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Science 7 September 2007:
Vol. 317. no. 5843, pp. 1378 - 1381
DOI: 10.1126/science.1144066
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Reports

A Basal Dromaeosaurid and Size Evolution Preceding Avian Flight

Alan H. Turner1*, Diego Pol2, Julia A. Clarke3,4,1, Gregory M. Erickson5 and Mark A. Norell1

1 Division of Paleontology, American Museum of Natural History, Central Park West at 79th Street, New York, NY 10024–5192, USA.
2 CONICET, Museo Paleontológico Egidio Feruglio, Avenida Fontana 140, (9100) Trelew, Argentina.
3 Department of Marine, Earth and Atmospheric Sciences, North Carolina State University, Campus Box 8208, Raleigh, NC 27695–8298, USA.
4 Division of Paleontology, North Carolina Museum of Natural Sciences, 11 West Jones Street, Raleigh, NC 27601–1029, USA.
5 Department of Biological Sciences, Florida State University, Dewey Street and Palmetto Drive, Tallahassee, FL 32306–1100, USA.


Figure 1 Fig. 1. Mahakala omnogovae IGM 100/1033, holotype. (A) Skull in occipital view. (B) Braincase in left lateral view. (C) Sacrum and partial right leg in ventral view. (D) Frontal in dorsal (left) and ventral (right) views. (E) Axisvertebrain left lateral view. Scale bars, 5 mm in (A), (B), (D), and E) and 1 cm in (C). Abbreviations are as follows: cav, caudal vertebra; ctr, caudal tympanic recess; dtr, dorsal tympanic recess; ep, epipophysis; f.l, lacrimal facet; f.po, postorbital facet; fm, foramen magnum; mt, metatarsus; oc, occipitalcondyle; od, odontoid; pap, paroccipital process; pf, pneumatic foramen; ph, phalanx; prz, prezygapophysis; q.pr, contactsurface on prootic for quadrate; q, quadrate; ti, tibia; tl, tectal lobe; sac, sacrum; v.o, occipital vein track. [View Larger Version of this Image (40K GIF file)]
 

Figure 2 Fig. 2. Mahakala omnogovae IGM 100/1033, holotype. (A) Rightulna in lateral (right) and medial (left) views. (B) Ilium in medial (top) and lateral (bottom) views. (C) Femurinposterior (left) and lateral (right) views. (D) Tibia in anterior view. (E) Left metatarsus in anterior view. (F) Right raptorial claw. (G) Midcaudal vertebrae. Scale bars, 1 cm in (B) to (E) and 5 mm in (A), (F), and (G). Abbreviations are as follows: aa, ascending process of astragalus; as, astragalus; bf, brevis fossa; brs, brevisshelf; bs, biccipital scar; ca, calcaneum; cc, cnemial crest; ch, chevron; fc, fibular crest; fi, fibula; gtr, greater trochanter; lr, lateralridge; lc, lateral crest; mco, medial condyle; mt, metatarsal; obr, oblique ridge; pat, posterior antitrochanter; prz, prezygapophysis; pt, posterior trochanter; ts, trochanteric shelf. [View Larger Version of this Image (45K GIF file)]
 

Figure 3 Fig. 3. Phylogeny and body size change within paravian theropods. A temporally calibrated cladogram depicting the phylogenetic position of Mahakala and paravian body size through time and across phylogeny is shown. Characters uniting Mahakala with other dromaeosaurids include the absence of an accessory tympanic recess dorsal to the crista interfenestralis, and elongate paroccipital process with parallel dorsal and ventral edges that twist rostrolaterally distally, and the presence of a distinct ginglymus on the distal end of metatarsal II (17). Silhouettes are to scale, illustrating the relative magnitude of body size differences. Left-facing silhouettes near open circles show reconstructed ancestral body sizes. Ancestral paravian body size is estimated to be 600 to 700 g and 64 to 70 cm long (17). The ancestral deinonychosaur, troodontid, and dromaeosaurid body size is estimated at ~700 g. Large numbers (1, 2, 3, and 4) indicate the four major body increase trends in Deinonychosauria. See the supporting online material for further ancestral body size reconstruction data. Ma, Maastrichtian; Ca, Campanian; Sa, Santonian; Co, Coniacian; Tu, Turonian; Ce, Cenomanian; Ab, Albian; Ap, Aptian; Bar, Barremian; Hau, Hauterivian; Va, Valanginian; Ber, Berriasian; Ti, Tithonian; Ki, Kimmeridgian. Ma, million years ago. [View Larger Version of this Image (35K GIF file)]
 

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