Diversity Patterns of Late Jurassic Chondrichthyans: New Insights from a Historically Collected Hybodontiform Tooth Assemblage from Poland

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.

A new hybodontiform shark (StrophodusAgassiz 1838) from the Lower Cretaceous (Valanginian-Hauterivian) of Colombia

“…Strophodus recognized species.—Based on the list presented by Stumpf, Meng & Kriwet (2022) and the species recognized by Szabó & Főzy (2020) , Kumar et al (2022) , and Sharma & Singh (2021) , Strophodus is represented by at least 12 species, which in stratigraphic order include: (1) S. cf. reticulatus Agassiz, 1838 from the Middle Triassic of Switzerland (see Rieppel, 1981 ) and S. reticulatus from the Bathonian–Tithonian of England, France, Germany, Hungary and Switzerland (see Stumpf, Meng & Kriwet, 2022 and references therin); (2) S. smithwoodwardi ( Peyer, 1946 ) from the Toarcian of Switzerland; (3) S. dunaii ( Szabó & Főzy (2020) , from the Aalenian of Hungary; (4) S. tenuis Agassiz, 1838 from Aalenian–Bathonian strata of Germany and England ( Rees & Underwood, 2008 ); (5) S. longidens ( Agassiz, 1838 ) (type species) from the Bathonian of France; (6) S. magnus ( Agassiz, 1838 ) from the Bathonian of England, France and India ( Rees & Underwood, 2008 ; Sharma & Singh, 2021 ; Rigal & Cuny, 2016 ); (7) S. indicus ( Sharma & Singh, 2021 ) from the Bathonian of India; (8) S. jaisalmerensis ( Kumar et al, 2022 ) from the Bathonian of India; (9) S. medius ( Owen, 1869 ) from the Bathonian–Callovian of France, England and India ( Rees & Underwood, 2008 ; Sharma & Singh, 2021 ); (10) S . subreticulatus ( Agassiz, 1838 ) from the Kimmeridgian of Switzerland; (11) S .…”

“…subreticulatus ( Agassiz, 1838 ) from the Kimmeridgian of Switzerland; (11) S . udulfensis ( Leuzinger et al, 2017 ) from the Kimmeridgian of Switzerland and possibly England ( Stumpf, Meng & Kriwet, 2022 ); and (12) S . tridentinus ( Zittel, 1870 ), from the Tithonian of Italy (considered as nomen dubium by Szabó & Főzy, 2020 ).…”

“…Differential diagnosis .—Following Stumpf et al (2021) , species based on teeth and previously assigned to the genus Asteracanthus , but possibly referable to Strophodus are considered here for comparisons. Assuming this, we compare our specimens from Colombia with the at least 12 recognized Strophodus species from the Jurassic of Europe and India ( Rees & Underwood, 2008 ; Szabó & Főzy, 2020 ; Kumar et al, 2022 ; Sharma & Singh, 2021 ; Stumpf, Meng & Kriwet, 2022 ). In this regard, our new species from the Lower Cretacaous of Colombia can be distinguished from the following European and Asian species by the differences presented below.…”

“…nov. differs from S . udulfensis from the Kimmeridgian of Switzerland and possibly England ( Stumpf, Meng & Kriwet, 2022 ), by having less mesio-distally elongated anterolateral and lateral teeth with less convex and domed crown and lacking the strong reticulated ornamentation that characterize S . udulfensis .…”

“…, Cappetta, 2012 ); although some articulated and delicately preserved specimens have also been reported ( Stumpf et al, 2021 , and references therein). Many hybodontiform species were described using isolated teeth and spines only, one example is the genus Asteracanthus ( Agassiz, 1837 ), considered to be one of the most common hybodontiforms, given that teeth and spines traditionally referred to this genus have been reported worldwide from Middle Triassic to Upper Cretaceous strata ( Rees & Underwood, 2008 ; Cappetta, 2012 ; Szabó & Főzy, 2020 ; Stumpf et al, 2021 ; Stumpf, Meng & Kriwet, 2022 ). Agassiz (1837) named the type species Asteracanthus ornatissimus using isolated fin spines characterized by prominent stellate tubercles from the Upper Jurassic of England.…”