of premaxilla of specimen 41HIII 0415 (scale bar equals 1 mm); (c), photograph and line drawing of maxilla of specimen 41HIII 0415 (scale bar equals 5 mm); (d), photograph and line drawing of mandible and hyoid arch of specimen 41HIII 0404 (scale bar equals 1 cm). Abbreviations: aof, antorbital fenestra; bhy, basihyoid; chy, ceratohyoid; emdf, external mandibular foramen; fr, frontal; hym, hyomandible; idp, interdental plate; jp, jugal process; lap, lachrymal process; lde, left dentary; ll, left lachrymal; lm, left maxilla; ln, left nasal; lpm, left premaxilla; lspl, left splenial; mg, Meckelian groove; mp, maxillary process; mxf, maxillary fenestra; np, nasal process; nvf, neurovascular foramina; pa, parietal; prmf, promaxillary fenestra; ran, right angular; rde, right dentary; rpm, right premaxilla; rsa, right surangular; saf, surangular foramen. special is that the space between the fenestra increases posteriorly and the width of the groove does not change in 41HIII 0404, unlike that observed in another Anchiornis specimen LPM-B00169 (Hu et al., 2009), Xiaotingia (Xu et al., 2011a) and Eosinopteryx (Pascal et al., 2013b). A deep Meckelian groove is located on the labial surface of

5 Feb Vol. 92 No. 1 5 Table 1 Selected measurements (in mm) of 41HIII 0404 and 41HIII 0415 Skull length 41HIII HIII Mandible length 52.7 Caudal series length Scapula length 25.7 (L) Coracoid length 5 (L) Furcula width Furcula length (each branch) Humerus length 63.2 (L) 43.8 (L) 42.8 (R) Humerus deltopectoral crest length 15.9 (L) 11.9 (L) Ulna length 52.9 (L) 52.9 (R) 37.3 (L) 34.6 (R) Radius length 51 (L) 36.9 (L) 34.6 (R) Semilunate carpal length 2.7 (L) 1.7 (L) Metacarpal I length 11.2 (L) 8.3 (L) 7.9 (R) Metacarpal II length 30.9 (L) 21.5 (R) Metacarpal III length 28.7 (L) Manual phalanx I (L) 24.3 (R) 21.6 (L) 18 (R) Manual phalanx I (L) 8.2 (L) 8.6 (R) Manual phalanx II-1 19 (L) 12.5 (R) Manual phalanx II (L) 18.6 (L) 19.3 (R) Manual phalanx II (L) 15.7 (R) 9.5 (L) 9.6 (R) Manual phalanx III (L) 7.7 (R) Manual phalanx III (L) 7.4 (R) 6.4 (R) Manual phalanx III (L) 13 (R) 10.4 (R) Manual phalanx III (L) 7.7 (R) Ilium length 36.3 (R) Pubis length 53.7 (R) Ischium length 20.8 (R) 13.6 (L) Femur length 65.6 (L) 66.8 (R) 46.8 (L) Tibia length 92.5 (L) Tibiotarsus length 96 (R) 71.5 (L) 71.2 (R) Fibula length 90.6 (L) Astragalus length 2.1 (L) Metatarsal I length 8.7 (L) 4.8 (L) 3.9 (R) Metatarsal II length 49.2 (L) 48.3 (R) 32.9 (L) 36.2 (R) Metatarsal III length 52.8 (L) 49.5 (R) 35.7 (L) 37.2 (R) Metatarsal IV length 52.2 (L) 50.1 (R) 32.8 (L) 35.9 (R) Metatarsal V length 13.1 (L) Pedal phalanx I-1 length 6.6 (L) 5.5 (L) 5.7 (R) Pedal phalanx I-2 length 6.2 (L) 2.7 (L) 3.6 (R) Pedal phalanx II-1 length 11.2 (L) 7.7 (L) 8.6 (R) Pedal phalanx II-2 length 11.3 (L) 7.8 (L) 7.8 (R) Pedal phalanx II-3 length 5.8 (L) Pedal phalanx III-1 length 13.4 (L) 9.1 (L) Pedal phalanx III-2 length 10.1 (L) 10.8 (R) 7.6 (L) 7.6 (R) Pedal phalanx III-3 length 9.4 (R) 7.2 (L) 6.9 (R) Pedal phalanx III-4 length 13 (R) 6.4 (L) 5.7 (R) Pedal phalanx IV-1 length 9.8 (L) 9.8 (R) 5.8 (L) 7.5 (R) Pedal phalanx IV-2 length 5.6 (R) 4.4 (L) 5.5 (R) Pedal phalanx IV-3 length 13.2* (R) 3.5 (L) 4.9 (R) Pedal phalanx IV-4 length 2.1 (L) 5.4 (R) Pedal phalanx IV-5 length 12.1 (R) 4.1 (L) Notes: *, the estimated complete length of a partial element; abbreviations: L, left; R, right. the dentary, as in Shanag (Turner et al., 2007a). The posterodorsal process does not obviously protrude and the posteroventral process does not reach the external mandibular foramen. Like the maxillary teeth, the dentary teeth are not closely packed, not strongly curved posteriorly, lack serrations on the anterior and the posterior carinae and do not have a distinct constriction between the crown and the root. Furthermore, a distinct interdental plate can be seen on the labial surface. The dentary has fourteen teeth, similar to that of Sinornithosaurus haoiana (Liu Jinyuan et al., 2004), Bambiraptor feinbergi (Burnhamet al., 2000), Shanag (Turner et al., 2007a), Saurornitholestes langstoni (Sue, 1978), Velociraptor mongoliensis (Barsbold and Osmólska, 1999) and Changyuraptor (Han et al., 2014), more than Xiaotingia (Xu et al., 2011a) which has fewer than 10 and fewer than Austroraptor (Novas et al., 2008) which present 25 and 18 in Jinfengopteryx (Ji Qiang et al., 2005). Most of the splenial covers the posterior part of the Meckelian groove in a labial view. The blunt process is directed posterodorsally and is in the posterior part of the upper margin. The angular length is at 47% of that of the mandible. A small, sub-round surangular foramen is located near the posterior end of the surangular, unlike that in Xiaotingia (Xu et al., 2011a), Anchiornis IVPP V14378 (Xu Xing et al., 2009) and V. mongoliensis (Barsbold and Osmólska, 1999). There is a sub-oval external mandibular foramen at the posterior part of the joint of the angular and surangular. The basihyoid is a parallelogram in a lateral view and is located in the anterior part of the hyoid arch. A pair of slender bowed bones to the left and right sides of the basihyoid are ceratohyoids. A small round bone located at the end of the ceratohyoid is probably a hyomandible. 5.2 Vertebral column Most of centra and ribs are preserved in 41HIII 0404, the anterior cervical and dorsal vertebrae are missing and sacral vertebrae are unrecognizable due to poor preservation. Except for the atlas, the other nine cervical vertebrae can be clearly distinguished in 41HIII 0415, but the rest of the axial skeleton is incomplete. The centrum length in a cervical series decreases slightly posteriorly. The prezygapophysis is relatively robust. The diapophyses in the cervical vertebra are developed and semi-circular in a lateral view. The length of rhe cervical rib is slightly longer than the corresponding centrum, different from Aurornis (Pascal et al., 2013a). The shaft of the cervical rib is nearly parallel to that of the centrum. The height of the neural arch is about twice that of the centrum. The neural spine points posterodorsally, but it is not distally expanded. Diapophyses are obvious but parapophyses are not. The centrum length is twice the height and shortens posteriorly. No distinct pneumaticfossa can be observed. The dorsal ribs contain a relatively slender capitulum and short tuberculum. The fourth ribs are the longest at 59% of the femur, while the eighth dorsal ribs are the shortest, at 30% of the femur. There is no uncinate process on the ribs, different from that of Microraptor zhaoianus (Xu et al., 2000) and S. haoiana (Liu Jinyuan et al., 2004). The gastralia are preserved in pairs. The length of the longest gastralia is at 36% of the femur and the shortest is at 11%. The caudal count is about 28 based on the complete preservation of 41HIII 0404 (Fig. 5a), like Tianyuraptor

6 6 Vol. 92 No. 1 Feb Fig. 5. Caudal vertebrae, chevronsin, Semilunate carpal, manus and pelvic girdle of specimen 41HIII (a), photograph and line drawing of caudal vertebrae and chevrons (scale bar equals 1 cm); (b), photograph and line drawing of Semilunate carpal (scale bar equals 5 mm); (c), photograph and line drawing of manus (scale bar equals 2 cm); (d), photograph and line drawing of pelvic girdle (scale bar equals 1 cm). Abbreviations: bvf, brevis fossa; cup, cuppedicus fossa; isp, ischial peduncle; lis, left ischium; lp, left pubis; mc, metacarpal; obp, obturator process; puf, pubic foot; pup, pubic peduncle; rae, radiale; ril, right ilium; ris, right ischium; rp, right pubis; sac, supracetabular crest; sec, semilunate carpal. ostromi (Zheng et al., 2009), which is more than 24 or 25 in Microraptor (Xu et al., 2000, 2003), 23 in Jinfengopteryx elegans (Ji Qiang et al., 2005) and 22 in Changyuraptor (Han et al., 2014). The total length of the tail is about four times that of the trunk and about 4.4 times that of femur, as seen in Tianyuraptor (Zheng et al., 2009), which is comparatively shorter than Epidendrosaurus (Zhang et al., 2002) but obviously longer than Mei (Xu and Norell, 2004) and Eosinopteryx (Pascal et al., 2013b). The eight anterior caudals are elongated posteriorly and the 10 posterior ones are shortened posteriorly. The transitional point is probably located at the sixth to eighth vertebrae (Table 2). Transverse processes can be seen in the anterior caudal vertebrae, as in the holotype (Xu Xing et al., 2009). But notably, the transverse process of the first vertebra is directed posteriorly where the others are directed laterally. The Table 2 Measurements (in mm) of the centrum length of the caudal vertebrae of 41HIII 0404 cv length cv length cv length cv length Note: Abbreviation: cv, caudal vertebrae. prezygapophysis of the vertebrae get longer posteriorly, indicated by the length of the anterior prezygapophysis that is about one fourth of the corresponding centrum and the posterior prezygapophysis that is about half of the corresponding centrum. The postzygapophysis length is slightly shorter than the corresponding prezygapophysis, which is about one third that of the corresponding centrum at the end of the tail. These prezygapophysis and

7 Feb Vol. 92 No. 1 7 postzygapophysis characters are very different from dromaeosaurids, like Bambiraptor (Burnham et al., 2000), Microraptor (Xu et al., 2000, 2003), S. haoiana (Liu Jinyuan et al., 2004), Graciliraptor (Xu Xing and Wang Xiaolin, 2004a), Linheraptor (Xu et al., 2010) and Buitreraptor (Makovicky et al., 2005). A distinct groove appears on the lateral surface of the middle and posterior vertebrae, consistent with LPM-B00169 (Hu et al., 2009) and Eosinopteryx (Pascal et al., 2013b). The length of the middle caudal vertebrae is about twice that of the caudal vertebrae at the end, similar to Tianyuraptor (Zheng et al., 2009), at 2.1 times longer than the anterior vertebrae, as in Sinusonasus (Xu Xing and Wang Xiaolin, 2004b) and Xiaotingia (Xu et al., 2011a), but greater than Linheraptor (Xu et al., 2010) and the holotype specimen of Anchiornis (Xu Xing et al., 2009). Chevrons shafts are parallel to the centrum. Chevrons are only posteriorly extended and anteriorly bifurcated, which is similar to that of the holotype (Xu Xing et al., 2009) but different from Graciliraptor (Xu Xing and Wang Xiaolin, 2004a), Buitreraptor (Makovicky et al., 2005), Jinfengopteryx (Ji Qiang et al., 2005) and Sinusonasus (Xu Xing and Wang Xiaolin, 2004b). Each chevron tapers distally. The length of anterior chevrons is about half that of the relative centrum and shortens posteriorly. 5.3 Forelimb and pectoral girdle The total length of the forelimb (humerus + ulna + carpal + metacarpal II + digit II) is at 78% of the hind limb, like Sinornithosaurus (Xu et al., 1999; Liu Jinyuan et al., 2004), greater than the 53% in the Tianyuraptor (Zhenget al., 2009), but much shorter than the 96% in the Changyuraptor (Han et al., 2014). The scapula length is at 59% of the humerus, resembling the holotype, slightly less than the 63% in S. millenii (Xu et al., 1999) and 65% in S. haoiana (Liu Jinyuan et al., 2004) and considerably less than the 77% in the Buitreraptor (Makovicky et al., 2005) and 88% in the Tianyuraptor (Zheng et al., 2009). The scapula to ulna length ratio is 70%, which is less than the 77% of S. millenii (Xu et al., 1999) and 81% of S. haoiana (Liu Jinyuan et al., 2004). The length of scapula is at 55% of the femur, which is less than the 70% in Linhevenator (Xu et al., 2011b). The acromial process is not obvious, differing from the distinct acromial process types seen in Unenlagia comahuensis (Novas and Puerta, 1997), Rahona (Forster et al., 1998), Buitreraptor (Makovicky et al., 2005), Jinfengopteryx (Ji Qiang et al., 2005) and Xiaotingia (Xu et al., 2011a). The scapula does not expanded distally, different from Jinfengopteryx (Ji Qiang et al., 2005), Linhevenator (Xu et al., 2011b) and Epidendrosaurus (Zhang et al., 2002). The glenoid cavity is located laterally, as seen in U. comahuensis (Novas and Puerta, 1997), Microraptor (Xu et al., 2000, 2003), Sinovenator (Xu et al., 2002) and Mei (Xu and Norell, 2004). The coracoid tubercle appears on the lateral surface of the coracoid which bears a distinct sub-glenoid fossa, like Eosinopteryx (Pascal et al., 2013b). The length of each furcula branch is at 26% of the femur, which is relatively shorter than that of the holotype (Xu Xing et al., 2009). There is no hypocleidium in the furcular. The length of the humerus is at 95% of the femur, like Epidexipteryx (Zhang et al., 2008), but is longer than many deinonychosaurians, like U. comahuensis (Novas and Puerta, 1997), Austroraptor (Novas et al., 2008), Linheraptor (Xu et al., 2010), Linhevenator (Xu et al., 2011b), Epidendrosaurus (Zhang et al., 2002), Aurornis (Pascal et al., 2013a) and Daliansaurus (Shen Caizhi et al., 2017) (Table 3). The deltopectoral crest is not obviously protruding, being one fourth the length of the humerus, as in other Anchiornis specimens (Hu et al., 2009; Xu Xing et al., 2009), relatively shorter than those in Unenlagia paynemili (Calvo et al., 2004), Luanchuanraptor (Lü Junchang et al., 2007) and Linhevenator (Xu et al., 2011b). The length of the ulna is at 83.7% of the humerus, similar to the holotype (Xu Xing et al., 2009), Changyuraptor (Han et al., 2014) and Epidendrosaurus (Zhang et al., 2002), but different from the much longer ulna in Microraptor (Xu et al., 2000, 2003), Jinfengopteryx (Ji Qiang et al., 2005), Xixiasaurus (Lü et al., 2010), Rahona (Forster et al., 1998), Graciliraptor (Xu Xing and Wang Xiaolin, 2004a) and NGMC91 (Ji Qiang et al., 2001). The ulna is straight and the radius is relatively curved, like Eosinopteryx (Pascal et al., 2013b). The ulna is only slightly thicker than the radius. The olecranon process is not obvious. The semilunate carpal in the new specimens is semi-circular, covering the proximal surface of metacarpal I and half of metacarpal II. This is inconsistent with the holotype, whose semilunate carpal lies on the surface of metacarpal II and metacarpal III and fuses with these metacarpals, as is also seen in M. zhaoianus (Xu et al., 2000), S. haoiana (Liu Jinyuan et al., 2004), Jinfengopteryx (Ji Qiang et al., 2005) and Tianyuraptor (Zheng et al., 2009) in which a larger part of the semilunate carpal covers metacarpal II (Fig. 5b). The length of the manus is at 137% of the femur, including metacarpal II, the longest metacarpal, which is at 49% of the femur length (Fig. 5c). Metacarpal III is a little shorter, at 93% of metacarpal II. Metacarpal I is at 36% of metacarpal II, which is very similar to IGM100/44 (Barsbold et al., 1987) and Eosinopteryx (Pascal et al., 2013b), slightly shorter than Jinfengopteryx (Ji Qiang et al., 2005) but longer than S. haoiana (Liu Jinyuan et al., 2004), Changyuraptor (Han et al., 2014) and

8 8 Vol. 92 No. 1 Feb Table 3 Selected ratios of 41HIII 0404, 41HIII 0415, IVPP V14378, LPM-B00169 of Anchiornis and other relative Paraves Anchiornis 41HIII 0404 Anchiornis Anchiornis IVPP 41HIII 0415 V14378 Anchiornis Xiaotingia LPM-B00169 STM 27-2 Aurornis YFGP-T5198 Eosinopteryx YFGP-T5197 Forelimb length/hindlimb length * Scapula length/humerus length * Humerus length/femur length * * Ulna length/femur length * Humerus+Ulna length/femur length * Radius length/femur length * Manus length/femur length * * Metacarpal I length/metacarpal II length Metacarpal I+Manual phalanx I-1 length/metacarpal II length Metacarpal III length/metacarpal II length Manual phalanx II-2 length/manual phalanx II-1 length Manual phalanx III-1 length/manual phalanx II-1 length Manual phalanx III-2 length/manual phalanx III-1 length Manual phalanx III-3 length/manual phalanx III-1 length Ilium length/femur length * * Pubis length/femur length Ischium length/femur length * 0.28 Tibiotarsus length/femur length * Tibia length/femur length 1.4 Metatarsal III length/femur length Metatarsal I length/metatarsal III length Metatarsal V length/metatarsal III length Pedal phalanx II-2 length/pedal phalanx II-1 length Pedal phalanx III-2 length/pedal phalanx III-1 length Pedal phalanx III-3 length/pedal phalanx III-1 length Pedal phalanx IV-1 length/pedal phalanx II-1 length Notes: *, the estimated ratio by the estimated length; abbreviations: IVPP, Institute of Vertebrate Paleontology and Paleoanthropology; LPM, Liaoning Paleontological Museum; STM Shandong Tianyu Museum of Nature; YFGP, Yizhou Fossil & Geology Park. Graciliraptor (Xu Xing and Wang Xiaolin, 2004a). Metacarpal II is a little wider than metacarpal I and III. The ligament fossa in the phalanges are deep, differing from Xiaotingia (Xu et al., 2011a) whose ligament fossa are not obvious. The phalanges in digit II are wider than those in other phalanges. Metacarpal II is longer than phalanx I-1 but is shorter than metacarpal I plus phalanx I- 1. Phalanx II-2 is the longest phalanx at 1.3 times that of II -1. Phalanx II-3 is distinctly shorter than phalanx II-1, different from NGMC91 (Ji et al., 2001) whose phalanx II -3 and II-1 are almost the same length. Phalanx III-1 and III-2 are the shortest phalanges. Phalanx III-1 is at 40% of phalanx II-1 and a little longer than III-2, unlike that in Sinornithosaurus (Xu et al., 1999; Liu Jinyuan et al., 2004), Microraptor gui (Xu et al., 2003), Graciliraptor (Xu Xing and Wang Xiaolin, 2004a), Tianyuraptor (Zheng et al., 2009) and Xiaotingia (Xu et al., 2011a), whose phalanx III-1 is obviously longer than phalanx III- 2. The first ungual is the largest in 41HIII 0404 and bear the largest curvature, but ungual sizes in 41HIII 0415 look the same. 5.4 Hind limb and pelvic girdle The total length of the hind limb (femur + tibiotarsus + metatarsal III + digit III) is at 126% of the forelimb. The short ilium is at 55% of the femur, shorter than the 60% in Sinovenator (Xu et al., 2002) and 75% in Tianyuraptor (Zheng et al., 2009). The anterior border of the preacetabular is flat and slightly ventrally directed, different from Epidexipteryx (Zhang et al., 2008), Epidendrosaurus (Zhang et al., 2002), Xiaotingia (Xu et al., 2011a) and Tianyuraptor (Zheng et al., 2009), which bear a projecting anterior border (Fig. 5d). The cuppedicus fossa is obvious in the ilium, like U. comahuensis (Novas and Puerta, 1997) and Luanchuanraptor (Lü Junchang et al., 2007), and different from Mahakala (Turner et al., 2007b) and Hesperonychus (Longrich and Currie, 2009), which do not have an obvious cuppedicus fossa. Postacetabular tapers posteriorly, like in most of the deinonychosaurians. The pubic peduncle is located anteroventrally and the ischial peduncle is located posteroventrally. The width of the pubic peduncle is longer than the acetabulum and ischial peduncle. The supracetabular crest is obvious. The pubis is nearly perpendicular to the ilium, whose shaft is at 81% the length of the femur. The middle part of pubis is robust and widens medially, being possibly a pubic apron. The distal joint is flat and is directed posteriorly, forming the pubis foot, like Rahona (Forster et al., 1998), Bambiraptor (Burnham et al., 2000) and Tianyuraptor (Zheng et al., 2009), but is different from the undeveloped type like that in Linheraptor (Xu et al., 2010), Luanchuanraptor (Lü Junchang et al., 2007), Sinornithoides (Russell and Dong, 1993) and Epidexipteryx (Zhang et al., 2008). The pubis foot is at 12% the length of the pubis. The ischium is relatively flat, the shaft is directed posteroventrally, and it

9 Feb Vol. 92 No. 1 9 is at 39% the length of the pubis, unlike Bambiraptor (Burnham et al., 2000), Sinusonasus (Xu Xing and Wang Xiaolin, 2004b) and Epidexipteryx (Zhang et al., 2008), whose ischium is longer than half of the pubis. The pubic peduncle is nearly perpendicular to the iliac peduncle. The anterior border of the ischium is flat but the posterior border is straight and thick. A distinct obturator process appears at the distal 1/3 part of the posterior border in 41HIII 0404 but at the middle of the posterior border in 41HIII No proximodorsal process were observed, unlike U. comahuensis (Novas and Puerta, 1997), Rahona (Forster et al., 1998), S. millenii (Xu et al., 1999), Bambiraptor (Burnham et al., 2000), Buitreraptor (Makovicky et al., 2005), M. gui (Xu et al., 2003), Sinovenator (Xu et al., 2002) and Mei (Xu and Norell, 2004). The femurs are slightly anteriorly bent and the distal part is more robust, the same as the holotype (Xu Xing et al., 2009). An obvious femoral head is directed dorsomedially. The femoral neck and a shallow trochanteric fossa can be seen in 41HIII A small fourth trochanter appears at the middle of the femur shaft, different from U. comahuensis (Novasand Puerta, 1997), Bambiraptor (Burnham et al., 2000) and Buitreraptor (Makovicky et al., 2005), which do not have a fourth trochanter. The length of the tibiotarsus is at 149% of the femur, close to the 150% in the holotype (Xu Xing et al., 2009) but longer than U. comahuensis (Novas and Puerta, 1997), M. zhaoianus (Xu et al., 2000), Rahona (Forster et al., 1998), Tianyuraptor (Zheng et al., 2009), Linheraptor (Xu et al., 2010), Sinusonasus (Xu Xing and Wang Xiaolin, 2004b), Epidexipteryx (Zhang et al., 2008) and Eosinopteryx (Pascal et al., 2013b). The tibia is straight and the middle part is slightly narrower than both ends. The fibula is a little shorter than the tibia. The width of the proximal end of the fibula is slightly less than that of the tibia. The middle part of the fibula is extremely slender, about 1/6 the size of the middle of the tibia, like Rahona (Forster et al., 1998) and S. millenii (Xu et al., 1999). The body of the astragalus is sub-rounded in a lateral view. Tha ascending process, which is at 73% the length of the astragalus, is straight and tapers proximally, different from Utahraptor (Kirkland et al., 1993) whose ascending process forms a sub-triangle surface, and in Talos (Zanno et al., 2011) whose ascending process covers the surface of the tibia. Metatarsal III is the longest metatarsal at 77% the length of the femur and is an arctometatarsus, like Graciliraptor (Xu Xing and Wang Xiaolin, 2004a), Saurornithoides junior (Barsbold, 1974), Tochisaurus (Kurzanov and Osmólska, 1991), Mei (Xu and Norell, 2004), NGMC91 (Ji et al., 2001), Neuquenraptor (Novas and Pol, 2005), M. zhaoianus (Xu et al., 2000), Linhevenator (Xu et al., 2011b), Sinusonasus (Xu Xing and Wang Xiaolin, 2004b) and the holotype (Xu Xing et al., 2009). Metatarsal I is the shortest metatarsal at 16% the length of metatarsal III. Metatarsal I is located at the distal 1/4 part of metatarsal II, like M. zhaoianus (Xu et al., 2000), NGMC91 (Ji et al., 2001) and Epidendrosaurus (Zhang et al., 2002), but differing from the holotype (Xu Xing et al., 2009) and Linhevenator (Xu et al., 2011b) whose metatarsal I is located at the middle of metatarsal II. The length of metatarsal V is at 25% of metatarsal III, much shorter than Changyuraptor (Han et al., 2014). The distal end of metatarsal II bears a distinct ginglymoid. Metatarsal IV bears an obvious ridge in anterior view, resembling Neuquenraptor (Novas and Pol, 2005), M. zhaoianus (Xu et al., 2000), Mei (Xu and Norell, 2004) and S. millenii (Xu et al., 1999). The width of metatarsal IV is equal to the metatarsal II. The length of metatarsal IV is slightly longer than metatarsal II. The first digit is not reversed and is located at the posterior of other digits. Phalanx I-1 is about the half length of phalanx III-1. The length of phalanx II-1 is nearly equal to phalanx II-2 which has a distinct proximal heel like Mahakala (Turner et al., 2007b), Austroraptor (Novas et al., 2008), Byronosaurus (Norell et al., 2000) and Linhevenator (Xu et al., 2011b). The third digit is the longest and contains phalanx III-1, which is at 1.3 times length of phalanx III-2, and phalanx III-3 is the shortest phalanx in digit III. Phalanx IV-2, IV-3 and IV-4 are the shortest phalanges. The height of the first ungual is about half that of the second one. The second ungual is only slightly larger than the other unguals in 41HIII 0404, as in the holotype (Xu Xing et al., 2009), and is not strongly curved, as seen in Hesperonychus (Longrich and Currie, 2009), IGM100/44 (Barsbold et al., 1987) and Borogovia (Osmólska, 1987). This differs from the strongly curved ungual in Rahona (Forster et al., 1998), Pyroraptor (Allain and Taquet, 2000), Microraptor (Xu et al., 2000, 2003), S. haoiana (Liu Jinyuan et al., 2004), Graciliraptor (Xu Xing and Wang Xiaolin, 2004a), Neuquenraptor (Novas and Pol, 2005), Sinusonasus (Xu Xing and Wang Xiaolin, 2004b), Mei (Xu and Norell, 2004), Anchiornis IVPP V14378 (Xu Xing et al., 2009), Linhevenator (Xu et al., 2011b) and Pedopenna (Xu and Zhang, 2005). However, in 41HIII 0415, the third ungual is the largest in terms of height and length. 5.5 Feathers Distinct feather prints are preserved in 41HIII 0404 and cover the back, tail, regions of the ulna, metacarpals, manual phalanges, tibiofibula, metatarsals and pedal phalanges (Fig. 6). None of the feathers have a rachis, except those at the posterior part of the tail. This is different from Anchiornis LPM-B00169 (Hu et al., 2009)

10 10 Vol. 92 No. 1 Feb Fig. 6. Feathers of specimen 41HIII (a), feathers at the back; (b), feathers at the forelimb; (c), feathers at the hind limb; (d), feathers at the anterior tail; (e), feathers at the posterior tail. Scale bars equal 5 cm. which has a distinct distribution of contour feathers at the forelimb and hind limb regions. These differences may not be individual or be in development, so more Anchiornis specimens are needed for further clarification. The feathers covering the back are obviously unusual. They are fibrous plumulaceous feathers, averaging 41mm in length and the longest feather which is at 1.6 times the length of forelimb feathers in this specimen. These feathers may not be forelimb feathers based on the preservation location and length. No such feathers are seen in other feathered dinosaurs and their function remains unknown. The tail feathers are very different between the anterior and posterior parts. The anterior feathers (at the point of vertebrae 1 10) are fibrous plumulaceous feathers that shorten distally, from 31.5 mm to 12.7 mm. Furthermore, the arrangement of these feathers is abnormal, they are

11 Feb Vol. 92 No anteriorly radial but posteriorly parallel and perpendicular to the tail. The posterior feathers (at the point of vertebrae) are asymmetric pennaceous feathers, perhaps rectrices, preserving an unclear rachis but distinct vanes. There are about 20 pairs of pennaceous feathers that are arranged posteriorly and point along the posterior tail at an angle of 30 degrees. These feathers are sub-oval and have a small distance from the tail, indicating a long quill or a different pigment between the proximal and distal feathers. The feathers distributed at the ulna are nearly perpendicular to the ulna and average 25 mm in length and at 47% the length of the ulna. The feathers distributed at the metacarpals are average 20.5 mm in length and are at 66% the length of metacarpal II. However, these feathers are at an angle of 45 degrees with the shaft of the metacarpals and point to the distal part. Except for the unguals, the manual phalanges also have a distribution of plumulaceous feathers that are average 4.8 mm in length. The feathers at the hind limb region are relatively dense, average 6.6 mm in length at the tibiotarsus region, 7.7 mm at the metatarsus region, 1.5 mm at the pedal phalanges region and the unguals have none. They are also plumulaceous feathers that are distally pointed at an angle of 60 degrees to relative bones. 6 Discussion These two specimens, 41HIII 0404 and 41HIII 0415, can be referred to Anchiornis based on the following characters: their skulls are triangular in a lateral view and have a relatively blunt snout; the teeth are unserrated; the antorbital fossa contains the promaxillary fenestra, maxillary fenestra and antorbital fenestra; transverse processes can be seen in the anterior caudal vertebrae and a distinct groove appears at the lateral surface of middle and posterior caudal vertebrae; the chevrons are only posteriorly extended and anteriorly bifurcated; the length of scapula is at 59% of the humerus; the humerus has a relatively short deltopectoral crest; the ulna is only slightly thicker than the radius; the length of the ulna is at 83.7% of the humerus; the ischium is short and at 30% of the femoral length; the femurs are slightly anteriorly bent and the distal part is more robust; the length of the tibiotarsus is at 149% of the femur; metatarsal III is the longest metatarsal, it is at 77% the length of the femur and is an arctometatarsus; the length of pedal phalanx II-2 is close to that of pedal phalanx II-1. By researching these two new Anchiornis specimens and comparing them to IVPP V14378 and LPM-B00169, we have revised the characters of Anchiornis as follows: the maxillary process of premaxilla and maxillary process of the nasal form the posterior border of the external nares; the external nares expand posteriorly to the anterior border of the antorbital fossa; the round maxilla fenestra is large and the sub-oval promaxillary fenestra is relatively small; the lachrymal is T-shaped in a lateral view, bearing a short prefrontal process which forms a subtriangular antorbital fenestra with the maxilla and nasal; they have a large lateral quadrate foramen; an array of neurovascular foremen appear at the labial surface of the dentary in a horizontal groove, and the interval between these foremen widens posteriorly; distinct pneumathodium appear at the lateral surface of cervical vertebrae; caudal vertebrae number about 28 and anterior caudal vertebrae bearing transversal processes and posterior caudal vertebrae bearing grooves are present at lateral surfaces; the chevrons at the middle and posterior part of the tail branch anteriorly, are directed posteriorly and are about half the length of relative caudal vertebrae; the scapula does not have a distinct acromial process, being flat and not extended distally; a lateral tubercle appears at the coracoid; the length of the deltopectoral crest is about 1/4 of the humerus; the ulna is only slightly thicker than the radius; the ilium bears an obvious supracetabular crest, cuppedicus fossa and brevis fossa, and the pubic peduncle is wider than the ischial peduncle; the pubis points anteroventrally and is distally posteriorly bent; the length of the tibiotarsus is at 1.5 times that of the femur; astragalus whose ascending process tapers at the end is not fused with tibia; metatarsals are arctometatarsus, metatarsal I is located at the distal 1/4 part of metatarsal II; the second ungual is only slightly larger than other unguals. However, 41HIII 0404 and 41HIII 0415 have some characters which differ from previously reported Anchiorins specimens, indicating an individual difference or different preservation situation. The sub-round surangular foramen is quite small in the new materials. Dentary teeth are not closely packed at the joint region. The interclavicular angle of furcular is obviously different in these specimens, at 77 degrees for 41HIII 0404 and 120 degrees for 41HIII 0415, which is close to IVPP V Numerous small pits are located on the ventral surface of the coracoid, which is described as an Anchiornis characteristic, were not seen in the new materials. The semilunate carpal is located at the proximal end of metacarpal I and II but not II and III in IVPP V The length of the ischium is at 30% of the femur, which is comparatively longer than IVPP V14378 and LPM- B Four Paraves, Anchiornis, Xiaotingia, Aurornis and Eosinopteryx, which are four small non-avian dinosaurs that have been found in a similar location, have close relationship. Most of their characters are quite similar,

12 12 Vol. 92 No. 1 Feb indicated by some bone length ratios (Table 3). Previous articles allocated them into different clades, like Troodontidae, at the base of Avialae, or forming a single group in Deinonychosauria, because they share characters with the Dromaeosauridae, Troodontidae and basal birds (Hu et al., 2009; Xu Xing et al., 2009; Xu et al., 2011a; Pascal et al., 2013a; Pascal et al., 2013b). Here we coded Anchiornis based on the character list synthesised 41HIII 0404 and 41HIII 0415, into a recently published phylogenetic analysis of basal Paraves, replacing the character list of Anchiornis in that paper (Pascal et al., 2013a) (Appendix 1). The data matrix, using Dilophosaurus, Dubreuillosaurus, Monolophosaurus and Sinraptor as outgroups, was analysed by TNT (Goloboff et al., 2008). A total of 1500 characters and 100 taxa were included in this research (Sinovenator was excluded because of the wrong code list in that article), using the traditional research of 1000 replicates. The 650 most parsimonious trees were found to build a strict consensus tree (tree length = 4581, consistency index=0.310 and retention index = 0.563) (Fig. 7). Our results place Anchiornis, Xiaotingia, Aurornis, Archaeopteryx, Eosinopteryx and part of Troodontidae at the base of Avialae. Other Troodontidae were placed as a sister group with Avialae. That means that the currently defined Troodontidae may not be a monophyletic group and it has a closer relationship with Avialae than with Dromaeosauridae. Yanliao Biota members, including Anchiornis, Xiaotingia, Aurornis, Eosinopteryx and Scansoriopterygidae being composed of Epidendrosaurus and Epidexipteryx, have the closest relationship with Aves, indicating that the Avialae had a rapid evolution during the Middle Late Jurassic period. Noticeably, 275 characters of Anchiornis included in the 1500 characters were identified in the former character list (Pascal et al., 2013a) and 399 characters are identified in this paper. However, 39 character codes are different when comparing the two character lists, which equates to 14% of the former character list (Pascal et al., 2013a) (Appendix 1). Similarly, the ratios were 16%, 10%, 8% and 11% when compared with Archaeopteryx, Aurornis, Eosinopteryx and Xiaotingia, respectively. These ratios show that differences between Anchiornis individuals of are usually greater than those between different species, a phenomenon which is not inconsistent with natural laws. The incomplete data (963 of Archaeopteryx, 289 of Aurornis, 265 of Eosinopteryx and 275 of Xiaotingia) should be the most important reason for this phenomenon. Species belonging to the Aurornis, Eosinopteryx and Xiaotingia were built based on a unique specimen resulting in insufficient data, and individual differences were difficult to identify. That is why sometimes the relationships with dromaeosaurids, troodontids, scansoriopterygids and other avians are quite different when a new species is discovered. Another reason to explain the phenomenon may be the questionable Fig. 7. The strict consensus tree of the 650 most parsimonious trees.

13 Feb Vol. 92 No character list. The feather characters should not be included in the list because we could not identify feather gender differences. Moreover, if a group of species have some apomorphic characters that are listed in the character list but other species do not, these characters may weaken the power of other common characters. The weakened power will greatly influence the result of a phylogenetic analysis when a great number of data are missing. As a result, the results from a phylogenetic analysis based on an incomplete character list are questionable. Thousands of Anchiornis specimens have been discovered. We need to synthesise the information from these specimens, identify the differences between individuals and shape a relatively complete character list so that conclusions are more reliable. 7 Conclusions (1) The feathered dinosaur, Anchiornis huxleyi, provides significant information on the evolution from dinosaurs to birds. We revised species characters by collecting more data from two new specimens, 41HIII 0404 and 41HIII (2) We found some minor character differences between new materials and former ones, caused by individual differences or a different preservation situation. The different feather patterns from previously studied materials showed that the diversity may not be due to individual or developmental differences. (3) The results from a phylogenetic analysis placed Anchiornis at the base of Avialae and indicated that currently defined Troodontidae may not be a monophyletic group. That means that the relationship between Avialae, Troodontidae and Dromaeosauridae is far more complex than previously imagined and that the Avialae had a rapid evolution during the Middle Late Jurassic period. (4) Limited data from unique specimens and the questionable character list weakens the reliability of phylogenetic analysis results in dinosaur research. More specimens and more data may be the only way to obtain more reliable results. Acknowledgements The authors thank Shu-an Ji and Ye Peng for commenting on the manuscript and Chunjun Zeng and Guihai Cui for preparing the specimens. The National Natural Science Foundation of China (grant No ) and China Geological Survey (grant No. DD ) supported this research. Manuscript recived Dec. 13, 2016 accepted Jun. 12, 2017 edited by Fei Hongcai References Allain, R., and Taquet, P., A new genus of Dromaeosauridae (Dinosauria, Theropoda) from the Upper Cretaceous of France. Journal of Vertebrate Paleontology, 20 (2): Barsbold, R., Saurornithoididae, a new family of small theropod dinosaurs from central Asia and North America. Palaeontologia Polonica, 30: Barsbold, R., and Osmólska, H., The skull of Velociraptor (Theropoda) from the Late Cretaceous of Mongolia. 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