A Basal Dromaeosaurid and Size Evolution Preceding Avian Flight

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Science  07 Sep 2007:
Vol. 317, Issue 5843, pp. 1378-1381
DOI: 10.1126/science.1144066
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.