Abstract
Here, we provide a detailed taxonomic reassessment of a historically collected chondrichthyan dental assemblage from the lower Kimmeridgian of Czarnogłowy in north-western Poland and discuss its significance for better understanding hybodontiform diversity patterns prior to their post-Jurassic decline in fully marine environments. In spite of its low taxonomic diversity, consisting of four large-toothed taxa (viz., Strophodus udulfensis, Asteracanthus ornatissimus, Planohybodus sp. and cf. Meristodonoides sp.), this assemblage is remarkable in that there are only very few Mesozoic hybodontiform assemblages with more large-toothed genera or even species. Comparisons with other European Late Jurassic hybodontiform-bearing localities demonstrate fairly homogenous distribution patterns characterized by large-bodied epipelagic forms of high dispersal ability. This is in stark contrast to post-Jurassic hybodontiform associations, which are dominated by smaller species that were predominantly bound to marginal marine and continental waters, suggesting a major reorganization of chondrichthyan communities during the Early Cretaceous.
Highlights
The Late Jurassic marks a critical time interval in the history of life leading to dramatic episodes of global environmental perturbation at the Jurassic/Cretaceous (J/K) boundary [1], which seemingly affected vertebrate communities in both the terrestrial and marine realms (e.g., [2,3,4,5,6,7])
The hybodontiform Strophodus udulfensis is represented by dental material that refers to different ontogenetic stages, suggesting that the marginal marine environments south of Fennoscandia might have provided shelter that maximized growth rates and at the same time minimized the risk of predation
The present study, in which we reassessed a historically collected hybodontiform dental assemblage from the lower Kimmeridgian of Czarnogłowy initially described by Hoffmann [49], contributes to our knowledge of Mesozoic marine vertebrate life, providing promising clues for better understanding Late Jurassic chondrichthyan diversity and distribution patterns
Summary
The Late Jurassic marks a critical time interval in the history of life leading to dramatic episodes of global environmental perturbation at the Jurassic/Cretaceous (J/K) boundary [1], which seemingly affected vertebrate communities in both the terrestrial and marine realms (e.g., [2,3,4,5,6,7]). The controlling factors driving the diversity dynamics of post-Jurassic hybodontiforms remain unresolved. Hybodontiforms, whose fossil record is dominated by isolated dental remains For overview), have been recorded from various European Late Jurassic localities so far (e.g., [17,18,19,20,21,22,23,24,25,26,27,28,29,30,31]), with rather rare occurrences from Asia [32,33,34,35], Africa [36,37] and South. Even after more than two centuries of extensive research, our knowledge of Late Jurassic hybodontiforms is still insufficient, such that their diversity and distribution patterns remain ambiguous and poorly understood. The intention of this study is (1) to provide a detailed taxonomic reassessment of a historically collected hybodontiform dental assemblage from the lower Kimmeridgian of Czarnogłowy in north-western Poland and (2) to discuss its significance in terms of
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