Paleobiology

The palaeoecology of the primitive, limbed snake Pachyrhachis is reevaluated. Previously considered to have been preserved in a shallow bay with a nearby freshwater source, it is here demonstrated to have inhabited an inter‐reef basin. Evidence for this comes from the position of the nearest palaeoshoreline (450 km away), the finely laminated carbonate mudstones, and the absence of bioturba‐tion, alluvium, and unequivocally terrestrial or freshwater taxa. Marine adaptations of Pachyrhachis include the laterally compressed body and heavily ossified (pachyostotic) vertebrae and ribs. Hydrodynamic considerations indicate that it was a slow swimmer, and thus an ambush rather than pursuit predator. Morphology of the anterior vertebrae suggests that the strike muscles were well‐developed. The narrow head and neck might have been adaptations to reduce water resistance during rapid lunges, and/or to forage in burrows or tight crevices.

The late Pleistocene megafaunal extinctions may have been the first extinctions directly related to human activity, but in North America the close temporal proximity of human arrival and the Younger Dryas climate event has hindered efforts to identify the ultimate extinction cause. Previous work evaluating the roles of climate change and human activity in the North American megafaunal extinction has been stymied by a reliance on geographic binning, yielding contradictory results among researchers. We used a fine-scale geospatial approach in combination with 95 megafaunal last-appearance and 75 human first-appearance radiocarbon dates to evaluate the North American megafaunal extinction. We used kriging to create interpolated first- and last-appearance surfaces from calibrated radiocarbon dates in combination with their geographic autocorrelation. We found substantial evidence for overlap between megafaunal and human populations in many but not all areas, in some cases exceeding 3000...

Xiphosurids are an archaic group of aquatic chelicerate arthropods, generally known by the colloquial misnomer of ‘horseshoe crabs’. Known from marine envi- ronments as far back as the early Ordovician, horseshoe crabs are generally considered ‘living fossils’ – descendants of a bradytelic lineage exhibiting little morphological or ecological variation throughout geological time. However, xiphosurids are known from freshwater sediments in the Palaeozoic and Mesozoic; furthermore, the contention that xiphosurids show little morphological variation has never been tested empirically. Attempts to test this are hampered by the lack of a modern phylogenetic framework with which to explore different evolutionary scenarios. Here, I present a phylogenetic analysis of Xiphosurida and explore patterns of morphospace and environmental occupation of the group throughout the Phanerozoic. Xiphosurids are shown to have invaded non-marine environments indepen- dently at least five times throughout their evolutionary history, twice resulting in the radiation of major clades – bellinurines and austrolimulids – that occupied novel regions of morphospace. These clades show a convergent ecological pattern of differentiation, speciation and subse- quent extinction. Horseshoe crabs are shown to have a more dynamic and complex evolutionary history than previ- ously supposed, with the extant species representing only a fraction of the group’s past ecological and morphological diversity.

"The principal conch parameters—whorl expansion rate, whorl overlap rate, umbilical
width, and whorl thickness—of Early and Middle Devonian ammonoids have been extensively investigated.
Stratophenetic analyses show long-term trends in the transformations of these characters
over long periods of time, but sudden and rapid reversals can also be observed. On the basis
of these four quantifiable conch parameters and supplementary qualitative characters, ten ammonoid
morphs were distinguished. Reconstruction of the evolutionary history of these morphs
reflects the existence of two major phylogenetic lineages, both already visible in Early Devonian
faunas. The agoniatitid lineage is characterized by slow character development and leads to the
Frasnian gephuroceratids; the anarcestid lineage displays rapidmorphological evolution that leads
to the late Givetian pharciceratids as well as the Middle and Late Devonian tornoceratids. Morphological
evolution is interpreted as partly limited by geometrical and physical constraints."

Spiral-shaped foraging trace fossils, assigned to the graphoglyptid cf. Spirorhaphe azteca, are reported from an Early Permian intertidal flat in the Robledo Mountains of southern New Mexico, USA. Remarkably similar spiral-shaped structures are produced in modern intertidal flats by the paraonid polychaete Paraonis fulgens, and function as traps to capture mobile microorganisms migrating in the sediment in response to tides. We envisage a similar function for the Early Permian trace fossils. Previous studies have suggested that the lack of P. fulgens–type traces from ancient intertidal deposits indicates that such behavior only evolved geologically recently in such settings. However, this report demonstrates that such specialized foraging behavior was present in intertidal settings by at least the Early Permian. Graphoglyptids are typical of deep-marine settings, and characteristic of the Nereites ichnofacies. This represents their first undoubted occurrence in intertidal facies in the geological record. We postulate that the occurrence of graphoglyptids in deep-marine and intertidal settings is related to the predictability of resources. The scarcity of intertidal graphoglyptids in the geological record is most likely a preservational effect.

Tyrannosaurs, the group of dinosaurian carnivores that includes Tyrannosaurus rex and its closest relatives, are icons of prehistory. They are also the most intensively studied extinct dinosaurs, and thanks to large sample sizes and an influx of new discoveries, have become ancient exemplar organisms used to study many themes in vertebrate paleontology. A phylogeny that includes recently described species shows that tyrannosaurs originated by the Middle Jurassic but remained mostly small and ecologically marginal until the latest Cretaceous. Anatomical, biomechanical, and histological studies of T. rex and other derived tyrannosaurs show that large tyrannosaurs could not run rapidly, were capable of crushing bite forces, had accelerated growth rates and keen senses, and underwent pronounced changes during ontogeny. The biology and evolutionary history of tyrannosaurs provide a foundation for comparison with other dinosaurs and living organisms.

La paléontologie a connu au cours du XX e siècle une « révolution paléobiologique » (Sepkoski et Ruse, 2009), en se constituant comme science théorique et intégrée à la biologie de l'évolution. Si l'histoire de la paléoanthropologie reflète un tournant similaire, la révolution paléobiologique reste, à plusieurs égards, inachevée dans cette discipline. Cet article analyse les causes de cet inachèvement, en identifiant des limites empiriques, relatives aux particularités du registre fossile de la paléoanthropologie, mais aussi des limites épistémologiques, rapportées à différentes conceptions de la paléobiologie en jeu dans cette discipline. Nous montrons enfin qu'il est nécessaire de prendre en considération la spécificité anthropologique de la discipline pour apprécier la particularité du tournant paléobiologique dans le champ de l'évolution humaine. Abstract Paleontology underwent a "paleobiological revolution" during the twentieth century (Sepkoski and Ruse, 2009), by becoming a theoretical science and a part of evolutionary biology. Although the history of paleoanthropology reflects a similar change, the paleobiological revolution is still incomplete in this field. This article explains why the change is only partial. We identify empirical limits, pertaining to the distinctive features of the fossil record in paleoanthropology, as well as epistemological limits, linked with several different understandings of what paleobiology means. Finally, we demonstrate that there is a need to consider paleoanthropology as being not only a branch of paleobiology, but also an anthropology. By doing so, it is possible to assess properly the paleobiological change in the field of human evolution.

More than 800 isolated teeth of fossil Pongo have been recovered from cave sites in the vicinity of Chongzuo in Guangxi, southern China, ranging from the Early to Late Pleistocene (2.0e0.1 Ma). These collections provide a unique regional window into the evolutionary history of orangutans over a twomillion-year period at the northernmost extent of their former geographic range. Here we investigate the nature and timing of the evolutionary change in the dental size of fossil orangutans from Chongzuo. Fossil tooth size (mesiodistal length*buccolingual breadth) was compared against an extant Pongo pygmaeus standard (n ¼ 106 individuals). During the course of the Pleistocene, orangutans from southern China exhibited a progressive reduction in overall dental size. Early Pleistocene Pongo has cheek teeth with occlusal areas that are 38.1% larger than those of extant P. pygmaeus. Those from the Middle and Late Pleistocene are 25.2% and 18.9% larger, respectively. Previously, the size difference in dentition between the Early to Middle Pleistocene and Middle to Late Pleistocene samples was used to differentiate time-successive species of Pongo, namely Pongo weidenreichi and Pongo devosi. However, with access to larger samples and better representation of populations through time, the evidence in support of this taxonomic arrangement requires reconsideration. Diminution of the teeth now appears to be a gradual evolutionary transformation rather than a punctuated event. Moreover, the morphological features that distinguish the Chongzuo fossil orangutans from extant Pongo spp. remain uniform throughout the Pleistocene. Retaining P. weidenreichi and P. devosi as anagenetic species remains an option, but, given the current evidence, we consider it preferable to assign all of the fossil orangutans from Chongzuo to P. weidenreichi. Beyond resolving questions of alpha taxonomy, the study of fossil orangutan dental size provides a basis for estimating body mass, which has implications for interpreting the paleobiology of Pleistocene Pongo in southern China.

Diprotodon Owen, was one of the first fossil mammals described from Australia and has the distinction of being the largest ever marsupial. However, until recently its taxonomy was unclear and knowledge of its continental distribution, palaeoecology and evolution was poorly known. This paper describes cranial elements from an unusually small-bodied Diprotodon from the Early Pleistocene Nelson Bay Formation, Portland, Australia. It is intermediate in size between the smaller-bodied Pliocene ancestor, Euryzygoma dunense de Vis 1895 and the larger-bodied Late Pleistocene D. optatum Owen, . However, it is morphologically inseparable from Late Pleistocene Diprotodon and is here referred to as D. ?optatum. A temporal morphocline most parsimoniously explains the medium body size of the Nelson Bay taxon; thus we provide the first evidence of a transitional form within Diprotodon. The cause(s) of gigantism of the E. dunense-D. ?optatum-D. optatum lineage through the late Cainozoic is unclear but most likely involved the physiological response to changes in the physical and/or biotic environment. Although the size changes within the lineage may have been initially advantageous, they were most likely disadvantageous when the optimum body size was obtained. Our results suggest that Diprotodon was at its largest ever body size during the Late Pleistocene - the time period that coincided with its extinction.

The Expo / Mammoth 2010 is a cultural product derivative of the interdisciplinary project "Study of the Pleistocene megafauna in Guerrero Creek. Guadalupe, Zacatecas. First field season: surface collection at the study area and stratigraphic controlled collecting at the site Puente Calabacillas, approved by the National Council of Archaeology (National Institute of Anthropology and History)
The first objective of the exhibition is based in a holistic, interdisciplinary develop an approach around the settlement
of the first human groups and mega Pleistocene fauna in the north central region Mexico. By documenting particular
ecological characteristics of some species animals, and explains the possible circumstances that caused the extinction of the megafauna. The second objective is based on restoring
scientific research in the process of classification and ordering information paleontological excavations provide.

We believe that punctuational change dominates the history of life: evolution is concentrated in very rapid events of speciation (geologically instantaneous, even if tolerably continuous in ecological time). Most species, during their geological history, either do not change in any appreciable way, or else they fluctuate mildly in morphology, with no apparent direction. Phyletic gradualism is very rare and too slow, in any case, to produce the major events of evolution. Evolutionary trends are not the product of slow, directional transformation within lineages; they represent the differential success of certain species within a clade—speciation may be random with respect to the direction of a trend (Wright's rule).As an a priori bias, phyletic gradualism has precluded any fair assessment of evolutionary tempos and modes. It could not be refuted by empirical catalogues constructed in its light because it excluded contrary information as the artificial result of an imperfect fossi...

This study aims to trace changes in the River Nile flows over the Late Quaternary and is based on palynomorphs which were embedded in the sea floor of the Levantine Basin. The palynomorphs were extracted from two marine sediment cores, which cover the last 86 ka and are located at the two ends of the Levantine Basin: MD-9509, at the southern part of the Levantine Basin, and MD-9501, at its northern part. Core MD-9509 was taken from the Nile cone and is characterized by high sedimentation rates and a good state of palynomorph preservation. The assemblages included palynomorphs which were transported via the Nile headwaters and therefore enabled the reconstruction of the River Nile flows. The results demonstrate that the last glacial period (~75e16 ka) was characterized by a decrease in Nile water discharge and an increase in sediment influx, while opposite trends were observed prior to the last glacial period as well as during the deglaciation and the Holocene. Based on the study of the spores, it is suggested that during the last glacial, the main contributors of freshwater and sediment load to the Eastern Mediterranean Sea were the Blue Nile and the Atbara and only during interglacials was there a more significant contribution of the White Nile. Within the northern core, MD-9501, pollen was preserved only during the formation of sapropels S3 and S1. The comparison of the sapropelic palynological spectra in both core sites clearly indicates that during sapropel deposition, climate conditions were more humid in the Northern Levant, reflecting the north-south regional Mediterranean climatic moisture gradient. Sapropel formation was a result of the intensification of the monsoonal climate system which was most probably related to the maximum insolation values at 65 N, while, currently, the Atlantic is the main influencing climate system in the region. One of the most interesting observations in this study is that during Heinrich Events H2-H6, which originated in the north Atlantic and were identified in MD-9509 based on minimum arboreal pollen percentages, pollen originating from tropical regions was not embedded in the Levantine Basin. These results lend support to the view that episodes of dryness in tropical/sub-tropical Eastern Africa were associated not only with low-latitude climate controls, but also with high-latitude glacial stress.

Glyptodont clavipes (Cingulata, Glyptodontidae) was a massive mammal with a rigid carapace for which bipedalism has been proposed. In this work, bipedal posture is explored by way of a biomechanical model that has been previously tested in extant mammals, and the predictions are supported with biomechanical and morphofunctional approaches. I show that G. clavipes could adopt a bipedal posture rest its mass on the hind limbs while maintaining its trunk in a horizontal position, leaving forelimb free of its body support function. This work clarifies the bipedalism of G. clavipes and discusses its biological importance for locomotion and other biological functions. Additionally, limb and body proportions needed to adopt bipedal stance in quadruped mammals, and a model that may be used to interpret bipedal postures in extant and fossil mammals is given, thus offering a new means to study bipedalism.

See what modern science has to say about eating animal products. Find out once and for all if meat is bad for you or good for you. You'll also learn from the science what a healthy diet should consist of. Chapters were added covering sodium in the diet, walking, and optimal exercising practices.

When studying an extinct species such as the cave bear (Ursus spelaeus ROSENMÜLLER 1794), it is possible to apply a variety of molecular biology techniques such as the study of stable isotopes or mitochondrial DNA (mDNA) to infer patterns of behaviour or physiology that would otherwise remain concealed. Throughout Europe and along time, differences in the isotopic values (δ 13 C and δ 15 N) of cave bears arise from environmental differences and the Pleistocene climatic evolution. The climate determines the hibernation length, during which the cave bears undergo a particular physiology that can be related to an increase in δ 15 N during climate cooling. In order to verify whether hibernation affected the isotopic values, we compared cave bears in different ontogenetic stages. The results show that perinatal values reflect the values for mothers during hibernation, while juveniles show differences in maternal investment. A previous study in the literature based on complete mitochondrial DNA sequences of several individuals collected from closely situated caves showed that each cave housed, almost exclusively, a single lineage of haplotypes. This pattern suggests extreme fidelity to the birth site, or homing behaviour, and that cave bears formed stable maternal social groups, at least for the purpose of hibernation. Studies of this type offer unexpected data on the palaeobiology of this extinct animal.

Exceptionally preserved fossils provide crucial insights into extinct body plans and organismal evolution. Molluscs, one of the most disparate animal phyla, radiated rapidly during the early Cambrian period (approximately 535–520 million years ago (Ma)). The problematic fossil taxa Halkieria and Orthrozanclus (grouped in Sachitida) have been assigned variously to stem-group annelids, brachiopods , stem-group molluscs or stem-group aculiferans (Polyplacophora and Aplacophora), but their affinities have remained controversial owing to a lack of preserved diagnostic characters. Here we describe a new early sachitid, Calvapilosa kroegeri gen. et sp. nov. from the Fezouata biota of Morocco (Early Ordovician epoch, around 478 Ma). The new taxon is characterized by the presence of a single large anterior shell plate and polystichous radula bearing a median tooth and several lateral and uncinal teeth in more than 125 rows. Its flattened body is covered by hollow spinose sclerites, and a smooth, ventral girdle flanks an extensive mantle cavity. Phylogenetic analyses resolve C. kroegeri as a stem-group aculiferan together with other single-plated forms such as Maikhanella (Siphogonuchites) and Orthrozanclus; Halkieria is recovered closer to the aculiferan crown. These genera document the stepwise evolution of the aculiferan body plan from forms with a single, almost conchiferan-like shell through two-plated taxa such as Halkieria, to the eight-plated crown-group aculiferans. C. kroegeri therefore provides key evidence concerning the long debate about the crown molluscan affinities of sachitids. This new discovery strongly suggests that the possession of only a single calcareous shell plate and the presence of unmineralised sclerites are plesiomorphic (an ancestral trait) for the molluscan crown.

Course name: Introduction to the Paleontology and Paleoanthropology of Spain

Saint Louis University, Madrid Campus, Faculty: Science and Engineering
Semester:  Spring 2005.

Course description: This course gives an introduction into the Paleontology and Paleoanthropology of Spain. Basic principles and methods of Paleontology and Paleoanthropology will be outlined. Especially presented will be the origins of life and human beings, evolution, and extinctions. The paleontological part will concentrate on some interesting Spanish case studies (reefs of the Devonian period, swamp forests of the Carboniferous period, shallow sea of the Jurassic period, dinosaurs from the Upper Jurassic and Lower Cretaceous, and mammals and insects of the Tertiary period). In the center of the paleoanthropological part will be the famous findings of Homo antecessor and Homo heidelbergensis in the caves of Atapuerca and their importance for our knowledge about Human evolution.

Course Calendar:
Monday, Jan. 17: 1. Introduction – What are Fossils?
Wednesday, Jan. 19: 2. The Geologic Time Scale
Monday, Jan. 24, & Wednesday, Jan. 26: 3. Evolution and Taxonomy – Biology and Paleontology in Dialogue (I)
Thursday, Jan. 27: End of DROP/ADD period
Monday, Jan. 31, & Wednesday, Feb. 2: 3. Evolution and Taxonomy – Biology and Paleontology in Dialogue (II) & 4. Biogeography and Mass Extinctions (I)
Monday, Feb. 7: 4. Biogeography and Mass Extinctions (II)
Wednesday, Feb. 9: 5. From the Origins of Life to the Silurian
Monday, Feb. 14: Review & Preparation of first mid-term exam
Monday, Feb. 14: Deadline for the submission of the title of the paper
Wednesday, Feb. 16: First mid-term exam.
Monday, Feb. 21: 6. Reefs of the Devonian Period
Wednesday, Feb. 23: 7. Swamp Forests of the Carboniferous Period (I)
Monday, Feb. 28: 7. Swamp Forests of the Carboniferous Period (II) & 8. Reptiles of the Triassic Period
Wednesday, Mar. 2: 9. Life of the Shallow Sea of the Jurassic Period (I)
Saturday, Mar. 5, to Sunday, Mar. 13: SPRING BREAK
Monday, Mar. 14: 9. Life of the Shallow Sea of the Jurassic Period (II)
Wednesday, Mar. 16: 10. Dinosaurs from the Upper Jurassic and Cretaceous (I)
Monday, Mar. 21: 10. Dinosaurs from the Upper Jurassic and Cretaceous (II)
Wednesday, Mar. 23: 11. Fossils of the Tertiary Period
Thursday, Mar. 24, to Sunday, Mar. 27: Easter
Monday, Mar. 28: Review & Preparation of second mid-term exam
Wednesday, Mar. 30: Second mid-term exam
Monday, Apr. 4: Deadline for the submission of papers and PowerPoint presentations
Monday, Apr. 4, & Wednesday, Apr. 6: 12. Outline of Human evolution.
Friday, Apr. 8: Last day to drop a class and receive a grade of "W"
Monday, Apr. 11, & Wednesday, Apr. 13: 13. The Earliest Man in Spain – the Homo from Orce. & 14. Homo antecessor and Homo heidelbergensis from the Caves of Atapuerca (Prov. Burgos) (I)
Saturday, Apr. 16: Field trip to Guadalajara
Monday, Apr. 18: 14. Homo antecessor and Homo heidelbergensis from the Caves of Atapuerca (Prov. Burgos) (II)
Wednesday, Apr. 20: 15. The Humans after Homo heidelbergensis in Spain.
Monday, Apr. 25, & Wednesday, Apr. 27: Presentation of papers