The first theropod dinosaur (Coelurosauria, Theropoda) from the base of the Romualdo Formation (Albian), Araripe Basin, Northeast Brazil

Juliana Manso Sayão,Juliana Manso Sayão,Helder De Paula Silva,Xin Cheng,Renan Alfredo Machado Bantim,Arthur Souza Brum,Antônio Álamo Feitosa Saraiva,Alexander W A Kellner,Flaviana Jorge De Lima,Xin Cheng,Rafael Cesar Lima Pedroso De Andrade

doi:10.1038/s41598-020-67822-9

Abstract

The Romualdo Formation (Araripe Basin) is worldwide known for the large number of well-preserved fossils but the dinosaur record is rather scarce. Here we describe a new coelurosaur, which is the first tetrapod recovered from the basal layers of this stratigraphic unit that consist of dark shales. Aratasaurus museunacionali gen. et sp. nov. is known by an incomplete but articulated right hind limb with the distal portion of the femur, proximal half of tibia and incomplete pes. The new species differs from other coelurosaurs by a medial fossa in the tibia and digits II, III and IV being symmetric. The phylogenetic analysis recovered Aratasaurus museunacionali closely related to Zuolong salleei, forming a basal coelurosaur lineage. The paleohistology indicate that the specimen is a juvenile, with an estimated body length around 3.12 m. The new taxon represents the first occurrence of basal coelurosaurians in the Araripe Basin and suggests a widespread distribution of this group during the Lower Cretaceous.

Highlights

The limited amount of theropod material is not exclusive of B razil[9]
The material was donated to the Museu de Paleontologia Plácido Cidade Nuvens by a local resident of Santana do Cariri who informed that it came from the Mina Pedra Branca
The fossil material is incomplete and very compressed, the cross sections of the femur, tibia and metatarsi are similar to the ones of Zuolong salleei[41], which suggests that Aratasaurus museunacionali exhibited a similar body dimensions, estimated in 34.25 kg of body mass and 3.12 m of total length (Fig. 10)

Summary

Introduction

Among the regions where such reptiles are found in the country is the Araripe B asin[10] This tectonic structure is worldwide known for the well preserved and diverse fossil biota[11,12,13,14]. The specimen was on loan to the Museu Nacional/UFRJ for preparation purposes and luckily not affected by the big fire of September 2nd of 201825. The discovery of this new species increases the dinosaur distribution in the several lithological facies of this stratigraphic unit, that is more diverse than previously thought as pointed before[26]

Methods

Results

Conclusion