New clues on the Late Cretaceous dinosaurian fauna of Mato Grosso (Central Brazil)

AGUSTIN MARTINELLI; MARCOS SALES; HEITOR FRANCISCHINI; VALERIA SCHMIDT; HECHENLEITNER, E. MARTÍN; CESAR SCHULTZ; SILANE DA SILVA CAMINHA; ROGERIO RUBERT

Cuiaba

Congreso; XXVII Congresso Brasileiro de Paleontologia; 2022

The fossil record of continental tetrapods from Cretaceous rocks of Mato Grosso State is taxonomically and numerally sparse compared to other regions of Brazil and of South America (e.g. Patagonia). For instance, it mainly includes titanosaur sauropods, abelisaurid and megaraptoran theropods, mesoeucrocodylian notosuchians and turtles. However, these records are basically fragmentary and only one species could be erected from there: Pycnonemosaurus nevesi (Theropoda, Abelisauria), discovered in the southeastern portion of the State in the 1950s. In this contribution, we report the findings made at a new fossiliferous site in the Morro do Cambambe area, Chapada dos Guimarães Municipality. These new discoveries are the result of research efforts and field work begun in 2016 that were momentarily suspended by the Covid-19 pandemic situation. The new site, namely “Anta site”, has produced abundant dinosaur remains in a ~16 m2 excavated quarry. The fossil remains include titanosaur sauropods and abelisaurid theropods. A conspicuous specimen is an individual of a new medium-sized abelisaurid, with an estimated body length of ~5 m, which include cranial (maxilla, lacrimal, basicranial and mandibular fragments) and postcranial (cervical, dorsal and caudal vertebrae, cervico-dorsal ribs, isolated caudal transverse processes, haemal arches, metatarsal III and pedal phalanges) elements. Its cervico-dorsal and caudal vertebral anatomy resembles furileusaurian abelisaurids, but some cranial bones (e.g., lacrimal) have a more generalized anatomy, resembling basal abelisauroids (Eoabelisaurus). On the other hand, titanosaur sauropods are represented by isolated and somewhat fragmentary remains of individuals of different sizes, including teeth, vertebral fragments (neural arches and vertebral centra) and appendicular elements. The fossiliferous layers were previously known as the “Cambambe Unit” or “Cambambe Formation” and have often been considered to be from the Upper Cretaceous; although, their stratigraphic affinities continue to be debated. The fossil content at the new site in the Morro do Cambambe area is certainly bringing new data on the dinosaur fauna of central Brazil during the Late Cretaceous. [ Jurassic Foundation, Ginko Research]