Giant extinct freshwater turtles discovered


This 13 February 2020 video says about itself:

Stupendemys geographicus – the largest freshwater turtle

Researchers discovered new Stupendemys geographicus specimens in the Urumaco Formation, Venezuela, and La Tatacoa Desert in Colombia. The new specimens revealed that the shell of male Stupendemys had horns. Researchers estimate that the CIAAP-2002-01 specimen had a body mass between 871 kg and 1145 kg. According to palaeontologist Marcelo Sánchez: “The carapace of some Stupendemys individuals reached almost three meters, making it one of the largest, if not the largest turtle that ever existed”.

From the University of Zurich in Switzerland:

Extinct giant turtle had horned shell of up to three meters

February 12, 2020

Summary: Paleobiologists have discovered exceptional specimens in Venezuela and Colombia of an extinct giant freshwater turtle called Stupendemys. The carapace of this turtle, which is the largest ever known, measured between 2.4 to almost 3 meters. Moreover, the shell of male Stupendemys had horns – a rare feature in turtles.

The tropical region of South America is one of the world’s hot spots when it comes to animal diversity. The region’s extinct fauna is unique, as documented by fossils of giant rodents and crocodylians -including crocodiles, alligators, caimans and gavials — that inhabited what is today a desert area in Venezuela. Five to ten million years ago, this was a humid swampy region teeming with life. One of its inhabitants was Stupendemys geographicus, a turtle species first described in the mid-1970s.

Giant turtle 100 times heavier than its closest relative

Researchers of the University of Zurich (UZH) and fellow researchers from Colombia, Venezuela, and Brazil have now reported exceptional specimens of the extinct turtle recently found in new locations across Venezuela and Colombia. “The carapace of some Stupendemys individuals reached almost three meters, making it one of the largest, if not the largest turtle that ever existed,” says Marcelo Sánchez, director of the Paleontological Institute and Museum of UZH and head of the study. The turtle had an estimated body mass of 1,145 kg — almost one hundred times that of its closest living relative, the big-headed Amazon river turtle.

Males carried horns on their carapace

In some individuals, the complete carapace showed a peculiar and unexpected feature: horns. “The two shell types indicate that two sexes of Stupendemys existed — males with horned shells, and females with hornless shells,” concludes Sánchez. According to the paleobiologist, this is the first time that sexual dimorphism in the form of horned shells has been reported for any of the side-necked turtles, one of the two major groups of turtles worldwide.

Despite its tremendous size, the turtle had natural enemies. In many areas, the occurrence of Stupendemys coincides with Purussaurus, the largest caimans. This was most likely a predator of the giant turtle, given not only its size and dietary preferences, but also as inferred by bite marks and punctured bones in fossil carapaces of Stupendemys.

Turtle phylogeny thoroughly revised

Since the scientists also discovered jaws and other skeleton parts of Stupendemys, they were able to thoroughly revise the evolutionary relationships of this species within the turtle tree of life. “Based on studies of the turtle anatomy, we now know that some living turtles from the Amazon region are the closest living relatives,” says Sánchez. Furthermore, the new discoveries and the investigation of existing fossils from Brazil, Colombia and Venezuela indicate a much wider geographic distribution of Stupendemys than previously assumed. The animal lived across the whole of the northern part of South America.

Opossums pollinating Brazilian flowers, new discovery


This 7 February 2020 video from Brazil is called Big-eared opossum licking the nectar.

From the Ecological Society of America:

Pollinating opossums confirm decades-long theory

February 12, 2020

In Brazil there is a plant so strange that researchers predicted — and 27 years later, proved — that opossums are key to its pollination. The findings are published in the Ecological Society of America’s journal Ecology.

The plant Scybalium fungiforme, a little-known fungus-like species of the family Balanophoraceae, has bunches of tiny pale flowers that are surrounded and housed by a hard surface of bracts — like on an artichoke. Because of their scale-like shape, the bracts must be opened or peeled back to expose the flowers and nectar to pollinators such as bees.

While most species in the Balanophoraceae plant family are primarily pollinated by bees and wasps, researchers at São Paulo State University in Botucatu, Brazil hypothesized something different. They thought that opossums, with their opposable thumbs, would be a key pollinator for S. fungiforme due to the challenging bracts covering the flowers.

In the early 1990s Patrícia Morellato, a professor at the university, first made the prediction. She and her colleagues studied the plant and they captured an opossum with nectar on its nose. There observations went unpublished because they did not record or obtain direct evidence of the opossums pollinating the flowers.

Felipe Amorim, assistant professor at the university and lead author on this study, did not encounter the plant until 2017, but hypothesized that a non-flying mammal is needed for pollination based on the flower morphology. In April 2019 his students independently hypothesized that perhaps rodents could act as the main pollinators of this species. “At that time, neither of us knew anything about the unpublished observations made by Patrícia in the ’90s”, he explains.

In May 2019 Amorim and a team of researchers went to Serra do Japi Biological Reserve, located about 50 km from the area studied by Morellato, and set up night-vision cameras to record the activity of nocturnal flower visitors. The cameras captured opossums removing bracts from the fungus-like plant and pushing their faces into the flowers to eat the nectar. It was the first direct evidence of opossums pollinating the plant.

Amorim sent his colleague Morellato the footage. “When she watched the videos,” he says, “she sent me a voice message as excited as we were when we first saw the opossum visiting the flowers, because it was the first time she saw something she predicted two and a half-decades ago!”

The researchers had made the opossum prediction based on “pollination syndrome” — the concept that floral attributes such as color, morphology, scent, and size reflect the adaptation of a plant species to pollination by a certain group of animals. Opossums, having “hands” with opposable thumbs, are capable of peeling back the scale-like leafs covering the flowers of S. fungiforme. The plant does have other floral visitors that act as secondary pollinators once the bracts are removed — bees and wasps dominate the crowd, but a surprising additional visitor was several hummingbirds.

“Based on the flower morphology,” Amorim says, “Morellato, my students, and I could safely predict that this plant should be pollinated by non-flying mammals, but the occurrence of hummingbirds coming to the ground to visit these flowers was something completely unexpected to me.” Morellato had not seen any hummingbirds visiting this species at her study site during the ’90s, but researchers have more recently obtained indirect evidence that hummingbirds visit the plant in both study locations.

The authors hope to continue studying the pollinators of S. fungiforme to assess the efficiency of each group of flower visitor (mammals, hummingbirds, and bees and wasps) in order to quantify their contribution to the fruit production of this plant. They also want to analyze the chemical compounds of nectar and floral scent, which can reveal much about the adaptation of a plant for a given group of pollinator.

Overall, the story is an interesting one to tell, the culmination of nearly three decades of prediction and observation based on the hard shell surrounding a bunch of tiny flowers. Amorim contemplates that “at the time that non-flying mammals were first predicted as the pollinators of this fungus-like plant, I was about 11 years old, and most of the authors of this study hadn’t even been born!”