Fossils

Although fossils of Trionychidae are found as far back as the Early Cretaceous, their evolutionary history, including the origin of the crown clade, is poorly understood. Here, we use a microCT scan of the skull of ‘Trionyx’ kyrgyzensis from the late Early Cretaceous (Albian) of Kyrgyzstan as the basis for a thorough redescription of the cranial morphology of this species. New information includes the pattern of cranial circulation, which is comparable to all extant trionychids. A unique combination of cranial and postcranial characters of ‘Trionyx’ kyrgyzensis allows us to establish for it a new genus Petrochelys gen. nov. The data regarding Petrochelys kyrgyzensis are incorporated into a phylogenetic analysis. When Petrochelys kyrgyzensis is analysed without including additional, extinct taxa, it is placed in a highly derived position within the extant Nilssonia. However, the addition of five Cretaceous–Palaeogene taxa breaks up hypothesized long branches and results in more basal positions for Petrochelys kyrgyzensis within recovered trees. All results support the hypothesis that Petrochelys kyrgyzensis is a crown trionychid and a member of Trionychinae. Our findings highlight the importance of including multiple extinct taxa in phylogenetic analyses prior to using any of those taxa as calibration points in divergence dating estimates. https://zoobank.org/urn:lsid:zoobank.org:pub:592B98BF-87DF-48A8-8AA2-543AAD21FC95

An extremely well-preserved dinosaur ( Cf. Edmontosaurus sp.) found in the Hell Creek Formation (Upper Cretaceous, North Dakota) retains soft-tissue replacement structures and associated organic compounds. Mineral cements precipitated in the skin apparently follow original cell boundaries, partially preserving epidermis microstructure. Infrared and electron microprobe images of ossified tendon clearly show preserved mineral zonation, with silica and trapped carbon dioxide forming thin linings on Haversian canals within apatite. Furthermore, Fourier transform infrared spectroscopy (FTIR) of materials recovered from the skin and terminal ungual phalanx suggests the presence of compounds containing amide groups. Amino acid composition analyses of the mineralized skin envelope clearly differ from the surrounding matrix; however, intact proteins could not be obtained using protein mass spectrometry. The presence of endogenously derived organics from the skin was further demonstrated by p...

Ticks are currently among the most prevalent blood-feeding ectoparasites, but their feeding habits and hosts in deep time have long remained speculative. Here, we report direct and indirect evidence in 99 million-year-old Cretaceous amber showing that hard ticks and ticks of the extinct new family Deinocrotonidae fed on blood from feathered dinosaurs, non-avialan or avialan excluding crown-group birds. A †Cornupalpatum burmanicum hard tick is entangled in a pennaceous feather. Two deinocrotonids described as †Deinocroton draculi gen. et sp. nov. have specialised setae from dermestid beetle larvae (hastisetae) attached to their bodies, likely indicating cohabitation in a feathered dinosaur nest. A third conspecific specimen is blood-engorged, its anatomical features suggesting that deinocrotonids fed rapidly to engorgement and had multiple gonotrophic cycles. These findings provide insight into early tick evolution and ecology, and shed light on poorly known arthropod-vertebrate inte...

The stone marten is a widely distributed mustelid in the Palaearctic region that exhibits variable habitat preferences in different parts of its range. The species is a Holocene immigrant from southwest Asia which, according to fossil remains, followed the expansion of the Neolithic farming cultures into Europe and possibly colonized the Iberian Peninsula during the Early Neolithic (ca. 7,000 years BP). However, the population genetic structure and historical biogeography of this generalist carnivore remains essentially unknown. In this study we have combined mitochondrial DNA (mtDNA) sequencing (621 bp) and microsatellite genotyping (23 polymorphic markers) to infer the population genetic structure of the stone marten within the Iberian Peninsula. The mtDNA data revealed low haplotype and nucleotide diversities and a lack of phylogeographic structure, most likely due to a recent colonization of the Iberian Peninsula by a few mtDNA lineages during the Early Neolithic. The microsatel...

P rotein sequences from bone-derived collagen as old as 68 million years have been detected by using mass spectrometry (1, 2). A BLAST search of the resulting peptide sequences found the highest similarities between the collagen peptides obtained from extracts of Tyrannosaurus rex fossil bone and those of birds (Gallus gallus) and between mastodon (Mammut americanum) and other mammals, including elephant (Loxodonta africana). We performed phylogenetic analyses to infer the evolutionary relationships of the T. rex [Museum of the Rockies (MOR) 1125] and mastodon (MOR 605). The results extend our knowledge of trait evolution within nonavian dinosaurs into the macromolecular level of biological organization.

Background: Archaeological bones contain only small amounts of DNA due to post-mortem DNA degradation and the changes endogenous DNA is subjected to during diagenesis. An important step before undertaking such time-consuming and costly analyses as ancient DNA investigation is to predict the presence of DNA in ancient samples. To date, the leading screening method has been amino acid racemization; however, other analytical techniques can also be used to assess the degree of bone preservation. Aim: The aim of the present study was to relate the presence of DNA with bone preservation in order to select samples potentially suitable for ancient DNA analysis. Subjects and methods: Bones collected from several archaeological sites, different locations (cave, rockshelter or sub divo) and diachronic periods were selected for analytical and spectroscopic analysis in order to correlate bone tissue preservation with the presence of DNA. Different techniques were combined to assess the degree of...

Understanding animal terrestrialization, the process through which animals colonized the land, is crucial to clarify extant biodiversity and biological adaptation. Arthropoda (insects, spiders, centipedes and their allies) represent the largest majority of terrestrial biodiversity. Here we implemented a molecular palaeobiological approach, merging molecular and fossil evidence, to elucidate the deepest history of the terrestrial arthropods. We focused on the three independent, Palaeozoic arthropod terrestrialization events (those of Myriapoda, Hexapoda and Arachnida) and showed that a marine route to the colonization of land is the most likely scenario. Molecular clock analyses confirmed an origin for the three terrestrial lineages bracketed between the Cambrian and the Silurian. While molecular divergence times for Arachnida are consistent with the fossil record, Myriapoda are inferred to have colonized land earlier, substantially predating trace or body fossil evidence. An estimat...

A machaeridian, Lepidocoleus hohensteini sp. nov., is described from the Hunsrü ck Slate (Lower Emsian) of Germany. The available material includes a unique example preserving evidence of the soft tissues, only the second machaeridian specimen to do so and the first lepidocoleid. This specimen shows that the plates are attached to alternate segments in the trunk. The morphology is consistent with an annelid affinity of the Lepidocoleidae and confirms the unity of the Machaeridia. This discovery adds an important group to the known diversity of this famous late Palaeozoic marine Konservat-Lagerstätte.

Earth scientists have searched for signs of microscopic life in ancient samples of permafrost, ice, deep-sea sediments, amber, salt and chert. Until now, evidence of cyanobacteria has not been reported in any studies of ancient DNA older than a few thousand years. Here, we investigate morphologically, biochemically and genetically primary evaporites deposited in situ during the late Miocene (Messinian) Salinity Crisis from the north-eastern Apennines of Italy. The evaporites contain fossilized bacterial structures having identical morphological forms as modern microbes. We successfully extracted and amplified genetic material belonging to ancient cyanobacteria from gypsum crystals dating back to 5.910-5.816 Ma, when the Mediterranean became a giant hypersaline brine pool. This finding represents the oldest ancient cyanobacterial DNA to date. Our clone library and its phylogenetic comparison with present cyanobacterial populations point to a marine origin for the depositional basin. This investigation opens the possibility of including fossil cyanobacterial DNA into the palaeo-reconstruction of various environments and could also be used to quantify the ecological importance of cyanobacteria through geological time. These genetic markers serve as biosignatures providing important clues about ancient life and begin a new discussion concerning the debate on the origin of late Miocene evaporites in the Mediterranean.

Fierce debate surrounds the history of organisms in the southern hemisphere; did Gondwanan break-up produce ocean barriers that imposed distribution patterns on phylogenies (vicariance)? Or have organisms modified their distributions through trans-oceanic dispersal? Recent advances in biogeographical theory suggest that the current focus on vicariance versus dispersal is too narrow because it ignores 'geodispersal' (i.e. expansion of species into areas when geographical barriers disappear), extinction and sampling errors. Geodispersal produces multiple, conflicting vicariance patterns, and extinction and sampling errors destroy vicariance patterns. This perspective suggests that it is more difficult to detect vicariance than trans-oceanic dispersal and that specialized methods must be applied if an unbiased understanding of southern hemisphere biogeography is to be achieved.

Among rodents, the lineage from Progonomys hispanicus to Stephanomys documents a case of increasing size and dental specialization during an approximately 9 Myr time-interval. On the contrary, some contemporaneous generalist lineages like Apodemus show a limited morphological evolution. Dental shape can be related to diet and can be used to assess the ecological changes along the lineages. Consequently, size and shape of the first upper molar were measured in order to quantify the patterns of morphological evolution along both lineages and compare them to environmental trends. Climatic changes do not have a direct influence on evolution, but they open new ecological opportunities by changing vegetation and allow the evolution of a specialist like Stephanomys. On the other hand, environmental changes are not dramatic enough to destroy the habitat of a long-term generalist like Apodemus. Hence, our results exemplify a case of an influence of climate on the evolution of specialist species, although a generalist species may persist without change.

Medullary bone (MB), an estrogen-dependent reproductive tissue present in extant gravid birds, is texturally, histologically and compositionally distinct from other bone types. Phylogenetic proximity led to the proposal that MB would be present in non-avian dinosaurs, and recent studies have used microscopic, morphological, and regional homologies to identify this reproductive tissue in both theropod and ornithischian dinosaurs. Here, we capitalize on the unique chemical and histological fingerprint of MB in birds to characterize, at the molecular level, MB in the non-avian theropod Tyrannosaurus rex (MOR 1125), and show that the retention of original molecular components in fossils allows deeper physiological and evolutionary questions to be addressed.

We used in situ radiance/irradiance profiles to retrieve profiles of the spectral backscattering coefficient for all particles in an E. huxleyi coccolithophore bloom off the coast of Plymouth, UK. At high detached coccolith concentrations the spectra of backscattering all showed a minimum near ∼550 to 600 nm. Using flow cytometry estimates of the detached coccolith concentration, and assuming all of the backscattering (over and above the backscattering by the water itself) was due to detached coccoliths, we determined the upper limit of the backscattering cross section (σ b ) of individual coccoliths to be 0:123 AE 0:039 μm 2 =coccolith at 500 nm. Physical models of detached coccoliths were then developed and the discrete dipole approximation was used to compute their average backscattering cross section in random orientation. The result was 0:092 μm 2 at 500 nm, with the computed σ b displaying a spectral shape similar to the measurements, but with less apparent increase in backscattering toward the red. When σ b is computed on a per mole of calcite, rather than a per coccolith basis, it agreed reasonably well with that determined for acid-labile backscattering at 632 nm averaged over several species of cultured calcifying algae. Intact coccolithophore cells were taken into account by arguing that coccoliths attached to coccolithophore cells (forming a "coccosphere") backscatter in a manner similar to free coccoliths in random orientation. Estimating the number of coccoliths per coccosphere and using the observed number of coccolithophore cells resulted is an apparent backscattering cross section at 500 nm of 0:114 AE 0:013 μm 2 =coccolith, in satisfactory agreement with the measured backscattering.

The exquisite transitional fossil Tetrapodophis e described as a stem-snake with four small legs from the Lower Cretaceous of Brazil e has been widely considered a burrowing animal, consistent with recent studies arguing that snakes had fossorial ancestors. We reevaluate the ecomorphology of this important taxon using a multivariate morphometric analysis and a reexamination of the limb anatomy. Our analysis shows that the body proportions are unusual and similar to both burrowing and surface-active squa-mates. We also show that it exhibits striking and compelling features of limb anatomy, including enlarged first metapodials and reduced tarsal/carpal ossification e that conversely are highly suggestive of aquatic habits, and are found in marine squamates. The morphology and inferred ecology of Tetra-podophis therefore does not clearly favour fossorial over aquatic origins of snakes.

Fossil mesostigmatid mites are extremely rare. Inclusions assignable to the tortoise mites (Mesostigmata, Uropodina) are described here for the first time from Eocene (ca. 44–49 Ma) Baltic amber. This is the oldest record of Uropodina and documents the first unequivocal amber examples potentially assignable to the extant genus Uroobovella Berlese, 1903 (Uropodoidea: Urodinychidae). Further mites in the same amber pieces are tentatively assigned to Microgynioidea (Microgyniina) and Ascidae (Gamasina), both potentially representing the oldest records of their respective superfamily and family groups. This new material also preserves behavioural ecology in the form of phoretic deutonymphs attached to their carriers via a characteristic anal pedicel. These deutonymphs in amber are intimately associated with longhorn beetles (Coleoptera: Cerambycidae), probably belonging to the extinct species Nothorhina granulicollis Zang, 1905. Modern uropodines have been recorded phoretic on species b...

Feathers of today's birds are constructed of beta (b)-keratins, structural proteins of the epidermis that are found solely in reptiles and birds. Discoveries of ''feathered dinosaurs'' continue to stimulate interest in the evolutionary origin of feathers, but few studies have attempted to link the molecular evolution of their major structural proteins (b-keratins) to the appearance of feathers in the fossil record. Using molecular dating methods, we show that before the appearance of Anchiornis ($155 Million years ago (Ma)) the basal b-keratins of birds began diverging from their archosaurian ancestor $216 Ma. However, the subfamily of feather b-keratins, as found in living birds, did not begin diverging until $143 Ma. Thus, the pennaceous feathers on Anchiornis, while being constructed of avian b-keratins, most likely did not contain the feather b-keratins found in the feathers of modern birds. Our results demonstrate that the evolutionary origin of feathers does not coincide with the molecular evolution of the feather b-keratins found in modern birds. More likely, during the Late Jurassic, the epidermal structures that appeared on organisms in the lineage leading to birds, including early forms of feathers, were constructed of avian b-keratins other than those found in the feathers of modern birds. Recent biophysical studies of the b-keratins in feathers support the view that the appearance of the subfamily of feather b-keratins altered the biophysical nature of the feather establishing its role in powered flight. How to cite this article: Greenwold MJ, Sawyer RH. 2011. Linking the molecular evolution of avian beta (b) keratins to the evolution of feathers. J. Exp. Zool. (Mol. Dev. Evol.) 316:609-616.

Reconstructions of foraging behavior and diet are central to our understanding of fossil hominin ecology and evolution. Current hypotheses for the evolution of the genus Homo invoke a change in foraging behavior to include higher quality foods. Recent microwear texture analyses of fossil hominin teeth have suggested that the evolution of Homo erectus may have been marked by a transition to a more variable diet. In this study, we used microwear texture analysis to examine the occlusal surface of 2 molars from Dmanisi, a 1.8 million year old fossil hominin site in the Republic of Georgia. The Dmanisi molars were characterized by a moderate degree of surface complexity (Asfc), low textural fill volume (Tfv), and a relatively low scale of maximum complexity (Smc), similar to specimens of early African H. erectus. While caution must be used in drawing conclusions from this small sample (n = 2), these results are consistent with continuity in diet as H. erectus expanded into Eurasia.

Coral species composition of drilled cores from emergent bank reefs, and coral cover of the surface of old and living reefs located along the coast of the state of Bahia, Eastern Brazil, revealed that there is a marked change in the occurrence of the major building coral species in different time intervals of the reef structure, as well as in the living surface of reefs located in two different geographical sites. Holocene core sections from two reef areas (12°40 0 S-38°00 0 W and 18°00 0 S-39°00 0 W) have as major reef builders, on its topmost core interval (3 to 4 ky old), the endemic coral Mussismilia braziliensis Verrill, 1868, which also dominate on the 2.5-3.5 ky old surfaces of truncated reef tops. At the base of the cores (the 2 m lower interval, older than 4 ky BP), another endemic coral Mussismilia harttii Verrill, 1868 is the dominant reef component. The relative abundance of M. braziliensis on the living surfaces of shallow reefs from both areas, shows that in the southern area, it is up to 98% on reefs located 60 km off the coast, in depths between 3 and 4 m, but do not exceed 1.3% on the surface of the northern reefs located 1-2 km off the coast in depths 4-5 m. The Holocene falling sea level that occurred along the coast of Brazil since 5.1 ky BP, causes an increasing runoff into the area of coastal reefs. This phenomenon may have affected the nearshore reef building fauna, replacing a more susceptive coral fauna with one better adapted to low light levels and higher sediment influx. The high turbidity associated with early Holocene shelf flooding, should also be responsible for the absence of M. braziliensis during the initial stages of reef buildup in Brazil. At the present time, the rapidly increasing human pressure, due to changes in land uses of the coastal zone (increasing sedimentation rate, nutrification of coastal waters, industrial pollution) and underwater practices, such as overfishing and an intense tourism, is aggravating the recovery capacity of this already naturally threatened coral community. If this situation coupled with increasing sea surface temperature persists, modern coral reef growth, in Brazil cannot be maintained and the major reef building coral species of the reefs in Bahia, a remnant endemic coral fauna will very soon appear in the list of endangered species.

Abstract Sauropod dinosaurs were the largest terrestrial
herbivores and pushed at the limits of vertebrate biomechanics
and physiology. Sauropods exhibit high craniodental
diversity in ecosystems where numerous species coexisted,
leading to the hypothesis that this biodiversity is
linked to niche subdivision driven by ecological specialisation.
Here, we quantitatively investigate feeding behaviour
hypotheses for the iconic sauropod Diplodocus. Biomechanical
modelling, using finite element analysis, was used to
examine the performance of the Diplodocus skull. Three
feeding behaviours were modelled: muscle-driven static biting,
branch stripping and bark stripping. The skull was found to be
‘over engineered’ for static biting, overall experiencing low
stress with only the dentition enduring high stress. When
branch stripping, the skull, similarly, is under low stress, with
little appreciable difference between those models. When simulated for bark stripping, the skull experiences far greater
stresses, especially in the teeth and at the jaw joint. Therefore,
we refute the bark-stripping hypothesis, while the hypotheses
of branch stripping and/or precision biting are both
consistent with our findings, showing that branch stripping
is a biomechanically plausible feeding behaviour
for diplodocids. Interestingly, in all simulations, peak
stress is observed in the premaxillary–maxillary ‘lateral
plates’, supporting the hypothesis that these structures
evolved to dissipate stress induced while feeding. These
results lead us to conclude that the aberrant craniodental
form of Diplodocus was adapted for food procurement
rather than resisting high bite forces.

Present work illustrates a scheme of quantitative description of the shape of the skull outlines of temnospondyl amphibians using bilaterally symmetric closed Fourier curves. Some special points have been identified on the Fourier fits of the skull outlines, which are the local maxima, or minima of the distances from the centroid of the points at the skull outline. These points denotes break in curvature of the outline and their positions can be compared to differentiate the skull shapes. The ratios of arc-lengths of the posterior and lateral outline of 58 temnospondyl skulls have been plotted to generate a triaguarity series of the skulls. This series grades different families, some of their genera and species as well as some individuals according to their posterior and lateral skull length ratios. This model while comparing different taxa, takes into account the entire arc-length of the outline of the temnospondyl skulls, and does not depend on few geometric or biological points used by earlier workers for comparing skull shapes.

Flying fishes are extraordinary aquatic vertebrates capable of gliding great distances over water by exploiting their enlarged pectoral fins and asymmetrical caudal fin. Some 50 species of extant flying fishes are classified in the Exocoetidae (Neopterygii: Teleostei), which have a fossil record no older than the Eocene. The Thoracopteridae is the only pre-Cenozoic group of non-teleosts that shows an array of features associated with the capability of over-water gliding. Until recently, however, the fossil record of the Thoracopteridae has been limited to the Upper Triassic of Austria and Italy. Here, we report the discovery of exceptionally well-preserved fossils of a new thoracopterid flying fish from the Middle Triassic of China, which represents the earliest evidence of an over-water gliding strategy in vertebrates. The results of a phylogenetic analysis resolve the Thoracopteridae as a stem-group of the Neopterygii that is more crown-ward than the Peltopleuriformes, yet more ba...

Mycorrhizal fungi are among the most common symbioses found in terrestrial ecosystems, both natural and managed. They are important for many reasons, but most notably because of their positive effects on plant growth, which are mediated by their uptake of nutrients from the soil and transport of these to the roots. Moreover, many edible fungi are mycorrhizal. The study of mycorrhizal fungi has been hampered by the inability to identify species and individuals in the soil. This has been greatly aided by DNA-based methods, which first require the extraction of DNA. Herein, I discuss some general concerns that must be considered when extracting and purifying DNA from ecological samples and offer specific methods for soil, mycorrhizal roots, and fruiting bodies. These methods are rapid, safe, effective, relatively inexpensive, and convenient because they are based on commercially available kits. 58 comparing macromolecules [5]

The feeding mechanism of gars (Ginglymodi : Lepisosteidae) is characterized by cranial elevation and lower jaw rotation but minimal cranial kinesis. Gar jaws have numerous, sharply pointed, elongate teeth for capture of evasive prey. Their mandibles range from relatively short to extremely long depending on the species. Jaw length and lever dimensions were hypothesized to affect the biomechanics of force and motion during feeding, according to simple mechanical models of muscles exerting force through first-or third-order levers. A morphometric protocol was used to measure the jaw structure of seven living and five fossil species of gar and these data were used to calculate the mechanical advantage (a measure of force transmission) for both opening and closing of the mandible. Gars were found to possess low mechanical advantage (MA) and high transmission of motion, although gars occupy a range of biomechanical states across the continuum of force vs. velocity transmission. The longnose gar, Lepisosteus osseus, has one of the lowest jaw closing MAs (0.05) ever measured in fishes. Intraspecific lever mechanics were also calculated for a developmental series (from feeding larvae to adults) of L. osseus and Atractosteus spatula. A characteristic ontogenetic curve in MA of the lower jaw was obtained, with a large decrease in MA between larva and juvenile, followed by a steady increase during adult growth. This curve correlates with a change in prey type, with the small, robust-jawed individuals feeding mainly on crustaceans and insects and the large, long-jawed individuals of all species becoming mainly piscivorous. Principal components analysis of functionally important morphometrics shows that several gar species occupy different regions of functional morphospace. Some fossil gar species are also placed within functional morphospace using this approach. J. Morphol. 000: 000 -000, 2005.

We have synthesized inorganic micron-sized filaments, whose microstucture consists of silica-coated nanometer-sized carbonate crystals, arranged with strong orientational order. They exhibit noncrystallographic, curved, helical morphologies, reminiscent of biological forms. The filaments are similar to supposed cyanobacterial microfossils from the Precambrian Warrawoona chert formation in Western Australia, reputed to be the oldest terrestrial microfossils. Simple organic hydrocarbons, whose sources may also be abiotic and indeed inorganic, readily condense onto these filaments and subsequently polymerize under gentle heating to yield kerogenous products. Our results demonstrate that abiotic and morphologically complex microstructures that are identical to currently accepted biogenic materials can be synthesized inorganically.

Recent discoveries from the Aptian–Albian Antlers (Oklahoma) and Cloverly (Montana, Wyoming) formations provide significant additions to the Early Cretaceous record of lizards in North America. The lizards from the Antlers Formation include two teiids (one named), an anguimorphan, and a series of fragmentary jaws with “paramacellodid”-like teeth. The lizards from the Cloverly Formation include a new species of Paramacellodus and many indeterminate jaw fragments. The apparent lack of shared lizard taxa between the two units calls into question their temporal equivalence, which is based on similarity of dinosaur taxa. Although apparently distinct, the lizard faunas of both units are very similar to that of the Late Jurassic Morrison Formation in being composed primarily of “para-macellodid” or “paramacellodid”-like taxa. It appears that there was a period of relative stasis in the evolution of lizards in North America between the Late Jurassic and Aptian–Albian, paralleling a similar trend in Europe between the Late Jurassic and the Barremian (or later). Reported lizards from the Aptian-Albian of Mongolia present a level of taxonomic diversity much different than that of the same time period in Oklahoma, Montana, and Wyoming, but more like that of the Late Cretaceous of North America, suggesting that taxonomic groups common to the Late Cretaceous and Tertiary occurred earlier in Asia than in North America.

Authors describe a hyoid bone body, without horns, attributed to Homo erectus from Castel di Guido (Rome, Italy), dated to about 400,000 years BP. The hyoid bone body shows the bar-shaped morphology characteristic of Homo, in con- trast to the bulla-shaped body morphology of African apes and Australopithecus. Its measurements differ from those of the only known complete specimens from other extinct human species and early hominid (Kebara Neandertal and Au- stralopithecus afarensis), and from the mean values observed in modern humans. The almost total absence of muscular impressions on the body's ventral surface suggests a reduced capability for elevating this hyoid bone and modulating the length of the vocal tract in Homo erectus. The shield-shaped body, the probable small size of the greater horns and the ra- diographic image appear to be archaic characteristics; they reveal some similarities to non-humans and pre-human gen- era, suggesting that the morphological basis for hum...

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.

Many aspects of human biology can be reconstructed from skeletal and fossil remains. The endocranial vasculature runs through cerebral, connective, and bone elements, where it is influenced by the functional and structural relationships among these different components of the endocranial system. The imprints and traces of these vessels can be used to analyze the craniovascular features of extinct species or historical samples. These traits can supply information about evolutionary adaptation, the mutual relationships between and within populations, and individual life history. In particular, bioarchaeology considers individual morphological variants as indicators of temporal and spatial relatedness and population structure, whereas paleoanthropology studies functional aspects to consider evolutionary changes and phylogenetic processes. Forensic science can investigate the cause of death associated with craniovascular pathologies by relying on morphological variations for individual ...

The maxilliped venom claw is an intriguing structure in centipedes. We address open questions concerning this structure. The maxillipeds of fossil centipedes from the Carboniferous (about 300 million years old) have been described, but not been depicted previously. Re-investigation demonstrates that they resemble their modern counterparts. A Jurassic geophilomorph centipede (about 150 million years old) was originally described as possessing a rather leg-like maxilliped. Our re-investigation shows that the maxilliped is, in fact, highly specialized as in modern Geophilomorpha. A scenario for the evolution of the centipede maxilliped is presented. It supports one of the two supposed hypotheses of centipede phylogeny, the Pleurostigmophora hypothesis. Although this hypothesis appears now well established, many aspects of character evolution resulting from this phylogeny remain to be told in detail. One such aspect is the special joint of the maxilliped in some species of Cryptops. Cry...

Earlier observations of the virtual endocast of LB1, the type specimen for Homo floresiensis, are reviewed, extended, and interpreted. Seven derived features of LB1's cerebral cortex are detailed: a caudallypositioned occipital lobe, lack of a rostrally-located lunate sulcus, a caudally-expanded temporal lobe, advanced morphology of the lateral prefrontal cortex, shape of the rostral prefrontal cortex, enlarged gyri in the frontopolar region, and an expanded orbitofrontal cortex. These features indicate that LB1's brain was globally reorganized despite its ape-sized cranial capacity (417 cm 3 ). Neurological reorganization may thus form the basis for the cognitive abilities attributed to H. floresiensis. Because of its tiny cranial capacity, some workers think that LB1 represents a Homo sapiens individual that was afflicted with microcephaly, or some other pathology, rather than a new species of hominin. We respond to concerns about our earlier study of microcephalics compared with normal individuals, and reaffirm that LB1 did not suffer from this pathology. The intense controversy about LB1 reflects an older continuing dispute about the relative evolutionary importance of brain size versus neurological reorganization. LB1 may help resolve this debate and illuminate constraints that governed hominin brain evolution.

Global climate change, linked to astronomical forcing factors, has been implicated in faunal evolutionary change in equatorial Africa, including
the origin and diversification of hominin lineages. Empirical terrestrial data demonstrating that orbital forcing has a significant effect,
or is detectable, at early hominin sites in equatorial continental interiors during the Pliocene, however, remain limited. Sedimentation patterns in
the Baringo Basin within the Central Kenyan Rift Valley between ca. 2.7 and 2.55 Ma, controlled by climatic factors, provide a detailed paleoenvironmental
record spanning 35 fossil vertebrate localities, including three hominin sites. The succession includes a sequence of diatomites
that record rhythmic cycling of major freshwater lake systems consistent with w23-kyr Milankovitch precessional periodicity. The temporal
framework of shifting precipitation patterns, relative to Pliocene insolation curves, implicate African monsoonal climatic control and indicate
that climatic fluctuations in Rift Valley ecosystems were paced by global climatic change documented in marine cores. These data provide direct
evidence of orbitally mediated environmental change at Pliocene Rift Valley hominin fossil localities, providing a unique opportunity to assess
the evolutionary effect of short-term climatic flux on late Pliocene East African terrestrial communities.