Paper No. 76-38
Presentation Time: 9:00 AM-5:30 PM
SPIDER DIVERSITY OF THE CRATO FORMATION, AN EARLY CRETACEOUS FOSSIL-LAGERSTäTTE OF NORTHEASTERN BRAZIL
Spiders are relatively rare in the fossil record, but are typically found preserved in amber and lacustrine deposits. The Crato Formation of northeastern Brazil is an Early Cretaceous Fossil-Lagerstätte and lacustrine deposit with a relative abundance of fossil spiders. The spiders are exceptionally preserved as three-dimensional geothite replacements. Many of the spiders display legs tightly curled under the body, which appears to be related to the paleosalinity of the lake in which they were deposited. Few have been formally described and include spiders from the family Dipluridae and a likely misidentified spider ascribed to the genus Cretaraneus. After redescription of the supposed Cretaraneus spider and examination of several new spiders, the diversity of this Mesozoic fossil ecosystem has been expanded. The majority of specimens are likely the same species, but are not Cretaraneus, and may belong to the family Araneidae. One of the largest specimens appears to belong to Nephilidae, the golden orb-weavers. Additionally, a single specimen likely belongs to Palpimanidae, ground-dwelling spiders that prey on other spiders. The paleogeographic distribution of these spider families has been expanded to South America during the Mesozoic, and the age range of Palpimanidae has been extended back nearly 90 million years.