A fast-growing basal troodontid (Dinosauria: Theropoda) from the latest Cretaceous of Europe

Albert G Sellés,Àngel Galobart,Philip J Currie,Bernat Vila,Stephen L Brusatte

doi:10.1038/s41598-021-83745-5

Abstract

A characteristic fauna of dinosaurs and other vertebrates inhabited the end-Cretaceous European archipelago, some of which were dwarves or had other unusual features likely related to their insular habitats. Little is known, however, about the contemporary theropod dinosaurs, as they are represented mostly by teeth or other fragmentary fossils. A new isolated theropod metatarsal II, from the latest Maastrichtian of Spain (within 200,000 years of the mass extinction) may represent a jinfengopterygine troodontid, the first reported from Europe. Comparisons with other theropods and phylogenetic analyses reveal an autapomorphic foramen that distinguishes it from all other troodontids, supporting its identification as a new genus and species, Tamarro insperatus. Bone histology shows that it was an actively growing subadult when it died but may have had a growth pattern in which it grew rapidly in early ontogeny and attained a subadult size quickly. We hypothesize that it could have migrated from Asia to reach the Ibero-Armorican island no later than Cenomanian or during the Maastrichtian dispersal events.

Highlights

During the latest Cretaceous in the run-up to the end-Cretaceous mass extinction, Europe was a series of islands populated by diverse and distinctive communities of dinosaurs and other vertebrates
The new species appeared within the faunal turnover on the island in the early Maastrichtian, which helps define the origins and timings of the migratory waves that brought the newcomers to the European archipelago
Diagnosis Tamarro insperatus is a mid-sized basal troodontid distinguished by the following unique combination of characters (* marks potential autapomorphies): metatarsal II with marked plantar ridge; small foramen on the lateral surface of the plantar ridge of the metatarsal II*; sub-arctometatarsalian condition with the metatarsal III restricted to the plantar margin on its proximal part

Summary

Introduction

During the latest Cretaceous (ca. 77–66 million years ago) in the run-up to the end-Cretaceous mass extinction, Europe was a series of islands populated by diverse and distinctive communities of dinosaurs and other vertebrates. 77–66 million years ago) in the run-up to the end-Cretaceous mass extinction, Europe was a series of islands populated by diverse and distinctive communities of dinosaurs and other vertebrates. Many of these animals exhibited peculiar features that may have been generated by lack of space and resources in their insular habitats. These include dwarf sauropod and ornithischian dinosaurs with slow growth rates[1,2,3,4], anatomically bizarre small theropods[5,6], and mammals with reduced brain s izes[7]. The new species appeared within the faunal turnover on the island in the early Maastrichtian, which helps define the origins and timings of the migratory waves that brought the newcomers to the European archipelago

Methods

Results

Discussion

Conclusion