Page 1

Cranial morphology of the avian alvarezsauridae: evidence from a new relative of Mononykus

Luis M. Chiappe1, Mark A. Norell2, and James M. Clark3

1

Department of Ornithology, American Museum of Natural History, Central Park West at 79th Street, New York, NY 10024, U.S.A.

2

Department of Vertebrate Paleontology, American Museum of Natural History, Central Park West at 79th Street, New York, NY 10024, U.S.A. 3

Department of Biological Sciences, George Washington University, Washington, D. C. 20052, U.S.A.


Joint American Museum of Natural History and Mongolian Academy of Sciences Expeditions have recovered over 20 alvarezsaurid (Theropoda: Aves) specimens in the Late Cretaceous of Mongolia’s Gobi Desert1. Here we describe a new taxon closely related to Mononykus2,3. This material includes two exquisitely preserved skulls—the first known for Alvarezsauridae—which provide additional support for the group’s avian relationships4,5, first postulated on primarily postcranial evidence2,3. This evidence includes the presence of avian characters such as the absence of a contact between the jugal and postorbital, and between the quadratojugal and squamosal, a movable joint between quadratojugal and quadrate, separate squamosal and braincase articulations of the quadrate, confluence between the caudal tympanic recess and columellar recess, a triradiate palatine, an unusually large foramen magnum, and the loss of a coronoid bone. The configuration of the temporal region of the skull and its articulation with the rostrum strongly suggest the capability for prokinetic movement, and support the idea that prokinesis preceded other types of avian intracranial kinesis. Aves (Avialae sensu Gauthier, 1986) Linnaeus, 1758 Metornithes Perle et al., 1993 Alvarezsauridae Bonaparte, 1991 Mononykinae, new taxon (Fig. 4) Shuvuuia deserti, new genus and species. Holotype—MGI 100/975 (Mongolian Geological Institute, Ulaanbaatar). Referred specimens—MGI N 100/99, MGI 100/977, MGI 100/1001. Previously these specimens, including the holotype, were referred to Mononykus4. Etymology—Shuvuuia from the Mongolian "shuvuu" meaning bird and deserti in reference to the semi-arid depositional environment of the Djadokhta Formation1. Locality and Horizon—Ukhaa Tolgod (MGI 100/975, MGI 100/977, MGI 100/1001) and Tugrugeen Shireh (MGI 100/99), South Gobi Aimak, Mongolia. Tentatively Djadokhta Formation (Late Cretaceous/Campanian?)1,6. Diagnosis—A mononykine (Fig. 4) distinguished from Mononykus olecranus by its less compressed cervical centra with large pneumatic foramina, humeral deltopectoral crest continuous with its head, pubis of subcircular section, femoral and tibiotarsal shafts bowed latero-medially, and medial margin of astragalus' ascending process less excavated. Shuvuuia deserti shows a lesser degree of co-ossification of the proximal tarsals to the tibia and among metacarpals in specimens of comparable size to the holotype of Mononykus olecranus, suggesting a lower rate of bone co-ossification. The new species differs from Parvicursor remotus by the absence of a ventral keel in the rostralmost synsacral vertebra and by the lesser co-ossification between proximal tarsals and the tibia. Shuvuuia deserti differs from all alvarezsaurids by the presence of a sharp ridge on the medial margin of the distal tibiotarsus, a character interpreted as an autapomorphy. The skull of Shuvuuia deserti displays a number of characters interpreted as autapomorphies, including the articulation between quadrate and postorbital, elongate basipterygoid processes, numerous teeth, hypertrofied prefrontal/ectethmoid (see below for problematic interpretation of this bone). These characters, however, may prove to diagnose a more inclusive taxon following the discovery of additional alvarezsaurid cranial material. Description. The delicate skull is elongate with large orbits and terminal tear-shaped nares (Figs. 1-3). The maxilla forms most of the snout’s lateral surface as in other early birds10. The caudal half forms a slender bar ventrally bordering the antorbital fossa. The dentigerous margin of the premaxilla is not preserved but the maxilla bears numerous tiny, unserrated teeth, identical to Mononykus2. Teeth are absent behind the rostral third of the antorbital fossa. On the dentary the teeth

2


lay in a continuous groove. The lacrimal has an expanded rostral process and a tiny caudal extension resembling the L-shaped lacrimal of Archaeopteryx and other non-avian theropods11. The orbit is walled rostrally by a problematic large ossification, widely exposed on the skull roof. It could be interpreted as a large prefrontal, but both elements meet ventral to the frontals—a condition unknown in dinosaurs12. In this respect, this element resembles more an avian ectethmoid; yet no ectethmoid is known to be exposed dorsally13. The postorbital fails to reach the rod-like jugal so the orbit and infratemporal fossa are continuous; a condition known only for metornithine birds among archosaurs14,15—although this condition may be present in Archaeopteryx4. The jugal and quadratojugal are fused into a jugal bar which forms a tiny fork on its caudal end. Shuvuuia also contrasts with non-avian archosaurs, in which the quadratojugal bears a tall dorsal process sutured to the quadrate14,15. In Archaeopteryx16 and an enantiornithine hatchling17 this process is significantly shorter and not sutured to the quadrate. The triradiate squamosal is not incorporated into the braincase of Shuvuuia, Archaeopteryx, and other early avians, which retain a complete, diapsid supratemporal fenestra16,17. Like in other birds, the paroccipital processes are short and not perforated by the caudal tympanic recess, which opens inside the collumelar recess4. The foramen magnum is proportionally larger than in any non-avian dinosaur12 and the caudally directed occipital condyle is very small. The basipterygoid processes are unusually long and almost vertically oriented. The quadrate is tall and slender, resembling Archaeopteryx and the enantiornithine Gobipteryx in that it is nearly one-fourth the length of the skull16. This bone also resembles Archaeopteryx in the strong rostro-caudal compression of its latero-distal corner 16. Proximally, the quadrate has two well-differentiated heads. The lateral articulates with a squamosal-postorbital facet, while the medial is dorso-caudally directed toward the braincase. The palatine is long and slender, lacking the jugal process and tetraradiate aspect of non-avian theropods16. Discussion. The skull of Shuuvuia offers further evidence for the avian affinities of this group and emphasizes the highly specialized nature of this bizarre lineage; just as in the postcranium, Shuuvuia displays a number of unusual cranial characters, and characters restricted to Aves among dinosaurs12. The configuration of the jugal and suspensorium of Shuvuuia (Fig. 1) suggests capacity for intracranial kinesis 15,18-20(e.g. the elevation and depression of the rostrum). Without ventral squamosal and dorsal quadratojugal processes, the streptostylic quadrate was free to swing antero-posteriorly15,18-20. The lack of a connection between the jugal and postorbital freed the jugal to act as a strut between quadrate and rostrum. Forces directed longitudinally from the quadrate would rotate the rostrum around a transverse axis at a flexion area just anterior to the orbit. A thinning of the jugal (bending zone) just caudal to its lacrimal contact and the loose connection between the frontals and the preorbital bones (nasals and prefrontals/ectethmoids) indicate that the snout may have moved as a unit like in prokinetic birds15,18-20 (Fig. 1C). The absence of a continuous naso-orbital septum agrees with this interpretation. Prokinesis is usually regarded as the primitive type of kinesis derived from either akinetic or mesokinetic archosaurian skulls15,18-20 and has been reported in a number of early birds21-23. The design of the skull of Shuvuuia suggests that some motion, most likely prokinetic, was possible, thus supporting this interpretation. Methodology. A cladistic analysis based on 90 characters (six multistate) places the Alvarezsauridae as the sister-taxon to all avians except for Archaeopteryx (Fig. 4; see Supplementary Information for character list, data matrix, and node diagnoses). Cranial characters in Shuvuuia shared only with birds among dinosaurs include the absence of a postorbitaljugal contact, the movable joint (not sutured) between quadratojugal and quadrate, the separate articulation of the quadrate with the braincase, and the disproportionately large foramen magnum relative to the occipital condyle. The skull of Shuvuuia also shares with Archaeopteryx and other avians characters that are absent in velociraptorine theropods—the outgroup selected for the present cladistic analysis. These include the absence of squamosal-quadratojugal contact, a

3


triradiate palatine, a caudal tympanic recess confluent with the columellar recess, the absence of a coronoid in the mandible, and unserrated tooth crowns. Certain workers have claimed that alvarezsaurids are either specialized ornithomimosaurs24,25 or a different group of non-maniraptoran theropods26, although in neither case a cladistic analysis has been published. Our phylogenetic studies, as well as independent cladistic analyses, indicate that the few similarities between alvarezsaurids and nonmaniraptoran coelurosaurs are convergent4,5,7,8,27. For example, the ornithomimosaur Pelecanimimus bears numerous, tiny teeth with unserrated crowns restricted to the anterior part of the maxilla28 and ornithomimosaurs (as well as oviraptorosaurs and therizinosaurids among non-avian maniraptorans) lack a coronoid bone29. Furthermore, if the preorbital ossification of Shuvuuia is identified as a prefrontal, it is larger than that of most maniraptoran dinosaurs and more comparable in size to that of ornithomimosaurs30. However, placing alvarezsaurids outside Maniraptora would require homoplasy in an extensive number of maniraptoran, avian, and metornithine synapomorphies4,5,7,8,27. References 1. Dashzeveg D. et al. Extraordinary preservation in a new vertebrate assemblage from the Late Cretaceous of Mongolia. Nature 374: 446-449 (1995). 2. Perle A., Norell, M. A., Chiappe, L. M. & Clark, J. M. Flightless bird from the Cretaceous of Mongolia. Nature 362, 623626 (1993). 3. Perle A. et al. Skeletal morphology of Mononykus olecranus (Theropoda: Avialae) from the Late Cretaceous of Mongolia. Am. Mus. Nov. 3105, 1-29 (1994). 4. Chiappe, L. M., Norell, M. A. & Clark, J. M. Phylogenetic position of Mononykus from the Upper Cretaceous of the Gobi Desert. Mem. Queens. Mus. 39, 557-582 (1996). 5. Chiappe, L. M., Norell, M. A. & Clark, J. M. Mononykus and Birds: Methods and Evidence. Auk 114, 300-302 (1997). 6. Jerzykiewicz, T. & Russell, D. A. Late Mesozoic stratigraphy and vertebrates from the Gobi Basin. Cret. Res. 12, 345377 (1991). 7. Novas, F. E. Alvarezsauridae, Cretaceous maniraptorans from Patagonia and Mongolia. Mem. Queens. Mus. 39, 675702 (1996). 8. Novas, F. E. Anatomy of Patagonykus puertai (Theropoda, Maniraptora, Alvarezsauridae) from the Late Cretaceous of Patagonia. J. Vert. Paleont. 17, 137-166 (1997). 9. Karkhu, A. A. & Rautian, A. S. A new family of Maniraptora (Dinosauria: Saurischia) from the Late Cretaceous of Mongolia. Paleont. J. 30, 583-592 (1996). 10. Chiappe, L. M. Late Cretaceous birds of southern South America: anatomy and systematics of Enantiornithes and Patagopteryx deferrariisi. M眉nchener Geowiss. Ab.. (A) 30, 203-244 (1996). 11. Currie, P. J. New information on the anatomy and relationships of Dromaeosaurus albertensis (Dinosauria, Theropoda). J. Vert. Paleont. 15, 576-591 (1995). 12. Weishampel, D. B., Dodson, P. & Osm贸lska, H. The Dinosauria. (Univ. of California Press, Berkeley, 1990). 13. Cracraft, J. The lacrimal-ectethmoid bone complex in birds: a single character analysis. Am. Midl. Nat. 80, 316-359 (1968). 14. Romer, A. S. Osteology of the Reptiles (Univ. Chicago Press, Chicago, 1956). 15. Zusi, R. L. in The Skull (eds Hanken, J & Hall, B. K.) vol. 2, 391-437 (Univ. Chicago Press, Chicago, 1993). 16. Elzanowski, A. & Wellnhofer, P. (1996). Cranial morphology of Archaeopteryx: evidence from the seventh skeleton. J. Vert. Paleont. 16, 81-94 (1996). 17. Sanz, J. L. et al. A nestling bird from the Early Cretaceous of Spain: implications for avian skull and neck evolution. Science 276, 1543-1546 (1997). 4


18. Zusi, R. L. A functional and evolutionary analysis of rhynchokinesis in birds. Smith. Contr. Zool. 395, 1-40 (1985). 19. Simonetta, A. M. On the mechanical implications of the avian skull and their bearing on the evolution and classification of birds. Quart. Rev. Biol. 35, 206-220 (1960). 20. Bock, W. J. Kinetics of the avian skull. J. Morph. 114, 1-42 (1964). 21. Bühler, P. On the morphology of the skull of Archaeopteryx. in The beginnings of Birds (eds Hecht, M. K., Ostrom, J. H., Viohl, G. & Wellnhofer, P.) 135-140 (Proceedings of the International Archaeopteryx Conference, Eichstätt, 1985). 22. Hou, L., Martin, L. D., Zhou, Z. & Feduccia, A. Early adaptive radiation of birds: evidence from fossils from northeastern China. Science 274, 1164-1167 (1996). 23. Bühler, P., Martin, L. D. & Witmer, L. M. Cranial kinesis in the Late Cretaceous birds Hesperornis and Parahesperornis. Auk 105, 111-122 (1988). 24. Martin, L.D. & Rinaldi, C. How to Tell a Bird from a Dinosaur. Maps Digest, 17, 190-196 (1994) 25. Feduccia, A. The origin and evolution of birds (Yale Univ. Press, New Haven, 1996). 26. Sereno, P. The origin and evolution of dinosaurs. Annu. Rev. Earth Planet. Sci. 25, 435-489 (1997). 27. Forster, C. A., Chiappe, L. M., Krause, D. W. & Sampson, S. D. The first Cretaceous bird from Madagascar. Nature 382, 532-534 (1996). 28. Pérez-Moreno, B. P. et al. A unique multitoothed ornithomimosaur from the Lower Cretaceous of Spain. Nature 370, 363-367 (1994). 29. Clark, J. M., Perle, A. & Norell, M. A. The skull of Erlicosaurus andrewsi, a Late Cretaceous “Segnosaur” (Theropoda: Therizinosauridae) from Mongolia. Am. Mus. Nov. 3115, 1-39 (1994). 30. Osmólska, H., Roniewicz, E. & Barsbold, R. A new dinosaur, Gallimimus bullatus n. gen. n. sp. (Ornithomimidae) from the Upper Cretaceous of Mongolia. Palaeont. Pol. 27, 103-143 (1972). Acknowledgements. We thank A. Davidson and M. Ellison for the preparation and illustration of the specimens, respectively. A. Milner, L. Witmer, G. Zweers, and J. Vanden Berge provided useful reviews and discussions. The Chapman and Frick Memorial Funds of the AMNH, and the National Science Foundation (DEB-9407999) provided support for this research. Figure captions Figure 1. A, B, Skull and jaw of Shuvuuia deserti (MGI 100/1001) in right lateral (A) and left lateral (B; only postorbital region and with left jaw removed) views. C, Reconstruction of the skull of Shuvuuia deserti displaying its kinematic capacity for elevating the snout independent from the braincase. Placement of flexion areas or bending zones at the base of the snout, both dorsally and ventrally, suggest that the snout moved as a single unit, like in all prokinetic birds. Note that Shuvuuia’s prokinetic movement differs from the modern type of prokinesis in that the dorsal bending zone lies between the frontals and the nasal-preorbital bones, and not between the frontals and the nasal-premaxillaries. Abbreviations: art, articular; atf, antorbital fossa; d, dentary; fr, frontal; jbr, jugal bar; lcr, lacrimal; mdf, mandibular fossa; mx, maxilla; po, postorbital; q, quadrate; sq, squamosal. Figure 2. Skull and right jaw of Shuvuuia deserti (MGI 100/1001) in dorsal (A), ventral (B), and caudal (C) views. Abbreviations: bpt, basipterygoid process; bsr, basisphenoidal recess; fm, foramen magnum; hyo, hyoid; occ, occipital condyle; p, parietal; poo, preorbital ossification (prefrontal/ectethmoid; see text); pop, paroccipital process; pt, pterygoid; stf, supratemporal fenestra; others as in Fig. 1.

5


Figure 3. Skull and jaws of Shuvuuia deserti (MGI 100/977) in dorsal (A) and ventral (B) views. Abbreviations: art, articular; mxf, maxillary fenestra; n, nasal; pal, palatine; pmx, premaxilla; psr, parasphenoidal rostrum; san, surangular; slr, sclerotic ring; others as in Fig. 2. Figure 4. A, Some morphological differences between Shuvuuia deserti (left row) and Mononykus olecranus (right row) (figures not in scale). 1, Shuvuuia has a cranio-dorsally expanded deltopectoral crest that is continuous with the humeral head while Mononykus exhibits a pillar-like deltopectoral crest (see arrow). 2, Shuvuuia possesses a sharp ridge (larger arrow) on the medial margin of the distal end of the tibia which is absent in Mononykus and lacks the deep medial notch (smaller arrow) at the base of the ascending process of Mononykus. 3-4, The centra of Shuvuuia’s cervico-dorsal (3) and anterior dorsals (4) are much less compressed than those in Mononykus. For autapomorphic characters and further differences see Diagnosis in text. B, Phylogenetic position of the Alvarezsauridae and interrelationships among its component taxa. Consensus cladogram derived from three most parsimonious trees with different topologies for the mononykine taxa under the implicit enumeration command (finds all shortest trees) of computer program “Hennig 86” (length: 115 steps, CI: 0.83, RI: 0.82 for both the consensus and the fundamental cladograms). Mononykinae is phylogenetically defined as the common ancestor of Mononykus, Shuvuuia, and Parvicursor plus all its descendants. Supplementary Information to be made available on Nature’s Web site Cladistic Analysis. List of characters and data matrix informative for resolving the phylogenetic relationships of the taxa included in Figure 4 (multistate characters treated as non-additive). Scoring for Enantiornithes is based on a combination of the anatomical information provided by the indisputable enantiornithines Neuquenornis volans (Chiappe & Calvo, 1994), Cathayornis yandica (Zhou et al., 1992; Martin & Zhou, 1997), Eoalulavis hoyasi (Sanz et al., 1996), Concornis lacustris (Sanz et al., 1995), Gobipteryx minuta (Elzanowski, 1977, 1981; including undescribed material), the El Brete enantiornithines (Chiappe, 1993, 1996), and a hatchling specimen from the Early Cretaceous of Catalonia (Sanz et al., 1997). The scoring for Ornithurae is based on the anatomy of the basal ornithurines Hesperornis regalis (Marsh, 1880), Ichthyornis dispar (Marsh, 1880), Ichthyornis victor (Marsh, 1880), and Ambiortus dementjevi (Kurochkin, 1985). For the interrelationships within Enantiornithes see Chiappe (1993) and Sanz et al. (1995); basal ornithurine relationships are discussed in Cracraft (1986).

1.

Rostral portion of premaxillae unfused (0) or fused (1) in adults.

2.

Frontal process of premaxilla short (0), relatively long to very long, at least approaching the rostral border of the antorbital fossa (1).

3.

Cup-shaped caudal maxillary sinus: absent (0), present (1).

4.

Caudal margin of naris farther rostral than (0) or, nearly reaching or overlapping (1) the, rostral border of the antorbital fossa.

5.

Triradiate palatine (jugal process absent): absent (0), present (1).

6.

Postorbital-jugal contact: present (0), absent (1).

7.

Quadratojugal sutured to the quadrate (0), or joined by a ligament (1).

8.

Quadratojugal-squamosal contact: present (0), absent (1).

9.

Quadrate articulating only with the squamosal (0), or with both prootic and squamosal (1).

10. Caudal tympanic recess opens on the rostral margin of the paraoccipital process (0), or into the columellar recess (1). 11. Coronoid bone: present (0), absent (1). 12. Teeth in adults: with serrated crown (0) or unserrated crowns (1). 13. One or more pneumatic foramina piercing the centra of mid-anterior cervicals beyond the level of the parapophysis6


diapophysis: present (0), absent (1). 14. Anterior cervical vertebrae heterocoelous: absent (0), present (1). 15. Carotid processes in intermediate cervicals: absent (0), present (1). 16. Prominent ventral processes on cervico-dorsal vertebrae: absent (0), present (1). 17. Cervico-dorsal vertebrae with parapophyses located at the same level as the prezygapophyses: absent (0), present (1). 18. Wide vertebral foramen in thoracic vertebrae, vertebral foramen/articular cranial facies ratio (vertical diameter) larger than 0.40: absent (0), present (1). 19. Hyposphene-hypantrum accessory intervertebral articulations in dorsal vertebrae: present (0), absent (1). 20. Synsacrum formed by 7 or fewer (0), or 8 or more vertebrae (1). 21. Cranial articular surface of synsacrum strongly concave: absent (0), present (1). 22. Caudal portion of the synsacrum forming a prominent ventral keel: absent (0), present (1). 23. Caudal articular surface of synsacrum convex: absent (0), present (1). 24. Prezygapophyses of distal caudal vertebrae: elongate (0), short or absent (1). 25. Caudal vertebrae: amphicoelous (0), or procoelous (1). 26. First caudal centrum strongly compressed ventrally: absent (0), present (1). 27. Elongated (much longer than wider) proximal haemal arches: absent (0), present (1). 28. Pygostyle: absent (0), present (1). 29. Caudal vertebral count larger than 35 (0) or fewer than 25-26 (1). 30. Coracoid and scapula articulate through a broad, sutured articulation (0), or through more localize, less extensive facets (1). 31.

Scapula articulated at the shoulder (proximal) end of coracoid (0), or well below it (1).

32. Coracoid and scapula placed in the same plane (0), or forming a sharp angle (1) at the level of the glenoid cavity. 33. Coracoid shape: elongated with subrectangular profile (0), short (1), strut-like (2). 34. Bicipital tubercle (= acrocoracoidal process): present (0), absent (1). 35. Supracoracoid nerve foramen of coracoid centrally located (0), or displaced (often as an incision or even without passing through) toward the medial margin of coracoid (1). 36. Scapular caudal end blunt and usually expanded (0), or tapered to sharp point (1). 37. Prominent acromion in the scapula: absent (0), present (1). 38. Boomerang-shaped furcula, with interclavicular angle approximately 90/ (0), or U-shaped furcula, with an interclavicular angle less than 70/ (1). 39. Sternum subquadrangular to transversally rectangular (0) or longitudinally rectangular (1). 40. Ossified sternal keel: absent (0), present (1). 41. Proximal and distal humeral ends twisted (0), or expanded nearly in the same plane (1). 42. Ventral tubercle of humerus projected ventrally (0), proximally (1), or caudally, separated from the humeral head by a deep capital incision (2). 43. Humerus with distinct transverse ligamental groove: absent (0), present (1). 44. Humeral pneumatic fossa: absent (0), present (1). 45. Humeral distal condyles mainly located on distal (0), or cranial (1) aspect. 46. Humerus with two (0), or a single distal condyle (1). 47. Well-developed olecranal fossa on the caudal face of the distal end of humerus: absent (0), present (1). 48. Ulna shorter than (0), or subequal in length to, or longer than, humerus (1). 49. Diameter of ulnar shaft: radial shaft/ulnar shaft ratio larger (0), or smaller (1) than 0.70. 50. Olecranon process on ulna: relatively small (0), hypertrophied, nearly one-third (1) or one-half (2) the length of the ulna. 7


51. Distal end of ulna subrectangular and transversely compressed (0), or subtriangular in shape (1). 52. Semilunate ridge on ulnar dorsal condyle: absent (0), present (1). 53. Ulnare (scapholunar) of round to sub-rectangular shape (0) or U-shaped to heart-shaped (1). 54. Distal carpals and proximal portion of metacarpals unfused (0), or fused forming a carpometacarpus (1). 55. Extensor process on carpometacarpus: absent or rudimentary (0), present (1). 56. Alular metacarpal (I)/major metacarpal (II) length ratio smaller than or equivalent to 0.30: absent (0), present (1). 57. Alular metacarpal massive, depressed, and quadrangular-shaped: absent (0), present (1). 58. Alular digit (I) long, exceeding the distal end of the major metacarpal (0), or short, not surpassing this metacarpal (1). 59. Alular digit (I) large, robust, and dorsoventrally compressed: absent (0), present (1). 60. Prominent ventral projection of the latero-proximal margin of the proximal phalanx of alular digit (digit I): absent (0), present (1). 61. Alular ungual phalanx with two, ventro-proximal foramina: absent (0), present (1). 62. Pelvic elements unfused (0), or fused or partially fused (1). 63. Pubis subvertically oriented (0), or well-retroverted (1). 64. Prominent antitrochanter: absent (0), caudally directed (1), or dorso-caudally directed (2). 65. Iliac fossa for M. cuppedicus (=M. iliofemoralis internus): present (0), absent or rudimentary (1). 66. Iliac brevis fossa: present (0), absent (1). 67. Pubic pedicel ventrally or caudoventrally (0), or cranioventrally projected (1). 68. Supracetabular crest on ilium absent or rudimentary (0), extending throughout the acetabulum (1), or extending only over the rostral half of the acetabulum (2). 69. Ischiadic terminal processes in contact (0), or lacking contact (1). 70. Ischium less than two-thirds (0), or two-thirds or more of pubis length (1). 71. Obturator process of ischium: prominent (0), or reduced or absent (1). 72. Pubic apex in contact (0), or lacking contact (1). 73. Pubis shaft laterally compressed throughout its length: absent (0), present (1). 74. Pubic foot: present (0), absent (1). 75. Pubic apron more than one-third the length of the pubis (0), shorter or absent (1). 76. Laterally compressed and kidney-shaped proximal end of pubis: absent (0), present (1). 77. Femur with distinct fossa for capital ligament: absent (0), present (1). 78. Femoral anterior trochanter nearly confluent with the greater trochanter (0), or fused to it forming the trochanteric crest (1). 79. Femoral posterior trochanter: present (0), absent (1). 80. Conical and strongly distally projected lateral condyle of femur: absent (0), present (1). 81. Femoral popliteal fossa distally bounded by a complete transverse ridge: absent (0), present (1). 82. Tibiofibular crest on the lateral condyle of femur: absent (0), present (1). 83. Tibia, calcaneum, and astragalus unfused or poorly coosified (sutures still visible) (0), or complete calcaneoastragalar-tibial fusion (1). 84. Medial border of tibiotarsus at nearly the level of lateral border (0) or strongly projected proximally (1). 85. Proximal end of fibula prominently excavated by a medial fossa (0), or nearly flat (1). 86. Fibula with tubercle for M. iliofibularis anterolaterally (0), laterally or caudolaterally or caudally (1) directed. 87. Fibula reaching the proximal tarsals (0), or greatly reduced distally, without reaching these elements (1). 88. Distal tarsals free (0), or completely fused to the metatarsals (1). 89. Metatarsal V: present (0), absent (1). 90. Proximal end of metatarsal III in the same plane as metatarsals II and IV (0), reduced, not reaching the tarsals (arctometatarsalian condition) (1), or plantarily displaced with respect to metatarsals II and IV (2). 8


Data Matrix

Taxa\character 1

2

3

4

5

6

7

8

9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45

Velociraptorinae 0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

Archaeopteryx

0

1

0

1

1

?

1

1

?

1

1

1

0

0

?

0

0

?

?

0

0

?

0

1

0

?

0

0

1

0

0

0

0

0

0

0

1

0

?

?

0

0

0

0

0

Mononykus

?

?

?

?

?

?

?

?

?

1

?

1

1

0

1

1

1

1

1

?

1

1

1

?

1

1

?

?

?

0

0

0

1

1

0

0

0

?

1

1

1

1

0

0

1

Shuvuuia

0

0

?

0

1

1

1

1

1

1

1

1

0

0

1

1

1

1

1

0

1

1

1

1

1

1

1

0

1

0

0

0

1

1

0

0

0

?

1

1

1

1

0

0

1

Parvicursor

?

?

?

?

?

?

?

?

?

?

?

?

?

?

?

?

?

1

1

?

0

?

?

?

1

1

?

0

?

?

?

?

?

?

?

?

?

?

?

?

?

?

?

?

?

Alvarezsaurus

?

?

?

?

?

?

?

?

?

?

?

?

?

?

?

?

0

?

?

0

0

0

?

1

1

1

1

?

?

0

0

0

?

?

0

?

0

?

?

?

?

?

?

?

?

Patagonykus

?

?

?

?

?

?

?

?

?

?

?

?

?

?

?

?

?

1

1

?

1

1

1

?

1

1

?

?

?

0

0

?

1

1

0

?

?

?

?

?

?

1

0

0

1

Enantiornithes

1

1

1

1

1

1

1

1

?

?

1

1

1

1

1

1

0

1

1

1

1

0

0

1

0

0

0

1

1

1

1

1

2

0

1

1

1

1

1

1

0

2

1

1

1

Ornithurae

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

0

1

1

1

0

0

0

1

0

0

0

1

1

1

1

1

2

0

1

1

1

1

1

1

1

2

1

1

1

Taxa\character 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 Velociraptorinae 0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

Archaeopteryx

0

0

0

0

0

0

0

0

0

0

1

0

0

0

0

0

0

0

0

0

?

0

0

?

0

1

0

0

0

0

0

?

0

0

0

?

0

0

0

?

?

0

0

0

0

Mononykus

1

0

0

0

2

1

0

?

1

0

0

1

0

1

1

1

1

?

1

1

?

1

2

?

?

?

?

?

?

?

1

0

1

1

1

0

0

0

1

1

?

1

?

?

1

Shuvuuia

1

0

0

0

2

1

0

?

1

0

0

1

0

1

1

1

?

1

1

1

0

1

2

1

1

1

1

1

1

1

1

?

?

1

?

0

?

0

1

1

1

1

0

0

1

Parvicursor

?

?

?

?

?

?

?

?

?

?

?

?

?

?

?

?

1

?

1

?

?

?

?

1

1

1

1

1

?

1

?

?

1

1

1

?

0

0

1

1

1

1

0

?

1

Alvarezsaurus

?

?

?

?

?

?

?

?

?

?

?

?

?

?

?

0

?

?

?

1

0

1

1

?

?

?

?

?

?

?

?

?

?

0

?

?

?

0

?

?

?

0

?

?

0

Patagonykus

1

0

?

0

1

1

0

?

1

0

?

1

0

1

1

?

0

0

1

1

?

1

1

?

?

?

1

1

0

1

0

?

0

0

1

0

0

0

0

?

?

0

?

?

0

Enantiornithes

0

1

1

1

0

1

1

1

1

1

1

0

1

0

0

0

1

1

2

0

1

0

0

0

1

0

0

0

0

1

0

1

1

0

0

1

1

1

0

1

?

1

1

1

0

Ornithurae

0

1

1

1

0

1

1

1

1

1

1

0

1

0

0

?

1

1

2

1

1

0

0

1

1

1

1

1

1

1

0

1

1

1

0

1

1

1

0

1

1

1

1

1

2

Synapomorphies diagnosing different nodes of Figure 4 (asterisked characters have equivocal optimization; a “-“ preceding the character number indicates a reversal):

Node 1 (Aves): 2*, 4*, 5, 6*, 7, 8, 9*, 10, 11, 12, 15*, 18*, 19*, 24, 29, 37-40*, 56*, 69*, 71, 85*, 86*

Node 2 (Metornithes): 2-4*, 6*, 9*, 13*, 15*, 16, 18*, 19*, 33a*, 33b*, 37-41*, 42a*, 42b*, 45, 51, 53*, 54, 56*, 62*, 63*, 64a*, 64b*, 65*, 69*, 70, 72*, 73*, 75, 78*, 85*, 86*

Node 3 (Alvarezsauridae): 2-4*, 13*, 23*, 25, 26, 27, 33a,*, 33b*, 34*, -37*, 38*, 41*, 42a*, 42b*, 46*, 50a*, 50b*, 53*, 56*, 57*, 59*, 60*, 62*, 63*, 64a*, 64b*, 65*, 67, 68a 69*, 72*, 73*, 78*, 80* Node 4 (Patagonykus + Mononykinae): 2-4*, 13*, 17*, 21, 22, 23*, 33a*, 34*, 38*, 41*, 42a*, 46*, 50a*, 50b*, 53*, 56*, 57*, 59-63*, 64a*, 69*, 72*, 73*, 78*, 80*

Node 5 (Mononykinae): 2-4*, 13*, 17*, 38*, 41*, 50b*, 53*, -56*, 61-63*, 68b, 69*, 74*, 76, 78*, 79, 84, 87, 90

Ornithurae + Enantiornithes: 1, 2-4*, 13*, 14, 20, 28, 30, 31, 32, 33b*, 35, 36, 37*, 38*, 41*, 42b*, 43, 44, 47, 48, 49, 52, 53*, 55, 56*, 58, 62*, 63*, 64b*, 65*, 66, 69*, 72*, 73*, 77, 78*, 81, 82, 83, 87, 88, 89

9


References Chiappe, L. M. Enantiornithine (Aves) tarsometatarsi from the Cretaceous Lecho Formation of northwestern Argentina. Am. Mus. Nov. 3083,1-27 (1993). Chiappe, L. M. Late Cretaceous birds of southern South America: anatomy and systematics of Enantiornithes and Patagopteryx deferrariisi. M端nchener Geowiss. Ab. (A) 30, 203-244 (1996). Chiappe, L. M. & Calvo, J.O. Neuquenornis volans, a new Upper Cretaceous bird (Enantiornithes: Avisauridae) from Patagonia, Argentina. J. Vert. Paleont. 14, 230-246 (1994). Cracraft, J. The origin and early diversification of birds. Paleobiology 12, 383-399 (1986). Elzanowski, A. Skulls of Gobipteryx (Aves) from the Upper Cretaceous of Mongolia. Palaeont. Pol. 37, 153-165 (1977). Elzanowski, A. Embryonic bird skeletons from the Late Cretaceous of Mongolia. Palaeont. Pol. 42, 147-176 (1981). Kurochkin, E. N. A true carinate bird from Lower Cretaceous deposits in Mongolia and other evidence of early Cretaceous birds in Asia. Cret. Res. 6, 271-278 (1985). Marsh, O. C. Odontornithes: a monograph on the extinct toothed birds of North America. US Geol. Explor. 40th Parallel (Government Printing Office, Washington, 1880). Martin, L. D. & Zhou Z. Archaeopteryx-like skull in enantiornithine bird. Nature 389, 556 (1997). Sanz, J. L., Chiappe, L. M., & Buscalioni, A. D. The osteology of Concornis lacustris (Aves: Enantiornithes) from the Lower Cretaceous of Spain and a re-examination of its phylogenetic relationships. Am. Mus. Nov. 3133, 1-23 (1995). Sanz, J. L. et al. A new Lower Cretaceous bird from Spain: implications for the evolution of flight. Nature 382, 442-445 (1996). Sanz, J. L. et al. A nestling bird from the Early Cretaceous of Spain: implications for avian skull and neck evolution. Science 276, 1543-1546 (1997). Zhou, Z., Jin, F. & Zhang, J. Preliminary report on a mesozoic bird from Liaoning, China. Chinese Sci. Bul. 37, 1365-1368 (1992).

10

Chiappe et al, 1998  

Department of Vertebrate Paleontology, American Museum of Natural History, Central Park West at 79 th Street, New York, NY 10024, U.S.A. Dep...

Read more
Read more
Similar to
Popular now
Just for you