 |
| Benggwigwishingasuchus eremicarminis Smith, Klein, Sander & Schmitz, 2024 |
Abstract
Recent studies suggest that both stem- and crown-group Archosauria encompassed high ecological diversity during their initial Triassic radiation. We describe a new pseudosuchian archosaur, Benggwigwishingasuchus eremicarminis gen. et sp. nov., from the Anisian (Middle Triassic) Fossil Hill Member of the Favret Formation (Nevada, USA), a pelagic setting in the eastern Panthalassan Ocean characterized by the presence of abundant ammonoids and large-bodied ichthyosaurs. Coupled with archosauriforms from the eastern and western Tethys Ocean, Benggwigwishingasuchus reveals that pseudosuchians were also components of Panthalassan ocean coastal settings, establishing that the group occupied these habitats globally during the Middle Triassic. However, Benggwigwishingasuchus, Qianosuchus, and Ticinosuchus (two other pseudosuchians known from marine sediments) are not recovered in a monophyletic group, demonstrating that a nearshore marine lifestyle occurred widely across Archosauriformes during this time. Benggwigwishingasuchus is recovered as part of an expanded Poposauroidea, including several taxa (e.g. Mandasuchus, Mambawakalae) from the Middle Triassic Manda Beds of Tanzania among its basally branching members. This implies a greater undiscovered diversity of poposauroids during the Early Triassic, and supports that the group, and pseudosuchians more broadly, diversified rapidly following the End-Permian mass extinction.
Class Reptilia Linnaeus, 1758
Archosauriformes
Archosauria
Pseudosuchia
Poposauroidea
 |
| Benggwigwishingasuchus eremicarminis gen. et sp. nov. Holotype skeleton (LACM-DI 158616) (a) (pelvis block mirrored for articulation); and interpretive drawing (b) |
Genus Benggwigwishingasuchus
Benggwigwishingasuchus eremicarminis gen. et sp. nov.
Holotype: LACM-DI 158616, a partially articulated skeleton, including some cranial elements but most of the axial column, girdles and limbs.
Diagnosis: Mid-sized pseudosuchian (total length: approximately 1.5 m; femur length: 17.75 cm) diagnosed by the following unique combination of characters (*indicates autapomorphy, †indicates autapomorphy inferred from phylogenetic analysis): semilunate eminence on middle of ventral ramus of prefrontal*; ventral ramus of prefrontal broadly exposed in lateral view, extensive ventrally and excludes lacrimal from orbit; supratemporal fossa well-exposed dorsally on parietal; high cervical vertebrae count (10–11); low dorsal vertebrae count (10–11)*; dorsal vertebrae with well-developed laminae and deep infradiapophyseal fossae; anterior caudal vertebrae with well-developed, spatulate ribs; anterior caudal ribs asymmetrical in dorsal view, with diagonal bevel on posterolateral edge*; weakly sinusoidal fibular shaft; metatarsal IV longer than metatarsal III†; metatarsal IV subequal in length to metatarsal II†; robust lateral plantar tubercle on ventral face of metatarsal V; dorsal osteoderms in one-to-one, mirrored alignment in dorsal aspect†; osteoderms with indentations creating an ‘hourglass’ waisting in dorsal view*; osteoderms with multiple short spikes on lateral and medial edges.
Etymology: The generic name combines ‘Benggwi Gwishinga’ from the Shoshone term for ‘catching fish’, with ‘suchus’, the Greek term for Sobek, the Egyptian crocodile-headed god. The specific epithet combines the Latin ‘erema’ and ‘carminis’, meaning ‘desert song’, and honours Elaine Kramer and Monica Shaffer, and their love of the palaeontology, museums, and opera of the southwestern USA. The binomen is intended to translate roughly as ‘Fisherman Croc's desert song’.
 |
| Middle Triassic palaeogeographic map with localities of Archosauriformes known from marine settings. |
Locality and age: Fossil Hill Member of the Favret Formation, Favret Canyon, Augusta Mountains, Pershing County, Nevada, USA. The type locality, LACM LOC 8057, is near the top of the north slope of Favret Canyon at an altitude of 1911 m. The horizon pertains to the Frechites occidentalis Zone, which is late Anisian (Middle Triassic) in age.
Nathan D. Smith, Nicole Klein, P. Martin Sander and Lars Schmitz. 2024. A New pseudosuchian from the Favret Formation of Nevada reveals that Archosauriforms occupied Coastal Regions globally during the Middle Triassic. Biol. Lett. 2020240136. DOI: doi.org/10.1098/rsbl.2024.0136
