Armed with playlists, tweezers and patience, researchers at Petrified Forest National Park announced the discovery of a new species of tanystropheid reptile in the journal Palaeodiversity on Aug. 1.
“The study, led by seasonal paleontologist Alaska Schubert, describes the anatomy of Akidostropheus oligos and compares it to other related Triassic animals from fossils that are relatively common from Europe and China but are extremely rare in North America,” according to a National Park Service press release. “The new species itself is named Akidostropheus oligos, meaning ‘tiny, spiked backbone,’ because a single neck bone is remarkably small (less than 7 mm tall, smaller than the average pinky fingernail) and has a unique spike on top.”
While the park takes its name from the roughly 14 different species of fossilized conifers preserved from the Triassic period — towering trees that thrived some 220 million years ago, most notably the trunks traditionally identified as Araucarioxylon arizonicum, Arizona’s state fossil — scientists from NPS and the Smithsonian are uncovering an even deeper evolutionary story, grain by grain. These discoveries come from the Chinle Formation, dated to about 220 million years ago, when Arizona lay near the equator at the heart of the supercontinent Pangea.
“It would have been very small … the whole animal would have fit in your palm, probably would have looked like just a little lizard with a longer-than-average neck, and [it] probably would have been a midline row of spikes coming out of its back, and then potentially some scale features,” Schubert said. “[But] until we find a whole animal, it’s going to be hard to say.”
created replicate of the fossil at 20 times the size.
Tanystropheids are classified as archosauromorphs, an outgroup ancestral to archosauria, which later split into the crocodile and bird lineages. These unusual reptiles were short-lived and confined to the Triassic period, reflecting a rapid period of evolution that took place following the Earth’s most severe mass extinction event — “The Great Dying” — that took place around 252 million years ago when about 96% of marine species went extinct.
However, the tanystropheids from PEFO are only distantly related to its more famous Mesozoic marine reptiles such as mosasaurs, with Schubert citing it as an example of convergent evolution, because the Chinle rock formation is a terrestrial deposit of a semitropical environment.
“Oh, the spikes on the vertebrae for sure make this species unique compared to other Triassic reptiles,” Schubert said. “Tanystrophiade is a clade within a larger group called archosauromorphs, and there are currently no other archosauromorph ever that have been found with bony spikes coming out of their vertebrae. That is something that’s not only new to tanystrophiade, it’s also new to archosauromorph.”
The leading hypothesis for the spikes is as a defensive mechanism, according to Schubert. Additionally, the diet of the new species remains uncertain because skull and tooth material has not been found.
“One of the things that makes the tanystrophiade clade unique is their really long necks and if you have a really long neck, then you’re also liable to get it chomped by predators,” Schubert said.
Unlike traditional fossil excavation in which paleontologists dig easily visible bones from bedrock, matrix sorting is a method designed to recover tiny fossils, often less than a centimeter long. Sediment from fossil-rich sites is first soaked in water to break it apart, then washed through a series of smaller and smaller fine mesh screens. Researchers then painstakingly examine the individual grains of sediment under microscopes, to find teeth and other microfossils.
“There are some days you just don’t have the patience for it, but other times it can be a surprisingly Zen activity where you put in your headphones, put on your favorite album, and just go at it for hours and hours,” Schubert said. “It’s shocking how quickly the time passes sometimes.”
It can leave plenty of time for Schubert to get caught up on bluegrass music, though gypsy punk rock and funk band the Ohio Players have been known to rattle the walls of the PEFO bone lab. The latter was immortalized by park researchers in 2023, who named the oldest known caecilian, a species of burrowing amphibian, after the Ohio Players’ 1972 song “Funky Worm,” giving it the scientific name Funcusvermis gilmorei.
The process of matrix sorting is tedious — for example, with Funcusvermis gilmorei, two tons of sediment was collected and one Funcusvermis gilmorei jawbone was found every 32 pounds, according to PEFO Paleontologist Adam Marsh.
“One of the big takeaways from this study is that it highlights the importance of doing the microvertebrate work at these sites,” Schubert said. “Because obviously the environment isn’t just the large animals that live in it — there are so many small creatures running around that fill in the ecological niches.”
Both the recently discovered tanystropheid and Funcusvermis gilmorei were discovered from sediment collected from a fossil locality known as Thunderstorm Ridge, discovered in 2018 in the park’s expansion lands, east of Blue Mesa. The site sits on land formerly known as the Paulsell Ranch, acquired by the park in 2011 after the 2004 Petrified Forest Expansion Act authorized the addition of about 125,000 acres. Nearly 300 new fossil localities were identified during surveying that took place from 2016 to 2018, with Thunderstorm Ridge emerging as among the most significant.
“These fossil beds [of Thunderstorm Ridge] are very productive and tens of thousands of fossil bones and bone fragments have been found within them,” a Friends of Petrified Forest blogpost from 2021 reads. “To date, paleontologists have identified 56 species of vertebrates, including several species of fresh water shark; bony fish species including species similar to modern gar fish; coelacanths; giant salamander-like amphibians known as metoposaurs; frogs; a diversity of reptiles including close relatives of early dinosaurs and stem-mammals.”
“We still have a bunch of bones from Thunderstorm Ridge that haven’t really been studied in depth, so there are so many ongoing projects,” Schubert said. “It’s tough because how do you even decide what to work on first?”
