Upper Jurassic Morrison Formation new paleontology + Morrison Formation trace fossils (free pdfs)
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Ben Creisler
Jan 22, 2026, 6:33:50 PM (11 days ago) Jan 22
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Ben Creisler
Adrian P. Hunt, Spencer G. Lucas and John R. Foster (2026)
The ichnological record of vertebrate consumption from the Upper Jurassic Morrison Formation of western North America with description of a new dentalite and revision of the ichnogenus Machichnus
In: Foster et al., 2026, New Developments in the Paleontology and Geology of the Upper Jurassic Morrison Formation. New Mexico Museum of Natural History and Science Bulletin 102: 359-373
https://www.researchgate.net/publication/399959000_CONFUSION_CONTRADICTION_CONSENSUS_AND_CONTROVERSY-MIDDLE-UPPER_JURASSIC_STRATIGRAPHY_ON_THE_SOUTHERN_COLORADO_PLATEAU
The Upper Jurassic Morrison Formation is famous for its vertebrate fauna, notably dinosaurs, but it yields a relatively depauperate vertebrate ichnofauna, except for tracks. The track ichnofauna is quite extensive, but traces related to consumption are uncommon. Dentalites are known from several Morrison sauropods but only from a few theropods and other non-sauropod herbivorous dinosaurs. We restrict the dentalite ichnogenus Machichnus to include only the ichnospecies M. regularis, M. multilineatus and Machichnus inrosus, which represent rodent gnawing. Morsichnus igen. nov. is introduced to include the raking traces Morsichnus (Machichnus) bohemicus, Morsichnus (Machichnus) fatimae and Morsichnus (Machichnus) dimorphodon. Morsichnus deinodentatus igen. et isp. nov. represents the traces of the biting of large theropods. We coin the term Seeker Effect (Seeker Fieldwork Effect, Seeker Collections Effect) to recognize the importance in the fossil record of fossils being found when sought. Recent work suggests that the Seeker Collection Effect may reveal many more Morrison dentalites when existing collections are re-examined, and the same is true for molalites. Regurgitalites, consumulites and coprolites are very uncommon due to taphonomic megabiases. Pabulites and digestilites are recent concepts that have not been applied to the Morrison Formation trace-fossil record. Micturalites are absent or rare in the Morrison Formation, as they are elsewhere. Claims of Morrison dinosaur gastroliths are largely based on polished siliceous clasts that lack a skeletal association, so these are doubtful records of gastroliths. Theropod tracks from two large dinosaur quarries (Howe Quarry, Something Interesting Quarry) may represent scavenging by carnivores.
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New papers (likely more to come posted as free pdfs in Research Gate...):
Free pdf:
John R. Foster, Kelli C. Trujillo, Rebecca K. Hunt-Foster, Spencer G. Lucas, Kenneth Carpenter, and Brent H. Breithaupt (2026)
An introduction to new developments in the geology and paleontology of the Upper Jurassic Morrison Formation
In: Foster et al., 2026, New Developments in the Paleontology and Geology of the Upper Jurassic Morrison Formation. New Mexico Museum of Natural History and Science Bulletin 102: 1-14
https://www.researchgate.net/publication/399958698_AN_INTRODUCTION_TO_NEW_DEVELOPMENTS_IN_THE_GEOLOGY_AND_PALEONTOLOGY_OF_THE_UPPER_JURASSIC_MORRISON_FORMATION
An introduction to new developments in the geology and paleontology of the Upper Jurassic Morrison Formation
In: Foster et al., 2026, New Developments in the Paleontology and Geology of the Upper Jurassic Morrison Formation. New Mexico Museum of Natural History and Science Bulletin 102: 1-14
https://www.researchgate.net/publication/399958698_AN_INTRODUCTION_TO_NEW_DEVELOPMENTS_IN_THE_GEOLOGY_AND_PALEONTOLOGY_OF_THE_UPPER_JURASSIC_MORRISON_FORMATION
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Free pdf:
Spencer G. Lucas (2026)
Confusion, contradiction, consensus and controversy-Middle-Upper Jurassic stratigraphy on the Southern Colorado Plateau
In: Foster et al., 2026, New Developments in the Paleontology and Geology of the Upper Jurassic Morrison Formation. New Mexico Museum of Natural History and Science Bulletin 102: 73-93
https://www.researchgate.net/publication/399959000_CONFUSION_CONTRADICTION_CONSENSUS_AND_CONTROVERSY-MIDDLE-UPPER_JURASSIC_STRATIGRAPHY_ON_THE_SOUTHERN_COLORADO_PLATEAU
Middle-Upper Jurassic strata on the southern Colorado Plateau assigned to the San Rafael Group and overlying Morrison Formation have been studied for nearly 175 years. Early studies resulted in much confusion and uncertainty about the identification and correlation of the Jurassic stratigraphic units. The monograph by Baker, Dane and Reeside published by the U. S. Geological Survey in 1936 was a turning point in understanding that both resolved some of the confusion and produced more. It began a period of contradiction that culminated in a consensus in the 1950s, which was the Jurassic stratigraphy advocated by the U. S. Geological Survey. In the 1980s-1990s research by Anderson and Lucas called into question much of that consensus and thus began a wide-ranging controversy, particularly about the overall stratigraphic architecture, correlation and relationship to regional unconformities of the Middle-Upper Jurassic strata. These controversies have not been fully resolved. Recent publications have introduced new understanding and new problems, particularly with regard to lithostratigraphy, unconformities, sequence stratigraphy, distributive fluvial systems and magnetostratigraphy.
=====
Confusion, contradiction, consensus and controversy-Middle-Upper Jurassic stratigraphy on the Southern Colorado Plateau
In: Foster et al., 2026, New Developments in the Paleontology and Geology of the Upper Jurassic Morrison Formation. New Mexico Museum of Natural History and Science Bulletin 102: 73-93
https://www.researchgate.net/publication/399959000_CONFUSION_CONTRADICTION_CONSENSUS_AND_CONTROVERSY-MIDDLE-UPPER_JURASSIC_STRATIGRAPHY_ON_THE_SOUTHERN_COLORADO_PLATEAU
Middle-Upper Jurassic strata on the southern Colorado Plateau assigned to the San Rafael Group and overlying Morrison Formation have been studied for nearly 175 years. Early studies resulted in much confusion and uncertainty about the identification and correlation of the Jurassic stratigraphic units. The monograph by Baker, Dane and Reeside published by the U. S. Geological Survey in 1936 was a turning point in understanding that both resolved some of the confusion and produced more. It began a period of contradiction that culminated in a consensus in the 1950s, which was the Jurassic stratigraphy advocated by the U. S. Geological Survey. In the 1980s-1990s research by Anderson and Lucas called into question much of that consensus and thus began a wide-ranging controversy, particularly about the overall stratigraphic architecture, correlation and relationship to regional unconformities of the Middle-Upper Jurassic strata. These controversies have not been fully resolved. Recent publications have introduced new understanding and new problems, particularly with regard to lithostratigraphy, unconformities, sequence stratigraphy, distributive fluvial systems and magnetostratigraphy.
=====
Free pdf:
Adrian P. Hunt, Spencer G. Lucas and John R. Foster (2026)
The ichnological record of vertebrate consumption from the Upper Jurassic Morrison Formation of western North America with description of a new dentalite and revision of the ichnogenus Machichnus
In: Foster et al., 2026, New Developments in the Paleontology and Geology of the Upper Jurassic Morrison Formation. New Mexico Museum of Natural History and Science Bulletin 102: 359-373
https://www.researchgate.net/publication/399959000_CONFUSION_CONTRADICTION_CONSENSUS_AND_CONTROVERSY-MIDDLE-UPPER_JURASSIC_STRATIGRAPHY_ON_THE_SOUTHERN_COLORADO_PLATEAU
The Upper Jurassic Morrison Formation is famous for its vertebrate fauna, notably dinosaurs, but it yields a relatively depauperate vertebrate ichnofauna, except for tracks. The track ichnofauna is quite extensive, but traces related to consumption are uncommon. Dentalites are known from several Morrison sauropods but only from a few theropods and other non-sauropod herbivorous dinosaurs. We restrict the dentalite ichnogenus Machichnus to include only the ichnospecies M. regularis, M. multilineatus and Machichnus inrosus, which represent rodent gnawing. Morsichnus igen. nov. is introduced to include the raking traces Morsichnus (Machichnus) bohemicus, Morsichnus (Machichnus) fatimae and Morsichnus (Machichnus) dimorphodon. Morsichnus deinodentatus igen. et isp. nov. represents the traces of the biting of large theropods. We coin the term Seeker Effect (Seeker Fieldwork Effect, Seeker Collections Effect) to recognize the importance in the fossil record of fossils being found when sought. Recent work suggests that the Seeker Collection Effect may reveal many more Morrison dentalites when existing collections are re-examined, and the same is true for molalites. Regurgitalites, consumulites and coprolites are very uncommon due to taphonomic megabiases. Pabulites and digestilites are recent concepts that have not been applied to the Morrison Formation trace-fossil record. Micturalites are absent or rare in the Morrison Formation, as they are elsewhere. Claims of Morrison dinosaur gastroliths are largely based on polished siliceous clasts that lack a skeletal association, so these are doubtful records of gastroliths. Theropod tracks from two large dinosaur quarries (Howe Quarry, Something Interesting Quarry) may represent scavenging by carnivores.
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Jerry Harris
Jan 23, 2026, 11:02:00 AM (10 days ago) Jan 23
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Another one from this volume:
Foster, J.R., Woodruff, C., and Royo-Torres, R. (2026)
The first evidence of Turiasauria (Sauropod) in the Upper Jurassic Morrison Formation
Casts made from teeth discovered in the Brushy Basin Member (Kimmeridgian) of the Morrison Formation in northwestern Colorado, which possess heart-shaped tooth crowns in the labial and lingual profiles with their apex compressed labiolingually, indicate the presence of the first reported member of Turiasauria from the Late Jurassic of North America. This suggests that the group dispersed to North America prior to the Early Cretaceous and that the group might have survived the Jurassic-Cretaceous boundary in the region.
Virginia Tidwell
Jan 23, 2026, 1:50:28 PM (10 days ago) Jan 23
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Can anyone tell me where to purchase this NMMNH volume since the museum itself is temporarily closed?
Virginia Tidwell
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Mickey Mortimer
Jan 23, 2026, 7:08:01 PM (10 days ago) Jan 23
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Looks to be lots of interesting papers in this volume- "Hullinger et al. (2026) redescribe an apatosaur specimen from very high in the Morrison Formation in Arches National Park. Woodruff et al. (2026) report the first Barosaurus specimen from Montana. Carpenter et al. (2026) describe the postcrania of young Camarasaurus from Dinosaur National Monument."
"Carpenter (2026) describes a very small stegosaur from Wyoming, and Hunt-Foster et al. (2026) describe a very large stegosaur specimen from northeastern Utah."
"Carpenter (2026) describes a very small stegosaur from Wyoming, and Hunt-Foster et al. (2026) describe a very large stegosaur specimen from northeastern Utah."
"Galton and Carpenter (2026) redescribe Camptosaurus dispar, and Krumenacker et al. (2026) describe several enigmatic ornithopod specimens."
Mickey Mortimer
Mickey Mortimer
Jan 23, 2026, 9:28:35 PM (10 days ago) Jan 23
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The Camarasaurus, juvenile Stegosaurus and Camptosaurus ones are all on ResearchGate btw.
Mickey Mortimer
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