贵州威宁及邻近地区新生界中再沉积有孔虫

８０年代,当时的一些主要报纸和有关杂志相继报道过贵州威宁及其邻近地区上第三系中曾发现一批海相有孔虫化石,由此推断云贵高原曾受到晚第三纪的海侵。经过笔者鉴定,这批有孔虫为再沉积的石炭纪标本,其中不仅有非Ｔｉｎｇ小有孔虫,还有Ｔｉｎｇ类,从Ｔ类化石分析,其时代无疑为早石灰世,从而匡正了对云贵高原新生代地质历史的认识。     

Origin of planktotrophy--evidence from early molluscs

The size of early ontogenetic shells (protoconchs) of ancient benthic molluscs suggests that feeding larvae occurred at about 490 myr (approximately, transition from Cambrian to Ordovician). Most studied Ordovician protoconchs were smaller than Cambrian ones, indicating smaller Ordovician eggs and hatchlings. This suggests substitution of nutritious reserve matter such as yolk by plankton as an energy source for larvae. The observed size change represents the first direct empiric evidence for a late Cambrian to Ordovician switch to planktotrophy in invertebrate larvae. It corroborates previous hypotheses about a possible polyphyly of planktotrophy. These hypotheses were primarily based on molecular clock data of extant clades with different types of larva, change in the overall body size, as well as increasing predation pressure on Early Paleozoic sea floors. The Early Ordovician is characterized by an explosive radiation of benthic suspension feeders and it was suggested that planktotrophy would prolongate escape from benthic predation on hatchlings. This biological escalation hypothesis does not fully explain why planktotrophy and suspension feeding became important at the same time, during a major biodiversification. An additional factor that probably included availability of nutrients must have played a role. We speculate that an increasing nutrient supply and availability of photoautotrophic plankton in world oceans have facilitated both planktotrophy and suspension feeding, which does not exclude a contemporaneous predation-driven escalation. It is very likely that the evolution of planktotrophy as well as increasing predation contributed to the Ordovician radiation.     

Speciation durations and Pleistocene effects on vertebrate phylogeography.

An approach applied previously to avian biotas is extended in this paper to other vertebrate classes to evaluate Pleistocene phylogeographic effects and to estimate temporal spans of the speciation process (speciation durations) from mitochondrial (mt) DNA data on extant taxa. Provisional molecular clocks are used to date population separations and to bracket estimates of speciation durations between minimum and maximum values inferred from genetic distances between, respectively, extant pairs of intraspecific phylogroups and sister species. Comparisons of genetic-distance trends across the vertebrate classes reveal the following: (i) speciation durations normally entail at least two million years on average; (ii) for mammals and birds, Pleistocene conditions played an important role in initiating phylogeographic differentiation among now-extant conspecific populations as well as in further sculpting pre-existing phylogeographic variety into many of today''s sister species; and (iii) for herpetofauna and fishes, inferred Pleistocene biogeographic influences on present-day taxa differ depending on alternative but currently plausible mtDNA rate calibrations.     

Ecological implications of molluscan ontogenetic strategies - examples from aquatic ecosystems of the Cenozoic Iberian Peninsula

Molluscs from marginal marine and intra-continental basins of the Iberian Peninsula are described with special emphasis on the early ontogenetic shell formation, which reflects the embryogenesis and larval ecology. The fossils, covering a time span from the Early Oligocene to the Early Pleistocene, are compared to contemporaneous fossil faunas of the Mediterranean and Paratethys, and to extant Mediterranean faunas. Larval shells occur in bivalves and gastropods of Upper Tortonian coastal lagoons near Crevillente (Alicante), indicating marine larval stages and a connection of the adult habitat with the open sea. The euryhaline marginal marine gastropods display planktotrophic larval shells, which enable a marine distribution, but prevented generally euryhaline genera, such as Granulolabium and Terebralia (Cerithioidea, Potamididae), from colonizing continental saline ecosystems. The establishment of athalassic saline populations implies the preadaptational loss of planktotrophy. For the first time lecithotrophic larval development in an athalassic saline system is documented for Potamides gaudryi (Cerithioidea, Potamididae) from the late Middle to early Upper Miocene of the Duero Basin. With regard to the early ontogenetic development, P. gaudryi is distinguished from its possible descendant, the extant Potamides conicus (Blainville, 1829), which represents a direct developer that lacks any larval stage. In comparison to direct development, lecithotrophic larval development was advantageous in the colonization of temporary habitats, such as flood areas. Two different modes of direct development with hatching of crawling young are documented: Feeding on embryonic yolk until the hatching stage and adelphophagy. Adelphophagous embryonic development appears to be advantageous in neritids, thiarids and pulmonates that live in habitats with strong predation of juvenile fishes based on the advanced developmental stage and larger shell size of the hatchlings.     

Ancient fossil specimens of extinct species are genetically more distant to an outgroup than extant sister species are

There exists a remarkable correlation between genetic distance as measured by protein or DNA dissimilarity and time of species divergence as inferred from fossil records. This observation has provoked the molecular clock hypothesis. However, data inconsistent with the hypothesis have steadily accumulated in recent years from studies of extant organisms. Here the published DNA and protein sequences from ancient fossil specimens were examined to see if they would support the molecular clock hypothesis. The hypothesis predicts that ancient specimens cannot be genetically more distant to an outgroup than extant sister species are. Also, two distinct ancient specimens cannot be genetically more distant than their extant sister species are. The findings here do not conform to these predictions. Neanderthals are more distant to chimpanzees and gorillas than modern humans are. Dinosaurs are more distant to frogs than extant birds are. Mastodons are more distant to opossums than other placental mammals are. The genetic distance between dinosaurs and mastodons is greater than that between extant birds and mammals. Therefore, while the molecular clock hypothesis is consistent with some data from extant organisms, it has yet to find support from ancient fossils. Far more damaging to the hypothesis than data from extant organisms, which merely question the constancy of mutation rate, the study of ancient fossil organisms here challenges for the first time the fundamental premise of modern evolution theory that genetic distances had always increased with time in the past history of life on Earth.     

The disparity of priapulid, archaeopriapulid and palaeoscolecid worms in the light of new data

Priapulids and their extinct relatives, the archaeopriapulids and palaeoscolecids, are vermiform, carnivorous ecdysozoans with an armoured, extensible proboscis. These worms were an important component of marine communities during the Palaeozoic, but were especially abundant and diverse in the Cambrian. Today, they comprise just seven genera in four families. Priapulids were among the first groups used to test hypotheses concerning the morphological disparity of Cambrian fossils relative to the extant fauna. A previous study sampled at the generic level, concluding that Cambrian genera embodied marginally less morphological diversity than their extant counterparts. Here, we sample predominantly at the species level and include numerous fossils and some extant forms described in the last fifteen years. Empirical morphospaces for priapulids, archaeopriapulids and palaeoscolecids are relatively insensitive to changes in the taxon or character sample: their overall form has altered little, despite the markedly improved sampling. Cambrian and post-Cambrian genera occupy adjacent rather than broadly overlapping regions of these spaces, and Cambrian species still show lower morphological disparity than their post-Cambrian counterparts. Crucially, the significance of this difference has increased with improved taxon sampling over research time. In contrast with empirical morphospaces, the phylogeny of priapulids, archaeopriapulids and palaeoscolecids derived from morphological characters is extremely sensitive to details of taxon sampling and the manner in which characters are weighted. However, the extant Priapulidae and Halicryptidae invariably resolve as sister families, with this entire clade subsequently being sister group to the Maccabeidae. In our most inclusive trees, the extant Tubiluchidae are separated from these other living taxa by a number of small, intervening fossil clades.     

Supertree analyses of the roles of viviparity and habitat in the evolution of atherinomorph fishes

Using supertree phylogenetic reconstructions, we investigate how livebearing and freshwater adaptations may have shaped evolutionary patterns in the Atherinomorpha, a large clade (approximately 1500 extant species) of ray-finned fishes. Based on maximum parsimony reconstructions, livebearing appears to have evolved at least four times independently in this group, and no reversions to the ancestral state of oviparity were evident. With respect to habitat, at least five evolutionary transitions apparently occurred from freshwater to marine environments, at least two transitions in the opposite direction, and no clear ancestral state was identifiable. All viviparous clades exhibited more extant species than their oviparous sister taxa, suggesting that transitions to viviparity may be associated with cladogenetic diversification. Transitions to freshwater were usually, but not invariably associated with increased species richness, but the trend was, overall, not significant among sister clades. Additionally, we investigated whether livebearing and freshwater adaptations are currently associated with elevated risks of extinction as implied by species' presence on the 2004 IUCN Red List. Despite being correlated with decreased brood size, livebearing has not significantly increased extinction risk in the Atherinomorpha. However, freshwater species were significantly more likely than marine species to be listed as endangered.     

Middle Eocene Pelagornithidae and Gaviiformes (Aves) from the Ukrainian Paratethys

Abstract: We describe avian remains from Novopskov, a new middle Eocene marine locality in Ukraine. The fossils constitute the most substantial collection of Palaeogene bird bones from Eastern Europe and contribute to a better knowledge of the Paratethyan seabird fauna. Most of the specimens belong to Pelagornithidae (bony‐toothed birds), and two species of very different size can be distinguished. The larger of these is tentatively referred to Dasornis sp., the smaller to Odontopteryx toliapica. The specimens include skeletal elements that were not described for Palaeogene bony‐toothed birds and document previously unknown morphological differences between Palaeogene and Neogene Pelagornithidae. It is argued that the purported crane Eobalearica tugarinovi, from the middle Eocene of Kyrgyzstan, is probably also a bony‐toothed bird. A new genus and species of small Gaviiformes, Colymbiculus udovinchenkoi, is described, which is the earliest fossil record of a loon from Europe, preceding the next oldest specimens by more than 10 myr. The Ukrainian fossils document profound differences between middle Eocene and extant marine avifaunas of Europe, and whereas the middle Eocene Paratethyan avifauna appears to have been similar to that of the North Sea with regard to pelagornithid diversity, the absence of prophaethontids and relative abundance of Gaviiformes may indicate faunistic differences concerning the remaining seabirds.     

Evidence for targeted elasmobranch predation on thalassinidean shrimp in the Miocene Taliao Formation,NE Taiwan

Terrestrial and marine invertebrate organisms both leave records of their activities in the sediment in the form of trace fossils, at least during certain stages of their ontogeny. In contrast, trace fossils produced by vertebrate organisms are scarce, although terrestrial trace fossils provide exclusive insights into the social behaviour of their producers. In the marine realm, vertebrate trace fossils are relatively rare, difficult to identify and problematic to interpret. However, in certain settings, observations on serendipitously preserved and exposed trace fossils can shed light on the predatory behaviour of marine vertebrates. In Miocene outer shelf to nearshore sandstones of the Taliao Formation in NE Taiwan, large numbers of bowl‐shaped trace fossils can be observed. Morphology and size range (diameter typically 10–30 cm, average depth around 10 cm) of these trace fossils agree well with feeding traces of modern stingrays, and the trace fossil Piscichnus waitemata, which has been attributed to bottom feeding rays. Stingrays direct a jet of water from their mouths to excavate a bowl‐shaped pit to expose their prey. In the material filling the excavated bowl, broken pieces of two other common trace fossils, Ophiomorpha and Schaubcylindrichnus, are often found, and in a number of cases, vertical shafts of Ophiomorpha surrounded by dispersed pieces of wall material have been observed. In contrast, surrounding sediment rarely contains this kind of broken pieces of wall material. These observations clearly indicate that stingrays specifically targeted the producers of the trace fossils: thalassinoid crustaceans and worms, respectively. The targeted predation of these relatively deep burrowers furthermore suggests that the rays used their electroreceptive organs to locate the prey; as such, direct targeting of buried prey only based on olfactory senses has been shown to be ineffective in experiments with extant myliobatiform rays.     

Phylogeny of extant and fossil Juglandaceae inferred from the integration of molecular and morphological data sets

It is widely acknowledged that integrating fossils into data sets of extant taxa is imperative for proper placement of fossils, resolution of relationships, and a better understanding of character evolution. The importance of this process has been further magnified because of the crucial role of fossils in dating divergence times. Outstanding issues remain, including appropriate methods to place fossils in phylogenetic trees, the importance of molecules versus morphology in these analyses, as well as the impact of potentially large amounts of missing data for fossil taxa. In this study we used the angiosperm clade Juglandaceae as a model for investigating methods of integrating fossils into a phylogenetic framework of extant taxa. The clade has a rich fossil record relative to low extant diversity, as well as a robust molecular phylogeny and morphological database for extant taxa. After combining fossil organ genera into composite and terminal taxa, our objectives were to (1) compare multiple methods for the integration of the fossils and extant taxa (including total evidence, molecular scaffolds, and molecular matrix representation with parsimony [MRP]); (2) explore the impact of missing data (incomplete taxa and characters) and the evidence for placing fossils on the topology; (3) simulate the phylogenetic effect of missing data by creating "artificial fossils"; and (4) place fossils and compare the impact of single and multiple fossil constraints in estimating the age of clades. Despite large and variable amounts of missing data, each of the methods provided reasonable placement of both fossils and simulated "artificial fossils" in the phylogeny previously inferred only from extant taxa. Our results clearly show that the amount of missing data in any given taxon is not by itself an operational guideline for excluding fossils from analysis. Three fossil taxa (Cruciptera simsonii, Paleoplatycarya wingii, and Platycarya americana) were placed within crown clades containing living taxa for which relationships previously had been suggested based on morphology, whereas Polyptera manningii, a mosaic taxon with equivocal affinities, was placed firmly as sister to two modern crown clades. The position of Paleooreomunnea stoneana was ambiguous with total evidence but conclusive with DNA scaffolds and MRP. There was less disturbance of relationships among extant taxa using a total evidence approach, and the DNA scaffold approach did not provide improved resolution or internal support for clades compared to total evidence, whereas weighted MRP retained comparable levels of support but lost crown clade resolution. Multiple internal minimum age constraints generally provided reasonable age estimates, but the use of single constraints provided by extinct genera tended to underestimate clade ages.     

Dental metric comparisons of Morotopithecus and Afropithecus: implications for the validity of the genus Morotopithecus

Morotopithecus bishopi and Afropithecus turkanensis are two large-bodied hominoid primates from early Miocene deposits of eastern Africa. Researchers have used both cranial and postcranial characters to distinguish these two species. Unfortunately, of the fossil material attributed to each, only the face, palate, and upper dentition are preserved well enough in both species for direct comparisons. There are currently no known directly comparable postcranial elements. In this study, we reevaluated dental characters argued to distinguish the type specimens of Morotopithecus from Afropithecus: relative size of the upper premolars and M3. Exact randomization methods were used to address two questions. First, is it possible to find the degree of dental-size difference observed between Morotopithecus (UMP 62-11) and Afropithecus (KNM-WK 16999) within extant African hominoids? Second, what is the probability of observing the levels of difference found between the fossils among pairs of extant individuals? Metric differences in relative premolar and M3 size were calculated between all possible pairs within the extant sample and the observed difference of the fossil pair was then compared to the resulting distribution of extant pairs. The observed size differences for all comparisons in the fossil teeth were well within the variation observed in the extant African hominoid samples (p>0.05). In light of these results and other currently available cranial evidence, we suggest that the type specimens of Morotopithecus and Afropithecus are not different enough to support taxonomic distinction.     

Liaoxia Cao et S.Q. Wu (Gnetales): ephedroids from the Early Cretaceous Yixian Formation in Liaoning, northeastern China

Gnetalean compression-impression fossils are described from the Early Cretaceous Yixian Formation, Liaoning Province, north-eastern China, and assigned to six species of Liaoxia Cao et S.Q. Wu. The fossils have opposite-decussate phyllotaxis and cones comprising 2–12 pairs of bracts. Ovulate cones have seeds typically in a distal position. The species differ from each other and from previously described fossils in the absence or presence of leaves, shape of cones and seeds, and shape and position of cone bracts. The species of Liaoxia are probably close relatives of extant species of Ephedra L., but diagnostic reproductive details that could confirm this hypothesis are not preserved. The restricted information in the fossils and the poorly understood morphological diversity of extant Ephedra, prevent assignment of the fossils to any particular subgroup of Ephedra, as well as an explicit exclusion of them from the extant genus.     

Look in the trees: Hylobatids as evolutionary models for extinct hominins

Studying extant apes is of central importance to paleoanthropology. This approach is informative in inferring how hominin skeletal morphology reflects phylogeny, behavior, development, and ecological context. Traditionally, great apes have dominated the paleoanthropological literature as extant analogs for extinct hominins, to the exclusion of their phylogenetic sister group, the hylobatids. Phylogenetic proximity, large body size, and high encephalization quotients may have contributed to decisions to use great apes as models for hominins. However, if we reexamine hylobatids as extant models for extinct hominins—using modern phylogenetic, behavioral, and ecological data—this clade is uniquely poised to inform future frameworks in paleoanthropology. The following features make hylobatids strong analogs for extinct hominins: taxonomic diversity, the timing of diversification, hybridization between species, small body size, and reduced sexual dimorphism. Based on these shared features, hylobatids offer future opportunities to paleoanthropology, and provide a much richer extant analog than is currently recognized.     

Life‐history strategies indicate live‐bearing in Nothosaurus (Sauropterygia)

In Sauropterygia, a diverse group of Mesozoic marine reptiles, fossil evidence of viviparity (live‐bearing) only exists for Pachypleurosauria and Plesiosauria, and was assumed to also be the case for nothosaurs. Previous studies have successfully applied an extant squamate model to sauropterygian life‐history traits. In extant squamates, oviparity and viviparity are associated with differences in life‐history trait combinations. We establish growth curves for Nothosaurus specimens based on their humeral histology. We then analyse life‐history traits derived from these curves and compare inferred traits to those of modern squamates and pachypleurosaurs to assess their reproduction mode. We show that birth to adult size ratios (i.e. birth size divided by the mother's size) provide good estimates of clutch sizes in extant squamates and in viviparous extinct marine reptiles, but these ratios cannot discriminate viviparous and oviparous squamates. Thus, large ratios do not indicate viviparity in fossil taxa to which the extant squamate model is applicable. Applying differences in birth size, age at maturation, and maximum longevity that are observed between extant viviparous and oviparous squamates to our Nothosaurus sample, we identified 7 out of 24 specimens as being potentially viviparous. Conversely, they suggested oviparity for many nothosaurs but also for many pachypleurosaur samples. Under the assumption that the entire clade Pachypleurosauria was viviparous, the majority of nothosaurs would also have been viviparous as they comprised trait combinations similar to those seen in pachypleurosaurs. Overall, this suggests that within nothosaurs and pachypleurosaurs both reproduction modes existed in different taxa.     

Orycteropus (Tubulidentata, Mammalia) from Langebaanweg and Baard's Quarry, Early Pliocene of South Africa

Fossil teeth and bones of aardvarks are relatively common at Langebaanweg, an Early Pliocene site in western Cape Province, South Africa. The remains are compatible in size and most details of morphology to extant Orycteropus afer, and are the earliest fossils attributed to this species. Other Late Miocene to Early Pliocene localities in Africa have yielded smaller species of aardvarks, suggesting that the extant lineage evolved in southern Africa. Morphologically the genus Orycteropus has been remarkably conservative since at least the Early Miocene but it witnessed an overall increase in size through the Neogene. The species O. afer has been morphometrically stable since the Early Pliocene. These observations indicate that the evolutionary process in aardvarks is extremely bradytelic. To cite this article: M. Pickford, C. R. Palevol 4 (2005).     

Extant primitively segmented spiders have recently diversified from an ancient lineage

Living fossils are lineages that have retained plesiomorphic traits through long time periods. It is expected that such lineages have both originated and diversified long ago. Such expectations have recently been challenged in some textbook examples of living fossils, notably in extant cycads and coelacanths. Using a phylogenetic approach, we tested the patterns of the origin and diversification of liphistiid spiders, a clade of spiders considered to be living fossils due to their retention of arachnid plesiomorphies and their exclusive grouping in Mesothelae, an ancient clade sister to all modern spiders. Facilitated by original sampling throughout their Asian range, we here provide the phylogenetic framework necessary for reconstructing liphistiid biogeographic history. All phylogenetic analyses support the monophyly of Liphistiidae and of eight genera. As the fossil evidence supports a Carboniferous Euramerican origin of Mesothelae, our dating analyses postulate a long eastward over-land dispersal towards the Asian origin of Liphistiidae during the Palaeogene (39–58 Ma). Contrary to expectations, diversification within extant liphistiid genera is relatively recent, in the Neogene and Late Palaeogene (4–24 Ma). While no over-water dispersal events are needed to explain their evolutionary history, the history of liphistiid spiders has the potential to play prominently in vicariant biogeographic studies.     

Phylogeny of giant clams (Cardiidae: Tridacninae) based on partial mitochondrial 16S rDNA gene sequences.

We have performed the first DNA molecular phylogenetic analysis of giant clams. An approximately 462-nucleotide fragment of the mitochondrial large ribosomal subunit (16S) was sequenced for all eight species of giant clams and two species of an outgroup taxon, the edible cockle Cerastoderma. The data were analyzed using a maximum parsimony approach and a single most parsimonious tree was found. The resulting phylogenetic hypothesis indicates that the genera Hippopus and Tridacna are monophyletic sister taxa. Tridacna (Chametrachea) is the sister taxon to (T. tevoroa (T. derasa + T. gigas)), with these latter three taxa all being placed in a single subgenus, Tridacna (Tridacna). The number of recognized giant clam species has increased by one-third over the last two decades with the discovery of two rare new species having restricted geographic ranges: H. porcellanus (Palau and the Sulu Archipelago) and T. tevoroa (Tonga and Fiji). These two species lack a known fossil record but exhibit greater genetic distances from sister taxa than do extant giant clam species pairs which are recognizable in Neogene strata, e.g., T. gigas/T. derasa and T. maxima/T. squamosa. We propose that the two new species represent ancient relict lineages of Miocene origin.     

Geography best explains global patterns of genetic diversity and postglacial co‐expansion in marine turtles

For many species, climate oscillations drove cycles of population contraction during cool glacial periods followed by expansion during interglacials. Some groups, however, show evidence of uniform and synchronous expansion, while others display differences in the timing and extent of demographic change. We compared demographic histories inferred from genetic data across marine turtle species to identify responses to postglacial warming shared across taxa and to examine drivers of past demographic change at the global scale. Using coalescent simulations and approximate Bayesian computation (ABC), we estimated demographic parameters, including the likelihood of past population expansion, from a mitochondrial data set encompassing 23 previously identified lineages from all seven marine turtle species. For lineages with a high posterior probability of expansion, we conducted a hierarchical ABC analysis to estimate the proportion of lineages expanding synchronously and the timing of synchronous expansion. We used Bayesian model averaging to identify variables associated with expansion and genetic diversity. Approximately 60% of extant marine turtle lineages showed evidence of expansion, with the rest mainly exhibiting patterns of genetic diversity most consistent with population stability. For lineages showing expansion, there was a strong signal of synchronous expansion after the Last Glacial Maximum. Expansion and genetic diversity were best explained by ocean basin and the degree of endemism for a given lineage. Geographic differences in sensitivity to climate change have implications for prioritizing conservation actions in marine turtles as well as for identifying areas of past demographic stability and potential resilience to future climate change for broadly distributed taxa.     

New fossil Progonocimicidae (Hemiptera: Coleorrhyncha: Progonocimicoidea) from the Upper Mesozoic of northeastern China,with a phylogeny of Coleorrhyncha

A new Progonocimicidae species, Cicadocoris anisomeridis sp.n. , with asymmetrical tegmina is described from the Middle Jurassic Jiulongshan Formation in northeastern China. This is the fifth report of Coleorrhyncha from China. A cladistic analysis based on a combination of fossil and extant taxa clarifies the phylogenetic status of the new fossils and allows the reconstruction of inter‐subfamily relationships within the suborder Coleorrhyncha. Coleorrhyncha is monophyletic and divided into two main clades. Progonocimicidae comprises a monophyletic lineage, to which the new fossils belong. The broadly conceived Progonocimicinae and Cicadocorinae, as recognized by earlier authors, are not supported. The monophyly of the family Karabasiidae is also not supported, and its two constituent subfamilies Hoploridiinae and Karabasiinae are raised to family rank. Hoploridiidae is found to be sister group to all extant moss bugs, and Karabasiidae is found to be the monophyletic sister group to Hoploridiidae + all extant moss bugs. This published work has been registered in ZooBank, http://zoobank.org/urn:lsid:zoobank.org:pub:30BC0498‐3B8A‐4650‐BC9D‐02A0C8D870B2 .