Vertebrate Palaeontology

Los ceratópsidos son el grupo más diverso además de ser componentes característicos y abundantes de las asociaciones de dinosaurios del oeste de Norte América (Laramidia) durante el Cretácico Tardío. Estratos del Campaniano han producido numerosos especímenes tanto de centrosaurinos como de chasmosaurinos, principalmente de Canadá y Estados Unidos. En contraste, el registro de la parte sur de Laramidia es sorprendentemente escaso. Restos de ceratópsidos son extremadamente raros en el Cretácico Tardío de México, contrastando con las asociaciones más ricas de hadrosaurios. Sin embargo, restos de dinosaurios han sido reportados de estratos mexicanos, aunque la mayoría de este material no es diagnóstico, y solamente dos taxones, Yehuecauhceratops mudei y Coahuilacertops magnacuerna, provenientes de las formaciones Aguja y Cerro del Pueblo (Campaniano) respectivamente, han sido nombrados.

This paper looks into the relation between orbital and radiometric dating and tries to locate the geographic area from which genomic changes, opposite in nature to the common understanding today, occurred. It assumes guesstimates for dinosaur lifespans ca. 80 years. It draws a surprising conclusion.

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.

Assessments of dinosaur macroevolution at any given time can be biased by the historical publication record. Recent studies have analysed patterns in dinosaur diversity that are based on secular variations in the numbers of published taxa. Many of these have employed a range of approaches that account for changes in the shape of the taxonomic abundance curve, which are largely dependent on databases compiled from the primary published literature. However, how these ‘corrected’ diversity patterns are influenced by the history of publication remains largely unknown. Here, we investigate the influence of publication history between 1991 and 2015 on our understanding of dinosaur evolution using raw diversity estimates and shareholder quorum subsampling for the three major subgroups: Ornithischia, Sauropodomorpha, and Theropoda. We find that, while sampling generally improves through time, there remain periods and regions in dinosaur evolutionary history where diversity estimates are highly volatile (e.g. the latest Jurassic of Europe, the mid-Cretaceous of North America, and the Late Cretaceous of South America). Our results show that historical changes in database compilation can often substantially influence our interpretations of dinosaur diversity. ‘Global’ estimates of diversity based on the fossil record are often also based on incomplete, and distinct regional signals, each subject to their own sampling history. Changes in the record of taxon abundance distribution, either through discovery of new taxa or addition of existing taxa to improve sampling evenness, are important in improving the reliability of our interpretations of dinosaur diversity. Furthermore, the number of occurrences and newly identified dinosaurs is still rapidly increasing through time, suggesting that it is entirely possible for much of what we know about dinosaurs at the present to change within the next 20 years.

We describe the partially preserved femur of a large-bodied theropod dinosaur from the Cenomanian “Kem Kem Compound Assemblage” (KKCA) of Morocco. The fossil is housed in the Museo Geologico e Paleontologico “Gaetano Giorgio Gemmellaro” in Palermo (Italy). The specimen is compared with the theropod fossil record from the KKCA and coeval assemblages from North Africa. The combination of a distally reclined head, a not prominent trochanteric shelf, distally placed lesser trochanter of stout, alariform shape, a stocky shaft with the fourth trochanter placed proximally, and rugose muscular insertion areas in the specimen distinguishes it from Carcharodontosaurus, Deltadromeus and Spinosaurus and supports referral to an abelisaurid. The estimated body size for the individual from which this femur was derived is comparable to Carnotaurus and Ekrixinatosaurus (up to 9 meters in length and 2 tons in body mass). This find confirms that abelisaurids had reached their largest body size in the “middle Cretaceous,” and that large abelisaurids coexisted with other giant theropods in Africa. We review the taxonomic status of the theropods from the Cenomanian of North Africa, and provisionally restrict the Linnean binomina Carcharodontosaurus iguidensis and Spinosaurus aegyptiacus to the type specimens. Based on comparisons among the theropod records from the Aptian-Cenomanian of South America and Africa, a partial explanation for the so-called “Stromer’s riddle” (namely, the coexistence of many large predatory dinosaurs in the “middle Cretaceous” record from North Africa) is offered in term of taphonomic artifacts among lineage records that were ecologically and environmentally non-overlapping. Although morphofunctional and stratigraphic evidence supports an ecological segregation between spinosaurids and the other lineages, the co-occurrence of abelisaurids and carcharodontosaurids, two groups showing several craniodental convergences that suggest direct resource competition, remains to be explained.

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.

The “Bonaventura Gravina” Collection of the Earth Science Museum of Catania (Italy) includes an ichthyosaur specimen of unknown geographic and stratigraphic provenance, age, and taxonomic determination. On comparison with other fossils from the same collection it was established that the specimen is from Böll, southwestern Germany; the ammonites preserved on the same slab indicate an early Toarcian age. Based on the available information it is suggested that it comes from the Early Jurassic Posidonia Shale (Posidonienschiefer), which is known worldwide for its ichthyosaur remains. A morphological comparison with Toarcian ichthyosaurs allowed the fossil remains to be referred to an adult specimen of Stenopterygius, a mid-sized ichthyosaur genus common in the Toarcian of Southern Germany. The phylogenetic analysis by parsimony supports this conclusion.

La histología ósea concede una visión sustancial del crecimiento y biología de los vertebrados fósiles. Muchos de los mayores clados de dinosaurios no avianos han sido extensivamente muestreados para datos de osteología ósea permitiendo la reconstrucción de su crecimiento así como una evaluación de la evolución de sus cambios de crecimiento a lo largo de su filogenia.

Resumen El trabajo de Alfredo Dugès relacionado con el estudio del registro fósil representa un importante ejemplo del estado de la Paleontología como ciencia durante la segunda mitad del siglo xix. La información que se encuentra en los dos textos que escribió so-bre Zoología refleja su visión de la importancia del registro fósil como complemento en el estudio de aspectos muy diversos de la biología de los animales y como herramien-ta que permite conocer su historia a través del tiempo geológico. Los cuatro artículos en que describe registros fósiles del Altiplano de México son referencias obligadas para estudiosos de vertebrados del Plioceno y Pleistoceno de México y son trabajos que de-muestran la gran formación de naturalista que Dugès adquirió en un ambiente inte-lectual cosmopolita, caracterizado por importantes descubrimientos y el desarrollo de grandes ideas y teorías sobre la naturaleza. Résumé Les travaux de Alfredo Dugès liés à l'étude du registre fossile, représentent un exemple important de l'état de la paléontologie comme une science au cours de la seconde moitié du xixe siècle. L'information contenue dans les deux textes de zoologie qu'il a écrit reflète ses vues sur l'importance du registre fossile comme un complément des études de très nombreux aspects de la biologie des animaux et aussi comme un outil qui permet de connaitre l'histoire à travers du temps géologique. Les quatre publications décrivant le registre fossile du Plateau Mexicain sont références obligées pour les chercheurs de vertébrés du Pliocène et Pléistocène du Mexique, et sont des oeuvres qui représentent la grande formation de naturaliste que Dugès a acquis dans un envi-ronnement intellectuel cosmopolite, caractérisé par d'importantes découvertes et le développement de grandes idées et théories sur la nature. Abstract Alfredo Dugès' work on the fossil record is an important indicator of the state of the Paleontology as a science during the second half of the nineteenth century. The two

Strisores is a clade of neoavian birds that include diurnal aerial specialists such as swifts and hummingbirds, as well as several predominantly nocturnal lineages such as nightjars and potoos. Despite the use of genome-scale molecular datasets, the phylogenetic interrelationships among major strisorean groups remain controversial. Given the availability of next-generation sequence data for Strisores and the clade's rich fossil record, we reassessed the phylogeny of Strisores by incorporating a large-scale sequence dataset with anatomical data from living and fossil strisoreans within a Bayesian total-evidence framework. Combined analyses of molecular and morphological data resulted in a phylogenetic topology for Strisores that is congruent with the findings of two recent molecular phylogenomic studies, supporting nightjars (Caprimulgidae) as the extant sister group of the remainder of Strisores. This total-evidence framework allowed us to identify morphological synapomorphies for strisorean clades previously recovered using molecular-only datasets. However, a combined analysis of molecular and morphological data highlighted strong signal conflict between sequence and anatomical data in Strisores. Furthermore, simultaneous analysis of molecular and morphological data recovered differing placements for some fossil taxa compared with analyses of morphological data under a molecular scaffold, highlighting the importance of analytical decisions when conducting morphological phylogenetic analyses of taxa with molecular phylogenetic data. We suggest that multiple strisorean lineages have experienced convergent evolution across the skeleton, obfuscating the phylogenetic position of certain fossils, and that many distinctive specializations of strisorean subclades were acquired early in their evolutionary history. Despite this apparent complexity in the evolutionary history of Strisores, our results provide fossil support for aerial foraging as the ancestral ecological strategy of Strisores, as implied by recent phylogenetic topologies derived from molecular data.

Synopsis The field of comparative morphology has entered a new phase with the rapid generation of high-resolution three-dimensional (3D) data. With freely available 3D data of thousands of species, methods for quantifying morphology that harness this rich phenotypic information are quickly emerging. Among these techniques, high-density geometric morphometric approaches provide a powerful and versatile framework to robustly characterize shape and phenotypic integration, the covariances among morphological traits. These methods are particularly useful for analyses of complex structures and across disparate taxa, which may share few landmarks of unambiguous homology. However, high-density geometric morphometrics also brings challenges, for example, with statistical, but not biological, covariances imposed by placement and sliding of semilandmarks and registration methods such as Procrustes superimposition. Here, we present simulations and case studies of high-density datasets for squamates, birds, and caecilians that exemplify the promise and challenges of high-dimensional analyses of phenotypic integration and modularity. We assess: (1) the relative merits of "big" high-density geometric morphometrics data over traditional shape data; (2) the impact of Procrustes superimpo-sition on analyses of integration and modularity; and (3) differences in patterns of integration between analyses using high-density geometric morphometrics and those using discrete landmarks. We demonstrate that for many skull regions, 20-30 landmarks and/or semilandmarks are needed to accurately characterize their shape variation, and landmark-only analyses do a particularly poor job of capturing shape variation in vault and rostrum bones. Procrustes superimposition can mask modularity, especially when landmarks covary in parallel directions, but this effect decreases with more biologically complex covariance patterns. The directional effect of landmark variation on the position of the centroid affects recovery of covariance patterns more than landmark number does. Landmark-only and landmark-plus-sliding-semilandmark analyses of integration are generally congruent in overall pattern of integration, but landmark-only analyses tend to show higher integration between adjacent bones, especially when landmarks placed on the sutures between bones introduces a boundary bias. Allometry may be a stronger influence on patterns of integration in landmark-only analyses, which show stronger integration prior to removal of allometric effects compared to analyses including semilandmarks. High-density geometric morphometrics has its challenges and drawbacks, but our analyses of simulated and empirical datasets demonstrate that these potential issues are unlikely to obscure genuine biological signal. Rather, high-density geometric morphometric data exceed traditional landmark-based methods in characterization of morphology and allow more nuanced comparisons across disparate taxa. Combined with the rapid increases in 3D data availability, high-density morphometric approaches have immense potential to propel a new class of studies of comparative morphology and phenotypic integration.

Aim: We use cluster analysis to delimit climatically and functionally distinct mam-malian faunal clusters. These entities form regional species pools and are relevant to community assembly processes. Similar clusters can be differentiated in the fossil record, offering the potential for use as palaeoenvironmental proxies.

Evolution is a fundamentally population level process in which variation, drift and selection produce both temporal and spatial patterns of change. Statistical model fitting is now commonly used to estimate which kind of evolutionary process best explains patterns of change through time using models like Brownian motion, stabilizing selection (Ornstein-Uhlenbeck) and directional selection on traits measured from stratigraphic sequences or on phylogenetic trees. But these models assume that the traits possessed by a species are homogeneous. Spatial processes such as dispersal, gene flow and geographical range changes can produce patterns of trait evolution that do not fit the expectations of standard models, even when evolution at the local-population level is governed by drift or a typical OU model of selection. The basic properties of population level processes (variation, drift, selection and population size) are reviewed and the relationship between their spatial and temporal dynamics is discussed. Typical evolutionary models used in palaeontology incorporate the temporal component of these dynamics, but not the spatial. Range expansions and contractions introduce rate variability into drift processes, range expansion under a drift model can drive directional change in trait evolution, and spatial selection gradients can create spatial variation in traits that can produce long-term directional trends and punctuation events depending on the balance between selection strength, gene flow, extirpation probability and model of speciation. Using computational modelling that spatial processes can create evolutionary outcomes that depart from basic population-level notions from these standard macroevolutionary models.

Ecometrics is a trait-based approach to study ecosystem variability through time. An ecometric value is derived from describing the distribution of functional traits at the community level, which may arise by environmental filtering, extinction, or convergence. An ecometric relationship describes the correspondence between spatially explicit ecometric values and corresponding environmental variation. Transfer functions and maximum likelihood approaches have been developed with modern trait-environment relationships to reconstruct paleotemperature, paleoprecipitation, and paleovegetation cover given the distribution of functional traits within a community. Because the focus for this approach is on the traits and not on species, it is transferable through space and time and can be used to compare novel communities. In this paper we review the concepts and history of ecometric analysis and then describe practical methods for implementing an ecometric study.