Postosuchus, new specimen from Petrified Forest National Park (free pdf)
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Ben Creisler
May 30, 2026, 6:29:43 PM (7 days ago) May 30
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Ben Creisler
Not yet mentioned:
Adam D. Marsh, Alaska N. Schubul, Ava S. Dalton, Helen E. Burch, and Deborah E. Wagner (2026)
Postosuchus Supernova: A New Specimen of Postosuchus Cf. P. Kirkpatricki
Lithodendron 3: 101-120
doi: https://doi.org/10.69575/SBEP1712
https://petrifiedforestfieldinstitute.org/lithodendron/lithodendron/volume-3/postosuchus-supernova-a-new-specimen-of-postosuchus-cf-p-kirkpatricki/
Rauisuchid archosaurs were among the top predators of global Late Triassic terrestrial communities. Fossils of these macropredators are relatively uncommon in Upper Triassic strata of North America compared to potential prey taxa like aetosaurs or contemporary but semiaquatic predators like phytosaurs or metoposaurid amphibians. Because of this, the alpha taxonomy, life history, and ecology of North American rauisuchids and their closest paracrocodylomorph relatives are not well understood. Only three named rauisuchid taxa are known from the continent, represented by holotype specimens of Vivaron haydeni from New Mexico, Postosuchus kirkpatricki from Texas, and Postosuchus alisonae from North Carolina.
Here we report a new specimen of the genus Postosuchus from Petrified Forest National Park, represented by partial skull elements including right and left premaxillae and maxillae, the right nasal, left jugal, and other fragmentary dermatocranial elements (PEFO 55550). The bones were eroding out of the Lot’s Wife beds of the Sonsela Member (Chinle Formation) nearly 8 m up a sheer cliff. Fragments were collected as float at the base of the cliff and a ladder was used to access the fossiliferous horizon. No elements remained in situ, but approximately 300 kg of the wash sediment below the site was dry-screened, resulting in hundreds of fragments that we reassembled over more than 100 person hours. The maxillae preserve the lateral ridge that is apomorphic for the genus. PEFO 55550 is similar in size to the holotype specimen of
P. kirkpatricki (TTU-P9000) and may be of a similar ontogenetic status. An even more fragmentary rauisuchid specimen (PEFO 34044) from Petrified Forest is 18% larger than TTU-P9000, suggesting that these animals grew to bigger sizes in the Late Triassic of what is now North America. A more complete disarticulated rauisuchid skull was found at the park in 2025 and is undergoing preparation and conservation (PEFO 34576).
Free pdf:
Adam D. Marsh, Alaska N. Schubul, Ava S. Dalton, Helen E. Burch, and Deborah E. Wagner (2026)
Postosuchus Supernova: A New Specimen of Postosuchus Cf. P. Kirkpatricki
Lithodendron 3: 101-120
doi: https://doi.org/10.69575/SBEP1712
https://petrifiedforestfieldinstitute.org/lithodendron/lithodendron/volume-3/postosuchus-supernova-a-new-specimen-of-postosuchus-cf-p-kirkpatricki/
Rauisuchid archosaurs were among the top predators of global Late Triassic terrestrial communities. Fossils of these macropredators are relatively uncommon in Upper Triassic strata of North America compared to potential prey taxa like aetosaurs or contemporary but semiaquatic predators like phytosaurs or metoposaurid amphibians. Because of this, the alpha taxonomy, life history, and ecology of North American rauisuchids and their closest paracrocodylomorph relatives are not well understood. Only three named rauisuchid taxa are known from the continent, represented by holotype specimens of Vivaron haydeni from New Mexico, Postosuchus kirkpatricki from Texas, and Postosuchus alisonae from North Carolina.
Here we report a new specimen of the genus Postosuchus from Petrified Forest National Park, represented by partial skull elements including right and left premaxillae and maxillae, the right nasal, left jugal, and other fragmentary dermatocranial elements (PEFO 55550). The bones were eroding out of the Lot’s Wife beds of the Sonsela Member (Chinle Formation) nearly 8 m up a sheer cliff. Fragments were collected as float at the base of the cliff and a ladder was used to access the fossiliferous horizon. No elements remained in situ, but approximately 300 kg of the wash sediment below the site was dry-screened, resulting in hundreds of fragments that we reassembled over more than 100 person hours. The maxillae preserve the lateral ridge that is apomorphic for the genus. PEFO 55550 is similar in size to the holotype specimen of
P. kirkpatricki (TTU-P9000) and may be of a similar ontogenetic status. An even more fragmentary rauisuchid specimen (PEFO 34044) from Petrified Forest is 18% larger than TTU-P9000, suggesting that these animals grew to bigger sizes in the Late Triassic of what is now North America. A more complete disarticulated rauisuchid skull was found at the park in 2025 and is undergoing preparation and conservation (PEFO 34576).
Adam Marsh
May 30, 2026, 6:37:14 PM (7 days ago) May 30
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Thanks, Ben :)
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On May 30, 2026, at 3:29 PM, Ben Creisler <bcre...@gmail.com> wrote:
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Ben Creisler
May 30, 2026, 6:50:22 PM (7 days ago) May 30
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You're welcome! I was glad to check and see a new issue out.
Ben
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