A remarkable discovery has recently been made in an active underground stream beneath the deep hills of the Edwards Plateau. During a snorkeling excursion through the low ceilings and dark passages of Benders Cave in Comal County, Texas, researchers discovered a massive ‘lag assemblage’ of Pleistocene megafauna. It is also uniquely important, as it contains fossils of species previously unknown in the region (including giant tortoises and the lion-sized pampatheres (Homcina septentrionalis)). These discoveries are forcing paleontologists to reconsider their beliefs about the ancient climate of central Texas, as the data indicate that there was a much warmer and more humid climate during the time period previously thought to be dominated by cool, dry grasslands.
Rare fossils discovered in Benders Cave, Texas
The collection of fossils of large animals from an active stream site provided the basis for this work. According to research published in Cambridge University Press, the bones of the largest animals that lived during the Ice Age, mammoths, mastodons, saber-toothed cats and giant ground sloths, were identified. The fossils were mineralized and had a calcite coating due to prolonged exposure to carbonate-saturated groundwater; This mineralization and coating preserved the fossils in a ‘lag assemblage’ on the cave floor.
From lion-sized armadillos to giant tortoises: rare finds on the Edwards Plateau
As noted in the findings from the Jackson School of Geosciences and the University of Texas at Austin, the most notable scientific discoveries were the bones of a giant tortoise (Hesperotestudo) and a pampathere (Homacina septentrionalis). Pampatheres, which were the size of lions, are close relatives of the modern armadillo, but both species had never before been found on the Edwards Plateau. Their presence represents an extreme anomaly as both species require a warm, humid, frost-free climate, a characteristic that differs significantly from the cold, moist model accepted for the Late Pleistocene in the Edwards Plateau.
How cluster analysis revealed a 100,000-year-old warm climate
Researchers at the University of Texas faced challenges in ascertaining accurate dating of the bones; The first preliminary radiocarbon analysis of bioapatite indicated an age of about 17,000 years, although this is an inaccurate date determined due to carbonate contamination in the cave environment; Thus through the use of cluster analysis it was determined that based on fossils found at various points within a water cave in Texas, the fossils are actually from a warm climate during Marine Isotope Stage 5 which is more than 100,000 years ago.
How researchers navigated submerged cave passages
The investigation of the water cave system represents one of the first formal investigations of water-filled cave systems within the state of Texas. Compared to most excavation sites located within dry cave systems, researchers were required to use snorkel gear/wetsuits with additional underwater lighting to help provide better visibility through the stream bed/low ceiling of the cave passage. Using this type of technology and methodology, scientists were able to sample 21 different areas along the stream bed. Additionally, the results of this investigation show that underwater cave systems represent an excellent place to preserve paleobiological records of the past.
