Search for: All records

ABSTRACT Plio-Pleistocene sediments from the southwestern Florida Peninsula contain an extraordinary density and diversity of marine mollusk and vertebrate fossils which, collectively, document major faunal shifts on the Florida Platform through a period of profound environmental change. Systematic study of these fossil assemblages and the environments in which they lived has been limited, however, by: i) a lack of outcrop sections spanning the full Plio-Pleistocene stratigraphy of the region and ii) major uncertainties in correlation between previous study sites due to extreme lateral variability in coastal paleoenvironments. Here, we describe a new stratigraphic section from Florida Shell Quarry in Charlotte County, Florida, which contains fossil-rich deposits of each major Plio-Pleistocene unit in the area (the Tamiami, Caloosahatchee, Bermont, and Fort Thompson formations). Bulk sediment samples collected from 22 horizons were used to broadly characterize stratigraphic variations in lithology and faunal content. Predation intensity was estimated from drill-hole frequency among populations of the bivalve Chione spp. While all studied formations were mainly deposited under marine conditions, both lithologic and faunal facies shifts within the Caloosahatchee and Bermont units indicate periods of pronounced freshwater influence. Faunal diversity is relatively high in the Tamiami, Caloosahatchee, and Bermont units but declines in the Fort Thompson. Similarly, predation intensity is high in the Caloosahatchee and Bermont units but lower in the Fort Thompson at the sampled sites. In addition to characterizing changes in the local paleoenvironment, we propose a sequence stratigraphic model for the section based on inferred local sea-level fluctuations. We leverage this sequence stratigraphic framework to correlate the Florida Shell section with other studied sections in the Charlotte Harbor area. The development of this new site provides a workable basis for more detailed studies of the long-term paleoecological and paleoenvironmental evolution of southwestern Florida. 

Sixty-five species and nine indeterminate taxa of Florida Paleogene echinoids are discussed, and their geographic and stratigraphic distributions provided. These include 49 species documented from the Eocene and 16 from the Oligocene. Ten new species are described: Prionocidaris robertsi n. sp., Rhyncholampas mariannaensis n. sp., Rhyncholampas bao n. sp., Weisbordella inglisensis n. sp., Weisbordella libum n. sp., Durhamella tetrapora n. sp., and Brissus jonesi n. sp. from the Eocene; and Plagiobrissus cassadyi n. sp., Eupatagus dumonti n. sp., and Schizaster carlsoni n. sp. from the Oligocene. We reconsidered subjective junior synonyms of all species and resurrect Neolaganum archerensis, Echinocyamus macneili, and Eupatagus mooreanus. Furthermore, we updated the taxonomy for all included species and their known distributions and provide emended diagnoses for the genera and species of Florida Neolaganidae. In addition, we herein report the occurrence of Porpitella micra in Cretaceous strata of the subsurface of Florida. This remarkable finding makes P. micra the earliest known of all the scutelloids. Echinoids within the Ocala Limestone are placed in five echinoid biozones, which are defined within, these include the Oligopygus phelani, Oligopygus haldemani, Oligopygus wetherbyi, Wythella eldridgei, and Haimea brooksi Zones. This document complements the Neogene (including the Quaternary) fossil echinoid fauna of Florida we published in 2020 and represents a compilation of the known Florida Paleogene echinoid record. The region is currently known to have the most speciose and diverse assemblage of Paleogene echinoids in the United States. 

Abstract Northern Arizona University, Flagstaff, Arizona, USA, recently installed a MIni CArbon DAting System (MICADAS) with a gas interface system (GIS) for determining the¹⁴C content of CO₂gas released by the acid dissolution of biogenic carbonates. We compare 48 paired graphite, GIS, and direct carbonate¹⁴C determinations of individual mollusk shells and echinoid tests. GIS sample sizes ranged between 0.5 and 1.5 mg and span 0.1 to 45.1 ka BP (n = 42). A reduced major axis regression shows a strong relationship between GIS and graphite percent Modern Carbon (pMC) values (m = 1.011; 95% CI [0.997–1.023], R²= 0.999) that is superior to the relationship between the direct carbonate and graphite values (m = 0.978; 95% CI [0.959-0.999], R²= 0.997). Sixty percent of GIS pMC values are within ±0.5 pMC of their graphite counterparts, compared to 26% of direct carbonate pMC values. The precision of GIS analyses is approximately ±70¹⁴C yrs to 6.5 ka BP and decreases to approximately ±130¹⁴C yrs at 12.5 ka BP. This precision is on par with direct carbonate and is approximately five times larger than for graphite. Six Plio-Pleistocene mollusk and echinoid samples yield finite ages when analyzed as direct carbonate but yield non-finite ages when analyzed as graphite or as GIS. Our results show that GIS¹⁴C dating of biogenic carbonates is preferable to direct carbonate¹⁴C dating and is an efficient alternative to standard graphite¹⁴C dating when the precision of graphite¹⁴C dating is not required. 

The influence of functional traits on species survivorship has been evaluated in various contexts in both modern and ancient ecosystems, but an important direction for research is to integrate datasets that include both extinct and extant taxa. This approach can provide a more reliable understanding of the effects of functional traits on macroecological and macroevolutionary dynamics. Knowledge of the links between individual traits and survivorship is crucial for developing accurate extinction risk predictive models. Here we test the impact of numerous functional traits on the survival and extinction of species through time, using bivalve and gastropod species from the rich fossil record of the western Atlantic over the last ~3 million years, along with the associated extant biota. We also compare the impact of these organismic traits on survival relative to a group level trait: geographic distribution. Analyses use a dataset of 12 functional traits including life habit, feeding behavior and basal metabolic rate (BMR), for 115 species from 36 families. Traits were observed and measured from specimens in the collections of the Paleontological Research Institution, Florida Museum of Natural History, and University of Kansas, as well as surveys of the literature and online databases such as the Neogene Marine Biota of Tropical America (NMITA). Results derived from Principal Coordinates Analysis (PCoA) show there is a clear distinction between extinct and extant species, overall, when comparing them based on life habit, maximum body size, shell composition and BMR. Most traits showed little direct relation with survival, except BMR and associated maximum body size, supporting the Metabolic Theory of Ecology. Since many functional traits do not explain survival, their function may be mis- or over-interpreted, and traits posited to represent important organismic adaptations may not play a prominent role in long-term species survival, especially during the major climate changes over the last ~ 3 million years. Some traits do show significant interactions, and these were more fully explored using additional multivariate analyses. The relative importance of geographic range size suggests group-level characters may be the primary determinant of extinction patterns over macroevolutionary time scales. 

Predicting the effects of anthropogenic climate change on Earth’s marine mollusk species is highly relevant, as many are critical human food resources and indispensable members of marine ecosystems. To predict which species will go extinct and which will survive, it is essential to understand the past climate species have experienced, as well as determine the relationship between functional traits, which provide a direct connection to organismal ecology, and survival. Many extant West Atlantic (WA) mollusks, especially gastropods and bivalves, survived the Mid-Pliocene Warm Period and the Last Interglacial, warm intervals compared to the present, that can serve as analogues for predicted future conditions of anthropogenic climate change. WA mollusks have an exceptional Neogene fossil record, which makes them an ideal group to study to develop a predictive extinction risk framework. The present research focuses on the correlation between functional traits and extinction in over 80 species of WA mollusks, both extant and extinct. Functional trait data such as body size, mobility, diet, bathymetric depth range, and organism-substrate relationship, which correlate with metabolic requirements, a known factor in extinction risk, and degree and type of ornamentation, shell shape in bivalves, and narrowness of the aperture in gastropods, which correlate with predation resistance, were collected across these species. These comprise both continuous and discrete character data. Various statistical tests were applied to the database to examine variable correlation/interaction, and the relative contributions of traits to extinction risk. Traits related to metabolism were strong predictors of survival; traits related to predation resistance play a less important role. While this study focuses on organismic traits, the aim of future research will be to explore how group characteristics such as geographic range are associated with functional traits and extinction risk for these species. A predictive framework is developed using patterns of extinction in the fossil record to infer survival of various species in the future, which will be relevant for evaluating the potential consequences of climate change, global change biology, and for determining which species should be targeted for conservation efforts. 

Predation traces found on fossilized prey remains can be used to quantify the evolutionary history of biotic interactions. Fossil mollusc shells bearing these types of traces provided key evidence for the rise of predation during the Mesozoic marine revolution (MMR), an event thought to have reorganized global marine ecosystems. However, predation pressure on prey groups other than molluscs has not been explored adequately. Consequently, the ubiquity, tempo and synchronicity of the MMR cannot be thoroughly assessed. Here, we expand the evolutionary record of biotic interactions by compiling and analysing a new comprehensively collected database on drilling predation in Meso-Cenozoic echinoids. Trends in drilling frequency reveal an Eocene rise in drilling predation that postdated echinoid infaunalization and the rise in mollusc-targeted drilling (an iconic MMR event) by approximately 100 Myr. The temporal lag between echinoid infaunalization and the rise in drilling frequencies suggests that the Eocene upsurge in predation did not elicit a coevolutionary or escalatory response. This is consistent with rarity of fossil samples that record high frequency of drilling predation and scarcity of fossil prey recording failed predation events. These results suggest that predation intensification associated with the MMR was asynchronous across marine invertebrate taxa and represented a long and complex process that consisted of multiple uncoordinated steps probably with variable coevolutionary responses. 

ABSTRACT Interactions with predators and parasites can result in traces found on Recent and fossil echinoids. However, identifying specific trace makers, particularly on fossil echinoids, remains contentious. To document the range of trace morphologies present on echinoids and improve our ability to identify and quantify biotic interactions affecting echinoids, we characterized traces found on fossil echinoids using museum collections and field sampling spanning the Jurassic to Recent worldwide. Using light microscopy, 8,564 individual echinoid specimens were examined including 130 species, and 516 traces of potential biotic interactions identified. Morphological characteristics were recorded for each trace, including the shape of the trace outline, maximum diameter and cross-section profile. Based on shared morphological characteristics, it was possible to classify all traces into eight categories: circular, subcircular, elongated, irregular, rectangular, figure-eight, notched, and linear. Cross-section characteristics provided additional insights into the identity of potential trace makers. To further evaluate the proposed biotic origins of these traces, trace diversity was examined through time and compared with anticipated ecological trends associated with the diversification of echinoids, and their predators and parasites. Trace diversity increased over time, starting in the late Eocene, coincident with the proliferation of echinoid-drilling gastropods, an indication that biotic interactions intensified through evolutionary time, as predicted by several macroevolutionary hypotheses previously tested using mollusks. The morphological descriptions provided here enhance our understanding of biotic traces on fossil echinoids, and the potential to identify temporal trends in the intensity and diversity of biotic interactions that have affected echinoids throughout their evolutionary history.