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Phylogenetic support for a specialized clade ofCretaceous enantiornithine birds with informationfrom a new speciesJingmai K. O'Connor a b , Xuri Wang c , Luis M. Chiappe a , Chunling Gao c , Qingjin Meng c ,Xiaodong Cheng c & Jinyuan Liu ca Dinosaur Institute, Natural History Museum of Los Angeles, 900 Exposition Boulevard, LosAngeles, CA, 90007, U.S.A.b University of Southern California, 3651 Trousdale Parkway ZHS 117, Los Angeles, CA,90089, U.S.A. E-mail:c Dalian Natural History Museum, No. 40 Xicun Street Heishijiao Shahekou, District Dalian,P.R. ChinaPublished online: 09 Mar 2012.

To cite this article: Jingmai K. O'Connor , Xuri Wang , Luis M. Chiappe , Chunling Gao , Qingjin Meng , Xiaodong Cheng &Jinyuan Liu (2009) Phylogenetic support for a specialized clade of Cretaceous enantiornithine birds with information from anew species, Journal of Vertebrate Paleontology, 29:1, 188-204, DOI: 10.1080/02724634.2009.10010371

To link to this article: http://dx.doi.org/10.1080/02724634.2009.10010371

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ARTICLE

PHYLOGENETIC SUPPORT FOR A SPECIALIZED CLADE OF CRETACEOUSENANTIORNITHINE BIRDS WITH INFORMATION FROM A NEW SPECIES

JINGMAI K. O’CONNOR,*,1,2 XURI WANG,3 LUIS M. CHIAPPE,1 CHUNLING GAO,3 QINGJIN MENG,3

XIAODONG CHENG,3 and JINYUAN LIU3

1Dinosaur Institute, Natural History Museum of Los Angeles, 900 Exposition Boulevard, Los Angeles, CA 90007, U.S.A.2University of Southern California, 3651 Trousdale Parkway ZHS 117, Los Angeles, CA 90089 U.S.A., jingmai@usc.edu

3Dalian Natural History Museum, No. 40 Xicun Street Heishijiao Shahekou, District Dalian, P.R. China

ABSTRACT—A new species of enantiornithine bird from the Lower Cretaceous Yixian Formation of northeasternChina is reported. The new taxon, Shanweiniao cooperorum, possesses several enantiornithine synapomorphies as wellas the elongate rostral morphology (rostrum equal to or exceeding 60% the total length of the skull) of the Chinese earlyCretaceous enantiornithines, Longipteryx chaoyangensis and Longirostravis hani. The discovery of this new specimenhighlights the existence of a diverse clade of trophically specialized enantiornithines, Longipterygidae, for which wepresent phylogenetic support in a new comprehensive cladistic analysis of Mesozoic birds. Shanweiniao provides newinformation on the anatomy of longipterygids, and preserves a rectricial morphology previously unknown to enantior-nithines, with at least four tail feathers closely arranged. This supports the hypothesis that enantiornithines were strongfliers and adds to the diversity of known tail morphologies of these Cretaceous birds.

INTRODUCTION

Since their establishment as a clade less than three decadesago, Enantiornithes has become the most specieous group ofCretaceous birds known to science. A large portion of this diver-sity comes from the Lower Cretaceous (~125-120 Ma) Jehol( ) Group deposits of northeastern China (Fig. 1; Swisheret al., 2002; Zhu et al., 2007), a lithostratigraphic unit that hasyielded a wealth of early birds including taxa such as Confuci-usornis sanctus, Jeholornis prima, Liaoningornis longidigitrus,Yanornis martini, and Yixianornis grabaui (Zhang et al., 2003).

Though highly specieous, enantiornithines are morphological-ly very similar, and in this respect, often compared to themodern passerines (Chiappe, 2007). Although their cranialmorphology is not well known because the skull is missing,crushed, or fragmentary in most specimens, available data showthat most of these birds possess relatively short rostra, approxi-mately 50% of the total skull length. However, three enantior-nithines from the Jehol biota are known to possess a relativelyelongate rostrum, Longipteryx chaoyangensis (Zhang et al.,2001), Longirostravis hani (Hou et al., 2004) and a yet unnamedtaxon (Morschhauser et al., 2006). These taxa share several char-acteristics (elongate rostrum [here defined as a preorbital lengthequal to or exceeding 60% of the total skull length]; upperdentition limited to the premaxilla; lower dentition restricted tothe rostral tips of the dentaries; dentary long, slender, and ven-trally concave) (Hou et al., 2004; Zhang et al., 2001), whichsuggests they form a monophyletic group of trophicallyspecialized enantiornithine birds (Chiappe et al., 2006). Herewe describe a new taxon, Shanweiniao cooperorum, and providephylogenetic support for the formation of such a clade.

Institutional Abbreviations: DNHM, Dalian Natural HistoryMuseum; PKUP, Peking University.

Anatomical Abbreviations: See Appendix 1.

SYSTEMATIC PALEONTOLOGY

Aves Linnaeus, 1758Pygostylia Chiappe, 2002

Enantiornithes Walker, 1981Longipterygidae, Zhang et al. 2000

Phylogenetic Definition—The most recent common ancestorof Longipteryx chaoyangensis and Longirostravis hani and all itsdescendents.Included Taxa—Longipteryx chaoyangensis (Zhang et al.,

2001), Longirostravis hani (Hou et al., 2004), Shanweiniao coop-erorum, and a yet unnamed new taxon here referred to asDNHM D2522 (Morschhauser et al., 2006).Stratigraphic Distribution—Yixian and Jiufotang Formations

of the Jehol Group, Lower Cretaceous, 125-120 Ma (Swisheret al, 2002; He et al., 2004; Zhu et al., 2007).Geographic Distribution—Chaoyang, Lingyuan and Yixian,

western Liaoning Province, northeastern China.Diagnosis—Small to medium-sized enantiornithine birds with

the rostral portion of the skull equal to or exceeding 60% thetotal skull length; dentition restricted to the premaxilla androstral-most portion of the dentary; coracoid with nearly straightlateral margin.

Shanweiniao cooperorum gen. et sp. nov.(Figs. 2, 3)

Holotype—A nearly complete and largely articulated adultindividual preserved in a slab (Fig. 2) and counterslab (Fig. 3).The bones contained in the slab, DNHM D1878/1, are exposedprimarily in ventral view, while those in the counterslab, DNHMD1878/2, are mainly exposed in dorsal view. Feathers are pre-served as carbonized traces concentrated around the head,wings, and tail.Locality and Horizon—Lingyuan, Liaoning Province, China.

Dawangzhangzi Bed, middle Yixian Formation, Lower Creta-ceous (Swisher et al., 2002).*Corresponding author

Journal of Vertebrate Paleontology 29(1):188–204, March 2009# 2009 by the Society of Vertebrate Paleontology

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Etymology—“Shan wei niao ( )” meaning “fan-tail bird”in Chinese, refers to the fact that this specimen preserves the firstknown occurrence of an enantiornithine fan-shaped feathered tail.The species name is in honor of Carl and Lynn Cooper for theirgenerous support in the study of Mesozoic birds from China.Diagnosis—Shanweiniao cooperorum is a longipterygid enan-

tiornithine that possesses the unique combination of the follow-ing characters: elongate cranium that is 62% rostrum (64% inLongipteryx; 60%–64% in Longirostravis; 65% in DNHMD2522); second phalanx of manual major digit reduced andwedge-shaped (as in Longirostravis and DNHM D2522; unre-duced in Longipteryx); omal one-third of the clavicular ramidorsally curved; acute (40�) interclavicular angle (70� in Long-ipteryx; 55� in Longirostravis and DNHM D2522); clavicularsymphysis broad, exceeding the hypocleidium in length (short inLongipteryx, Longirostravis and DNHM D2522); sternum withsimple distal expansions of the lateral trabeculae (similar toLongipteryx; forked in DNHM D2522; branching, moose-hornmorphology in Longirostravis); intermembral index (humerus +ulna/femur + tibia) of 1.23 (Longipteryx = 1.48–1.51; Longiros-travis = 1.07; DNHM D2522 = 1.09); tarsometatarsus with meta-tarsal III longest and cranially convex, closely approached inlength (in order) by metatarsals IV and II (as in Longirostravisand DNHM D2522; IV longest in Longiptyerx); longitudinalcrest on central portion of pedal unguals; pedal unguals relati-vely unrecurved with large, curved keratinous sheaths; tail com-posed of at least four elongate rectrices.

ANATOMY

Anatomical nomenclature primarily follows Baumel and Wit-mer (1993) using the English equivalents of the Latin terms;certain structures not named therein follow Howard (1929).The skull is preserved in lateral view (Fig. 4). It is elongate

and delicate. The rostrum (measured from the rostral margin of

the orbit to the rostral margin of the premaxilla) constitutes 62%of the total skull length, slightly less than the percentage inLongipteryx and DNHM D2522 (estimated at 64% and 65%respectively), and within the range estimated for Longirostravis,60%–64%. The rostralmost tip of the skull is obscured whereit abuts wing bones, but the presence of alveoli and small teethcan be confirmed in the premaxilla, indicating that this birdshares with Longipteryx, Longirostravis and DNHM D2522 anedentulous maxilla but dentigerous premaxilla. A lone tooth canbe identified near the rostral portion of the left dentary (Fig. 4),but there is no evidence of either teeth or alveoli along themajority of the length of the dentaries, indicating that mandibu-lar teeth, if present, were also restricted to the rostral portion ofthe dentary, as in Longipteryx, Longirostravis and DNHMD2522. The proximally restricted teeth and overall delicate andelongate nature of the skull suggests that Shanweiniao mayalso have occupied the mudprobing niche of Longirostravis(Hou et al. 2004). Distal rhynchokinesis is often associated withthis ecological adaptation, however preservation makes it diffi-cult to determine if Shanweiniao (or Longirostravis) possessedthis specialization.Themandibles are straight (Fig. 4), lacking the ventral curvature

present in Longipteryx, Longirostravis and DNHM D2522. Bothdentaries are visible in DNHM D1878/2; the left mandible is pre-served in lateral view; a lateral groove paralleling the tomial edgeis marked with small, oval foramina. The right mandible is pre-served in medial view; although crushed, the articulation betweenthe dentary and surangular is visible. Fragments of thin, curvedbones interpreted as the angular bones are preserved below themandible and above the right dentary (Fig. 4). In DNHMD1878/1,the distal end of the left dentary is visible; the caudal end showsthe caudoventrally slanted and tapered ancestral condition(unforked), seen in Archaeopteryx lithographica (Elzanowski,2001) as well as in Longipteryx, Vescornis hebeiensis and Eoenan-tiornis buhleri (Zhang et al., 2004; Zhou et al., 2005).The frontal processes of the premaxilla are long, approaching

50% the length of the skull, but the ends are not preserved andtheir caudal extent cannot be ascertained. The jugal bar is pre-served but displaced dorsally, obscuring the morphology of theantorbital fenestra. The proximal end of the jugal is covered bythe broken and displaced proximal end of the left dentary. Theexternal nares appear to be retracted caudal to the rostralmostone-third of the skull. A curved bony margin preserved rostral tothe orbit is interpreted as the displaced caudal margin of the nares.The exact size, shape, and relative position of the nares and antor-bital fenestra cannot be determined. A sclerotic ring is preserved,but the number of individual ossicles is impossible to discern.

Vertebral Column

Approximately ten poorly preserved but articulatedvertebrae are preserved in ventral (DNHM D1878/1) and dorsal(DNHM D1878/2) view extending from the base of the skullto a point near the interclavicular symphysis (visible inDNHM D1878/1). The last vertebra appears to be associatedwith a long rib and is thus interpreted as a thoracic vertebra. Theexact position of the cervico-thoracic transition is difficult todetermine due to the poor preservation where the vertebraeintersect the pectoral girdle. The cervical series (eight or ninepreserved plus an atlas, for a minimum of nine total) appears tobe at least partially heterocoelous: in the seventh cervical,the cranial articular surface is visible and transversely concave.Nevertheless, the exact degree of heterocoely present through-out the cervical series cannot be determined. A small tuberclepresent on the dorsal margin of cervical five is interpreted as aspinous process. The postzygapophyses of the cervical vertebraeare well developed and project caudally beyond the vertebral bodyby a distance that exceeds one-third the vertebral bodies total

FIGURE 1. Map of Liaoning, China showing longipterygid fossil local-ities. The new taxon comes from the Lingyuan locality; Longirostravishani was collected near Yixian; and several Longipteryx specimens andan undescribed longipterygid (DNHM D2522) were found nearChaoyang.

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length. The shorter prezygapophyses extend cranially half thelengths of their caudal counterparts. Cervicals five, six, and sevenpreserve thin, elongate caudally directed ribs. The longest (cervicalfive) approaches the length of the vertebra. Two poorly preservedthoracic vertebrae are preserved distal to the sternum in DNHMD1878/2.

A portion of the synsacrum is displaced caudally between thetwo femora and exposed in ventral view in DNHM D1878/1(Fig. 3). The piece consists of two or three fused vertebrae; thetransverse processes are long, equal to the width of the vertebralbody, and project perpendicular to the axis of the synsacrum.The distal ends of the transverse processes are wider than theproximal portion. A groove preserved along the midline is inter-preted as a ventral sulcus, present also in DNHM D2522.

The pygostyle is broken; proximally, the right side bears aprocess reminiscent of the dorsal fork present in enantiornithinetaxa such as Longipteryx and Halimornis thompsoni (Chiappeet al., 2002). The distal margin is broken, although it was clearlyconstricted, as in Longipteryx, DNHM D2522, and Halimornis.In DNHM D1878/2, a pair of keel-like processes are visiblerunning parallel down the midline of the pygostyle; preservationmakes it difficult to ascertain in what view the pygostyle is pre-served, so these processes cannot be definitively correlated to

the paired ventral keels seen in the pygostyle of Halimornis(Chiappe et al., 2002). The number of vertebrae constituting thepygostyle likewise cannot be determined.Short, parallel sternal rib segments are preserved on either side of

the sternum. Visible thoracic rib segments appear to lack ossifieduncinate processes on both slabs. Gastralia, however, are present,preserved disarticulated between the sternum and the pelvis.

Pectoral Girdle

Both coracoids, preserved in articulation with the sternum,are strut-like. The sternal margin of each is concave as in Long-ipteryx, not straight as in Longirostravis and DNHM D2522. Thelateral margin is straight to slightly concave, as in Longirostravisand Longipteryx, not strongly convex as in some enantior-nithines (e.g., Concornis lacustris; Sanz et al., 1995). In DNHMD1878/2, a slight depression embays on the dorsal surface of thecoracoid. This depression is weak, unlike the deep fossae presentin some other enantiornithine taxa (Chiappe and Walker, 2002)and the basal ornithuromorph Apsaravis ukhaana (Clarke andNorell, 2002). The coracoid neck is simple, lacking a procoracoidprocess, as in other enantiornithines. No supracoracoideus nerveforamen is visible.

FIGURE 2. Holotype (DNHM D1878/1) of Shanweiniao cooperorum. A, photo; B, camera lucida drawing. See Appendix 1 for anatomicalabbreviations.

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In ventral view (DNHM D1878/2), the right scapula is pre-served in articulation with the right coracoid such that the bladeis covered by the coracoid. It possesses a robust and elongateacromion as in the Spanish enantiornithine Eoalulavis hoyasi(Sanz et al., 2002). In DNHM D1878/1 the scapular blade isexposed in costal view; it is long and straight, with no visiblegroove like those reported in the enantiornithine material fromEl Brete, Argentina (Chiappe and Walker, 2002). The scapulaexceeds the coracoid in length (Table 1; http://www.vertpaleo.org/publications/JVPContent.cfm); the distal end is blunt,tapering only very slightly.The furcula of Shanweiniao, preserved in DNHM D1878/1, is

narrow and Y-shaped. The morphology and exact length of thelong, poorly preserved hypocleidum relative to the rami cannotbe determined, though it is clearly at least one-third the lengthof either ramus. The rami are each approximately as long as thecoracoid. The omal one-third of each ramus is curved dorsallyand the omal tip slightly expanded. The caudal end of the clavi-cles fuse over a broad area so that the symphysial portion of thefurcula is nearly the same length as the hypocleideum unlikeother longipterygids in which the symphysis is restricted.

The interclavicular angle is acute, describing an angle of approx-imately 40�, which is much smaller than those of Longirostravis(55�) and Longipteryx (70�).The sternum is preserved in dorsal view (DNHM D1878/2)

but badly broken (Fig. 3). The proximal portion is displacedalong a small crack that runs diagonally through the element,offsetting the proximal portion of the right humerus as well(DNHM D1878/2). The cranial margin of the sternum appearsto be rounded. A large, well-preserved piece clearly shows themorphology of the right lateral and medial trabeculae, as well asthe morphology of the midline, which allows a confident recon-struction of its overall morphology (Fig. 5). The distal end of theright lateral trabecula is slightly broken, but the morphologyappears to have been relatively simple: straight with the distalend only slightly expanded. The cross-sectional profile of eachlateral trabecula appears to change from dorsoventrally ovalproximally to spatulate at the distal end, but this may be a pre-servational artifact. The branching, “moose-antler morphology”of Longirostravis remains an autapomorphy of that taxon. Themedial trabeculae are smaller than the lateral trabeculae (�one-third the length); their axes are slightly angled medially with

FIGURE 3. Holotype (DNHM D1878/2) of Shanweiniao cooperorum. A, photo; B, camera lucida drawing. See Appendix 1 for anatomicalabbreviations.

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respect to the lateral trabeculae and sternal midline. The caudalmargin of the sternum forms a relatively long xiphoid process,which projects slightly farther caudally than the lateral trabecu-lae, unlike Longirostravis and DNHM D2522 in which the later-al trabeculae project furthest. Distally as in the lateral trabecula,the xiphoid process expands slightly, and its distal margin isstraight. The distal end of the sternum, like Longipteryx, Long-irostravis and DNHM D2522, is imperforate, as opposed to thecondition in several ornithuromorph taxa (e.g., Yixianornis,Yanornis, and Songlingornis linghensis; Clarke et al., 2006).

Forelimb

The humerus is only partially preserved on both sides. Theproximal tip of the right humerus is preserved in DNHMD1878/2, broken and displaced; its head displays the typicalenantiornithine condition: concave on the midline, rising dor-sally and ventrally. The left humerus, preserved in pieces in bothslabs, indicates that the deltopectoral crest was weak, transver-sely measuring less than the width of the shaft. The distal margin(right humerus DNHMD1878/1) is angled, but not as strongly as

in some enantiornithines (e.g., Longipteryx, DNHM D2522,Alexornis antecedens; Brodkorb, 1976).The ulna and radius are nearly equal in length. The ulna is

robust, approaching the width of the humeral shaft. The ulna isslightly bowed, creating a proximal interosseous space betweenit and the radius that closes distally. The dorsal and ventralcondyles and the carpal tuberosity are visible on the distal endof the left ulna (DNHM D1878/2). The two condyles are weaklydeveloped and not separated by a deep sulcus; the dorsal con-dyle appears to form a semilunate ridge. The carpal tuberosity(also visible on the left side of DNHM D1878/2) is prominentand not separated from the ventral condyle by an incisure as insome neornithines (e.g., Cathartes).The radius is straight and half the width of the ulna. The

presence of a longitudinal groove cannot be determined.A cup-shaped structure preserved between the ulna, radius

and underlying metacarpal bones is interpreted as the carpaltrochlea of the carpometacarpus. An indeterminate fragmentlocated dorsolateral to the right manus in DNHM D1878/2 mayrepresent at least part of the ulnare or radiale.The manus of Shanweiniao is reduced, as in Longirostravis

and DNHM D2522; based on the available specimen, it appearsto be 2-2-1-x-x but is likely to have been 2-2-2-x-x, as inLongirostravis, which has two phalanges in the minor digit(personal observation), the second being extremely reduced.The alular digit is covered proximally by the ulna and radius.The distal half of the first phalanx of the alular digit is straight(DNHM D1878/2). A fragment in DNHM D1878/1 is inter-preted as the second phalanx; it is reduced and wedge-shaped,approximately the same size as the lone preserved minor digitphalanx. The major digit possesses two phalanges, lacking thelarge claw present in Longipteryx. The first phalanx is cylindricaland not dorsoventrally expanded as in more advanced birds(e.g., Gansus yummenensis, Neornithes; You et al., 2006). Thedistal phalanx is wedge-shaped and tapers distally. The singlepreserved phalanx of the minor digit is cylindrical in shape andapproximately the same size as the distal phalanx of the majordigit. The relative lengths of the metacarpals and the degree offusion present in the carpometacarpus cannot be determined.

Pelvic Girdle

The pelvic girdle is preserved primarily in DNHM D1878/2,including portions of both ilia and pubes (Fig. 3). Details of thepreacetabular wings of the ilia are not clear. The right acetabu-lum contains the broken head of the right femur. The pubicpeduncle is long, but it cannot be ascertained if the new taxonshares the same laterally compressed and hooked condition seenin Longirostravis and Longipteryx. The postacetabular wing of

FIGURE 4. Skull of Shanweiniao cooperorum in left lateral view.A, photo; B, camera lucida drawing. See Appendix 1 for anatomicalabbreviations.

TABLE 1. Selected measurements of longipterygid taxa in millimeters.

Longipteryx (holotype) Longirostravis Shanweiniao

Right Left Right Left Right Left

Skull, length 55.06 — (32.86) — (32.69) 31.36Rostrum (35.45) — (24.57) — (19.59)Coracoid 19.86 — (11.86) 13.57 (12.61) —Furcula — — 10.71 (10.17) (8.95) (8.44)Humerus (42.03) 43.48 (25.71) 23.51 22.43 (21.31)Ulna (47.1) 44.26 (25.14) (24.11) (23.36) —Radius (43.48) — 24.57 (21.43) (22.53) —Femur 28.77 28.26 — 19.43 — (17.6)Tibiotarsus — 30.07 25 25.17 22.41 22.61Tarsometatarsus — 19.2 13.74 — 11.75 11.9Pygostyle 21.38 13.57 (12.37)

Measurements of Shanweiniao are a composite of the slab and counterslab; see Table 1S (http://www.vertpaleo.org/publications/JVPContent.cfm)for a complete table of measurements.Parentheses denote estimated measurements; incomplete bones and measurements have been omitted.

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the left ilium, preserved in lateral view, is directed slightlyventrally, rendering the ventral margin concave. The distal endtapers, as in Longipteryx, DNHM D2522 and other enantior-nithines (e.g., Eoalulavis, Cathayornis yandica; Zhou, 1995; Sanzet al., 2002). The ventral margin of the ilium bears a large,rounded antitrochanter. The delicate, rod-like pubis is short,approximately equal to the femur in length, but more than twicethe length of the postacetabular wing of the ilium. The pubestogether form a caudally directed V, indicating that they werelikely retroverted. The distal ends, not preserved, approach eachother as if to form a short pubic symphysis.

Hindlimb

The hindlimb is shorter than the forelimb. The intermembralindex (ImI, measured as the sum of the lengths of the humerusand ulna divided by the sum of the lengths of the femur andtibiotarsus) measures approximately 1.23, intermediate betweenLongipteryx (ImI = 1.5) and Longirostravis (ImI = 1.07). InDNHM D1878/2, the left femur is preserved in ventral view andthe right femur in lateral view. The proximal portions of bothfemora are preserved in DNHM D1878/1. The femur is shorterthan the tibiotarsus and longer than the tarsometatarsus. Thefemur is slightly bowed craniocaudally; the head is round anddirected at an angle of 90� from the shaft. The trochanteric crestis separated from the femoral head by a distinct neck and pro-jects farther proximally than the femoral head. Distally, both afossa for the insertion of the capital ligament and a patellargroove are absent. In lateral view, the femur lacks the crestpresent in some enantiornithines (e.g., the El Brete material;Chiappe, 1996). A tibiofibular crest is also absent.Both tibiotarsi are preserved in DNHM D1878/2. Each is

more than double the length of the tarsometatarsus. The righttibiotarsus is preserved in lateral view and the left in caudalview. The lateral condyle is visible on the distal end of the righttibiotarsus. A faint fibular crest is visible 4 mm from the proxi-mal end of the right tibiotarsus. The fibula is preserved in articu-lation with the left tibiotarsus in DNHM D1878/2. Its proximalend is wedge shaped. The void of the left fibula in DNHMD1878/1 indicates the bone extended for at least half the lengthof the tibiotarsus.The feet are primarily preserved in dorsal view in DNHM

D1878/1 and in plantar view in DNHM D1878/2, although voidsof the dorsal view are also preserved in DNHM D1878/2. Thetarsometatarsus is short and proximally fused, with suture linesvisible distally. Proximally, an intercotylar eminence is absent.The metatarsals are subequal in mediolateral width. Distally,the third metatarsal extends farthest but is closely approachedby the fourth. The second metatarsal is the shortest, but itapproaches the metatarsal IV in length: the distal end of metatar-sal II surpasses the proximal end of the trochlea of metatarsal IV.Metatarsal I, preserved in lateral view, is reversed and

transversely compressed with a convex dorsal margin; whetherit was straight or J-shaped cannot be determined. Metatarsal Iarticulates low on the tarsometatarsus, as in Longipteryx andDNHM D2522. A dorsal tubercle on metatarsal II lies approxi-mately 3 mm from the proximal end of the tarsometatarsus. As inLongipteryx, it appears to be located more on the dorsal surfaceas opposed to the lateral surface of metatarsal II (e.g. Apsaravis;Clarke and Norell, 2002). Metatarsal III is transversely convexin dorsal view. In DNHM D1878/2, the left tarsometatarsus ispreserved in caudoventral view, and it is clear that a hypotarsusis absent.The feet are visible on both sides of both slabs; the left foot in

DNHM D1878/1 preserves the most information (Fig. 6). Thepedal phalangeal formula is 2-3-4-5-x. The first phalanx of thehallux is longer and more slender than the proximal phalanges ofdigits II–IV. In each digit, the penultimate phalanx is longer thanthe preceding phalanges. The total length of each digit, exceptthe hallux, exceeds the length of the tarsometatarsus. The firstphalanx of the second digit is approximately two-thirds thelength of the penultimate phalanx, which is the longest phalanxin the entire foot. The two proximal phalanges of digit III areapproximately equal to each other and shorter than the proximalphalanx in digit II. The penultimate phalanx in digit III is shorterthan that of digit II. The proximal three phalanges in digit IV aresubequal and each is approximately half the length of the penul-timate phalanx. The claws of all the pedal digits (including thehallux) are large, subequal in size and triangular in shape, lack-ing both strong degrees of curvature and strong flexor tubercles.The ungual of digit II, including its keratinous sheath, nearlyexceeds the length of the preceding two phalanges combined.A longitudinal crest on the central portion of the claw isvisible in the best-preserved unguals (left digits II and IV onDNHM D1878/1 and digit III in DNHM D1878/2) and is alsopresent in DNHM D2522 and ornithomimid theropods (e.g.,Struthiomimus altus, Harpymimus okladnikovi; Makovickyet al., 2004). Horny sheaths are preserved, giving the claws asickle shape. The sheaths appear to lack the distal constrictions

FIGURE 6. Left tarsometatarsus of Shanweiniao cooperorum in dorsalview. A, photo; B, camera lucida drawing. See Appendix 1 for anatomi-cal abbreviations.

FIGURE 5. Reconstruction of longipterygid sterni. A, Shanweiniaocooperorum; B, Longirostravis hani; C, Longipteryx chaoyangensis.

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interpreted as wear facets seen in some climbing birds (e.g.,Picoides; personal observation).

Integument

Carbonized traces of feathers are preserved throughout thespecimen. Wing feathers are present, but the exact number ofprimaries and secondaries is difficult to determine. The outer-most contour (presumed to be a primary) is estimated at 82 mm,measured from the impression of the right wing in DNHMD1878/1.

Tail rectrices are preserved in both slabs and are most clearlyvisible in DNHM D1878/1 (Fig. 7). Four rachises are clearlydiscernable, indicating the presence of four vaned, long andslender rectrices. The feathers are incomplete, missing theirproximal and distal ends. The vanes of these rectrices are paral-lel to one and another and directed toward the pygostyle. Theoutline of the right wing is complete in DNHM D1878/1 anddoes not overlap the retrices. The vanes of the wing feathers arealso directed at a different angle from that of the tail feathers,and thus we feel confident that these feather impressions do notrepresent wing elements. Because the distal most ends are notpreserved, it cannot be determined if the rectrices were graded,as in Yixianornis. Upper- and under-tail covert feathers are alsopreserved on the lateral margins of the pygostyle.

DISCUSSION

Phylogenetic Relationships of Shanweiniao

The phylogenetic position of Shanweiniao cooperorum wasdetermined using a modified version of the Chiappe (2002) data-set. The updated character list includes characters from Clarke(2002), enantiornithine characters from Chiappe and Walker(2002), as well as several new characters (Appendix 2). Twenty-nine taxa were scored for 242 characters. Thirty-one characterswere considered ordered; twenty-three characters were removedas uninformative with the current taxonomic sample (Appen-dix 2). Neornithes was represented by Anas platyrhynchos andGallus gallus, and Dromaeosauridae was used as the outgroup.The matrix (Appendix 3) was run using NONA (Goloboff,1993); optimal trees were identified using five random additionsequence replications of taxa, each followed by Tree BisectionReconnection (TBR) branch-swapping and 100 iterations ofjackknife ratchet, collapsing the trees on TBR rearrangements.The result was 20 most parsimonious trees of 588 steps. Thetrees differ within the relative placement of taxa within theenantiornithine and ornithuromorph clades.

The strict consensus tree (Fig. 8) places Shanweiniao withinEnantiornithes; the results agree with previous analyses (Clarkeet al., 2006; Zhou et al., 2005) in the placement of most taxa witha few significant differences. Zhongornis (Gao et al., 2008),Jeholornis, and Archaeopteryx form consecutive outgroups ofPygostylia with the confuciusornithid clade and Sapeornis asbasalmost pygostylians. Previous analyses have differed in theplacement of Sapeornis and Confuciusornis, placing the formerin a more basal position (Clarke et al., 2006; Zhou and Zhang,2002) and the latter as more derived, within the ornithothoracineclade (Zhou and Zhang, 2002). The results of this analysis placeSapeornis in a more derived position than Confuciusornithidae,as sister taxon to Ornithothoraces.

A large ornithothoracine clade is formed by Enantiorni-thes and Ornithuromorpha. Enantiornithine taxa form twopolytomies; the basal polytomy consists of Shanweiniao, Long-irostravis, Longipteryx and DNHM D2522, a relationshipsupported by three unambiguous synapomorphies (see Supple-mentary Data 2 at: http://www.vertpaleo.org/publications/JVPContent.cfm): upper dentition restricted to the premaxilla

FIGURE 7. Tail rectrices of Shanweiniao cooperorum in DNHMD1878/1. A, photo; B, camera lucida drawing.

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(5:1) with maxillary teeth absent (8:1) and the presence of adistally constricted pygostyle (79:1; a character known to occurin other enantiornithines) (Fig. 9). Within the longipterygids,Longirostravis and DNHM D2522 form a more exclusiveclade supported by two unambiguous synapomorphies: the pres-ence of outer sternal trabecula that project distally fartherthan the sternal midline (111:2) and an ulna/radius shaftwidth ratio that is greater than 0.7 (144:0, a reversal). A long-ipterygid clade formed by Longipteryx and Longirostraviswas previously supported (Chiappe et al., 2006) by two synapo-morphies: teeth restricted to the premaxilla and the presence ofan elongate rostrum. The current analysis expands the anatomi-cal support for the close relationship of these taxa and providesevidence for the existence of a more diverse longipterygid clade(Table 2).The second enantiornithine polytomy groups the remaining

taxa together, a result not surprising considering the results ofprevious Mesozoic bird analyses (Clarke et al., 2006; Chiappe,2002) and even enantiornithine specific matrices (Chiappe andWalker, 2002; Chiappe, et al., 2006) have failed to bring muchresolution to the clade. The relationships between enantior-nithine taxa presented in Zhou et al., (2006) are not supportedhere, which may be due to the inclusion of a larger number ofenantiornithine taxa in the current analysis.

Ornithuromorpha, a clade previously well resolved (Clarkeet al., 2006; Chiappe, 2002), has resulted in a polytomy, indicatingthe need for further work on this part of the tree. The consensustree places Patagopteryx basal to a large polytomy with theEarly Cretaceous Chinese hongshanornithids (Hongshanornislongicresta + PKUP V1069; O’Connor et al., in review) andornithurines nested within (Fig. 8). Within Ornithurae, Neor-nithes falls in a polytomy with Hesperornis regalis and Ichthyor-nis dispar; the Carinatae (Ichthyornis + Neornithes) clade is notsupported here.

Enantiornithine Tail Morphology

Shanweiniao preserves an elongate tail composed of at leastfour closely aligned rectrices, a previously unrecorded mor-phology. The typical enantiornithine tail morphology consistsof short coverts covering the pygostyle (Clarke et al., 2006),however, several species have been described possessing elon-gate streamer-like tail feathers; Protopteryx fengningensis(Zhang and Zhou, 2000) and Dapingfangornis sentisorhinus(Li et al., 2006) possess paired tail feathers, similar to thosepreserved in some specimens of Confuciusornis (Chiappe et al.,1999) and the recently named Paraprotopteryx gracilis has beendescribed with four (Zheng et al., 2007). The elongate rectrices

FIGURE 8. Strict consensus cladogram illustrating the phylogenetic position of Shanweiniao cooperorum. Tree length: 588 steps; consistency index= 48, retention index = 68.

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preserved in Paraprotopteryx, Protopteryx, Dapingfangornis,and Confuciusornis have often been interpreted as displaystructures, a conclusion that is supported here due to theirlength, splay and morphology (Chiappe et al., 1999; Zhangand Zhou, 2000; Li et al., 2006; Zheng et al., 2007). The distalends of the feathers in these taxa are preserved widely spaced,not closely aligned along their lengths in such a way as tocreate a surface capable of acting as an airfoil and thusgenerate any aerodynamic benefit. In contrast, the rachi of thefeathers preserved in Shanweiniao are closely arranged forminga continuous surface indicating that this tail had the potentialto act as an airfoil and generate lift. Whether the function ofthe tail in Shanweiniao was aerodynamic or for display isunclear given the incomplete preservation of the holotype,however the presence of this morphology among enantiorni-thines reveals the possibility that some members of the cladehad evolved this aerodynamic specialization.Among Mesozoic birds, Shanweiniao represents the second

known occurrence of a tail morphology capable of generatingsubstantial lift. Fan-shaped tails in Mesozoic taxa have onlybeen previously reported in a single specimen, the holotype ofYixianornis grabaui, a basal ornithurmorph (Clarke et al.,2006). Since the only previously known fan-shaped tail wasassociated with the anatomically modern, plough-shapedpygostyle of Yixianornis (also found in modern birds), it wassuggested that the fan-shaped tail and the bulb rectricium,which controls the fanning motion of the tail rectrices in mod-ern birds, coevolved with the ornithuromorph “plough-shaped”pygostyle morphology, and that the bulb rectricium was absentin the pygostyles of more basal birds, such as enantiornithinesand confuciusornithids (Clarke et al., 2006). The presence of afan-shaped tail outside the Yixianornis + Neornithes clade sug-gests that while it cannot be determined if a bulb rectriciumwas present in basal birds, it cannot be ruled out based onpygostyle or rectricial morphology. The retricial morphologyof Shanweiniao suggests the taxon may have possessed as bulbrectricium, which would imply the structure was not restrictedto Ornithuromorpha. Whether the bulb rectricium was presentin other enantiornithines (or widespread among), or whetherthe structure, if present, was homologous to that of modernbirds, cannot be determined with out additional specimens anda phylogenetic tree with higher resolution.Enantiornithines were first envisioned to be poor fliers (Walker,

1981) but the discovery of Neuquenornis (Chiappe, 1991)abolished this notion. The discovery of a specimen with an alulalent support to the latter view, that enantiornithines wereable fliers, comparable to modern birds (Sanz et al., 1996). A fan-shaped tail greatly increases aerodynamic performance throughincreased lift and maneuverability (Gatesy and Dial, 1996).The tail morphology preserved in Shanweiniao is the first amongenantiornithines, and the second among Mesozoic avians, to sug-gest the evolution of enhanced flight capabilities in the caudalregion. Enantiornithines developed flight specializations beyondthe skeletal level, having developed integumentary aerodynamicspecializations as well. This supports the hypothesis that enantior-nithines possessed sophisticated aerodynamic abilities, which like-ly facilitated their rapid diversification within the Cretaceous(Chiappe, 2007).

ACKNOWLEDGMENTS

We thank S. Abramowicz for preparing the illustrations,G. Takeuchi and D. Goodreau for the preparation of the speci-men, Zhou Z-H. and Zhang F-C. for kindly granting access tocomparative material at the Institute of Vertebrate Paleontologyand Paleoanthroplogy and D. Varricchio for providing access tounpublished material. We also thank J. Harris and two anony-mous reviewers for reading the manuscript and providing useful

FIGURE 9. Stratigraphic column showing the longipterygid bearingformations of the Jehol Group (modified from Zhou and Zhang, 2002;ages in Ma) and the temporal distributions of these taxa. Each taxon isknown only from point distributions; the elongate “ranges” indicate thelack of information regarding the exact bed from which the fossil wasextracted. Longirostravis hani is known only to come from the YixianFormation, while Shanweiniao cooperorum is known to come from the“Dawangzhangzi bed” of the Yixian.

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edits and comments. This research was funded by the NationalScience Foundation (DEB-0317140) and support from Carl andLynn Cooper, Ron and Judy Perlstein, and Richard and EileenGarson.

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Taxon Collection # Clade % Rostrum

Archaeopteryx, Thermopolis WDC-CSG-100 Archaeopterygidae 55Archaeoperyx, berlin HNM1880/81 Archaeopterygidae 50Archaeopteryx, Eischtatt Archaeopterygidae 55Confuciusornis sanctus GMV 2130 Confuciusornithidae 52Confuciusornis sanctus GMV 2132 Confuciusornithidae 54Sapeornis chaoyangensis DNHM D2523 Aves 54*Cathayornis indet. DNHM D9769 Enantiornithes 47–53*Protopteryx fengningensis IVPP V11665 Enantiornithes 47–55*Vescornis hebeiensis NIGP CAS

130722Enantiornithes 55*

Shanweiniao cooperorum DNHM D1878 Enantiornithes 62*Longipteryx chaoyangensis IVPP V12352 Enantiornithes 64Longipteryx chaoyangensis IVPP V12552 Enantiornithes 64Longipterygidae n sp. DNHM D2522 Enantiornithes 60*Hongshanornis longicresta IVPP V14533 Ornithuromorpha 53*Yanornis martini IVPP V13358 Ornithuromorpha 55–58*

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Submitted January 13, 2008; accepted July 30, 2008

APPENDIX 1. Anatomical abbreviations.

APPENDIX 2. Description of characters used in phylogenetic analysis.The matrix was run using 242 characters. Of these, 17 represent originalcharacters (5, 10, 41, 43, 46, 47, 67, 70, 71, 79, 101, 110, 111, 161, 176, 234,242), 110 are from the Chiappe (2002) dataset (2, 3, 6, 11, 14, 17-23, 26-28, 30, 36, 38, 48-51, 53, 54, 56, 60-63, 69, 72, 73, 75, 76, 82-84, 86, 89-91,96, 106, 109, 112, 113, 115, 120-122, 124, 126, 132, 134, 135, 139, 143, 144,148-150, 153, 157, 163, 165-168, 170-174, 179, 182-189, 192, 194, 195, 197-202, 204, 207-211, 217-221, 223, 224, 227, 229, 230, 236, 239, 241), 77 arefrom the Clarke (2002) dataset (8, 12, 13, 15, 16, 24, 25, 29, 31-35, 37, 39,40, 42, 44, 45, 52, 57, 58, 64, 65, 68, 74, 80, 81, 85, 87, 95, 97, 99, 100, 108,114, 116, 119, 127, 128, 130, 133, 136-138, 140-142, 145-147, 151, 152, 154-156, 158-160, 162, 164, 169, 178, 180, 181, 193, 203, 212-216, 225, 228, 232,233, 235), eight are from the Chiappe and Walker (2002) dataset (78, 88,94, 98, 102, 222, 237, 238), two are from the Clarke et al. (2006) dataset(118, 129) and four are from the Chiappe et al. (2006) dataset (55, 77,175, 196). An additional ten characters from the Chiappe (2002) datasethave been included in modified form (9, 66, 103-105, 107, 117, 177, 190,205), as have seven from Clarke (2002) (7, 59, 123, 131, 191, 206, 231) andsix that are modified versions of similar characters from both Clarke(2002) and Chiappe (2002) (1, 4, 92, 93, 125, 226). During the analysis,23 characters (16, 31, 34, 39, 40, 63, 64, 66, 69, 72, 74, 78, 99, 100, 101, 102,118, 179, 186, 193, 195, 206, and 222) were excluded on the basis they areuninformative in this analysis. Thirty-one characters are considered or-dered (see below).

Skull and Mandible

1. Premaxillae in adults: unfused (0); fused only rostrally (1); completelyfused (2). (ORDERED)

2. Maxillary process of the premaxilla: restricted to its rostral portion (0);subequal or longer than the facial contribution of the maxilla (1).

3. Frontal process of the premaxilla: short (0); relatively long,approaching the rostral border of the antorbital fenestra (1);very long, extending caudally near the level of lacrimals (2).(ORDERED)

4. Premaxillary teeth: present throughout (0); present but rostral tipedentulous (1); absent (2).

5. Upper dentition restricted to premaxilla: absent (0); present (1).6. Caudal margin of naris: far rostral than the rostral border of the

antorbital fossa (0); nearly reaching or overlapping the rostral borderof the antorbital fossa (1).

7. Naris longitudinal axis: considerably shorter than the long axis ofthe antorbital fossa (0); subequal or longer (1). We are using thelongitudinal axis of these structures as a proxy for their relative size.The longitudinal axis is often easier to measure than the actual areaenclosed by either the naris or the antorbital fossa.

8. Maxillary teeth: present (0); absent (1).9. Dorsal (ascending) ramus of the maxilla: present with two fenestra

(the promaxilllary and maxillary fenestra) (0); present with one fe-nestra (1); absent (2). (ORDERED)

al alular metacarpal nas nasalal I first phalanx, alular digit pmx premaxillaal II second phalanx alular digi pub pubisang angular pyg pygostylecau caudal vertebrae qd? possible quadratecmc carpometacarpus rad radiuscor coracoid rdn right dentarycrv cervical vertebrae rib ribsden dentary sca scapulafem femur scl sclerotic ringfur furcula stn sternumhum humerus sur surangularili ilium syn synsacrumjug jugal tbt tibiotarsusldn left dentary thv thoracic vertebraemac major metacarpal tmt tarsometatarsusma I first phalanx, major digit tth teethma II second phalanx, major digit uln ulnamax maxilla I - IV pedal digitsmi I first phalanx, minor digit I-(1 - 5) pedal phalangesmt I metatarsal one

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10. Caudal margin of choana: located rostrally, not overlapping the re-gion of the orbit (0); displaced caudally, at the same level or over-lapping the rostral margin of the orbit (1).

11. Rostral margin of the jugal: away from the caudal margin of the naris(0); or very close to (leveled with) the caudal margin of the naris (1).

12. Contact between palatine and maxilla/premaxilla: palatine contactmaxilla only (0); contacts premaxilla and maxilla (1).

13. Vomer and pterygoid articulation: present, well developed (0); re-duced, narrow process of pterygoid passes dorsally over palatine tocontact vomer (1); absent, pterygoid and vomer do not contact (2).

14. Jugal process of palatine: present (0); absent (1).15. Contact between palatine and pterygoid: long, craniocaudally over-

lapping contact (0); short, primarily dorsoventral contact (1).16. Contact between vomer and premaxilla: present (0); absent (1).17. Ectopterygoid: present (0); absent (1).18. Postorbital: present (0); absent (1).19. Contact between postorbital and jugal: present (0); absent (1).20. Quadratojugal: sutured to the quadrate (0); joined through a liga-

mentary articulation (1).21. Lateral, round cotyla on the mandibular process of the quadrate

(quadratojugal articulation): absent (0); present (1).22. Contact between the quadratojugal and squamosal: present (0); ab-

sent (1).23. Squamosal incorporated into the braincase, forming a zygomatic

process: absent (0); present (1).24. Squamosal, ventral or “zygomatic” process: variably elongate, dor-

sally enclosing otic process of the quadrate and extending cranioven-trally along shaft of this bone, dorsal head of quadrate not visible inlateral view (0); short, head of quadrate exposed in lateral view (1).

25. Frontal/parietal suture in adults: open (0); fused (1).26. Quadrate orbital process (pterygoid ramus): broad (0); sharp and

pointed (1).27. Quadrate pneumaticity: absent (0); present (1).28. Quadrate: articulating only with the squamosal (0); articulating with

both prootic and squamosal (1).29. Otic articulation of the quadrate: articulates with a single facet

(squamosal) (0); articulates with two distinct facets (prootic andsquamostal) (1); articulates with two distinct facets and quadratedifferentiated into two heads (2). (ORDERED)

30. Quadrate distal end: with two transversely aligned condyles (0); witha triangular, condylar pattern, usually composed of three distinctcondyles (1).

31. Basipterygoid processes: long (0); short (articulation with pterygoidsubequal to, or longer than, amount projected from the basisphenoidrostrum) (1).

32. Pterygoid, articular surface for basipterygoid process: concave “sock-et”, or short groove enclosed by dorsal and ventral flanges (0); flat toconvex (1); flat to convex facet, stalked, variably projected (2). (OR-DERED)

33. Eustachian tubes: paired, lateral, and well-separated from each other(0); paired, close to each other and to cranial midline or forming asingle cranial opening (1).

34. Osseous interorbital septum (mesethmoid): absent (0); present (1).35. Dentary teeth: present (0); absent (1).36. Dentary tooth implantation: teeth in individual sockets (0); teeth in a

communal groove (1).37. Symphysial portion of dentaries: unfused (0); fused (1).38. Deeply notched rostral end of the mandibular symphysis: absent (0);

present (1).39. Mandibular symphysis, symphyseal foramina: absent (0); single (1);

paired (2).40. Mandibular symphysis, symphyseal foramen/foramina: opening

on caudal edge of symphysis (0); opening on dorsal surface of sym-physis (1).

41. Small ossification present at the rostral tip of the mandibular sym-physis (intersymphysial ossification): absent (0); present (1). Martin(1987:13) refers to this ossification as the “predentary.” This term isinappropriate as it implies a homology between this ossification andthe predentary bone of ornithischian dinosaurs—a hypothesis that isnot supported by parsimony.

42. Caudal margin of dentary strongly forked: unforked, or with a weaklydeveloped dorsal ramus (0); strongly forked with the dorsal andventral rami approximately equal in caudal extent (1).

43. Mandibular ramus sigmoidal such that the rostral tip is dorsally convexand the caudal end is dorsally concave: absent (0); present (1).

44. Cranial extent of splenial: stops well caudal to mandibular symphysis(0); extending to mandibular symphysis, though noncontacting (1);extending to proximal tip of mandible, contacting on midline (2).(ORDERED)

45. Meckel’s groove (medial side of mandible): not completely coveredby splenial, deep and conspicuous medially (0); covered by splenial,not exposed medially (1).

46. Rostral mandibular fenestra: absent (0); present (1).47. Caudal mandibular fenestra: present (0); absent (1). We regard the

caudal mandibular fenestra of neornithines as homologous to thesurangular fenestra of non-avian dinosaurs (Chiappe, 2002).

48. Articular pneumaticity: absent (0); present (1).49. Teeth: serrated crowns (0); unserrated crowns (1).

Vertebral Column and Ribs

50. Atlantal hemiarches in adults: unfused (0); fused, forming a singlearch (1).

51. One or more pneumatic foramina piercing the centra of mid-cranialcervicals, caudal to the level of the parapophysis-diapophysis: pres-ent (0); absent (1).

52. Cervical vertebrae: variably dorsoventrally compressed, amphicoe-lous (“biconcave”: flat to concave articular surfaces) (0); cranialsurface heterocoelous (i.e., mediolaterally concave, dorsoventrallyconvex), caudal surface flat or slightly concave (1); heterocoelouscranial (i.e., mediolaterally concave, dorsoventrally convex) andcaudal (i.e., mediolaterally convex, dorsoventrally concave) sur-faces (2). (ORDERED)

53. Prominent carotid processes in the intermediate cervicals: absent(0); present (1).

54. Postaxial cervical epipophyses: prominent, projecting further backfrom the postzygapophysis (0); weak, not projecting further backfrom the postzygapophysis, or absent (1).

55. Keel-like ventral surface of cervical centra: absent (0); present (1).56. Prominent (50% or more the height of the centrum’s cranial articu-

lar surface) ventral processes of the cervicothoracic vertebrae:absent (0); present (1).

57. Thoracic vertebral count: 13-14 (0); 11-12 (1); fewer than 11 (2).The transition between cervical and thoracic vertebrae is oftendifficult to identify, which makes counting these vertebrae problem-atic. Here, thoracic vertebrae are defined as possessing free, ven-trally projecting ribs. When inarticulated, vertebral morphologyshould be used. (ORDERED)

58. Thoracic vertebrae: at least part of series with subround, centralarticular surfaces (e.g., amphicoelous/opisthocoelous) that lack thedorsoventral compression seen in heterocoelous vertebrae (0);series completely heterocoelous (1).

59. Caudal thoracic vertebrae, centra, length and midpoint width:approximately equal in length and midpoint width (0); length mark-edly greater than midpoint width (1).

60. Wide vertebral foramen in the mid-caudal thoracic vertebrae, ver-tebral foramen/articular cranial surface ratio (vertical diameter)larger than 0.40: absent (0); present (1).

61. Hyposphene-hypantrum accessory intervertebral articulations inthe thoracic vertebrae: present (0); absent (1).

62. Lateral side of the thoracic centra: weakly or not excavated (0);deeply excavated by a groove (1); excavated by a broad fossa (2).

63. Cranial thoracic vertebrae, parapophyses: located in the cranial partof the centra of the thoracic vertebrae (0); located in the centralpart of the centra of the thoracic vertebrae (1).

64. Notarium: absent (0); present (1).65. Sacral vertebrae, number ankylosed (synsacrum): less than 7 (0); 7 (1);

8 (2); 9 (3); 10 (4); 11 or more (5); 15 or more (6). (ORDERED)66. Synsacrum, procoelous articulation with last thoracic centrum

(deeply concave facet of synsacrum receives convex articulation oflast thoracic centrum): absent (0); present (1).

67. Cranial vertebral articulation of first sacral vertebra: approximatelyequal in height and width (0); wider than high (1).

68. Series of short sacral vertebrae with dorsally directed parapophysesjust cranial to the acetabulum: absent (0); present, three such ver-tebrae (1); present, four such vertebrae (2). (ORDERED)

69. Convex caudal articular surface of the synsacrum: absent (0); pres-ent (1).

70. Degree of fusion of distal caudal vertebrae: fusion absent (0);few vertebrae partially ankylosed (intervening elements are

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well-discernable) (1); vertebrae completely fused into a pygostyle(2). (ORDERED)

71. Free caudal vertebral count: more than 35 (0); 35-26 (1); 25 - 20 (2);19-9 (3); 8 or less (4). (ORDERED)

72. Procoelous caudals: absent (0); present (1).73. Distal caudal vertebra prezygapophyses: elongate, exceeding the

length of the centrum by more than 25% (0); shorter (1); absent(2). (ORDERED)

74. Free caudals, length of transverse processes: approximately equalto, or greater than, centrum width (0); significantly shorter thancentrum width (1).

75. Proximal haemal arches: elongate, at least 3 times longer than wider(0); shorter (1); absent (2). (ORDERED)

76. Pygostyle: longer than or equal to the combined length of the freecaudals (0); shorter (1).

77. Cranial end of pygostyle dorsally forked: absent (0); present (1).78. Cranial end of pygostyle with a pair of laminar, ventrally projected

processes: absent (0); present (1).79. Distal constriction of pygostyle: absent (0); present (1). In the

pygostyles of some enantiornithine taxa, the distal-most mediolat-eral width is reduced so that the midline of the pygostyle projectsdistally farther than the lateral margins (Chiappe et al., 2002).

80. Ossified uncinate processes in adults: absent (0); present and free(1); present and fused (2).

81. Gastralia: present (0); absent (1).

Thoracic Girdle and Sternum

82. Coracoid shape: rectangular to trapezoidal in profile (0); strut-like (1).

83. Coracoid and scapula articulation: through a wide, sutured articula-tion (0); through more localized facets (1).

84. Scapula: articulated at the shoulder (proximal) end of the coracoid(0); well below it (1).

85. Coracoid, humeral articular (glenoid) facet: dorsal to acrocoracoidprocess/“biceps tubercle” (0); ventral to acrocoracoid process (1).

86. Humeral articular facets of the coracoid and the scapula: placed inthe same plane (0); forming a sharp angle (1).

87. Coracoid, acrocoracoid: straight (0); hooked medially (1).88. Laterally compressed shoulder end of coracoid, with nearly aligned

acrocoracoid process, humeral articular surface, and scapular facet,in dorsal view: absent (0); present (1).

89. Procoracoid process on coracoid: absent (0); present (1).90. Distinctly convex lateral margin of coracoid: absent (0); present (1).91. Broad, deep fossa on the dorsal surface of the coracoid (dorsal

coracoidal fossa): absent (0); present (1).92. Supracoracoidal nerve foramen of coracoid: centrally located (0);

displaced toward (often as an incisure) the medial margin of thecoracoid (1); displaced so that it nerve no longer passes through thecoracoid (absent) (2). (ORDERED) In some taxa the n. supracor-acoideus does not pierce the coracoid, but is assumed to pass medi-ally at the level between the bone’s midpoint and its glenoid(humeral articular facet).

93. Coracoid, medial surface, strongly depressed elongate furrow at thelevel of the passage of n. supracoracoideus: absent (0); present (1).

94. Supracoracoid nerve foramen, location relative to dorsal coracoidalfossa: above fossa (0); inside fossa (1).

95. Coracoid, lateral process (sternocoracoidal process): absent (0);present (1).

96. Scapular shaft: straight (0); sagittally curved (1).97. Scapula, length: shorter than humerus (0); as long as or longer than

humerus (1).98. Scapular acromion costolaterally wider than deeper: absent (0);

present (1).99. Scapula, acromion process: projected cranially surpassing the artic-

ular surface for coracoid (facies articularis coracoidea; Baumel andWitmer, 1993 ) (0); projected less cranially than the articular sur-face for coracoid (1).

100. Scapula, acromion process: straight (0); laterally hooked tip (1).101. Proximal end of scapula, pit between acromion and humeral articu-

lar facet: absent (0); present (1).102. Costal surface of scapular blade with prominent longitudinal fur-

row: absent (0); present (1).103. Scapular caudal end: blunt (may or may not be expanded) (0);

tapered (1).

104. Furcular, shape: boomerang-shaped (0); V to Y-shaped (1);U-shaped (2).

105. Furcula interclavicular angle: approximately 90� (0); less than 70�(1). The interclavicular angle is measured as the angle formed be-tween three points, one at the omal end of each rami and the apexlocated at the clavicular symphysis.

106. Dorsal and ventral margins of the furcula: subequal in width (0);ventral margin distinctly wider than the dorsal margin so that thefurcular ramus appears concave laterally (1).

107. Hypocleideum: absent (0); present as a tubercle or shortprocess (1); present as an elongate process approximately 30% ramilength (2); hypertrophied, exceeding 50% rami length (3). OR-DERED

108. Ossified sternum: two flat plates (0); single flat element (1); singleelement, with slightly raised midline ridge (2); single element, withprojected carina (3).

109. Sternal carina: near to, or projecting rostrally from, the cranialborder of the sternum (0); not reaching the cranial border of thesternum (1).

110. Sternum, caudal margin, number of paired caudal trabecula: none(0); one (1); two (2). The use of “lateral” and “medial” to identifythe specific sternal processes is abandoned here due to the difficultyof identifying trabecula when only one is present. Eoenantiornis isscored as a “?” due to the uncertain status of the sternal processes;it is possible that the identified “lateral process” (Zhou et al. 2005)is actually the distal humerus.

111. Sternum, outermost trabecula, shape: tips terminate cranial to cau-dal end of sternum (0); tips terminate at or approaching caudal endof sternum (1); tips extend caudally past the termination of thesternal midline (2).

112. Prominent distal expansion in the outermost trabecula of the ster-num: absent (0); present (1).

113. Rostral margin of the sternum broad and rounded: absent (0); pres-ent (1).

114. Sternum, coracoidal sulci spacing on cranial edge: widely separatedmediolaterally (0); adjacent (1); crossed on midline (2). In taxa suchas Eoalulavis in which the preserved sternum does not bear actualsulci, the placement of the coracoids can be used to infer theirposition relative to the sternum.

115. Costal facets of the sternum: absent (0); present (1).116. Sternal costal processes: three (0); four (1); five (2); six (3); seven

(4); eight (5). (ORDERED)117. Sternal midline, caudal end: blunt W-shape (0); V-shape (1); elon-

gate straight projection (xiphoid process) (2); flat (3); rounded (4).118. Sternum, caudal half, paired enclosed fenestra: absent (0); pres-

ent (1).119. Sternum, dorsal surface, pneumatic foramen (or foramina): absent

(0); present (1).

Thoracic Limb

120. Proximal and distal humeral ends: twisted (0); expanded nearly inthe same plane (1).

121. Humeral head: concave cranially and convex caudally (0); globeshaped, craniocaudally convex (1).

122. Proximal margin of the humeral head concave in its central portion,rising ventrally and dorsally: absent (0); present (1).

123. Humerus, proximocranial surface, well-developed circular fossa onmidline: absent (0); present (1).

124. Humerus with distinct transverse ligamental groove: absent (0);present (1).

125. Humerus, ventral tubercle projected caudally, separated from hu-meral head by deep capital incision: absent (0); present (1).

126. Pneumatic fossa in the caudoventral corner of the proximal end ofthe humerus: absent or rudimentary (0); well developed (1).

127. Humerus, deltopectoral crest: projected dorsally (in line with thelong axis of humeral head) (0); projected cranially (1).

128. Humerus, deltopectoral crest: less than shaft width (0); approxi-mately same width (1); prominent and subquadrangular (i.e., sub-equal length and width) (2).

129. Humerus, deltopectoral crest, perforated by a large fenestra: absent(0); present (1).

130. Humerus, bicipital crest: little or no cranial projection (0); devel-oped as a cranial projection relative to shaft surface in ventral view(1); hypertrophied, rounded tumescence (2).

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131. Humerus, distal end of bicipital crest, pit-shaped fossa for muscularattachment: absent (0); craniodistal on bicipital crest (1); directlyventrodistal at tip of bicipital crest (2); caudodistal, variably devel-oped as a fossa (3).

132. Distal end of the humerus very compressed craniocaudally: absent(0); present (1).

133. Humerus, demarcation of muscle origins (e.g., m. extensor meta-carpi radialis in Aves) on the dorsal edge of the distal humerus: noindication of origin as a scar, a pit, or a tubercle (0); indication as apit-shaped scar or as a variably projected scar-bearing tubercle orfacet (1).

134. Well-developed brachial depression on the cranial face of the distalend of the humerus: absent (0); present (1). We interpret the bra-chial fossa not as a depression on the craniodistal end of the humer-us but as a distinct scar for muscle attachment.

135. Well-developed olecranon fossa on the caudal face of the distal endof the humerus: absent (0); present (1).

136. Humerus, distal end, caudal surface, groove for passage of m. sca-pulotriceps: absent (0); present (1).

137. Humerus, m. humerotricipitalis groove: absent (0); present as a well-developed ventral depression contiguous with the olecranon fossa (1).

138. Humerus, distal margin: approximately perpendicular to long axisof humeral shaft (0); ventrodistal margin projected significantlydistal to dorsodistal margin, distal margin angling strongly ventrally(sometimes described as a well-projected flexor process) (1).

139. Humeral distal condyles: mainly located on distal aspect (0); oncranial aspect (1).

140. Humerus, long axis of dorsal condyle: at low angle to humeral axis,proximodistally oriented (0); at high angle to humeral axis, almosttransversely oriented (1).

141. Humerus, distal condyles: subround, bulbous (0); weakly defined,“straplike” (1).

142. Humerus, ventral condyle: length of long axis of condyle less thanthe same measure of the dorsal condyle (0); same or greater (1).

143. Ulna: shorter than humerus (0); nearly equivalent to or longer thanhumerus (1).

144. Ulnar shaft, radial-shaft/ulnar-shaft ratio: larger than 0.70 (0); smal-ler than 0.70 (1).

145. Ulna, cotylae: dorsoventrally adjacent (0); widely separated by adeep groove (1).

146. Ulna, dorsal cotyla strongly convex: absent (0); present (1).147. Ulna, bicipital scar: absent (0); developed as a slightly raised scar

(1); developed as a conspicuous tubercle (2).148. Proximal end of the ulna with a well-defined area for the insertion

of m. brachialis anticus: absent (0); present (1).149. Semilunate ridge on the dorsal condyle of the ulna: absent (0);

present (1).150. Shaft of radius with a long longitudinal groove on its ventrocaudal

surface: absent (0); present (1).151. Ulnare: heart-shaped with little differentiation into short rami (0);

U-shaped to V-shaped, well-developed rami (1).152. Ulnare, ventral ramus (crus longus, Baumel and Witmer, 1993):

shorter than dorsal ramus (crus brevis) (0); same length as dorsalramus (1); longer than dorsal ramus (2).

153. Semilunate carpal and proximal ends of metacarpals in adults: un-fused (0); semilunate fused to the alular (I) metacarpal (1); semilu-nate fused to the major (II) and minor (III) metacarpals (2); fusionof semilunate and all metacarpals (3). Any specimen that is inferredto be a juvenile should be scored as a “?” in order to account for thepossibility of ontogenetic change.

154. Semilunate carpal, position relative to the alular metacarpal (I):over entire proximal surface (0); over less than one-half proximalsurface or no contact present (1).

155. Pisiform process: absent (0); present (1).156. Carpometacarpus, ventral surface, infratrochlear fossa deeply exca-

vating proximal surface of pisiform process: absent (0); present (1).157. Round-shaped alular metacarpal (I): absent (0); present (1).158. Alular metacarpal (I), extensor process: absent, no cranioproxi-

mally projected muscular process (0); present, tip of extensor pro-cess just surpassed the distal articular facet for phalanx 1 in cranialextent (1); tip of extensor process conspicuously surpasses articularfacet by approximately half the width of facet, producing a pro-nounced knob (2); tip of extensor process conspicuously surpassesarticular facet by approximately the width of facet, producing apronounced knob (3). (ORDERED)

159. Alular metacarpal (I), distal articulation with phalanx I: ginglymoid(0); shelf (1).

160. Metacarpal III, craniocaudal diameter as a percentage of samedimension of metacarpal II: approximately equal or greater than50% (0); less than 50% (1).

161. Proximal extension of metacarpal III: level with metacarpal II (0);ending distal to proximal surface of metacarpal II (1).

162. Intermetacarpal process or tubercle on metacarpal II: absent (0);present as scar (1); present as tubercle or flange (2).

163. Intermetacarpal space: absent or very narrow (0); at least as wide asthe maximum width of minor metacarpal (III) shaft (1).

164. Intermetacarpal space: reaches proximally as far as the distal end ofmetacarpal I (0); terminates distal to end of metacarpal I (1).

165. Distal end of metacarpals: unfused (0); partially or completelyfused (1).

166. Minor metacarpal (III) projecting distally more than the majormetacarpal (II): absent (0); present (1).

167. Alular digit (I): long, exceeding the distal end of the major meta-carpal (0); subequal (1); short, not surpassing this metacarpal (2).(ORDERED)

168. Proximal phalanx of major digit (II): of normal shape (0); flat andcraniocaudally expanded (1).

169. Major digit (II), phalanx 1, “internal index process” (Stegmann,1978) on caudodistal edge: absent (0); present (1).

170. Intermediate phalanx of major digit (II): longer than proximalphalanx (0); shorter than or equivalent to proximal phalanx (1).

171. Ungual phalanx of major digit (II): present (0); absent (1).172. Ungual phalanx of major digit (II) much smaller than the unguals of

the alular (I) and minor (III) digits: absent (0); present (1).173. Proximal phalanx of theminor digit (III) much shorter than the remain-

ing non-ungual phalanges of this digit: absent (0); present (1).174. Ungual phalanx of minor digit (III): present (0); absent (1).175. Length of manus (semilunate carpal + major metacarpal and digit)

relative to humerus: longer (0); subequal (1); shorter (2). (OR-DERED)

176. Intermembral index = (length of humerus + ulna)/(length of femur+ tibiotarsus): less than 0.7, flightless (0); between 0.7 and 0.9 (1);between 0.9 and 1.1 (2); greater than 1.1 (3).

Pelvic Girdle

177. Pelvic elements in adults, at the level of the acetabulum: unfused orpartial fusion (0); completely fused (1).

178. Ilium/ischium, distal co-ossification to completely enclose theilioischiadic fenestra: absent (0); present (1).

179. Preacetabular process of ilium twice as long as postacetabular pro-cess: absent (0); present (1).

180. Preacetabular ilium: approach on midline, open, or cartilaginousconnection (0); co-ossified, dorsal closure of “iliosynsacralcanals” (1).

181. Ilium, m. cuppedicus fossa as broad, mediolaterally oriented surfacedirectly cranioventral to acetabulum: present (0); surface absent,insertion variably marked by a small entirely lateral fossa cranialto acetabulum (1).

182. Preacetabular pectineal process (Baumel and Witmer, 1993): absent(0); present as a small flange (1); present as a well-projected flange(2). (ORDERED)

183. Small acetabulum, acetabulum/ilium length ratio equal to or smal-ler than 0.11: absent (0); present (1).

184. Prominent antitrochanter: caudally directed (0); caudodorsally di-rected (1).

185. Supracetabular crest on ilium: well developed (0); absent or rudi-mentary (1).

186. Supracetabular crest: extending throughout the acetabulum (0);extending only over the cranial half of the acetabulum (1).

187. Postacetabular process shallow, less than 50% of the depth of thepreacetabular wing at the acetabulum: absent (0); present (1).

188. Iliac brevis fossa: present (0); absent (1).189. Ischium: two-thirds or less the length of the pubis (0); more than

two-thirds the length of the pubis (1).190. Obturator process of ischium: prominent (0); reduced or absent

(1). The ischium of Archaeopteryx is forked distally; the thicker cra-nioventrally oriented fork is here interpreted to be the obturatorprocess.

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191. Ischium, caudal demarcation of the obturator foramen: absent (0);present, developed as a small flange or raised scar contacting/fusedwith pubis and demarcating the obturator foramen distally (1).

192. Ischium with a proximodorsal (or proximocaudal) process: absent(0); present (1).

193. Ischiadic terminal processes forming a symphysis: present (0); ab-sent (1).

194. Orientation of proximal portion of pubis: cranially to subverticallyoriented (0); retroverted, separated from the main synsacral axis byan angle ranging between 65� and 45� (1); more or less parallel tothe ilium and ischium (2). (ORDERED)

195. Pubic pedicel: cranioventrally projected (0); ventrally or caudoven-trally projected (1).

196. Pubic pedicel of ilium very compressed laterally and hook-like:absent (0), present (1).

197. Pubic shaft laterally compressed throughout its length: absent (0);present (1).

198. Pubic apron: one-third or more the length of the pubis (0); shorter(1); absent (absence of symphysis) (2). (ORDERED)

199. Pubic foot: present (0); absent (1).

Pelvic Limb

200. Femur with distinct fossa for the capital ligament: absent (0); pres-ent (1).

201. Femoral neck: present (0); absent (1).202. Femoral anterior trochanter: separated from the greater trochanter

(0); fused to it, forming a trochanteric crest (1).203. Femoral posterior trochanter: present, developed as a slightly pro-

jected tubercle or flange (0); hypertrophied, “shelf-like” conforma-tion (1) (in combination with development of the trochanteric shelf;see Hutchinson, 2001); absent (2).

204. Femur with prominent patellar groove: absent (0); present (1).205. Femur: ectocondylar tubercle and lateral condyle separated by

deep notch (0); ectocondylar tubercle and lateral condyle contigu-ous but without developing a tibiofibular crest (1); tibiofibular crestpresent, defining laterally a fibular trochlea (2). Proximal to thelateral condyle in theropod dinosaurs there is a caudal projectionknown as the ectocondylar tubercle (Welles, 1984). It is hypothe-sized that this tubercle is homologous to the precursor to the tibio-fibular crest, formed through the connection of the ectocondylartubercle and the lateral condyle (Chiappe 1996). (ORDERED)

206. Caudal projection of the lateral border of the distal end of thefemur, proximal and contiguous to the ectocondylar tubercle/tibio-fibular crest: absent (0); present (1).

207. Femoral popliteal fossa distally bounded by a complete transverseridge: absent (0); present (1).

208. Fossa for the femoral origin of m. tibialis cranialis: absent (0);present (1).

209. Tibia, calcaneum, and astragalus: unfused or poorly co-ossified(sutures still visible) (0); complete fusion of tibia, calcaneum, andastragalus (1).

210. Round proximal articular surface of tibiotarsus: absent (0); present (1).211. Cranial cnemial crest on tibiotarsus: absent (0); present (1).212. Tibia, caudal extension of articular surface for distal tarsals/tarso-

metatarsus: absent, articular restricted to distalmost edge of caudalsurface (0); well-developed caudal extension, sulcus cartilaginistibialis of Aves (Baumel and Witmer, 1993), distinct surfaceextending up the caudal surface of the tibiotarsus (1); with well-developed, caudally projecting medial and lateral crests (2).(ORDERED)

213. Extensor canal on tibiotarsus: absent (0); present as an emarginategroove (1); groove bridged by an ossified supratendinal bridge (2).(ORDERED)

214. Tibia/tarsal-formed condyles: medial condyle projecting farther cra-nially than lateral condyle (0); equal in cranial projection (1).

215. Tibia/tarsal-formed condyles, mediolateral widths: medial condylewider (0); approximately equal (1); lateral condyle wider (2). (OR-DERED)

216. Tibia/tarsal-formed condyles: gradual sloping of condyles towardsmidline of tibiotarsus (0); no tapering of either condyle (1).

217. Proximal end of the fibula: prominently excavated by a medial fossa(0); nearly flat (1).

218. Fibula, tubercle for m. iliofibularis: craniolaterally directed (0); lat-erally directed (1); caudolaterally or caudally directed (2). (OR-DERED)

219. Fibula, distal end reaching the proximal tarsals: present (0); absent (1).220. Distal tarsals in adults: free (0); completely fused to the metatarsals

(1). Any specimen that is inferred to be a juvenile should be scoredas a “?” in order to account for the possibility of ontogenetic change.

221. Metatarsals II-IV completely (or nearly completely) fused to eachother: absent (0); present (1).

222. Proximal end of metatarsus: plane of articular surface perpendicularto longitudinal axis of metatarsus (0); strongly inclined dorsally (1).

223. Metatarsal V: present (0); absent (1).224. Proximal end of metatarsal III: in the same plane as metatarsals II and

IV (0); plantarly displaced with respect to metatarsals II and IV (1).225. Tarsometatarsal proximal vascular foramen/foramina: absent (0);

one between metatarsals III and IV (1); two (2).226. Metatarsals, relative mediolateral width: metatarsal IV approxi-

mately the same width as metatarsals II and III (0); metatarsal IVnarrower than metatarsals II and III (1); metatarsal IV greater inwidth than either metatarsal II or III (2).

227. Well-developed tarsometatarsal intercotylar eminence: absent (0);present (1).

228. Tarsometatarsus, projected surface and/or grooves on proximocau-dal surface (associated with the passage of tendons of the pes flex-ors in Aves; hypotarsus): absent (0); developed as caudal projectionwith flat caudal surface (1); projection, with distinct crests andgrooves (2); at least one groove enclosed by bone caudally (3).(ORDERED)

229. Plantar surface of tarsometatarsus excavated: absent (0); present (1).230. Tarsometatarsal distal vascular foramen completely enclosed by

metatarsals III and IV: absent (0); present (1).231. Metatarsal I: straight (0); J-shaped, the articulation of the hallux

is located on the same plane as the attachment surface of themetatarsal I (1); J-shaped; the articulation of the hallux is perpen-dicular to the attachment surface (2); the distal half of the meta-tarsal I is laterally deflected so that the laterodistal surface isconcave (3).

232. Metatarsal II tubercle (associated with the insertion of the tendonof the m. tibialis cranialis in Aves): absent (0); present, on approxi-mately the center of the proximodorsal surface of metatarsal II (1);present, developed on lateral surface of metatarsal II, at contactwith metatarsal III or on lateral edge of metatarsal III (2).(ORDERED)

233. Metatarsal II, distal plantar surface, fossa for metatarsal I (fossametatarsi I; Baumel and Witmer, 1993): absent (0); shallow notch(1); conspicuous ovoid fossa (2). (ORDERED)

234. Relative position of metatarsal trochleae: trochlea III more distalthan trochleae II and IV (0); trochlea III at same level as trochleaIV (1); trochlea III at same level as trochleae II and IV (2).

235. Metatarsal II, distal extent of metatarsal II relative to metatarsalIV: approximately equal in distal extent (0); metatarsal IIshorter than metatarsal IV but reaching distally farther thanbase of metatarsal IV trochlea (1); metatarsal II shorter than meta-tarsal IV, reaching distally only as far as base of metatarsal IVtrochlea (2).

236. Trochlea of metatarsal II broader than the trochlea of metatarsalIII: absent (0); present (1).

237. Metatarsal III, trochlea in plantar view, proximal extent of lateraland medial edges of trochlea: trochlear edges approximately equalin proximal extent (0); medial edge extends farther (1).

238. Distal end of metatarsal II strongly curved medially: absent (0);present (1).

239. Completely reversed hallux (arch of ungual phalanx of digit I oppos-ing the arch of the unguals of digits II-IV): absent (0); present (1).

240. Size of claw of hallux relative to other pedal claws: shorter, weaker,and smaller (0); similar in size (1); longer, more robust, andlarger (2).

Integument

241. Alula: absent (0); present (1).242. Fan-shaped feathered tail composed of more than two elongate

retrices: absent (0); present (1).

202 JOURNAL OF VERTEBRATE PALEONTOLOGY, VOL. 29, NO. 1, 2009

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3.

Matrix

of28taxausedforphylogen

eticanalysis.

10

20

30

40

50

60

70

80

90

100

110

120

Dromaeosauridae

0000000000

0000000000

0000000000

00000000??

0000000000

0000000000

0000000000

00001????1

0000000000

000?100000

00000000?[01]

??00000000

Archaeopteryx

0000000000

00000?0010

010?00?000

??0?000???

0000000?10

00?100000?

?00000?000

20001????0

0000000000

000?0000?0

?000000???

?????????0

Zhongornis

???2???1??

??????????

?????0????

????1?????

??????????

??????001?

?0??[01]????1

30?1??????

01????0000

0???000???

?00?0?[01]???

??????????

Jeholornis

??22?111??

??????????

0?????????

????00????

?000?00?1?

?0????001?

1000?????0

10000?????

01101?0000

01??010???

??10000??0

??????????

Sapeornis

10100010[01]?

0??????001

0?1?0?????

????1?0???

?00??0??1?

???100[01]00?

?10010?002

4000000?00

0000110000

00??000000

??10002???

??????????

Confuciusornis

1022?1111?

0?????0001

0110000120

???11?1121

010?1100?1

01?101[01]011

1200100002

4000?00001

0100?0?000

0???000000

0000000[12]01

1?01121000

Changchengornis

1?22?1111?

0????????1

??????0???

????1?11??

0?0??100??

?[12]????????

?2??1???02

4??0?0000?

0100?0?000

????000000

?0?00001?1

??01??10?0

Longipteryx

?1201111??

????????11

?11??0????

????000???

?00??01?1?

?1011?????

????[123]????2

4??0201?11

0111110100

????000?00

0?11112[123]?2

11????20??

Eoenantiornis

[01]02001?0[01]?

0?????????

????1?????

????00????

?0??????1?

??????????

????0????2

40202?1??1

0111110101

111000??00

???1112[123]?[12]

??110?2000

Concornis

??????????

??????????

??????????

??????????

??????????

??1????01?

?2????????

?0?01????0

?111110101

?11?00?1??

???1112312

11110?20?0

Longirostravis

[01]0201??1??

??????????

??????????

????00????

?00??01?1?

?1?????0??

???01????2

40?0?01?10

01111?0?00

?20?0001?0

??111?[23][123]?2

21110?20??

Eoalulavis

??????????

??????????

??????????

??????????

??????????

?00111200?

?2?0??????

?????????0

1111110101

1110000000

0?111?3210

??010?30?0

Gobipteryx

20[12]2?10120

0021?10???

?????0???0

?1??1?10??

?10?1?10??

????1?????

?????00??2

40????000?

?1111?010?

11100??000

0?1?112???

?????????0

Neuquenornis

??????????

??????????

??????????

??????????

??????????

???????0??

?1????????

??????????

?1111???01

1111000???

?1?111130[12]

?1????????

Vescornis

?0?????0??

??????????

??????????

????000???

?00[12]001?1?

?21?1??0??

?1??0????2

??????000?

0111?10?01

????000000

?001103312

0011??20??

Iberomesornis

??????????

??????????

??????????

??????????

??????????

10111110??

?0000????2

401?101??0

1111??0?00

?2??0?????

???11?[23][23]??

??????20??

Shanweiniao

[01]?[12][01]1??1??

??????????

??????????

??????0???

?00[12]?01???

???1??????

?????????2

????????1?

0111????000

???000?00?

?111?2[123]?2

111[01]??20??

DNHM

D2522

[01]0201??1??

???????01?

??????????

????0?0???

0?0??0??1?

???????01?

?11?0???0[12]

4??0?0??10

011?1?0?00

?[12]??0???00

???11?3[12]12

2111??20??

Yixianornis

11210?????

??????????

????0???1?

1???0?0???

110?????1?

?1?1??2011

?1003??0?2

4????1000[12]

0111110010

010?110000

001210?311

111?0?41??

Patagopteryx

??????????

?????????1

1110001111

??????????

??0??000?1

1211011001

100031101?

?120??????

?111110000

0?0?01100?

0??????[12]??

??10?????1

PKUP1069

11[12]001?0??

???????1??

??????????

?????00???

101??0????

?11?11?0??

?20???????

??????????

?1111100?0

????11100?

?01210?301

20110?10?1

Apsaravis

??????????

??????????

????????1?

????1?1???

?1????????

021?1?201?

?20?4??0?2

4?10??????

?111110000

1111111001

001????30?

???1?????1

Hongshanornis

?0200?10??

????????1?

??????????

?????00???

101??0????

??????????

?1???????2

4???????01

0111110010

????011??0

?0121?1??2

201???10?1

Yanornis

10[12]10110??

1????????1

??????????

???1000???

1?00?01?1?

?0?????01?

?2003??0??

??????????

0111111010

0?0?110000

??121?0301

211[12]??41?1

Gansus

??????????

??????????

??????????

??????????

??????????

121?1?2011

1100400102

4?20210000

1111110010

020?1100??

0012100312

10100?10?1

Hesperornis

1122?11021

1021011111

1111010111

?1?10110??

100?10101?

1210012111

12004010?2

3020210001

?110?0?010

010?0100??

000200?1?0

??1111000?

Icthyornis

21[12]????0??

???????111

111??1111?

??01001???

?002101111

1[01]11012011

120?[34]?0102

401021000?

?111111010

010?111010

0012?00310

??1?12?011

Anas

2122?01121

0111111111

1111111121

12111?1021

00001011?1

0211012111

1000601202

4020210002

1111111010

020?110000

0012100311

1001133011

Gallus

1122?11121

1121111111

1111111121

12111?1020

00001011?1

0211012111

1001601202

4020210002

1111111010

020?111000

0012101311

0101122011

(Continued

)

O’CONNOR ET AL.—SPECIALIZED CLADE OF CRETACEOUS ENANTIORNITHINE BIRDS 203

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(Continued).

130

140

150

160

170

180

190

200

210

220

230

240

Dromaeosauridae

0000001000

0000000000

0100000000

??000?0000

0000000000

000000000[01]

00001?0000

000010000[01]

0000000000

0000000000

0000000000

0[01]00000000

00

Archaeopteryx

00?0001100

000000000?

??00000000

??000?0000

1000000000

0000020000

00001?1?00

01?010000?

1000000?00

0?0??0??00

0000000000

00?0?0?001

00

Zhongornis

?0000?0100

????0000??

??00??????

????0000?0

100?000000

000001?00?

?????????1

?1????????

??[02]0[01]??00?

0?0??0??1?

00?0?00000

0??0[12]0?011

??

Jeholornis

00??000100

?0?00??000

01110?0000

01210?00?0

0010000000

0000130000

?00?1?11?1

01?010010?

??0???0?00

0?0?10??11

00000000??

00?020?011

?0

Sapeornis

00??000110

0000???000

0111????00

??21000001

000?000000

0001230000

??0???1111

01111?0100

10?0100?10

0?0?111?11

0000000000

00?000?011

??

Confuciusornis

0000000210

?000001010

0001002100

01210?000?

100?000000

0110020000

00001??101

0111100101

0110101?1?

010000?111

000010001?

2100000011

00

Changchengornis

?0????02??

??????????

??01?????0

????0?0000

?0??000000

011002???0

??????????

???[12]???1??

?????????0

????????11

0000?0?0??

2??010?011

?0

Longipteryx

01?00?000?

????0??11?

??11????10

0?01000000

100?011001

0001130000

????1?1111

011[12]11010?

0????0??00

????1?1?10

0?10000000

01?120?011

??

Eoenantiornis

????1?000?

??????????

??11?????1

0?31??0000

?00?011001

000122???0

??????????

???[12]??0[12]0?

??1?????1?

?????????1

0010010???

???0?1001?

??

Concornis

01101?0002

11?0????1?

??11112???

?????????0

??0??12001

000122????

????????10

?11[12]??01?1

????????11

0???0???11

00?0?00??0

0??000?012

??

Longirostravis

01??1?000?

???????0??

??10??????

??310?10?0

1?0?01?001

1?0123??01

??????1??1

011?11????

0???????10

0?????1?11

0?10000??0

???010?0??

??

Eoalulavis

0110100002

1101100111

01111?21?1

?????????0

??1?011001

????2???0?

??????1???

??????????

?11???????

??????????

??????????

??????????

1?

Gobipteryx

??????0?0?

???0??????

???1???111

?????????0

??0?01?00?

?????20???

??????????

????100?1?

?????????1

0101011?11

0010?10000

11?0?1?1??

??

Neuquenornis

????10010?

?1?01?1???

??10?1??11

??31??10?0

?[01]0001????

??????????

??????????

??????????

?110??1???

0?????????

0??0?1??1?

1?00?11?1[12]

??

Vescornis

01?0??0102

11?0???111

1111??????

1[02]?1??10?0

??01012001

0001220???

??????????

?1????????

??????1?01

0????????1

0??0010??0

1??121?111

??

Iberomesornis

??????????

?1?0???111

???1??????

??????????

??????????

???????000

?????????1

?111??????

???0????0?

0????????0

0?10010?00

1??001?011

??

Shanweiniao

???????00?

???????1??

??11????1?

??????????

??????1001

1??122????

??????????

????1??[12]?0

1??0[01]0??1?

????????11

0??00000??

?1??10?001

?1

DNHM

D2522

01????0001

???????11?

??10??????

??????00?0

??0?012001

1??1230000

??0???1?11

?1?110????

0???????0?

???011??1?

0?1000???0

00?010?011

??

Yixianornis

10??11??0?

0?0?11001?

0?100021?0

??31110111

00001?1101

000102100?

1??0??0?01

??11??01??

?12?101?10

????????11

101??001?1

0?001??011

?1

Patagopteryx

001???1000

?0?0000010

0?0000?0?0

?????????0

??1????0?0

0???20?000

10001?0011

10121?021?

0?20????10

0?0?001111

1010100111

0000?0?001

??

PKUP1069

10?01?1101

2011100010

001100???0

??31110??0

0010100100

000101????

???11?1??1

???[12]??0???

????2?1?10

12[01]121?111

1011100??1

010010?011

??

Apsaravis

1001000101

1100001111

1111012110

1?31100111

0110???1??

??????1000

1011??1?11

1012??1211

01?110??1?

?20121??11

1?111001?1

?20010?0??

??

Hongshanornis

10?????10?

???????0??

??11??????

??31??00?0

??00?01101

000101????

????????0?

?01[12]???[12]1?

?????????0

????????11

10?0?00?0?

0??020?011

??

Yanornis

1001??0101

10?????010

0011?0?11?

0?31110010

0000101101

0001231010

0?111??101

00?11?010?

?1??????1?

??0??0??11

1011?00[01]??

12?010?011

??

Gansus

1001??0101

30?1???010

011100111?

0?31??0111

0001?12101

0001321?00

11111?0101

0112100110

01?1101?10

12?0?0?211

1011100101

02?0200011

??

Hesperornis

?????0??0?

?0????????

??????????

??????????

??????????

?????01000

11111?0111

10121012?1

0121101110

1211101211

1011221101

3211200001

??

Icthyornis

1001100101

20110?1010

0011002110

1?31110111

010010?111

1????310?0

10111???11

01121?12?1

0121101?10

121110?211

1011201?01

?2102000??

??

Anas

1001111000

3011111010

0001001110

1231101311

1111102101

1??1231101

11111?0101

1112101211

0111101110

1220101211

1011201301

3210200010

11

Gallus

1001111000

3011111110

0011001110

1131101311

0210112101

1??1211101

12111?0110

1112101211

0121101110

1220101211

1011201301

3220101010

11

204 JOURNAL OF VERTEBRATE PALEONTOLOGY, VOL. 29, NO. 1, 2009

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