Giant subfossil lemur graveyard discovered, submerged, in Madagascar.

In October, 2014, we organized a paleontological expedition toinvestigate flooded freshwatercavesinTsimanampetsotsa NationalPark, Madagascar, located in the arid southwestern region of thecountry where the karst landscape is pocked with dry caves andlarge water-filled sinkholes (Fig. 1). Our team of nine scuba diverswas led by Phillip Lehman of the Dominican Republic SpeleologicalSociety (Supplementary Online Material [SOM] Video 1). The dis-covery of subfossils in Tsimanampetsotsa was made initially byRyan Dart of Antananarivo. The director of Tsimanampetsotsa Na-tional Park, Mr. Lovasoa Dresy, immediately recognized theirimportance to science and encouraged the work reported here.Substantial numbers of subfossil remains were found in threecaves. In Aven Cave we discovered what is likely to be the singlelargest cache of giant subfossil lemurs ever uncovered. The othertwo fossiliferous caves were Mitoho and Malaza Manga. Subfossilshad been previously reported from around the entrance to MitohoCave (Perrier de la B^athie, 1934; Goodman and Jungers, 2014 ) butno underwater investigation of remains inside any of these caveshad been conducted prior to this expedition. Thus the primaryobjective was to establish the paleontological potential of thesecaves, with the principal aim of assessing the biodiversity of thesubfossil content of Aven (Fig.1).Avenisakarsticdissolutioncaveorsinkholeproducedbywaterdraining through the porous limestone shelf. It is a classic verticalsink hole with deep horizontal cave passageways, each ending in acollapse of limestone blocks. In the complex of tunnels and pas-sages, many sections can be accessed only through narrow re-strictions, a challenge that requires advanced cave divingtechniques as a precondition to safe exploration of this dark, un-charted subterranean environment (Fig. 2C). It is readily apparentthat these spaces were dry in the past as there is substantial spe-leothem (stalactite and stalagmite) formation. The full extent ofAven's passageways has yet to be explored, but our team laid about268 m of safety line during the expedition, running at an averagedepth of 42 m.Theopeningof the sinkholeis some25 min circumference, andthe water table is located 10e12 m below the rim. A small island inthe center of the water pool is the very top of a debris cone, what'sleft of the collapsed overhead rock (Fig. 1). The mound falls gentlyintothe depths of the lit cavern toabout25 m, fromwherethe caveextends into the blackness in all directions. It is in this transitionalzone where most of the more visible subfossil remains have beenlocated.Duringthesurvey,standardcavemappingtechniqueswereemployed to locate and mark areas with materials of interest, suchas dense bone accumulations or the location of important speci-mens. It became immediately apparent that there were multiplesites of import and hundreds of cranial and postcranial remains