Roundup on Thunderstorm Ridge: keeping up with Petrified Forest NP

Last week's publication of the stem-caecilian Funcusvermis reminded me that I really ought to show off Petrified Forest National Park (PEFO) more often. Since the last spotlight, on the "biloph" trilophosaur Trilophosaurus phasmalophus in spring 2020, four more species of Triassic vertebrates have been described from fossils found in the park, to go along with a bushel of reports on anatomy, identifications of rare forms, vertebrate trace fossils, stratigraphy and geochronology, and other topics, to say nothing of conference abstracts and papers that mention PEFO fossils in wider contexts. (SVP conferences are usually good for a handful of PEFO topics.) Because we're talking the Late Triassic, the taxonomic diversity is wide. There's a little bit of almost everything.*

*Interestingly enough, that includes Paleozoic marine invertebrates: reworked fossiliferous cobbles of the Permian Kaibab Formation have been found in the park's Chinle Formation outcrops, particularly the Sonsela Member. There are also limited Neogene deposits with Hemphillian vertebrates.

Classically, as with most places that have produced vertebrate fossils for more than a century, big singular fossils were long the focus (e.g., skulls of phytosaurs). Although there is still interest in those kinds of fossils, increasingly study has focused on bonebeds and microvertebrates, with much more care given to stratigraphic placement. It turns out that PEFO holds a whole weird and wonderful landscape of everything that gave it a go in the Late Triassic, before a couple of groups of archosaurs took over land management for the rest of the Mesozoic. (And if you don't like vertebrates, the plants are just about as wild in their own way, and there are freshwater and terrestrial invertebrates as well.) It practically begs for a book like those on Florissant, Fossil Lake, the Morrison, and the White River Badlands.

Here's a strat column to help keep the geologic units straight, borrowed from the park website.

With all of that in mind, here are a few quick hits from the past few years of research at PEFO:

Trilophosaurus and Ophthalmothule

For this post, we highlight two extinct reptiles that have been the subjects of publications in the past few days. Other than that, they don't have much in common. One is a short-necked terrestrial herbivore less than three meters long that lived during the Late Triassic in what is now Arizona, the other is a long-necked marine carnivore between five and six meters long that lived at about the Jurassic–Cretaceous boundary at what is now an Arctic island (not quite so arctic at the time).