A new siderolitid from the late Maastrichian of Italy

Abstract

During the latest Cretaceous, many representatives of the larger benthic foraminifera (LBF) community reached a high level of “maturation”, developing large-sized shells with complex architectures. Increasing size and complexity in a relatively short period of time can be interpreted as a rapid response to biologic competition for space and resources with other LBF (like for instance fabularids, lacazinids, alveolinids, rotaliids, orbitoidids) in the shallow carbonate to mixed carbonate-clastic platforms. A paradigm of this type of fast evolution is the group of the Siderolitidae, lamellar-perforate LBF with a complex canal system that were abundant in shallow-water platforms during the late Cretaceous (Campanian-Maastrichtian). Five genera have been described up to now that represent five different steps of evolution in terms of complexity: Arnaudiella, Praesiderolites, Pseudosiderolites, Wannierina and Siderolites. In broad terms, the species ascribed to these genera replace each other in time, offering a good tool for high resolution biostratigraphy. Recent studies on material from the late Maastrichtian of Italy have yielded a siderolitid with a singular architectural pattern that differs from its relatives. The new morphotype has a very large test with large canaliferous spines and a very complex enveloping canal system. This new morphotype is the youngest siderolitid known so far. Strontium isotope stratigraphy indicates a late Maastrichtian age of 66.4 ±1.5 Ma, very close to the K-Pg boundary. The large size and very high complexity shown by the new morphotype are in accordance with the general evolutionary trends of LBF.

During the latest Cretaceous, many representatives of the larger benthic foraminifera (LBF) community reached a high level of “maturation”, developing large-sized shells with complex architectures. Increasing size and complexity in a relatively short period of time can be interpreted as a rapid response to biologic competition for space and resources with other LBF (like for instance fabularids, lacazinids, alveolinids, rotaliids, orbitoidids) in the shallow carbonate to mixed carbonate-clastic platforms. A paradigm of this type of fast evolution is the group of the Siderolitidae, lamellar-perforate LBF with a complex canal system that were abundant in shallow-water platforms during the late Cretaceous (Campanian-Maastrichtian). Five genera have been described up to now that represent five different steps of evolution in terms of complexity: Arnaudiella, Praesiderolites, Pseudosiderolites, Wannierina and Siderolites. In broad terms, the species ascribed to these genera replace each other in time, offering a good tool for high resolution biostratigraphy. Recent studies on material from the late Maastrichtian of Italy have yielded a siderolitid with a singular architectural pattern that differs from its relatives. The new morphotype has a very large test with large canaliferous spines and a very complex enveloping canal system. This new morphotype is the youngest siderolitid known so far. Strontium isotope stratigraphy indicates a late Maastrichtian age of 66.4 ±1.5 Ma, very close to the K-Pg boundary. The large size and very high complexity shown by the new morphotype are in accordance with the general evolutionary trends of LBF.

During the latest Cretaceous, many representatives of the larger benthic foraminifera (LBF) community reached a high level of “maturation”, developing large-sized shells with complex architectures. Increasing size and complexity in a relatively short period of time can be interpreted as a rapid response to biologic competition for space and resources with other LBF (like for instance fabularids, lacazinids, alveolinids, rotaliids, orbitoidids) in the shallow carbonate to mixed carbonate-clastic platforms. A paradigm of this type of fast evolution is the group of the Siderolitidae, lamellar-perforate LBF with a complex canal system that were abundant in shallow-water platforms during the late Cretaceous (Campanian-Maastrichtian). Five genera have been described up to now that represent five different steps of evolution in terms of complexity: Arnaudiella, Praesiderolites, Pseudosiderolites, Wannierina and Siderolites. In broad terms, the species ascribed to these genera replace each other in time, offering a good tool for high resolution biostratigraphy. Recent studies on material from the late Maastrichtian of Italy have yielded a siderolitid with a singular architectural pattern that differs from its relatives. The new morphotype has a very large test with large canaliferous spines and a very complex enveloping canal system. This new morphotype is the youngest siderolitid known so far. Strontium isotope stratigraphy indicates a late Maastrichtian age of 66.4 ±1.5 Ma, very close to the K-Pg boundary. The large size and very high complexity shown by the new morphotype are in accordance with the general evolutionary trends of LBF.