Episode 31 – The First Frogs of the Age of Dinosaurs!

Past Time
Past Time
Episode 31 - The First Frogs of the Age of Dinosaurs!


Every discovery we make in natural history happens thanks to specimens. Fossil bones, shells, footprints, coprolites, tissue samples—even field notes and photograms—are the building blocks scientists use to tell the story of life on our planet. On Past Time, we talk a LOT about the contributions of museums and scientists to the story of life. However, we don’t often address the specific specimens that help tell that story. Even one little bone can reveal great truths.


Meet DMNH 2018-05-0002, an eyelash-sized bone from the 213-million-year-old Chinle Formation of eastern Arizona. The bone is housed in the fossil collections of the Perot Museum of Nature and Science in Dallas, Texas. DMNH 2018-05-0002 (I refuse to abbreviate!) is a right ilium (pelvic bone) of a frog that was likely only a few centimeters long in life. This fragile treasure is the oldest evidence for a frog on the entire North American continent, predating the next fossil by 30 million years! One little bone leads to a huge expansion in the story of frogs, the most abundant group of amphibians on Earth!

Dr. Michelle Stocker holds up DMNH 2018-05-0002 embedded in matrix and wax. It’s THAT small. Image from vt.edu

These amazing frogs were published in Biology Letters by Virginia Tech paleontologist Michelle Stocker, a world-renowned expert on Triassic ecosystems. Dr. Stocker and her team have done a lot of recent work on MICROVERTEBRATES, the bones and teeth of tiny animals. Microvertebrate fossil sites are those that preserve large quantities of tiny (~1 centimeter and smaller) bits, and they can tell us a lot about the smaller animals in an environment. Some paleontologists use sifting and fine-mesh screens to collect bones out of these sediments. In this case, Dr. Stocker and her team prepared bones out of blocks of sediment using microscopes and extremely fine tools. Hat-tip specifically to Ben Kligman, a Virginia Ph.D. student who is pioneering these refined preparation techniques!

Images of the Chinle frog fossils described by Stocker et al. (2019). DMNH 2018-05-0002 is featured in the top row. The lower images include other frog ilia and jaw fragments found in the collections of Petrified Forest National Park and the Museum of Northern Arizona.

DIG DEEPER (Links and Reading)

  • The Perot Museum of Nature and Science in Dallas, Texas is a world-class museum with incredible collections of Cretaceous vertebrates from Texas, Alaska, and across the western United States. Obviously, there are some Triassic treasures in the collection, too! The exhibits include classic American dinosaurs like Alamosaurus, Tyrannosaurus, and Tenontosaurus and some newcomers like Convolosaurus, Nanuqsaurus, and Ugrunaaluk.
  • The original scientific paper in Biology Letters by Dr. Michelle Stocker and her colleagues describes the Chinle frogs, including DMNH 2018-05-0002 and a series of other tiny frog fragments from Triassic Arizona.
  • For general audiences, Virginia Tech put out a press release describing the discovery, including a video featuring Dr. Stocker.
  • Petrified Forest National Park (PEFO) is an amazing park in eastern Arizona. Named for the fossilized remains of ancient forests from the Triassic Period, PEFO contains some of the largest fossil exposures from the Triassic Period of North America. DMNH 2018-05-0002 was found just to the south of the park, but some additional Triassic frog bits have been found in the PEFO fossil collections! Seriously, go to PEFO if you like beautiful and desolate vistas!
  • VT Paleobiology is a collaborative effort of all of the Virginia Tech paleontologists, including Dr. Stocker. Their research ranges from Cambrian invertebrates, to Triassic ecosystems, to Cretaceous tyrannosaurs, and beyond!


  • The amazing artwork used for the promo image is a painting by paleo-artist Andrey Atuchin commissioned for this study. Check out his artwork at Deviantart and Twitter!
  • Frog sound effects from freesound.org user flapknot.

Filed under: Arizona, Dallas, Dinosaurs, Fossils, Frog, Mesozoic, Museum, Paleontologists, Petrified Forest, Phytosaur, Triassic, amphibian, amphibians, collections, dinosaur, fossil, frogs, paleontologist, phytosaurs

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