High Quality Content by WIKIPEDIA articles! Hallirhoidae is an extinct family of lithistid demosponges found throughout the world from the Cretaceous to the Eocene, whereupon they became extinct. The highest concentration of species occurred in the Tethys Ocean during the upper Cretaceous. The hallirhoid demosponges were very distinctive-looking, largely pear-shaped sponges that were attached to the seafloor by a long stem-like stalk.