Sauropod tracks from Lower Cretaceous of China + crocodyliform egg clusters from Late Cretaceous of Brazil + ichthyosaur partial skeleton from Cuba

[Ben Creisler]

Ben Creisler

bcre...@gmail.com

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Qing Yang, Lida Xing, Jens N. Lallensack, Lin Liu, Qiyan Chen, Anthony Romilio, Qi Qi, Juan Qi, Ming Zhao, Xi Chen, Ya Zhao, Lixin Wei & Yang Wan (2026)
A new sauropod tracksite from the Lower Cretaceous of Ningxia, Northwestern China, with implications for overtrack preservation
Scientific Reports (unedited preprint)
https://doi.org/10.1038/s41598-026-37987-w
https://www.nature.com/articles/s41598-026-37987-w


We are providing an unedited version of this manuscript to give early access to its findings. Before final publication, the manuscript will undergo further editing. Please note there may be errors present which affect the content, and all legal disclaimers apply.

Abstract

Dinosaur fossils in the Early Cretaceous Madongshan Formation (Ningxia, northwestern China) are scarce, but fossil tracks have recently been reported. We describe a new sauropod tracksite, the Beilianchi tracksite, which is the largest tracksite known from the formation. The site consists of a steeply inclined surface approximately 650 m2 in area that, although mostly inaccessible, is documented and studied using photogrammetry. Nine medium to large-sized sauropod trackways (pes lengths ranging from 58.3 to 143.5 cm), as well as numerous isolated tracks, were identified at the site. The tracks are preserved in laminated silty mudstones; layers deposited after track formation are filling many of the tracks as overtracks but are mostly eroded outside of the tracks. The site preserves evidence of probably a single tracking surface and at least two distinct track-forming intervals, suggesting a time-averaged assemblage. Characteristic features of these trackways include (1) narrow/medium to wide gauge, (2) outward rotation of both manus and pes impressions, (3) oval to subtriangular pes morphologies, and (4) semicircular manus impressions. The Beilianchi tracks are intermediate in morphology between typical Brontopodus and Parabrontopodus tracks. Our understanding of the distribution and size spectrum of Early Cretaceous sauropods in northwestern China is advanced by this discovery.

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Giovanna M. X. Paixão, Agustín G. Martinelli, Júlio C. A. Marsola, E. Martín Hechenleitner, William R. Nava, Luis M. Chiappe, Eduardo I. Jussiani, Sebastian Rozadilla, Jonatan Kaluza & Felipe L. Pinheiro (2026)

Fossil evidence of exceptionally large egg-clutches sheds light on reproductive diversity in Late Cretaceous crocodyliforms from Brazil
Journal of Vertebrate Paleontology e2596997
doi: https://doi.org/10.1080/02724634.2025.2596997
https://www.tandfonline.com/doi/full/10.1080/02724634.2025.2596997


The Upper Cretaceous units of the Bauru Group have provided a comprehensive fossil record of eggs and nests belonging to different reptilian clades, such as turtles, crocodyliforms, and dinosaurs. Here, we report the discovery of several egg-clutches from the Adamantina Formation (Bauru Group), cropping out in the city of Presidente Prudente (São Paulo State, Brazil). The new discovery represents three egg clutches, totaling 83 eggs, plus numerous isolated eggshells. The spatial arrangement of the eggs within the clutches is like that observed in different species of extant crocodyliforms, an arrangement that results from the construction of a relatively narrow hole within a substrate mixed with leaf litter. An important feature of one of the clutches (MPM 447) is that it contains a large number of eggs (at least 47), thus representing the largest Mesozoic crocodyliform egg clutch ever found. SEM images of the external surface revealed a high pore density, suggesting that thicker and more porous eggs facilitate water loss, compensating for deposition in more humid settings. The set of attributes converges with structures described for crocodyliforms. In connection with studies conducted on the Bauru Group, the correlation with Notosuchia elucidates broader aspects of the adaptation of this clade, which includes organisms specialized in both terrestrial environments and more humid habitats. The new discovery shows new evolutionary implications for one of the world's most diverse fossil crocodylomorph faunas, revealing more complex and successful reproductive habits with potential adaptations to occasionally wetter environments.


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Manuel Iturralde-Vinent, Lisandro Campos, Andrzej Pszczółkowski, Yasmani Ceballos-Izquierdo & Lázaro W. Viñola-Lopez (2026)
A partial ichthyosaur (?Ophthalmosauridae) skeleton from the Tithonian (Upper Jurassic) of western Cuba
Journal of Vertebrate Paleontology e2609717
doi: https://doi.org/10.1080/02724634.2025.2609717
https://www.tandfonline.com/doi/full/10.1080/02724634.2025.2609717


Here we report the discovery of the first partially articulated ichthyosaur skeleton from the insular Caribbean. The specimen is embedded in a limestone slab that is exposed in the ceiling of a fluvial cave in El Cuajaní, within the Viñales Geopark and National Park in western Cuba. The study of the microfossil assemblages from the fossil-bearing slab indicates that the section where the specimen is embedded belongs to the Upper Tithonian El Americano Member of the Guasasa Formation. The exposed segment of the skeleton includes the U-shaped curved vertebral column with associated ribs, isolated vertebrae, and a single hindlimb. The hindlimb morphology is comparable to that of Tithonian platypterygiine ophthalmosaurids, resembling Caypullisaurus bonapartei and Aegirosaurus leptospondylus. This fossil represents the most complete ichthyosaur recovered from Cuba to date and extends the temporal record of ichthyosaurs on the island, which previously only included specimens from the Oxfordian.

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