Taphonomic characteristics of an Upper Cretaceous dinosaur fossil-rich layer along the west bank of the Erlian Salt Lake, Inner Mongolia, and their paleoecological implications
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Abstract:
Outcrops of the Upper Cretaceous Iren Dabasu Formation along the west bank of the Erlian Salt Lake have yielded abundant disarticulated dinosaur fossils that display taphonomic features characteristic of a hydraulically accumulated lag deposit. This discovery is significant for reconstructing the composition of the assemblage and the taphonomic and sedimentary history of the dinosaur community found in this area. Based on skeletal measurements and taphonomic data collected from the fossil-rich layer during fieldwork conducted in 2014 and 2015, more than 50% of the specimens from the bonebed are attributed to the early-branching hadrosauroid Bactrosaurus johnsoni, suggesting herding behavior of this species in life. Following catastrophic mass mortality events, the dinosaur community was strongly affected by the carcass decomposition, mechanical bone breakage, and physical weathering, ultimately resulting in a vertebrate bonebed mono-dominated by Bactrosaurus. Paleocurrent orientations are random and variable, reflecting a relatively chaotic process of hydraulic transportation of bones. Hydraulic sorting played only a minor role in bone transportation and burial. The age profile of the Bactrosaurus population is dominated by nestling and juvenile individuals, strongly indicating an attritional mortality pattern and suggesting population segregation between hadrosauroid juveniles and adults.
