A dinosaur ichnofauna from the Lower Cretaceous Shinekhudag Formation, Mongolia.

Buuvei Mainbayara, Masato Fujita, Ryuji Takasaki, Khishigjav Tsogtbaatar, Zorigt Badamkhatan , Nymsambuu Odgerel and Shinobu Ishigaki

The early Cretaceous dinosaur fauna of Mongolia is poorly known, in contrast to the
extensively documented Upper Cretaceous record. Here we describe recently excavated
dinosaur trackways from the historic Saijrakh locality from the Barremian–Aptian Shinekhudag
Formation. The ichnoassemblage includes multiple trackways of large sauropods and
theropods preserved on a single bedding plane. The sauropod trackways are wide-gauge and
exhibit a unique mosaic of features: the manus prints have a distinct pollex impression (a
plesiomorphic trait), but also possesses posterior lobes suggestive of derived soft-tissue pads.
The pes prints are characterized by straight, anteriorly directed digits I–IV. The combination
of primitive and derived characters is most consistent with a basal titanosauriform trackmaker,
providing new insights into sauropod locomotor evolution. Associated theropod tracks are
large, broad (as wide as its length), and functionally tridactyl, with wide interdigital angles
(>60°). The theropod tracks confirm the presence of large predators in this ecosystem. Beyond
individual morphologies, the high density of trackways, with frequent overprinting, indicates
that the site represents a zone of repeated transit or a high-traffic corridor. The parallel
sauropod trackways may further infer that these large-bodied herbivores followed optimal
pathways to minimize locomotor costs as modern elephants do.

Ichons

Taylor and Francis

第33巻

第2号

193

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https://www.tandfonline.com/doi/full/10.1080/10420940.2026.2645024