Prospective and early-career paleontologists deserve an accurate assessment of employment opportunities in their chosen field of study. Drawing on a wide range of sources, we have produced an admittedly incomplete analysis of the current status and recent trends of permanent academic employment in the discipline. Obtaining more complete longitudinal data on employment trends is a major difficulty; this is a challenge that needs to be addressed. The number of job seekers is far in excess of available positions. There has been a clear erosion in the number of academic paleontologists in the United States, a trend exacerbated in recent years. The decline, in constant dollars, of federal funding for paleontological research has potential strong negative impacts on future hiring. The loss of paleontology positions has also had a deleterious effect on our professional societies, which have seen a loss of regular (professional) membership, although student membership remains strong. These trends also potentially negatively impact efforts to diversify the field. Professional societies need to better coordinate their efforts to address these serious issues. Individual paleontologists also must become more effective advocates for the importance and relevance of our science.

Life-history traits such as dispersal affect population attributes like gene flow, which can have consequences for speciation and extinction rates over macroevolutionary timescales. Here we use the Cheilostomatida, a monophyletic order of marine bryozoans, to test whether a life-history trait, larval brooding, affected the origination and extinction rates of genera throughout their fossil record. Cheilostome lineages that brood their larvae have shorter larval dispersal distances than non-brooding lineages, which has led to the hypothesis that the evolution of larval brooding decreased gene flow, increased origination, and drove their Cretaceous diversification. Brooding cheilostomes are far more diverse than non-brooding cheilostomes today, but it remains to be shown that brooding lineages have a higher origination rate than non-brooders. We fit time-varying Pradel seniority capture–mark–recapture models to look at the effect of brooding on origination and extinction rates during the Cretaceous cheilostome diversification, the Cretaceous/Paleogene mass extinction and recovery, and through the Cenozoic. Our results support the hypothesis that brooding affects origination rate, but only in the Cenomanian to Campanian. Extinction rates do not differ between brooding and non-brooding genera, and there is no regime shift specific to the Cretaceous/Paleogene mass extinction. Our work illustrates the importance of using fossil occurrences and time-varying models, which can detect interval-specific diversification differentials.

Body mass is an important facet of reconstructing the paleobiology of fossil species and has, historically, been estimated from individual skeletal measurements. This paper demonstrates the potential advantages of estimating body mass using 3D geometric morphometrics on limb bones, which allows size to be explicitly contextualized within the functional morphology of the animal. Geometric morphometrics of the humerus and femur is used to estimate body mass in domestic dogs and wild canids, and the resulting estimates are compared with estimates made using limb bone dimensions and centroid size. In both groups, 3D methods produced more accurate estimates of body mass than linear dimensions. Additionally, centroid size was a poor predictor of body mass and should not be preferred over linear measurements. The use of 3D methods also reveals specific aspects of shape that are associated with different sizes. In general, relatively heavier individuals were associated with more robust bones and wider articulation sites, as well as larger attachment sites for muscles related to flexion and extension of the shoulder and hip joints. The body-mass equations constructed based on dogs were further evaluated on wild canids, as a test of their potential efficacy on fossil canids. With some adjustments, the body-mass estimation equations made for domestic dogs were able to reliably predict the mass of wild canids. These equations were then used to estimate body mass for a selection of fossil canids: Canis latrans, 16 kg; Aenocyon dirus, 67 kg; Phlaocyon multicuspus, 8 kg; and Hesperocyon gregarius, 2.5 kg.

The evolution of mammalian innovations like elevated growth rates, endothermy, and live birth has been the subject of paleobiological work for decades. Bone histology provides one of the best lines of evidence for assessing growth rates and life-history traits in the fossil record. However, little ontogenetic information is available for nonmammalian cynodonts, the stock lineage that eventually gave rise to mammals. Here, I report the bone histology of two traversodontid cynodonts from the Triassic Manda Formation of Tanzania. Using two femoral size series, I correlate bone tissue composition and limb size in Scalenodon angustifrons and Luangwa drysdalli. Fifteen individuals were analyzed from seven penecontemporaneous localities to assess intraspecific histovariation within traversodontid ontogenetic development for the first time. My results show that Scalenodon and Luangwa have disparate life histories despite being similarly sized contemporaries. Luangwa is characterized by parallel-fibered bone that transitions to woven-parallel bone early in ontogeny, interpreted as a growth spurt. This increase in growth rate is seen in small- and middle-sized individuals but is resorbed and remodeled in the largest, skeletally mature individual. By contrast, Scalenodon is characterized by woven-parallel tissue in early ontogeny. However, femur size is not correlated with changes in bone tissue composition, as multiple individuals show peripheral slower-growing tissue regardless of size, interpreted as highly developmentally plastic growth. Together, these results demonstrate that coeval members of Traversodontidae show disparate life histories. The underlying mechanisms to explain different life histories in these taxa are likely due to (1) intrinsic differences in growth rates and (2) varying degrees of developmentally flexible growth. The implication of this work is that intraspecific variation in growth dynamics may be more widespread than currently understood in cynodonts and that size is not a good indicator of maturity for some species.

A central goal in ecology is investigating the impact of major perturbations, such as invasion, on the structure of biological communities. One promising line of inquiry is using co-occurrence analyses to examine how species’ traits mediate coexistence and how major ecological, climatic, and environmental disturbances can affect this relationship and underlying mechanisms. However, present communities are heavily influenced by anthropogenic behaviors and may exhibit greater or lesser resistance to invasion than communities that existed before human arrival. Therefore, to disentangle the impact of individual disturbances on mammalian communities, it is important to examine community dynamics before humans. Here, we use the North American fossil record to evaluate the co-occurrence structure of mammals across the Great American Biotic Interchange. We compiled 126 paleocommunities from the late Pliocene (4–2.5 Ma) and early Pleistocene (2.5–1 Ma). Genus-level co-occurrence was calculated to identify significantly aggregated (co-occur more than expected) and segregated (co-occur less than expected) genus pairs. A functional diversity analysis was used to calculate functional distance between genus pairs to evaluate the relationship between pair association strength and functional role. We found that the strength distribution of aggregating and segregating genus pairs does not significantly change from the late Pliocene to the early Pleistocene, even with different mammals forming the pairs, including immigrant mammals from South America. However, we did find that significant pairs, both aggregations and segregations, became more similar in their functional roles following the Plio-Pleistocene transition. Due to different mammals and ecological roles forming significant associations and the stability of co-occurrence structure across this interval, our study suggests that mammals have fundamental ways of assembling that may have been altered by humans in the present.

Ostracoderms, Paleozoic jawless stem-gnathostomes, are characterized by distinctive bony shields covering the front of their bodies. These headshields exhibit significant variations in morphology across species, boasting frontal, lateral, and dorsal processes. Ostracoderms represent pivotal intermediaries between modern jawless and jawed vertebrates, so understanding their biology and ecology is crucial for unraveling the selective pressures that shaped the early evolution and diversification of jawed vertebrates, which now dominate vertebrate diversity. This study employs virtual paleontology techniques and phylogenetic comparative methods to explore the hydrodynamic and ecological implications of these processes, focusing on pteraspidomorphs, the most diverse ostracoderm group. The analysis reveals widespread convergence in the arrangement and development of headshield processes. Lateral processes enhance hydrodynamic efficiency and generate lift, while combined lateral and dorsal processes provide stability in rolling, yawing, and pitching. Frontal processes reduce drag in many cases. These findings illuminate the enigmatic roles of ostracoderm headshields, showing how the dimensions and arrangement of their processes are biomechanically linked to a range of functions and ecological roles. Collectively, this highlights the intricate evolutionary pathways of lifestyles and ecologies within stem-gnathostomes, challenging the idea of a unidirectional trend toward more active lifestyles in vertebrate evolution and suggesting diverse ecological roles for ostracoderms.

Ichthyosauria, Plesiosauria, and Metriorhynchidae were apex predators in Mesozoic oceanic trophic networks. Previous stable oxygen isotope studies suggested that several taxa belonging to these groups were endothermic and that some of them were homeothermic organisms. However, these conclusions remain contentious owing to the associated uncertainties regarding the δ18O value and oxygen isotope fractionation relative to environmental seawater. Here, we present new bioapatite phosphate δ18O values (δ18Op) of Ichthyosauria, Plesiosauria, and Metriorhynchidae (Middle Jurassic to Early Cretaceous) recovered from mid- to high paleolatitudes to better constrain their thermophysiology and investigate the presence of regional heterothermies. The intraskeletal δ18Op variability failed to reveal distinct heterothermic patterns within any of the specimens, indicating either intrabody temperature homogeneity or an overriding diagenetic overprint of the original biological δ18Op bone record. Body temperature estimates have been reassessed from new and published δ18Op values of well-preserved isolated teeth, recently revised Mesozoic latitudinal δ18O oceanic gradients, and 18O-enrichment factors of fully aquatic air-breathing vertebrates. Our results confirm that Ichthyosauria were homeothermic endotherms (31°C to 41°C), while Plesiosauria were likely poikilothermic endotherms (27°C to 34°C). The new body temperature estimates of the Metriorhynchidae (25°C to 32°C) closely follow ambient temperatures and point to poikilothermic strategy with no or little endothermic ability. These results improve our understanding of Mesozoic marine reptile thermoregulation and indicate that due to their limited body temperature variations, the δ18Op values from Ichthyosauria fossil remains could be used as valuable archives of Mesozoic oceans δ18Osw values that may help improve paleoenvironmental and paleoclimatic reconstructions.

Toothed whales (odontocetes) make use of high-frequency sounds to echolocate, differing significantly from their sister group baleen whales (mysticetes), which make use of low-frequency sound for long-distance communication. This divergence in auditory ability has led to considerable speculation as to how hearing functioned in the ancestral archaeocetes, and when the specializations of modern species arose. Numerous studies have attempted to infer auditory capabilities from morphological correlates valid in modern species. Here, we build upon these previous methods with a focus on cochlear structures that have well-understood links to function. We combine this with information on the sound conduction apparatus to chart the evolutionary trajectory of cetacean hearing. Our results suggest an initial move toward low-frequency specialization in early Eocene cetaceans, which coincides with the appearance of new sound conduction pathways. This paved the way for the later movement toward higher-frequency hearing in protocetids; however, the ultra-high- and low-frequency hearing specializations of both modern cetacean clades evolved after their divergence. We use these data to test the hypotheses that evolutionary brain size increases in cetaceans were related to the origin of high-frequency echolocation. We show that no shift in relative brain size coincides with any changes toward high-frequency perception. However, this does not rule out a role for other changes in hearing ability such as some simple forms of echolocation, similar to that suggested for hippopotamuses or bowhead whales, which may have been present in even the earliest cetaceans.

Analysis of length-frequency data using the ELEFAN (Electronic Length-Frequency Analysis) approach and software is widely used to quantify the growth, mortality, longevity, and related parameters of Recent marine animals. Here we analyze a sample (n = 211) of the Ediacaran metazoan Parvancorina minchami Glaessner, 1958, from the Vendian siliciclastic marine deposits of the southeastern White Sea region, Russia. The results fit a von Bertalanffy equation with the parameters L∞ = 2 cm, K = yr−1 (with t0 not estimated) and an instantaneous rate of mortality (M) of 1.44 yr−1, implying M/K ≈ 2, as commonly occurs in Recent small invertebrates. These parameter values also imply a longevity for P. minchami of about 4 yr. The concepts and approach used here, previously applied to an Ordovician trilobite and a Cambrian radiodont, suggest that inferences on growth, mortality, longevity, and related parameters can be obtained from suitable size-frequency samples of long-extinct metazoans, opening new vistas on their growth dynamics and functional roles in ancient ecosystems.

The Neotropics host the highest diversity of plants on the Earth today and have done since at least the late Paleogene (~58 Ma). Several mechanisms have been proposed to explain this elevated diversity, but the empirical patterns of Neotropical plant diversification that would test key aspects of those mechanisms are still unclear. We use an extensive palynological database from northern South America to characterize patterns of extinction, origination, and diversity and their possible drivers since the Paleogene. The foreland Llanos basin of Colombia preserves the evolutionary history of Neotropical vegetation as well as the geological evolution of northern South America, offering a unique opportunity to study the relationship between the geological and fossil records. The palynological record of the Llanos basin has been intensely studied mainly for oil exploration, and we use this information to infer the evolutionary history of Neotropical vegetation in Colombia during the Cenozoic. There is no straightforward relationship between global temperature and Neotropical plant diversity. Nevertheless, environmental change had an important influence on the dynamics of diversification, especially during volatile climate intervals such as the Paleocene–Eocene and the Pleistocene. Pulses of regional extinction were driven by large-scale temperature excursions, including both warming and cooling phases. Time-lagged origination pulses results in rapid floral replacement on a timescale of 1 Myr. Origination and extinction are essentially balanced on long timescales, leading to a near-zero long-term net diversification rate. Regional geological events, like the uplift of the Andean Cordillera, and changes in paleogeography also played an important role in Neotropical plant diversification.

Genome size (GS) is thought to be a key life-history trait and important for controlling plant distributions and evolutionary dynamics, but a full understanding of GS variation through evolutionary history requires proxy measurements from fossils. Here, we compare two potential GS proxies: guard cell length (GCL) and sporomorph size. We generated GCL and pollen size data from angiosperms growing in the University of Münster Botanical Garden, compiled sporomorph size data from the literature, and related these to GS using phylogenetic regression models. We also fit evolutionary models to the botanical garden data and used a published dataset to validate GCL as a GS proxy. The majority of the analyses conducted revealed a positive relationship between GS and sporomorph size, but in most cases, the explanatory power of the regressions was low. GCL showed a stronger and more consistent relationship with GS, and independent validation of the relationship showed a generally good match between predicted and observed GS. Sporomorph size is not suitable as a cross-taxon GS proxy, but some specific taxa (e.g., Pinus) may contain useful GS information. GCL has much more potential for measuring paleo-GS, but requires further research for us to better understand possible environmental controls on cell size variation.