Inter-amphibian predation in the Early Cretaceous of China.

For most fossil taxa, dietary inference relies primarily on indirect evidence from jaw morphology and the dentition. In rare cases, however, preserved gut contents provide direct evidence of feeding strategy and species interaction. This is important in the reconstruction of food webs and energy flow through ancient ecosystems. The Early Cretaceous Chinese Jehol Biota has yielded several such examples, with lizards, birds, small dinosaurs, and mammals as both predator and prey. Here we describe an Early Cretaceous fossil frog specimen, genus Genibatrachus, that contains an adult salamander within its body cavity. The salamander is attributed to the hynobiid-like genus Nuominerpeton. The salamander skeleton is complete and articulated, suggesting it was caught and swallowed shortly before the frog itself died and was buried.

New dating evidence of the early presence of hominins in Southern Europe.

The first "Out of Africa" migrations represent a seminal event in the history of humankind. At the gates of Europe, the first appearance of Hominins is recorded in Georgia, 1.8 million years ago (Ma); however, the picture of migration across the continent remains incomplete. Vallonnet Cave (France) is a Lower Paleolithic prehistoric site with traces of hominin activities including lithic remains and cut-marks on mammal bones. Here, we apply the uranium-lead (U-Pb) methods to two flowstones to date the intervening archaeological levels. The U-Pb data, coupled with paleomagnetic constraints, provide an age range from 1.2 to 1.1 Ma. The results conclusively demonstrate that Vallonnet Cave is one of the oldest European prehistoric sites in France with early hominin occupations associated with an Epivillafranchian fauna. Combined with data from other archaeological sites, the new precise chronology suggests a widespread occupation the Northern Mediterranean to Southwestern Europe at ~1.2 Ma.

Mandibular and dental characteristics of Late Triassic mammaliaform Haramiyavia and their ramifications for basal mammal evolution.

As one of the earliest-known mammaliaforms, Haramiyavia clemmenseni from the Rhaetic (Late Triassic) of East Greenland has held an important place in understanding the timing of the earliest radiation of the group. Reanalysis of the type specimen using high-resolution computed tomography (CT) has revealed new details, such as the presence of the dentary condyle of the mammalian jaw hinge and the postdentary trough for mandibular attachment of the middle ear-a transitional condition of the predecessors to crown Mammalia. Our tests of competing phylogenetic hypotheses with these new data show that Late Triassic haramiyids are a separate clade from multituberculate mammals and are excluded from the Mammalia. Consequently, hypotheses of a Late Triassic diversification of the Mammalia that depend on multituberculate affinities of haramiyidans are rejected. Scanning electron microscopy study of tooth-wear facets and kinematic functional simulation of occlusion with virtual 3D models from CT scans confirm that Haramiyavia had a major orthal occlusion with the tallest lingual cusp of the lower molars occluding into the lingual embrasure of the upper molars, followed by a short palinal movement along the cusp rows alternating between upper and lower molars. This movement differs from the minimal orthal but extensive palinal occlusal movement of multituberculate mammals, which previously were regarded as relatives of haramiyidans. The disparity of tooth morphology and the diversity of dental functions of haramiyids and their contemporary mammaliaforms suggest that dietary diversification is a major factor in the earliest mammaliaform evolution.

A Cretaceous eutriconodont and integument evolution in early mammals.

The Mesozoic era (252-66 million years ago), known as the domain of dinosaurs, witnessed a remarkable ecomorphological diversity of early mammals. The key mammalian characteristics originated during this period and were prerequisite for their evolutionary success after extinction of the non-avian dinosaurs 66 million years ago. Many ecomorphotypes familiar to modern mammal fauna evolved independently early in mammalian evolutionary history. Here we report a 125-million-year-old eutriconodontan mammal from Spain with extraordinary preservation of skin and pelage that extends the record of key mammalian integumentary features into the Mesozoic era. The new mammalian specimen exhibits such typical mammalian features as pelage, mane, pinna, and a variety of skin structures: keratinous dermal scutes, protospines composed of hair-like tubules, and compound follicles with primary and secondary hairs. The skin structures of this new Mesozoic mammal encompass the same combination of integumentary features as those evolved independently in other crown Mammalia, with similarly broad structural variations as in extant mammals. Soft tissues in the thorax and abdomen (alveolar lungs and liver) suggest the presence of a muscular diaphragm. The eutriconodont has molariform tooth replacement, ossified Meckel's cartilage of the middle ear, and specialized xenarthrous articulations of posterior dorsal vertebrae, convergent with extant xenarthran mammals, which strengthened the vertebral column for locomotion.

The vertebrate diencephalic MCH system: a versatile neuronal population in an evolving brain.

Neurons synthesizing melanin-concentrating hormone (MCH) are described in the posterior hypothalamus of all vertebrates investigated so far. However, their anatomy is very different according to species: they are small and periventricular in lampreys, cartilaginous fishes or anurans, large and neuroendocrine in bony fishes, or distributed over large regions of the lateral hypothalamus in many mammals. An analysis of their comparative anatomy alongside recent data about the development of the forebrain, suggests that although very different, MCH neurons of the caudal hypothalamus are homologous. We further hypothesize that their divergent anatomy is linked to divergence in the forebrain - in particular telencephalic evolution.

A Jurassic eutherian mammal and divergence of marsupials and placentals.

Placentals are the most abundant mammals that have diversified into every niche for vertebrates and dominated the world's terrestrial biotas in the Cenozoic. A critical event in mammalian history is the divergence of eutherians, the clade inclusive of all living placentals, from the metatherian-marsupial clade. Here we report the discovery of a new eutherian of 160 Myr from the Jurassic of China, which extends the first appearance of the eutherian-placental clade by about 35 Myr from the previous record, reducing and resolving a discrepancy between the previous fossil record and the molecular estimate for the placental-marsupial divergence. This mammal has scansorial forelimb features, and provides the ancestral condition for dental and other anatomical features of eutherians.

Transitional mammalian middle ear from a new Cretaceous Jehol eutriconodont.

The transference of post-dentary jaw elements to the cranium of mammals as auditory ossicles is one of the central topics in evolutionary biology of vertebrates. Homologies of these bones among jawed vertebrates have long been demonstrated by developmental studies; but fossils illuminating this critical transference are sparse and often ambiguous. Here we report the first unambiguous ectotympanic (angular), malleus (articular and prearticular) and incus (quadrate) of an Early Cretaceous eutriconodont mammal from the Jehol Biota, Liaoning, China. The ectotympanic and malleus have lost their direct contact with the dentary bone but still connect the ossified Meckel's cartilage (OMC); we hypothesize that the OMC serves as a stabilizing mechanism bridging the dentary and the detached ossicles during mammalian evolution. This transitional mammalian middle ear narrows the morphological gap between the mandibular middle ear in basal mammaliaforms and the definitive mammalian middle ear (DMME) of extant mammals; it reveals complex changes contributing to the detachment of ear ossicles during mammalian evolution.

The first hominin of Europe.

The earliest hominin occupation of Europe is one of the most debated topics in palaeoanthropology. However, the purportedly oldest of the Early Pleistocene sites in Eurasia lack precise age control and contain stone tools rather than human fossil remains. Here we report the discovery of a human mandible associated with an assemblage of Mode 1 lithic tools and faunal remains bearing traces of hominin processing, in stratigraphic level TE9 at the site of the Sima del Elefante, Atapuerca, Spain. Level TE9 has been dated to the Early Pleistocene (approximately 1.2-1.1 Myr), based on a combination of palaeomagnetism, cosmogenic nuclides and biostratigraphy. The Sima del Elefante site thus emerges as the oldest, most accurately dated record of human occupation in Europe, to our knowledge. The study of the human mandible suggests that the first settlement of Western Europe could be related to an early demographic expansion out of Africa. The new evidence, with previous findings in other Atapuerca sites (level TD6 from Gran Dolina), also suggests that a speciation event occurred in this extreme area of the Eurasian continent during the Early Pleistocene, initiating the hominin lineage represented by the TE9 and TD6 hominins.

Convergent dental adaptations in pseudo-tribosphenic and tribosphenic mammals.

Tribosphenic molars of basal marsupials and placentals are a major adaptation, with the protocone (pestle) of the upper molar crushing and grinding in the talonid basin (mortar) on the lower molar. The extinct pseudo-tribosphenic mammals have a reversed tribosphenic molar in which a pseudo-talonid is anterior to the trigonid, to receive the pseudo-protocone of the upper molar. The pseudo-protocone is analogous to the protocone, but the anteriorly placed pseudo-talonid is opposite to the posterior talonid basin of true tribosphenic mammals. Here we describe a mammal of the Middle Jurassic period with highly derived pseudo-tribosphenic molars but predominantly primitive mandibular and skeletal features, and place it in a basal position in mammal phylogeny. Its shoulder girdle and limbs show fossorial features similar to those of mammaliaforms and monotremes, but different compared with those of the earliest-known Laurasian tribosphenic (boreosphenid) mammals. The find reveals a much greater range of dental evolution in Mesozoic mammals than in their extant descendants, and strengthens the hypothesis of homoplasy of 'tribosphenic-like' molars among mammals.

Fluorescent detection of lipid droplets and associated proteins.

Most eukaryotic cells can store excess lipid in cytosolic lipid droplets. This unit discusses techniques for the visualization of lipid droplets and associated proteins in cultured mammalian cells. Protocols for the detection of lipid droplets with nile red and BODIPY 493/503 are included. The differences in the spectral properties of these two lipophilic dyes and advantages of each are discussed. The best method for combining visualization of intracellular lipid droplets with indirect immunofluorescent detection of lipid droplet-associated proteins is described. Techniques for sample fixation and permeabilization must be chosen carefully to avoid alterations to lipid droplet morphology. Immunofluorescent detection of adipophilin, a broadly expressed, lipid droplet-associated protein, widely used as a marker for lipid droplet accumulation, is presented as an example. Finally, a simple protocol for enhancing lipid droplet accumulation through supplementation with excess fatty acid is included.

A Mesozoic gliding mammal from northeastern China.

Gliding flight has independently evolved many times in vertebrates. Direct evidence of gliding is rare in fossil records and is unknown in mammals from the Mesozoic era. Here we report a new Mesozoic mammal from Inner Mongolia, China, that represents a previously unknown group characterized by a highly specialized insectivorous dentition and a sizable patagium (flying membrane) for gliding flight. The patagium is covered with dense hair and supported by an elongated tail and limbs; the latter also bear many features adapted for arboreal life. This discovery extends the earliest record of gliding flight for mammals to at least 70 million years earlier in geological history, and demonstrates that early mammals were diverse in their locomotor strategies and lifestyles; they had experimented with an aerial habit at about the same time as, if not earlier than, when birds endeavoured to exploit the sky.

A Cretaceous symmetrodont therian with some monotreme-like postcranial features.

A new spalacotheriid mammal preserved with a complete postcranium and a partial skull has been discovered from the Yixian Formation of Liaoning, China. Spalacotheroid symmetrodonts are relatives to modern therians (combined group of marsupials and placentals) and are characterized by many skeletal apomorphies of therians. But unlike the closely related spalacotheroids and living therians, this new mammal revealed some surprisingly convergent features to monotremes in the lumbar vertebrae, pelvis and hindlimb. These peculiar features may have developed as functional convergence to locomotory features of monotremes, or the presence of lumbar ribs in this newly discovered mammal and their absence in its close relatives might be due to evolutionary developmental homoplasy. Analysis including this new taxon suggests that spalacotheroids evolved earlier in Eurasia and then dispersed to North America, in concordance with prevailing geodispersal patterns of several common mammalian groups during the Early Cretaceous period.

The mammalian superior colliculus: laminar structure and connections.

The superior colliculus is a laminated midbrain structure that acts as one of the centers organizing gaze movements. This review will concentrate on sensory and motor inputs to the superior colliculus, on its internal circuitry, and on its connections with other brainstem gaze centers, as well as its extensive outputs to those structures with which it is reciprocally connected. This will be done in the context of its laminar arrangement. Specifically, the superficial layers receive direct retinal input, and are primarily visual sensory in nature. They project upon the visual thalamus and pretectum to influence visual perception. These visual layers also project upon the deeper layers, which are both multimodal, and premotor in nature. Thus, the deep layers receive input from both somatosensory and auditory sources, as well as from the basal ganglia and cerebellum. Sensory, association, and motor areas of cerebral cortex provide another major source of collicular input, particularly in more encephalized species. For example, visual sensory cortex terminates superficially, while the eye fields target the deeper layers. The deeper layers are themselves the source of a major projection by way of the predorsal bundle which contributes collicular target information to the brainstem structures containing gaze-related burst neurons, and the spinal cord and medullary reticular formation regions that produce head turning.

Large Mesozoic mammals fed on young dinosaurs.

Mesozoic mammals are commonly portrayed as shrew- or rat-sized animals that were mainly insectivorous, probably nocturnal and lived in the shadow of dinosaurs. The largest known Mesozoic mammal represented by substantially complete remains is Repenomamus robustus, a triconodont mammal from the Lower Cretaceous of Liaoning, China. An adult individual of R. robustus was the size of a Virginia opossum. Here we report a new species of the genus, represented by a skeleton with most of the skull and postcranium preserved in articulation. The new species is 50% larger than R. robustus in skull length. In addition, stomach contents associated with a skeleton of R. robustus reveal remains of a juvenile Psittacosaurus, a ceratopsian dinosaur. Our discoveries constitute the first direct evidence that some triconodont mammals were carnivorous and fed on small vertebrates, including young dinosaurs, and also show that Mesozoic mammals had a much greater range of body sizes than previously known. We suggest that Mesozoic mammals occupied diverse niches and that some large mammals probably competed with dinosaurs for food and territory.

RTP family members induce functional expression of mammalian odorant receptors.

Transport of G protein-coupled receptors (GPCRs) to the cell surface membrane is critical in order for the receptors to recognize their ligands. However, mammalian GPCR odorant receptors (ORs), when heterologously expressed in cells, are poorly expressed on the cell surface. Here we show that the transmembrane proteins RTP1 and RTP2 promote functional cell surface expression of ORs expressed in HEK293T cells. Genes encoding these proteins are expressed specifically in olfactory neurons. These proteins are associated with OR proteins and enhance the OR responses to odorants. Similar although weaker effects were seen with a third protein, REEP1. These findings suggest that RTP1 and RTP2 in particular play significant roles in the translocation of ORs to the plasma membrane as well as in the functioning of ORs. We have used this approach to identify active odorant ligands for ORs, providing a platform for screening the chemical selectivity of the large OR family.

Gonadotropin-releasing hormone (GnRH): from fish to mammalian brains.

This work deals with a family of neuropeptides, gonadotropin-releasing hormone (GnRH), that play a key role in the development and maintenance of reproductive function in vertebrates. 2. Until now, a total of 16 GnRH structural variants have been isolated and characterized from vertebrate and protochordate nervous tissue. All vertebrate species already investigated have at least two GnRH forms coexisting in the central nervous system. However, it is now well accepted that three forms of GnRH in early and late evolved bony fishes are present. 3. In these cases, cGnRH-II is expressed by midbrain neurons, a species-specific GnRH is present mainly in the preoptic area and the hypothalamus, and sGnRH is localized in the terminal nerve ganglion (TNG). In this context it is possible to think that three GnRH forms and three GnRH receptor (GnRH-R) subtypes are expressed in the central nervous system of a given species. 4. Then it is possible to propose three different GnRH lineages expressed by distinct brain areas in vertebrates: (1) the conserved cGnRH-II or mesencephalic lineage; or (2) the hypothalamic or "releasing" lineage whose primary structure has diverged by point mutations (mGnRH and its orthologous forms: hrGnRH, wfGnRH, cfGnRH, sbGnRH, and pjGnRH); and (3) the telencephalic sGnRH form. Also different GnRH nomenclatures are discussed.

A comparative analysis of the morphology of corticothalamic projections in mammals.

Recent anatomical tracing methods have revealed new principles underlying the organization of corticothalamic connections in the mammalian nervous system. These data demonstrated the distribution of two types of synaptic contacts in the corticothalamic projection: small (<1 microm) and giant (2-10 microm) axon terminals. We compare the organization of corticothalamic projections in the auditory, somatosensory, visual, and motor systems of a variety of mammalian species, including the monkey. In all these systems and species, both types of corticothalamic terminals have been observed. Small endings formed the major corticothalamic terminal field, whereas giant terminals were less numerous and formed additional terminal fields together with small terminals. After comparing their spatial distribution, as well as the degree of reciprocity between the corticothalamic and thalamocortical projections, different roles are proposed for small and giant endings. Small terminals are typically present in the projection serving the feed-back control of the cerebral cortex on the thalamic nucleus from which it receives its main projection. In contrast, giant terminals are involved in feed-forward projections by which activity from a cortical area is distributed, via the thalamus, to other parts of the cerebral cortex. The cross-species and cross-systems comparison reveals differences in the mode of feed-forward projection, which may be involved in the activation of other parts of the same cortical area or form part of a projection that activates other cortical areas.