A partial skeleton of an enantiornithine bird from the early Cretaceous of northwestern China

Although recent discoveries from Lower Cretaceous sediments in northeastern China have greatly improved our understanding of the initial stages of avian diversification in eastern Asia, the early evolution of Aves elsewhere on the continent remains poorly understood. In 2004, a collaborative field effort directed by personnel from the Chinese Academy of Geological Sciences and Carnegie Museum of Natural History recovered multiple partial to nearly complete avian skeletons from outcrops of the Lower Cretaceous Xiagou Formation exposed in the Changma Basin of northwestern Gansu Province, China. Here we describe a thrush-sized partial skeleton comprised of a fragmentary pelvic girdle and largely complete hind limbs. A phylogenetic analysis of 20 avian ingroup taxa and 169 anatomical characters places the specimen in Enantiomithes, and within that clade, in Enenantiomithes. When coupled with additional recent discoveries from the Changma Basin, the new skeleton improves our understanding of early avian evolution and diversification in central Asia

Exact ground states for the four-electron problem in a two-dimensional finite Hubbard square system

We present exact explicit analytical results describing the exact ground state of four electrons in a two dimensional square Hubbard cluster containing 16 sites taken with periodic boundary conditions. The presented procedure, which works for arbitrary even particle number and lattice sites, is based on explicitly given symmetry adapted base vectors constructed in r-space. The Hamiltonian acting on these states generates a closed system of 85 linear equations providing by its minimum eigenvalue the exact ground state of the system. The presented results, described with the aim to generate further creative developments, not only show how the ground state can be exactly obtained and what kind of contributions enter in its construction, but emphasize further characteristics of the spectrum. On this line i) possible explications are found regarding why weak coupling expansions often provide a good approximation for the Hubbard model at intermediate couplings, or ii) explicitly given low lying energy states of the kinetic energy, avoiding double occupancy, suggest new roots for pairing mechanism attracting decrease in the kinetic energy, as emphasized by kinetic energy driven superconductivity theories.Comment: 37 pages, 18 figure

Was Dinosaurian Physiology Inherited by Birds? Reconciling Slow Growth in Archaeopteryx

Archaeopteryx is the oldest and most primitive known bird (Avialae). It is believed that the growth and energetic physiology of basalmost birds such as Archaeopteryx were inherited in their entirety from non-avialan dinosaurs. This hypothesis predicts that the long bones in these birds formed using rapidly growing, well-vascularized woven tissue typical of non-avialan dinosaurs. We report that Archaeopteryx long bones are composed of nearly avascular parallel-fibered bone. This is among the slowest growing osseous tissues and is common in ectothermic reptiles. These findings dispute the hypothesis that non-avialan dinosaur growth and physiology were inherited in totality by the first birds. Examining these findings in a phylogenetic context required intensive sampling of outgroup dinosaurs and basalmost birds. Our results demonstrate the presence of a scale-dependent maniraptoran histological continuum that Archaeopteryx and other basalmost birds follow. Growth analysis for Archaeopteryx suggests that these animals showed exponential growth rates like non-avialan dinosaurs, three times slower than living precocial birds, but still within the lowermost range for all endothermic vertebrates. The unexpected histology of Archaeopteryx and other basalmost birds is actually consistent with retention of the phylogenetically earlier paravian dinosaur condition when size is considered. The first birds were simply feathered dinosaurs with respect to growth and energetic physiology. The evolution of the novel pattern in modern forms occurred later in the group's history

Unusually thick dinosaur eggshell fragments from the Spanish Late Cretaceous

[EN] Fieldwork carried out recently in the southeastern branch of the Iberian Range (Valencia Province, Spain) has led to the collection of a large volume of dinosaur eggshell fragments of unusual thickness. These specimens, up to 4.9 mm thick, were recovered from palustrine grey marls of the upper Campanian-lower Maastrichtian Sierra Perenchiza Formation, which comprises a wetland paleoenvironment deposit. These eggshell fragments have a characteristic compactituberculate ornamentation, dinosauroid-spherulitic organisation, and exhibit a complex canaliculate respiratory system. The external tuberculate surface of the shell as well as the internal microstructure enable referral to Megaloolithus aff. siruguei, the most common megaloolithid oospecies known from the Iberian Peninsula and southern France. The biostratigraphic range of M. siruguei matches the temporal distribution of titanosaurid dinosaurs across the Iberian Range, tentatively considered to be potential producers.This work was supported by the Ministerio de Economia y Competitividad of Spain [Secretaria de Estado de Investigacion, Desarrollo e Innovacion, projects CGL2013-47521-P and CGL2014-53548-P]Company Rodríguez, J. (2017). Unusually thick dinosaur eggshell fragments from the Spanish Late Cretaceous. Historical Biology (Online). 31(2):203-210. https://doi.org/10.1080/08912963.2017.1357717S203210312Allain, R., & Suberbiola, X. P. (2003). Dinosaurs of France. Comptes Rendus Palevol, 2(1), 27-44. doi:10.1016/s1631-0683(03)00002-2Bravo, A. M., & Gaete, R. (2014). Titanosaur eggshells from the Tremp Formation (Upper Cretaceous, Southern Pyrenees, Spain). Historical Biology, 27(8), 1079-1089. doi:10.1080/08912963.2014.934231Canudo, J. I., Oms, O., Vila, B., Galobart, À., Fondevilla, V., Puértolas-Pascual, E., … Blanco, A. (2016). The upper Maastrichtian dinosaur fossil record from the southern Pyrenees and its contribution to the topic of the Cretaceous–Palaeogene mass extinction event. Cretaceous Research, 57, 540-551. doi:10.1016/j.cretres.2015.06.013Cruzado-Caballero, P., Ruiz-Omeñaca, J. I., Gaete, R., Riera, V., Oms, O., & Canudo, J. I. (2013). A new hadrosaurid dentary from the latest Maastrichtian of the Pyrenees (north Spain) and the high diversity of the duck-billed dinosaurs of the Ibero-Armorican Realm at the very end of the Cretaceous. Historical Biology, 26(5), 619-630. doi:10.1080/08912963.2013.822867Chiappe, L. M., Coria, R. A., Dingus, L., Jackson, F., Chinsamy, A., & Fox, M. (1998). Sauropod dinosaur embryos from the Late Cretaceous of Patagonia. Nature, 396(6708), 258-261. doi:10.1038/24370Company J. 2004. Vertebrados continentales del Cretácico superior (Campaniense-Maastrichtiense) de Valencia [PhD dissertation]. Valencia: Universidad de Valencia.Company, J., & Szentesi, Z. (2012). Amphibians from the Late Cretaceous Sierra Perenchiza Formation of the Chera Basin, Valencia Province, Spain. Cretaceous Research, 37, 240-245. doi:10.1016/j.cretres.2012.04.003Csiki-Sava, Z., Buffetaut, E., Ősi, A., Pereda-Suberbiola, X., & Brusatte, S. L. (2015). Island life in the Cretaceous - faunal composition, biogeography, evolution, and extinction of land-living vertebrates on the Late Cretaceous European archipelago. ZooKeys, 469, 1-161. doi:10.3897/zookeys.469.8439Erben, H. K., Hoefs, J., & Wedepohl, K. H. (1979). Paleobiological and isotopic studies of eggshells from a declining dinosaur species. Paleobiology, 5(4), 380-414. doi:10.1017/s0094837300016900García, R. A. (2007). An «egg-tooth»–like structure in titanosaurian sauropod embryos. Journal of Vertebrate Paleontology, 27(1), 247-252. doi:10.1671/0272-4634(2007)27[247:aesits]2.0.co;2Garcia, G., & Vianey-Liaud, M. (2001). Dinosaur eggshells as biochronological markers in Upper Cretaceous continental deposits. Palaeogeography, Palaeoclimatology, Palaeoecology, 169(1-2), 153-164. doi:10.1016/s0031-0182(01)00215-2Grellet-Tinner, G., Chiappe, L. M., & Coria, R. (2004). Eggs of titanosaurid sauropods from the Upper Cretaceous of Auca Mahuevo (Argentina). Canadian Journal of Earth Sciences, 41(8), 949-960. doi:10.1139/e04-049Grigorescu, D., Garcia, G., Csiki, Z., Codrea, V., & Bojar, A.-V. (2010). Uppermost Cretaceous megaloolithid eggs from the Haţeg Basin, Romania, associated with hadrosaur hatchlings: Search for explanation. Palaeogeography, Palaeoclimatology, Palaeoecology, 293(3-4), 360-374. doi:10.1016/j.palaeo.2010.03.031Izquierdo LA, Montero D, Pérez G, Urién V, Meijide M. 2001. Macroestructura de huevos de dinosaurios en el Cretácico superior de “La Rosaca” (Burgos, España). Actas de las I Jornadas Internacionales Sobre Paleontología de Dinosaurios y su Entorno. Ed. Colectivo Arqueológico y Paleontológico de Salas. Salas de los Infantes. p. 389–395.Jackson FD. 2007. Titanosaur reproductive biology: comparison of the Auca Mahuevo Titanosaur nesting locality (Argentina), to the Pinyes Megaloolithus nesting locality (Spain) [PhD dissertation]. Bozeman (MT): Montana State University.Jackson, F. D., Garrido, A., Schmitt, J. G., Chiappe, L. M., Dingus, L., & Loope, D. B. (2004). Abnormal, multilayered titanosaur (Dinosauria: Sauropoda) eggs from in situ clutches at the Auca Mahuevo locality, Neuquen Province, Argentina. Journal of Vertebrate Paleontology, 24(4), 913-922. doi:10.1671/0272-4634(2004)024[0913:amtdse]2.0.co;2Jackson, F. D., Varricchio, D. J., Jackson, R. A., Vila, B., & Chiappe, L. M. (2008). Comparison of water vapor conductance in a titanosaur egg from the Upper Cretaceous of Argentina and a Megaloolithus siruguei egg from Spain. Paleobiology, 34(2), 229-246. doi:10.1666/0094-8373(2008)034[0229:cowvci]2.0.co;2López-Martı́nez, N., Moratalla, J. J., & Sanz, J. L. (2000). Dinosaurs nesting on tidal flats. Palaeogeography, Palaeoclimatology, Palaeoecology, 160(1-2), 153-163. doi:10.1016/s0031-0182(00)00063-8Mohabey, D. M. (1998). Systematics of Indian Upper Cretaceous dinosaur and chelonian eggshells. Journal of Vertebrate Paleontology, 18(2), 348-362. doi:10.1080/02724634.1998.10011063Moratalla JJ. 1993. Restos indirectos de dinosaurios del registro español: paleoicnología de la Cuenca de (Jurásico superior-Cretácico inferior) y paleoología del Cretácico superior [PhD dissertation]. Madrid: Universidad Autónoma de Madrid.Moreno-Azanza, M., Bauluz, B., Canudo, J. I., Gasca, J. M., & Torcida Fernández-Baldor, F. (2016). Combined Use of Electron and Light Microscopy Techniques Reveals False Secondary Shell Units in Megaloolithidae Eggshells. PLOS ONE, 11(5), e0153026. doi:10.1371/journal.pone.0153026Moreno-Azanza, M., Bauluz, B., Canudo, J. I., Puértolas-Pascual, E., & Sellés, A. G. (2013). A re-evaluation of aff. Megaloolithidae eggshell fragments from the uppermost Cretaceous of the Pyrenees and implications for crocodylomorph eggshell structure. Historical Biology, 26(2), 195-205. doi:10.1080/08912963.2013.786067Oms, O., Dinarès-Turell, J., Vicens, E., Estrada, R., Vila, B., Galobart, À., & Bravo, A. M. (2007). Integrated stratigraphy from the Vallcebre Basin (southeastern Pyrenees, Spain): New insights on the continental Cretaceous−Tertiary transition in southwest Europe. Palaeogeography, Palaeoclimatology, Palaeoecology, 255(1-2), 35-47. doi:10.1016/j.palaeo.2007.02.039Ortega, F., Bardet, N., Barroso-Barcenilla, F., Callapez, P. M., Cambra-Moo, O., Daviero- Gómez, V., … Sanz, J. L. (2015). The biota of the Upper Cretaceous site of «Lo Hueco» (Cuenca, Spain). Journal of Iberian Geology, 41(1). doi:10.5209/rev_jige.2015.v41.n1.48657Rasskin-Gutman, D., Elez, J., Esteve-Altava, B., & López-Martínez, N. (2020). Reconstruction of the internal structure of the pore system of a complex dinosaur eggshell (Megaloolithus siruguei). Spanish Journal of Palaeontology, 28(1), 61. doi:10.7203/sjp.28.1.17831Riera, V., Oms, O., Gaete, R., & Galobart, À. (2009). The end-Cretaceous dinosaur succession in Europe: The Tremp Basin record (Spain). Palaeogeography, Palaeoclimatology, Palaeoecology, 283(3-4), 160-171. doi:10.1016/j.palaeo.2009.09.018Sellés, A. G., Bravo, A. M., Delclòs, X., Colombo, F., Martí, X., Ortega-Blanco, J., … Galobart, À. (2013). Dinosaur eggs in the Upper Cretaceous of the Coll de Nargó area, Lleida Province, south-central Pyrenees, Spain: Oodiversity, biostratigraphy and their implications. Cretaceous Research, 40, 10-20. doi:10.1016/j.cretres.2012.05.004Tanaka, K., & Zelenitsky, D. K. (2014). Comparisons between experimental and morphometric water vapor conductance in the eggs of extant birds and crocodiles: implications for predicting nest type in dinosaurs. Canadian Journal of Zoology, 92(12), 1049-1058. doi:10.1139/cjz-2014-0078Vianey-Liaud, M., Khosla, A., & Garcia, G. (2003). Relationships between European and Indian dinosaur eggs and eggshells of the oofamily Megaloolithidae. Journal of Vertebrate Paleontology, 23(3), 575-585. doi:10.1671/0272-4634(2003)023[0575:rbeaid]2.0.co;2Vianey-Liaud, M., & Lopez-Martinez, N. (1997). Late Cretaceous dinosaur eggshells from the Tremp Basin, southern Pyrenees, Lleida, Spain. Journal of Paleontology, 71(6), 1157-1171. doi:10.1017/s002233600003609xVila, B., Galobart, À., Canudo, J. I., Le Loeuff, J., Dinarès-Turell, J., Riera, V., … Gaete, R. (2012). The diversity of sauropod dinosaurs and their first taxonomic succession from the latest Cretaceous of southwestern Europe: Clues to demise and extinction. Palaeogeography, Palaeoclimatology, Palaeoecology, 350-352, 19-38. doi:10.1016/j.palaeo.2012.06.008(2010). Lethaia, 43(2). doi:10.1111/let.2010.43.issue-2Vila, B., Jackson, F. D., Fortuny, J., Sellés, A. G., & Galobart, À. (2010). 3-D Modelling of Megaloolithid Clutches: Insights about Nest Construction and Dinosaur Behaviour. PLoS ONE, 5(5), e10362. doi:10.1371/journal.pone.0010362Vila, B., Riera, V., Bravo, A. M., Oms, O., Vicens, E., Estrada, R., & Galobart, À. (2011). The chronology of dinosaur oospecies in south-western Europe: Refinements from the Maastrichtian succession of the eastern Pyrenees. Cretaceous Research, 32(3), 378-386. doi:10.1016/j.cretres.2011.01.009Vila, B., Sellés, A. G., & Brusatte, S. L. (2016). Diversity and faunal changes in the latest Cretaceous dinosaur communities of southwestern Europe. Cretaceous Research, 57, 552-564. doi:10.1016/j.cretres.2015.07.003Vissers, R. L. M., & Meijer, P. T. (2012). Iberian plate kinematics and Alpine collision in the Pyrenees. Earth-Science Reviews, 114(1-2), 61-83. doi:10.1016/j.earscirev.2012.05.001Wright, V. P., & Platt, N. H. (1995). Seasonal wetland carbonate sequences and dynamic catenas: a re-appraisal of palustrine limestones. Sedimentary Geology, 99(2), 65-71. doi:10.1016/0037-0738(95)00080-

Functional Morphometric Analysis of the Furcula in Mesozoic Birds

The furcula displays enormous morphological and structural diversity. Acting as an important origin for flight muscles involved in the downstroke, the form of this element has been shown to vary with flight mode. This study seeks to clarify the strength of this form-function relationship through the use of eigenshape morphometric analysis coupled with recently developed phylogenetic comparative methods (PCMs), including phylogenetic Flexible Discriminant Analysis (pFDA). Additionally, the morphospace derived from the furculae of extant birds is used to shed light on possible flight adaptations of Mesozoic fossil taxa. While broad conclusions of earlier work are supported (U-shaped furculae are associated with soaring, strong anteroposterior curvature with wing-propelled diving), correlations between form and function do not appear to be so clear-cut, likely due to the significantly larger dataset and wider spectrum of flight modes sampled here. Interclavicular angle is an even more powerful discriminator of flight mode than curvature, and is positively correlated with body size. With the exception of the close relatives of modern birds, the ornithuromorphs, Mesozoic taxa tend to occupy unique regions of morphospace, and thus may have either evolved unfamiliar flight styles or have arrived at similar styles through divergent musculoskeletal configurations

A teleofunctional account of evolutionary mismatch.

This is the final version of the article. It first appeared from Springer via http://dx.doi.org/10.1007/s10539-016-9527-1When the environment in which an organism lives deviates in some essential way from that to which it is adapted, this is described as "evolutionary mismatch," or "evolutionary novelty." The notion of mismatch plays an important role, explicitly or implicitly, in evolution-informed cognitive psychology, clinical psychology, and medicine. The evolutionary novelty of our contemporary environment is thought to have significant implications for our health and well-being. However, scientists have generally been working without a clear definition of mismatch. This paper defines mismatch as deviations in the environment that render biological traits unable, or impaired in their ability, to produce their selected effects (i.e., to perform their proper functions in Neander's sense). The machinery developed by Millikan in connection with her account of proper function, and with her related teleosemantic account of representation, is used to identify four major types, and several subtypes, of evolutionary mismatch. While the taxonomy offered here does not in itself resolve any scientific debates, the hope is that it can be used to better formulate empirical hypotheses concerning the effects of mismatch. To illustrate, it is used to show that the controversial hypothesis that general intelligence evolved as an adaptation to handle evolutionary novelty can, contra some critics, be formulated in a conceptually coherent way

Cellular preservation of musculoskeletal specializations in the Cretaceous bird Confuciusornis

The hindlimb of theropod dinosaurs changed appreciably in the lineage leading to extant birds, becoming more ‘crouched’ in association with changes to body shape and gait dynamics. This postural evolution included anatomical changes of the foot and ankle, altering the moment arms and control of the muscles that manipulated the tarsometatarsus and digits, but the timing of these changes is unknown. Here, we report cellular-level preservation of tendon- and cartilage-like tissues from the lower hindlimb of Early Cretaceous Confuciusornis. The digital flexor tendons passed through cartilages, cartilaginous cristae and ridges on the plantar side of the distal tibiotarsus and proximal tarsometatarsus, as in extant birds. In particular, fibrocartilaginous and cartilaginous structures on the plantar surface of the ankle joint of Confuciusornis may indicate a more crouched hindlimb posture. Recognition of these specialized soft tissues in Confuciusornis is enabled by our combination of imaging and chemical analyses applied to an exceptionally preserved fossil

A basal lithostrotian titanosaur (Dinosauria: Sauropoda) with a complete skull: Implications for the evolution and paleobiology of titanosauria

We describe Sarmientosaurus musacchioi gen. et sp. nov., a titanosaurian sauropod dinosaur from the Upper Cretaceous (Cenomanian - Turonian) Lower Member of the Bajo Barreal Formation of southern Chubut Province in central Patagonia, Argentina. The holotypic and only known specimen consists of an articulated, virtually complete skull and part of the cranial and middle cervical series. Sarmientosaurus exhibits the following distinctive features that we interpret as autapomorphies: (1) maximum diameter of orbit nearly 40% rostrocaudal length of cranium; (2) complex maxilla - lacrimal articulation, in which the lacrimal clasps the ascending ramus of the maxilla; (3) medial edge of caudal sector of maxillary ascending ramus bordering bony nasal aperture with low but distinct ridge; (4) ´tongue-like´ ventral process of quadratojugal that overlaps quadrate caudally; (5) separate foramina for all three branches of the trigeminal nerve; (6) absence of median venous canal connecting infundibular region to ventral part of brainstem; (7) subvertical premaxillary, procumbent maxillary, and recumbent dentary teeth; (8) cervical vertebrae with ´strut-like´ centroprezygapophyseal laminae; (9) extremely elongate and slender ossified tendon positioned ventrolateral to cervical vertebrae and ribs. The cranial endocast of Sarmientosaurus preserves some of the most complete information obtained to date regarding the brain and sensory systems of sauropods. Phylogenetic analysis recovers the new taxon as a basal member of Lithostrotia, as the most plesiomorphic titanosaurian to be preserved with a complete skull. Sarmientosaurus provides a wealth of new cranial evidence that reaffirms the close relationship of titanosaurs to Brachiosauridae. Moreover, the presence of the relatively derived lithostrotian Tapuiasaurus in Aptian deposits indicates that the new Patagonian genus represents a ´ghost lineage´ with a comparatively plesiomorphic craniodental form, the evolutionary history of which is missing for at least 13 million years of the Cretaceous. The skull anatomy of Sarmientosaurus suggests that multiple titanosaurian species with dissimilar cranial structures coexisted in the early Late Cretaceous of southern South America. Furthermore, the new taxon possesses a number of distinctive morphologies - such as the ossified cervical tendon, extremely pneumatized cervical vertebrae, and a habitually downward- facing snout - that have rarely, if ever, been documented in other titanosaurs, thus broadening our understanding of the anatomical diversity of this remarkable sauropod clade. The latter two features were convergently acquired by at least one penecontemporaneous diplodocoid, and may represent mutual specializations for consuming low-growing vegetation.Fil: Martínez, Rubén Darío. Universidad Nacional de la Patagonia; ArgentinaFil: Lamanna, Matthew C.. Carnegie Museum Of Natural History; Estados UnidosFil: Novas, Fernando Emilio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "bernardino Rivadavia"; ArgentinaFil: Ridgely, Ryan C.. Ohio University College Of Osteopathic Medicine; Estados UnidosFil: Casal, Gabriel. Universidad Nacional de la Patagonia; ArgentinaFil: Martínez, Javier E.. Hospital Regional de Comodoro Rivadavia; ArgentinaFil: Vita, Javier R.. Resonancia Magnética Borelli; ArgentinaFil: Witmer, Lawrence M.. Ohio University College Of Osteopathic Medicine; Estados Unido

Convergent Evolution in Aquatic Tetrapods: Insights from an Exceptional Fossil Mosasaur

Mosasaurs (family Mosasauridae) are a diverse group of secondarily aquatic lizards that radiated into marine environments during the Late Cretaceous (98–65 million years ago). For the most part, they have been considered to be simple anguilliform swimmers – i.e., their propulsive force was generated by means of lateral undulations incorporating the greater part of the body – with unremarkable, dorsoventrally narrow tails and long, lizard-like bodies. Convergence with the specialized fusiform body shape and inferred carangiform locomotory style (in which only a portion of the posterior body participates in the thrust-producing flexure) of ichthyosaurs and metriorhynchid crocodyliform reptiles, along with cetaceans, has so far only been recognized in Plotosaurus, the most highly derived member of the Mosasauridae. Here we report on an exceptionally complete specimen (LACM 128319) of the moderately derived genus Platecarpus that preserves soft tissues and anatomical details (e.g., large portions of integument, a partial body outline, putative skin color markings, a downturned tail, branching bronchial tubes, and probable visceral traces) to an extent that has never been seen previously in any mosasaur. Our study demonstrates that a streamlined body plan and crescent-shaped caudal fin were already well established in Platecarpus, a taxon that preceded Plotosaurus by 20 million years. These new data expand our understanding of convergent evolution among marine reptiles, and provide insights into their evolution's tempo and mode