A new Early Cretaceous dinosaur locality in the Twin Mountains Formation at Proctor Lake, Texas, reveals information concerning hypsilophodontid social behavior. Both adults and congregations of juvenile hypsilophodontids occur at the site. Recent excavation of one mass of juveniles shows that it occurs in a shallow depression on a paleosol surface. The distribution of skeletal elements and age structure of individuals within congregations may indicate nesting and parental care of the young after hatching. Hypsilophodontids occupied the site over a long period of time, indicating attraction to the area for some reason. The region was a semi-arid flood plain within a lowland valley. Attractive features of the site may have included abundant vegetation and water or protection from predators. The accumulations of juvenile bones may represent attritional mortality of individuals from a single clutch or a succession of clutches in the nest area.