Thursday, 3 March 2016

Fukuivenator paradoxus: Weird New Maniraptoran

From the infamous lower Cretaceous period Kitadani Dinosaur Quarry, where the most iconic Japanese dinosaurs have been found, is Fukuivenator paradoxus. A maniraptoran, it's the first from Kitadani (and possibly Japan, unless there is some literature I'm not aware of), and the type sp├ęcimen (FPDM-V8461) exhibits an unusual mixture of basal maniraptoriform and derived dromaeosaurid characters, meaning that this theropod is an entirely new lineage of basally-branching maniraptoran. Plus, being part of this new lineage and simultaneously looking so similar to dromaeosaurids means that this is an instance of homoplasy ('convergent evolution') within Coelurosauria.

Yoichi Azuma, Xing Xu, Masateru Shibata, Soichiro Kawabe, Kazunori Miyata and Takuya Imai. 2016.  A Bizarre Theropod from the Early Cretaceous of Japan Highlighting Mosaic Evolution among Coelurosaurians. Scientific Reports. 6(20478); DOI: 10.1038/srep20478


Our understanding of coelurosaurian evolution, particularly of bird origins, has been greatly improved, mainly due to numerous recently discovered fossils worldwide. Nearly all these discoveries are referable to the previously known coelurosaurian subgroups. Here, we report a new theropod, Fukuivenator paradoxus, gen. et sp. nov., based on a nearly complete specimen from the Lower Cretaceous Kitadani Formation of the Tetori Group, Fukui, Japan. While Fukuivenator possesses a large number of morphological features unknown in any other theropod, it has a combination of primitive and derived features seen in different theropod subgroups, notably dromaeosaurid dinosaurs. Computed-tomography data indicate that Fukuivenator possesses inner ears whose morphology is intermediate between those of birds and non-avian dinosaurs. Our phylogenetic analysis recovers Fukuivenator as a basally branching maniraptoran theropod, yet is unable to refer it to any known coelurosaurian subgroups. The discovery of Fukuivenator considerably increases the morphological disparity of coelurosaurian dinosaurs and highlights the high levels of homoplasy in coelurosaurian evolution.

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