Two fossil discoveries from the East African Rift reveal new information about the evolution of primates, according to a study published online in Nature this week led by Ohio University scientists.
This image shows a holotype specimen of Rukwapithecus fleaglei (RRBP 12444A), a partial right mandible bearing the lower fourth premolar, first and second molars, and partially erupted third molar, in lateral view.
The team’s findings document the oldest fossils of two major groups of primates: the group that today includes apes and humans (hominoids), and the group that includes Old World monkeys such as baboons and macaques (cercopithecoids).
Geological analyses of the study site indicate that the finds are 25 million years old, significantly older than fossils previously documented for either of the two groups.
For the first time, the study documents that the two lineages were already evolving separately during this geological period (Oligocene).
The first specimen of Archelon (YPM 3000) was collected from the Pierre Shale of South Dakota in 1895.
The largest Archelon fossil, found in the Pierre Shale of South Dakota in the 1970s, measures more than 4 m (13 ft) long, and about 4.9 m (16 ft) wide from flipper to flipper. It was a marine turtle, whose closest living relative in the present day is the leatherback sea turtle.
Archelon’s fossils date to around 75-65 million years ago in the Late Cretaceous period, when a shallow sea covered most of central North America.
#34. What is your favorite prehistoric organism we have discussed in this class and why?
- Student’s Response: Suspension Feeders in general. I found them quite interesting.
…Really? Out of everything we talked about this semester—dinosaurs, weird mammals, giant armored fish—and suspension feeders are your top choice?
I feel like a failure as an educator.
All grown-ups were once children—although few of them remember it.
—Antoine de Saint-Exupéry
Painted turtles (Chrysemys picta), found in lakes and streams across North America, are one of many reptile species whose sex is determined by temperature. Eggs in warm nests are likely to hatch as females, while males hatch in cooler nests, although no one is sure why.
In recent years, many researchers have raised concerns that global warming could skew the sex ratios of these reptiles. Rory Telemeco and his colleagues at Iowa State University developed a mathematical model to predict whether the painted turtles might be affected.
Conservative climate models predict that average temperatures in the US Midwest will rise by 4 °C over the next century. The group’s model suggests that this temperature hike would result in nests of all-female hatchlings, and ultimately the extinction of these turtles.