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.

Romualdo组（Araripe盆地）以保存完好的化石而闻名世界，但恐龙记录却很少。在这里，我们描述了一种新的腔骨龙，这是从该地层单元由深色页岩组成的基底层中回收的第一个四足动物。ARASARAURUS MUSEUNACIONALI GEN。等。十一月 股骨头远端，胫骨近端半部和大腿骨不全是不完整但有关节的右后肢。新物种与其他腔骨龙的不同之处在于胫骨的内侧窝，而第二，第三和第四位是对称的。系统发育分析发现与左龙沙雷密切相关的鼠龙，形成基础的腔骨龙。古组织学表明该标本是幼体，估计体长约为3.12 m。新的分类单元代表了Araripe盆地中首次出现的基部腔骨龙，并暗示了这一群体在下白垩纪的广泛分布。