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[dinosaur] Echidna forelimbs + dinosaur nesting + evolution of iridescent feathers + more

Ben Creisler

Some recent non-dino papers:

Free pdf:

Sophie Regnault &Â Stephanie E. Pierce (2018)
Pectoral girdle and forelimb musculoskeletal function in the echidna (Tachyglossus aculeatus): insights into mammalian locomotor evolution.
Royal Society Open Science 5: 181400.
DOI: 10.1098/rsos.181400

Although evolutionary transformation of the pectoral girdle and forelimb appears to have had a profound impact on mammalian locomotor and ecological diversity, both the sequence of anatomical changes and the functional implications remain unclear. Monotremes can provide insight into an important stage of this evolutionary transformation, due to their phylogenetic position as the sister-group to therian mammals and their mosaic of plesiomorphic and derived features. Here we build a musculoskeletal computer model of the echidna pectoral girdle and forelimb to estimate joint ranges of motion (ROM) and muscle moment arms (MMA)âtwo fundamental descriptors of biomechanical function. We find that the echidna's skeletal morphology restricts scapulocoracoid mobility and glenohumeral flexionâextension compared with therians. Estimated shoulder ROMs and MMAs for muscles crossing the shoulder indicate that morphology of the echidna pectoral girdle and forelimb is optimized for humeral adduction and internal rotation, consistent with limited in vivo data. Further, more muscles act to produce humeral long-axis rotation in the echidna compared to therians, as a consequence of differences in muscle geometry. Our musculoskeletal model allows correlation of anatomy and function, and can guide hypotheses regarding function in extinct taxa and the morphological and locomotor transformation leading to therian mammals.


Kohei TANAKA, Darla K. ZELENITSKY, FranÃois THERRIEN & Yoshitsugu KOBAYASHI (2018)Â
Transition in Nesting Methods and Behaviors from Non-Avian Dinosaurs to Birds.Â
Japanese Journal of Ornithology 67(1): 25-40

Archosaurs (e.g., crocodilians, pterosaurs, and dinosaurs including birds) are the most diverse and successful clade of terrestrial vertebrates. An understanding of the nesting methods and behaviors of both extinct (e.g., non-avian dinosaurs) and extant archosaurs (i.e., crocodilians and birds) is crucial for the advancement of our understanding of the evolution and diversification of this clade. The nesting methods and behavior of extinct taxa cannot be directly observed from the fossil record, thus aspects of nesting (i.e., nest type, incubation behavior, and incubation period) may only be inferred and reconstructed based on certain features of fossil eggs, nests, and embryos (e.g., clutch size, egg mass, eggshell porosity, and embryonic osteology). Nests and nesting behaviors were likely to have been diverse among non-avian dinosaurs, and the evolution of these features in archosaurs is discussed.


Klara K. NordÃn, Jaeike Faber, Frane BabaroviÄ, Thomas L. Stubbs, Tara Selly, James D. Schiffbauer, Petra Peharec ÅtefaniÄ, Gerald Mayr, Fiann Smithwick & Jakob Vinther (2018)
Melanosome diversity and convergence in the evolution of iridescent avian feathers--implications for paleocolor reconstruction.
Evolution (advance online publication)

Some of the most varied colors in the natural world are created by iridescent nanostructures in bird feathers, formed by layers of melaninâcontaining melanosomes. The morphology of melanosomes in iridescent feathers is known to vary, but the extent of this diversity, and when it evolved, is unknown. We use scanning electron microscopy to quantify the diversity of melanosome morphology in iridescent feathers from 97 extant bird species, covering 11 orders. In addition, we assess melanosome morphology in two Eocene birds, which are the stem lineages of groups that respectively exhibit hollow and flat melanosomes today. We find that iridescent feathers contain the most varied melanosome morphologies of all types of bird coloration sampled to date. Using our extended dataset, we predict iridescence in an early Eocene trogon (cf. Primotrogon) but not in the early Eocene swift Scaniacypselus, and neither exhibit the derived melanosome morphologies seen in their modern relatives. Our findings confirm that iridescence is a labile trait that has evolved convergently in several lineages extending down to paravian theropods. The dataset provides a framework to detect iridescence with more confidence in fossil taxa based on melanosome morphology.


Chase T. Kinsey & Lance D. McBrayer (2018)
Forelimb position affects facultative bipedal locomotion in lizards.
Journal of Experimental Biology : jeb.185975Â
doi: 10.1242/jeb.185975Â

Recent work indicates that bipedal posture in lizards is advantageous during obstacle negotiation (Parker and McBrayer, 2016). However, little is known about how bipedalism occurs beyond a lizard's acceleratory threshold. Furthermore, no study to date has examined the effects of forelimb position on the body center of mass in the context of bipedalism. This study quantified the frequency of bipedalism when sprinting with vs. without an obstacle at 0.8 meters from initiating a sprint. Forelimb positions were quantified during bipedal running at the start of a sprint and when crossing an obstacle. Two species with contrasting body forms (and thus different body center of mass; BCoM) were studied (Sceloporus woodi, Aspidoscelis sexlineata) to assess potential variation due to body plan and obstacle crossing behavior. No significant difference in frequency of bipedalism was observed in S. woodi with or without an obstacle. However, A. sexlineata primarily used a bipedal posture when sprinting. Forelimb positions were variable in S. woodi and stereotyped in A. sexlineata. Caudal extension of the forelimbs helped shift the BCoM posteriorly and transition to, or maintain, a bipedal posture in A. sexlineata, but not S. woodi. The posterior shift in BCoM, aided by more caudally placed forelimbs, helps raise the trunk from the ground, regardless of obstacle presence. The body plan, specifically the length of the trunk and tail, and forelimb position work together with acceleration to shift the BCoM posteriorly to transition to a bipedal posture. Thus, species exhibit morphological and behavioral adjustments to transition to and maintain facultative bipedalism while sprinting.


Free pdf:

XI Dangpeng, WAN Xiaoqiao, LI Guobiao & LI Gang (2018)
Cretaceous integrative stratigraphy and timescale of China.ÂÂ
SCIENCE CHINA Earth Sciences (advance online publication)
doi: 10.1007/s11430-017-9262-yÂ

Cretaceous strata are widely distributed across China and record a variety of depositional settings. The sedimentary facies consist primarily of terrestrial, marine and interbedded marine-terrestrial deposits, of which marine and interbedded facies are relatively limited. Based a thorough review of the subdivisions and correlations of Cretaceous strata in China, we provide an up-to-date integrated chronostratigraphy and geochronologic framework of the Cretaceous system and its deposits in China. Cretaceous marine and interbedded marine-terrestrial sediments occur in southern Tibet, Karakorum, the western Tarim Basin, eastern Heilongjiang and Taiwan. Among these, the Himalayan area has the most complete marine deposits, the foraminiferal and ammonite biozonation of which can be correlated directly to the international standard biozones. Terrestrial deposits in central and western China consist predominantly of red, lacustrine-fluvial, clastic deposits, whereas eastern China, a volcanically active zone, contains clastic rocks in association with intermediate to acidic igneous rocks and features the most complete stratigraphic successions in northern Hebei, western Liaoning and the Songliao Basin. Here, we synthesise multiple stratigraphic concepts and charts from southern Tibet, northern Hebei to western Liaoning and the Songliao Basin to produce a comprehensive chronostratigraphic chart. Marine and terrestrial deposits are integrated, and this aids in the establishment of a comprehensive Cretaceous chronostratigraphy and temporal framework of China. Further research into the Cretaceous of China will likely focus on terrestrial deposits and mutual authentication techniques (e.g., biostratigraphy, chronostratigraphy, magnetostratigraphy and cyclostratigraphy). This study provides a more reliable temporal framework both for studying Cretaceous geological events and exploring mineral resources in China.


Free pdf:

HUANG Diying (2018)
Jurassic integrative stratigraphy and timescale of China.
SCIENCE CHINA Earth Sciences (advance online publication)
doi: 10.1007/s11430-017-9268-7Â

The Jurassic stratigraphy in China is dominated by continental sediments. Marine facies and marine-terrigenous facies sediment have developed locally in the Qinghai-Tibet area, southern South China, and northeast China. The division of terrestrial Jurassic strata has been argued, and the conclusions of biostratigraphy and isotope chronology have been inconsistent. During the Jurassic period, the North China Plate, South China Plate, and Tarim Plate were spliced and formed the prototype of ancient China. The Yanshan Movement has had a profound influence on the eastern and northern regions of China and has formed an important regional unconformity. The Triassic-Jurassic boundary (201.3 Ma) is located roughly between the Haojiagou Formation and the Badaowan Formation in the Junggar Basin, and between the Xujiahe Formation and the Ziliujing Formation in the Sichuan Basin. The early Early Jurassic sediments generally were lacking in the eastern and central regions north of the ancient Dabie Mountains, suggesting that a clear uplift occurred in the eastern part of China during the Late Triassic period when it formed vast mountains and plateaus. A series of molasse-volcanic rock-coal strata developed in the northern margin of North China Craton in the Early Jurassic and are found in the Xingshikou Formation, Nandailing Formation, and Yaopo Formation in the West Beijing Basin. The geological age and markers of the boundary between the Yongfeng Stage and Liuhuanggou Stage are unclear. About 170 Ma ago, the Yanshan Movement began to affect China. The structural system of China changed from the near east-west Tethys or the Ancient Asia Ocean tectonic domain to the north-north-east Pacific tectonic domain since 170â135 Ma. A set of syngenetic conglomerate at the bottom of the Haifanggou or Longmen Fms. represented another set of molasse-volcanic rock-coal strata formed in the Yanliao region during the Middle Jurassic Yanshan Movement (Curtain A1). The bottom of the conglomerate is approximately equivalent to the boundary of the Shihezi Stage and Liuhuanggou Stage. The bottom of the Manas Stage creates a regional unconformity in northern China (about 161 Ma, Volcanic Curtain of the Yanshan Movement, Curtain A2). The Jurassic Yanshan Movement is likely related to the southward subduction of the Siberian Plate to the closure of the Mongolia-Okhotsk Ocean. A large-scale volcanic activity occurred in the Tiaojishan period around 161â153 Ma. Note that 153 Ma is the age of the bottom Tuchengzi Formation, and the bottom boundary of the Fifth Stage of the Jurassic terrestrial stage in China should have occurred earlier than this. This activity was marked by a warming event at the top of the Toutunhe Formation, and the change in the biological assembly is estimated to be 155 Ma. The terrestrial Jurassic-Cretaceous boundary (ca. 145.0 Ma) in the Yanliao region should be located in the upper part of Member 1 of the Tuchengzi Formation, the Ordos Basin in the upper part of the Anding Formation, the Junggar Basin in the upper part of the Qigu Formation, and the Sichuan Basin in the upper part of the Suining Formation The general characteristics of terrestrial Jurassic of China changed from the warm and humid coal-forming environment of the Early-Middle Jurassic to the hot, dry, red layers in the Late Jurassic. With the origin and development of the Coniopteris-Phoenicopsis flora, the Yanliao biota was developed and spread widely in the area north of the ancient Kunlun Mountains, ancient Qinling Mountains, and ancient Dabie Mountain ranges in the Middle Jurassic, and reached its great prosperity in the Early Late Jurassic and gradually declined and disappeared and moved southward with the arrival of a dry and hot climate.


Karol JewuÅa, MichaÅ Matysik, Mariusz Paszkowski & JoachimSzulc (2018)
The late Triassic development of playa, gilgai floodplain, and fluvial environments from Upper Silesia, southern Poland.
Sedimentary Geology (advance online publication)


Carnian-Norian terrestrial deposits from SE Germanic Basin represent playa and gilgai-type floodplain environments.

The evolution of gilgai environments was mainly controlled by climatic changes through Late Triassic.

Gravel analysis indicates San River and Moesian platform sources.

Palaeosol type and geochemistry indicate climatic seasonality with precipitation at 720âmm/yr.


The numerous discoveries of disintegrated skeletons of large terrestrial vertebrates within several thin levels of the Upper Silesian Keuper initiated broad investigations into the palaeoenvironment and age of the bone-bearing sediments. Despite years of research, the depositional history of the Upper Triassic continental succession and its controlling factors are still poorly recognized. This paper reconstructs the depositional evolution of the Upper Triassic strata in Upper Silesia, Poland, discusses the tectonic and climatic control on deposition, and identifies the sediment provenance. Detailed sedimentological analysis enabled the recognition of three major palaeoenvironments: (1) playa; (2) distal floodplain featured by gilgai micromorphology; (3) fluvial system (sand-dominated meandering, sand- and gravel-dominated braided, and potentially anastomosing river system). The transition from one palaeoenvironment into another reflects climatic changes throughout the late Triassic. The Carnian interval is dominated by gypsum-rich playa mudstones deposited under hot and arid conditions, with only one wet episode recorded as meandering river sandstones (the so-called Carnian Pluvial Event). In contrast, Norian sedimentation was controlled by strong seasonal climatic variations, which is reflected in alternating palaeosol horizons (vertisols and calcisols), thin claystone beds (small water-pond deposits), and conglomerates (rapid flood events). This facies assemblage was formed in a relatively stable floodplain which became the main habitat of numerous vertebrate organisms. The Rhaetian is represented by a gravel-dominated braided river system developed in response to significant climate humidification, with tectonic controls on flow direction. Clast types from Norian and Rhaetian conglomerates revealed that the studied area was fed from the south and south west by the San River and Moesian Massifs. Geochemical analysis of Norian palaeosol horizons suggests mean annual precipitation of ~ 720âmm/yr in agreement with the palaeoclimatic reconstructions for the area, pointing to seasonal sub-humid to semi-arid climate conditions.

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