Phylogeny of Schisandraceae based on morphological data: evidence from modern plants and the fossil record

Schisandraceae are traditionally subdivided in two genera, Schisandra and Kadsura, based on differences in the organisation of the floral receptacle, the carpels, and the presence or absence of a ``pseudostigma'. Recently, phylogenetic analyses utilizing ITS sequence data and morphological data resulted in incongruent tree topologies, with the morphological trees suggesting monophyly of the two genera, whereas ITS trees did not resolve Schisandra and Kadsura as monophyletic clades. In the present paper we study seed morphology and leaf epidermal features of 22 species of Schisandraceae in order to provide additional data for a morphological data matrix. Seed morphological characters are highly homoplastic and do not yield further evidence for monophyly of the two genera. Instead, a number of characters appear to support sister group relationships between taxa within the genera, such as, for instance, for K. coccinea and K. scandens, both of which have large seeds along with a multi-layered mesotesta. Considering leaf epidermal characteristics, species of Kadsura were found to be consistently amphistomatic, whereas species of Schisandra are always hypostomatic. Phylogenetic analysis using the extended data matrix resulted in weakly supported Kadsura and Schisandra clades with five and four synapomorphies indicating monophyly of Kadsura and Schisandra, respectively. Fossils ascribed to Schisandraceae date back to the Late Cretaceous. These are tri-and hexacolpate pollen types displaying a combination of features found in modern Schisandraceae and partly also in Illiciaceae. Leaf remains from this period are poorly preserved and difficult to ascribe to Schisandraceae because of the lack of synapomorphies for the family. In the Early Cainozoic, leaf and seed remains from North America and Europe unambiguously belong to the family. Seeds from the Eocene of North America show some similarities to the modern Schisandra glabra from North America, while fossils from Europe show more similarities to modern Asian species.     

Preface: The phylogeny, fossil record and ecological diversity of ostracod crustaceans

After more than two centuries of research, more than 65,000 living and fossil ostracod species have been described and studied, yet much remains to be learned about this ancient, widespread and diverse group of bivalved arthropods. Their higher classification and phylogeny are subjects of vigorous debate, as is their position in the broader picture of crustacean phylogeny. At the same time, major advances in our understanding of ostracod lineages and their relationships are resulting from the application of innovative approaches and techniques. This preface provides a contextual overview of the 15 contributions to this volume, which resulted from the 14th International Symposium on Ostracoda (ISO2001) held in 2001at Shizuoka, Japan. As such it provides a cross-section of topics at the forefront of research on the evolution and diversity of Ostracoda, and indicates directions for future work.     

First record of a pterosaur landing trackway

The terrestrial progression of pterosaurs, the flying reptiles of the Mesozoic Era, has been debated for over two centuries. The recent discovery of quadrupedal pterodactyloid pterosaur tracks from Late Jurassic sediments near Crayssac, France, shows that the hindlimbs moved parasagittally, as in mammals, birds and other dinosaurs, and the hypertrophied forelimbs could make tracks both close to the body wall and far outside it. Their manus tracks are unique in form, position and kinematics, which would be expected because the forelimbs were used for flight. Here, we report the first record of a pterosaur landing track, which differs substantially from typical walking trackways. The individual landed on both hind feet in parallel fashion, dragged its toes slightly as it left the track, landed again almost immediately and placed the hindfeet parallel again, then placed its forelimbs on the ground, took another short step with both hindlimbs and adjusted its forelimbs, and then began to walk off normally. The trackway shows that pterosaurs stalled to land, a reflection of their highly developed capacity for flight control and manoeuverability.     

Braincase evolution in suchian archosaurs (Reptilia: Diapsida): evidence from the rauisuchian Batrachotomus kupferzellensis

The osteology of an almost complete braincase of the rauisuchian archosaur Batrachotomus kupferzellensis Gower from the Middle Triassic of Germany is described. There is a possibly discrete epiotic ossification, the metotic fissure is undivided by bone (i.e. there is a metotic foramen), the medial wall of the otic capsule is mostly ossified, the cerebral branch of the internal carotid artery entered the lateral surface of the parabasisphenoid, the ventral ramus of the opisthotic is more prominent laterally than a strong subvertical ridge on the exoccipital and basioccipital that lies posterior to the external foramen for the hypoglossal nerve, and the perilymphatic foramen faces away from the otic capsule in a posterior direction. Braincase morphology in the rauisuchians Saurosuchus galilei , Postosuchus kirkpatricki, and Tikisuchus romeri is reviewed. A matrix of 27 braincase characters for 12 archosaurian taxa is analysed. The most parsimonious hypothesis is consistent with the currently orthodox view of archosaurian phylogeny, except in that aetosaurians are more closely related to crocodylomorphs than is any rauisuchian. This phylogeny is used in a brief interpretation of the evolution of derived braincase features present in extant crocodilians. © 2002 The Linnean Society of London, Zoological Journal of the Linnean Society , 2002, 136 , 49–76.     

The fossil evidence of anthropoid brain evolution

The endocast of Aegyptopithecus, a 27 million year old ape, reveals that its brain was advanced over that of prosimians and comparable to that of modern anthropoids in relative size and in having expanded visual cortex, reduced olfactory bulbs, and a central sulcus separating primary somatic sensory and motor cortex. The early appearance of those features suggests that they may have been among the adaptations responsible for the evolution of anthropoids from prosimian ancestors. The frontal lobe was relatively smaller in Aegyptopithecus than in modern anthropoids. An endocast of Dolichocebus, one of the oldest known New World monkeys (25–30 million years old), reveals visual cortex expanded as in modern anthropoids. The 19 million year old Napak frontal bone displays a hominoid rather than cercopithecoid sulcal pattern. An 18 million year old endocast of the ape Dryopithecus (Proconsul) was neither monkey-like nor primitive, as originally described, but rather apelike and essentially modern in all observable features. The oldest undoubted Old World monkey endocast, from nine million year old Mesopithecus, reveals that the brain was modern in sulcal pattern and proportions. The sulcal pattern was like that of modern colobines, but that appears to be the more primitive condition, from which features characteristic of modern cercopithecine brains have evolved. The brain of six million year old Libypithecus was similar to that of Mesopithecus. A two million year old endocast of “Dolichopithecus” arvernensis displays a modern cercopithecine sulcal pattern.     

The early evolution of feathers: fossil evidence from Cretaceous amber of France

The developmental stages of feathers are of major importance in the evolution of body covering and the origin of avian flight. Until now, there were significant gaps in knowledge of early morphologies in theoretical stages of feathers as well as in palaeontological material. Here we report fossil evidence of an intermediate and critical stage in the incremental evolution of feathers which has been predicted by developmental theories but hitherto undocumented by evidence from both the recent and the fossil records. Seven feathers have been found in an Early Cretaceous (Late Albian, ca 100 Myr) amber of western France, which display a flattened shaft composed by the still distinct and incompletely fused bases of the barbs forming two irregular vanes. Considering their remarkably primitive features, and since recent discoveries have yielded feathers of modern type in some derived theropod dinosaurs, the Albian feathers from France might have been derived either from an early bird or from a non-avian dinosaur.     

The fossil record and limb disparity of enantiornithines, the dominant flying birds of the Cretaceous

Morphometric and stratigraphic analyses that encompass the known fossil record of enantiornithine birds (Enantiornithes) are presented. These predominantly flighted taxa were the dominant birds of the second half of the Mesozoic; the enantiornithine lineage is known to have lasted for at least 60 million years (Ma), up until the end of the Cretaceous. Analyses of fossil record dynamics show that enantiornithine 'collectorship' since the 1980s approaches an exponential distribution, indicating that an asymptote in proportion of specimens has yet to be achieved. Data demonstrate that the fossil record of enantiornithines is complete enough for the extraction of biological patterns. Comparison of the available fossil specimens with a large data set of modern bird (Neornithes) limb proportions also illustrates that the known forelimb proportions of enantiornithines fall within the range of extant taxa; thus these birds likely encompassed the range of flight styles of extant birds. In contrast, most enantiornithines had hindlimb proportions that differ from any extant taxa. To explore this, ternary diagrams are used to graph enantiornithine limb variation and to identify some morphological oddities ( Otogornis , Gobipteryx ); taxa not directly comparable to modern birds. These exceptions are interesting – although anatomically uniform, and similar to extant avians in their wing proportions, some fossil enantiornithines likely had flight styles not seen among their living counterparts.     

Miocene marmosets: First fossil evidence

The first fossil remains of marmosets, an isolated incisor, premolar, and molar, all similar in size toCallithrix species, have been discovered in the middle Miocene La Venta fauna of Colombia. The M¹ is referred to a new genus and species,Micodon kiotensis, characterized by a fully developed hypocone and low occlusal relief. The P₄ and I¹ resemble those ofCallithrix, suggesting a close affinity with callitrichin marmosets. In combining small size with a four-cusped morphology,Micodon demonstrates the shortcomings of typological definitions of platyrrhine families and suggests that small body size may have preceded the tricuspid molar pattern in marmoset evolution. The 14- to 15-Ma date for the La Venta suggests that marmosets are an at least moderately ancient radiation, contrary to estimates based upon the molecular clock.     

The completeness of the fossil record of mesozoic birds: implications for early avian evolution

Many palaeobiological analyses have concluded that modern birds (Neornithes) radiated no earlier than the Maastrichtian, whereas molecular clock studies have argued for a much earlier origination. Here, we assess the quality of the fossil record of Mesozoic avian species, using a recently proposed character completeness metric which calculates the percentage of phylogenetic characters that can be scored for each taxon. Estimates of fossil record quality are plotted against geological time and compared to estimates of species level diversity, sea level, and depositional environment. Geographical controls on the avian fossil record are investigated by comparing the completeness scores of species in different continental regions and latitudinal bins. Avian fossil record quality varies greatly with peaks during the Tithonian-early Berriasian, Aptian, and Coniacian-Santonian, and troughs during the Albian-Turonian and the Maastrichtian. The completeness metric correlates more strongly with a 'sampling corrected' residual diversity curve of avian species than with the raw taxic diversity curve, suggesting that the abundance and diversity of birds might influence the probability of high quality specimens being preserved. There is no correlation between avian completeness and sea level, the number of fluviolacustrine localities or a recently constructed character completeness metric of sauropodomorph dinosaurs. Comparisons between the completeness of Mesozoic birds and sauropodomorphs suggest that small delicate vertebrate skeletons are more easily destroyed by taphonomic processes, but more easily preserved whole. Lagerst?tten deposits might therefore have a stronger impact on reconstructions of diversity of smaller organisms relative to more robust forms. The relatively poor quality of the avian fossil record in the Late Cretaceous combined with very patchy regional sampling means that it is possible neornithine lineages were present throughout this interval but have not yet been sampled or are difficult to identify because of the fragmentary nature of the specimens.     

Exceptionally preserved North American Paleogene metatherians: adaptations and discovery of a major gap in the opossum fossil record

A major gap in our knowledge of the evolution of marsupial mammals concerns the Paleogene of the northern continents, a critical time and place to link the early history of metatherians in Asia and North America with the more recent diversification in South America and Australia. We studied new exceptionally well-preserved partial skeletons of the Early Oligocene fossil Herpetotherium from the White River Formation in Wyoming, which allowed us to test the relationships of this taxon and examine its adaptations. Herpetotheriidae, with a fossil record extending from the Cretaceous to the Miocene, has traditionally been allied with opossums (Didelphidae) based on fragmentary material, mainly dentitions. Analysis of the new material reveals that several aspects of the cranial and postcranial anatomy, some of which suggests a terrestrial lifestyle, distinguish Herpetotherium from opossums. We found that Herpetotherium is the sister group to the crown group Marsupialia and is not a stem didelphid. Combination of the new palaeontological data with molecular divergence estimates, suggests the presence of a long undocumented gap in the fossil record of opossums extending some 45Myr from the Early Miocene to the Cretaceous.     

Plant hemoglobins: a molecular fossil record for the evolution of oxygen transport

The evolution of oxygen transport hemoglobins occurred on at least two independent occasions. The earliest event led to myoglobin and red blood cell hemoglobin in animals. In plants, oxygen transport "leghemoglobins" evolved much more recently. In both events, pentacoordinate heme sites capable of inert oxygen transfer evolved from hexacoordinate hemoglobins that have unrelated functions. High sequence homology between hexacoordinate and pentacoordinate hemoglobins in plants has poised them for potential structural analysis leading to a molecular understanding of this important evolutionary event. However, the lack of a plant hexacoordinate hemoglobin structure in the exogenously ligand-bound form has prevented such comparison. Here we report the crystal structure of the cyanide-bound hexacoordinate hemoglobin from barley. This presents the first opportunity to examine conformational changes in plant hexacoordinate hemoglobins upon exogenous ligand binding, and reveals structural mechanisms for stabilizing the high-energy pentacoordinate heme conformation critical to the evolution of reversible oxygen binding hemoglobins.     

The fossil record of North American mammals: evidence for a Paleocene evolutionary radiation

Paleontologists long have argued that the most important evolutionary radiation of mammals occurred during the early Cenozoic, if not that all eutherians originated from a single common post-Cretaceous ancestor. Nonetheless, several recent molecular analyses claim to show that because several interordinal splits occurred during the Cretaceous, a major therian radiation was then underway. This claim conflicts with statistical evidence from the well-sampled latest Cretaceous and Cenozoic North American fossil record. Paleofaunal data confirm that there were fewer mammalian species during the latest Cretaceous than during any interval of the Cenozoic, and that a massive diversification took place during the early Paleocene, immediately after a mass extinction. Measurement data show that Cretaceous mammals were on average small and occupied a narrow range of body sizes; after the Cretaceous-Tertiary mass extinction, there was a rapid and permanent shift in the mean. The fact that there was an early Cenozoic mammalian radiation is entirely compatible with the existence of a few Cretaceous splits among modern mammal lineages.     

The arboreal leaping theory of the origin of pterosaur flight

Three theories about the origin of flight in pterosaurs have been proposed: 1) the arboreal parachuting theory (passive falling from trees leading to gliding and eventually to powered flight); 2) the cursorial theory (bipedal running and leaping leading directly to powered flight); and 3) the arboreal leaping theory (active leaping between branches and trees leading to powered flight). The available evidence as to the functional morphology of pterosaurs, and in particular their hindlimb, is reviewed and used to test the three theories. Pterosaurs were well suited for arboreality and their hindlimb morphology argues against cursoriality, but supports an arboreal leaping lifestyle for early pterosaurs or their immediate ancestors.     

The evolutionary history of Fagus in western Eurasia: Evidence from genes, morphology and the fossil record

 Fagus (beech) is among the most abundant and economically important genera of broad-leaved trees in northern hemisphere temperate forests. The number of modern taxa present in Europe and Asia Minor has long been a matter of debate and up to five species have been recognised. To resolve taxonomic and phylogenetic relationships we conducted morphological and molecular genetic analyses in western Eurasiatic taxa and evaluated palaeontological evidence. To place our findings from western Eurasiatic populations in a broader context additional East Asiatic and North American species of the same subgenus Fagus as well as two species of the subgenus Engleriana were included in our study. The morphological features exhibited in western Eurasiatic populations of Fagus show a west-east gradient that is characterised by strongly overlapping variability between geographical races. Fagus populations from Asia Minor exhibit an even higher variability that is also reflected in their genetic variability of nuclear rDNA internal transcribed spacer (ITS) sequences. The intraspecific genetic variability recorded here is in conflict with previous ITS studies in Fagus. The high amount of ITS polymorphism within Fagus from western Eurasia along with the clinal variation observed for morphological characters suggest the presence of only a single species, Fagus sylvatica L., in Europe and Asia Minor. Previously recognised taxa such as F. orientalis Lipsky and Fagus moesiaca (Maly) Czeczott should therefore be treated as synonyms of Fagus sylvatica. Although species belonging to the subgenus Engleriana were genetically distinct from species of the subgenus Fagus, relationships within the subgenus Fagus could not be clearly resolved. A reason for this could be the low rate of diversification in Fagus during the early phase of range expansion of the genus in the Oligocene period as indicated by the uniformity of leaf and cupule/nut fossils. This may account for the low overall ITS divergence and the high degree of polymorphism encountered in the subgenus Fagus and points to a late differentiation of western Eurasiatic and eastern Asiatic species. Area disruptions during the Pleistocene and the post-glacial recolonisation of western Europe appear to have caused the west-east gradient that is apparent in modern Fagus of western Eurasia but absent in Late Tertiary ancestors of Fagus sylvatica. Received June 22, 2001 Accepted February 25, 2002     

Climatic influences on species: Evidence from the fossil record

The detailed Neogene and Quaternary paleoclimatic reconstructions now available provide a means to test how species respond to environmental change. Paleontologic studies of marine organisms show that climatic change causes evolution (via cladogenesis and anagenesis), ecophenotypic variation, migration, morphologic stasis and extinction. Evolution during climatic change is a rare event relative to the number of climatic cycles that have occurred, but climate-related environmental barriers, usually temperature, may play an important role in the isolation of populations during allopatric speciation.     

When Earth started blooming: insights from the fossil record

Recent palaeobotanical studies have greatly increased the quantity and quality of information available about the structure and relationships of Cretaceous angiosperms. Discoveries of extremely well preserved Cretaceous flowers have been especially informative and, combined with results from phylogenetic analyses of extant angiosperms (based mainly on molecular sequence data), have greatly clarified important aspects of early angiosperm diversification. Nevertheless, many questions still persist. The phylogenetic origin of the group itself remains as enigmatic as ever and, in some cases, newly introduced techniques from molecular biology have given confusing results. In particular, relationships between the five groups of extant seed plants remain uncertain, and it has sometimes proved difficult to reconcile estimates of the time of divergence between extant lineages made using a 'molecular clock' with the fossil record. One result, however, is becoming increasingly clear: a great deal of angiosperm diversity is extinct. Some groups of angiosperms were evidently more diverse in the past than they are today. In other cases, fossils defy assignment to extant groups at the family level or below. This raises the possibility that evolutionary conclusions based solely upon extant taxa that are merely relics of groups that were once much more diverse might be misled by the effects of extinction. It also introduces the possibility that some early enigmatic fossils might represent lineages that diverged from the main line of angiosperm evolution below the most recent common ancestor of all extant taxa. These, and other questions, are among those that need to be addressed by future palaeobotanical research.     

Cattle and chemokines: evidence for species-specific evolution of the bovine chemokine system

The chemokine system comprises a family of small chemoattractant molecules that have roles in both the healthy and diseased organism. Chemokines act by binding specific receptors on the target cell surface and inducing chemotaxis. The human chemokine system is well characterized, with approximately fifty chemokines identified that fall into four families. The chemokines and their receptors are promiscuous in that one chemokine can often bind several receptors, and vice versa. Study of the bovine chemokine system has been restricted to date to a handful of chemokines, and the identification of bovine chemokines is largely based on the closest human homologue. This method of identification is prone to error and may result in the misassumption of function of a particular chemokine. Here, we review current knowledge of bovine chemokines and reassess the bovine chemokine system based on phylogenetic and syntenic approaches. The bovine chemokine system, for the most part, shows high similarity to the chemokine system of other mammals such as humans; however, differences have been identified. Cattle possess fewer chemokines than humans, yet also possess chemokines that have no obvious homologue in the human system. These 'missing' and 'novel' chemokines may represent functional differences between the bovine and human chemokine systems that may affect the way in which these species are able to respond to specific pathogen repertoires.     

Hominin cognitive evolution: identifying patterns and processes in the fossil and archaeological record

As only limited insight into behaviour is available from the archaeological record, much of our understanding of historical changes in human cognition is restricted to identifying changes in brain size and architecture. Using both absolute and residual brain size estimates, we show that hominin brain evolution was likely to be the result of a mix of processes; punctuated changes at approximately 100 kya, 1 Mya and 1.8 Mya are supplemented by gradual within-lineage changes in Homo erectus and Homo sapiens sensu lato. While brain size increase in Homo in Africa is a gradual process, migration of hominins into Eurasia is associated with step changes at approximately 400 kya and approximately 100 kya. We then demonstrate that periods of rapid change in hominin brain size are not temporally associated with changes in environmental unpredictability or with long-term palaeoclimate trends. Thus, we argue that commonly used global sea level or Indian Ocean dust palaeoclimate records provide little evidence for either the variability selection or aridity hypotheses explaining changes in hominin brain size. Brain size change at approximately 100 kya is coincident with demographic change and the appearance of fully modern language. However, gaps remain in our understanding of the external pressures driving encephalization, which will only be filled by novel applications of the fossil, palaeoclimatic and archaeological records.