A giant phytosaur (Reptilia: Archosauria) skull from the Redonda Formation (Upper Triassic: Apachean) of east-central New Mexico
— Andrew B. Heckert, Spencer G. Lucas, Adrian P. Hunt, and Jerald D. Harris


In the Summer of 1994, a field party of the New Mexico Museum of Natural History and Science (NMMNH) collected a giant, incomplete phytosaur skull from a bonebed discovered by Paul Sealey in east-central New Mexico. This bonebed lies in a narrow channel deposit of intraformational conglomerate in the Redonda Formation. Stratigraphically, this specimen comes from strata identical to the type Apachean land -vertebrate faunachron and thus of Apachean (latest Triassic: late Norian-Rhaetian) age. The skull lacks most of the snout but is otherwise complete and in excellent condition. As preserved, the skull measures 780 mm long, and was probably 1200 mm or longer in life, making it nearly as large as the holotype of Rutiodon (= Machaeroprosopus,= Smilosuchus) gregorii, and one of the largest published phytosaur skulls. The diagnostic features of Redondasaurus present in the skull include robust squamosal bars extending posteriorly well beyond the occiput and supratemporal fenestrae that are completely concealed in dorsal view.

The specimen was originally encased in a plaster jacket only marginally larger than the preserved skull. Still, the contents of the jacket reveal one of the densest accumulations of disarticulated bones in the Chinle Group, including a total of 275 other teeth, bones, and bone fragments, including a smaller phytosaur skull. The smaller skull is poorly ossified, distorted, and slightly disarticulated due to lack of fusion. We suspect that this specimen represents a subadult Redondasaurus, but it lacks the temporal region and is thus not identifiable at the genus level. Aetosaur scutes associated with the phytosaurs may represent the first record of Neoaetosauroides in North America and suggest correlation of the Apachean Redonda Formation with the Los Colorados Formation of Argentina.

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Recommended Citation:

  1. Heckert, Andrew B.; Lucas, Spencer G.; Hunt, Adrian P.; Harris, Jerald D., 2001, A giant phytosaur (Reptilia: Archosauria) skull from the Redonda Formation (Upper Triassic: Apachean) of east-central New Mexico, in: Geology of the Llano Estacado, Lucas, Spencer G.; Ulmer-Scholle, Dana S., New Mexico Geological Society, Guidebook, 52nd Field Conference, pp. 169-176. https://doi.org/10.56577/FFC-52.169

[see guidebook]