A contribution to tropical rain forest taphonomy: retrieval and documentation of chimpanzee remains from Kibale Forest, Uganda

The absence of Pan and Gorilla fossils from Africa has led some to suggest that African rain forests are not conducive to bone preservation. The absence of fossils is unfortunate as it hampers phylogenetic and socioecological interpretations on the divergence of the earliest hominids. For the most part, taphonomic studies have been restricted to cave and open country contexts. With this in mind, we have initiated a taphonomic project in a tropical rain forest, the Kibale Forest of western Uganda. In the course of bone gathering activities over the past 4 years, we have documented the retrieval of skeletal remains representing nine chimpanzees (Pan troglodytes schweinfurthii). Crania and mandibles are most commonly recovered, followed by elements of the axial skeleton, and finally, appendages. Vertical segregation of small compact bones can occur in areas with a soft substrate. Scavenging activity suggests the role of suids, but this has not been proven. Geochemical tests suggest that Kibale soils are neutral and may be conducive to bone preservation. Our independent preliminary data from bone weathering/survival experiments indicate that bones appear undamaged after several years and are able to accumulate on the forest floor. These results contrast with popular assumptions on the potential of African rain forests as potential fossil reservoirs.     

陕西西乡寒武纪幸运期宽川铺生物群网格状微体化石埋藏学与生物属性研究*

磷酸盐化保存是软躯体化石特异埋藏的一个重要途径, 而微生物在软躯体磷酸盐化过程中可能发挥了重要作用。前人通过埋藏学实验发现, 微生物会在动物胚胎等软躯体组织内部快速滋生, 充填生物体内部空间, 以微生物假形的方式复制了生物体的原始形态。但化石的磷酸盐化过程是否与埋藏学实验模拟的过程一致, 目前仍有争议。本次研究在寒武纪早期宽川铺生物群中发现了一类网格状微体化石。此类化石的保存状态可以根据其中丝状微生物滋生的程度分为三种类型, 它们展示了生物从死亡到微生物侵入、滋生, 最后被磷酸盐化的全过程。这些标本显示, 微生物假形在生物软组织磷酸盐化过程中扮演了重要角色, 但并不是化石磷酸盐化的必由之路, 尤其是当生物体具有矿化硬骨骼或者几丁质软骨骼等抗腐性较强的结构时。此类标本多以不完整保存的残片为主, 正反两面结构一致, 具有典型列状排列的近圆形与哑铃形网孔。由于化石结构简单, 生物学性状较少, 因此它们的亲缘关系尚不明确, 是一类需要继续研究的疑难化石。     

The role of iron in the formation of Ediacaran ‘death masks’

The Ediacara biota are an enigmatic group of Neoproterozoic soft-bodied fossils that mark the first major radiation of complex eukaryotic and macroscopic life. These fossils are thought to have been preserved via pyritic “death masks” mediated by seafloor microbial mats, though little about the chemical constraints of this preservational pathway is known, in particular surrounding the role of bioavailable iron in death mask formation and preservational fidelity. In this study, we perform decay experiments on both diploblastic and triploblastic animals under a range of simulated sedimentary iron concentrations, in order to characterize the role of iron in the preservation of Ediacaran organisms. After 28 days of decay, we demonstrate the first convincing “death masks” produced under experimental laboratory conditions composed of iron sulfide and probable oxide veneers. Moreover, our results demonstrate that the abundance of iron in experiments is not the sole control on death mask formation, but also tissue histology and the availability of nucleation sites. This illustrates that Ediacaran preservation via microbial death masks need not be a “perfect storm” of paleoenvironmental porewater and sediment chemistry, but instead can occur under a range of conditions.     

Possible ctenophoran affinities of the Precambrian "sea-pen" Rangea

The Namibian Kuibis Quartzite fossils of Rangea are preserved three-dimensionally owing to incomplete collapse of the soft tissues under the load of instantaneously deposited sand. The process of fossilization did not reproduce the original external morphology of the organism but rather the inner surface of collapsed organs, presumably a system of sacs connected by a medial canal. The body of Rangea had tetraradial symmetry, a body plan shared also by the White Sea Russian fossil Bomakellia and possibly some other Precambrian frond-like fossils. They all had a complex internal anatomy, smooth surface of the body, and radial membranes, making their alleged colonial nature unlikely. Despite a different style of preservation, the Middle Cambrian Burgess Shale frond-like Thaumaptilon shows several anatomical similarities to Rangea. The body plan of the Burgess Shale ctenophore Fasciculus, with its numerous, pinnately arranged comb organs, is in many respects transitional between Thaumaptilon and the Early Cambrian ctenophore Maotianoascus from the Chengjiang fauna of South China. It is proposed that the irregularly distributed dark spots on the fusiform units of the petaloid of Thaumaptilon represent a kind of macrocilia and that the units are homologous with the ctenophoran comb organs. These superficial structures were underlain by the complex serial organs, well represented in the fossils of Rangea. The Precambrian "sea-pens" were thus probably sedentary ancestors of the ctenophores.     

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.     

Experimental analysis of soft‐tissue fossilization: opening the black box

Taphonomic experiments provide important insights into fossils that preserve the remains of decay‐prone soft tissues, tissues that are usually degraded and lost prior to fossilization. These fossils are among the most scientifically valuable evidence of ancient life on Earth, giving us a view into the past that is much less biased and incomplete than the picture provided by skeletal remains alone. Although the value of taphonomic experiments is beyond doubt, a lack of clarity regarding their purpose and limitations, and ambiguity in the use of terminology, are hampering progress. Here we distinguish between processes that promote information retention and those that promote information loss, in order to clarify the distinction between fossilization and preservation. Recognizing distinct processes of decay, mineralization and maturation, the sequence in which they act, and the potential for interactions, has important consequences for analysis of fossils, and for the design of taphonomic experiments. The purpose of well‐designed taphonomic experiments is generally to understand decay, maturation and preservation individually, thus limiting the number of variables involved. Much work remains to be done, but these methodologically reductionist foundations will allow researchers to build towards more complex taphonomic experiments and a more holistic understanding and analysis of the interactions between decay, maturation and preservation in the fossilization of non‐biomineralized remains. Our focus must remain on the key issue of understanding what exceptionally preserved fossils reveal about the history of biodiversity and evolution, rather than on debating the scope and value of an experimental approach.     

甘肃临夏盆地的渐新世巨犀化石

描述了 2种巨犀化石 :霍尔果斯准噶尔巨犀 (Dzungariotheriumorgosense)和牙沟副巨犀(新种 ) (Paraceratheriumyagouensesp .nov.)。新种的主要特征是 :个体小 ;上颊齿齿冠高 ,有薄层白垩质覆盖 ;DP2～M1反前刺大 ,原尖后收缩沟明显 ,次尖有深的前收缩沟 ,中谷和后凹中常有附属小柱等。巨犀的演化历史可能比过去想象的更复杂。Indricotherium、Dzungariotherium和Paraceratherium为代表不同进化水平和支系的 3个属 ,不应合并为Paraceratherium一属。牙沟含巨犀化石层位的地质时代为晚渐新世。     

化石闭壳龟的新发现

闭壳龟(Cuora)是龟科(Emydidae)中的一个现生属,有6个现生种,分布于东亚和东南亚,我国产4种。为该地区龟类动物中的一个小类群,以前未有化石发现。本文记述的是闭壳龟属的一个化石新种(Cuora pitheca,sp.nov.),时代为上新世早期。这是该属龟类的首次化石记录。它的发现,不仅把闭壳龟属的历史从现代推至上新世早期,并为探讨该龟类的进化和分布提供重要资料。     

Continuity and/or Discontinuity in the Pleistocene peopling of Europe?

Today, a number of European fossils are known which can be dated between 500,000 and 900,000 years ago. These remains provide evidence of an early human settlement of Europe, which apparently predates the emergence of Neanderthals. However, the taxonomic attribution of these fossils and their phylogenetic relationship to each other and to Neanderthals remains unclear. Evidence for a direct phylogenetic relationship with Neanderthals or a discontinuity is not yet conclusive. The task is complicated by the fact that the emergence of the Neanderthal population was not abrupt, but progressive. It is probable that the peopling of Europe during the entire Pleistocene was unique and presented from its very origins an “endemic” (a cul-de-sac) character, which may explain that the first traces of fossils in Europe illustrate particularities in comparison those from Africa and from Asia. Further paleontological discoveries will be needed to redefine the status of these features and to improve our understanding of human evolution in Europe.     

Formation and diagenesis of modern marine calcified cyanobacteria

Calcified cyanobacterial microfossils are common in carbonate environments through most of the Phanerozoic, but are absent from the marine rock record over the past 65 Myr. There has been long-standing debate on the factors controlling the formation and temporal distribution of these fossils, fostered by the lack of a suitable modern analog. We describe calcified cyanobacteria filaments in a modern marine reef setting at Highborne Cay, Bahamas. Our observations and stable isotope data suggest that initial calcification occurs in living cyanobacteria and is photosynthetically induced. A single variety of cyanobacteria, Dichothrix sp., produces calcified filaments. Adjacent cyanobacterial mats form well-laminated stromatolites, rather than calcified filaments, indicating there can be a strong taxonomic control over the mechanism of microbial calcification. Petrographic analyses indicate that the calcified filaments are degraded during early diagenesis and are not present in well-lithified microbialites. The early diagenetic destruction of calcified filaments at Highborne Cay indicates that the absence of calcified cyanobacteria from periods of the Phanerozoic is likely to be caused by low preservation potential as well as inhibited formation.     

Biomats, biofilms, and bioglue as preservational agents for arthropod trackways

Due to divergent taphonomic selection, corresponding body and trace fossils are rarely found in the same rocks. In addition to this general rule, arthropod trackways are preferentially preserved in particular settings: (1) lithographic limestones, where toxic bottom waters account for the exceptional preservation of body fossils at the end of their “mortichnial” trackways; (2) estuarine and lacustrine biolaminites that yield blurred surface tracks as well as the sharper undertracks; and (3) Cambrian intertidal sands before the Precambrian/Cambrian substrate revolution had reached this environment. In all these ichnotopes, the original presence of protective microbial films can be inferred from sedimentary structures. By analogy, it is hypothesised that microbes (“bioglue”) may have been involved in the preservation of trackways in eolian dune sands. The absence of arthropod tracks in Ediacaran sands and silts means either that arthropods had not yet evolved or that they were as yet too tiny to pierce the tougher biomats of the time.     

A critique of the chronometric evidence for hominid fossils: I. Africa and the Near East 500-50 ka

The chronometric dating evidence for all hominid fossils from Africa and the Near East that have previously been dated to 500-50 ka is critically assessed using the concept of chronometric hygiene, and these dates are revised using Bayesian statistical analyses where possible. Sixteen relevant hominid sites lacking chronometric evidence are briefly discussed. Chronometric evidence from 37 sites is assessed in detail. The dates for many hominid fossils are poorly constrained, with a number dated by comparisons of faunal assemblages-a method that does not have good chronological resolution for much of the last million years. For sites with stratigraphic sequences of dates, it is generally possible to refine the dating, but in some cases, the revised chronology is less precise than previous chronologies. Fossils over 200 ka in age tend to be poorly dated, but for the last 200 kyr, dating is better due to the availability of electron-spin-resonance and thermoluminescence dating. Consideration of the chronologies favored by the proponents of the out-of-Africa and multiregional hypotheses of human evolution shows their selectivity. The chronological assessment of the fossils here is compatible with either hypothesis. If evolutionary schemes that do not rely on the morphology of the hominid fossils to decide the sequence of fossils are to be built, then further dating is required, alongside full publication of existing dates.     

The original colours of fossil beetles

Structural colours, the most intense, reflective and pure colours in nature, are generated when light is scattered by complex nanostructures. Metallic structural colours are widespread among modern insects and can be preserved in their fossil counterparts, but it is unclear whether the colours have been altered during fossilization, and whether the absence of colours is always real. To resolve these issues, we investigated fossil beetles from five Cenozoic biotas. Metallic colours in these specimens are generated by an epicuticular multi-layer reflector; the fidelity of its preservation correlates with that of other key cuticular ultrastructures. Where these other ultrastructures are well preserved in non-metallic fossil specimens, we can infer that the original cuticle lacked a multi-layer reflector; its absence in the fossil is not a preservational artefact. Reconstructions of the original colours of the fossils based on the structure of the multi-layer reflector show that the preserved colours are offset systematically to longer wavelengths; this probably reflects alteration of the refractive index of the epicuticle during fossilization. These findings will allow the former presence, and original hue, of metallic structural colours to be identified in diverse fossil insects, thus providing critical evidence of the evolution of structural colour in this group.     

The fossil pupa Simulimima and the evidence it provides for the Jurassic origin of the Simuliidae (Diptera)

Abstract. Examination of the Middle Jurassic dipteran pupal fossil Simulimima grandis Kalugina shows it to possess the pupal diagnostic characters of Simuliidae and to be not significantly distinguishable from the pupa of modern Prosimulium . The nominal monotypic genus Simulimima Kalugina is assigned to that family, but provisionally maintained as valid in the absence of knowledge of associated life stages. The holotype and only specimen of S. grandis is redescribed and illustrated photographically and by line drawings, with emphasis on features which pertain to its family placement. Unambiguous assignment to Simuliidae implies an earlier Mesozoic origin for the blackflies than previously evidenced by available fossils, and it is suggested that the origins of the Simuliidae go back to Lower Jurassic times.     

What Does Palaeontology Contribute to Systematics in a Molecular World?

Palaeontology provides the only direct record for morphological and genetic change through time and uniquely contributes to systematics in two ways: by providing access to denser taxon sampling than is otherwise possible and by dating divergence times. Claims that ancient DNA has survived millions of years in certain fossils suggested the possibility that palaeontology could contribute directly to molecular systematic studies. Unfortunately, none of the supposed geologically ancient DNA records stands up to detailed scrutiny and fossils therefore contribute primarily through the morphological information they preserve. Denser taxon sampling can improve the accuracy of phylogenetic estimates primarily through allowing better discrimination of homoplasy from homology. This in turn leads to more accurate hypotheses of character transformation. Denser taxon sampling also offers the opportunity for more accurate rooting, since more characters can be polarized by reference to a stem-group taxon than to an extant sister-group taxon. Missing data can be a problem for fossils, but is not crippling. Finally the temporal order of clade appearances in the fossil record can provide ancillary evidence for selecting a working phylogeny from among a number of equally most parsimonious cladograms.     

Distinguishing heat from light in debate over controversial fossils

Fossil organisms offer our only direct insight into how the distinctive body plans of extant organisms were assembled. However, realizing the potential evolutionary significance of fossils can be hampered by controversy over their interpretation. Here, as a guide to evaluating palaeontological debates, we outline the process and pitfalls of fossil interpretation. The physical remains of controversial fossils should be reconstructed before interpreting homologies, and choice of interpretative model should be explicit and justified. Extinct taxa lack characters diagnostic of extant clades because the characters had not yet evolved, because of secondary loss, or because they have rotted away. The latter, if not taken into account, will lead to the spurious assignment of fossils to basally branching clades. Conflicting interpretations of fossils can often be resolved by considering all the steps in the process of anatomical analysis and phylogenetic placement, although we must accept that some fossil organisms are simply too incompletely preserved for their evolutionary significance to be realized.     

辽南前寒武系兴民村组“类水母”化石新认识

近年来,由于大量可靠的前寒武纪多细胞动物化石的发现,激起了各国学者在前寒武纪地层中寻找多细胞动物化石及其遗迹的热情。华北辽东半岛南部新元古界兴民村组"类水母"化石自上个世纪80年代中期发现以来,一直被大多数学者认为是可能的后生动物化石。然而,笔者通过对"类水母"化石的形态学及生长模式的研究,认为辽南前寒武系兴民村组"类水母"化石可能并非多细胞动物化石,而是一类亲缘关系不明的不具备运动能力的底栖生物化石,该化石具有无限的线性增长方式。关于其生物学属性需要进行进一步的研究。     

Fossils impact as hard as living taxa in parsimony analyses of morphology

Systematists disagree whether data from fossils should be included in parsimony analyses. In a handful of well-documented cases, the addition of fossil data radically overturns a hypothesis of relationships based on extant taxa alone. Fossils can break up long branches and preserve character combinations closer in time to deep splitting events. However, fossils usually require more interpretation than extant taxa, introducing greater potential for spurious codings. Moreover, because fossils often have more "missing" codings, they are frequently accused of increasing numbers of MPTs, frustrating resolution and reducing support. Despite the controversy, remarkably little is known about the effects of fossils more generally. Here we provide the first systematic study, investigating empirically the behavior of fossil and extant taxa in 45 published morphological data sets. First-order jackknifing is used to determine the effects that each terminal has on inferred relationships, on the number of MPTs, and on CI' and RI as measures of homoplasy. Bootstrap leaf stabilities provide a proxy for the contribution of individual taxa to the branch support in the rest of the tree. There is no significant difference in the impact of fossil versus extant taxa on relationships, numbers of MPTs, and CI' or RI. However, adding individual fossil taxa is more likely to reduce the total branch support of the tree than adding extant taxa. This must be weighed against the superior taxon sampling afforded by including judiciously coded fossils, providing data from otherwise unsampled regions of the tree. We therefore recommend that investigators should include fossils, in the absence of compelling and case specific reasons for their exclusion.     

Names for trace fossils: a uniform approach

The taxonomic treatment of trace fossils needs a uniform approach, independent of the ethologic groups concerned. To this aim, trace fossils are rigorously defined with regard to biological taxa and physical sedimentary structures. Potential ichnotaxobases are evaluated, with morphology resulting as the most important criterion. For trace fossils related to bioerosion and herbivory, substrate plays a key role, as well as composition for coprolites. Size, producer, age, facies and preservation are rejected as ichnotaxobases. Separate names for undertracks and other poorly preserved material should gradually be replaced by ichnotaxa based on well-preserved specimens. Recent traces may be identified using established trace fossil taxa but new names can only be based on fossil material, even if the distinction between recent and fossil may frequently remain arbitrary. It is stressed that ichnotaxa must not be incorporated into biological taxa in systematics. Composite trace fossil structures (complex structures made by the combined activity of two or more species) have no ichnotaxonomic standing but compound traces (complex structures made by one individual tracemaker) may be named separately under certain provisions. The following emendations are proposed to the International Code of Zoological Nomenclature: The term 'work of an animal' should be deleted from the code, and ichnotaxa should be based solely on trace fossils as defined herein.     

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.