The oldest European fossil songbird from the early Oligocene of Germany

We report on the oldest European songbird (Passeriformes), from the early Oligocene (30–34 million years ago) of Frauenweiler in Germany. The specimen represents the earliest associated remains of an early Tertiary passerine described so far. It ties the first appearance of Passeriformes in Europe to a minimum age of 30 million years. Passeriform birds are absent in Eocene deposits that yielded abundant remains of small land birds and apparently dispersed into Europe around the Eocene/Oligocene boundary (about 34 million years ago), not at the Oligocene/Miocene boundary (about 24 mya) as hitherto thought. This possibly relates the appearance of songbirds in Europe to a well-known major faunistic break at the Eocene/Oligocene boundary, called the grande coupure. The Frauenweiler songbird most notably differs from extant Passeriformes in having a larger processus procoracoideus on the coracoid and appears to be outside Eupasseres, the taxon which includes Oscines (all modern European and most Old World songbirds) and Suboscines (most South and Central American songbirds). It shows that there were earlier dispersal events of non-oscine songbirds into Europe before the arrival of Oscines from the Australian continental plate towards the late Oligocene.     

丛枝菌根真菌对铈污染土壤上玉米生长和铈吸收的影响

采用温室盆栽试验的方法,模拟不同程度的铈(Ce)污染土壤(100、500、1 000 mg·kg~(-1)),研究接种丛枝菌根(arbuscular mycorrhizal,AM)真菌Glomus aggregatum(GA)和Funneliformis mosseae(FM)对玉米(Zea mays L.)菌根侵染率、生物量、营养元素吸收、C:N:P生态化学计量比和稀土元素Ce吸收、转运的影响,旨在为稀土污染土壤的治理提供基础数据和技术支持.结果表明,GA和FM均与玉米成功建立了互惠共生关系,平均菌根侵染率为7.12%~74.47%;随着土壤Ce污染程度的增加,玉米菌根侵染率、地上部和根部的生物量、营养元素N、P、K的吸收量以及Ce从根到叶的转运率均显著降低,而玉米植株的C:P和N:P、地上部和根部Ce含量显著升高.接种AM真菌不同程度地促进了玉米的生长,在重度Ce污染土壤接种FM对玉米生长的促进作用显著高于GA,而在轻度和中度Ce污染土壤二者之间无显著性差异;接种显著改善了玉米的营养状况,一定程度上显著降低了玉米植株的C:N:P在轻度和中度Ce污染土壤GA对营养元素吸收的促进作用要显著高于FM,而在重度Ce污染土壤则反之;接种也显著增加了轻度Ce污染土壤玉米地上部和根部Ce含量,而对中度和重度Ce污染土壤上玉米Ce的吸收无显著影响,促进了Ce从根部到地上部分的转运.试验初步证明,AM真菌能够减轻稀土元素Ce对植物的毒害作用,在稀土污染土壤的植物修复中具有潜在的应用价值.     

菌根真菌重金属耐性机制研究进展

菌根真菌在自然界中广泛存在,能与大多数陆地植物形成共生体,菌根共生体系对于植物适应各种逆境胁迫具有重要意义.在重金属污染土壤中通常也能发现菌根真菌,某些菌根真菌对重金属表现出较强的耐受性,在污染土壤修复方面显示出应用潜力.本文从生境选择、生理适应、功能基因表达调控等层面综述了菌根真菌重金属耐性机制方面的最新研究进展,并对今后的研究方向进行了展望,旨在推进相关机制研究及菌根技术在重金属污染土壤修复中的应用.     

Floods and Other Possible Adverse Environmental Effects of Meadowland Area Decline in Former West Germany

6   ha, or 6% of the country's total area. The environmental implications of this large-scale conversion have so far received little attention; the present study examined some of these implications. A review of research on soil physical and chemical aspects of the conversion of permanent grassland into arable land reveals that such a large-scale conversion may have considerable effects upon the environment. For example, due to the mineralization of soil organic matter a release of NO₃ and CO₂ into the environment can be expected on the order of 10 t N and 100 t C per hectare. Environmentally equally severe, if not worse, is the increased amount of surface runoff that can be expected from converted grassland soils in arable land during winter because of surface sealing and soil compaction. This increased surface runoff, in combination with the runoff from other farmland, may be one of the reasons for the growing frequency of floods along major German rivers in recent years. In view of the lasting adverse environmental effects of permanent grassland conversion and the subsidized agricultural surpluses in Germany today, we conclude that a reconversion of arable land into permanent grassland may be beneficial both environmentally and economically.     

Isolation and fractionation of soil humin using alkaline urea and dimethylsulphoxide plus sulphuric acid

Humin, the most recalcitrant and abundant organic fraction of soils and of sediments, is a significant contributor to the stable carbon pool in soils and is important for the global carbon budget. It has significant resistance to transformations by microorganisms. Based on the classical operational definition, humin can include any humic-type substance that is not soluble in water at any pH. We demonstrate in this study how sequential exhaustive extractions with 0.1 M sodium hydroxide (NaOH) + 6 M urea, followed by dimethylsulphoxide (DMSO) + 6% (v/v) sulphuric acid (H₂SO₄) solvent systems, can extract 70–80% of the residual materials remaining after prior exhaustive extractions in neutral and aqueous basic media. Solid-state ¹³C NMR spectra have shown that the components isolated in the base + urea system were compositionally similar to the humic and fulvic acid fractions isolated at pH 12.6 in the aqueous media. The NMR spectra indicated that the major components isolated in the DMSO + H₂SO₄ medium had aliphatic hydrocarbon associated with carboxyl functionalities and with lesser amounts of carbohydrate and peptide and minor amounts of lignin-derived components. The major components will have significant contributions from long-chain fatty acids, waxes, to cuticular materials. The isolates in the DMSO + H₂SO₄ medium were compositionally similar to the organic components that resisted solvation and remained associated with the soil clays. It is concluded that the base + urea system released humic and fulvic acids held by hydrogen bonding or by entrapment within the humin matrix. The recalcitrant humin materials extracted in DMSO + H₂SO₄ are largely biological molecules (from plants and the soil microbial population) that are likely to be protected from degradation by their hydrophobic moieties and by sorption on the soil clays. Thus, the major components of humin do not satisfy the classical definitions for humic substances which emphasise that these arise from microbial or chemical transformations in soils of the components of organic debris.     

Effects of arbuscular mycorrhizal fungi inoculation on arsenic accumulation by tobacco (Nicotiana tabacum L.)

A pot experiment was conducted to study the e ects of arbuscular mycorrhizal (AM) fungi (from contaminated or uncontaminated soils) on arsenic (As) uptake of tobacco (Nicotiana tabacum L.) in As-contaminated soil. Mycorrhizal colonization rate, dry weight, As and P uptake by plants, concentrations of water-extractable As and As fractions were determined. A low mycorrhizal colonization rate (< 25%) was detected. Our research indicated that AM fungi isolated from polluted soils were no more e ective than those from unpolluted soils when grown in symbiosis with tobacco. No significant di erences were observed in roots and stalks dry weights among all treatments. Leaves and total plant dry weights were much higher in Glomus versiforme treatment than that in control treatment. As contents in roots and stalks from mycorrhizal treatments were much lower than that from control treatment. Total plant As content exhibited the same trend. P concentrations in tobacco were not a ected by colonization, nor were stalks, leaves and total plant P contents. Roots P contents were remarkably lower in HN treatments than in other treatments. Meanwhile, decreased soil pH and lower water-extractable As concentrations and higher levels of As fraction bound to well-crystallized hydrous oxides of Fe and Al were found in mycorrhizal treatments than in controls. The protective e ect of mycorrhiza against plant As uptake may be associated with changes in As solubility mediated by changing soil pH. These results indicated that under As stress, proper mechanisms employed by AM fungi can protect tobacco against As uptake. Results confirmed that AM fungi can play an important role in food quality and safety.     

Torpor use during gestation and lactation in a primate

Torpor is an energy-saving mechanism that allows endotherms to overcome energetic challenges. Torpor should be avoided during reproduction because of potential incompatibility with offspring growth. To test if torpor can be used during gestation and lactation to compensate for food shortage, we exposed reproductive female grey mouse lemurs (Microcebus murinus), a heterothermic primate, to different levels of food availability. Torpor use was characterised by daily skin temperature profiles, and its energetic outcome was assessed from changes in body mass. Food shortage triggered torpor during the end of the gestation period (n = 1), ranging from shallow in response to 40% food restriction to deep daily torpor in response to 80% restriction. During the early period of lactation, females fed ad libitum (n = 2) or exposed to a 40% restriction (n = 4) remained normothermic; but 80% food restricted females (n = 5) gave priority to energy saving, increasing the frequency and depth of torpor bouts. The use of torpor was insufficient to compensate for 80% energetic shortage during lactation resulting in loss of mass from the mother and delayed growth in the pups. This study provides the first evidence that a heterothermic primate can use torpor to compensate for food shortages even during reproduction. This physiological flexibility likely evolved as a response to climate-driven fluctuations in food availability in Madagascar.     

Influences of excessive Cu on photosynthesis and growth in ectomycorrhizal Pinus sylvestris seedlings

Growth and photosynthesis responses were measured for Scots pine( Pinus sylvestris L. cv. ) inoculated with ectomycorrhizal fungi ( Suillus bovinus ) under 6.5 and 25 mg/L Cu treatments to evaluate ectomycorrhizal seedlings‘ tolerance to heavy metal stress. Results showed that excessive Cu can significantly impair the growth and photosynthesis of pine seedlings, but such impairment is much smaller to the ectomycorrhizal seedlings. Under 25mg/L Cu treatment, the dry weight of ectomycorrhizal seedlings is 25% lower than the control in contrary to 53% of the non-mycorrhizal seedlings, and the fresh weight of ectomycorrhizal roots was significantly higher than those of non-mycorrhizal roots, about 25% and 42% higher at 6.5 and 25 mg/L Cu treatments respectively. Furthermore,ectomycorrhizal fungi induced remarkable difference in the growth rate and pigment content of seedlings under excessive Cu stress. At 2.5 mg/L Cu, the contents of total chlorophyll, chlorophyll-a and chlorophyll-b were 30% higher in ectomycorrhizal plants than those in non-mycorrhizal plants. O2 evolution and electron transport of PSI and PSII were restrained by elevated Cu stress. However, no significant improvement was observed in reducing the physiological restraining in ectomycorrhizal seedlings over the non-mycorrhizal ones.     

How water saving irrigation contributes to climate change resilience—a case study of practices in China

A warming climate system is now an indisputable fact. An effective response to climate change should include both mitigation and adaptation. Water is essential to human survival and social development. But the shortage of water resources is a worldwide problem, which in China has been exacerbated by climate change. In order to find out how to cope with climate change successfully, this study, on the basis of China statistical data 2007–2009, quantitatively analyzes the role of water saving irrigation (WSI) in addressing climate change. The study shows that water saving irrigation (WSI) can serve as a useful enabler in dealing with climate change. From the perspective of mitigation, the 3-year total CO₂ emission reduction stands at 34.67 (21.83 ~ 47.48) Mt, about per year 11.56(7.28 ~ 15.83)Mt. From the perspective of adaptation, the total water saved from 2007 to 2009 stands at 96.85 (61.81 ~ 129.66) Gm³. If per unit farmland irrigation takes a 3-year average of agricultural water consumption, the water saved in 2009 is enough to irrigate additional 5.70 (3.80 ~ 7.80) Mhm², or to increase the grain yield by 22.04 (14.68 ~ 30.15) Gt. In addition, WSI can reduce soil salinization and conserve soil to sustain land productivity and environmental benefits. So WSI can be a positive measure in coping with climate change when it is rightly deployed. However, the costs and local context of such practices call for further studies.     

纳米氧化锌、硫酸锌和AM真菌对玉米生长的影响

纳米氧化锌(Zn O)是应用最为广泛但具有一定生物毒性的金属型纳米颗粒(nanoparticles,NPs)之一,而丛枝菌根(arbuscular mycorrhizal,AM)真菌能改善宿主植物矿质营养和增强宿主植物抗逆性,但纳米Zn O和其他锌污染物之间的关系以及AM真菌对其生物效应的影响目前尚不清楚.通过温室盆栽试验,研究了单一或复合施加纳米Zn O、ZnSO_4(500mg·kg~(-1))时接种AM真菌Funneliformis mosseae BEG 167对玉米生长的影响.结果表明,纳米Zn O对AM真菌侵染和玉米植株生长有一定抑制作用,表现出植物毒性,且与同浓度(500 mg·kg~(-1))下的ZnSO_4作用类似.与非菌根对照相比,接种AM真菌降低了玉米植株的Zn含量或Zn吸收量,且在复合处理中对玉米生长表现出较好的促生作用.结果首次表明,纳米ZnO与ZnSO_4在生物毒性上存在复杂的交互作用,而接种AM真菌在二者复合污染时对玉米具有一定的保护作用.     

外加不同铁源和丛枝菌根对砷污染土壤上玉米生长及磷、砷吸收的影响

通过盆栽模拟试验研究了添加不同铁源及接种丛枝菌根真菌(Arbuecular mycorrhizal fungi,AMF)对高砷污染土壤上玉米生长及其吸收磷、砷、铁、锰、铜和锌的影响.试验结果表明,与对照相比,添加硫酸亚铁并接种AMF显著地提高了土壤有效铁、锰含量,降低了土壤中水溶性砷、磷含量以及玉米地上部砷的含量,并极大地增加了植株对磷的吸收,提高了植株体内磷砷吸收量之比,从而明显地改善了植株的菌根建成和生长状况.在不接种情况下,硫酸亚铁和石灰混合处理显著地降低了土壤水溶性砷、磷含量及根系砷含量,并明显增加了磷的吸收以及磷、砷吸收量的比值,使玉米植株生物量和根长增加的幅度较其它铁源处理时更大.尽管添加铁尾矿砂增加了土壤水溶性磷的含量以及植株磷的吸收而在一定程度上改善了玉米的生长,但这种效果以不接种时更为明显,因而有必要根据土壤的污染程度调整铁尾矿砂的添加量和接种抗性菌株,以强化植物的抗砷能力.     

不同磷水平下丛枝菌根真菌对纳米氧化锌生物效应的影响

纳米ZnO颗粒是应用最为广泛金属型纳米颗粒(nanoparticles,NPs)之一,对作物和土壤微生物的影响值得关注.丛枝菌根(arbuscular mycorrhizal,AM)是自然界中普遍存在的植物-真菌共生体,对各种环境胁迫具有一定的抵御能力,但菌根效应受土壤和植物磷含量的影响.分别设置0、20、50、100 mg·kg~(-1)这4个磷水平,在接种或不接种AM真菌Funneliformis mosseae、添加或不添加纳米ZnO(500 mg·kg~(-1))条件下在温室中利用玉米进行土壤盆栽试验.结果表明,纳米ZnO没有显著影响玉米生长,但不利于菌根侵染和磷素吸收,并引起锌在植物体内的积累.纳米ZnO和高磷降低玉米菌根侵染,但AM真菌在所有磷水平下均显著促进植物生长.施磷和接菌均可使土壤p H升高、降低纳米ZnO源锌的生物有效性,从而降低锌向玉米地上部分的转运和积累,体现出一定保护作用.接菌在多数情况下显示出积极的菌根效应,尤其在低磷、添加纳米ZnO条件下更为显著.结果首次表明,AM真菌、磷肥均有助于减轻纳米ZnO引起的土壤污染及其所产生的生态和健康风险.     

Carbon sequestration of paddy fields in Western Jilin of China during 1989–2004

The study area of this article, Western Jilin province of China, was a typical area responding to global changing in middle latitude areas. In this paper, by interpreting the thematic mapper (TM) images of the study area in the years of 1989, 1996, 2000 and 2004, the land use/cover change (LUCC) data were achieved, which included the area of paddy fields and its spatial distributions. 113 soil samples were collected to obtain soil organic carbon (SOC) data of different land use types. After that, the organic matter contents of these samples were measured by using the potassium dichromate oxidation-outer heating method. Based on the data above, the amount of SOC sequestrated by the surface soil (0~30 cm) of paddy fields was calculated. The result showed that: the area of paddy fields was increasing continuously in western Jilin, from 11.28 × 10⁴ hm² in 1989 to 22.77 × 10⁴ hm² in 2004. Paddy fields transferred from wetlands, grasslands and water areas accounted for the main part of the paddy fields in 2004, the areas were 3.09 × 10⁴ hm², 2.98 × 10⁴ hm² and 2.8 × 10⁴ hm², respectively. And paddy fields with a total area of 0.83 × 10⁴ hm² degraded into saline-alkali lands. The amount of organic carbon sequestration in the surface layer (0–30 cm) of paddy fields was 658.86 × 10⁴ t. The primary SOC sinks located around the joint of Baicheng City and Zhenlai County, while the major SOC source located at Songyuan City and northern Qianguo County.     

菌根生物技术在大武口洗煤厂矸石山绿化中的应用初探

介绍了菌根生物技术在煤矸石山绿化中应用的可行性，并以干旱地区的宁夏太西集团有限责任公司大武口洗煤厂煤矸石山绿化为例，探讨了菌根生物技术应用的方法和效果。研究表明：干旱地区煤矸石山绿化覆土栽植是必要的，接种菌剂能促进植物生长，在立地好的区域侵染率达90％，有推广应用的潜能。     

New contributions to the study of common double mutants in the human <Emphasis Type="Italic">LDL</Emphasis> receptor gene

Variations in the gene encoding the low-density lipoprotein receptor (LDLR) can cause familial hypercholesterolemia (FH), one of the most common inherited metabolic disorders in humans. The functional effects of the p.Gln92Glu and p.Asn564His alterations are predicted as benign, but the c.313 + 1G>C and p.Lys799_Phe801del changes are believed to cause disease. Although p.Gln92Glu and c.313 + 1G>C have been observed only in Spain, p.Asn564His and p.Lys799_Phe801del are widespread in Western Europe. In order to estimate the ages (t generations) of these four variants of the gene, to determine their possible origin and to consider the influence of age and selective pressure on their spread, we analyzed 86 healthy individuals and 126 FH patients in Spain. Most of the FH patients investigated carried two of these four LDLR variants simultaneously, while only one patient carried three of them simultaneously. Haplotype analyses were based on five LDLR SNPs: c.81T>C, c.1413G>A, c.1725C>T, c.1959T>C and c.2232G>A. The results suggest that p.Gln92Glu and c.313 + 1G>C arose at about the same time (99 and 103 generations ago, respectively) in the CACTG haplotype and that p.Asn564His and p.Lys799_Phe801del appeared in the CGCCG haplotype and might be slightly more recent variations (92 and 95 generations ago, respectively). Low selective pressures could explain the maintenance of these variants in spite of their ages. The origin of p.Gln92Glu and c.313 + 1G>C appears to be in Spain whereas p.Asn564His and p.Lys799_Phe801del could have been introduced in Spain by Celtic migrations in the seventh to fifth centuries BC.     

丛枝菌根影响纳米ZnO对玉米的生物效应

人工纳米颗粒(engineered nanoparticles,ENPs)能被植物吸收、积累,随食物链进入人体而引起健康风险.丛枝菌根(arbuscular mycorrhizal,AM)真菌可与陆地生态系统中绝大多数高等植物互惠共生,可能影响ENPs的生物效应.在温室土壤盆栽条件下研究了施加不同水平纳米ZnO(0、500、1000、2000、3000 mg·kg-1)和接种AM真菌Acaulospora mellea对玉米生长和营养状况的影响.结果表明,随土壤中纳米ZnO施加水平的增加,菌根侵染率和玉米生物量均呈降低趋势,根系总长、总表面积及总体积降低,植株体内Zn含量和吸收量逐渐增加,地上部分P、N、K、Fe、Cu吸收量逐渐降低.与对照相比,接种AM真菌均促进玉米的生长,改善P、N、K营养,根系总长、总表面积及总体积增加,并在施加纳米ZnO时增加Zn在玉米根系中的分配比例.本结果首次表明,土壤中纳米ZnO对丛枝菌根具有一定毒性,而接种AM真菌能够减轻其毒性,对宿主植物起到保护作用.     

Assessment of field situations for the feasibility of vesicular-arbuscular mycorrhizal inoculation,using a forage legume as test plant

This paper reports experiments aimed at predicting ecological situations where vesicular-arbuscular mycorrhizal (VAM) inoculation would be beneficial. Twelve unsterile soils were assayed and Hedysarum coronarium, a forage legume, was the test plant. Three vesicular-arbuscular endophytes, namely Glomus mosseae, G. fasciculatus and a Glomus sp. were tested, and in all cases G. mosseae was the more efficient, with indications of some plant-fungus specificity. A considerable degree of dependency on mycorrhizas, for suitable growth and N₂-fixation, was also demonstrated for the tested legume-Rhizobium sp. system. The studied soils varied in their concentration of plant-available phosphorus and in the amount, infectivity and effectiveness of indigenous VAM propagules; however, no correlation between these parameters could be found. The level of success of the introduction of G. mosseae in the presence of naturally existing endophytes was evaluated by the extent of the plant response in terms of growth, nodulation and N and P uptake in each soil. The inoculation of G. mosseae was effective in 7 out of the 12 soils; however, it was not possible to find a correlation between any of the soil parameters studied (i.e. soluble P concentration, amount of mycorrhizal root pieces and VAM mycelium and spores) and the plant response to G. mosseae inoculation. Thus, it is necessary to emphasize the need for simple techniques to screen situations where it would be worth attempting VAM inoculation, since each particular soil must be checked for each given plant-fungus combination.     

镧-铅复合污染下AM真菌对玉米生长和镧、铅吸收的影响

采用温室盆栽试验的方法,模拟不同程度的镧-铅复合污染土壤(50、200、800 mg·kg~(-1)),研究接种丛枝菌根(arbuscular mycorrhizal,AM)、真菌Claroideoglomus etunicatum(CE)和Rhizophagus intraradices(RI)对玉米(Zea mays L.)菌根侵染率、生物量、矿质营养元素吸收、C∶N∶P生态化学计量比、稀土镧(La)和重金属铅(Pb)吸收、转运的影响,旨在为稀土-重金属复合污染土壤的治理和修复提供科学依据.结果表明,AM真菌CE和RI均与玉米建立了共生关系,平均菌根侵染率为26.7%~95.8%;随着La-Pb复合污染含量的增加,玉米植株菌根侵染率、地上部和根部生物量以及N、P、K、Ca、Mg这5种矿质营养元素含量显著降低,而玉米植株C∶P和N∶P以及地上部和根部La、Pb含量显著增加.接种2种AM真菌使玉米植株生物量显著提高了17.8%~158.9%,地上部和根部P含量显著提高了24.5%~153.8%,降低了C∶P和N∶P,符合生长速率假设.在3种程度La-Pb复合污染含量土壤上,AM真菌使玉米植株根部Pb含量显著增加了51.3%~67.7%,地上部Pb含量显著降低了16.0%~67.7%,Pb从玉米根部向地上部的转运率降低了31.5%~54.7%;同时,接种AM真菌显著增加了轻度LaPb复合污染土壤上玉米植株的La含量,在中度La-Pb复合污染土壤上却显著减少了玉米地上部的La含量,增加了玉米根部的La含量,抑制了La从根部向地上部的转运,重度La-Pb复合污染土壤上均没有显著影响.试验结果初步证明,AM真菌具有促进稀土-重金属复合污染土壤植物修复的潜力,对于稀土-重金属复合污染土壤生态系统的植被恢复具有潜在应用价值.     

Effect of inoculation with arbuscular mycorrhizal fungi on the degradation of DEHP in soil

The effect of inoculation with arbuscular mycorrhizal(AM) fungi( Acaulospora lavis) on the degradation of di(2-ethylhexyl) phthalate(DEHP) in soil was studies. Cowpea plants( Pigna sinensis) were used as host plants and grown in a specially designed rhizobox. The experimental results indicated that, both in sterile and non-sterile soil,mycorrhizal colonization rates were much higher in the mycorrhizal plants than in the non-mycorrhizal plants. Addition of 4 mg/kg DEHP slightly affected mycorrhizal colonization, but the addition of 100 mg/kg DEHP significantly decreased mycorrhizal colonization. DEHP degradation in the mycorrhizosphere (Ms) and hyphosphere (Hs),especially in the Hs, increased after inoculation with Acaulospora lavis. It is concluded that mycorrhizal hyphae play an important role in the plant uptake, degradation and translocation of DEHP. The mechanism might be attributed to increased numbers of bacteria and actinomycetes and activity of dehydrogenase, urease and acid phosphatase in the Ms and Hs by mycorrhizal fungi.     

First complete sauropod dinosaur skull from the Cretaceous of the Americas and the evolution of sauropod dentition

Sauropod dinosaur bones are common in Mesozoic terrestrial sediments, but sauropod skulls are exceedingly rare—cranial materials are known for less than one third of sauropod genera and even fewer are known from complete skulls. Here we describe the first complete sauropod skull from the Cretaceous of the Americas, Abydosaurus mcintoshi, n. gen., n. sp., known from 104.46 ± 0.95 Ma (megannum) sediments from Dinosaur National Monument, USA. Abydosaurus shares close ancestry with Brachiosaurus, which appeared in the fossil record ca. 45 million years earlier and had substantially broader teeth. A survey of tooth shape in sauropodomorphs demonstrates that sauropods evolved broad crowns during the Early Jurassic but did not evolve narrow crowns until the Late Jurassic, when they occupied their greatest range of crown breadths. During the Cretaceous, brachiosaurids and other lineages independently underwent a marked diminution in tooth breadth, and before the latest Cretaceous broad-crowned sauropods were extinct on all continental landmasses. Differential survival and diversification of narrow-crowned sauropods in the Late Cretaceous appears to be a directed trend that was not correlated with changes in plant diversity or abundance, but may signal a shift towards elevated tooth replacement rates and high-wear dentition. Sauropods lacked many of the complex herbivorous adaptations present within contemporaneous ornithischian herbivores, such as beaks, cheeks, kinesis, and heterodonty. The spartan design of sauropod skulls may be related to their remarkably small size—sauropod skulls account for only 1/200th of total body volume compared to 1/30th body volume in ornithopod dinosaurs.