Guest post by Gregg Gunnell, Division of Fossil Primates
(A version of this column originally appeared in the Duke Lemur Center newsletter)
Lagerstätten – that word sends a shiver of excitement up and down the spine of every paleontologist.
In German the word means ‘storage place’ or ‘deposits,’ but in paleontology it has come to mean a very rich fossil deposit that contains complete or nearly complete specimens that sample a wide variety of the creatures living at a certain time.
A cave diver and subfossil specimen in Aven Cave, Madagascar. The plastic triangle is a scale for photographs of the specimen in situ. (Image by Phillip Lehman and Pietro Donaggio-Bitner)
As you might imagine, Lagerstätten are quite rare. Some of the more famous examples are the Burgess Shale in Canada which preserves soft body outlines of ancient (530 million years ago) Cambrian animals; the Jurassic (150 Ma) Solenhofen limestones in Germany where the famous Archaeopteryx is found; and the middle Eocene (45 Ma) Messel Oil Shale in Germany which preserves whole skeletons of many birds, mammals, reptiles, amphibians, and insects.
I have had the good fortune to be in on the discovery of two Lagerstätten in addition to studying specimens from two others. The first one our team discovered was in 1998 in Pakistan, a place we named Gandhera Quarry. It preserves a remarkable wealth of early Eocene (52 Ma) mammals from Balochistan Province – an assemblage that has yet to completely studied.
But the latest and most exciting to me as Director of the Division of Fossil Primates in the Duke Lemur Center happened late last year in Southwest Madagascar.
The discovery of subfossils at a place called Aven Cave was known to local people, but not reported to the scientific community until an Australian cave diver named Ryan Dart saw it. The cave and its specimens are underwater. The specimens are called subfossils, because they aren’t old enough to have completed (or in some cases even started) the fossilization process.
A joint team from the University of Antananarivo, Duke University, University of Massachusetts, Brooklyn College and Midwestern University led an expedition to this cave site in October 2014. Cave divers Phillip Lehman and the Dominican Republic Speleological Society dive team helped us find a treasure trove of subfossils.
Lemur skulls, as they were found in the cave, with a scale marker. (Photo courtesy of Phillip Lehman and Pietro Donaggio-Bitner)
Only a preliminary survey has been made of Aven Cave to date, but it is clear already that it is one of the richest subfossil sites ever discovered in Madagascar. The initial list of animal specimens found in the cave includes three genera of extinct lemurs (Pachylemur, Mesopropithecus, and Megaladapis) as well as one species of a living form, Lemur catta, the familiar ring-tailed lemur. In addition to the primates there are abundant specimens of bats (Hipposideros), carnivores (the extinct fossa Cryptoprocta spelea as well as a smaller, still living species, C. ferox), two species of rodents, an extinct pygmy hippopotamus, crocodiles, turtles, and two bird species including the extinct elephant bird Mullerornis.
Not only is there a diverse assembly of species coming from Aven Cave, the sample is also abundant, with many species represented by multiple specimens. Many specimens appear to be complete or nearly complete skeletons.
The expedition was aided by Mr. Lovasoa Dresy, the director of Tsimanampetsotsa National Park, and was generously supported by the National Science Foundation and the National Geographic Society.
We anticipate many more and surprising discoveries in the future. Stay tuned for updates from Aven Cave!