Lobocarcinus lumacopius (Decapoda: Cancridae), a new species of cancrid crab from the Eocene of Fayum, Egypt

Abstract

The genus Lobocarcinus Reuss, as it is currently understood, consists of five species. Three of these species are retained: L. paulinowurtembergensis, L. indicus, and L. aegypticus. Lobocarcinus catalaunicus is referred to Neptunus, and L.? santosi is referred to Cancer. A new species, L. lumacopius, is described. Lobocarcinus forms are distinct from all other cancrids in the lobation of their anterolateral margins, high width: length ratio, and dorsal carapace ornamentation. The type species of the genus, L. paulinowurtembergensis, is abundant in the Gebel Mokattam region near Cairo. The studied specimens of L. lumacopius are from Wadi Hitan (Zeuglodon Valley), a region approximately 140 km southwest of Gebel Mokattam in the Fayum Depression. Direct comparisons are made between L. lumacopius and L. paulinowurtembergensis, and sexually dimorphic characters of L. lumacopius, including width: length ratios and abdominal and sternal elements, are identified. A key is presented to aid in the identification of the various species within the genus and to help in distinguishing Lobocarcinus from Cancer.