A Cretaceous hoofed mammal from India

The sedimentary record documenting the northward drift of India (Late Cretaceous to late Early Eocene) has recently provided important clues to the evolution, radiation, and dispersal of mammals. Here, we report a definitive Late Cretaceous (Maastrichtian) archaic ungulate (Kharmerungulatum vanvaleni genus et species nova) from the Deccan volcano-sedimentary sequences exposed near Kisalpuri village in Central India. This find has important implications for the origin and diversification of early ungulates and raises three possible paleobiogeographic scenarios: (i) Archaic ungulates may have been cosmopolitan in distribution. (ii) Kharmerungulatum might be an immigrant from Western Asia. (iii) Archaic ungulates may have originated in India.     

An aegialodontid upper molar and the evolution of mammal dentition

The most obvious key synapomorphy of the therian mammals is the tribosphenic pattern of their molars. Tribosphenic teeth are capable of both shearing and grinding, which substantially increase effectiveness of food processing and, in turn, permit evolution of a wide range of dietary specializations. Functional tribospheny developed repeatedly during mammalian evolution but was successful only in the Boreosphenida. The earliest stage in the development of boreosphenidan tribospheny has remained poorly understood, being documented only by lower molars of aegialodontids. Here, we report a known upper molar of an aegialodontid mammal, Kielantherium, from the Early Cretaceous of Mongolia.     

Early Cretaceous spider web with its prey

The orb web is a spectacular evolutionary innovation that enables spiders to catch flying prey. This elegant, geometric structure is woven with silk fibers that are renowned for their superior mechanical properties. We used silk gland expression libraries to address a long-standing controversy concerning the evolution of the orb-web architecture. Contrary to the view that the orb-web design evolved multiple times, we found that the distribution and phylogeny of silk proteins support a single, ancient origin of the orb web at least 136 million years ago. Furthermore, we substantially expanded the repository of silk sequences that can be used for the synthesis of high-performance biomaterials.     

True Polar Wander since the Early Cretaceous

The motions of the lithospheric plates have been reconstructed for three time intervals back to the Early Cretaceous. These displacements were analyzed to determine the best-fitting rigid rotation, which could then be ascribed to true polar wander. The true polar wander so obtained is no larger than a few degrees and is within the magnitude of the uncertainties involved.     

Comment on "Impacts of the Cretaceous Terrestrial Revolution and KPg extinction on mammal diversification"

Meredith et al. (Reports, 28 October 2011, p. 521) question three findings of our delayed-rise hypothesis for present-day mammals made with reference to the Cretaceous-Paleogene (KPg) boundary, based on their new time tree of the group. We show that their own data do not support their objections and that the macroevolutionary patterns from the respective phylogenies are not statistically different.     

A fossil bee from Early Cretaceous Burmese amber

The bee fossil record is fragmentary, making it difficult to accurately estimate the antiquity of bee-mediated pollination. Here, we describe a bee fossil [Melittosphex burmensis (new species), Melittosphecidae (new family)] from Early Cretaceous Burmese amber (approximately 100 million years before the present). The fossil provides insights into the morphology of the earliest bees and provides a new minimum date for the antiquity of bees and bee-mediated pollination.     

Cretaceous sauropods from the sahara and the uneven rate of skeletal evolution among dinosaurs

Lower Cretaceous fossils from central Niger document the succession of sauropod dinosaurs on Africa as it drifted into geographic isolation. A new broad-toothed genus of Neocomian age ( approximately 135 million years ago) shows few of the specializations of other Cretaceous sauropods. A new small-bodied sauropod of Aptian-Albian age ( approximately 110 million years ago), in contrast, reveals the highly modified cranial form of rebbachisaurid diplodocoids. Rates of skeletal change in sauropods and other major groups of dinosaurs are estimated quantitatively and shown to be highly variable.     

A nearly modern amphibious bird from the Early Cretaceous of northwestern China

Three-dimensional specimens of the volant fossil bird Gansus yumenensis from the Early Cretaceous Xiagou Formation of northwestern China demonstrate that this taxon possesses advanced anatomical features previously known only in Late Cretaceous and Cenozoic ornithuran birds. Phylogenetic analysis recovers Gansus within the Ornithurae, making it the oldest known member of the clade. The Xiagou Formation preserves the oldest known ornithuromorph-dominated avian assemblage. The anatomy of Gansus, like that of other non-neornithean (nonmodern) ornithuran birds, indicates specialization for an amphibious life-style, supporting the hypothesis that modern birds originated in aquatic or littoral niches.     

Early chemical evolution of nucleic acids: a theoretical model

Recent experimental work suggests a possible cyclical pathway for early prebiotic oligonucleotide formation that involves (i) dry-state (nontemplate) synthesis of random copolymers with mixed 2',5' and 3',5' bonds, (ii) passage of these oligomers into solution at low temperatures, and (iii) a preferential hydrolysis of the 2',5' bond in any short helices that have formed. This early system could have selected for complementary sequences that were largely 3',5'-linked, but may not have selected efficiently for a single enantiomer of ribose.     

An ossified Meckel's cartilage in two Cretaceous mammals and origin of the mammalian middle ear

An ossified Meckel's cartilage has been recovered from two early Cretaceous mammals from China. This element is similar to Meckel's cartilage in prenatal and some postnatal extant mammals and indicates the relationship of Meckel's cartilage with the middle ear in early mammals. The evidence shows that brain expansion may not be the initial factor that caused the separation of postdentary bones from the dentary as middle ear ossicles during mammalian evolution. The failure of the dentary to seize reduced postdentary elements during ontogeny of early mammals is postulated as an alternative mechanism for the separation. Modifications of both feeding and hearing apparatuses in early mammals may have led to the development of the definitive mammalian middle ear.     

A Late Jurassic digging mammal and early mammalian diversification

A fossil mammal from the Late Jurassic Morrison Formation, Colorado, has highly specialized teeth similar to those of xenarthran and tubulidentate placental mammals and different from the generalized insectivorous or omnivorous dentitions of other Jurassic mammals. It has many forelimb features specialized for digging, and its lumbar vertebrae show xenarthrous articulations. Parsimony analysis suggests that this fossil represents a separate basal mammalian lineage with some dental and vertebral convergences to those of modern xenarthran placentals, and reveals a previously unknown ecomorph of early mammals.     

Middle and late eocene mammal communities: a major discrepancy

The multituberculate Parectypodus lovei has been found in late Eocene rocks in Montana, together with 11 other mammal species similar to those found in the late Eocene Tepee Trail Formation in Wyoming.The multituberculate and six other species are unknown in rocks of equivalent age or of middle Eocene age elsewhere.It is suggested that the known middle Eocene faunas are all taken from a similar ecological situation and do not reflect the true diversity of middle Eocene life. Middle Eocene faunas of different ecological aspect may be recovered from sediments along, and in, the mountain fronts of northwestern Wyoming.     

内蒙黑猪仔猪早期断奶适龄的探讨

本课题研究的目的就是找出内蒙古地区仔猪早期断奶的适宜断奶日龄，为养猪生产提供科学的依据。为此，我们做了内蒙黑猪哺乳仔猪生后２１、３５、４５不同日龄断奶试验，从中寻找规律，确定适合内蒙古地区的仔猪早期断奶日龄。经６０ｄ试验，我们测定了一系列数据。通过对试验结果分析看出：３５日龄断奶组的仔猪增重快，生长发育迅速，到６０日龄时的体重显著地高于２１日龄组和４５日龄组的体重，经方差分析差异显著（０．０１＜ｐ＜０．０５）；３５日龄断奶组仔猪成活率最高为９０．２４％，３５日龄断奶组母猪年产胎数也较多，从而增加了母猪年产活仔数；３５日龄断奶组还明显地降低了饲养成本，经济效益高。通过试验，作者认为：在内蒙古地区一般饲养管理条件下，仔猪３５日龄早期断奶最适宜，并可在生产中推广应用。     

Climbing adaptations in the early eocene mammal Chriacus and the origin of artiodactyla

A virtually complete articulated skeleton of the arctocyonid Chriacus, recently found in northern Wyoming, is one of the most intact early Eocene mammal skeletons ever found. It exhibits numerous adaptations characteristic of mammals that climb, including strong bony crests and processes (reflecting powerful musculature), ability for considerable forearm supination, a highly mobile ankle joint, plantigrade feet, curved and transversely compressed claws, and a long, possibly semiprehensile tail. These features contrast sharply with those of the oldest artiodactyls and indicate that Chriacus or a similar arctocyonid was not ancestral to the Artiodactyla, as has been proposed.     

Predatory Dinosaurs from the Sahara and Late Cretaceous Faunal Differentiation

Late Cretaceous (Cenomanian) fossils discovered in the Kem Kem region of Morocco include large predatory dinosaurs that inhabited Africa as it drifted into geographic isolation. One, represented by a skull approximately 1.6 meters in length, is an advanced allosauroid referable to the African genus Carcharodontosaurus. Another, represented by a partial skeleton with slender proportions, is a new basal coelurosaur closely resembling the Egyptian genus Bahariasaurus. Comparisons with Cretaceous theropods from other continents reveal a previously unrecognized global radiation of carcharodontosaurid predators. Substantial geographic differentiation of dinosaurian faunas in response to continental drift appears to have arisen abruptly at the beginning of the Late Cretaceous.