Biogeographical implications of a new mouse-sized fossil bandicoot (Marsupialia: Peramelemorphia) occupying a dasyurid-like ecological niche across Australia

Abstract: We describe Bulungu palara gen. et sp. nov., a new fossil peramelemorphian (bandicoot), based on a single well-preserved skull and additional dental specimens from Late Oligocene to Middle Miocene (Faunal Zones A–C) limestone deposits at the Riversleigh World Heritage Property, Queensland, and two dental specimens from the Early–Middle Miocene Kutjamarpu Local Fauna, South Australia. This is the first fossil peramelemorphian species to be reported from more than a single fossil fauna, with its inferred distribution extending from north-western Queensland (modern latitude ∼19°S) to north-eastern South Australia (modern latitude ∼28°S). The presence of Bulungu palara in Riversleigh Faunal Zones A, B and C and in the Kutjamarpu Local Fauna supports the current interpretation that these faunas span similar ages, namely Late Oligocene–Middle Miocene. Phylogenetic analyses of an expanded 74 morphological character dataset using maximum parsimony and Bayesian approaches, both with and without a molecular scaffold, consistently place Bulungu and the Oligo-Miocene forms Galadi and Yarala outside crown-group Peramelemorphia. These analyses also fail to support a close relationship between the Pliocene Ischnodon australis (previously considered the oldest known representative of the extant peramelemorphian family Thylacomyidae) and the modern thylacomyid genus Macrotis. With an estimated body mass of ∼130 g, Bulungu palara is smaller than any known Recent bandicoot from Australia, although some modern New Guinean species are similar in size. The small size and craniodental morphology of B. palara suggest that it was predominantly or exclusively insectivorous, perhaps ecologically similar to small New Guinean dasyurids such as Murexechinus melanurus. Together with the small-bodied (< 100 g), insectivorous Yarala burchfieldi and large-bodied (∼900 g), faunivorous Galadi speciosus, Bulungu palara demonstrates that Oligo-Miocene Australian peramelemorphians filled ecological niches that today are mostly occupied by dasyurids, and that a major faunal turnover event occurred at some point after the Middle Miocene. http://zoobank.org/urn:lsid:zoobank.org:pub:18955DCC-DB8C-4216-AF38-921E1E5C1F79

peramelemorphia
ecological niche
late oligocene


Body mass estimation in xenarthra: A predictive equation suitable for all quadrupedal terrestrial placentals?

Abstract: The Magnorder Xenarthra includes strange extinct groups, like glyptodonts, similar to large armadillos, and ground sloths, terrestrial relatives of the extant tree sloths. They have created considerable paleobiological interest in the last decades; however, the ecology of most of these species is still controversial or unknown. The body mass estimation of extinct species has great importance for paleobiological reconstructions. The commonest way to estimate body mass from fossils is through linear regression. However, if the studied species does not have similar extant relatives, the allometric pattern described by the regression could differ from those shown by the extinct group. That is the case for glyptodonts and ground sloths. Thus, stepwise multiple regression were developed including extant xenarthrans (their taxonomic relatives) and ungulates (their size and ecological relatives). Cases were weighted to maximize the taxonomic evenness. Twenty‐eight equations were obtained. The distribution of the percent of prediction error (%PE) was analyzed between taxonomic groups (Perissodactyla, Artiodactyla, and Xenarthra) and size groups (0–20 kg, 20–300 kg, and more than 300 kg). To assess the predictive power of the functions, equations were applied to species not included in the regression development [test set cross validation, (TSCV)]. Only five equations had a homogeneous %PE between the aforementioned groups. These were applied to five extinct species. A mean body mass of 80 kg was estimated for Propalaehoplophorus australis (Cingulata: Glyptodontidae), 594 kg for Scelidotherium leptocephalum (Phyllophaga: Mylodontidae), and 3,550.7 kg for Lestodon armatus (Phyllophaga: Mylodontidae). The high scatter of the body mass estimations obtained for Catonyx tarijensis (Phyllophaga: Mylodontidae) and Thalassocnus natans (Phyllophaga: Megatheriidae), probably due to different specializations, prevented us from predicting its body mass. Surprisingly, although obtained from ungulates and xenarthrans, these five selected equations were also able to predict the body mass of species from groups as different as rodents, carnivores, hyracoideans, or tubulidentates. This result suggests the presence of a complex common allometric pattern for all quadrupedal placentals. J. Morphol., 2008. © 2008 Wiley‐Liss, Inc.

xenarthra
equation
ground sloth
body mass estimation


New bivalves from a Middle Devonian methane seep in Morocco: the oldest record of repetitive shell morphologies among some seep bivalve molluscs

Abstract: A fauna of bivalve molluscs is described from methane seep carbonates of the Middle Devonian (c. 390 Ma) Hollard Mound in the eastern Anti-Atlas, Morocco. We describe a new modiomorphid genus Ataviaconcha gen. nov. with the type species Ataviaconcha wendti sp. nov. This is a very large, semi-infaunal species occurring in large colonies similar to those formed by Recent chemosymbiotic cold-seep and hydrothermal vent bivalves. It is the second modiomorphid bivalve known from Palaeozoic chemosynthesis-based ecosystems, after the roughly coeval Sibaya ivanovi Little, Maslennikov, Morris & Gubanov, 1999, from the Sibay hydrothermal vent deposit in the Ural Mountains, Russia. The second and much less numerous bivalve species described in this paper is the solemyid Dystactella? eisenmanni sp. nov., belonging to a genus known also from Ordovician to Devonian marine environments distinct from cold seeps and hydrothermal vents. As with other fossil and Recent solemyids, it was an infaunal burrower, most likely living in symbiosis with chemoautotrophic bacteria. These new findings show that bivalves are ancient in chemosynthesis-based ecosystems, thriving there for at least 390 Myr, and that the bivalve-dominated faunas predated the first occurrence of dimerelloid brachiopods at seeps. The early evolutionary adaptation of some bivalves to chemosynthesis-based ecosystems is probably related to a symbiosis-based metabolism allowing efficient exploitation of chemosynthetic food resources. Ataviaconcha wendti sp. nov. represents a morphology which recurred several times throughout the following 390 Myr in different bivalve groups that flourished at hydrocarbon seeps. This strongly suggests environmental control on the evolution of adaptations in seep biotas. http://zoobank.org/urn:lsid:zoobank.org:pub:A83D5CB1-67D2-4D05-8EBC-BFCA6E6845D8


A Synthesis of the Long-Term Paleoclimatic Evolution of the Arctic

Abstract: Since the Arctic Ocean began forming in the Early Cretaceous 112–140 million years ago, the Arctic region has undergone profound oceanographic and paleoclimatic changes. It has evolved from a warm epicontinental sea to its modern state as a cold isolated ocean with extensive perennial sea ice cover. Our understanding of the long-term paleoclimate evolution of the Arctic remains fragmentary but has advanced dramatically in the past decade through analysis of new marine and terrestrial records, supplemented by important insights from paleoclimate models. Improved understanding of how these observations fit into the long-term evolution of the global climate system requires additional scientific drilling in the Arctic to provide detailed and continuous paleoclimate records, and to resolve the timing and impact of key tectonic and physiographic changes to the ocean basin and surrounding landmasses. Here, we outline the long-term paleoclimatic evolution of the Arctic, with a focus on integrating both terrestrial and marine records.

long-term paleoclimatic evolution
arctic
arctic ocean


On impact and volcanism across the Cretaceous-Paleogene boundary

Abstract: An impact with a dash of volcanism Around the time of the end-Cretaceous mass extinction that wiped out dinosaurs, there was both a bolide impact and a large amount of volcanism. Hull et al. ran several temperature simulations based on different volcanic outgassing scenarios and compared them with temperature records across the extinction event. The best model fits to the data required most outgassing to occur before the impact. When combined with other lines of evidence, these models support an impact-driven extinction. However, volcanic gases may have played a role in shaping the rise of different species after the extinction event. Science, this issue p. 266 The primary cause of the end-Cretaceous mass extinction was an impact, with volcanism playing a role in the aftermath. The cause of the end-Cretaceous mass extinction is vigorously debated, owing to the occurrence of a very large bolide impact and flood basalt volcanism near the boundary. Disentangling their relative importance is complicated by uncertainty regarding kill mechanisms and the relative timing of volcanogenic outgassing, impact, and extinction. We used carbon cycle modeling and paleotemperature records to constrain the timing of volcanogenic outgassing. We found support for major outgassing beginning and ending distinctly before the impact, with only the impact coinciding with mass extinction and biologically amplified carbon cycle change. Our models show that these extinction-related carbon cycle changes would have allowed the ocean to absorb massive amounts of carbon dioxide, thus limiting the global warming otherwise expected from postextinction volcanism.

volcanism
end-cretaceous mass extinction
bolide impact
cause
warming


New insights into the ultrastructure, permeability, and integrity of conodont apatite determined by transmission electron microscopy

Abstract:
New crystalline structures have been observed in argon ion-milled conodont elements from a diverse suite of Ordovician taxa (‘Cordylodus robustus’, Drepanoistodus suberectus, Panderodus gracilis, Plectodina? sp., Aphelognathus sp., Periodon aculeatus), using transmission electron microscopy (TEM). Electron diffraction patterns of albid tissue reveal that the component crystals are extraordinarily large, in the order of hundred(s) of microns. These large albid crystals show typical cancellate porosity, although a distinctly lamellar structure has also been observed within a large albid crystal positioned between hyaline lamellar and cancellate albid tissues. There is a distinct absence of ‘interlamellar space’ within all hyaline tissues examined, which are characterized by a polycrystalline matrix of micron-scale elongate crystals that are both strongly aligned and tightly bound within a broader lamellar structure. Optical opacity, caused by light scattering within large (≥ 0.5 µm) pores, is also a feature of both albid and polycrystalline lamellar crown tissues. Accordingly, conodont hard tissues are differentiated by crystal size and shape, as well as inter- and intracrystalline porosity.

These new observations highlight the structural complexities of conodont histologies and the need for more comprehensive investigations particularly of transitional crown tissues, which are not well defined by terms typically used in the literature. Their histological structures are interpreted to be a product of in vivo crystallization and thus provide new insights into the relative porosity, permeability, and inherent integrity of the tissues as well as their growth relationships. Accordingly, these data not only have implications for earlier histological and palaeobiological interpretations of conodont hard tissues but are also fundamental in determining their chemical integrity, which is crucial for characterizing palaeoseawater composition and palaeoenvironmental change. The potential for conodont apatite to retain primary chemical information depends on crystal size and permeability, so the large albid crystal domains are consistent with parallel geochemical studies that suggest that cancellate albid crown is more resistant to diagenetic modification.

permeability
conodont apatite
transmission electron microscopy
crystal
matrix


Systematics and Evolution of the Miocene Three-Horned Palaeomerycid Ruminants (Mammalia, Cetartiodactyla)

Abstract: Palaeomerycids were strange three-horned Eurasian Miocene ruminants known through fossils from Spain to China. We here study their systematics, offering the first cladistic phylogeny of the best-known species of the group, and also reassess their phylogenetic position among ruminants, which is currently disputed. The beautifully preserved remains of a new palaeomerycid from middle Miocene deposits of Spain, Xenokeryx amidalae gen. et sp. nov., helps us to better understand palaeomerycid anatomy, especially that of the nuchal region in the skull, significantly improving our current knowledge on these enigmatic ruminants. Our results show two main lineages of palaeomerycids, one containing the genus Ampelomeryx diagnosed by a characteristic type of cranium / cranial appendages and some dental derived traits, and another one that clusters those forms more closely related to Triceromeryx than to Ampelomeryx, characterized by a more derived dentition and a set of apomorphic cranial features. Xenokeryx branches as a basal offshoot of this clade. Also, we find that Eurasian palaeomerycids are not closely related to North American dromomerycids, thus rejecting the currently more accepted view of palaeomerycids as the Eurasian part of the dromomerycid lineage. Instead of this, palaeomerycids are nested with the African Miocene pecoran Propalaeoryx and with giraffoids. On the other hand, dromomerycids are closely related to cervids. We define a clade Giraffomorpha that includes palaeomerycids and giraffids, and propose an emended diagnosis of the Palaeomerycidae based on cranial and postcranial characters, including several features of the cranium not described so far. We also define the Palaeomerycidae as the least inclusive clade of pecorans containing Triceromeryx and Ampelomeryx. Finally, we reassess the taxonomy of several palaeomerycid taxa.

ruminant
giraffomorpha
palaeomerycidae
large clade


Early Eocene Thermal Maximum 3: Biotic Response at Walvis Ridge (SE Atlantic Ocean)

Abstract: We combine stable isotope, calcareous nannoplankton, and benthic foraminiferal records for Ocean Drilling Program Sites 1262 (paleodepth ~3,500 m) and 1263 (paleodepth ~1,500 m) on Walvis Ridge (SE Atlantic), to document the marine biotic response to Eocene Thermal Maximum 3, in the early part of the Early Eocene Climate Optimum, ~3.1 Myr after the Paleocene/Eocene Thermal Maximum. Bottom water warming may have decreased the vertical thermal gradient at both sites, but more at Site 1263 than at Site 1262. Floral and faunal changes were more muted at Site 1262 than at shallower Site 1263, indicating that carbonate dissolution was not the most important cause of biotic effects. Assemblage changes were more pronounced in benthos than in plankton. Calcareous nannofossils underwent minor ecological changes, possibly related to the presence of warmer waters, especially at Site 1263, and dissolution‐resistant taxa increased in abundance. Benthic foraminiferal diversity decreased at both sites, but benthic foraminiferal accumulation rates declined dramatically at Site 1263, remaining stable at Site 1262. Ocean circulation may have changed during ETM3, resulting in the presence of a warmer (intermediate) water mass at Site 1263. More pronounced warming may have caused enhanced remineralization of organic matter, so less food reached the benthos. The biotic response to the X‐event was less pronounced than that to earlier and more severe hyperthermal events, the Paleocene/Eocene Thermal Maximum and Eocene Thermal Maximum 2. The extent of the biotic response reflects the severity of the environmental disturbance but varies by location (e.g., paleodepth on Walvis Ridge).

eocene thermal maximum
biotic response
walvis ridge
foraminiferal record


Increased precipitation and weathering across the Paleocene‐Eocene Thermal Maximum in central China

Abstract: Global warming during the Paleocene‐Eocene Thermal Maximum (PETM) ∼55.5 million years ago (Ma) was associated with a massive release of carbon to the ocean‐atmosphere system, as evidenced by a prominent negative carbon isotope excursion (CIE) and widespread dissolution of marine carbonates. The paleohydrologic response to the PETM warming has been studied worldwide; however, relevant records of environmental perturbation in Asia are lacking so far. Here we extend the record of this event in central China, a subtropical paleosetting, through geochemical and mineralogical analyses of lacustrine sediments. Geochemical indicators of authigenic carbonates—including molar Mg/Ca and Sr/Ca ratios—suggest an overall increased precipitation across the PETM, compatible with the disappearance of authigenic dolomite and the appearance of kaolinite in the strata. The relatively humid conditions persisted long after the carbon‐cycle perturbation had stopped, implying that the transient hyper‐greenhouse warming might have forced the regional climate system into a new climate state that was not easily reversed. Additionally, a gradual increase in chemical index of alteration (CIA) and the appearance of kaolinite are associated with the PETM, indicating an intensified silicate weathering and pedogenesis in the watershed in response to warmer and more humid climate. Our results corroborate the theory that an accelerated continental chemical weathering served as a negative feedback to sequester carbon and lower the atmospheric greenhouse‐gas levels during the PETM.

precipitation
paleocene‐eocene thermal maximum
central china
kaolinite


Extraterrestrial Cause for the Cretaceous-Tertiary Extinction

Abstract: Platinum metals are depleted in the earth's crust relative to their cosmic abundance; concentrations of these elements in deep-sea sediments may thus indicate influxes of extraterrestrial material. Deep-sea limestones exposed in Italy, Denmark, and New Zealand show iridium increases of about 30, 160, and 20 times, respectively, above the background level at precisely the time of the Cretaceous-Tertiary extinctions, 65 million years ago. Reasons are given to indicate that this iridium is of extraterrestrial origin, but did not come from a nearby supernova. A hypothesis is suggested which accounts for the extinctions and the iridium observations. Impact of a large earth-crossing asteroid would inject about 60 times the object's mass into the atmosphere as pulverized rock; a fraction of this dust would stay in the stratosphere for several years and be distributed worldwide. The resulting darkness would suppress photosynthesis, and the expected biological consequences match quite closely the extinctions observed in the paleontological record. One prediction of this hypothesis has been verified: the chemical composition of the boundary clay, which is thought to come from the stratospheric dust, is markedly different from that of clay mixed with the Cretaceous and Tertiary limestones, which are chemically similar to each other. Four different independent estimates of the diameter of the asteroid give values that lie in the range 10 � 4 kilometers.

cause
cretaceous-tertiary extinction
asteroid
mass extinction
bolide impact


A quantitative evaluation of evolutionary patterns in opercle bone shape in Saurichthys (Actinopterygii: Saurichthyidae)

Abstract: Despite an impressive radiation of more than 30 species in the wake of the end‐Permian mass extinction, the taxonomic study of Saurichthys has suffered from a lack of universally diagnostic features and a lack of tested quantitative schemes that can be applied to analyse interspecific morphological differences. In this study, we provide an initial quantitative framework for morphological evolution in Saurichthys by focusing on a single bone, the opercle and exploring patterns of interspecific variability in shape using outline‐based geometric morphometrics and linear measurements. For the six species examined, comprising 155 specimens and representatives from the Early, Middle and Late Triassic, our results indicate that interspecific shape differences largely reflect an anterior–posterior dimension decrease (= craniocaudal direction) as the dorso‐ventral dimension remains similar. In contrast, intraspecific variability in shape is subtle and spread across the outline of the bone, such that counter‐acting dimension differences (increase/decrease) were found to occur along a single margin at oblique axes in several species. Our quantitative scheme, which is widely applicable to other groups, provides a useful description of the broad modes of opercle shape change that may help as a starting framework from which to develop character states for opercle morphology in future study.

evolutionary pattern
saurichthys
morphometric
specie flock


Earliest ontogeny of Early Palaeozoic Craniiformea : compelling evidence for lecithotrophy

Abstract:
Popov, L.E., Bassett, M.G. & Holmer, L.E. 2012: Earliest ontogeny of Early Palaeozoic Craniiformea: compelling evidence for lecithotrophy. Lethaia, Vol. 45, pp. 566–573.

The early ontogeny of Palaeozoic Craniiformea (Brachiopoda) remains controversial, with conflicting reports of evidence indicating lecithotrophic versus planktotrophic larval stages. Further compelling evidence for lecithotrophy in Palaeozoic craniiforms is described here. Newly obtained, well-preserved Silurian specimens of craniiforms, including Craniops (Craniopsida), and Lepidocrania? and Orthisocrania (Craniida) from Gotland and the St. Petersburg region, form the basis for this study. The new material demonstrates that the characters of shell structure and shell formation provide evidence of early differentiation of an adult dorsal mantle, and the presence of a distinctive primary layer with a characteristic lath-like pattern indicates that these craniiforms underwent a lecithotrophic larval stage, more or less identical to that of living. □Novocrania. Brachiopoda, Craniiformea, ontogeny, phylogeny, Early Palaeozoic.

early palaeozoic craniiformea
lecithotrophy
early ontogeny


Pneumaticity and soft-tissue reconstructions in the neck of diplodocid and dicraeosaurid sauropods

Abstract: The axial soft-tissue system in the neck of Dicraeosauridae and Diplodocidae, including pneumatic diverticula, ligaments, and muscles, is reconstructed on the basis of phylogenetic and functional morphological comparisons with extant crocodylians and birds and compared with other soft-tissue reconstructions for sauropods. Bifurcation of the neural spines separated the paired supraspinal ligament into two sheets. A paired interspinal septum was attached to the cranial and caudal margins of the neural spines. The dorsal and the lateral portions of the cervical musculature must have been strongly segmented, whereas the laterocostal portion was divided with one myoseptum per vertebral segment. The hypaxial cervical muscle was most probably small and only poorly segmented. In Diplodocidae and Dicraeosauridae, the distribution of external pneumatic structures is similar, whereas only Diplodocidae possess intraosseous pneumatic structures. Supravertebral pneumatic diverticula are reconstructed for both groups, which, together with dorsal ligaments filled the gap between the metapophyses of bifurcate neural spines. Comparisons between the vertebrae of juvenile and adult diplodocids strongly indicate that pneumatisation proceeded from the supramedullary diverticula into the neural arch and the neural spine. The regular branching pattern of the pneumatic cavities as well as the vertical I-beam construction of the vertebral corpora is interpreted as a consequence of the biomechanical constraints of the vertebral corpora in diplodocids. These reconstructions form the ground for functional morphological considerations in Diplodocidae and Dicraeosauridae while addressing the possible mechanical consequences of pneumatic structures for the integrity of the support system of the neck.

sauropod
pneumatic diverticula
vertebrae
pneumaticity


Revisiting the molluscan fauna from the Cambrian (Series 2, stages 3–4) Xinji Formation of North China

Abstract: A diverse group of molluscs from the Cambrian Series 2, Stages 3–4 Xinji Formation of the North China Block (NCB) is described, based on more than 4500 specimens from three well‐studied sections in Shaanxi and Henan provinces, along the southern and southwestern margin of the NCB. Twenty molluscan species are identified, including one bivalve, three stem group gastropods, and 16 additional helcionelloids. Among these, six helcionelloid species are reported from the NCB for the first time, and one new species, Parailsanella luonanensis sp. nov. is proposed. This diverse molluscan fauna shares a large number of species with contemporaneous faunas of South Australia (15), Antarctica (7), Laurentia (6), Siberia (3) and South China (1). Faunal similarities are even greater on a generic level. The striking similarities of the molluscan faunas of North China, South Australia and Antarctica strongly support the hypothesis that the NCB was situated close to Eastern Gondwana, most likely close to South Australia in the Cambrian Epoch 2. In addition, well‐preserved shell attachment muscle scars were observed in the helcionelloid Figurina figurina, with two pairs of symmetrical, continuous, band‐like muscle scars, which are obviously different from the musculature of both gastropods and monoplacophorans. Because of this unique musculature, these characteristic Cambrian cap‐like molluscs are assigned to the Helcionelloida rather than to the Gastropoda or Monoplacophora.


Atolchelys lepida, a new side-necked turtle from the Early Cretaceous of Brazil and the age of crown Pleurodira

Abstract: We report a new pleurodiran turtle from the Barremian Morro do Chaves Formation, Sergipe-Alagoas Basin, Brazil. We tested the phylogenetic position of Atolchelys lepida gen. et sp. nov. by including it in a comprehensive cladistic analysis of pleurodires. The new species is a basal member of Bothremydidae and simultaneously the oldest unambiguous crown Pleurodira. The biogeographic and chronostratigraphic significance of the finding has implications for the calibration of molecular clocks studies by pushing back the minimum age of crown Pleurodira by more than 12 Ma (ca 125 Ma). The reanalysis of Pelomedusoides relationships provides evidence that the early evolution and relationships among the main lineages of side-necked turtles can be explained, at least partially, by a sequence of vicariance events.

turtle
early cretaceous
crown pleurodira
phylogenetic position


Proteomic method to extract, concentrate, digest and enrich peptides from fossils with coloured (humic) substances for mass spectrometry analyses

Abstract: Humic substances are breakdown products of decaying organic matter that co-extract with proteins from fossils. These substances are difficult to separate from proteins in solution and interfere with analyses of fossil proteomes. We introduce a method combining multiple recent advances in extraction protocols to both concentrate proteins from fossil specimens with high humic content and remove humics, producing clean samples easily analysed by mass spectrometry (MS). This method includes: (i) a non-demineralizing extraction buffer that eliminates protein loss during the demineralization step in routine methods; (ii) filter-aided sample preparation (FASP) of peptides, which concentrates and digests extracts in one filter, allowing the separation of large humics after digestion; (iii) centrifugal stage tipping, which further clarifies and concentrates samples in a uniform process performed simultaneously on multiple samples. We apply this method to a moa fossil (approx. 800–1000 years) dark with humic content, generating colourless samples and enabling the detection of more proteins with greater sequence coverage than previous MS analyses on this same specimen. This workflow allows analyses of low-abundance proteins in fossils containing humics and thus may widen the range of extinct organisms and regions of their proteomes we can explore with MS.

humic
substance
mass spectrometry
protein


Phylogeny and tempo of diversification in the superradiation of spiny-rayed fishes

Abstract: Spiny-rayed fishes, or acanthomorphs, comprise nearly one-third of all living vertebrates. Despite their dominant role in aquatic ecosystems, the evolutionary history and tempo of acanthomorph diversification is poorly understood. We investigate the pattern of lineage diversification in acanthomorphs by using a well-resolved time-calibrated phylogeny inferred from a nuclear gene supermatrix that includes 520 acanthomorph species and 37 fossil age constraints. This phylogeny provides resolution for what has been classically referred to as the “bush at the top” of the teleost tree, and indicates acanthomorphs originated in the Early Cretaceous. Paleontological evidence suggests acanthomorphs exhibit a pulse of morphological diversification following the end Cretaceous mass extinction; however, the role of this event on the accumulation of living acanthomorph diversity remains unclear. Lineage diversification rates through time exhibit no shifts associated with the end Cretaceous mass extinction, but there is a global decrease in lineage diversification rates 50 Ma that occurs during a period when morphological disparity among fossil acanthomorphs increases sharply. Analysis of clade-specific shifts in diversification rates reveal that the hyperdiversity of living acanthomorphs is highlighted by several rapidly radiating lineages including tunas, gobies, blennies, snailfishes, and Afro-American cichlids. These lineages with high diversification rates are not associated with a single habitat type, such as coral reefs, indicating there is no single explanation for the success of acanthomorphs, as exceptional bouts of diversification have occurred across a wide array of marine and freshwater habitats.

spiny-rayed fish
living acanthomorph
reef
phylogeny


Microanatomy of the radius and lifestyle in amniotes (Vertebrata, Tetrapoda)

Abstract: Radial cross‐sections of 49 species of extant and two species of extinct amniotes of known lifestyle have been studied in order to assess the relationship between lifestyle (aquatic, amphibious or terrestrial) and bone microanatomy. Most compactness profile and body size parameters exhibit a phylogenetic signal; therefore, classical statistical tests should not be used. Permutational multiple linear regressions show an ecological signal in most compactness profile parameters and in the cross‐section maximal diameter. A linear discriminant analysis is performed with these parameters to distinguish the various lifestyles. The discriminant function based on taxa of known lifestyle is used to infer the lifestyle of three extinct amniotes: the early nothosaur Pachypleurosaurus (amphibious), the therapsid Lystrosaurus (amphibious) and the synapsid Ophiacodon (aquatic). These predictions are congruent with classical palaeoecological interpretations. This model may be very useful when attempting to infer the ancestral lifestyle of amniotes and other early limbed vertebrates.

lifestyle
amniote
ecological signal
microanatomy


Soft Anatomy of the Early Cambrian Arthropod Isoxys curvirostratus from the Chengjiang Biota of South China with a Discussion on the Origination of Great Appendages

Abstract: An updated reconstruction of the body plan, functional morphology and lifestyle of the arthropod Isoxys curvirostratus is proposed, based on new fossil specimens with preserved soft anatomy found in several localities of the Lower Cambrian Chengjiang Lagerstätte. The animal was 2–4 cm long and mostly encased in a single carapace which is folded dorsally without an articulated hinge. The attachment of the body to the exoskeleton was probably cephalic and apparently lacked any well-developed adductor muscle system. Large stalked eyes with the eye sphere consisting of two layers (as corneal and rhabdomeric structures) protrude beyond the anterior margin of the carapace. This feature, together with a pair of frontal appendages with five podomeres that each bear a stout spiny outgrowth, suggests it was raptorial. The following 14 pairs of limbs are biramous and uniform in shape. The slim endopod is composed of more than 7 podomeres without terminal claw and the paddle shaped exopod is fringed with at least 17 imbricated gill lamellae along its posterior margin. The design of exopod in association with the inner vascular (respiratory) surface of the carapace indicates I. curvirostratus was an active swimmer. Morphological comparisons demonstrate that species of Isoxys were diverse in feeding habits and occupied a very broad morphospace, i.e., carapace bivalved or a single shield, the pre-oral limbs antenniform or modified into great appendages, the succeeding endopods slim or stout. This casts doubt on the current taxonomy that assigns all species to a single genus, and on any presumed lifestyle of Isoxys extrapolated to the generic level. Finally, since I. curvirostratus and I. acutangulus carry a pair of great appendages, Isoxys has recently been placed into the great appendage arthropods. Such placement might be inadequate because the homology of the great appendages can not be established.

arthropod isoxys curvirostratus
chengjiang biota
appendage
endopod


Exceptionally preserved ostracodes from a Middle Miocene palaeolake, California, USA

Abstract: Abstract: Exceptionally well-preserved specimens of a new cypridid ostracode (Crustacea), Raepula ira sp. nov., are described from palaeolake sediments of the Middle Miocene Barstow Formation of the Mud Hills, southern California. This is only the second occurrence of exceptionally preserved ostracodes from the Miocene. Based on ages obtained from associated volcanic tuffs the palaeolake sediments were deposited between 16.3 and 15.8 Ma. The ostracodes form one element of a diverse lake community dominated by fairy shrimps, copepods, diatoms, larvae of diving beetles, flies and mosquitoes, and body fossils and ephippia of branchiopods and anomopods. The ostracodes are preserved three dimensionally with their soft anatomy replicated in microcrystalline silica. Submicron-scale details such as sensory setae are preserved, surpassing the resolution of most other ostracode-bearing lagerstätten and allowing their biology to be compared with extant taxa. Supplementary material: Red–blue anaglyphs of the exceptionally preserved ostracodes are available at http://www.geolsoc.org.uk/SUP18407.


The monophyly of Euparkeriidae (Reptilia: Archosauriformes) and the origins of Archosauria: a revision of Dorosuchus neoetus from the Mid‐Triassic of Russia

Abstract: Euparkeria capensis is resolved as the sister taxon to Archosauria in many cladistic phylogenies and provides a key outgroup which may approximate the ancestral archosaur morphology. Several other taxa have been referred to the family Euparkeriidae, but the monophyly of this taxon remains doubtful and largely untested. To test this monophyly, the archosauriform and putative euparkeriid Dorosuchus neoetus from the Mid‐Triassic of Russia is re‐examined in the light of recent work on the evolution of stem archosaurs. Dorosuchus neoetus is found to possess a number of morphological features that place it close to Archosauria, including a sigmoidal femur with a clear attachment region for the m. caudifemoralis musculature, but no unambiguous archosaurian apomorphies. Dorosuchus neoetus is included for the first time in a numerical cladistic analysis and is recovered as the sole sister taxon to Archosauria + Phytosauria. A monophyletic Euparkeriidae including D. neoetus and E. capensis is slightly less parsimonious. In addition, a mandible and pterygoid that were previously referred to D. neoetus subsequent to the original description of the species are also included separately within the phylogenetic analysis and are recovered within Archosauria, possibly raising questions as to their correct taxonomic referral. However, this phylogenetic placement is based primarily on the absence of palatal teeth, but the presence or absence of palatal teeth exhibits considerable homoplasy within Archosauriformes. Based on other aspects of their morphology, we do not reject the referral of these elements to D. neoetus.


Telltale eyes: the lateral visual systems of Rhenish Lower Devonian eurypterids (Arthropoda, Chelicerata) and their palaeobiological implications

Abstract: The compound eyes of three taxa of Rhenish Lower Devonian eurypterids are examined and compared with those known from other eurypterids and the extant horseshoe crab Limulus polyphemus. The lateral eyes of the small species Rhenopterus diensti, a phylogenetically basal representative of the stylonurine clade, are characterized by a comparatively low number of lenses and high interommatidial angle Δφ (2.8°). The comparatively limited visual capacities of R. diensti are more similar to L. polyphemus than to its closer relatives of the eurypterine clade and perhaps this reflects a progression of lateral eye structure in the evolution of eurypterids as a whole. The number of eye facets in Adelophthalmus sievertsi is higher than that in the supposed ambush predator Acutiramus cummingsi, but lower than that in other ‘swimming’ eurypterids (Eurypterina). Due to poor preservation, no other eye parameters could be analysed in this species, but further morphological attributes and geographical distribution designate the mid‐sized A. sievertsi as an able swimmer. A low interommatidial angle Δφ of less than 1° confirms that the visual capacities of Jaekelopterus rhenaniae are in line with an interpretation of this giant species as an active high‐level predator. The inferred lifestyles of adult individuals of these three, co‐occurring Rhenish eurypterids indicate niche differentiation avoiding to some degree the competition for food in their marginal marine to delta plain transitional habitats.


A ‘new’ palaeolithic dog from central Europe

Abstract: Kesslerloch Cave in Switzerland is one of the major Magdalenian sites in Central Europe. During a recent reanalysis of the faunal remains, we identified a cranial fragment and teeth of the domestic dog. The large maxillar fragment was directly dated to 12.225±45 bp (KIA-33350) or c. 14.100-14.600 BP. The finds are metrically well below the natural variability of wolves from both Palaeolithic and recent times and even show slight morphological differences to the wild wolves from the site. We argue that the maxilla fragment must now be considered the earliest indisputable directly dated evidence of a domestic dog. Copyright © 2010 John Wiley & Sons, Ltd.


Flightlessness and Long Bone Allometry in Palaeognathiformes and Sphenisciformes

Abstract: Palaeognathiformes and Sphenisciformes are the only two major taxa that have lost the capacity for flying. Nevertheless, the consequences of this flightlessness are completely different. While Palaeognathiformes are all running birds, Sphenisciformes are adapted to swimming. To study the morphology of leg and wing bones, length, sagittal and transverse diameters and second moment of area of humerus, ulna, radius, femur, tibiotarsus and tarsometatarsus were measured. Thirty-three specimens from fourteen species of Palaeognathiformes and eleven specimens from seven species of Sphenisciformes were studied. Several non-flying species from other avian orders were also considered. Regressions of all these parameters were calculated with body mass as the independent variable. For each bone, the ratio sagittal diameter/transverse diameter was also calculated. Most of the correlations are significantly different from the isometric condition. From a mechanical point of view, the most interesting result is that the second moment of area of the leg long bones always scales with strong positive allometry, whereas in the case of the wing long bones, the scaling shows high negative allometry. Biometrically, Sphenisciformes display a constant wing long bone morphology, with transverse diameters much larger than sagittal. In contrast, Palaeognathiformes present a highly variable morphology of the wing bones, affecting length and diameters.

allometry
palaeognathiformes
sphenisciforme
body mass
flightlessness


Redescription of the skull of Hezhengia bohlini (Artiodactyla, Mammalia) and a reassessment of the systematics of the Chinese late Miocene ‘ovibovines’

Abstract: Hezhengia is the most recently named ‘ovibovine’ genus, established by Qiu et al. (2000) based on a brief description of several skulls from Hezheng County, Linxia Prefecture, without attempting to provide a phylogenetic analysis with the other Chinese ‘ovibovines’, including Tsaidamotherium, Shaanxispira, Lantiantragus, Urmiatherium and Plesiaddax. Since then more than 100 well-preserved skulls have been discovered from the Linxia Basin. Most of the late Miocene ‘ovibovines’ have a highly specialized horn apparatus, and their inter-relationships and relationships to the extant Ovibos remain enigmatic. In this study, we provide detailed descriptions of H. bohlini skulls and mandibles, compared with the other Chinese late Miocene ‘ovibovines’. Two previously described upper jaws (?Plesiaddax minor) from Fugu County in north-western China are referred to a second species of Hezhengia, H. minor (Bohlin, 1935a). We perform a cladistic analysis using 110 morphological characters of skull, teeth and horn core, including all the Chinese late Miocene ‘ovibovine’ genera with relatively complete skulls, the middle Miocene fossil bovid Turcocerus, and 13 extant bovids. An analysis focused on the target fossil taxa is also performed with minimally necessary extant bovids. The phylogenetic analyses indicate that the Chinese late Miocene ‘ovibovines’ are paraphyletic offshoots of the same clade including Turcocerus and the extant capines, and none of them is closely related to Ovibos. We tentatively divided them into three groups, referring Hezhengia, Plesiaddax and Urmiatherium to the tribe Urmiatheriini, finding Shaanxispira and Lantiantragus as closely related, and Tsaidamotherium probably a distant clade.

skull
chinese late miocene
ovibovine
linxia basin


Time-dependent climate sensitivity and the legacy of anthropogenic greenhouse gas emissions

Abstract: Climate sensitivity measures the response of Earth’s surface temperature to changes in forcing. The response depends on various climate processes that feed back on the initial forcing on different timescales. Understanding climate sensitivity is fundamental to reconstructing Earth’s climatic history as well as predicting future climate change. On timescales shorter than centuries, only fast climate feedbacks including water vapor, lapse rate, clouds, and snow/sea ice albedo are usually considered. However, on timescales longer than millennia, the generally higher Earth system sensitivity becomes relevant, including changes in ice sheets, vegetation, ocean circulation, biogeochemical cycling, etc. Here, I introduce the time-dependent climate sensitivity, which unifies fast-feedback and Earth system sensitivity. I show that warming projections, which include a time-dependent climate sensitivity, exhibit an enhanced feedback between surface warming and ocean CO2 solubility, which in turn leads to higher atmospheric CO2 levels and further warming. Compared with earlier studies, my results predict a much longer lifetime of human-induced future warming (23,000–165,000 y), which increases the likelihood of large ice sheet melting and major sea level rise. The main point regarding the legacy of anthropogenic greenhouse gas emissions is that, even if the fast-feedback sensitivity is no more than 3 K per CO2 doubling, there will likely be additional long-term warming from slow climate feedbacks. Time-dependent climate sensitivity also helps explaining intense and prolonged warming in response to massive carbon release as documented for past events such as the Paleocene–Eocene Thermal Maximum.

legacy
greenhouse gas emission
time-dependent climate sensitivity


The Dentition of Megalosaurid Theropods

Abstract: Theropod teeth are particularly abundant in the fossil record and frequently reported in the literature. Yet, the dentition of many theropods has not been described comprehensively, omitting details on the denticle shape, crown ornamentations and enamel texture. This paucity of information has been particularly striking in basal clades, thus making identification of isolated teeth difficult, and taxonomic assignments uncertain. We here provide a detailed description of the dentition of Megalosauridae, and a comparison to and distinction from superficially similar teeth of all major theropod clades. Megalosaurid dinosaurs are characterized by a mesial carina facing mesiolabially in mesial teeth, centrally positioned carinae on both mesial and lateral crowns, a mesial carina terminating above the cervix, and short to well-developed interdenticular sulci between distal denticles. A discriminant analysis performed on a dataset of numerical data collected on the teeth of 62 theropod taxa reveals that megalosaurid teeth are hardly distinguishable from other theropod clades with ziphodont dentition. This study highlights the importance of detailing anatomical descriptions and providing additional morphometric data on teeth with the purpose of helping to identify isolated theropod teeth in the future.


How should we estimate diversity in the fossil record? Testing richness estimators using sampling‐standardised discovery curves

Abstract: To infer genuine patterns of biodiversity change in the fossil record, we must be able to accurately estimate relative differences in numbers of taxa (richness) despite considerable variation in sampling between time intervals. Popular subsampling (=interpolation) methods aim to standardise diversity samples by rarefying the data to equal sample size or equal sample completeness (=coverage). Standardising by sample size is misleading because it compresses richness ratios, thereby flattening diversity curves. However, standardising by coverage reconstructs relative richness ratios with high accuracy. Asymptotic richness extrapolators are widely used in ecology, but rarely applied to fossil data. However, a recently developed parametric extrapolation method, TRiPS (True Richness estimation using Poisson Sampling), specifically aims to estimate the true richness of fossil assemblages. Here, we examine the suitability of a range of richness estimators (both interpolators and extrapolators) for fossil datasets, using simulations and a novel method for comparing the performance of richness estimators with empirical data. We constructed sampling‐standardised discovery curves (SSDCs) for two datasets, each spanning 150 years of palaeontological research: Mesozoic dinosaurs at global scale, and Mesozoic–early Cenozoic tetrapods from North America. These approaches reveal how each richness estimator responds to both simulated best‐case and empirical real‐world accumulation of fossil occurrences. We find that extrapolators can only truly standardise diversity data once sampling is sufficient for richness estimates to have asymptoted. Below this point, directly comparing extrapolated estimates derived from samples of different sizes may not accurately reconstruct relative richness ratios. When abundance distributions are not perfectly flat and sampling is moderate to good, but not perfect, TRiPS does not extrapolate, because it overestimates binomial sampling probabilities. Coverage‐based interpolators, by contrast, generally yield more stable subsampled diversity estimates, even in the face of dramatic increases in face‐value counts of species richness. Richness estimators that standardise by coverage are among the best currently available methods for reconstructing deep‐time biodiversity patterns. However, we recommend the use of sampling‐standardised discovery curves to understand how biased reporting of fossil occurrences may affect sampling‐standardised diversity estimates.

richness estimator
discovery curve
sample size
fossil data
extent


Evolutionary and Biological Implications of Dental Mesial Drift in Rodents: The Case of the Ctenodactylidae (Rodentia, Mammalia)

Abstract: Dental characters are importantly used for reconstructing the evolutionary history of mammals, because teeth represent the most abundant material available for the fossil species. However, the characteristics of dental renewal are presently poorly used, probably because dental formulae are frequently not properly established, whereas they could be of high interest for evolutionary and developmental issues. One of the oldest rodent families, the Ctenodactylidae, is intriguing in having longstanding disputed dental formulae. Here, we investigated 70 skulls among all extant ctenodactylid genera (Ctenodactylus, Felovia, Massoutiera and Pectinator) by using X-ray conventional and synchrotron microtomography in order to solve and discuss these dental issues. Our study clearly indicates that Massoutiera, Felovia and Ctenodactylus differ from Pectinator not only by a more derived dentition, but also by a more derived eruptive sequence. In addition to molars, their dentition only includes the fourth deciduous premolars, and no longer bears permanent premolars, conversely to Pectinator. Moreover, we found that these premolars are lost during adulthood, because of mesial drift of molars. Mesial drift is a striking mechanism involving migration of teeth allowed by both bone remodeling and dental resorption. This dental innovation is to date poorly known in rodents, since it is only the second report described. Interestingly, we noted that dental drift in rodents is always associated with high-crowned teeth favoring molar size enlargement. It can thus represent another adaptation to withstand high wear, inasmuch as these rodents inhabit desert environments where dust is abundant. A more accurate study of mesial drift in rodents would be very promising from evolutionary, biological and orthodontic points of view.

mesial drift
rodent
ctenodactylidae
molar


The oldest Gondwanan cephalopod mandibles (Hangenberg Black Shale, Late Devonian) and the mid‐Palaeozoic rise of jaws

Abstract: It is widely accepted that the effects of global sea‐level changes at the transition from the Devonian to the Carboniferous are recorded in deposits on the shelf of northern Gondwana. These latest Devonian strata had been thought to be poor in fossils due to the Hangenberg mass extinction. In the Ma'der (eastern Anti‐Atlas), however, the Hangenberg Black Shale claystones (latest Famennian) are rich in exceptionally preserved fossils displaying the remains of non‐mineralized structures. The diversity in animal species of these strata is, however, low. Remarkably, the organic‐rich claystones have yielded abundant remains of Ammonoidea preserved with their jaws, both in situ and isolated. This is important because previously, the jaws of only one of the main Devonian ammonoid clades had been found (Frasnian Gephuroceratina). Here, we describe four types of jaws of which two could be assigned confidently to the Order Clymeniida and to the Suborder Tornoceratina. These findings imply that chitinous normal‐type jaws were likely to have already been present at the origin of the whole clade Ammonoidea, i.e. in the early Emsian (or earlier). Vertebrate jaws evolved prior to the Early Devonian origin of ammonoids. The temporal succession of evolutionary events suggests that it could have been the indirect positive selection pressure towards strong (and thus preservable) jaws since defensive structures of potential prey animals would otherwise have made them inaccessible to jawless predators in the course of the mid‐Palaeozoic marine revolution. In this respect, our findings reflect the macroecological changes that occurred in the Devonian. [Correction added on 28 July 2016 after first online publication: In the Abstract, the sentence “Vertebrate jaws probably … in the Early Devonian” was amended]

cephalopod
hangenberg black shale
late devonian
jaw
ammonoid clade


New application of strontium isotopes reveals evidence of limited migratory behaviour in Late Cretaceous hadrosaurs

Abstract: Dinosaur migration patterns are very difficult to determine, often relying solely on the geographical distribution of fossils. Unfortunately, it is generally not possible to determine if a fossil taxon's geographical distribution is the result of migration or simply a wide distribution. Whereas some attempts have been made to use isotopic systems to determine migratory patterns in dinosaurs, these methods have yet to achieve wider usage in the study of dinosaur ecology. Here, we have used strontium isotope ratios from fossil enamel to reconstruct the movements of an individual hadrosaur from Dinosaur Provincial Park in Alberta, Canada. Results from this study are consistent with a range or migratory pattern between Dinosaur Provincial Park and a contemporaneous locality in the South Saskatchewan River area, Alberta, Canada. This represents a minimum distance of approximately 80 km, which is consistent with migrations seen in modern elephants. These results suggest the continent-wide distribution of some hadrosaur species in the Late Cretaceous of North America is not the result of extremely long-range migratory behaviours.

migratory behaviour
hadrosaur
north america


Jaw geometry and molar morphology in marsupial carnivores: analysis of a constraint and its macroevolutionary consequences

Abstract: In both jaw geometry and molar morphology, eutherian carnivores (order Carnivora) as a whole display greater diversity (plasticity in evolution from the primitive type) than marsupial carnivores (order Dasyurida). This is related to the difference in tooth replacement between the two taxa. In Carnivora, the permanent carnassial is preceded by a deciduous carnassial; the permanent tooth can erupt in its (geometrically) permanent position, and the post-carnassial molars are free to evolve for specialized functions or be reduced. In Dasyurida, there is relative molar progression, each erupting molar in turn functioning as a carnassial, and subsequently being pushed forwards in the jaw by the next erupting molar. Thus, all molars have carnassiform morphology, and none are free to develop for other functions. The greater plasticity of Carnivora has led to their adaptive zone being broader (as a group they are relatively more eurytopic than Dasyurida), which in turn has led to greater taxonomic diversity within Carnivora than Dasyurida. The resulting pattern from a macroevolutionary point of view is that, even in the absence of direct competition, Carnivora have had greater evolutionary “success” than Dasyurida.

molar morphology
marsupial carnivore
jaw geometry


The Anatomy of Dryptosaurus aquilunguis (Dinosauria: Theropoda) and a Review of Its Tyrannosauroid Affinities

Abstract: ABSTRACT Although among the first theropod dinosaurs known to science, and an iconic taxon in the history of dinosaur paleontology, the large carnivore Dryptosaurus aquilunguis from the Late Cretaceous of New Jersey remains poorly understood. Its anatomy has been described only in brief and its phylogenetic relationships have long been the subject of debate, although recent work proposes Dryptosaurus as a member of the tyrannosauroid clade. Here we present a thorough osteological description of the holotype of Dryptosaurus aquilunguis, supplemented with photographs of all the material, and provide extensive comparisons with other theropods, especially tyrannosauroids. In concert with recent phylogenetic analyses, our description confirms the tyrannosauroid affinities of Dryptosaurus and supports its placement as an “intermediate” taxon bracketed between small, basal forms (e.g., Guanlong, Dilong) and the derived, Late Cretaceous tyrannosaurids (e.g., Albertosaurus, Tyrannosaurus). We identify several autapomorphies of Dryptosaurus, including the combination of a reduced humerus and an enlarged hand. These forelimb proportions, which differ from the uniformly large arms of basal tyrannosauroids and uniformly atrophied arms of tyrannosaurids, suggest that forelimb reduction in tyrannosauroids may not have proceeded in a uniform fashion. Functionally, Dryptosaurus may have used both its skull and arms as weapons for prey acquisition and processing.

anatomy
dryptosaurus aquilunguis
tyrannosauroid affinity
late cretaceous
holotype


A Middle Miocene (~14 Ma) vertebrate assemblage from Palasava, Rapar Taluka, Kutch (Kachchh) District, Gujarat State, western India

Abstract: ABSTRACT The present article aims to record a recently discovered middle Miocene vertebrate assemblage (including marine and terrestrial mammals) from Palasava, Kutch (Kachchh) District, Gujarat State, western India. The faunal assemblage comprising fishes, chelonians, crocodiles, snakes, birds and mammals is significant in terms of palaeoecology, palaeoenvironment and biostratigraphy of the region and yields evidence concerning its biogeographic affinities linked to Neogene Eustatic history. Palasava fauna together with previously known Neogene (particularly Miocene) vertebrate assemblages from the Kutch region indicates the presence of a riverine-estuarine system(s) linked to the sea, i.e. the depositional centres were quite close to the sea. Furthermore, the Palasava vertebrate assemblage (recorded herein) points towards a prevalence of warm, humid/wet, tropical to sub-tropical environmental conditions. The terrestrial mammalian assemblage from Palasava represents at least seven families with six of the terrestrial mammalian taxa identified herein to the genus level, namely: Sanitherium, Sivameryx, Brachypotherium, Zygolophodon, Gomphotherium, and Deinotherium. The overall assemblage (including Zygolophodon and Deinotherium) is indicative of a Middle Miocene, 14 ± 2 Ma (Langhian to Serravallian) age for the sedimentary succession at Palasava. Furthermore, a ~ 14 Ma age for the Palasava fauna indicates a correlation to regression cycle R5 in the Tagus Valley succession of Portugal.

middle miocene
brachypotherium
zygolophodon


Our past creates our present: a brief overview of racism and colonialism in Western paleontology

Abstract: Abstract. As practitioners of a historical science, paleontologists and geoscientists are well versed in the idea that the ability to understand and to anticipate the future relies upon our collective knowledge of the past. Despite this understanding, the fundamental role that the history of paleontology and the geosciences plays in shaping the structure and culture of our disciplines is seldom recognized and therefore not acted upon sufficiently. Here, we present a brief review of the history of paleontology and geology in Western countries, with a particular focus on North America since the 1800s. Western paleontology and geology are intertwined with systematic practices of exclusion, oppression, and erasure that arose from their direct participation in the extraction of geological and biological resources at the expense of Black, Indigenous, and People of Color (BIPOC). Our collective failure to acknowledge this history hinders our ability to address these issues meaningfully and systemically in present-day educational, academic, and professional settings. By discussing these issues and suggesting some ways forward, we intend to promote a deeper reflection upon our collective history and a broader conversation surrounding racism, colonialism, and exclusion within our scientific communities. Ultimately, it is necessary to listen to members of the communities most impacted by these issues to create actionable steps forward while holding ourselves accountable for the past.

past
colonialism
western paleontology
country
reflection


Rapid Acidification of the Ocean During the Paleocene-Eocene Thermal Maximum

Abstract: The Paleocene-Eocene thermal maximum (PETM) has been attributed to the rapid release of ∼2000 × 109 metric tons of carbon in the form of methane. In theory, oxidation and ocean absorption of this carbon should have lowered deep-sea pH, thereby triggering a rapid (<10,000-year) shoaling of the calcite compensation depth (CCD), followed by gradual recovery. Here we present geochemical data from five new South Atlantic deep-sea sections that constrain the timing and extent of massive sea-floor carbonate dissolution coincident with the PETM. The sections, from between 2.7 and 4.8 kilometers water depth, are marked by a prominent clay layer, the character of which indicates that the CCD shoaled rapidly (<10,000 years) by more than 2 kilometers and recovered gradually (>100,000 years). These findings indicate that a large mass of carbon (»2000 × 109 metric tons of carbon) dissolved in the ocean at the Paleocene-Eocene boundary and that permanent sequestration of this carbon occurred through silicate weathering feedback.

ocean
paleocene-eocene thermal maximum
methane
global warming
hyperthermal event


Relaxed Molecular Clock Provides Evidence for Long-Distance Dispersal of Nothofagus (Southern Beech)

Abstract: Nothofagus (southern beech), with an 80-million-year-old fossil record, has become iconic as a plant genus whose ancient Gondwanan relationships reach back into the Cretaceous era. Closely associated with Wegener's theory of “Kontinentaldrift”, Nothofagus has been regarded as the “key genus in plant biogeography”. This paradigm has the New Zealand species as passengers on a Moa's Ark that rafted away from other landmasses following the breakup of Gondwana. An alternative explanation for the current transoceanic distribution of species seems almost inconceivable given that Nothofagus seeds are generally thought to be poorly suited for dispersal across large distances or oceans. Here we test the Moa's Ark hypothesis using relaxed molecular clock methods in the analysis of a 7.2-kb fragment of the chloroplast genome. Our analyses provide the first unequivocal molecular clock evidence that, whilst some Nothofagus transoceanic distributions are consistent with vicariance, trans-Tasman Sea distributions can only be explained by long-distance dispersal. Thus, our analyses support the interpretation of an absence of Lophozonia and Fuscospora pollen types in the New Zealand Cretaceous fossil record as evidence for Tertiary dispersals of Nothofagus to New Zealand. Our findings contradict those from recent cladistic analyses of biogeographic data that have concluded transoceanic Nothofagus distributions can only be explained by vicariance events and subsequent extinction. They indicate that the biogeographic history of Nothofagus is more complex than envisaged under opposing polarised views expressed in the ongoing controversy over the relevance of dispersal and vicariance for explaining plant biodiversity. They provide motivation and justification for developing more complex hypotheses that seek to explain the origins of Southern Hemisphere biota.

long-distance dispersal
nothofagus
southern beech
new zealand
vicariance


Hominid butchers and biting crocodiles in the African Plio–Pleistocene

Abstract: Significance The idea that early Australopithecus shaped stone tools to butcher large mammals before the emergence of Homo around 2 million years ago has excited both primatologists and archaeologists. Such claims depend on interpreting modifications found on the surfaces of fossil bones. Recent experiments involving the feeding of mammal carcasses to modern crocodiles have revealed that equifinality—the creation of similar products by different processes—is more important than previously appreciated by zooarchaeologists. Application of these findings to Ethiopian fossils casts doubt on claims for the earliest large mammal butchery and indicates the need for reassessment of all Oldowan-associated bone assemblages to determine the degree to which equifinality compromises earlier interpretations of hominid subsistence activities and their role in human evolution. Zooarchaeologists have long relied on linear traces and pits found on the surfaces of ancient bones to infer ancient hominid behaviors such as slicing, chopping, and percussive actions during butchery of mammal carcasses. However, such claims about Plio–Pleistocene hominids rely mostly on very small assemblages of bony remains. Furthermore, recent experiments on trampling animals and biting crocodiles have shown each to be capable of producing mimics of such marks. This equifinality—the creation of similar products by different processes—makes deciphering early archaeological bone assemblages difficult. Bone modifications among Ethiopian Plio–Pleistocene hominid and faunal remains at Asa Issie, Maka, Hadar, and Bouri were reassessed in light of these findings. The results show that crocodiles were important modifiers of these bone assemblages. The relative roles of hominids, mammalian carnivores, and crocodiles in the formation of Oldowan zooarchaeological assemblages will only be accurately revealed by better bounding equifinality. Critical analysis within a consilience-based approach is identified as the pathway forward. More experimental studies and increased archaeological fieldwork aimed at generating adequate samples are now required.

crocodile
human evolution
mammalian carnivore


Insights into the Ecology and Evolutionary Success of Crocodilians Revealed through Bite-Force and Tooth-Pressure Experimentation

Abstract: Background Crocodilians have dominated predatory niches at the water-land interface for over 85 million years. Like their ancestors, living species show substantial variation in their jaw proportions, dental form and body size. These differences are often assumed to reflect anatomical specialization related to feeding and niche occupation, but quantified data are scant. How these factors relate to biomechanical performance during feeding and their relevance to crocodilian evolutionary success are not known. Methodology/Principal Findings We measured adult bite forces and tooth pressures in all 23 extant crocodilian species and analyzed the results in ecological and phylogenetic contexts. We demonstrate that these reptiles generate the highest bite forces and tooth pressures known for any living animals. Bite forces strongly correlate with body size, and size changes are a major mechanism of feeding evolution in this group. Jaw shape demonstrates surprisingly little correlation to bite force and pressures. Bite forces can now be predicted in fossil crocodilians using the regression equations generated in this research. Conclusions/Significance Critical to crocodilian long-term success was the evolution of a high bite-force generating musculo-skeletal architecture. Once achieved, the relative force capacities of this system went essentially unmodified throughout subsequent diversification. Rampant changes in body size and concurrent changes in bite force served as a mechanism to allow access to differing prey types and sizes. Further access to the diversity of near-shore prey was gained primarily through changes in tooth pressure via the evolution of dental form and distributions of the teeth within the jaws. Rostral proportions changed substantially throughout crocodilian evolution, but not in correspondence with bite forces. The biomechanical and ecological ramifications of such changes need further examination.

evolutionary success
bite-force
force
tooth


Origination and Extinction through the Phanerozoic: A New Approach

Abstract: Temporal patterns of origination and extinction are essential components of many paleontological studies, but it has been difficult to obtain accurate rate estimates because the observed record of first and last appearances is distorted by the incompleteness of the fossil record. Here I analyze observed first and last appearances of marine animal and microfossil genera in a way that explicitly takes incompleteness and its variation into consideration. This approach allows estimates of true rates of origination and extinction throughout the Phanerozoic. Substantial support is provided for the proposition that most rate peaks in the raw data are real in the sense that they do not arise as a consequence of temporal variability in the overall quality of the fossil record. Even though the existence of rate anomalies is supported, their timing is nevertheless open to question in many cases. If one assumes that rates of origination and extinction are constant through a given stratigraphic interval, then peaks in revised origination rates tend to be displaced backward and extinction peaks forward relative to the peaks in the raw data. If, however, one assumes a model of pulsed turnover, with true originations concentrated at lower interval boundaries and true extinctions concentrated at upper interval boundaries, the apparent timing of extinction peaks is largely reliable at face value. Thus, whereas rate anomalies may well be real, precisely when they occurred is a question that cannot be answered definitively without independent support for a model of smooth versus pulsed rate variation. The pattern of extinction, particularly the major events, is more faithfully represented in the fossil record than that of origination. There is a tendency for the major extinction events to occur during stages in which the quality of the record is relatively high and for recoveries from extinctions to occur when the record is less complete. These results imply that interpretations of origination and extinction history that depend only on the existence of rate anomalies are fairly robust, whereas interpretations of the timing of events and the temporal covariation between origination and extinction may require substantial revision.

phanerozoic
incompleteness
face value
origination


Confirmation of Romer's Gap as a low oxygen interval constraining the timing of initial arthropod and vertebrate terrestrialization

Abstract: The first terrestrialization of species that evolved from previously aquatic taxa was a seminal event in evolutionary history. For vertebrates, one of the most important terrestrialized groups, this event was interrupted by a time interval known as Romer's Gap, for which, until recently, few fossils were known. Here, we argue that geochronologic range data of terrestrial arthropods show a pattern similar to that of vertebrates. Thus, Romer's Gap is real, occupied an interval from 360 million years before present (MYBP) to 345 MYBP, and occurred when environmental conditions were unfavorable for air-breathing, terrestrial animals. These model results suggest that atmospheric oxygen levels were the major driver of successful terrestrialization, and a low-oxygen interval accounts for Romer's Gap. Results also show that terrestrialization among members of arthropod and vertebrate clades occurred in two distinct phases. The first phase was a 65-million-year (My) interval from 425 to 360 MYBP, representing an earlier, prolonged event of complete arthropod terrestrialization of smaller-sized forms (425–385 MYBP) and a subsequent, modest, and briefer event of incipient terrestrialization of larger-sized, aquatic vertebrates (385–360 MYBP). The second phase began at 345 MYBP, characterized by numerous new terrestrial species emerging in both major clades. The first and second terrestrialization phases bracket Romer's Gap, which represents a depauperate spectrum of major arthropod and vertebrate taxa before a major Late Paleozoic colonization of terrestrial habitats.

gap
terrestrialization
atmospheric oxygen level


Independent evolution of baleen whale gigantism linked to Plio-Pleistocene ocean dynamics

Abstract: Vertebrates have evolved to gigantic sizes repeatedly over the past 250 Myr, reaching their extreme in today's baleen whales (Mysticeti). Hypotheses for the evolution of exceptionally large size in mysticetes range from niche partitioning to predator avoidance, but there has been no quantitative examination of body size evolutionary dynamics in this clade and it remains unclear when, why or how gigantism evolved. By fitting phylogenetic macroevolutionary models to a dataset consisting of living and extinct species, we show that mysticetes underwent a clade-wide shift in their mode of body size evolution during the Plio-Pleistocene. This transition, from Brownian motion-like dynamics to a trended random walk towards larger size, is temporally linked to the onset of seasonally intensified upwelling along coastal ecosystems. High prey densities resulting from wind-driven upwelling, rather than abundant resources alone, are the primary determinant of efficient foraging in extant mysticetes and Late Pliocene changes in ocean dynamics may have provided an ecological pathway to gigantism in multiple independent lineages.

whale
gigantism
plio-pleistocene
body size evolution
wind-driven upwelling


New Specimens of Nemegtomaia from the Baruungoyot and Nemegt Formations (Late Cretaceous) of Mongolia

Abstract: Two new specimens of the oviraptorid theropod Nemegtomaia barsboldi from the Nemegt Basin of southern Mongolia are described. Specimen MPC-D 107/15 was collected from the upper beds of the Baruungoyot Formation (Campanian-Maastrichtian), and is a nest of eggs with the skeleton of the assumed parent of Nemegtomaia on top in brooding position. Much of the skeleton was damaged by colonies of dermestid coleopterans prior to its complete burial. However, diagnostic characters are recovered from the parts preserved, including the skull, partial forelimbs (including the left hand), legs, and distal portions of both feet. Nemegtomaia represents the fourth known genus of oviraptorid for which individuals have been found on nests of eggs. The second new specimen, MPC-D 107/16, was collected a few kilometers to the east in basal deposits of the Nemegt Formation, and includes both hands and femora of a smaller Nemegtomaia individual. The two formations and their diverse fossil assemblages have been considered to represent sequential time periods and different environments, but data presented here indicate partial overlap across the Baruungoyot-Nemegt transition. All other known oviraptorids from Mongolia and China are known exclusively from xeric or semi-arid environments. However, this study documents that Nemegtomaia is found in both arid/aeolian (Baruungoyot Formation) and more humid/fluvial (Nemegt Formation) facies.

nemegtomaia
mongolia
baruungoyot formation


Timing of global regression and microbial bloom linked with the Permian-Triassic boundary mass extinction: implications for driving mechanisms

Abstract:
New high-resolution U-Pb dates indicate a duration of 89 ± 38 kyr for the Permian hiatus and of 14 ± 57 kyr for the overlying Triassic microbial limestone in shallow water settings of the Nanpanjiang Basin, South China. The age and duration of the hiatus coincides with the Permian-Triassic boundary (PTB) and the extinction interval in the Meishan Global Stratotype Section and Point, and strongly supports a glacio-eustatic regression, which best explains the genesis of the worldwide hiatus straddling the PTB in shallow water records. In adjacent deep marine troughs, rates of sediment accumulation display a six-fold decrease across the PTB compatible with a dryer and cooler climate as indicated by terrestrial plants. Our model of the Permian-Triassic boundary mass extinction (PTBME) hinges on the synchronicity of the hiatus with the onset of the Siberian Traps volcanism. This early eruptive phase released sulfur-rich volatiles into the stratosphere, thus simultaneously eliciting a short-lived ice age responsible for the global regression and a brief but intense acidification. Abrupt cooling, shrunk habitats on shelves and acidification may all have synergistically triggered the PTBME. Subsequently, the build-up of volcanic CO 2 induced a transient cool climate whose early phase saw the deposition of the microbial limestone.
Since the early days of stratigraphy, mass extinctions were noticed to coincide with major and global sea-level changes 1,2 that significantly alter extinction patterns and time-series of geochemical proxies. In the case of the Permian-Triassic boundary mass extinction (PTBME), the system boundary itself has been initially placed during a global eustatic regression 3 , but was subsequently placed during a global transgression 4 . The sea-level rise scenario naturally paved the way for a concomitant rise of the oxygen minimum zone as a kill mechanism, to which "lethally" hot sea-surface temperatures were recently added 5, 6 . With the exceptions of deep oceanic settings (e.g., Arrow Rocks, New Zealand 7 ; Mino Tamba Terrane, Japan 8,9 ), of few deep water shelves (e.g., Dongpan, South China 10 ) and of extremely rare shallow shelves (Musandam, United Arab Emirates 11 ), an overwhelming majority of globally distributed Permian-Triassic boundary (PTB) sections are affected by an unconformity separating the last Permian rocks from the first Triassic ones (e.g., Armenia 12 ; Canada 13 ; Pakistan 14 ; Norway 15 ; China 16 ). Intensively studied shallow water sections from South China follow this rule and the origin of this hiatus is intensively debated. Two competing mechanisms are frequently proposed: submarine dissolution through acidified waters 17 or subaerial erosion 18 . However, both mechanisms are not mutually exclusive and may conceivably have acted simultaneously 19 . In this respect, we emphasize here that climate-driven eustatic sea-level changes are commonly at the decamillennial timescale, an order of magnitude compatible with the duration of the world-wide regression that coincides with the PTB. The base of the Triassic in the equatorial shallow water sections is usually represented by the iconic microbial limestone 16 , which has been interpreted as the hallmark of ecosystem

global regression
boundary mass extinction
ice age


Not a limitless resource: ethics and guidelines for destructive sampling of archaeofaunal remains

Abstract: With the advent of ancient DNA, as well as other methods such as isotope analysis, destructive sampling of archaeofaunal remains has increased much faster than the effort to collect and curate them. While there has been considerable discussion regarding the ethics of destructive sampling and analysis of human remains, this dialogue has not extended to archaeofaunal material. Here we address this gap and discuss the ethical challenges surrounding destructive sampling of materials from archaeofaunal collections. We suggest ways of mitigating the negative aspects of destructive sampling and present step-by-step guidelines aimed at relevant stakeholders, including scientists, holding institutions and scientific journals. Our suggestions are in most cases easily implemented without significant increases in project costs, but with clear long-term benefits in the preservation and use of zooarchaeological material.

guideline
destructive sampling
archaeofaunal remain
ancient dna
isotope analysis


PENNSYLVANIAN STRATIGRAPHY AND FUSULINIDS OF CENTRAL AND EASTERN IRAN

Abstract: The Pennsylvanian succession of Central and Eastern Iran (Sardar Group) is studied in two key sections: Zaladu and Anarak. The Sardar Group (previously Sardar Formation) has been divided into two formations: the predominantly carbonate Ghaleh Formation and the predominantly siliciclastic or mixed carbonate-siliciclastic Absheni Formation. These two formations were earlier identified as Sardar 1 and Sardar 2 subformations. The Ghaleh Formation (formerly Sardar 1), of early Bashkirian age, is characterized by Eostaffella, Eostaffellina, Millerella, Plectostaffella, Semistaffella, primitive Pseudostaffella, and numerous archaediscids. The Absheni Formation (formerly Sardar 2) is upper lower Moscovian in age (late Vereian-early Kashirian) and is characterized by Profusulinella, Aljutovella, Neostaffella, Putrella, Moellerites, and Fusiella fusulinids. Poorly preserved upper Moscovian fusulinids (derived Fusiella, Fusulina, and Beedeina) occur at the top of this sequence. The hiatus between the Ghaleh and Absheni Formations corresponds to an interval from the upper Bashkirian, and probably to the lowermost Moscovian, and coincides with the replacement of predominantly carbonate sedimentation with mixed carbonate-siliciclastic sedimentation. The recently established late Gzhelian-Asselian Zaladu Formation unconformably overlies the Absheni Formation. The new data disagree with the previously proposed paleogeographic reconstruction of Central Iran and surrounding regions (including Iran-Afghanistan territory) during the Carboniferous-Early Permian. The foraminiferal assemblages from the Bashkirian-Moscovian sections of Alborz and Eastern Iran show a close resemblance in every respect. It is evident that these regions were located within a single basin connected with the basins of Taurus and Anatolia in the west and those of the Donets, Russian platform, and Urals in the north.

eastern iran
pennsylvanian succession
sardar group
palaeozoic sediment
ordovician shirgesht formation


Fossil evidence and stages of elongation of the Giraffa camelopardalis neck

Abstract: Several evolutionary theories have been proposed to explain the adaptation of the long giraffe neck; however, few studies examine the fossil cervical vertebrae. We incorporate extinct giraffids, and the okapi and giraffe cervical vertebral specimens in a comprehensive analysis of the anatomy and elongation of the neck. We establish and evaluate 20 character states that relate to general, cranial and caudal vertebral lengthening, and calculate a length-to-width ratio to measure the relative slenderness of the vertebrae. Our sample includes cervical vertebrae (n=71) of 11 taxa representing all seven subfamilies. We also perform a computational comparison of the C3 of Samotherium and Giraffa camelopardalis, which demonstrates that cervical elongation occurs disproportionately along the cranial–caudal vertebral axis. Using the morphological characters and calculated ratios, we propose stages in cervical lengthening, which are supported by the mathematical transformations using fossil and extant specimens. We find that cervical elongation is anisometric and unexpectedly precedes Giraffidae. Within the family, cranial vertebral elongation is the first lengthening stage observed followed by caudal vertebral elongation, which accounts for the extremely long neck of the giraffe.


THE ENDEMIC MARINE FISH FAUNA FROM THE EASTERN PARATETHYS RECONSTRUCTED FROM OTOLITHS FROM THE MIOCENE (MIDDLE SARMATIAN S.L.; BESSARABIAN) OF JURKINE (KERCH PENINSULA, CRIMEA)

Abstract:
Reconstructing fossil bony fish faunas using otoliths is a well-established method that allows a diverse and dense record in time and space to be assembled. Here we report about a rich otolith-based fish fauna from the middle Sarmatian s.l. (middle Bessarabian) from Jurkine, Kerch Peninsula, Crimea. The study is based on more than 5,000 specimens constituting 36 different species, 24 of which are new and 2 remain in open nomenclature. This assemblage represents the first major otolith association described from the Bessarabian. It also represents a fish fauna from the last continuous restricted marine environment that evolved in the Eastern Paratethys, was recruited from the Badenian/Tarkhanian fauna, and was not affected by the subsequent Khersonian crisis. The association of otoliths is characterized by a high content of endemic fishes that derived from the relatively well-known early Sarmatian s.l. (Volhynian) fish fauna, and it contains certain faunal elements that were trapped in the then-secluded Eastern Paratethys and did not range into younger strata. This forced endemic evolution explains the unusually high percentage of new taxa.
            The fish fauna is dominated by stenohaline marine shelf fishes apparently recruited from the Konkian and earlier Sarmatian s.l. (Volhynian) fauna after the Karaganian crisis. The families Gobiidae and Gadidae benefited most in this restricted marine environment, while deep-water fishes disappeared with the Karaganian crisis. In this study, we discuss the further evolution of Eastern Paratethyan fishes as far as can be reconstructed from the relatively limited data from post-Bessarabian strata, and we also outline targets for future research in the field.
The stratigraphic sequence of the Jurkine section is being revised based on a detailed suite of benthic foraminifera. Implications for the stratigraphy of the middle and upper Sarmatian s.l., their boundary, and the paleoenvironments of this part of the Kerch Peninsula are discussed.


A biomechanical constraint on body mass in terrestrial mammalian predators

Abstract: , Vol. 41, pp. 333–347Observations on extant mammals suggest that large body mass is selectively advanta-geous for a terrestrial predator on large herbivores. Yet, throughout the Cenozoic, somelineages of terrestrial mammalian predators attained greater maximal body masses thanothers. In order to explain this evolutionary pattern, the following biomechanical con-straint on body mass is hypothesized. The stress, set up in the humerus by the bendingmoment of the peak ground reaction force at maximal running speed, increased withincreasing body mass within a given lineage of terrestrial mammalian predators, resultingin a decreasing safety factor for the bone, until a predator could no longer attain themaximal running speed of its smaller relatives. The selective disadvantage of reducedmaximal running speed prevented further increase of body mass within the lineage.This hypothesis is tested by examining the scaling of humeral dimensions andestimating maximal body masses in several lineages of terrestrial mammalian predators.Among lineages with otherwise similar postcranial skeletons, those with the more robusthumeri at a given body mass attained the greater maximal body masses. Lineages withthe longer deltoid ridges/deltopectoral crests of the humeri and/or the more distallylocated deltoid scars (suggesting the more distal insertions of the humeral flexors) at agiven body mass also attained the greater maximal body masses. These results supportthe existence of the proposed biomechanical constraint, although paleoecological datasuggest that some lineages of terrestrial mammalian predators failed to reach the limits,imposed by this constraint, because of the small size of available prey.

biomechanical constraint
body mass
terrestrial mammalian predator


An integrative approach to understanding bird origins

Abstract: Background The origin of birds is one of the most enduring and dramatic evolutionary debates. The hypothesis that the primarily small-sized birds are nested within a theropod dinosaur group that includes the gigantic Tyrannosaurus rex has been supported by strong fossil evidence, but until recently, several important issues remained unresolved, including the origins of feathers and flight, the “temporal paradox” (the coelurosaurian theropods occur too late in the fossil record to be ancestral to the Jurassic bird Archaeopteryx), and supposed homological incongruities (e.g., the suggested homologies of three fingers in tetanuran theropods are different from those of living birds). Recent discoveries of spectacular dinosaur fossils from China and elsewhere provide new information to address these issues, and also prompt numerous studies in disciplines other than paleontology that help explain how bird characteristics originated and evolved. Evolutionary history of selected bird features inferred from multidisciplinary data. Recent studies demonstrate that major bird characteristics have evolved in a sequential way, and many of them initiated transformation early in dinosaur evolution, with some approaching modern conditions well before the origin of birds, whereas others appear only near the origin of the crown group birds. Advances The discoveries of feathered dinosaur fossils from the Jurassic and Cretaceous sediments of China and elsewhere document a diverse range of feathers from monofilamentous feathers to highly complex flight feathers, which show a general evolutionary trend of increasing complexity leading to the cladogenesis of birds. The wide occurrence of foot feathers in Mesozoic theropods (i.e., short filamentous forms in relatively basal theropods and large vaned forms in derived theropods, including early birds) clarifies feather-scale relations and integumentary evolution pertinent to flight origins and also shows that bird flight likely had evolved through a four-winged stage. With numerous discoveries of well-preserved dinosaur fossils covering a wide range of geological periods, the morphological, functional, and temporal transition from ground-living to flight-capable theropod dinosaurs is now one of the best-documented major evolutionary transitions. Meanwhile, studies in disciplines other than paleontology provide new insights into how bird characteristics originated and evolved—such as feathers, flight, endothermic physiology, unique strategies for reproduction and growth, and an unusual pulmonary system. The iconic features of extant birds, for the most part, evolved in a gradual and stepwise fashion throughout theropod evolution. However, new data also highlight occasional bursts of morphological novelty at certain stages particularly close to the origin of birds and an unavoidable complex, mosaic evolutionary distribution of major bird characteristics on the theropod tree. Research into bird origins provides a model example of how an integration of paleontological and neontological data can be used to gain a comprehensive understanding of the complexity surrounding major evolutionary transitions and to set new research directions. Outlook A refined, more robust phylogeny will be imperative to move our studies forward. A larger data set will help to increase the accuracy of phylogenetic reconstructions, but better character formulation and more accurate scorings are imperative at the current stage. In terms of character evolution, an integrative approach combining paleontological, neontological, developmental, temporal, and even paleoenvironmental data is particularly desirable. Greater examination of fossils pertaining to molecular information is also a potentially fruitful avenue for future investigation. Evolutionary scenarios for various aspects of the origin of birds have sometimes been constructed from neontological data, but any historical reconstruction must ultimately be tested using the fossil record. Consequently, dense fossil sampling along the line to modern birds and better understanding of transitional forms play key roles in such reconstructions. Recent discoveries of spectacular dinosaur fossils overwhelmingly support the hypothesis that birds are descended from maniraptoran theropod dinosaurs, and furthermore, demonstrate that distinctive bird characteristics such as feathers, flight, endothermic physiology, unique strategies for reproduction and growth, and a novel pulmonary system originated among Mesozoic terrestrial dinosaurs. The transition from ground-living to flight-capable theropod dinosaurs now probably represents one of the best-documented major evolutionary transitions in life history. Recent studies in developmental biology and other disciplines provide additional insights into how bird characteristics originated and evolved. The iconic features of extant birds for the most part evolved in a gradual and stepwise fashion throughout archosaur evolution. However, new data also highlight occasional bursts of morphological novelty at certain stages particularly close to the origin of birds and an unavoidable complex, mosaic evolutionary distribution of major bird characteristics on the theropod tree. Research into bird origins provides a premier example of how paleontological and neontological data can interact to reveal the complexity of major innovations, to answer key evolutionary questions, and to lead to new research directions. A better understanding of bird origins requires multifaceted and integrative approaches, yet fossils necessarily provide the final test of any evolutionary model. Bird evolution: How birds took to the air Research on the origin and evolution of birds has gathered pace in recent years, aided by a continuous stream of new fossil finds as well as molecular phylogenies. Bird origins, in particular, are now better understood than those of mammals, for which the early fossil record is relatively poor compared with that of birds. Xu et al. review progress in tracing the origins of birds from theropod dinosaurs, focusing especially on recent fossil finds of feathered dinosaurs of northeastern China. They integrate current research on developmental biology and functional anatomy with the paleontological record, to show how key features of birds—feathers, wings, and flight—originated and evolved, and radiated from their dinosaur forebears. Science, this issue 10.1126/science.1253293

integrative approach
bird origin
feather
flight


An advanced, new long-legged bird from the Early Cretaceous of the Jehol Group (northeastern China): insights into the temporal divergence of modern birds.

Abstract: We describe a new ornithuromorph bird species, Gansus zheni from the Lower Cretaceous lacustrine deposits of the Jiufotang Formation (Jehol Group), Liaoning Province, China. A cladistic analysis resolves Gansus zheni as the sister taxon of the roughly contemporaneous Gansus yumenensis (Xiagou Formation, Gansu Province), and together as the most immediate outgroup to Ornithurae. Gansus zheni is the most advanced bird known today for the Jehol Biota. Its discovery provides the best-documented case of inter-basinal correlations (Jehol and Changma basins of Liaoning and Gansu provinces, respectively) using low-taxonomic clades of fossil birds. The existence of close relatives of Ornithurae in deposits formed at about 120 million years ago helps to mitigate the long-standing controversy between molecular and paleontological evidence for the temporal divergence of modern birds (Neornithes).

china
temporal divergence
modern bird
gansus zheni


Unlocking the early fossil record of the arthropod central nervous system

Abstract: Extant panarthropods (euarthropods, onychophorans and tardigrades) are hallmarked by stunning morphological and taxonomic diversity, but their central nervous systems (CNS) are relatively conserved. The timing of divergences of the ground pattern CNS organization of the major panarthropod clades has been poorly constrained because of a scarcity of data from their early fossil record. Although the CNS has been documented in three-dimensional detail in insects from Cenozoic ambers, it is widely assumed that these tissues are too prone to decay to withstand other styles of fossilization or geologically older preservation. However, Cambrian Burgess Shale-type compressions have emerged as sources of fossilized brains and nerve cords. CNS in these Cambrian fossils are preserved as carbon films or as iron oxides/hydroxides after pyrite in association with carbon. Experiments with carcasses compacted in fine-grained sediment depict preservation of neural tissue for a more prolonged temporal window than anticipated by decay experiments in other media. CNS and compound eye characters in exceptionally preserved Cambrian fossils predict divergences of the mandibulate and chelicerate ground patterns by Cambrian Stage 3 (ca 518 Ma), a dating that is compatible with molecular estimates for these splits.

early fossil record
nervous system
tissue
decay experiment


First evidence of mutualism between ancient plant lineages (Haplomitriopsida liverworts) and Mucoromycotina fungi and its response to simulated Palaeozoic changes in atmospheric CO2

Abstract: The discovery that Mucoromycotina, an ancient and partially saprotrophic fungal lineage, associates with the basal liverwort lineage Haplomitriopsida casts doubt on the widely held view that Glomeromycota formed the sole ancestral plant–fungus symbiosis. Whether this association is mutualistic, and how its functioning was affected by the fall in atmospheric CO2 concentration that followed plant terrestrialization in the Palaeozoic, remains unknown. We measured carbon-for-nutrient exchanges between Haplomitriopsida liverworts and Mucoromycotina fungi under simulated mid-Palaeozoic (1500 ppm) and near-contemporary (440 ppm) CO2 concentrations using isotope tracers, and analysed cytological differences in plant–fungal interactions. Concomitantly, we cultured both partners axenically, resynthesized the associations in vitro, and characterized their cytology. We demonstrate that liverwort–Mucoromycotina symbiosis is mutualistic and mycorrhiza-like, but differs from liverwort–Glomeromycota symbiosis in maintaining functional efficiency of carbon-for-nutrient exchange between partners across CO2 concentrations. Inoculation of axenic plants with Mucoromycotina caused major cytological changes affecting the anatomy of plant tissues, similar to that observed in wild-collected plants colonized by Mucoromycotina fungi. By demonstrating reciprocal exchange of carbon for nutrients between partners, our results provide support for Mucoromycotina establishing the earliest mutualistic symbiosis with land plants. As symbiotic functional efficiency was not compromised by reduced CO2, we suggest that other factors led to the modern predominance of the Glomeromycota symbiosis.

haplomitriopsida liverwort
mucoromycotina
atmospheric co2 concentration