FUKUIVENATOR PARADOXUS WAS NOT AN EARLY-BRANCHING ALVAREZSAURIAN BUT THE FIRST BRANCHING ORNITHOMIMID FROM JAPAN

MESO JORGE GUSTAVO; QIN, Z.; PITTMAN, M.

Buenos Aires

Congreso; 1° Reunión Virtual de Comunicaciones de la Asociación Paleontológica Argentina; 2022

Asociación Paleontológica Argentina

Coelurosauria is a well-supported clade of later-diverging theropod whose interrelationships are complex, but that contains a large diversity of mostly carnivorous and some herbivorous non-avian theropods as well as living birds. In 2019, Hartman and collaborators recovered Fukuivenator paradoxus Azuma, Xu, Shibata, Kawabe, Miyata and Imai (2016) as an early-branching alvarezsaurian, based on the presence of a maxilla with promaxillary fenestra entering promaxillary recess, six sacral vertebrae, distal anteroposterior width of transverse processes on caudal vertebrae 1-4 tapered, ulna with a prominent proximomedial process, and distal extent of femoral lateral condyle past medial condyle that is > 10% of distal femur width. The holotype specimen was included in a matrix of 1000 characters and 172 avian and non-avian theropod taxa, and a phylogenetic analysis was performed using TNT. A strict consensus shows Fukuivenator nested within Ornithomimosauria as an early-branching ornithomimid. The synapomorphies that support this position are: maxillary process posteriorly extended separating maxilla from nasal posteriorly to external nares, number of caudal vertebrae between 35-40, coracoid with shallow ventral blade and elongate posteroventral process, metacarpal III approximately equal or greater than 50% compared to anteroposterior diameter of metacarpal II, manuals phalanges with flexor processes on proximal portion of ventral surfaces, and medial side of metacarpal II not expanded. Our results suggest that Ornithomimosauria clade had its origin in Asia, and that Europe played an important role as a dispersal center, especially during the Lower Cretaceous.