Palaeontology meets metacommunity ecology: The Maastrichtian dinosaur fossil record of North America as a case study.

Documenting the patterns and potential associated processes of ancient biotas has always been a central challenge in palaeontology. Over the last decades, intense debate has focused on the organisation of dinosaur–dominated communities, yet no general consensus has been reached on how these communities were organised in a spatial context and if primarily affected by abiotic or biotic agents. Here, we used analytical routines typically applied in metacommunity ecology to provide novel insights into dinosaurian distributions across the latest Cretaceous of North America. To do this, we combined fossil occurrences with functional, phylogenetic and palaeoenvironmental modelling, and adopted the perspective that more reasonable conclusions on palaeoecological reconstructions can be gained from studies that consider the organisation of biotas along ecological gradients at multiple spatial scales. Our results showed that dinosaurs were restricted in range to different parts of the Hell Creek Formation, prompting the recognition of discrete and compartmentalised faunal areas during the Maastrichtian at fine-grained scales, whereas taxa ranges formed quasi–nested groups when combining data from various geological formations across the Western Interior of North America. Although groups of dinosaurs had coincident range boundaries, their communities responded to multiple ecologically–important gradients when compensating for differences in sampling effort. Metacommunity structures of both ornithischians and theropods were correlated with climatic barriers and potential trophic relationships between herbivores and carnivores, thereby suggesting that dinosaurian faunas were shaped by physiological constraints and a combination of bottom-up and top-down forces across multiple spatial grains and extents.Additional Supporting files include the following Appendices: Appendix S1. Body mass distributions based on product partition models with Markov sampling computations. Appendix S2. Functional and phylogenetic features for each spatial scale and study clade. Appendix S3. R packages and statistical routines. Appendix S4. Elements of metacommunity structure for the conservative fixed–fixed null model. Appendix S5. Results for the forward selection of explanatory variables. Appendix S6. Results for ordinary least squares (OLS) regression models. Appendix S7. Results for commonality analysis (CA) for each spatial scale and study clade. Appendix S8. Measuring the spatial autocorrelation of OLS model residuals. The Excel file includes occurrence data, palaeoenvironmental reconstructions, and functional features: Sheets 1 and 2 contain raw information on each study site for the Hell Creek and other North American geological formations, respectively. Sheet 1 includes palaeoenvironmental information for the Hell Creek Formation (i.e. lithofacies -C, channel; FP, floodplain- and palaeotopography -m.a.s.l. after log-transformation). Raw PalaeoDEM data (Scotese and Wright, 2018) are also available here: https://www.earthbyte.org/paleodem-resource-scotese-and-wright-2018/ Sheet 2 contains raw information on the log-transformed palaeoenvironmental reconstructions for the Maastrichtian of North America (Palaeotopography -m.a.s.l., TempMean and TempSDann in K; Prec and PrecSDann in kgm-2). Raw palaeoclimate GCMs (Valdés et al., 2017) can also be obtained here: https://www.paleo.bristol.ac.uk/ummodel/scripts/papers/ Sheet 3 includes a taxon-specific classification into several functional guilds (see the main text for details): These files may be opened and edited in Excel. For details or further queries, please contact Jorge García-Girón ([email protected]). Funding provided by: University of León*Crossref Funder Registry ID: Award Number: 2017Funding provided by: Spanish Ministry of Economy and Industry*Crossref Funder Registry ID: Award Number: CGL2017–84176RFunding provided by: Junta de Castilla y LeónCrossref Funder Registry ID: http://dx.doi.org/10.13039/501100014180Award Number: LE004G18Funding provided by: Academy of FinlandCrossref Funder Registry ID: http://dx.doi.org/10.13039/501100002341Award Number: 331957Funding provided by: Academy of FinlandCrossref Funder Registry ID: http://dx.doi.org/10.13039/501100002341Award Number: 322652Funding provided by: European Research Council Starting Grant*Crossref Funder Registry ID: Award Number: ERC StG 2017, 756226, PalMFunding provided by: University of LeónCrossref Funder Registry ID: Award Number: 2017Funding provided by: Spanish Ministry of Economy and IndustryCrossref Funder Registry ID: Award Number: CGL2017–84176RFunding provided by: European Research Council Starting GrantCrossref Funder Registry ID: Award Number: ERC StG 2017, 756226, PalMDinosaur occurrences for the Maastrichtian of North America were retrieved from the Palaeobiology Database on May 2020, using the taxon name 'Dinosauria' and a time span of 72.1 – 66.0 Ma. Critically, although studies on modern community associations are limited to relatively brief periods of sampling time, fossil assemblages are windows on the faunas of ancient worlds occurring within particular chronostratigraphic units (Benson et al. 2018). Although this coarse temporal resolution will undoubtedly confound the data (which is addressed in detail below), it would be problematic to subdivide the time bins further, not least because only a handful of fossil assemblages are sufficiently informative to provide confident community-level estimates so far (Vavrek & Larsson 2010). Additionally, due to an insufficient amount of comparative data within high–resolution time bins (Dean et al. 2020) and the inherent errors in radiometric dating (Gates et al. 2010), the creation of a more tightly constrained correlative window is presently impractical. Here, we only retained occurrences belonging to Ornithischia and Theropoda since these two clades were the most diverse and abundant non–avian dinosaur groups in the latest Cretaceous of North America (Brusatte et al. 2015). Generic–level identifications were used in our study, and all avian taxa were excluded when delineating community types to keep our data more comparable to previous works (e.g. Vavrek & Larsson 2010; Dean et al. 2020). While birds are phylogenetically part of the dinosaurian clade, the different habits and habitats of latest Cretaceous Avialae (either diving or volant taxa) separates these faunas enough from ground-dwelling dinosaurs to justify their functional distinction in the context of the communities modelled here (see Heino et al. 2015b for an example on present-day biotas). Although the value of generic taxonomic ranks in community analyses has been debated, palaeontologists have used generic–level clades to investigate distributional patterns and variation in community composition of fossil taxa (e.g. Vavrek & Larsson 2010; Chiarenza et al. 2019; Dean et al. 2020). Indeed, generic–level identifications are preferred over species taxonomic ranks in dinosaur palaeobiology studies as most dinosaur genera (c. 87%) are easily diagnosed and monospecific (Weishampel et al. 2004; Mannion et al. 2012). Moreover, genus-level and species–level diversity patterns generally appear to track each other for Mesozoic tetrapods (Barrett et al. 2009), and genera are more taxonomically stable than species for many groups (Robeck et al. 2000). Here, however, taxa with unclear genus identification were discarded (i.e. we did not incorporate 'cryptic' diversity represented by taxonomically undiagnostic fossil remains that potentially represent distinct taxa, nor we did infer ghost lineages based on phylogenetic diversity estimates; Barrett et al. 2009; Mannion et al. 2011), and so were collections lacking formational assignment. If questionable ages appeared (e.g. ages notably deviating from ages of other collections from the same formation), they were either revised or excluded. These data are an up–to–date record of North American dinosaur faunas and therefore incorporate new Late Cretaceous fossils discovered over the past few years. Overall, our pruned dataset comprised 43 dinosaur genera, and consisted of 11 formations across the WIB of North America and 17 well–sampled locations across the Hell Creek landscape. Palaeoclimatic general circulation model. In this study, we used palaeoclimatic model outputs (here, near-surface [1.5 m] mean annual temperature (TempMean), near-surface [1.5 m] annual temperature standard deviation (TempSDann), annual average precipitation (PrecMean) and annual precipitation standard deviation (PrecSDann)) from the fully coupled atmosphere-ocean GCM HadCM3L v. 4.5 Atmospheric–Ocean General Circulation Model (Valdes et al. 2017). More specifically, we followed the nomenclature of Valdes et al. (2017) and applied the HadCM3BL–M2.1aE version of the model. The conditions of the model simulations for the Maastrichtian consist of an atmospheric CO2 concentration of 1120 ppmv, which is within the range of uncertainty provided by the recent proxy pCO2 reconstructions of Foster et al. (2017). The model simulations were run for a total of 1422 years, and the climate variables used in our analyses were an annual average of the last 30 years of these simulations. HadCM3L has contributed to the Coupled Mode Intercomparison Project experiments demonstrating skill when it comes to reproducing present-day climates (Collins et al. 2001; Valdes et al. 2017) and has also been used for an array of different palaeoclimate evaluations during the Eocene (Lunt et al. 2012), the Oligocene (Li et al. 2018) and the Miocene (Bradshaw et al. 2012). Detailed information on this palaeoclimatic model, including large–scale circulation (and associated energy and momentum fluxes) and temporal fluctuations, as well as the impacts of fine-scale orographic features on climate signals, are available elsewhere (e.g. Lunt et al. 2016; Chiarenza et al. 2019). Palaeogeographical digital elevation models (DEMs). The Maastrichtian palaeogeography for this study is that of Scotese & Wright (2018), which has been compiled as a palaeo-digital elevation model to facilitate grid-based analyses. In brief, these maps were created from publicly available stratigraphic literature, supplemented by fieldwork, including lithology, palaeoenvironmental information and broad-scale facies identification. For large–scale analyses, these palaeogeographies were upscaled to the palaeoclimatic model resolution (3.75° x 2.5°). This means that topographic and bathymetric information was broadly conserved, as it was resolved at a lower resolution (see Chiarenza et al. 2019 for a similar approach). Functional features. Each dinosaur taxon was classified into several functional guilds based on body mass (very small, small, medium, large and very large), locomotor mode (bipeds, facultative bipeds –capable of both quadrupedal and bipedal motion– and quadrupeds) and trophic habits (carnivores, omnivores and herbivores, and for the latter, low and high browsers). Body mass is perhaps the single most important and meaningful functional trait for animals, as it ultimately affects many aspects of their biology including metabolic rates, mechanical constraints, ecological performance and lifestyle strategies related to feeding, locomotion and reproduction (Loeuille & Loreau 2006; Iossa et al. 2008). Here, we used body mass estimates (very small ≤ 10 kg; 10 kg 10000 kg; Noto & Grossman 2010) based on adult representatives from the comprehensive dataset of Benson et al. (2014), which provides a wide list of dinosaur taxa using the scaling relationship of limb bone robustness (stylopodial circumference; Campione & Evans 2012). To obtain a more comprehensive understanding of body mass distributions in our data, we further applied an inflection point criterion based on the Barry & Hartigan (1993) product partition model with Markov chain Monte Carlo (MCMC). More specifically, this algorithm used the posterior probability of changes over 10000 MCMC iterations, excluding the first 1000 as burn in, to distinguish among different body mass categories in the latest Cretaceous dinosaurs of North America. Interestingly, this Bayesian analysis roughly identified most of the original body mass categories used in our study, with each category broadly representing an order of magnitude (García–Girón et al. 2020b, appendix S1, fig. S1). Trophic habits refer to the food processing strategies and diet of an animal, and it generally includes three primary categories, i.e. carnivores, herbivores and omnivores. Further subdivisions depend on the biological knowledge of the morphology (e.g. teeth morphology and skull) and behaviour of the study organismal group. Here, we assigned herbivores to categories of browse height rather than plant type due to the virtually unknown nature of plant preferences in dinosaurs. More specifically, we roughly assigned a simple maximum browsing limit (low ≤ 2 m; high > 2 m) based on characters such as limb length and neck posture using Noto & Grossman (2010) and Mallon et al. (2013). We further divided locomotor mode into two major categories: quadrupeds and bipeds. For those taxa with intermediate axial and limb morphologies in proportions between those of bipeds and obligate quadrupeds (e.g. Hadrosauridae), we included an additional locomotor division, i.e. facultative bipeds (see Noto & Grossman, 2010 for a similar approach). For the following analyses, we applied the mixed–variables coefficient of distance (i.e. a generalisation of Gower's distance; Pavoine et al. 2009) to extract a functional distance matrix, which described the functional differences between all taxon pairs based on body mass, trophic habits and locomotor mode (e.g. Heino & Tolonen 2017). Thereafter, the pairwise output values for the functional distance matrix were synthesised into separate axes using principal coordinate analysis (PCO) and following Duarte et al. (2012). See the main text for References

Shifts in food webs and niche stability shaped survivorship and extinction at the end-Cretaceous

It has long been debated why groups such as non-avian dinosaurs became extinct whereas mammals and other lineages survived the Cretaceous/Paleogene mass extinction 66 million years ago. We used Markov networks, ecological niche partitioning, and Earth System models to reconstruct North American food webs and simulate ecospace occupancy before and after the extinction event. We find a shift in latest Cretaceous dinosaur faunas, as medium-sized species counterbalanced a loss of megaherbivores, but dinosaur niches were otherwise stable and static, potentially contributing to their demise. Smaller vertebrates, including mammals, followed a consistent trajectory of increasing trophic impact and relaxation of niche limits beginning in the latest Cretaceous and continuing after the mass extinction. Mammals did not simply proliferate after the extinction event; rather, their earlier ecological diversification might have helped them survive

100 million years of turtle paleoniche dynamics enable the prediction of latitudinal range shifts in a warming world

Past responses to environmental change provide vital baseline data for estimating the potential resilience of extant taxa to future change. Here, we investigate the latitudinal range contraction that terrestrial and freshwater turtles (Testudinata) experienced from the Late Cretaceous to the Paleogene (100.5-23.03 mya) in response to major climatic changes. We apply ecological niche modeling (ENM) to reconstruct turtle niches, using ancient and modern distribution data, paleogeographic reconstructions, and the HadCM3L climate model to quantify their range shifts in the Cretaceous and late Eocene. We then use the insights provided by these models to infer their probable ecological responses to future climate scenarios at different representative concentration pathways (RCPs 4.5 and 8.5 for 2100), which project globally increased temperatures and spreading arid biomes at lower to mid-latitudes. We show that turtle ranges are predicted to expand poleward in the Northern Hemisphere, with decreased habitat suitability at lower latitudes, inverting a trend of latitudinal range contraction that has been prevalent since the Eocene. Trionychids and freshwater turtles can more easily track their niches than Testudinidae and other terrestrial groups. However, habitat destruction and fragmentation at higher latitudes will probably reduce the capability of turtles and tortoises to cope with future climate changes

palaeoverse: A community‐driven R package to support palaeobiological analysis

1. The open-source programming language ‘R' has become a standard tool in the palaeobiologist's toolkit. Its popularity within the palaeobiological community continues to grow, with published articles increasingly citing the usage of R and R packages. However, there are currently a lack of agreed standards for data preparation and available frameworks to support the implementation of such standards. Consequently, data preparation workflows are often unclear and not reproducible, even when code is provided. Moreover, due to a lack of code accessibility and documentation, palaeobiologists are often forced to ‘reinvent the wheel’ to find solutions to issues already solved by other members of the community. 2. Here, we introduce palaeoverse, a community-driven R package to aid data preparation and exploration for quantitative palaeobiological research. The package is freely available and has three core principles: (1) streamline data preparation and analyses; (2) enhance code readability; and (3) improve reproducibility of results. To develop these aims, we assessed the analytical needs of the broader palaeobiological community using an online survey, in addition to incorporating our own experiences. 3. In this work, we first report the findings of the survey, which shaped the development of the package. Subsequently, we describe and demonstrate the functionality available in palaeoverse and provide usage examples. Finally, we discuss the resources we have made available for the community and our future plans for the broader Palaeoverse project. 4. palaeoverse is a community-driven R package for palaeobiology, developed with the intention of bringing palaeobiologists together to establish agreed standards for high-quality quantitative research. The package provides a user-friendly platform for preparing data for analysis with well-documented open-source code to enhance transparency. The functionality available in palaeoverse improves code reproducibility and accessibility, which is beneficial for both the review process and future research

Supplementary Information

Data on valid crocodylomorph species, completeness, crocodylomorph-bearing collections, and body size, as well as temporal and spatial series for crocodylomorph diversity, completeness, and samplin

Data from: Spatiotemporal sampling patterns in the 230 million year fossil record of terrestrial crocodylomorphs and their impact on diversity

The 24 extant crocodylian species are the remnants of a once much more diverse and widespread clade. Crocodylomorpha has an approximately 230 million year evolutionary history, punctuated by a series of radiations and extinctions. However, the group's fossil record is biased. Previous studies have reconstructed temporal patterns in subsampled crocodylomorph palaeobiodiversity, but have not explicitly examined variation in spatial sampling, nor the quality of this record. We compiled a dataset of all taxonomically diagnosable non‐marine crocodylomorph species (393). Based on the number of phylogenetic characters that can be scored for all published fossils of each species, we calculated a completeness value for each taxon. Mean average species completeness (56%) is largely consistent within subgroups and for different body size classes, suggesting no significant biases across the crocodylomorph tree. In general, average completeness values are highest in the Mesozoic, with an overall trend of decreasing completeness through time. Many extant taxa are identified in the fossil record from very incomplete remains, but this might be because their provenance closely matches the species’ present‐day distribution, rather than through autapomorphies. Our understanding of nearly all crocodylomorph macroevolutionary ‘events’ is essentially driven by regional patterns, with no global sampling signal. Palaeotropical sampling is especially poor for most of the group's history. Spatiotemporal sampling bias impedes our understanding of several Mesozoic radiations, whereas molecular divergence times for Crocodylia are generally in close agreement with the fossil record. However, the latter might merely be fortuitous, i.e. divergences happened to occur during our ephemeral spatiotemporal sampling windows

FIRST RECORD OF ICHTHYOSAURS IN SICILY(UPPER TRIASSIC OF MONTE SCALPELLO, CATANIA PROVINCE)

Here we report for the first time on the presence of ichthyosaurs in Sicily, southern Italy. The deposit of origin (Mufara Formation) can be dated to the upper Carnian (Tuvalian substage) based on a typical association of ammonites, one of which (Shastites sp.) is embedded in the sediment still encrusting one of the bone specimens recently found. The latter consist of two isolated vertebral centra that are referred to the Ichthyosauria thanks to their disk-like shape (i.e. they are much taller than long) combined with the amphicelous condition, lack of transverse processes, and presence of rib articulations on the central sides. The largest specimen is more precisely an anterior dorsal vertebra from an adult individual, ascribed to Shastasauridae indet. By the presence of elongated reniform diapophyseal facets, cranially not truncated, and absence of parapophyses. The smaller specimen represents an anterior cervical element from an immature individual of a likely smaller-sized, indeterminate taxon. These finds indicate that the biodiversity of the Monte Scalpello Triassic fauna is higher than previously known, but above all represent the southernmost occurrence of Triassic ichthyosaurs in the western Tethys basin

An Italian dinosaur Lagerstätte reveals the tempo and mode of hadrosauriform body size evolution

none7siDuring the latest Cretaceous, the European Archipelago was characterized by highly fragmented landmasses hosting putative dwarfed, insular dinosaurs, claimed as fossil evidence of the "island rule". The Villaggio del Pescatore quarry (north-eastern Italy) stands as the most informative locality within the palaeo-Mediterranean region and represents the first, multi-individual Konservat-Lagerstätte type dinosaur-bearing locality in Italy. The site is here critically re-evaluated as early Campanian in age, thus preceding the final fragmentation stages of the European Archipelago, including all other European localities preserving hypothesized dwarfed taxa. New skeletal remains allowed osteohistological analyses on the hadrosauroid Tethyshadros insularis indicating subadult features in the type specimen whereas a second, herein newly described, larger individual is likely somatically mature. A phylogenetic comparative framework places the body-size of T. insularis in range with other non-hadrosaurid Eurasian hadrosauroids, rejecting any significant evolutionary trend towards miniaturisation in this clade, confuting its 'pygmy' status, and providing unmatched data to infer environmentally-driven body-size trends in Mesozoic dinosaurs.noneChiarenza, Alfio Alessandro; Fabbri, Matteo; Consorti, Lorenzo; Muscioni, Marco; Evans, David C; Cantalapiedra, Juan L; Fanti, FedericoChiarenza, Alfio Alessandro; Fabbri, Matteo; Consorti, Lorenzo; Muscioni, Marco; Evans, David C; Cantalapiedra, Juan L; Fanti, Federic

The first juvenile dromaeosaurid (Dinosauria: Theropoda) from Arctic Alaska.

Compared to the osteological record of herbivorous dinosaurs from the Late Cretaceous Prince Creek Formation of northern Alaska, there are relatively fewer remains of theropods. The theropod record from this unit is mostly comprised of isolated teeth, and the only non-dental remains known can be attributed to the troodontid cf. Troodon and the tyrannosaurid Nanuqsaurus. Thus far, the presence of members of Dromaeosauridae has been limited to isolated teeth. Here we describe a symphyseal portion of a small dentary with two ziphodont teeth. Based on tooth shape, denticle morphology, and the position of the Meckelian groove, we attribute this partial dentary to a saurornitholestine dromaeosaurid. The fibrous bone surface, small size, and higher number of mesial denticles compared to distal ones point to a juvenile growth stage for this individual. Multivariate comparison of theropod teeth morphospace by means of principal component analysis reveals an overlap between this dentary and Saurornitholestinae dromaeosaurid morphospace, a result supported by phylogenetic analyses. This is the first confirmed non-dental fossil specimen from a member of Dromaeosauridae in the Arctic, expanding on the role of Beringia as a dispersal route for this clade between Asia and North America. Furthermore, the juvenile nature of this individual adds to a growing body of data that suggests Cretaceous Arctic dinosaurs of Alaska did not undergo long-distance migration, but rather they were year-round residents of these paleopolar latitudes