Discoveries:

In 2016, researchers from University of Massachusetts, Amherst, collected 500 subfossil elements representing both extinct and extant species from extraordinary, submerged cave sites in the plateau region of southwestern Madagascar. The primary submerged cave site (Vintany) within Tsimanampesotse National Park was scheduled to be opened for tourism including recreational activities in 2021. The proposed recreational activities for the site presented a substantial risk to the fossil specimens from this intact fossil graveyard. 

The abundance of well-preserved faunal remains found by divers in the Tsimanampesotse cave systems (Vintany Cave, image 1), offered a unique opportunity to collect important new material to document ecological processes and timing during the past 5000-8000 years of extinction and decline among the megafauna of Madagascar. We predicted that taxonomic, genomic and isotopic data from the specimens would provide new evidence for community dynamics over time among poorly known endemic large reptiles (tortoises and crocodilians). Therefore, we proposed two expeditions to recover and document fossil material related to the extinction of the horned crocodiles and the giant tortoises of Madagascar. 

            During the course of our expeditions, our team of over fourteen international scholars were able to recover over 500 new fossils from the submerged caves. These collections will eventually be housed in a newly proposed Museum of Natural History at the University of Antananarivo where they will be available for local and international study. 

From the caves, we were able to recover eight nearly complete specimens of the extinct crocodile (Voay robustus), and additional fragmentary material including the first known juvenile of the species. These nearly complete specimens represent the first in the world to document the overall size of this species. We also examined and catalogued another six specimens held by the paleontology department at the University of Antananarivo (image 5) and additional seven individuals from the collections at Centre Val Bio at Ranomafana National Park. Our documentation of 21 new specimens for the extinct crocodile represents a tripling of the known number of specimens for this species in the world (table, image 2). We were also able to extract genomic data (image 6) for several individuals including one individual with distinct features that may represent a new species. 

We were able to obtain a nearly complete giant tortoise specimens from one of the submerged caves and another from a nearby site. We are currently using DNA and isotopes to understand how these tortoises may have lived during the period prior to extinction. 

During both expeditions we scanned fossils using photogrammetry (image 3) and a CT scanner to provide records and 3D printed replicas for study and for display in the local museum at the entrance to Tsimanampesotse National Park (image 4). We also made replicas for outreach and education at AMNH and University of Antananarivo. Our digital images will be deposited in Morphosource and be made available for research worldwide.  

Broader Societal Impacts:

We worked closely with Malagasy scholars and collaborators throughout the project to provide opportunities for knowledge exchange and for professional development. One of our Malagasy colleagues was able to participate in a conference in Los Angeles and is now employed as the new collection manager for the Centre Val Bio Natural History Museum in Madagascar and three others are completing the doctoral degrees on collections made during our expeditions. Six American scholars have had opportunities to conduct research as part of our expeditions and one received an NSF supplement for research. She has gone on to her doctoral studies at New York University. 

We have pursued opportunities to share these discoveries with audiences around the world including recent public lectures at Paleofest (Rockford, Illinois) and TetZooCon (London, UK). In a major public outreach and education opportunity, scholars from University of Massachusetts, Amherst, the American Museum of Natural History, Fordham University and the University of Antananarivo were featured in a PBS documentary (“When Whales Walked”) about the evolutionary lineages of animals including crocodiles. More broadly, this project fostered and continues to promote interdisciplinary research and interaction among academic researchers and local stakeholders from the U.S. and Madagascar.

Intellectual Merit: This research has helped us to document the relationships between modern and recently extinct crocodiles and giant tortoises in Madagascar. Additionally, these collections and associated stratigraphic data will allow us to continue to clarify the relationship between fine scale temporal dynamics of genomic diversity, diet and faunal change and the arrival of humans in southwestern Madagascar during the period prior to the extinction of the megafauna. Comparison of this intact cave depositional series with previous collections of these and other species across Madagascar will help explain changes in species composition, abundance, and genetic diversity within communities following the arrival of humans and during known climate shifts on the island. 

Last Modified: 07/01/2024
Modified by: Evon R Hekkala