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RE: Dinosaur news - Ngala - 09-08-2016
A new species of compsognathid from the Early Cretaceous Yixian Formation of western Liaoning, China
Beipiaognathus jii Hu, Wang & Huang, 2016
*This image is copyright of its original author
"The paper reports a new genus and species of compsognathids: Beipiaognathus jii( gen. et sp. nov.). It possesses not only the diagnostic characters of Compsognathidae,such as the fan-shaped dorsal neural spines and robust phalanx Ⅰ-1,but also some unique characteristics different from other compsognathids,including the un-serrated conical-shaped teeth,relatively long ulna,robust and long phalanx Ⅱ-1,and relatively short tail. The discovery further reveals the great diversity of Compsognathidae and provides more information for understanding the anatomical characters of compsognathids."
RE: Dinosaur news - Ngala - 09-10-2016
A new rauisuchid (Archosauria, Pseudosuchia) from the Upper Triassic (Norian) of New Mexico increases the diversity and temporal range of the clade
Vivaron haydeni Lessner et al, 2016
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Artist's rendering of a Vivaron haydeni that lived more than 200 million years ago. Image by Matt Celeskey.
Abstract:
"Rauisuchids are large (2–6 m in length), carnivorous, and quadrupedal pseudosuchian archosaurs closely related to crocodylomorphs. Though geographically widespread, fossils of this clade are relatively rare in Late Triassic assemblages. The middle Norian (∼212 Ma) Hayden Quarry of northern New Mexico, USA, in the Petrified Forest Member of the Chinle Formation, has yielded isolated postcranial elements and associated skull elements of a new species of rauisuchid. Vivaron haydeni gen. et. sp. nov. is diagnosed by the presence of two posteriorly directed prongs at the posterior end of the maxilla for articulation with the jugal. The holotype maxilla and referred elements are similar to those of the rauisuchid Postosuchus kirkpatricki from the southwestern United States, but V. haydeni shares several maxillary apomorphies (e.g., a distinct dropoff to the antorbital fossa that is not a ridge, a straight ventral margin, and a well defined dental groove) with the rauisuchid Teratosaurus suevicus from the Norian of Germany. Despite their geographic separation, this morphological evidence implies a close phylogenetic relationship between V. haydeni and T. suevicus. The morphology preserved in the new Hayden Quarry rauisuchid V. haydeni supports previously proposed and new synapomorphies for nodes within Rauisuchidae. The discovery of Vivaron haydeni reveals an increased range of morphological disparity for rauisuchids from the low-paleolatitude Chinle Formation and a clear biogeographic connection with high paleolatitude Pangea."
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Undergraduate researcher leads study naming a new species of reptile from 212 million years ago
RE: Dinosaur news - Ngala - 09-24-2016
The first iguanian lizard from the Mesozoic of Africa
Jeddaherdan aleadonta Apesteguía, Daza, Simões & Rage, 2016
*This image is copyright of its original author
Reconstruction credits: Jorge González
Abstract:
"The fossil record shows that iguanian lizards were widely distributed during the Late Cretaceous. However, the biogeographic history and early evolution of one of its most diverse and peculiar clades (acrodontans) remain poorly known. Here, we present the first Mesozoic acrodontan from Africa, which also represents the oldest iguanian lizard from that continent. The new taxon comes from the Kem Kem Beds in Morocco (Cenomanian, Late Cretaceous) and is based on a partial lower jaw. The new taxon presents a number of features that are found only among acrodontan lizards and shares greatest similarities with uromastycines, specifically. In a combined evidence phylogenetic dataset comprehensive of all major acrodontan lineages using multiple tree inference methods (traditional and implied weighting maximum-parsimony, and Bayesian inference), we found support for the placement of the new species within uromastycines, along with Gueragama sulamericana (Late Cretaceous of Brazil). The new fossil supports the previously hypothesized widespread geographical distribution of acrodontans in Gondwana during the Mesozoic. Additionally, it provides the first fossil evidence of uromastycines in the Cretaceous, and the ancestry of acrodontan iguanians in Africa."
RE: Dinosaur news - Ngala - 09-25-2016
A new ornithomimid theropod from the Dinosaur Park Formation of Alberta, Canada
Rativates evadens McFeeters, Ryan, Schröder-Adams & Cullen, 2016
*This image is copyright of its original author
Reconstruction credits: Andrey Atuchin
Abstract:
"A partial ornithomimid skeleton, ROM 1790, from the lower Dinosaur Park Formation (upper Campanian) of Alberta was previously referred to Struthiomimus altus, but lacks diagnostic characters of that species. It is here described as the holotype of a new species, Rativates evadens, gen. et sp. nov., diagnosed by the form of the maxilla-jugal contact, the reduction of the mid-caudal neural spines, the convex fusion of the left and right ischial shafts, the straight-edged distal end of the third metatarsal, and possibly the relatively enlarged medial condyle of the tibia. A histological section of the femur confirms that the type specimen is not a juvenile, despite its relatively small size (approximately 50% the size of large individuals of Struthiomimus altus). Phylogenetic analysis recovers Rativates as a member of a derived ornithomimid clade that includes Ornithomimus, Struthiomimus, and the Asian taxa Anserimimus and Qiupalong. Fusion of the proximal tarsals to the tibia in some ornithomimid specimens was observed to be more complete than previously recognized, increasing the suite of features that these non-avian dinosaurs share homoplastically with birds."
Other articles related:
LATE CRETACEOUS DINOSAUR RESEMBLED MODERN OSTRICH
New Ostrich-Mimic Dinosaur From Alberta Named for Its Ability to Evade Predators
RE: Dinosaur news - Ngala - 10-02-2016
Extreme Modification of the Tetrapod Forelimb in a Triassic Diapsid Reptile Pritchard, Turner, Irmis, Nesbitt & Smith, 2016
*This image is copyright of its original author
Reconstruction credits: Victor Leshyk
*This image is copyright of its original author
Highlights:
• Three-dimensional fossils of the Triassic diapsid Drepanosaurus are described
• Fossils support hypothesis that the forelimb is unique among tetrapods
• The radius and ulna are unequal in length, and two carpals are longer than the radius
• Forelimb range of motion and large claws suggest specialized hook-and-pull digging
Summary:
"The tetrapod forelimb is one of the most versatile structures in vertebrate evolution, having been co-opted for an enormous array of functions. However, the structural relationships between the bones of the forelimb have remained largely unchanged throughout the 375 million year history of Tetrapoda, with a radius and ulna made up of elongate, paralleling shafts contacting a series of shorter carpal bones. These features are consistent across nearly all known tetrapods, suggesting that the morphospace encompassed by these taxa is limited by some sort of constraint(s). Here, we report on a series of three-dimensionally preserved fossils of the small-bodied (<1 m) Late Triassic diapsid reptile Drepanosaurus, from the Chinle Formation of New Mexico, USA, which dramatically diverge from this pattern. Along with the crushed type specimen from Italy, these specimens have a flattened, crescent-shaped ulna with a long axis perpendicular to that of the radius and hyperelongate, shaft-like carpal bones contacting the ulna that are proximodistally longer than the radius. The second digit supports a massive, hooked claw. This condition has similarities to living “hook-and-pull” digging mammals and demonstrates that specialized, modern ecological roles had developed during the Triassic Period, over 200 million years ago. The forelimb bones in Drepanosaurus represent previously unknown morphologies for a tetrapod and, thus, a dramatic expansion of known tetrapod forelimb morphospace."
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RE: Dinosaur news - Ngala - 10-05-2016
Dinosaur footprint among largest on record discovered in Mongolia's Gobi Desert
By Chiara Palazzo
4 OCTOBER 2016 • 9:17AM
Professor Shinobu Ishigaki lying next to a dinosaur footprint in the Mongolian Gobi Desert CREDIT: OKAYAMA UNIVERSITY OF SCIENC
*This image is copyright of its original author
Scientists have unearthed in Mongolia's Gobi Desert one of the biggest dinosaur footprints ever recorded, measuring over a metre in length.
The enormous print, which measures 106cm (42 inches) in length and 77cm in width and dates back more than 70 million years, offers a fresh clue about the giant creatures that roamed the earth millions of years ago, scientists from the Okayama University of Science said.
One of several footprints discovered in the vast Mongolian desert, the huge fossil was unearthed in August by a joint Mongolian-Japanese expedition in a geologic layer formed between 70 million and 90 million years ago in the late Cretaceous Period, researchers said.
A drawing illustrating the dinosaur that may have left a footprint in Mongolia's Gobi Desert CREDIT: OKAYAMA UNIVERSITY OF SCIENCE
*This image is copyright of its original author
It was naturally cast, as sand flowed into dents that had been left by the creature stomping on the once muddy ground, news agency AFP reported.
"This is a very rare discovery as it's a well-preserved fossil footprint that is more than a metre long with imprints of its claws," said a statement issued by Okayama University of Science.
The footprint is believed to have belonged to a Titanosaur, a group of long-necked herbivore sauropods that lived in the Late Cretaceous period, and could have been more than 30 metres long and 20 metres tall, according to Shinobu Ishigaki, a professor from the Okayama University of Science, and the leader of Japan’s research team.
“A whole skeleton of a giant dinosaur that left such a massive footprint has yet to be uncovered in Mongolia,” professor Ishigaki told the Asahi Shimbun. “A fossilised skeleton of such a dinosaur is expected to be eventually discovered.”
“Footprints are living evidence of dinosaurs,” Masateru Shibata, a researcher with the Dinosaur Research Institute at Fukui Prefectural University, told the Japanese daily.
"There is a lot of information that can be obtained only from footprints, including the shape of dinosaur feet as well as the ways in which they walked."
Titanosaurs were the most diverse and abundant large-bodied herbivores in the southern continents during the final 30 million years of the Mesozoic Era.
Titanosaurs species range from the weight of a cow to the weight of a sperm whale or more, according to scientists.
One of the paleontologists lies next to the femur of sauropod discovered in Argentina in 2014 CREDIT: MEF
*This image is copyright of its original author
Several Titanosaur species are regarded as the biggest land-living animals yet discovered.
In 2014 remains of a gigantic Titanosaur were discovered in southern Patagonia, Argentina. According to palaeontologists, the Dreadnoughtus schrani, as the species was named, was the biggest dinosaur ever to walk the planet.
RE: Dinosaur news - Kingtheropod - 10-08-2016
Scientists announce discovery of largest dinosaur ever found in Brazil
*This image is copyright of its original author
"The 25-metre-long ‘Austroposeidon magnificus’ belonged to the Titanosaur group of herbivores and was about six to eight metres tall"
"Brazilian scientists have announced the discovery of what they say is the largest dinosaur ever found in South America’s biggest country.
The director of Rio de Janeiro’s Earth Sciences Museum, Diogenes Campos, said on Wednesday he named the 25-metre-long dinosaur “Austroposeidon magnificus.” It belonged to the Titanosaur group of herbivores that had large bodies, long necks and tails and relatively small skulls, he said.
He said the titanosaur was about six to eight metres tall and lived in what is now Brazil about 70 million years ago.
Fossil of the dinosaur’s neck and spinal vertebrae were found near the city of Presidente Prudente in Sao Paulo state in the 1950s by paleontologist Llewellyn Ivor Price, who died in 1980 without being acknowledged for the discovery.
Alexander Kellner, a paleontologist, said Price had so many other specimens to identify that he did not have time to get to Austroposeidon magnificus. The bones weren’t studied until recent years.
Titanosaurs lived during the Cretaceous Period in areas that today are in South America, Africa, Antarctica and Australia."
https://www.theguardian.com/science/2016/oct/07/scientists-announce-discovery-of-largest-dinosaur-ever-found-in-brazil
RE: Dinosaur news - Ngala - 10-09-2016
Good news @Kingtheropod, thanks for sharing. This is the article:
A New Giant Titanosauria (Dinosauria: Sauropoda) from the Late Cretaceous Bauru Group, Brazil
Austroposeidon magnificus Bandeira et al., 2016
*This image is copyright of its original author
Comparison between Brazilian dinosaurs, from highest: Austroposeidon magnificus (25 meters), Maxakalisaurus topai (13 meters) and Gondwanatitan fausto (8 meters).
Abstract:
"Titanosaurian dinosaurs include some of the largest land-living animals that ever existed, and most were discovered in Cretaceous deposits of Argentina. Here we describe the first Brazilian gigantic titanosaur, Austroposeidon magnificus gen. et sp. nov., from the Late Cretaceous Presidente Prudente Formation (Bauru Group, Paraná Basin), São Paulo State, southeast Brazil. The size of this animal is estimated around 25 meters. It consists of a partial vertebral column composed by the last two cervical and the first dorsal vertebrae, all fairly complete and incomplete portions of at least one sacral and seven dorsal elements. The new species displays four autapomorphies: robust and tall centropostzygapophyseal laminae (cpol) in the last cervical vertebrae; last cervical vertebra bearing the posterior centrodiapophyseal lamina (pcdl) bifurcated; first dorsal vertebra with the anterior and posterior centrodiapophyseal laminae (acdl/pcdl) curved ventrolaterally, and the diapophysis reaching the dorsal margin of the centrum; posterior dorsal vertebra bearing forked spinoprezygapophyseal laminae (sprl). The phylogenetic analysis presented here reveals that Austroposeidon magnificus is the sister group of the Lognkosauria. CT scans reveal some new osteological internal features in the cervical vertebrae such as the intercalation of dense growth rings with camellae, reported for the first time in sauropods. The new taxon further shows that giant titanosaurs were also present in Brazil during the Late Cretaceous and provides new information about the evolution and internal osteological structures in the vertebrae of the Titanosauria clade."
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RE: Dinosaur news - Ngala - 11-06-2016
New Australian sauropods shed light on Cretaceous dinosaur palaeobiogeography
Savannasaurus elliottorum Poropat et al., 2016
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Figure 4: Savannasaurus elliottorum gen. et sp. nov., holotype specimen AODF 660.
(a–e) Dorsal vertebrae (left lateral view). (f) Sacrum (ventral view). (g,h) Caudal vertebrae (left lateral view). (i) Left coracoid (lateral view). (j) Right sternal plate (ventral view). (k) Left radius (posterior view). (l) Right metacarpal III (anterior view). (m) Left astragalus (anterior view). (n) Coossified right and left pubes (anterior view). A number of ribs were preserved but have been omitted for clarity. Scale bar = 500 mm.
Abstract:
"Australian dinosaurs have played a rare but controversial role in the debate surrounding the effect of Gondwanan break-up on Cretaceous dinosaur distribution. Major spatiotemporal gaps in the Gondwanan Cretaceous fossil record, coupled with taxon incompleteness, have hindered research on this effect, especially in Australia. Here we report on two new sauropod specimens from the early Late Cretaceous of Queensland, Australia, that have important implications for Cretaceous dinosaur palaeobiogeography. Savannasaurus elliottorum gen. et sp. nov. comprises one of the most complete Cretaceous sauropod skeletons ever found in Australia, whereas a new specimen of Diamantinasaurus matildae includes the first ever cranial remains of an Australian sauropod. The results of a new phylogenetic analysis, in which both Savannasaurus and Diamantinasaurus are recovered within Titanosauria, were used as the basis for a quantitative palaeobiogeographical analysis of macronarian sauropods. Titanosaurs achieved a worldwide distribution by at least 125 million years ago, suggesting that mid-Cretaceous Australian sauropods represent remnants of clades which were widespread during the Early Cretaceous. These lineages would have entered Australasia via dispersal from South America, presumably across Antarctica. High latitude sauropod dispersal might have been facilitated by Albian–Turonian warming that lifted a palaeoclimatic dispersal barrier between Antarctica and South America."
RE: Dinosaur news - Ngala - 11-08-2016
Kaikaifilu hervei gen. et sp. nov., a new large mosasaur (Squamata, Mosasauridae) from the upper Maastrichtian of Antarctica
Kaikaifilu hervei Oteroa, Soto-Acuñaa, Rubilar-Rogersb, Gutsteina, 2016
*This image is copyright of its original author
Abstract:
"We present a large, fragmentary skull and the humerus of a mosasaur (Squamata, Mosasauroidea) recovered from upper Maastrichtian beds of the López de Bertodano Formation in Marambio (=Seymour) Island, Antarctica. The material belongs to a large, adult individual with marked heterodonty as well as unusual humeral features. Different phylogenetic analyses returned the studied specimen within the Tylosaurinae, while the unique features of the skull and humerus allow distinguish it from the unique Antarctic known tylosaurine species, Taniwhasaurus antarcticus (Novas et al., 2002), as well as from other known Late Cretaceous mosasaurids from the Southern Hemisphere, thus, justifying the erection of a new taxon, Kaikaifilu hervei gen. et. sp. nov. The different dental types documented in the specimen studied have been previously recorded through isolated teeth from the same locality and were subsequently referred to several genera. This new find and its importance to comprehend the previously known fragmentary records strongly suggests that the diversity of Antarctic mosasaurids could be more reduced than previously interpreted, including taxa which are different to the genera and species from the Northern Hemisphere. The new material represents the youngest occurrence of tylosaurines in Antarctica."
RE: Dinosaur news - Ngala - 11-10-2016
Cranial bone histology of Metoposaurus krasiejowensis (Amphibia, Temnospondyli) from the Late Triassic of Poland Gruntmejer, Konietzko-Meier & Bodzioch, 2016
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Figure 1: The skull of Metoposaurus krasiejowensis (UOPB 01029) from the Late Triassic of Poland.
(A) Dorsal view of skull; (B) Ventral view of the skull. Scale bar equals 10 cm.
Abstract:
"In this study, 21 skull bones of Metoposaurus krasiejowensis from the Late Triassic of Poland were investigated histologically. Dermal bones show a diploë structure, with an ornamented external surface. The ridges consist of mostly well vascularized parallel-fibered bone; the valleys are built of an avascular layer of lamellar bone. The thick middle region consists of cancellous bone, with varying porosity. The thin and less vascularized internal cortex consists of parallel-fibered bone. The numerous Sharpey’s fibers and ISF are present in all bones. The cyclicity of growth is manifested as an alternation of thick, avascular annuli and high vascularized zones as well as a sequence of resting lines. The detailed histological framework of dermal bones varies even within a single bone; this seems to be related to the local biomechanical loading of the particular part of the skull. The dynamic processes observed during the ornamentation creation indicate that the positions of the ridges and grooves change during growth and could be a specific adaptation to changing biomechanical conditions and stress distribution during bone development. In the supratemporal, the cementing lines show that the remodeling process could be involved in the creations of sculpture. The common occurrence of ISF suggests that metaplastic ossification plays an important role during cranial development. Endochondral bones preserved the numerous remains of calcified cartilage. This indicates that ossification follows a pattern known for stereospondyl intercentra, with relatively slow ossification of the trabecular part and late development of the periosteal cortex. The large accumulation of Sharpey’s fibers in the occipital condyles indicates the presence of strong muscles and ligaments connecting the skull to the vertebral column."
RE: Dinosaur news - Ngala - 11-15-2016
A toothed turtle from the Late Jurassic of China and the global biogeographic history of turtles
Sichuanchelys palatodentata Joyce, Rabi, Clark & Xu, 2016
*This image is copyright of its original author
Reconstruction credits: Lida Xing
Abstract:
Background
Turtles (Testudinata) are a successful lineage of vertebrates with about 350 extant species that inhabit all major oceans and landmasses with tropical to temperate climates. The rich fossil record of turtles documents the adaptation of various sub-lineages to a broad range of habitat preferences, but a synthetic biogeographic model is still lacking for the group.
Results
We herein describe a new species of fossil turtle from the Late Jurassic of Xinjiang, China, Sichuanchelys palatodentata sp. nov., that is highly unusual by plesiomorphically exhibiting palatal teeth. Phylogenetic analysis places the Late Jurassic Sichuanchelys palatodentata in a clade with the Late Cretaceous Mongolochelys efremovi outside crown group Testudines thereby establishing the prolonged presence of a previously unrecognized clade of turtles in Asia, herein named Sichuanchelyidae. In contrast to previous hypotheses, M. efremovi and Kallokibotion bajazidi are not found within Meiolaniformes, a clade that is here reinterpreted as being restricted to Gondwana.
Conclusions
A revision of the global distribution of fossil and recent turtle reveals that the three primary lineages of derived, aquatic turtles, including the crown, Paracryptodira, Pan-Pleurodira, and Pan-Cryptodira can be traced back to the Middle Jurassic of Euramerica, Gondwana, and Asia, respectively, which resulted from the primary break up of Pangaea at that time. The two primary lineages of Pleurodira, Pan-Pelomedusoides and Pan-Chelidae, can similarly be traced back to the Cretaceous of northern and southern Gondwana, respectively, which were separated from one another by a large desert zone during that time. The primary divergence of crown turtles was therefore driven by vicariance to the primary freshwater aquatic habitat of these lineages. The temporally persistent lineages of basal turtles, Helochelydridae, Meiolaniformes, Sichuanchelyidae, can similarly be traced back to the Late Mesozoic of Euramerica, southern Gondwana, and Asia. Given the ambiguous phylogenetic relationships of these three lineages, it is unclear if their diversification was driven by vicariance as well, or if they display a vicariance-like pattern. The clean, primary signal apparent among early turtles is secondarily obliterated throughout the Late Cretaceous to Recent by extensive dispersal of continental turtles and by multiple invasions of marine habitats.
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RE: Dinosaur news - Ngala - 11-16-2016
Walk before you jump: new insights on early frog locomotion from the oldest known salientian Lires, Soto & Gómez, 2016
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"This is a graph of the discriminant analysis that they did. In this kind of statistical analysis, four different variables were sort of “squashed down” to two more significant values, called Root 1 and Root 2. Think of them as summaries of larger groups of data." Credits: Jumping the Evolutionary Assembly Line
Abstract:
"Understanding the evolution of a Bauplan starts with discriminating phylogenetic signal from adaptation and the latter from exaptation in the observed biodiversity. Whether traits have predated, accompanied, or followed evolution of particular functions is the basic inference to establish the type of explanations required to determine morphological evolution. To accomplish this, we focus in a particular group of vertebrates, the anurans. Frogs and toads have a unique Bauplan among vertebrates, with a set of postcranial features that have been considered adaptations to jumping locomotion since their evolutionary origin. This interpretation is frequently stated but rarely tested in scientific literature. We test this assumption reconstructing the locomotor capabilities of the earliest known salientian, Triadobatrachus massinoti. This extinct taxon exhibits a mosaic of features that have traditionally been considered as representing an intermediate stage in the evolution of the anuran Bauplan, some of which were also linked to jumping skills. We considered T. massinoti in an explicit evolutionary framework by means of multivariate analyses and comparative phylogenetic methods. We used length measurements of major limb bones of 188 extant limbed amphibians (frogs and salamanders) and lizards as a morphological proxy of observed locomotor behavior. Our findings show that limb data correlate with locomotion, regardless of phylogenetic relatedness, and indicate that salamander-like lateral undulatory movements were the main mode of locomotion of T. massinoti. These results contrast with recent hypotheses and indicate that derived postcranial features that T. massinoti shared with anurans might have been later co-opted as exaptations in jumping frogs."
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RE: Dinosaur news - Ngala - 11-18-2016
A Late Cretaceous diversification of Asian oviraptorid dinosaurs: evidence from a new species preserved in an unusual posture
Tongtianlong limosus Lü, Chen, Brusatte, Zhu & Shen, 2016
*This image is copyright of its original author
Figure 5: An artistic reconstruction, showing the last-ditch struggle of Tongtianlong limosus as it was mired in mud, one possible, but highly speculative, interpretation for how the specimen was killed and buried (Drawn by Zhao Chuang).
Abstract:
"Oviraptorosaurs are a bizarre group of bird-like theropod dinosaurs, the derived forms of which have shortened, toothless skulls, and which diverged from close relatives by developing peculiar feeding adaptations. Although once among the most mysterious of dinosaurs, oviraptorosaurs are becoming better understood with the discovery of many new fossils in Asia and North America. The Ganzhou area of southern China is emerging as a hotspot of oviraptorosaur discoveries, as over the past half decade five new monotypic genera have been found in the latest Cretaceous (Maastrichtian) deposits of this region. We here report a sixth diagnostic oviraptorosaur from Ganzhou, Tongtianlong limosus gen. et sp. nov., represented by a remarkably well-preserved specimen in an unusual splayed-limb and raised-head posture. Tongtianlong is a derived oviraptorid oviraptorosaur, differentiated from other species by its unique dome-like skull roof, highly convex premaxilla, and other features of the skull. The large number of oviraptorosaurs from Ganzhou, which often differ in cranial morphologies related to feeding, document an evolutionary radiation of these dinosaurs during the very latest Cretaceous of Asia, which helped establish one of the last diverse dinosaur faunas before the end-Cretaceous extinction."
RE: Dinosaur news - Ngala - 12-08-2016
A new armored archosauriform (Diapsida: Archosauromorpha) from the marine Middle Triassic of China, with implications for the diverse life styles of archosauriforms prior to the diversification of Archosauria
Litorosuchus somnii Li et al., 2016
*This image is copyright of its original author
Abstract:
"Reptiles have a long history of transitioning from terrestrial to semi-aquatic or aquatic environments that stretches back at least 250 million years. Within Archosauria, both living crocodylians and birds have semi-aquatic members. Closer to the root of Archosauria and within the closest relatives of the clade, there is a growing body of evidence that early members of those clades had a semi-aquatic lifestyle. However, the morphological adaptations to a semi-aquatic environment remain equivocal in most cases. Here, we introduce a new Middle Triassic (245–235 Ma) archosauriform, Litorosuchus somnii, gen. et sp. nov., based on a nearly complete skeleton from the Zhuganpo Member (Ladinian [241–235 Ma]) of the Falang Formation, Yunnan, China. Our phylogenetic analyses suggest that Litorosuchus is a stem archosaur closely related to the aberrant Vancleavea just outside of Archosauria. The well-preserved skeleton of L. somnii bears a number of morphological characters consistent with other aquatic-adapted tetrapods including: a dorsally directed external naris, tall neural spines and elongate chevrons in an elongated tail, a short and broad scapula, webbed feet, long cervical vertebrae with long slender ribs, and an elongated rostrum with long and pointed teeth. Together these features represent one of the best-supported cases of a semi-aquatic mode of life for a stem archosaur. Together with Vancleavea campi, the discovery of L. somnii demonstrates a growing body of evidence that there was much more diversity in mode of life outside Archosauria. Furthermore, L. somnii helps interpret other possible character states consistent with a semi-aquatic mode of life for archosauriforms, including archosaurs."
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