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.

Antarctic Hoploparia exhibit morphologic changes upsection in a stratigraphic record considered to be long (approximately 15 m.y.) and free of major hiatuses. Five characters exhibit change upsection, and the overall morphologies of the geologically oldest and youngest lobsters are different. The observed patterns could be the result of either phyletic evolution or gradual invasion of one or more species into the range of the original species. The most parsimonious interpretation of the data argues against the invasion hypothesis but supports the phyletic evolution hypothesis.

Levinton notes that the number of individuals available to my study of patterns in the evolution of Homo erectus is low, especially when cranial base breadth is considered. If measurements of biauricular breadth are related to stratigraphic age of the fossils using linear regression, the slope obtained is small (−1.52). The confidence interval includes zero, and there is no evidence that a real trend is present. At the same time, the .95 interval is large (±26.81), so slopes differing by even a substantial margin cannot be distinguished. Levinton suggests that this negates a claim for stasis, and I agree that there are grounds for doubt. But by his reasoning, a case for stasis can never be established. While it is true that the occurrence of (very small) trends can never be denied, even if an analysis of many fossils shows a zero slope bracketed by narrow confidence limits, surely these “trends” must be dismissed as insignificant. Given such an outcome, a conclusion of no (directional) change would be quite justified.

Grass-dominated ecosystems cover ~40% of Earth's terrestrial surface, with tropical grasses accounting for ~20% of global net primary productivity. C3 (cool/temperate) and C4 (tropical and subtropical) grass distribution is driven primarily by temperature. In this work, we used phytolith assemblages collected from vegetation plots along an elevation and temperature gradient in the northern Andes (Colombia and Ecuador) to develop a paleothermometer for the region. To accomplish this, we created a transfer function based on the inverse relationship between mean annual temperature (MAT) and the phytolith-based climatic index (Ic), which is the proportion of C3 over C4 grass phytoliths (GSSCP). To evaluate how accurately the index reflects C4–C3 grass abundance in vegetation plots, we compared it with semiquantitative floristic estimates of C4–C3 grass abundance. To further evaluate the 1 − Ic index as a proxy for C4–C3 grass abundance, we compared it with corresponding δ13C values (an independent proxy for C4–C3 vegetation). Results indicate that (1) GSSCP assemblages correctly estimate C4–C3 grass abundance in vegetation plots; (2) the Ic index outperforms the δ13C record in estimating C4–C3 grass abundance, even in open-vegetation types; and (3) our Ic index–based model accurately predicts MAT. This new calibrated proxy will help improve paleotemperature reconstructions in the northern Andes since at least the emergence and spread of C4 grasses in the region during the late Miocene.

The Ordovician–Silurian (~485–419 Ma) was a time of considerable evolutionary upheaval, encompassing both great evolutionary diversification and one of the first major mass extinctions. The Ordovician diversification coincided with global climatic cooling and paleocontinental collision, the ecological impacts of which were mediated by region-specific processes including substrate changes, biotic invasions, and tectonic movements. From the Sandbian–Katian (~453 Ma) onward, an extensive carbonate shelf developed in the eastern Baltic paleobasin in response to a tectonic shift to tropical latitudes and an increase in the abundance of calcareous macroorganisms. We quantify the contributions of environmental differentiation and temporal turnover to regional diversity through the Ordovician and Silurian, using brachiopod occurrences from the more shallow-water facies belts of the eastern Baltic paleobasin, an epicontinental sea on the Baltica paleocontinent. The results are consistent with carbonate shelf development as a driver of Ordovician regional diversification, both by enhancing broadscale differentiation between shallow- and deep-marine environments and by generating heterogeneous carbonate environments that allowed increasing numbers of brachiopod genera to coexist. However, temporal turnover also contributed significantly to apparent regional diversity, particularly in the Middle–Late Ordovician.

Evolutionary rates and selection intensities in eight cladistically defined species-level evolutionary sequences of the Middle and Upper Ordovician bryozoan genus Peronopora were calculated for comparison with values published for fossil and living taxa. Calculations were restricted to statistically significant unidirectional segments of anagenetic series to minimize the mixing of different modes, directions, and rates of evolutionary change.

Rates and selection intensities ranged from 10−7 to 10−6 darwins and from 10−6 to 10−5 haldanes. Across characters, the weighted mean evolutionary rate equaled 5.86 × 10−7 darwins and the mean selection intensity was 6.44 × 10−7. Mean rates of 2.15 × 10−6, 4.31 × 10−6, and 8.61 × 10−6 haldanes, and corresponding mean selection intensities equaling 2.39 × 10−6, 4.78 × 10−6, and 9.56 × 10−6, were calculated for generation lengths of 0.5, 1, and 2 years, respectively.

The magnitudes of positive and negative evolutionary rates and selection intensities do not differ statistically, individual characters display no consistent pattern of positive or negative values, and no character complexes were detectable. A mosaic pattern of change occurs across characters in evolutionary sequences.

Eighty percent of analyzed evolutionary series were multispecies lineages. Both individual and mean values provide direct estimates of the rates of evolution within those lineages at the moment of speciation.

Rates of anagenetic evolution in Peronopora were low and similar to published rates for a variety of fossil protists, invertebrates, and vertebrates. However, earlier rate calculations did not isolate the effect of unidirectional anagenesis from that of stasis, random walks, trend reversals, or rate variations. Eight percent of characters in Peronopora produced anagenetic series that were statistically significant, a percentage similar to the 5% calculated in a study of 251 sequences of evolving traits in 53 fossil lineages (Hunt 2007). Stasis and mutation-drift are the most common patterns detectable in the fossil record, although anagenesis remains a potentially important force in shaping the course of both micro- and macroevolution.

Mark and Flessa (1977) have argued that the evolutionary equilibrium hypothesis requires that there should be significant correlation between generic origins and extinctions, and they presented data on Phanerozoic brachiopods and Cenozoic mammals. Their data are re-examined and the correlations are found not to support their version of the evolutionary equilibrium hypothesis. We argue that the equilibrium hypothesis may not be falsifiable using paleontological data.

Calcareous nannoplankton have been one of the dominant primary producers in the surface oceans since the late Triassic. The bolide impact at the Cretaceous/Paleogene (K/Pg) boundary ~66.0 Ma, led to the elimination of >90% of nannoplankton species: the largest extinction event in their evolutionary history. One of the few nannoplankton genera to survive the K/Pg mass extinction and even thrive in its aftermath was Braarudosphaera, which precipitates pentagonal calcite plates (pentaliths). The only Braarudosphaera species to span the K/Pg boundary (B. bigelowii) is extant and has formed geographically and temporally restricted “blooms” throughout geologic time. Four morphologically and genetically distinct cryptic species of B. bigelowii have been identified in the modern ocean. However, it is uncertain whether these cryptic species have disparate ecophysiological tolerances that have allowed them to adapt to varying environmental conditions. For the first time, we assess changes in the size and shape of Braarudosphaera pentaliths following the K/Pg mass extinction at three geographically and environmentally disparate sites that have early Paleocene Braarudosphaera blooms. Our results show that different Braarudosphaera morphotypes were dominant in the Gulf of Mexico compared with the Tethys Ocean, likely due to regional environmental differences. In addition, we provide evidence that the dominant Braarudosphaera morphotypes shifted in response to changes in upper water column stratification. This ability to rapidly adapt to unstable environments likely helped Braarudosphaera thrive in the aftermath of the K/Pg extinction and explains why this lineage has enjoyed such a long evolutionary history.

Despite the paleontological relevance and paleobiological interest of trigoniid bivalves, our knowledge of their ontogeny—an aspect of crucial evolutionary importance—remains limited. Here, we assess the intra- and interspecific ontogenetic variations exhibited by the genus Steinmanella Crickmay (Myophorellidae: Steinmanellinae) during the early Valanginian–late Hauterivian of Argentina and explore some of their implications. The (ontogenetic) allometric trajectories of seven species recognized for this interval were estimated from longitudinal data using 3D geometric morphometrics, segmented regressions, and model selection tools, and then compared using trajectory analysis and allometric spaces. Our results show that within-species shell shape variation describes biphasic ontogenetic trajectories, decoupled from ontogenetic changes shown by sculpture, with a gradual decay in magnitude as ontogeny progresses. The modes of change characterizing each phase (crescentic growth and anteroposterior elongation, respectively) are conserved across species, thus representing a feature of Steinmanella ontogeny; its evolutionary origin is inferred to be a consequence of the rate modification and allometric repatterning of the ancestral ontogeny. Among species, trajectories are more variable during early ontogenetic stages, becoming increasingly conservative at later stages. Trajectories’ general orientation allows recognition of two stratigraphically consecutive groups of species, hinting at a potentially higher genus-level diversity in the studied interval. In terms of functional morphology, juveniles had a morphology more suited for active burrowing than adults, whose features are associated with a sedentary lifestyle. The characteristic disparity of trigoniids could be related to the existence of an ontogenetic period of greater shell malleability betrayed by the presence of crescentic shape change.

Understanding the drivers of macroevolutionary trends through the Phanerozoic has been a central question in paleobiology. Increasingly important is understanding the regional and environmental variation of macroevolutionary patterns and how they are reflected at the global scale. Here we test the role of biotic interactions on regional ecological patterns during the Mesozoic marine revolution. We test for escalatory trends in Jurassic marine benthic macroinvertebrate ecosystems using occurrence data from the Paleobiology Database parsed by region and environment. The escalation hypothesis posits that taxonomic groups that could adapt to intense predation and bioturbation proliferated, whereas groups unable to adapt were reduced in diversity and abundance or driven to extinction. We tested this hypothesis in five regions during Jurassic stages and among four depositional environments in Europe. Few escalatory trends were detected, although at least one escalatory trend was observed in every region, with the greatest number and strongest trends observed in Europe. These trends include increases in shallow infauna and cementing epifauna and occurrences of facultatively mobile invertebrates and decreases in pedunculate, free-lying, and sessile epifauna. Within Europe, escalatory trends occur in shallow-water environments but also in deeper-water environments, where they are predicted not to occur. When regional trends are aggregated, trends in Europe drive the global signal. The results of this study suggest that while evidence of escalation is rare globally, it is plausible that escalation drove macroevolutionary patterns in Europe. Furthermore, these results underline the need to dissect global fossil data at the regional scale to understand global macroevolutionary dynamics.

Corallite sizes reflect a continuum in the efficacy of photosymbiosis in colonial reef corals, with smaller corallite sizes generally associated with higher autotrophy. Using a large compilation of reef-coral traits and corallite diameters as a proxy, we test here the hypothesis that photosymbiotic efficacy has increased over the evolutionary history of scleractinian corals. To gain a more comprehensive understanding of the evolutionary versus ecological patterns of corallite sizes of reef corals, we used three analytical methods: (1) occurrences-weighted within-bin analyses as a proxy for abundance or ecological dominance to depict ecological patterns; (2) unweighted range-through analyses; and (3) unweighted sampled-in-bin analyses to represent diversity in terms of taxonomic richness, enabling us to trace evolutionary patterns. By-genus, range-through analysis indicates a slightly positive trend of corallite sizes toward the Recent. However, the occurrences-weighted assessment shows a pronounced negative trend of corallite sizes in colonial corals since the Mesozoic. Random walk and directional evolution are both statistically supported to explain this long-term decrease. A driven trend is evolutionarily plausible, giving reef corals a selective advantage in the oligotrophic environments they largely occupy today.

Tree-based paleobiological studies use inferred phylogenies as models to test hypotheses about macroevolution and the quality of the fossil record. Such studies raise two concerns. The first is how model trees might bias results. The second is testing hypotheses about parameters that affect tree inference.

Bias introduced by model trees is explored for tree-based assessments of the quality of the fossil record. Several nuisance parameters affect tree-based metrics, including consistency of sampling probability, rates of speciation / extinction, patterns of speciation, applied taxonomic philosophy, and assumed taxonomy. The first two factors affect probabilistic assessments of sampling, but also can be tested and accommodated in sophisticated probability tests. However, the final three parameters (and the assumption of a correct phylogeny) do not affect probabilistic assessments.

Often paleobiologists wish to test hypotheses such as rates of character change or rates of preservation. Assumptions about such parameters are necessary in simple phylogenetic methods, even if the assumptions are that rates are homogeneous or that sampling is irrelevant. Likelihood tests that evaluate phylogenies in light of stratigraphic data and / or alternative hypotheses of character evolution can reduce assumptions about unknowns by testing numerous unknowns simultaneously. Such tests have received numerous criticisms, largely based in philosophy. However, such criticisms are based on incorrect depictions of the logical structures of parsimony and likelihood, misunderstandings about when arguments are probabilistic (as opposed to Boolean), overly restrictive concepts of when data can test a hypothesis, and simply incorrect definitions of some terms.

Likelihood methods can test multiparameter hypotheses about phylogeny and character evolution (i.e., rates, independence, etc.). The best hypothesis positing a single rate of independent character change (with no variation among character states) is determined for each topology. Hypotheses about rate variation among characters or across phylogeny, character independence, and different patterns of state evolution then are examined until one finds the simplest (i.e., fewest varying parameters) hypothesis that cannot be rejected given knowledge of a more complicated hypothesis. This is repeated for alternative topologies. An example is presented using hyaenids. Two trees are contrasted, one of which requires the minimum necessary steps and the other of which requires at least seven additional steps. Given either tree, likelihood rejects fewer than three general rates of character change and also rejects the hypothesis of independence among the characters. However, hypotheses of changes in rates across the tree do not add substantially to the tree likelihood. The likelihoods of the trees given stratigraphic data also are determined. Both morphologic and stratigraphic data suggest that the multiparameter hypothesis including the parsimony tree is significantly less likely than the multiparameter hypothesis including a different tree.

The classification of fossils has long been controversial. Should traditional taxonomic concepts be expanded to encompass plesiomorphic extinct relatives that exhibit subsets of essential defining characters in so many shades of gray? Should rank taxa, established on extant taxa alone, and in a pre-Darwinian, pre-Hennigian framework, remain restricted to their living constituents and integral extinct relatives? Or should these taxonomic concepts be restricted to a membership exhibiting a defining suite of essential characters, regardless of whether they are extant or extinct?

Rates of speciation and extinction are often linked to many ecological factors, traits (emergent and nonemergent) such as environmental tolerance, body size, feeding type, and geographic range. Marine gastropods in particular have been used to examine the role of larval dispersal in speciation. However, relatively few studies have been conducted placing larval modes in species-level phylogenetic context. Those that have, have not incorporated fossil data, while landmark macroevolutionary studies on fossil clades have not considered both phylogenetic context and net speciation (speciation–extinction) rates. This study utilizes Eocene volutid Volutospina species from the U.S. Gulf Coastal Plain and the Hampshire Basin, U.K., to explore the relationships among larval mode, geographic range, and duration. Based on the phylogeny of these Volutospina, we calculated speciation and extinction rates in order to compare the macroevolutionary effects of larval mode. Species with planktotrophic larvae had a median duration of 9.7 Myr, which compared significantly to 4.7 Myr for those with non-planktotrophic larvae. Larval mode did not significantly factor into geographic-range size, but U.S. and U.K. species do differ, indicating a locality-specific component to maximum geographic-range size. Non-planktotrophs (NPTs)were absent among the Volutospina species during the Paleocene–early Eocene. The relative proportions of NPTs increased in the early middle Eocene, and the late Eocene was characterized by disappearance of planktotrophs (PTs). The pattern of observed lineage diversity shows an increasing preponderance of NPTs; however, this is clearly driven by a dramatic extinction of PTs, rather than higher NPT speciation rates during the late Eocene. This study adds nuance to paleontology's understanding of the macroevolutionary consequences of larval mode.

The first size reduction (FSR) in the Reticulofenestra-Gephyrocapsa-Emiliania (RGE) lineage (order Isochrysidales), which occurred in the early Oligocene (~32 Ma), is of great significance for understanding the Lilliput effect that has affected coccolithophore communities from the late Eocene to this day. We conducted a morphologic analysis on the coccoliths of Reticulofenestra species that lived during the late middle Eocene to early Oligocene (~40–31 Ma), using marine sediments from the South Atlantic Ocean. Our data show increasing size and decreasing abundance of the large species during the late Eocene, leading to their disappearance at the FSR, and a concurrent decrease in the size variability of the small- to medium-sized coccoliths whose central opening diameter had become very reduced. Although the cosmopolitan late Paleogene through Neogene size decrease in coccolithophores has been linked to the concomitant long-term decline in global pCO2, we suggest here that the FSR was the result of environmental destabilization caused by the expansion of eutrophic environments following the late Eocene establishment of overturning circulation associated with ice buildup on Antarctica. This study also leads us to propose a hypothetical model that links coccolith morphology of species of the RGE lineage and trophic resources in the upper ocean: the small- to medium-sized, r-selected coccolithophores with smaller coccolith central openings live in nutrient-rich waters where they rely mostly on photosynthesis and little on mixotrophy, whereas the larger, K-selected species with larger coccolith central openings live in oligotrophic waters where they are more dependent on mixotrophy.