The rise of feathered dinosaurs: Kulindadromeus zabaikalicus, the oldest dinosaur with 'feather-like' structures

PeerJ. 2019 Feb 1;7:e6239. doi: 10.7717/peerj.6239. eCollection 2019.

Abstract

Diverse epidermal appendages including grouped filaments closely resembling primitive feathers in non-avian theropods, are associated with skeletal elements in the primitive ornithischian dinosaur Kulindadromeus zabaikalicus from the Kulinda locality in south-eastern Siberia. This discovery suggests that "feather-like" structures did not evolve exclusively in theropod dinosaurs, but were instead potentially widespread in the whole dinosaur clade. The dating of the Kulinda locality is therefore particularly important for reconstructing the evolution of "feather-like" structures in dinosaurs within a chronostratigraphic framework. Here we present the first dating of the Kulinda locality, combining U-Pb analyses (LA-ICP-MS) on detrital zircons and monazites from sedimentary rocks of volcaniclastic origin and palynological observations. Concordia ages constrain the maximum age of the volcaniclastic deposits at 172.8 ± 1.6 Ma, corresponding to the Aalenian (Middle Jurassic). The palynological assemblage includes taxa that are correlated to Bathonian palynozones from western Siberia, and therefore constrains the minimum age of the deposits. The new U-Pb ages, together with the palynological data, provide evidence of a Bathonian age-between 168.3 ± 1.3 Ma and 166.1 ± 1.2 Ma-for Kulindadromeus. This is older than the previous Late Jurassic to Early Cretaceous ages tentatively based on local stratigraphic correlations. A Bathonian age is highly consistent with the phylogenetic position of Kulindadromeus at the base of the neornithischian clade and suggests that cerapodan dinosaurs originated in Asia during the Middle Jurassic, from a common ancestor that closely looked like Kulindadromeus. Our results consequently show that Kulindadromeus is the oldest known dinosaur with "feather-like" structures discovered so far.

Keywords: Feathered dinosaurs; Jurassic of Siberia; Palynology; U-Pb dating.

Grant support

This work was supported by the Fonds National de la Recherche Scientifique (FRIA grant), the Russian Foundation for Basic Research (No. 17-04-01582), the Russian Science Foundation (No. 18-17-00038), the Siberian Branch of the Russian Academy of Science (program IX.137.1) and the European Research Council (StG “ISoSyC”, 336718). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.