The chondrichthyan fossil record of the Florida Platform (Eocene–Pleistocene)

Abstract

As of September 2019, the Florida Museum of Natural History (FLMNH) had a curated collection of 117,449 chondrichthyan specimens from Florida, spanning the Eocene through the Pleistocene. Herein, I evaluate the completeness of the chondrichthyan fossil record from Florida based on the FLMNH collection, while analyzing patterns in taxonomic and ecomorphological diversity. At least 70 chondrichthyan taxa were recognized, representing 10 orders, 26 families, and 42 genera; of which, 20 taxa represent first occurrences from Florida. A sample of 107,698 specimens was organized into 12 time bins to analyze taxonomic and ecomorphological diversity, with an expectation that diversity patterns would correspond with global climate events (e.g., the Eocene–Oligocene transition and the middle Miocene climatic optimum). However, diversity patterns were obscured by pervasive sampling bias, attributable to variable collection methods, research prioritizations, and regional lithologic controls. Sampling is particularly poor for smaller specimens and older geologic units (e.g., the Paleogene). Despite incomplete sampling of the Florida chondrichthyan fossil record, there was an apparent turnover along the Atlantic and Gulf Coastal Plains from a lamniform- to carcharhiniform-dominated chondrichthyan fauna that occurred during the Eocene. This turnover corresponded with the extinction of many lamniform taxa with grasping-dominated dentition types (e.g., Brachycarcharias, Jaekelotodus, and Macrorhizodus). Selachian taxa that survived the late Eocene extinctions were predominantly represented by cutting-dominant dentition types. As cutting aids in the dismemberment of prey, this may reflect a macroevolutionary trend toward active predation and scavenging on larger prey, such as marine mammals, teleost fish, and other sharks.

A previously overlooked, highly diverse early Pleistocene elasmobranch assemblage from southern Taiwan

“…The fossil record indicates that the fossil species preferred warm neritic environments ( Cappetta, 2004 ; Cappetta, 2012 ). Although most previous studies suggest its last appearance at the end of the Pliocene, new evidence indicates that † H. serra persisted into the Pleistocene in North America ( Ebersole, Ebersole & Cicimurri, 2017 ; Boessenecker, Boessenecker & Geisler, 2018 ; Perez, 2022 ). Teeth of Hemipristis that may belong to H. serra have been reported from Pleistocene and ‘Plio-Pleistocene’ deposits in Sulawesi and Java, Indonesia ( H .…”

“…We note that our bulk sediment sampling (830 kg, see methods) only yielded three specimens (ASIZF0100548, ASIZF0100590, and ASIZF0100591). Surface collecting likely results in sampling bias towards larger specimens, underrepresenting smaller specimens ( Welton & Farish, 1993 ; Perez, 2022 ). Nevertheless, 697 elasmobranch teeth from the Liuchungchi Formation in Niubu described in this study document the presence of at least 20 elasmobranch taxa ( Table 1 ).…”

First report in the fossil record of a shark tooth embedded in a pinniped bone

“…The fact that this bite was concentrated on an area of the body with minimal fat may have led to tooth failure, as it punctured the hard bone. Broadly triangular, serrated teeth, like those of Carcharodon carcharias, are regarded as representative of the cutting functional type and are thought to be adapted for feeding on large, fleshy prey (Frazzetta 1988;Kent 1994;Perez 2022a). Having a dentition equipped with cutting-type teeth allows predators to dismember their prey more effectively than other tooth morphologies.…”