Invertebrate remains were largely unknown at Rancho la Brea until the 1940's. At this time paleontologists started to find specimens in the matrix that was packed in the brain cavities of the larger mammals. Pit 91 and Project 23 excavations aim is to save the entire matrix from around the bones in order to find all of the microfossils. Diplopods (millipedes) have previously been identified from isolated rings or segments. Yet another interesting find in the Project 23 excavations are near-complete articulated millipedes such as these ones shown encased in asphalt sitting on a piece of wood.