Convergent avialan brain morphology in Sinovenator (Troodontidae, Theropoda)

Abstract Multiple modifications to the skull and brain anatomy occurred along the lineage encompassing bird-line theropod dinosaurs and modern birds. Anatomical changes to the endocranium include an enlarged endocranial cavity, relatively larger optic lobe that implies elevated visual acuity, and proportionately smaller olfactory bulbs that suggests reduced olfaction. Here, we use micro-computed tomographic (CT) imaging to reconstruct the endocranium and its brain structures from an exceptionally well-preserved skull of Sinovenator changii (Troodontidae, Theropoda). While its overall morphology resembles the typical endocranium of other troodontids, Sinovenator also exhibits unique endocranial features that are similar to other paravian taxa and non-maniraptoran theropods. Landmark-based geometric morphometric analysis on endocranial shape of non-avialan and avian dinosaurs points to the overall brain morphology of Sinovenator most closely resembling that of Archaeopteryx , thus indicating convergent evolution of avialan brain morphology in troodontids and wide existence of such architecture in Maniraptora. Institutional abbreviations : IVPP , Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing 100044, China. PMOL , Paleontological Museum of Liaoning, Shenyang 110034, China.