Cretaceous dinosaur tracks from high-latitude British Columbia + sauropod dig marks from Cretaceous of Bolivia
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Ben Creisler
Jul 24, 2026, 12:58:23 PMJul 24
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Ben Creisler
New papers:
At a palaeolatitude of 58–59°N, sandstones of the upper Coniacian Marshybank Formation represent a delta that prograded into the Western Interior Seaway. Overlying delta plain deposits represent lakes, mires, floodplains, crevasse splays and anastomosed rivers. Ubiquitous root traces in delta plain sediments indicate dense vegetation. Dinosaur tracks, all isolated specimens, and preserved primarily as natural casts and transmitted undertracks, are most commonly found on the base of, and within, crevasse splay sandstones throughout the ~12 m thick delta plain succession, with additional examples in channel bar sandstones. Of a total of 19 tracks, of no more than ‘moderate’ fidelity, 11 are blunt-toed and tridactyl, up to about 45 cm wide and 35 cm long, and are tentatively assigned to the pes tracks of ornithopods. Only one track is of sufficient fidelity to justify attribution to Hadrosauropodus, whereas two subtly arcuate, ovoid structures might represent ornithopod manus tracks. Of four tridactyl tracks with narrow digits, two are assigned with confidence to a theropod, whereas two, of lower fidelity, are of possible theropod origin. Only two, low fidelity tracks with four or five blunt digits might be attributed to the pes and manus of an ankylosaurine dinosaur. Marshybank Formation sediments preserve the stumps and fronds of conifers as well as cycads, ferns and a variety of angiosperms. Dinosaur tracks (and skeletal material) are particularly rare in terrestrial rocks of Coniacian age throughout the Western Interior Seaway. The ornithopod-dominated ichnofauna of the Marshybank Formation preserves the only evidence of Coniacian dinosaurs north of south-western Montana, and contrasts markedly with the ankylosaur-dominated fauna of the underlying Cenomanian rocks of the Dunvegan Formation.
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Free pdf:
Christian A. Meyer, Jose Hugo Heymann, Edwin Chuca Ibarra, Eddy Laura Flores & Lara Sciscio (2026)
Digging Sauropods: excavation behaviour or evidence for nest building? An example from the Late Cretaceous El Molino Formation (Maragua, Bolivia)
Fossil Record 29(2): 519-532.
doi: https://doi.org/10.3897/fr.29.198794
https://fr.pensoft.net/article/198794/
The Late Cretaceous deposits of Bolivia contain a diverse record of fossil vertebrate tracks. Extensive surfaces within the El Molino Formation (Maastrichtian) preserve evidence of diverse animal behaviour. Here, we report an unusual sedimentary structure from a titanosaurid track-bearing surface at the Mullurina Mayu locality (Maragua, Dep. Chuquisaca). The structure occurs within a massive claystone bed, interpreted as an overbank deposit, based on associated sedimentary structures and overlying units (i.e., desiccation cracks, caliche-bearing marls). The structure is a bowl-shaped depression, longer than wide (4.2 × 3.2 m), deeper internal basin (maximum depth of 60 cm), with a sharp coherent rim and an irregular margin. Along the basin walls, groups of parallel linear grooves (1 cm wide, interspace ~1.8 cm, length ~30 cm) occur within semi-circular depressions, showing two dominant orientations (NE-SW and ESE-WNW). Isolate broader scratches, interpreted as claw traces, occur on the basin floor. Several hypotheses are considered for the structure’s formation, including scouring, weathering, to animal excavation, and nest construction. The absence of scour marks, tool marks, or weathering textures, combined with syn-sedimentary nature and distribution of the scratch-like traces, support a biogenic origin. The bundled grooves are interpreted as possible skin-slip striations produced by repeated foot movement in the soft sediment during excavation. Given the close association with titanosaurid trackways, we tentatively consider this as evidence of their digging and possible abandoned nest scrape.
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A. Guy Plint & Charles W. Helm (2026)
An upper Coniacian (Upper Cretaceous) dinosaur track record from a high-latitude delta plain setting, north-east British Columbia, Canada
Historical Biology (advance online publication)
doi: https://doi.org/10.1080/08912963.2026.
https://www.tandfonline.com/doi/full/10.1080/08912963.2026.2683023
An upper Coniacian (Upper Cretaceous) dinosaur track record from a high-latitude delta plain setting, north-east British Columbia, Canada
Historical Biology (advance online publication)
doi: https://doi.org/10.1080/08912963.2026.
https://www.tandfonline.com/doi/full/10.1080/08912963.2026.2683023
At a palaeolatitude of 58–59°N, sandstones of the upper Coniacian Marshybank Formation represent a delta that prograded into the Western Interior Seaway. Overlying delta plain deposits represent lakes, mires, floodplains, crevasse splays and anastomosed rivers. Ubiquitous root traces in delta plain sediments indicate dense vegetation. Dinosaur tracks, all isolated specimens, and preserved primarily as natural casts and transmitted undertracks, are most commonly found on the base of, and within, crevasse splay sandstones throughout the ~12 m thick delta plain succession, with additional examples in channel bar sandstones. Of a total of 19 tracks, of no more than ‘moderate’ fidelity, 11 are blunt-toed and tridactyl, up to about 45 cm wide and 35 cm long, and are tentatively assigned to the pes tracks of ornithopods. Only one track is of sufficient fidelity to justify attribution to Hadrosauropodus, whereas two subtly arcuate, ovoid structures might represent ornithopod manus tracks. Of four tridactyl tracks with narrow digits, two are assigned with confidence to a theropod, whereas two, of lower fidelity, are of possible theropod origin. Only two, low fidelity tracks with four or five blunt digits might be attributed to the pes and manus of an ankylosaurine dinosaur. Marshybank Formation sediments preserve the stumps and fronds of conifers as well as cycads, ferns and a variety of angiosperms. Dinosaur tracks (and skeletal material) are particularly rare in terrestrial rocks of Coniacian age throughout the Western Interior Seaway. The ornithopod-dominated ichnofauna of the Marshybank Formation preserves the only evidence of Coniacian dinosaurs north of south-western Montana, and contrasts markedly with the ankylosaur-dominated fauna of the underlying Cenomanian rocks of the Dunvegan Formation.
=====
Free pdf:
Christian A. Meyer, Jose Hugo Heymann, Edwin Chuca Ibarra, Eddy Laura Flores & Lara Sciscio (2026)
Digging Sauropods: excavation behaviour or evidence for nest building? An example from the Late Cretaceous El Molino Formation (Maragua, Bolivia)
Fossil Record 29(2): 519-532.
doi: https://doi.org/10.3897/fr.29.198794
https://fr.pensoft.net/article/198794/
The Late Cretaceous deposits of Bolivia contain a diverse record of fossil vertebrate tracks. Extensive surfaces within the El Molino Formation (Maastrichtian) preserve evidence of diverse animal behaviour. Here, we report an unusual sedimentary structure from a titanosaurid track-bearing surface at the Mullurina Mayu locality (Maragua, Dep. Chuquisaca). The structure occurs within a massive claystone bed, interpreted as an overbank deposit, based on associated sedimentary structures and overlying units (i.e., desiccation cracks, caliche-bearing marls). The structure is a bowl-shaped depression, longer than wide (4.2 × 3.2 m), deeper internal basin (maximum depth of 60 cm), with a sharp coherent rim and an irregular margin. Along the basin walls, groups of parallel linear grooves (1 cm wide, interspace ~1.8 cm, length ~30 cm) occur within semi-circular depressions, showing two dominant orientations (NE-SW and ESE-WNW). Isolate broader scratches, interpreted as claw traces, occur on the basin floor. Several hypotheses are considered for the structure’s formation, including scouring, weathering, to animal excavation, and nest construction. The absence of scour marks, tool marks, or weathering textures, combined with syn-sedimentary nature and distribution of the scratch-like traces, support a biogenic origin. The bundled grooves are interpreted as possible skin-slip striations produced by repeated foot movement in the soft sediment during excavation. Given the close association with titanosaurid trackways, we tentatively consider this as evidence of their digging and possible abandoned nest scrape.
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