Early Fossil Record Research Articles

Estimating origination times from the early hominin fossil record.

The age of the earliest recovered fossil evidence of a hominin taxon is all too often equated with that taxon's origination. However, the earliest known fossil record nearly always postdates, sometimes by a substantial period of time, the true origination of a taxon. Here we evaluate the first appearance records of the earliest potential hominins (Sahelanthropus, Ardipithecus, Orrorin), as well as of the genera Australopithecus, Homo, and Paranthropus, to illustrate the considerable uncertainty regarding the actual timing of origin of these taxa. By placing confidence intervals on the first appearance records of early hominin taxa, we can better evaluate patterns of hominin diversity, turnover, and potential correlations with climatic and environmental changes.

Exceptional fossil assemblages confirm the existence of complex Early Triassic ecosystems during the early Spathian

The mass extinction characterizing the Permian/Triassic boundary (PTB; ~ 252 Ma) corresponds to a major faunal shift between the Palaeozoic and the Modern evolutionary fauna. The temporal, spatial, environmental, and ecological dynamics of the associated biotic recovery remain highly debated, partly due to the scarce, or poorly-known, Early Triassic fossil record. Recently, an exceptionally complex ecosystem dated from immediately after the Smithian/Spathian boundary (~ 3 myr after the PTB) was reported: the Paris Biota (Idaho, USA). However, the spatiotemporal representativeness of this unique assemblage remained questionable as it was hitherto only reported from a single site. Here we describe three new exceptionally diverse assemblages of the same age as the Paris Biota, and a fourth younger one. They are located in Idaho and Nevada, and are taxonomic subsets of the Paris Biota. We show that the latter covered a region-wide area and persisted at least partially throughout the Spathian. The presence of a well-established marine fauna such as the Paris Biota, as soon as the early Spathian, indicates that the post-PTB biotic recovery and the installation of complex ecosystems probably took place earlier than often assumed, at least at a regional scale.

Precambrian Paleobiology: Precedents, Progress, and Prospects

In 1859, C. R. Darwin highlighted the “inexplicable” absence of evidence of life prior to the beginning of the Cambrian. Given this lack of evidence and the natural rather than theological unfolding of life’s development Darwin espoused, over the following 50 years his newly minted theory was disputed. At the turn of the 19th century, beginning with the discoveries of C. D. Walcott, glimmerings of the previously “unknown and unknowable” early fossil record came to light – but Walcott’s Precambrian finds were also discounted. It was not until the breakthrough advances of the 1950’s and the identification of modern stromatolites (1956), Precambrian phytoplankton in shales (1950’s), stromatolitic microbes in cherts (1953), and terminal-Precambrian soft-bodied animal fossils (1950’s) that the field was placed on firm footing. Over the following half-century, the development and application of new analytical techniques coupled with the groundbreaking contributions of the Precambrian Paleobiology Research Group spurred the field to its international and distinctly interdisciplinary status. Significant progress has been made worldwide. Among these advances, the known fossil record has been extended sevenfold (from ∼0.5 to ∼3.5 Ga); the fossil record has been shown consistent with rRNA phylogenies (adding credence to both); and the timing and evolutionary significance of an increase of environmental oxygen (∼2.3 Ga), of eukaryotic organisms (∼2.0 Ga), and of evolution-speeding and biota-diversifying eukaryotic sexual reproduction (∼1.2 Ga) have been identified. Nevertheless, much remains to be learned. Such major unsolved problems include the absence of definitive evidence of the widely assumed life-generating “primordial soup”; the timing of the origin of oxygenic photosynthesis; the veracity of postulated changes in global photic-zone temperature from 3.5 Ga to the present; the bases of the advent of eukaryotic sexuality-requiring gametogenesis and syngamy; and the timing of origin and affinities of the small soft-bodied precursors of the Ediacaran Fauna.

A reassessment of the enigmatic diapsid Paliguana whitei and the early history of Lepidosauromorpha.

Lepidosaurs include lizards, snakes, amphisbaenians and the tuatara, comprising a highly speciose evolutionary radiation with widely varying anatomical traits. Their stem-lineage originated by the late middle Permian 259 million years ago, but its early fossil record is poorly documented, obscuring the origins of key anatomical and functional traits of the group. Paliguana whitei, from the Early Triassic of South Africa, is an enigmatic fossil species with the potential to provide information on this. However, its anatomy and phylogenetic affinities remain highly uncertain, and have been debated since its discovery more than 100 years ago. We present microtomographic three-dimensional imaging of the cranial anatomy of P. whitei that clarifies these uncertainties, providing strong evidence for lepidosauromorph affinities based on the structure of the temporal region and the implantation of marginal dentition. Phylogenetic analysis including these new data recovers Paliguana as the earliest known stem-lepidosaur, within a long-lived group of early diverging lepidosauromorphs that persisted to at least the Middle Jurassic. Our results provide insights into cranial evolution on the lepidosaur stem-lineage, confirming that characteristics of pleurodont dental implantation evolved early on the lepidosaur stem-lineage. By contrast, key functional traits related to hearing (quadrate conch) and feeding (streptostyly) evolved later in the lepidosaur crown-group.

A Triassic stem lepidosaur illuminates the origin of lizard-like reptiles.

The early evolution of diapsid reptiles is marked by a deep contrast between our knowledge of the origin and early evolution of archosauromorphs (crocodiles, avian and non-avian dinosaurs) to that of lepidosauromorphs (squamates (lizards, snakes) and sphenodontians (tuataras)). Whereas the former include hundreds of fossil species across various lineages during the Triassic period1, the latter are represented by an extremely patchy early fossil record comprising only a handful of fragmentary fossils, most of which have uncertain phylogenetic affinities and are confined to Europe1-3. Here we report the discovery of a three-dimensionally preserved reptile skull, assigned as Taytalura alcoberi gen. et sp. nov., from the Late Triassic epoch of Argentina that is robustly inferred phylogenetically as the earliest evolving lepidosauromorph, using various data types and optimality criteria. Micro-computed tomography scans of this skull reveal details about the origin of the lepidosaurian skull from early diapsids, suggesting thatseveral traits traditionally associated with sphenodontians in fact originated much earlier in lepidosauromorph evolution. Taytalura suggests that the strongly evolutionarily conserved skull architecture of sphenodontians represents the plesiomorphic condition for all lepidosaurs, that stem and crown lepidosaurs were contemporaries for at least ten million years during the Triassic, and that early lepidosauromorphs had a much broader geographical distribution than has previously been thought.

Sustained high rates of morphological evolution during the rise of tetrapods.

The fish-to-tetrapod transition is one of the most iconic events in vertebrate evolution, yet fundamental questions regarding the dynamics of this transition remain unresolved. Here, we use advances in Bayesian morphological clock modelling to reveal the evolutionary dynamics of early tetrapodomorphs (tetrapods and their closest fish relatives). We show that combining osteological and ichnological calibration data results in major shifts on the time of origin of all major groups of tetrapodomorphs (up to 25 million years) and that low rates of net diversification, not fossilization, explain long ghost lineages in the early tetrapodomorph fossil record. Further, our findings reveal extremely low rates of morphological change for most early tetrapodomorphs, indicating widespread stabilizing selection upon their 'fish' morphotype. This pattern was broken only by elpistostegalians (including early tetrapods), which underwent sustained high rates of morphological evolution for ~30 Myr during the deployment of the tetrapod body plan.

First Fossil Fokienia (Cupressaceae) in South China and Its Palaeogeographic and Palaeoecological Implications

Fokienia A. Henry & H. H. Thomas is a monotypic genus of the Cupressoideae Rich. ex Sweet (Cupressaceae), native to subtropical evergreen mesophytic forests in South China, northern Laos and Vietnam. The fossil record of Fokienia is very scanty, with only one known occurrence of foliage in the Oligocene of Longjing, Jilin, China. Here we report the fossil foliage of Fokienia discovered in the Miocene Erzitang Formation of the Guiping Basin, South China, which is similar to that of the only extant species Fokienia hodginsii in both macromorphological and epidermal features. This species is the earliest fossil record within the modern distribution area of Fokienia and the only fossil species for which morphology and anatomy have been studied in detail. Fossil evidence suggests that the genus Fokienia was present at middle latitudes of the Northern Hemisphere in the Oligocene and spread to South China during the Miocene. Due to physiological adaptations to warm-wet environments and weak cold tolerance, Fokienia migrated southward, as global climate cooling gradually drove it to extinction in the mid-latitudes. The ecological niche of the extant species, and co-existing plant fossils, suggest that the fossil assemblage represents the remains of an evergreen broad-leaved and conifer mixed forest growing under humid and warm Miocene climate.

Tarsal morphology of ischyromyid rodents from the middle Eocene of China gives an insight into the group\u2019s diversity in Central Asia

Ischyromyids are a group of large rodents with the earliest fossil record known from the late Paleocene (Clarkforkian) of North America; they are considered the earliest fossil representatives of Rodentia of modern aspect. Ischyromyids dominated early Paleogene small-mammal assemblages of North America and in the latest Paleocene migrated to western Europe and to Asia; in the latter they survived only to the beginning of the late Eocene, but were never abundant. Here we describe for the first time the calcanei of ischyromyids from the early middle Eocene of the Erlian Basin in Nei Mongol, northern China. These calcanei document the existence of three species. The morphology of the studied tarsal bones overall suggests ambulatory locomotion for these animals (‘slow cursors’), similar to that of the coypu and porcupines, but one form shows more marked cursorial capabilities. These differences show that Chinese ischyromyids, although rare, had attained greater taxonomic diversity by the middle Eocene in Nei Mongol than estimated from dental remains. We also address the question of the morphological and ecological divergence of these ischyromyids in relation to their North American counterparts, as well as the issue of a direct dispersal route from North America to Asia in the early Eocene.

A new fossil from the early Oligocene of Provence (France) increases the diversity of early Gruoidea and adds constraint on the origin of cranes (Gruidae) and limpkin (Aramidae)

Cranes (Gruidae) have a poor early fossil record, and the oldest ascertained fossils hitherto referred to the family (either as crown or stem-representatives) date back to the early or middle Miocene. Other Gruoidea have an even scarcer fossil record. Psophiidae and Aramidae are virtually unknown as fossils, and other fossil representatives of the Gruoidea are difficult to place. Here, we describe a new fossil that sheds new light on the early history of stem Gruidae, a right coracoid in dorsal view preserved on slab in limestone laminites of the early Oligocene « Calcaires de Campagne-Calavon» (Alpes de Haute Provence, France). It is compared with extant and fossil morphologically related taxa, and appears to differ from all extant and fossil relatives in the Gruoidea. The new fossil represents, among the Gruoidea, a new genus and species, Palaeogeranos tourmenti, placed within the clade (Aramidae + Gruidae) that is referred to as epifamily Gruoidae. Within Gruoidae, placement is tentative and we give arguments leading to propose a possible position as a stem Gruidae, a hypothesis to be tested with further discoveries. In this hypothesis, aged around 30 million years, the new fossil suggests that the stem of the Gruidae would date back to at least the earliest Oligocene, which is still compatible with current molecular phylogenetic divergence dates estimations, given the confidence intervals. Palaeogeranos will potentially help refining future calibrations for molecular phylogenetic studies, at least concerning the earliest Gruoidae (Aramidae + Gruidae).

Spatiotemporal variation in completeness of the early cynodont fossil record and its implications for mammalian evolutionary history

AbstractMammals are the only surviving group of Cynodontia, a synapsid clade that first appeared in the fossil record in the late Permian, ~260 million years ago. Using three metrics that capture skeletal completeness, we quantify the quality of the early cynodont fossil record in time and space to evaluate the impact of sampling and preservational biases on our understanding of the group's evolutionary history. There is no consistent global sampling signal for early cynodonts. Completeness of the cynodont fossil record increases across the Permian–Triassic boundary, peaking in the Early to early Late Triassic. This peak is dominated by specimens from southern Africa and South America, where a highly seasonal climate probably favoured preservation. Completeness is generally lower thereafter, correlating with a shift from a Gondwanan to a predominantly Laurasian fossil record. Phylogenetic and stratigraphic congruence in early cynodonts is high, although their fossil record exhibits less skeletal completeness overall than other tetrapod clades, including the contemporaneous anomodont synapsids. This discrepancy could be due to differences in the diagnosability of their fossils, especially for small‐bodied species. Establishing the timing and assembly of derived (‘mammalian’) anatomical features in Cynodontia is obscured by sampling. Two of the major nodes at which acquisition of mammalian features is concentrated (Cynodontia and Mammaliamorpha) suffer from lengthy intervals of poor sampling before becoming abundant parts of tetrapod faunas. Low completeness in these intervals limits our ability to determine when certain ‘key’ mammalian characteristics evolved, or to identify the selective pressures that might have driven their origins.

Ediacaran algal cysts from the Doushantuo Formation, South China

AbstractEarly-middle Ediacaran organic-walled microfossils from the Doushantuo Formation studied in several sections in the Yangtze Gorges area, South China, show ornamented cyst-like vesicles of very high diversity. These microfossils are diagenetically permineralized and observed in petrographic thin-sections of chert nodules. Exquisitely preserved specimens belonging to seven species of Appendisphaera, Mengeosphaera, Tanarium, Urasphaera and Tianzhushania contain either single or multiple spheroidal internal bodies inside the vesicles. These structures indicate reproductive stages, endocyst and dividing cells, respectively, and are preserved at early to late ontogenetic stages in the same taxa. This new evidence supports the algal affiliations for the studied taxa and refutes previous suggestions of Tianzhushania being animal embryo or holozoan. The first record of a late developmental stage of a completely preserved specimen of T. spinosa observed in thin-section demonstrates the interior of vesicles with clusters of identical cells but without any cavity that is diagnostic for recognizing algal cysts vs animal diapause cysts. Various lines of evidence to infer biological affinities of these microfossils – morphology, reproductive characters, spatial arrangement of cells, and biochemical properties of the vesicle wall – are collectively characteristic of algal clades. Recognizing the biological affinities of these microfossils is key to understanding whether animals capable of producing such morphologically complex diapause cysts had an early Ediacaran fossil record (633–610 Ma), or the microfossils were non-animal holozoans or algae as argued herein for Tianzhushania spinosa and other studied microfossils.

Experimental taphonomy of organelles and the fossil record of early eukaryote evolution.

The timing of origin of eukaryotes and the sequence of eukaryogenesis are poorly constrained because their fossil record is difficult to interpret. Claims of fossilized organelles have been discounted on the unsubstantiated perception that they decay too quickly for fossilization. We experimentally characterized the pattern and time scale of decay of nuclei, chloroplasts, and pyrenoids in red and green algae, demonstrating that they persist for many weeks postmortem as physical substrates available for preservation, a time scale consistent with known mechanisms of fossilization. Chloroplasts exhibit greater decay resistance than nuclei; pyrenoids are unlikely to be preserved, but their presence could be inferred from spaces within fossil chloroplasts. Our results are compatible with differential organelle preservation in seed plants. Claims of fossilized organelles in Proterozoic fossils can no longer be dismissed on grounds of plausibility, prompting reinterpretation of the early eukaryotic fossil record and the prospect of a fossil record of eukaryogenesis.

Evidence on vegetative and inflorescence morphology of Chloranthaceae (Angiospermae) from the Early Cretaceous (middle–late Albian) of Spain

The near-basal angiosperm family Chloranthaceae (with four living genera) is prominently represented in the Early Cretaceous fossil record by pollen and flowers, but its leaves, other vegetative parts and inflorescences are less well known. Here, we report impressions of leaves, stems and inflorescences from the middle–late Albian Escucha Formation of Teruel Province (NE Spain) that help redress this imbalance and bring into clearer focus the morphological and systematic diversity of this key group in the early angiosperm radiation. We used parsimony analysis of a morphological dataset of living and fossil Chloranthaceae to evaluate the position of the fossils on a molecular-based tree of extant taxa. Todziaphyllum elongatum gen. et sp. nov., with festooned semicraspedodromous venation and asymmetrical chloranthoid teeth, is most parsimoniously placed on the stem lineage of the living genus Hedyosmum. Leaves of Alcainea eklundiae gen. et sp. nov., with festooned semicraspedodromous venation and symmetric teeth, occur attached to stems in opposite pairs at swollen nodes with sheathing leaf bases and interpetiolar stipules, along with compound spikes of flowers with a monosymmetric androecium of three stamens, each flower subtended by a bract. This represents the first time that fossil leaves, stems and inflorescences of Chloranthaceae have been found in organic connection. Alcainea may be sister to Sarcandra, Chloranthus or the clade consisting of both genera, like the mesofossil Canrightiopsis. Leaf Type A, with festooned craspedodromous venation and symmetrical teeth, may be related to Ascarina. These observations provide direct evidence for the distinctive vegetative and inflorescence morphology of Chloranthaceae in the Early Cretaceous. They are consistent with the level of diversification inferred from coeval chloranthaceous pollen and floral mesofossils, including lines nested in crown group Chloranthaceae but not in any of living genera, and exhibiting character combinations not retained in living Chloranthaceae. http://zoobank.org/urn:lsid:zoobank.org:pub:08B96BA0-3B27-48A1-9E8F-CB5811AE8C07

“Out-of-India” dispersal for Adina (tribe Naucleeae; family Rubiaceae): evidence from the early Eocene fossil record from India

This study reports the oldest fossil record of the genus Adina, A. vastanenesis n. sp., from the early Eocene of Vastan lignite mine (Cambay Shale Formation), Surat district, Gujarat. This fossil wood is characterized by diffuse porous wood, predominantly solitary tylosed vessels, simple perforations, scanty paratracheal to diffuse to sometimes diffuse in aggregate axial parenchyma, predominantly uniseriate to occasionally biseriate rays, and non septate fibres with bordered pits and shows its best resemblance with the modern species, Adina multifolia Haviland, belonging to the tribe Naucleeae (subfamily Cinchonoideae) of the family Rubiaceae. The present discovery becomes the first fossil record of the wood of Adina, which provides an insight about the Gondwanan origin either for the genus Adina or the tribe Naucleeae and its further dispersal to Southeast Asia.

A new occurrence of Craigia (Malvaceae) from the Miocene of Yunnan and its biogeographic significance

ABSTRACT The living fossil Craigia consists only two species Craigia yunnanensis W.W. Smith et W.E. Evans and Craigia kwangsiensis H.H. Hsue, endemic to East Asia. Craigia is a typical palaeoendemic genus, with an extensive fossil record in the Northern Hemisphere (North America, Europe and Asia); but there is a temporospatial gap between its fossil occurrences and the modern populations, so its migration history is enigmatic. The earliest fossil record is from Northeast Asia and extant species are relictual, occurring only in southwestern China, northeastern India and northern Vietnam. Here, we describe a new fossil species, Craigia lincangensis Wang et Xie sp. nov., based on fruits from Late Miocene of Yunnan, China. This new finding along with other fossil records in Asia clarifies the southward migration route in Asia. The Miocene occurrence in this investigation represents the youngest record of Craigia so far in Asia and sheds new light on the final migration into its relict habitat.

Can We Reliably Calibrate Deep Nodes in the Tetrapod Tree? Case Studies in Deep Tetrapod Divergences.

Recent efforts have led to the development of extremely sophisticated methods for incorporating tree-wide data and accommodating uncertainty when estimating the temporal patterns of phylogenetic trees, but assignment of prior constraints on node age remains the most important factor. This depends largely on understanding substantive disagreements between specialists (paleontologists, geologists, and comparative anatomists), which are often opaque to phylogeneticists and molecular biologists who rely on these data as downstream users. This often leads to misunderstandings of how the uncertainty associated with node age minima arises, leading to inappropriate treatments of that uncertainty by phylogeneticists. In order to promote dialogue on this subject, we here review factors (phylogeny, preservational megabiases, spatial and temporal patterns in the tetrapod fossil record) that complicate assignment of prior node age constraints for deep divergences in the tetrapod tree, focusing on the origin of crown-group Amniota, crown-group Amphibia, and crown-group Tetrapoda. We find that node priors for amphibians and tetrapods show high phylogenetic lability and different phylogenetic treatments identifying disparate taxa as the earliest representatives of these crown groups. This corresponds partially to the well-known problem of lissamphibian origins but increasingly reflects deeper instabilities in early tetrapod phylogeny. Conversely, differences in phylogenetic treatment do not affect our ability to recognize the earliest crown-group amniotes but do affect how diverse we understand the earliest amniote faunas to be. Preservational megabiases and spatiotemporal heterogeneity of the early tetrapod fossil record present unrecognized challenges in reliably estimating the ages of tetrapod nodes; the tetrapod record throughout the relevant interval is spatially restricted and disrupted by several major intervals of minimal sampling coincident with the emergence of all three crown groups. Going forward, researchers attempting to calibrate the ages for these nodes, and other similar deep nodes in the metazoan fossil record, should consciously consider major phylogenetic uncertainty, preservational megabias, and spatiotemporal heterogeneity, preferably examining the impact of working hypotheses from multiple research groups. We emphasize a need for major tetrapod collection effort outside of classic European and North American sections, particularly from the southern hemisphere, and suggest that such sampling may dramatically change our timelines of tetrapod evolution.

South American Crocodylomorphs (Archosauria; Crocodylomorpha): A review of the early fossil record in the continent and its relevance on understanding the origins of the clade

Crocodylomorpha is a clade that has its origins during the Late Triassic and attained a global distribution early in their radiation. In this context, although limited to few geological units, the South American record has been relevant in the understanding of the origins of the clade. Additionally analyzing the South American crocodylomorph record and comparing it with the one in the rest of Pangea is relevant as, in recent years, provincialism has been proposed for different faunal assemblages. In this contribution we review the crocodylomorph Triassic record in South America by analyzing three units that have yielded fossils of the clade: the Santa María Supersequence in Brazil; and, the Ischigualasto and Los Colorados formations in Argentina. Our review does not support previous assignments of the taxon Barberenasuchus from the Santa María Supersequence as a non-crocodyliform crocodylomorph, as it displays traits that are absent in all known crocodylomorphs and are present in other earlier branching archosaurs. On the other hand, the Argentinian stratigraphic units remain as the only ones that have crocodylomorphs in the subcontinent. Here we report for the first time the occurrence of “large-bodied” crocodylomorphs in the Ischigualasto Formation, represented by a new yet undescribed taxon. The Los Colorados Formation has a diverse crocodylomorph record being represented by a non-crocodyliform crocodylomorph (Psedhesperosuchus) and two crocodyliforms (Hemiprotosuchus and Coloradisuchus). Here we present a putative new non-crocodyliform crocodylomorph taxon from Los Colorados Formation. When compared with other crocodylomorph bearing formations around Pangea, the Ischigualasto Formation bears similarities with the crocodylomorphs assemblages of North America due to the presence of early branching crocodylomorphs (Trialestes) including “large-bodied” taxa. The Los Colorados Formation reveals a transitional composition corresponding to Norian and Early Jurassic assemblages of Pangea, as it shares the presence of basal crocodyliforms (i.e., protosuchids) typical of Early Jurassic units (e.g., Upper Elliot) and basal non-crocodyliform crocodylomorphs, widely present in Norian assemblages.

Mid-Cenozoic climate change, extinction, and faunal turnover in Madagascar, and their bearing on the evolution of lemurs

BackgroundWas there a mid-Cenozoic vertebrate extinction and recovery event in Madagascar and, if so, what are its implications for the evolution of lemurs? The near lack of an early and mid-Cenozoic fossil record on Madagascar has inhibited direct testing of any such hypotheses. We compare the terrestrial vertebrate fauna of Madagascar in the Holocene to that of early Cenozoic continental Africa to shed light on the probability of a major mid-Cenozoic lemur extinction event, followed by an “adaptive radiation” or recovery. We also use multiple analytic approaches to test competing models of lemur diversification and the null hypothesis that no unusual mid-Cenozoic extinction of lemurs occurred.ResultsComparisons of the terrestrial vertebrate faunas of the early Cenozoic on continental Africa and Holocene on Madagascar support the inference that Madagascar suffered a major mid-Cenozoic extinction event. Evolutionary modeling offers some corroboration, although the level of support varies by phylogeny and model used. Using the lemur phylogeny and divergence dates generated by Kistler and colleagues, RPANDA and TESS offer moderate support for the occurrence of unusual extinction at or near the Eocene-Oligocene (E-O) boundary (34 Ma). TreePar, operating under the condition of obligate mass extinction, found peak diversification at 31 Ma, and low probability of survival of prior lineages. Extinction at the E-O boundary received greater support than other candidate extinctions or the null hypothesis of no major extinction. Using the lemur phylogeny and divergence dates generated by Herrera & Dàvalos, evidence for large-scale extinction diminishes and its most likely timing shifts to before 40 Ma, which fails to conform to global expectations.ConclusionsWhile support for large-scale mid-Cenozoic lemur extinction on Madagascar based on phylogenetic modeling is inconclusive, the African fossil record does provide indirect support. Furthermore, a major extinction and recovery of lemuriforms during the Eocene-Oligocene transition (EOT) would coincide with other major vertebrate extinctions in North America, Europe, and Africa. It would suggest that Madagascar’s lemurs were impacted by the climate shift from “greenhouse” to “ice-house” conditions that occurred at that time. This could, in turn, help to explain some of the peculiar characteristics of the lemuriform clade.

The Chloroplast Land Plant Phylogeny: Analyses Employing Better-Fitting Tree- and Site-Heterogeneous Composition Models.

The colonization of land by descendants of charophyte green algae marked a turning point in Earth history that enabled the development of the diverse terrestrial ecosystems we see today. Early land plants diversified into three gametophyte-dominant lineages, namely the hornworts, liverworts, and mosses, collectively known as bryophytes, and a sporophyte-dominant lineage, the vascular plants, or tracheophytes. In recent decades, the prevailing view of evolutionary relationships among these four lineages has been that the tracheophytes were derived from a bryophyte ancestor. However, recent phylogenetic evidence has suggested that bryophytes are monophyletic, and thus that the first split among land plants gave rise to the lineages that today we recognize as the bryophytes and tracheophytes. We present a phylogenetic analysis of chloroplast protein-coding data that also supports the monophyly of bryophytes. This newly compiled data set consists of 83 chloroplast genes sampled across 30 taxa that include chlorophytes and charophytes, including four members of the Zygnematophyceae, and land plants, that were sampled following a balanced representation of the main bryophyte and tracheophyte lineages. Analyses of non-synonymous site nucleotide data and amino acid translation data result in congruent phylogenetic trees showing the monophyly of bryophytes, with the Zygnematophyceae as the charophyte group most closely related to land plants. Analyses showing that bryophytes and tracheophytes evolved separately from a common terrestrial ancestor have profound implications for the way we understand the evolution of plant life cycles on land and how we interpret the early land plant fossil record.

First evidence of an ankylosaur (Dinosauria, Ornithischia) from the Jurassic Qigu Formation (Junggar Basin, NW China) and the early fossil record of Ankylosauria

The first evidence of an ankylosaur from the Late Jurassic Qigu Formation of the southern Junggar Basin (Xinjiang, northwestern China) is described, based on an isolated caudal vertebra that was discovered together with fragmentary remains of other dinosaurs, including stegosaurs, sauropods, and theropods. The caudal vertebra is characterized by the following features: (i) elliptical morphology of the centrum, being wider than high; (ii) short antero-posterior length of the centrum; (iii) pronounced transversely extending ventral groove; (iv) massive transverse process, that is longer than the centrum diameter; (v) transverse process meeting the centrum high at the dorsal half and at a relatively flat angle; (vi) transverse process making a broad contact with the neural arch without forming a proximo-dorsal projection; and (vii) notochordal prominence present in the centre of the anterior articular surface. The study specimen represents only the second record of an ankylosaur from the Jurassic of Asia — aside from the slightly older Tianchisaurus from the early Upper Jurassic Toutunhe Formation, equally from the Junggar Basin. It helps to fill a gap in our knowledge of the early evolution of these armoured dinosaurs. Additionally, this discovery highlights the potential of the southern Junggar Basin to yield a rich vertebrate fauna and thus to provide an important insight into Late Jurassic ecosystems of Central Asia.