I have sufficient primary sources. Here's my fact-check. VERDICT: TRUE The viral claim is supported by the peer-reviewed study and the research institutions involved. The only caveat is scientific hedging language ("likely"/"most likely" made by an adult T. rex), which the researchers themselves use — it does not make the underlying claim false. **What the primary sources establish (claim-linked findings):** 1. **It is a genuine first — and it is a *sequence* (a trackway), found in North Dakota.** The peer-reviewed paper — Falkingham, Hups, Tamez-Galvan, Bercovici & Lyson (2026), *Journal of Vertebrate Paleontology*, DOI 10.1080/02724634.2026.2706201 — states in its abstract: *"this is an important data point that marks the first report of a trackway that is likely attributable to an adult Tyrannosaurus rex."* It describes a newly discovered **~7 m trackway of four large tridactyl tracks, each ~1 m long**, from the Upper Cretaceous **Hell Creek Formation of North Dakota**, ~33 m below the Hell Creek/Fort Union contact, estimated at **~66.5 million years old**. ([LJMU Research Online repository — accepted version of the paper](https://researchonline.ljmu.ac.uk/id/eprint/29394/)) 2. **The "first adult T. rex trackway" framing is the researchers' own, and location/ownership check out.** The research team's institutions confirm: *"While isolated footprints have been attributed to adult T. rex in the past, this is the first time scientists have described a sequence of tracks, or trackway, likely left by this most famous of dinosaurs."* They add it *"was found in 2025 on federal land administered by the U.S. Forest Service near Marmarth, North Dakota"* — i.e., southwestern North Dakota. ([LJMU university press release](https://www.ljmu.ac.uk/about-us/news/articles/2026/9/8/new-insights-into-how-the-t-rex-moved); [Denver Museum of Nature & Science press release](https://www.dmns.org/press-room/press-releases/denver-museum-of-nature-science-discovers-first-ever-adult-t-rex-trackway/); [DMNS research page](https://www.dmns.org/science/research/t-rex-trackway/)) 3. **The identification is by an adult-sized animal, attributed to T. rex as "the most likely trackmaker."** The team identified T. rex as most likely based on the footprints' **exceptional size, narrow three-toed shape, and the abundance of T. rex fossils locally**, with a stride of ~13 ft and an estimated walking speed of ~3.5–4.5 mph. ([LJMU press release](https://www.ljmu.ac.uk/about-us/news/articles/2026/9/8/new-insights-into-how-the-t-rex-moved)) **Important nuance (why it is not "definitely proven"):** The attribution is probabilistic. The paper and both institutions consistently say the trackmaker is *"likely"*/*"most likely"* an adult *T. rex* — not certain. The paper also notes the track surfaces are *"heavily fractured and retain little anatomical detail beyond size and number of digits,"* and the walking-speed estimate is approximate because the tracks are heavily weathered. So if the claim were worded as "definitively/conclusively proven to be T. rex," that would be overstated. As worded ("the first ever sequence of footprints made by an adult T-Rex... discovered in North Dakota"), it matches the discovery as described by the primary sources. **Note on sourcing:** I could not open the publisher's article page on tandfonline.com (it is behind a Cloudflare bot challenge), so I relied on the university repository's accepted manuscript of the same peer-reviewed article, plus the two research institutions' own releases. No news articles or aggregators were used as evidence. Primary sources cited: - https://researchonline.ljmu.ac.uk/id/eprint/29394/ (LJMU Research Online — accepted version of the *Journal of Vertebrate Paleontology* paper) - https://www.ljmu.ac.uk/about-us/news/articles/2026/9/8/new-insights-into-how-the-t-rex-moved (Liverpool John Moores University) - https://www.dmns.org/press-room/press-releases/denver-museum-of-nature-science-discovers-first-ever-adult-t-rex-trackway/ (Denver Museum of Nature & Science) - https://www.dmns.org/science/research/t-rex-trackway/ (Denver Museum of Nature & Science research page)