Evolution: like any other science it is predictable

Evolutionary biology rejoices in the diversity of life, but this comes at a cost: other than working in the common framework of neo-Darwinian evolution, specialists in, for example, diatoms and mammals have little to say to each other. Accordingly, their research tends to track the particularities and peculiarities of a given group and seldom enquires whether there are any wider or deeper sets of explanations. Here, I present evidence in support of the heterodox idea that evolution might look to a general theory that does more than serve as a tautology (‘evolution explains evolution’). Specifically, I argue that far from its myriad of products being fortuitous and accidental, evolution is remarkably predictable. Thus, I urge a move away from the continuing obsession with Darwinian mechanisms, which are entirely uncontroversial. Rather, I emphasize why we should seek explanations for ubiquitous evolutionary convergence, as well as the emergence of complex integrated systems. At present, evolutionary theory seems to be akin to nineteenth-century physics, blissfully unaware of the imminent arrival of quantum mechanics and general relativity. Physics had its Newton, biology its Darwin: evolutionary biology now awaits its Einstein.     

Potential for Powered Flight Neared by Most Close Avialan Relatives,but Few Crossed Its Thresholds

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Feather evolution exemplifies sexually selected bridges across the adaptive landscape

Over the last two decades, paleontologists have pieced together the early evolutionary history of feathers. Simple hair‐like feathers served as insulating pelage, but the first feathers with complex branching structures and a plainer form evolved for the purpose of sexual display. The evolution of these complex display feathers was essential to the later evolution of flight. Feathers illustrate how sexual selection can generate complex novel phenotypes, which are then available for natural selection to modify and direct toward novel functions. In the longstanding metaphor of the adaptive landscape, sexual selection is a means by which lineages resting on one adaptive peak may gradually bridge a gap to another peak, without the landscape itself being first altered by environmental changes.     

Two new theropod egg sites from the Late Jurassic Lourinhã Formation,Portugal

Two new Late Jurassic (uppermost Late Kimmeridgian) dinosaur eggshell sites are described, Casal da Rola and Porto das Barcas, both near Lourinhã, central-west Portugal. Casal da Rola yields eggshells with an obliquiprismatic morphotype comparable to those from a nest with the associated fossil embryos from Paimogo, tentatively assigned to the theropod Lourinhanosaurus antunesi. The Porto das Barcas eggshells have a dendrospherulitic morphotype with a prolatocanaliculate pore system. This morphotype was also recognised in eggshells from a clutch with associated Torvosaurus embryos at the Porto das Barcas locality. A preliminary cladistic analysis of eggshell morphology suggests theropod affinities for the Casal da Rola eggs, but is unable to resolve the phylogenetic position of the Porto das Barcas eggs. The eggshells at both sites are preserved in distal flood plain mudstones and siltstones. Carbonate concretions within the deposits indicate paleosol development.     

New Important Iguanodontid and Theropod Trackways of the Tracksite Obernkirchen in the Berriasian of NW Germany and Megatracksite Concept of Central Europe

This article examines the high-resolution track horizon stratigraphy at the outcrop Obernkirchen. Massive sandstones, products of marine sand bar and fluviatile environments are present at the tracksite. Recently two track beds were examined in the outcrop. One new track slab of the lower track bed is described exposing well-preserved quadrupedal iguanodontid tracktypes of Iguanodontipus Sarjeant, Delair, and Lockley, 1998 Sarjeant, W. A. S., Delair, J. B. and Lockley, M. G. 1998. The footprints of Iguanodon: a history and taxonomic study. Ichnos, 6: 183–202. [Taylor & Francis Online] , [Google Scholar], and bipedal theropod tracks Megalosauropus Kaever and Lapparent, 1974 Kaever, M. and Lapparent, A. F. de. 1974. Les traces des pas le Dinosaures du Jurassique des Barkhausen (Basse Saxe, Allemagne). Bulletin de la Societé Geologique Français, 16: 516–525.  [Google Scholar]. The ichnogenus Iguanodontipus is discussed and the diagnosis extended. The tracksite Obernkirchen belongs to a megatracksite of the ancient coastline of the marginal marine Hercynic Basin of the Lower Cretaceous of Europe, including the four well-known sites Obernkirchen, Bad Rehburg, Münchehagen, and Bückeburg of Northwest Germany. Three different tracktypes of huge sauropods, theropods, and ornithopods are abundant at basal Lower Cretaceous siliciclastic coastlines in different regions in Spain, Portugal, England, Germany, and Switzerland. Dinosaur tracks are also present in carbonate platform environments of northern Italy and Istria.     

A phenology of the evolution of endothermy in birds and mammals

Recent palaeontological data and novel physiological hypotheses now allow a timescaled reconstruction of the evolution of endothermy in birds and mammals. A three‐phase iterative model describing how endothermy evolved from Permian ectothermic ancestors is presented. In Phase One I propose that the elevation of endothermy – increased metabolism and body temperature (T_b) – complemented large‐body‐size homeothermy during the Permian and Triassic in response to the fitness benefits of enhanced embryo development (parental care) and the activity demands of conquering dry land. I propose that Phase Two commenced in the Late Triassic and Jurassic and was marked by extreme body‐size miniaturization, the evolution of enhanced body insulation (fur and feathers), increased brain size, thermoregulatory control, and increased ecomorphological diversity. I suggest that Phase Three occurred during the Cretaceous and Cenozoic and involved endothermic pulses associated with the evolution of muscle‐powered flapping flight in birds, terrestrial cursoriality in mammals, and climate adaptation in response to Late Cenozoic cooling in both birds and mammals. Although the triphasic model argues for an iterative evolution of endothermy in pulses throughout the Mesozoic and Cenozoic, it is also argued that endothermy was potentially abandoned at any time that a bird or mammal did not rely upon its thermal benefits for parental care or breeding success. The abandonment would have taken the form of either hibernation or daily torpor as observed in extant endotherms. Thus torpor and hibernation are argued to be as ancient as the origins of endothermy itself, a plesiomorphic characteristic observed today in many small birds and mammals.     

Jaw biomechanics and the evolution of biting performance in theropod dinosaurs

Despite the great diversity in theropod craniomandibular morphology, the presence and distribution of biting function types across Theropoda has rarely been assessed. A novel method of biomechanical profiling using mechanical advantage computed for each biting position along the entirety of the tooth row was applied to 41 extinct theropod taxa. Multivariate ordination on the polynomial coefficients of the profiles reveals the distribution of theropod biting performance in function space. In particular, coelophysoids are found to occupy a unique region of function space, while tetanurans have a wide but continuous function space distribution. Further, the underlying phylogenetic structure and evolution of biting performance were investigated using phylogenetic comparative methods. There is a strong phylogenetic signal in theropod biomechanical profiles, indicating that evolution of biting performance does not depart from Brownian motion evolution. Reconstructions of ancestral function space occupation conform to this pattern, but phylogenetically unexpected major shifts in function space occupation can be observed at the origins of some clades. However, uncertainties surround ancestor estimates in some of these internal nodes, so inferences on the nature of these evolutionary changes must be viewed with caution.     

从新的古生物学及今生物学资料看羽毛的起源与早期演化(英文)

近年来关于羽毛和羽状皮肤衍生物的研究极大促进了我们对羽毛起源与早期演化的理解。结合最新的古生物学与今生物学资料,对一些保存了皮肤衍生物的非鸟恐龙标本进行观察研究,为这个重要的进化问题提供了新见解。推测羽毛的演化在鸟类起源之前就以下列顺序完成了5个主要的形态发生事件:1)丝状和管状结构的出现;2)羽囊及羽枝脊形成;3)羽轴的发生;4)羽平面的形成;5)羽状羽小支的产生。这些演化事件形成了多种曾存在于各类非鸟初龙类中的羽毛形态,但这些形态在鸟类演化过程中可能退化或丢失了;这些演化事件也产生了一些近似现代羽毛或者与现代羽毛完全相同的羽毛形态。非鸟恐龙身上的羽毛有一些现代羽毛具有的独特特征,但也有一些现生鸟羽没有的特征。尽管一些基于发育学资料建立的有关鸟类羽毛起源和早期演化的模型推测羽毛的起源是一个全新的演化事件,与爬行动物的鳞片无关,我们认为用来定义现代鸟羽的特征应该是逐步演化产生的,而不是突然出现。因此,对于羽毛演化而言,一个兼具逐步变化与完全创新的模型较为合理。从目前的证据推断,最早的羽毛既不是用来飞行也不是用来保暖,各种其他假说皆有可能,其中包括展示或者散热假说。展开整合性的研究有望为羽毛的起源问题提供更多思路。     

The diet of early birds based on modern and fossil evidence and a new framework for its reconstruction

Birds are some of the most diverse organisms on Earth, with species inhabiting a wide variety of niches across every major biome. As such, birds are vital to our understanding of modern ecosystems. Unfortunately, our understanding of the evolutionary history of modern ecosystems is hampered by knowledge gaps in the origin of modern bird diversity and ecosystem ecology. A crucial part of addressing these shortcomings is improving our understanding of the earliest birds, the non-avian avialans (i.e. non-crown birds), particularly of their diet. The diet of non-avian avialans has been a matter of debate, in large part because of the ambiguous qualitative approaches that have been used to reconstruct it. Here we review methods for determining diet in modern and fossil avians (i.e. crown birds) as well as non-avian theropods, and comment on their usefulness when applied to non-avian avialans. We use this to propose a set of comparable, quantitative approaches to ascertain fossil bird diet and on this basis provide a consensus of what we currently know about fossil bird diet. While no single approach can precisely predict diet in birds, each can exclude some diets and narrow the dietary possibilities. We recommend combining (i) dental microwear, (ii) landmark-based muscular reconstruction, (iii) stable isotope geochemistry, (iv) body mass estimations, (v) traditional and/or geometric morphometric analysis, (vi) lever modelling, and (vii) finite element analysis to reconstruct fossil bird diet accurately. Our review provides specific methodologies to implement each approach and discusses complications future researchers should keep in mind. We note that current forms of assessment of dental mesowear, skull traditional morphometrics, geometric morphometrics, and certain stable isotope systems have yet to be proven effective at discerning fossil bird diet. On this basis we report the current state of knowledge of non-avian avialan diet which remains very incomplete. The ancestral dietary condition in non-avian avialans remains unclear due to scarce data and contradictory evidence in Archaeopteryx. Among early non-avian pygostylians, Confuciusornis has finite element analysis and mechanical advantage evidence pointing to herbivory, whilst Sapeornis only has mechanical advantage evidence indicating granivory, agreeing with fossilised ingested material known for this taxon. The enantiornithine ornithothoracine Shenqiornis has mechanical advantage and pedal morphometric evidence pointing to carnivory. In the hongshanornithid ornithuromorph Hongshanornis only mechanical advantage evidence indicates granivory, but this agrees with evidence of gastrolith ingestion in this taxon. Mechanical advantage and ingested fish support carnivory in the songlingornithid ornithuromorph Yanornis. Due to the sparsity of robust dietary assignments, no clear trends in non-avian avialan dietary evolution have yet emerged. Dietary diversity seems to increase through time, but this is a preservational bias associated with a predominance of data from the Early Cretaceous Jehol Lagerstätte. With this new framework and our synthesis of the current knowledge of non-avian avialan diet, we expect dietary knowledge and evolutionary trends to become much clearer in the coming years, especially as fossils from other locations and climates are found. This will allow for a deeper and more robust understanding of the role birds played in Mesozoic ecosystems and how this developed into their pivotal role in modern ecosystems.