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Giant Bird Tracks (Family Gastornithidae) from the Paleogene Chuckanut Formation, Northwest Washington, USA, with a Review of Gastornis Distribution

by George E. Mustoe

Foss. Stud. 2025, 3(1), 4; https://doi.org/10.3390/fossils3010004 - 27 Feb 2025

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Abstract

Giant Paleogene groundbirds named Gastornis have long been known from Europe, with similar fossils from North America being placed in the genus Diatryma. A more recent discovery in China is evidence that these birds had wide geographic distribution. The name Gastornis is now generally considered to be the name that has historical precedence. Historically, Gastornis has been interpreted as being a fierce predator, but anatomical and isotopic evidence suggests that the giant birds were herbivores. Gastornithid tracks preserved in Lower Eocene fluvial sediments of the Chuckanut Formation in northwest Washington State, USA, support the herbivore interpretation. These tridactyl footprints preserve broad triangular toenails rather than talons. The Chuckanut Formation gastornithid tracks have been given the ichnotaxonomic name Rivavipes giganteus Mustoe et al. (2012). In 2024, two important new discoveries were made. These are a trackway that preserves three adult tracks, and two tracks left by a gastornithid chick.The adult bird trackway has stride and pace distances that are consistent with the short lower limb bones (tarsometatarsals) observed in Gastornis skeletal remains. The reproductive strategies of gastornithids remain enigmatic; the evidence consists of numerous egg shell fragments found at sites in France and the newly discovered Chuckanut tracks. Full article

(This article belongs to the Special Issue Advances in Palaeontology—Feature Papers to Celebrate the Inaugural Issue of Fossil Studies)

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15 pages, 13196 KB

Open AccessArticle

The First Discovery of a Fish Fossil (Phareodus sp.) from Paleogene Fluvial Deposits in Western Washington State, USA

by George E. Mustoe

Geosciences 2023, 13(9), 255; https://doi.org/10.3390/geosciences13090255 - 23 Aug 2023

Cited by 1 | Viewed by 3703

Abstract

The 2023 discovery of a fish fossil from lower Eocene strata of the Chuckanut Formation provides new insights into the paleoenvironment and paleoecology of one of the region’s most prolific fossil deposits. The detrital clastic fluvial and floodplain deposits of the Chuckanut Formation are not favorable for the preservation of fish, but the high quality of preservation of this specimen is evidence that some Chuckanut Formation sediments provide suitable depositional conditions for the preservation of skeletal remains. This information improves our understanding of the range of depositional environments within the Chuckanut Formation, and provides clues for searching for additional specimens. The discovery of this fossil has larger significance; the skeletal remains of fish are scarce in fluvial and floodplain deposits. Despite its incompleteness, dorsal fin and caudal fin ray anatomy suggest that the specimens represent the extinct genus Phareodus, an open-water carnivore that has previously only been reported in North America from the Green River and Bridger Formations in Wyoming and Utah, USA. Full article

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19 pages, 12834 KB

Open AccessArticle

Lower Eocene Footprints from Northwest Washington, USA. Part 1: Reptile Tracks

by George E. Mustoe

Geosciences 2019, 9(7), 321; https://doi.org/10.3390/geosciences9070321 - 22 Jul 2019

Cited by 22 | Viewed by 8192

Abstract

Lower Eocene fluvial strata in the Chuckanut Formation preserve abundant bird and mammal tracks. Reptile trace fossils include footprints from a small turtle (ichnogenus Chelonipus), and several Crocodylian trackways that consist of irregularly spaced footprints associated with linear tail drag marks. The latter trackways represent “punting” locomotion, where a submerged Crocodylian used intermittent substrate contacts to provide forward motion of their neutrally buoyant bodies. Two adjacent sandstone blocks preserve Crocodylian trace fossils that are named herein as a new ichnogenus and ichnospecies Anticusuchipes amnis. Two other Crocodylian trackways lack sufficient detail for ichnotaxonomic assignment. Full article

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