THE MOST DIVERSE FOSSIL SQUAT LOBSTER ASSEMBLAGE IN THE WORLD

The Friedrich Bachmayer Collection, housed at the Natural History Museum, Vienna, Austria is composed of Late Jurassic (Tithonian) fossils from reefal limestones found near Ernstbrunn, Austria. Containing over 7000 individual decapod crustacean fossils, it is the largest known Mesozoic decapod collection in the world, and consists of > 80 species. Since the galatheoids (commonly called squat lobsters and of which there are > 800 species today) contained within the collection have recently been the subject of two taxonomic monographs and the collection houses the largest number of fossilized individuals and greatest fossil galatheoid diversity known in the world, including the first appearance of four of the seven extinct and extant families, they were chosen for a population study. All identifiable galatheoid carapaces, discounting external molds, were tallied, totaling 2170 specimens. Of those, 1665 were identifiable to the species level, across 53 different species. Two species counted herein are still undescribed. Rarefaction curves for both genera and species appear to have leveled, so not many more new galatheoid taxa are expected from the Ernstbrunn Limestone. Several diversity metrics that take into account the number of specimens per species also indicate that the Ernstbrunn assemblage is very diverse. The Shannon Index for Ernstbrunn is 2.50; for comparison, this index is only 1.12 for a smaller mid-Cretaceous (Albian) galatheoid fauna from Koskobilo, Spain (482 individuals across 10 species). Chao1 values for the Ernstbrunn and Spanish galatheoid faunas are 64 and 11, respectively. The Simpson Index (1-D) gives a value of 0.83 for Ernstbrunn and 0.58 for Koskobilo (i.e. evenness is higher for Ernstbrunn). Results of this study add to the number of galatheoid species from Ernstbrunn and affirm that this galatheoid assemblage is the richest in the fossil record based on several diversity metrics.