Xinghaiornis lini (Aves: Ornithothoraces) from the Early Cretaceous of Liaoning: An Example of Evolutionary Mosaic in Early Birds

We describe a new species of Early Cretaceous bird from the Yixian Formation of Liaoning Province. Xinghaiornis lini gen. et sp. nov. is relatively large and characterized by a long, toothless rostrum and an elevated pedal digit I. The design of the skull and feet suggests that this bird was likely a mud-prober. This discovery provides strong support indicating that this avian trophic specialization originated at least 125 million years ago.

New record of a haplocyonine amphicyonid in Early Miocene of Nei Mongol fills a long-suspected geographic hiatus

犬熊科(Amphicyonidae)的4个亚科(Amphicyoninae,Daphoeninae,Haplocyoninae和Temnocyoninae)中,Haplocyoninae(简齿犬熊亚科)和Temnocyoninae(剪切犬熊亚科)是两类比较特殊的、高度食肉化的姊妹群。Haplocyoninae仅出现在欧洲的晚渐新世到早中新世,而Temnocyoninae则局限在北美的早渐新世到早中新世。目前亚洲虽还没有记录,但新近纪的亚洲无疑是欧洲与北美之间迁徙途中的必经之路。因此本文记录的新材料既是意外发现又是意料之中。2015年我们在内蒙古中部早中新世敖尔班组下红层中首次发现一枚犬熊类的左上第一臼齿。这颗臼齿虽然零星,但非常特征,属Haplocyoninae或Temnocyoninae无疑,值得记述。该牙齿由于中间的收缩及原尖周边齿带的变宽而具有明显的哑铃型轮廓。另外其原尖上的前、后脊也几乎消失,形成一种原尖缩小而且孤立的形态。上述特征与欧洲早中新世的Haplocyonoides mordax(咬合似简齿犬熊)似乎最接近,但由于材料稀少敖尔班犬熊类与北美的Temnocyon percussor更为接近的可能也不能完全排除。如果上述判断正确的话,新发现的Haplocyonoides则是目前发现的少数几例早中新世从欧洲迁移到亚洲的种类之一。这一支系在亚洲有可能延续到中中新世的Gobicyon(戈壁犬熊)。

The First Mesozoic Heterodactyl Bird from China

Dalingheornis liweii gen. et sp. nov., a new enantiornithine bird was collected from the early Cretaceous Yixian Formation in northeastern China. It is the first record of a highly specialized heterodactyl foot in Mesozoic birds. The Y-shaped furcula with short hypocleidum is different from that of other enantiornithines. The minor metacarpal is robust and longer than the major metacarpal. A long bony tail composed of 20 caudal vertebrae with chevrons resembling those of dromaeosaurids and thus, highlighting again the evolutionary relationship between birds and non-avian theropods. Well-preserved alula feathers and a heterodactyl foot provide strong evidence for the arboreal habit of Dalingheornis.

Osteological evidence for predatory behavior of the giant percrocutid (Dinocrocuta gigantea) as an active hunter

We present osteological evidence that a rhinocerotid skull belonging to a female Chilotherium wimani was bitten by a giant percrocutid, Dinocrocuta gigantea. Aided by comparative evidence of black rhino (Diceros bicornis) predation by extant spotted hyenas Crocuta crocuta, we interpret the healed wound on the C. wimani female as an injury incurred by the late Miocene D. gigantea. The hunting paleoecology of the giant percrocutid D. gigantea has long been speculated, but thus far no clear evidence has been discovered to point to the predatory habits of this carnivore. The present specimen of C. wimani provides evidence to indicate that the giant percrocutid shared similarities in predatory behavior to the modern spotted hyena: it was an active hunter in spite of the specialized bone-cracking craniodental morphology which imparted superb capability for processing bone.

Urban invaders are not bold risk-takers: a study of 3 invasive lizards in Southern California

Biological invasions threaten biodiversity worldwide,and therefore,understanding the traits of successful invaders could mitigate their spread.Many comm only invasive species do well in disturbed habitats,such as urban environments,and their abilities to effectively respond to disturbarices could con tribute to their invasiveness.Yet,there are non invasive species that also do well in disturbed habitats.The question remains whether urban invaders behave differently in urban environments than noninvaders,which could suggest an"urban-exploiting"phenotype.In Southern California,the co-occurrence of in vasive Italia n wall lizards Pod arc is siculus,brown anoles Anolis sagrei,and green anoles A.carolinensis,and native western fence lizards Sceloporus occidentalis offers an opportunity to test whether invasives exhibit consistent differences in risk-taking within human-altered habitats compared with a native species.We predicted that invasive lizards would exhibit more bold behavior by having shorter flight-initiation distances(FIDs)and by being found farther from a refuge(behaviors that would presumably maximize foraging in low-risk environments).Invasive populations had similar or longer FIDs,but were consistently found at distances closer to a refuge.Collectively,invasive lizards in urban habitats were not bolder than a native species.Relianee on nearby refuges might help species successfully invade urban habitats,and if a general pattern,may pose an added challenge in detecting or eliminating them.

巨鬣狗(Dinocrocuta gigantea)主动捕猎行为的化石骨骼学证据

报道的骨骼学证据显示一件雌性维氏大唇犀(Chilotherium wimani)的头骨上留有被巨鬣狗(Dinocrocuta gigantea)袭击的痕迹.对比现生斑鬣狗(Crocuta crocuta)对非洲黑犀(Diceros bicornis)的进攻行为,雌性大唇犀愈合的伤痕被解释为遭受晚中新世巨鬣狗攻击的后果.巨鬣狗的捕猎古生态学行为长期以来都是广泛关注的焦点,但以前一直未发现清晰的证据来指示这种食肉动物的捕猎习性.这件维氏大唇犀标本提供的证据表明巨鬣狗具有与现生斑鬣狗相似的捕猎行为:尽管其专门食骨的头骨和牙齿形态赋予巨鬣狗在腐食中处理骨头的强大能力,但它仍然是主动的捕猎者.

Dewlap size in male water anoles associates with consistent inter-individual variation in boldness

Male sexually selected signals can indicate competitive ability by honestly signaling fitnessrelevant traits such as condition or performance. However, behavior can also influence contest outcomes;in particular, boldness often predicts dominance rank and mating success. Here, we sought to determi ne whether male ornament size is associated with consiste nt in dividual differences in boldness in water anoles Anol is aquaticus. We measured the relative size of the dewlap, a flap of skin under the chin that is a sexually selected ornament in Anolis lizards, and tested for associations with responses to a novel and potentially risky environment: time to emerge from a refuge into an arena and number of head sea ns post-emergence. We found that in dividuals con siste ntly differed in both time to emerge and head sea nning (i.e., in dividual resp on ses were repeatable), and that dewlap size was negatively related to nu mber of head sea ns. This suggests that orname nt size could indicate male boldness if seanning represents antipredator vigilance. We found that males that had larger relative dewlaps were also in better body condition, but boldness (i.e., head scann ing) was not related to condition. Lastly, we found con siste nt d iff ere nces in behavior betwee n trials, showing that anoles were becoming habituated or sensitized to the testing arena. Overall, our study shows that in additi on to indicating con dition and perform a nee, dewlap size could also honestly indicate male boldness in Anolis lizards.

Species longevity in North American fossil mammals

Species longevity in the fossil record is related to many paleoecological variables and is important to macroevo­lutionary studies,yet there are very few reliable data on average species durations in Cenozoic fossil mammals.Many of the online databases(such as the Paleobiology Database)use only genera of North American Cenozoic mammals and there are severe problems because key groups(e.g.camels,oreodonts,pronghorns and probosci­deans)have no reliable updated taxonomy,with many invalid genera and species and/or many undescribed gen­era and species.Most of the published datasets yield species duration estimates of approximately 2.3-4.3 Myr for larger mammals,with small mammals tending to have shorter species durations.My own compilation of all the valid species durations in families with updated taxonomy(39 families,containing 431 genera and 998 species,averaging 2.3 species per genus)yields a mean duration of 3.21 Myr for larger mammals.This breaks down to 4.10-4.39 Myr for artiodactyls,3.14-3.31 Myr for perissodactyls and 2.63-2.95 Myr for carnivorous mammals(carnivorans plus creodonts).These averages are based on a much larger,more robust dataset than most previous estimates,so they should be more reliable for any studies that need species longevity to be accu­rately estimated.

How do small birds evolve in response to climate change?Data from the long-term record at La Brea tar pits

Biology textbooks describe the small changes in the beaks of the Galápagos finches as exemplars of how birds evolve in response to environmental changes.However,recent studies of the abundant fossil birds at Rancho La Brea find no evidence of evolutionary responses to the dramatic climate changes of the glacial–interglacial cycle over the past 35000 years:none of the large birds exhibit any change in body size or limb proportions,even during the last glacial maximum approximately 18000–20000 years ago,when the southern California chaparral was replaced by snowy coniferous forests.However,these are all large birds with large ranges and broad habitat preferences,capable of living in many different environments.Perhaps the smaller birds at La Brea,which have smaller home ranges and narrower habitats,might respond to climate more like Galápagos finches.The only 3 common small birds at La Brea are the western meadowlark,the yellow-billed magpie and the raven.In this study,we demonstrate that these birds also show complete stasis over the last glacial–interglacial cycle,with no statistically significant changes between dated pits.Recent research suggests that the small-scale changes over short timescales seen in the Galápagos finches are merely fluctuations around a stable morphology,and rarely lead to long-term accumulation of changes or speciation.Instead,the prevalence of stasis supports the view that long-term directional changes in morphology are quite rare.While directional changes in morphology occur frequently over short(<1 ka)timescales,in the long term such changes only rarely remain stable for long enough to appear in the fossil record.

A flattened enantiornithine in mid-Cretaceous Burmese amber:morphology and preservation

Cretaceous amber from Myanmar(～99 Ma Burmese amber) has become a valuable supplement to the traditional skeletal record of small theropod dinosaurs preserved in sedimentary rocks, particularly for coelurosaurs and enantiornithines. The specimens recovered from this deposit preserve skeletal material and soft tissues in unmatched detail. This provides opportunities to study three-dimensional preservation of soft tissues, microstructure, and pigmentation patterns that are seldom available elsewhere in the fossil record. Ultimately, this line of research provides insights into life stages that are difficult to preserve, the ecology and appearance of the groups involved, and the evolutionarydevelopment of structures such as feathers. Here we describe the most recent discovery from Burmese amber, an articulated skeleton of an enantiornithine bird. This individual has been sectioned along the coronal plane, providing a unique view inside multiple body regions. Osteological observations and plumage patterns support placement within the Enantiornithes, and suggest that the animal may have been a juvenile at the time of death. The specimen has a complex taphonomic history that includes exposure at the surface of a resin flow prior to encapsulation, and may include scavenging by some of the insects trapped within the same amber piece. The chemical composition observed along surface exposures and shallowly buried regions of the body indicate that the specimen has not undergone significant exchange with its surroundings. High iron concentrations are present in regions that preserve soft tissues as carbon films, and calcium distribution corresponds to regions where bones breach the surface of the amber.

Sexual signal conspicuity is correlated with tail autotomy in an anoline lizard

Sexual selection favors conspicuous signals that animals can use to communicate with conspecifics and/or to attract mates.However,natural and sexual selection are often in opposition,as conspicuous sexual signals can also be detected by eavesdropping predators,forcing these signals to also evolve in light of natural selection(Andersson 1994).