Penetrative theropod tracks as dubious ichnospecies + basal sauropodomorph tracks from Late Triassic of China
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Ben Creisler
Jan 13, 2026, 2:49:07 PM (5 days ago) Jan 13
to DinosaurMa...@googlegroups.com
Ben Creisler
New papers:
Jens N. Lallensack, Félix Pérez-Lorente, Mustapha Amzil, Mostafa Oukassou, Christian Meyer, Hafid Saber, Hendrik Klein, André Charriére, Omar Zafaty & Peter L. Falkingham (2026)
The abundance and diversity of penetrative tracks: a critical re-evaluation of theropod ichnotaxa
Historical Biology (advance online publication)
doi: https://doi.org/10.1080/08912963.2025.2610322
https://www.tandfonline.com/doi/full/10.1080/08912963.2025.2610322
Tetrapod ichnotaxonomy aims to classify tracks based on features that reflect trackmaker anatomy. Consequently, distinct ichnotaxa are assumed to represent distinct (though often unidentified) biological taxa. However, track shape is not only determined by trackmaker anatomy, but also by the properties of the substrate, the movements of the foot, the level of exposure, and any post-formational alteration. Because of these multiple sources of variation, determining if, and to what degree, a particular feature conveys anatomical information remains a major challenge. A major source of confusion has been penetrative tracks, which form when the foot sinks deeply into soft sediment, causing sediment to flow around the foot to seal its path. Penetrative tracks of long-toed, tridactyl trackmakers often show conspicuous features that appear to reflect foot anatomy but do in fact reflect the penetrative nature of the tracks. We studied dozens of tracksites in the Middle Jurassic of El Mers, Morocco and the Early Cretaceous Cameros Basin, Spain, showing that penetrative tracks are much more diverse and common than previously thought. We discuss formational mechanisms that explain the variation of several features commonly used to define ichnotaxa. We conclude that the type ichnospecies of Saurexallopus, Magnoavipes, Theroplantigrada, Ordexallopus, and Archaeornithipus are probably based on penetrative tracks and therefore nomina dubia.
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The abundance and diversity of penetrative tracks: a critical re-evaluation of theropod ichnotaxa
Historical Biology (advance online publication)
doi: https://doi.org/10.1080/08912963.2025.2610322
https://www.tandfonline.com/doi/full/10.1080/08912963.2025.2610322
Tetrapod ichnotaxonomy aims to classify tracks based on features that reflect trackmaker anatomy. Consequently, distinct ichnotaxa are assumed to represent distinct (though often unidentified) biological taxa. However, track shape is not only determined by trackmaker anatomy, but also by the properties of the substrate, the movements of the foot, the level of exposure, and any post-formational alteration. Because of these multiple sources of variation, determining if, and to what degree, a particular feature conveys anatomical information remains a major challenge. A major source of confusion has been penetrative tracks, which form when the foot sinks deeply into soft sediment, causing sediment to flow around the foot to seal its path. Penetrative tracks of long-toed, tridactyl trackmakers often show conspicuous features that appear to reflect foot anatomy but do in fact reflect the penetrative nature of the tracks. We studied dozens of tracksites in the Middle Jurassic of El Mers, Morocco and the Early Cretaceous Cameros Basin, Spain, showing that penetrative tracks are much more diverse and common than previously thought. We discuss formational mechanisms that explain the variation of several features commonly used to define ichnotaxa. We conclude that the type ichnospecies of Saurexallopus, Magnoavipes, Theroplantigrada, Ordexallopus, and Archaeornithipus are probably based on penetrative tracks and therefore nomina dubia.
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Lida Xing, Lin Liu, Tingshan Zhang, Jens N. Lallensack, Mihai Emilian Popa, Jianli Zeng, Hendrik Klein, Guanzhao Peng, Yong Ye, Yu Liu, Xin Shen & Qiyan Chen (2026)
Tracks of a large archosaur from the Late Triassic Xujiahe Formation in Guangyuan, Sichuan, China
Historical Biology (advance online publication)
doi: https://doi.org/10.1080/08912963.2025.2605163
https://www.tandfonline.com/doi/full/10.1080/08912963.2025.2605163
Late Triassic dinosaur skeletal records are missing in China, with only sparse dinosaur track occurrences documented in the southwestern and central regions. The Xujiahe Formation, situated along the northern margin of the Sichuan Basin, provides critical insights into the palaeoecosystems and sedimentary conditions of the region. A newly discovered Zilanba track site from the Fifth Member of the Xujiahe Formation near Guangyuan City, Sichuan Province, recorded ten tetrapod tracks. These small-sized tracks (majority of pes ranging 25–50 cm in length) comprise one trackway and four isolated tracks. Characterised by a medium gauge and possibly a low heteropody ratio (1: 2.3), although showing similarities with archosaurian tracks, they are tentatively attributed to basal sauropodomorphs. This site represents the ninth documented Triassic tetrapod track site in China and the third basal sauropodomorph track site of this period. This discovery enhances our understanding of the quantity and distribution of basal sauropodomorphs in Late Triassic of China. Furthermore, the Zilanba tracks provide new evidence supporting the previously proposed hypothesis of potential migration routes for basal sauropodomorphs from the western to the eastern Tethyan domain during this period.
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Tracks of a large archosaur from the Late Triassic Xujiahe Formation in Guangyuan, Sichuan, China
Historical Biology (advance online publication)
doi: https://doi.org/10.1080/08912963.2025.2605163
https://www.tandfonline.com/doi/full/10.1080/08912963.2025.2605163
Late Triassic dinosaur skeletal records are missing in China, with only sparse dinosaur track occurrences documented in the southwestern and central regions. The Xujiahe Formation, situated along the northern margin of the Sichuan Basin, provides critical insights into the palaeoecosystems and sedimentary conditions of the region. A newly discovered Zilanba track site from the Fifth Member of the Xujiahe Formation near Guangyuan City, Sichuan Province, recorded ten tetrapod tracks. These small-sized tracks (majority of pes ranging 25–50 cm in length) comprise one trackway and four isolated tracks. Characterised by a medium gauge and possibly a low heteropody ratio (1: 2.3), although showing similarities with archosaurian tracks, they are tentatively attributed to basal sauropodomorphs. This site represents the ninth documented Triassic tetrapod track site in China and the third basal sauropodomorph track site of this period. This discovery enhances our understanding of the quantity and distribution of basal sauropodomorphs in Late Triassic of China. Furthermore, the Zilanba tracks provide new evidence supporting the previously proposed hypothesis of potential migration routes for basal sauropodomorphs from the western to the eastern Tethyan domain during this period.
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