|
Dinosaur news
|
Exceptional preservation of soft tissue in a new specimen of Eoconfuciusornis and its biological implications Zheng, O'Connor, Wang, Pan, Wang, Wang & Zhou, 2017
 *This image is copyright of its original author In vivo reconstruction of a male and female pair of Eoconfuciusornis. Artwork by Michael Rothman.  *This image is copyright of its original author (a) Photograph of Eoconfuciusornis indet. STM7-144, preserved in right lateral view; scale bar equals 20 mm. Inset SEM images (all scale bars equal 2 μm); (b) left-wing coverts (sample 2_2) preserving black eumelanosomes; © coronal feathers (sample 2_1) preserving grey eumelanosomes; (d) dark spot of secondaries (sample A) preserving black eumelanosomes; (e) light part of secondaries (sample C) preserving grey mouldic eumelanosomes; (f) tail feathers (sample 2_3) preserving black eumelanosomes; (g) crural feathers (sample 2_4) preserving grey eumelanosomes; (h) submalar feathers (sample G) preserving phaeomelanosomes. Yellow dots indicate location of each sample. Abstract: "We report on an exceptional specimen of Eoconfuciusornis preserving rare soft-tissue traces of the ovary and wing. Ovarian follicles preserve a greater hierarchy than observed in Jeholornis and enantiornithines, suggesting confuciusornithiforms evolved higher rates of yolk deposition in parallel with the neornithine lineage. The preserved soft tissues of the wing indicate the presence of a propatagium and postpatagium, whereas an alular patagium is absent. Preserved remnants of the internal support network of the propatagium bear remarkable similarity to that of living birds. Soft tissue suggests the confuciusornithiform propatagium could maintain a cambered profile and generate lift. The feathers of the wing preserve remnants of their original patterning; however, this is not strongly reflected by observable differences under scanning electron microscopy (SEM). The tail plumage lacks elongate rectrices, suggesting that the earliest known confuciusornithiforms were sexually dimorphic in their plumage." Other articles related: Scientists make new discovery about bird evolution
Sauropod tooth morphotypes from the Upper Jurassic of the Lusitanian Basin (Portugal) Mocho, Royo-Torres, Malafaia, Escaso & Ortega, 2017
 *This image is copyright of its original author Abstract: "The Upper Jurassic of the Lusitanian Basin has yielded an important fossil record of sauropods, but little information is available about the tooth morphotypes represented in this region. A large sample of teeth, both unpublished and published, is described and discussed here. Four main tooth morphologies are identified: spatulate, heart-shaped, pencil-shaped, and compressed cone-chisel-shaped. Heart-shaped teeth are considered to be exclusive to a non-neosauropod eusauropod, tentatively referred to Turiasauria. The spatulate teeth can be attributed to members of the Macronaria; they have a complex cingulum, more than one lingual facet and a labial ridge. The compressed cone-chisel-shaped teeth are also attributed to macronarians and the presence of an axially twisted apex through an arc of 30°–45° suggests putative affinities with Europasaurus and basal titanosauriforms. The variability observed in the overall morphology and wrinkling pattern of the compressed cone-chisel-shaped teeth may be due to factors related to the tooth position or to the ontogeny of individuals. Finally, pencil-shaped teeth with high slenderness index values, oval and apically located wear facets, subcylindrical crowns and lacking carinae, are tentatively assigned to Diplodocoidea. The diversity of tooth morphologies is in accordance with the known palaeobiodiversity of the Portuguese Late Jurassic sauropod fauna, which is composed of non-neosauropod eusauropods (turiasaurs), diplodocoids (diplodocids) and macronarians (camarasaurids and probably brachiosaurids). The Late Jurassic sauropod fossil record of the Iberian Peninsula presents the broadest tooth morphospace range in the world from this period, suggesting a wide niche partition for sauropods, and corresponding high taxonomic diversity." Other articles related: La diversidad de dinosaurios de Portugal es mayor de lo que se pensaba La diversidad de dinosaurios de Portugal es mayor de lo que se pensaba
A new tyrannosaur with evidence for anagenesis and crocodile-like facial sensory system
Daspletosaurus horneri Carr, Varricchio, Sedlmayr, Roberts & Moore, 2017  *This image is copyright of its original author Figure 4: The craniofacial epidermis of Daspletosaurus horneri sp. nov., based on comparison with its closest living relatives, crocodylians and birds. Bone texture indicates large zones of large, flat scales and subordinate regions of armor-like skin and cornified epidermis; integumentary sense organs occur on the flat scales that cover the densest regions of neurovascular foramina. The region outside of the crocodylian-like skin is reconstructed with small scales after fossilized skin impressions of tyrannosaurids. This figure is not covered by the CC BY licence. Illustration © Dino Pulerà. All rights reserved, used with permission.  *This image is copyright of its original author Figure 1: Skull and jaws of the holotype (MOR 590) of Daspletosaurus horneri sp. nov.; (A) photograph and, (B) labeled line drawing of skull and jaws in left lateral view; © photograph and, (D) labeled line drawing of occiput and suspensorium in caudal view; (E) photograph and, (F) labeled line drawing of skull in dorsal view. Scale bars equal 10 cm. Abbreviations: MOR, Museum of the Rockies. Abstract: "A new species of tyrannosaurid from the upper Two Medicine Formation of Montana supports the presence of a Laramidian anagenetic (ancestor-descendant) lineage of Late Cretaceous tyrannosaurids. In concert with other anagenetic lineages of dinosaurs from the same time and place, this suggests that anagenesis could have been a widespread mechanism generating species diversity amongst dinosaurs, and perhaps beyond. We studied the excellent fossil record of the tyrannosaurid to test that hypothesis. Phylogenetic analysis places this new taxon as the sister species to Daspletosaurus torosus. However, given their close phylogenetic relationship, geographic proximity, and temporal succession, where D. torosus (~76.7–75.2 Ma) precedes the younger new species (~75.1–74.4 Ma), we argue that the two forms most likely represent a single anagenetic lineage. Daspletosaurus was an important apex predator in the late Campanian dinosaur faunas of Laramidia; its absence from later units indicates it was extinct before Tyrannosaurus rex dispersed into Laramidia from Asia. In addition to its evolutionary implications, the texture of the facial bones of the new taxon, and other derived tyrannosauroids, indicates a scaly integument with high tactile sensitivity. Most significantly, the lower jaw shows evidence for neurovasculature that is also seen in birds."
Supplementary cranial description of the types of Edmontosaurus regalis (Ornithischia: Hadrosauridae), with comments on the phylogenetics and biogeography of Hadrosaurinae Xing, Mallon & Currie, 2017
 *This image is copyright of its original author Fig 20. Strict consensus of 24 most parsimonious trees resulting from the maximum parsimony analysis of Hadrosauroidea, showing the sister-group relationship between Hadrosaurinae and Lambeosaurinae within Hadrosauridae. Numbers above lines represent bootstrap proportions, whereas those below lines represent Bremer decay values. Bootstrap proportions lower than 20 and Bremer decay values less than 2 are not shown. Abstract: "The cranial anatomy of the flat-skulled hadrosaurine Edmontosaurus regalis (Ornithischia: Hadrosauridae) is extensively described here, based on the holotype and paratype collected from the middle part of the Horseshoe Canyon Formation in southern Alberta. Focus is given to previously undocumented features of ontogenetic and phylogenetic importance. This description facilitates overall osteological comparisons between E. regalis and other hadrosaurids (especially E. annectens), and revises the diagnosis of E. regalis, to which a new autapomorphy (the dorsal half of the jugal anterior process bearing a sharp posterolateral projection into the orbit) is added. We consider the recently named Ugrunaaluk kuukpikensis from the upper Campanian/lower Maastrichtian of Alaska a nomen dubium, and conservatively regard the Alaskan material as belonging to Edmontosaurus sp.. A phylogenetic analysis of Hadrosauroidea using maximum parsimony further corroborates the sister-taxon relationship between E. regalis and E. annectens. In the strict consensus tree, Hadrosaurus foulkii occurs firmly within the clade comprising all non-lambeosaurine hadrosaurids, supporting the taxonomic scheme that divides Hadrosauridae into Hadrosaurinae and Lambeosaurinae. Within Edmontosaurini, Kerberosaurus is posited as the sister taxon to the clade of Shantungosaurus + Edmontosaurus. The biogeographic reconstruction of Hadrosaurinae in light of the time-calibrated cladogram and probability calculation of ancestral areas for all internal nodes reveals a significantly high probability for the North American origin of the clade. However, the Laramidia–Appalachia dispersals around the Santonian–Campanian boundary, inferred from the biogeographic scenario for the North American origin of Hadrosaurinae, are in conflict with currently accepted paleogeographic models. By contrast, the Asian origin of Hadrosaurinae with its relatively low probability resulting from the biogeographic analysis is worth seriously considering, despite the lack of fossil material from the Santonian and lower Campanian of Asia. Extra fossil collecting in appropriate geographic locations and stratigraphic intervals of Asia and Europe will help to clarify the biogeographic dynamics of hadrosaurine dinosaurs in the near future." 
The oldest known relative of dinosaurs was a total freak, experts say
 *This image is copyright of its original author The 245-million-year-old fossils were some of the strangest ones Sterling Nesbitt had ever seen. Their bodies looked like crocodiles — stout and muscular, with four sturdy legs. But their necks and tails were unusually long, and the bones bore certain markings only found in dinosaurs. The fossils definitely didn't belong to any creature known to science. But Nesbitt knew of an oddball animal that would fit these fossils perfectly: Teleocrater rhadinos, an ancient reptile discovered in Tanzania in the 1930s but never formally classified. Nesbitt had seen teleocrater's skeleton displayed in the London Natural History Museum years ago. Now, standing amid swaying grasses and piles of upturned soil at a fossil site not far from where the original bones were discovered, gazing at the remains of three new specimens, Nesbitt knew he was looking at the same creature. This time, he and his colleagues had enough material to figure out how teleocrater fits into the evolutionary family tree. It is the oldest known branch on the lineage that would eventually lead to dinosaurs, they report Wednesday in the journal Nature. To the untrained eye, teleocrater looks no stranger than any other dinosaur (I mean, have you seen the “Chicken from Hell?"), but experts say its body plan is extremely unusual for an ancient reptile. The freaky newfound species is forcing paleontologists to rethink how dinosaurs evolved. Nesbitt, a vertebrate paleobiologist at Virginia Tech, is an expert on the rise of a group of animals called archosaurs. Around 250 million years ago, that group diversified into two lineages — one led to today's crocodiles, the other led to the “avemetatarsalins,” which included dinosaurs and eventually birds. Phylogenetic analysis, which compares traits of various species to figure out how they relate to one another, suggests that teleocrater is a very early branch on the avemetatarsalin lineage. It's not a direct ancestor of dinosaurs (teleocrater's lineage eventually went extinct). Instead, it's more like an older cousin — one with a deep knowledge of family history and a proclivity for gossip. It can tell scientists quite a lot about dinosaurs' murky past. “Given their position on the family tree, they give us a good idea of what the common ancestor of all bird line archosaurs was like,” said Ken Angielczyk, a paleontologist at the Field Museum in Chicago and a co-author on the study. “If we want to understand how the very distinctive dinosaur and bird body plan evolved into something that’s very successful … teleocrater provides insight into the first step in that process.” The story that teleocrater tells is quite complex, the scientists say. The new species shows that some features thought to characterize dinosaurs actually evolved much earlier, soon after the split from crocodiles. Teleocrater bears a depression in its skull usually found only in dinosaurs, its hip muscles attached to its thigh bones in the same manner as those of birds, and its vertebrae are similar to those of other avemetatarsalins. But teleocrater lacks the distinctive ankle bone that would come to characterize dinosaurs and birds, and it walked on four legs, not two, as scientists believe the earliest dinosaurs did. This suggests that the ancient giants' distinctive body plan evolved gradually, and possibly multiple times. This matters, because dinosaurs are some of the most successful creatures in Earth's history, and scientists want to know why. Dinosaurs were the largest animals to walk on land and they dominated the planet for 150 million years (humans, by contrast, have been around for just a measly 200,000 years). Not even a cataclysmic asteroid impact could totally end the party — dinosaurs' descendants, birds, still live among us. The teleocrater discovery comes in the wake of a recent phylogenetic study that challenged scientists' understanding of the order in which dinosaurs diversified. That research, published in Nature last month, suggested that dinosaur family groupings needed to be reorganized and renamed and that dinosaurs arose in a completely different part of the world than originally thought. “It’s almost a one-two punch,” Nesbitt said of the two new studies. “It’s complicated the once-simple picture of how dinosaurs got their features.” Nesbitt, Angielczyk and their colleagues weren't looking to upend our understanding of dinosaur evolution when they traveled to southern Tanzania in 2015. They were searching the 245-year-old bone beds for clues about the end-Permian mass extinction, which wiped out more species than any other event in Earth's history. The event was so catastrophic that paleontologists refer to it simply as “the Great Dying,” and scientists are interested in how life recovered in its wake. The teleocrater fossils, which date back to about 5 million years after the mass extinction, suggest that the archosaurs evolved to take advantage of the newly vacated ecological niches. Teleocrater would have fit somewhere in the middle of the early Triassic food chain. It was about 6 to 8 feet long and had the sharp, serrated teeth of a fierce predator. Its legs were shorter than a dinosaur's, but not as sprawling as those of a crocodile. It shared its habitat — a river system lush with ferns — with an array of other reptiles large and small. Large, hippo-sized relatives of mammals called dicynodonts were lumbering around as well. The first dinosaurs wouldn't appear on the scene until about 15 million years later. But according to Nesbitt, the teleocrater discovery suggests it's worth looking at this period before they evolved. “We should look at their close relatives too,” he said “because there’s a lot more going on than anyone would have predicted.” http://www.msn.com/en-ca/news/world/the-...spartanntp
A new tiny dromaeosaurid dinosaur from the Lower Cretaceous Jehol Group of western Liaoning and niche differentiation among the Jehol dromaeosaurids
Zhongjianosaurus yangi Xu & Qin, 2017  *This image is copyright of its original author Abstract: "The Early Cretaceous Jehol dromaeosaurids are taxonomically and morphologically diverse, and one of them, Microraptor zhaoianus, has been suggested to be among the smallest known non-avialan theropods. However, this idea is based on specimens of relatively early ontogenetic stages, and the lower limit of the mature body mass of Jehol dromaeosaurids thus remains unknown. Here we describe a new dromaeosaurid, Zhongjianosaurus yangi gen. et sp. nov., based on a specimen from the Lower Cretaceous Yixian Formation (the middle section of the Jehol Group) from Sihedang, Lingyuan County, Liaoning in Northeast China. While this new taxon is referable to the Microraptorinae, it differs from other microraptorine dromaeosaurids in numerous features, most notably the fusion of proportionally long uncinate processes to dorsal ribs, a humerus with a strongly medially offset proximal end and a large fenestra within the deltopectoral crest, an ulna slightly longer than the humerus, and an arctometatarsalian pes. Most significantly, the estimated 0.31 kg mass of the Z. yangi holotype of an adult individual confirms that some Jehol dromaeosaurids are among the smallest known non-avialan theropods. Our preliminary analysis demonstrates niche differentiation among the Jehol dromaeosaurids, a phenomenon rarely reported among Mesozoic dinosaurian faunas."
A morphological study of the first known piscivorous enantiornithine bird from the Early Cretaceous of China
Piscivorenantiornis inusitatus Wang & Zhou, 2017  *This image is copyright of its original author Fig.3 Life reconstruction of the fish-eating enantiornithine bird (Image by SHI Aijuan).  *This image is copyright of its original author FIGURE 1. Photograph of the holotype of Piscivorenantiornis inusitatus, gen. et sp. nov., IVPP V22582. Abstract: "A fish-eating enantiornithine bird with a gastric pellet composed of fish bones has recently been reported from the Lower Cretaceous Jiufotang Formation of Liaoning Province, northeastern China. Along with other discoveries, this specimen reveals that distinct features of modern avian digestive system were well established in those early birds. On the basis of a detailed anatomical study presented here, we show that this fish-eating enantiornithine bird represents a new taxon, Piscivorenantiornis inusitatus, gen. et sp. nov. The well-preserved elements of the skull, neck, sternum, and pelvis further enrich our understanding of the morphological diversity in early enantiornithines. Most notably, the cranial articular facet of the caudal cervical vertebra is dorsoventrally concave and mediolaterally convex, a feature otherwise unknown among other birds and with unclear functional significance." Full Article Other articles related: Fish-eating enantiornithine bird provides evidence of modern avian digestive features Fish-Eating Enantiornithine Bird Provides Evidence of Modern Avian Digestive Features World's oldest bird vomit heaved out in China
A new ankylosaurine dinosaur from the Judith River Formation of Montana, USA, based on an exceptional skeleton with soft tissue preservation
Zuul crurivastator Arbour & Evans, 2017  *This image is copyright of its original author Reconstruction credits: Danielle Dufault  *This image is copyright of its original author Zuul crurivastator’s skull. Credits: Brian Boyle/Royal Ontario Museum  *This image is copyright of its original author Figure 2. Holotype of Zuul crurivastator, ROM 75860, skull in (a) left lateral, (b) anterior, © posterior and (d) oblique left anterodorsal views. (a′–d′) are digital models of the skull. Diagnostic characters for Z. crurivastator include (1) imbricated frontonasal caputegulae, (2) peaked, pyramidal prefrontal and middle supraorbital caputegulae and (3) prominent apicobasal furrows on the squamosal horns. Abbreviations are as follows: asca, anterior supraorbital caputegulum; fm, foramen magnum; laca, lacrimal caputegulum; loca, loreal caputegulum; mnca, median nasal caputegulum; mx, maxilla; na, external naris; nuca, nuchal caputegulum; oo, ocular osteoderm; oc, occipital condyle; pa, parietal; pmx, premaxilla; pnca, postnarial caputegulum; poc, paroccipital process; poca, postocular caputegulum; prfca, prefrontal caputegulum; psca, posterior supraorbital caputegulum; q, quadrate; qjh, quadratojugal horn; snca, supranarial caputegulum; sqh, squamosal horn. Abstract: "The terrestrial Judith River Formation of northern Montana was deposited over an approximately 4 Myr interval during the Campanian (Late Cretaceous). Despite having been prospected and collected continuously by palaeontologists for over a century, few relatively complete dinosaur skeletons have been recovered from this unit to date. Here we describe a new genus and species of ankylosaurine dinosaur, Zuul crurivastator, from the Coal Ridge Member of the Judith River Formation, based on an exceptionally complete and well-preserved skeleton (ROM 75860). This is the first ankylosaurin skeleton known with a complete skull and tail club, and it is the most complete ankylosaurid ever found in North America. The presence of abundant soft tissue preservation across the skeleton, including in situ osteoderms, skin impressions and dark films that probably represent preserved keratin, make this exceptional skeleton an important reference for understanding the evolution of dermal and epidermal structures in this clade. Phylogenetic analysis recovers Zuul as an ankylosaurin ankylosaurid within a clade of Dyoplosaurus and Scolosaurus, with Euoplocephalus being more distantly related within Ankylosaurini. The occurrence of Z. crurivastator from the upper Judith River Formation fills a gap in the ankylosaurine stratigraphic and geographical record in North America, and further highlights that Campanian ankylosaurines were undergoing rapid evolution and stratigraphic succession of taxa as observed for Laramidian ceratopsids, hadrosaurids, pachycephalosaurids and tyrannosaurids." Other articles related: Meet Zuul, destroyer of shins - the 75m-year-old 'Ghostbuster' dinosaur Zuul, Destroyer of Shins
The earliest known titanosauriform sauropod dinosaur and the evolution of Brachiosauridae
Vouivria damparisensis Mannion, Allain & Moine, 2017  *This image is copyright of its original author Abstract: "Brachiosauridae is a clade of titanosauriform sauropod dinosaurs that includes the well-known Late Jurassic taxa Brachiosaurus and Giraffatitan. However, there is disagreement over the brachiosaurid affinities of most other taxa, and little consensus regarding the clade’s composition or inter-relationships. An unnamed partial sauropod skeleton was collected from middle–late Oxfordian (early Late Jurassic) deposits in Damparis, in the Jura department of eastern France, in 1934. Since its brief description in 1943, this specimen has been informally known in the literature as the ‘Damparis sauropod’ and ‘French Bothriospondylus’, and has been considered a brachiosaurid by most authors. If correctly identified, this would make the specimen the earliest known titanosauriform. Coupled with its relatively complete nature and the rarity of Oxfordian sauropod remains in general, this is an important specimen for understanding the early evolution of Titanosauriformes. Full preparation and description of this specimen, known from teeth, vertebrae and most of the appendicular skeleton of a single individual, recognises it as a distinct taxon: Vouivria damparisensis gen. et sp. nov. Phylogenetic analysis of a data matrix comprising 77 taxa (including all putative brachiosaurids) scored for 416 characters recovers a fairly well resolved Brachiosauridae. Vouivria is a basal brachiosaurid, confirming its status as the stratigraphically oldest known titanosauriform. Brachiosauridae consists of a paraphyletic array of Late Jurassic forms, with Europasaurus, Vouivria and Brachiosaurus recovered as successively more nested genera that lie outside of a clade comprising (Giraffatitan + Sonorasaurus) + (Lusotitan + (Cedarosaurus + Venenosaurus)). Abydosaurus forms an unresolved polytomy with the latter five taxa. The Early Cretaceous South American sauropod Padillasaurus was previously regarded as a brachiosaurid, but is here placed within Somphospondyli. A recent study contended that a number of characters used in a previous iteration of this data matrix are ‘biologically related’, and thus should be excluded from phylogenetic analysis. We demonstrate that almost all of these characters show variation between taxa, and implementation of sensitivity analyses, in which these characters are excluded, has no effect on tree topology or resolution. We argue that where there is morphological variation, this should be captured, rather than ignored. Unambiguous brachiosaurid remains are known only from the USA, western Europe and Africa, and the clade spanned the Late Jurassic through to the late Albian/early Cenomanian, with the last known occurrences all from the USA. Regardless of whether their absence from the Cretaceous of Europe, as well as other regions entirely, reflects regional extinctions and genuine absences, or sampling artefacts, brachiosaurids appear to have become globally extinct by the earliest Late Cretaceous." Other articles related: Earliest relative of Brachiosaurus dinosaur found in France Fossil sheds light on 'Jurassic Park' dinosaurs
Redescription of the elasmosaurid plesiosaurian Libonectes atlasense from the Upper Cretaceous of Morocco
 *This image is copyright of its original author Reconstruction credits: Hyrotrioskjan Highlights
Abstract: "The holotype of Libonectes atlasense is an almost complete skeleton from Upper Cretaceous (mid-Turonian) rocks of the Goulmima area in eastern Morocco. Initial assessment of this specimen in 2005 proposed generic referral based on stratigraphical contemporaneity with Libonectes morgani from the Cenomanian–Turonian of Texas, U.S.A. Nevertheless, relative differences in the profile of the premaxillary-maxillary tooth row, position of the external bony nasal opening, number of teeth and rostrad inclination of the mandibular symphysis, proportions of the axial neural arch, and number of cervical and pectoral vertebrae were used to distinguish between these species. As part of an on-going comparative appraisal of elasmosaurid plesiosaurian osteo-anatomy, we re-examined the type and formally referred material of both L. atlasense and L. morgani in order to establish species validity, as well as compile a comparative atlas for use in future works. Our inspections revealed that these reportedly distinct species-level fossils are in fact virtually indistinguishable in gross morphology. Indeed, the only substantial difference occurs in relative prominence of the midline keel along the mandibular symphysis, which might be explained by intraspecific variation. Furthermore, our observations permit an amendment to the published generic diagnosis of Libonectes with the confirmation of important states such as the likely presence of a pectoral bar, distocaudad expansion of the humerus, and an epipodial foramen. In addition, novel features include a prominent ‘prong-like’ ventral midline process on the coracoids, and the development of a median pelvic bar that encloses a central fenestration. The composite remains of L. morgani thus constitute one of the most complete elasmosaurid skeletal hypodigms documented worldwide, and evidence a trans-Atlantic distribution for this apparently dispersive species during the early–Late Cretaceous."
A Late Norian-Rhaetian Coelophysid Neotheropod (Dinosauria, Saurischia) from the Quebrada del Barro Formation, Northwestern Argentina
Lucianovenator bonoi Martinez & Apaldetti, 2017  *This image is copyright of its original author Abstract: "Coelophysoids are the most abundant theropod dinosaurs known from the Late Triassic through Early Jurassic represent the earliest major radiation of Neotheropoda. Within Coelophysoidea sensu lato the most stable clade is Coelophysidae, small theropods characterized by long neck and light and kinetic skull. Coelophysids are the most abundant basal non-Tetanurae neotheropods known worldwide, but until recently they were unknown from South America. We report here a new coelophysid neotheropod, Lucianovenator bonoi gen. et sp. nov., from the late Norian-Rhaetian Quebrada del Barro Formation, northwestern Argentina. A phylogenetic analysis recovers Lucianovenator bonoi nested into the monophyletic group Coelophysidae in an unresolved clade together with Coelophysis rhodesiensis and Camposaurus arizonensis. The presence of Lucianovenator in the late Norian-Rhaetian of Argentina increases the poor and scarce record of Triassic South American neotheropods, suggesting that the virtual absence of theropods in the fossil record during the Rhaetian is probably a taphonomic/stratigraphic bias instead of a decline in diversity and abundance after the Norian. Finally, the new find corroborates the American endemism in the Late Triassic and worldwide distribution during the Early Jurassic of coelophysid neotheropods, supporting the extreme faunal homogeneity hypothesized for Early Jurassic continental biotas." Other articles related: Dinosaurio de San Juan, único en Sudamérica Lucianovenator bonoi, un dinosaurio de Caucete `Lucianovenator bonoi´, el dinosaurio hallado en Caucete, único en su tipo de Sudamérica
A New Troodontid Dinosaur (Liaoningvenator curriei gen. et sp. nov.) from the Early Cretaceous Yixian Formation in Western Liaoning Province
Liaoningvenator curriei Shen et al., 2017  *This image is copyright of its original author Reconstruction credits: Zhao Chuang Abstract: "A new troodontid, Liaoningvenator curriei gen. et sp. nov., is described based on a complete skeleton from the Early Cretaceous Yixian Formation of Beipiao City, Liaoning Province. It bears the following characteristics of Troodontidae: numerous and more closely appressed maxillary and dentary teeth; the teeth markedly constricted between the roots and crowns; the nutrient foramina in groove on the external surface of dentary; distal caudal vertebrae having a sulcus on the dorsal midline rather than a neural spine. Unlike other troodontids, Liaoningvenator exhibits a sub-triangular ischial boot in lateral view and slender ischial obturator process; transition point in caudal vertebrae starts from the seventh caudal vertebra. A phylogenetic analysis recovers Liaoningvenator and Eosinopteryx as sister taxa that belong to the same clade. These two taxa share the following three characteristics: (1) anterior maxillary and dentary teeth lack serrations along the anterior carina; (2) shafts of cervical ribs are longer than vertebral centra with which they articulate; and (3) anterior margin of ilium is straight. The histological study indicates that Liaoningvenator was attaining skeletal maturity and at least four years old when it perished. Liaoningvenator represents the fifth troodontid taxon from the Lower Cretaceous equivalent strata of western Liaoning. It provides much new anatomical information on basal troodontid dinosaurs in this region. It also enhances the diversity of the troodontids in Early Cretaceous of China currently known." Other articles related: Paleo Profile: The Liaoning Hunter
Reanalysis of the phylogenetic status of Nipponosaurus sachalinensis (Ornithopoda: Dinosauria) from the Late Cretaceous of Southern Sakhalin Takasaki et al., 2017
 *This image is copyright of its original author From Phys.org: The bones of the dinosaur Mukawaryu which have been cleaned so far. These likely represent more than half of the bones the dinosaur had. Credit: Hokkaido University Abstract: "Nipponosaurus sachalinensis is the only definitive lambeosaurine hadrosaurid from Sakhalin Island of Russia. Previous studies suggested it was a member of Lambeosaurini (derived lambeosaurines). However, its phylogenetic status within Lambeosaurini remains controversial. In addition, some studies argued the juvenile ontogenetic stage of the holotype and regarded Nipponosaurus as an invalid taxon. In order to solve these problems, its definite growth stage is determined through histological studies. Absence of a line of arrested growth, presence of osteons with large vascular spaces, and presence of primary bone remnants even in the highly modified regions of the femur confirm that the holotype was a juvenile. More than a hundred of the 350 characters used to determine the phylogenetic position of Nipponosaurus are ontogenetically variable characters based on the different ontogenetic stages of Hypacrosaurus stebingeri. Our phylogenetic analysis reveals that Nipponosaurus is a basal lambeosaurine hadrosaurid, much further down in the tree than previously suggested, and shows a polytomy with Blasisaurus and Arenyisaurus. This study also indicates that Nipponosaurus is a valid taxon because it possesses unique characters within the Lambeosaurinae (presence of massive surangular anterodorsal process, presence of lateral shelf of the dentary, and a relatively short ulna), which are independent of ontogeny." Other articles related: Japan's largest complete dinosaur skeleton discovered Unraveling the mysteries of Nipponosaurus
A new phylogeny of Stegosauria (Dinosauria, Ornithischia) Raven & Maidment, 2017
 *This image is copyright of its original author Abstract: "The stegosaurs are some of the most easily recognizable dinosaurs, but are surprisingly rare as fossils. Consequently much remains unknown about their palaeobiology, and every new stegosaurian find contributes to our understanding of the evolution of the clade. Since the last attempt to examine the evolutionary relationships of Stegosauria, new specimens have come to light, including the most complete individual of Stegosaurus ever found, new taxa have been described and, perhaps most importantly, new methods for analysis of cladistic datasets have been produced. In the light of these new data and technological advances, the phylogenetic relationships of the stegosaurs and basal armoured dinosaurs are investigated. The inclusion of continuous data results in much better resolution than was previously obtained, and the resulting single most parsimonious tree supports re-erection of the genera Miragaia and Hesperosaurus, which had previously been synonymized with Dacentrurus and Stegosaurus respectively. The recently described genus Alcovasaurus is resolved as a basal thyreophoran, but this is most likely a consequence of a very high degree of missing data and the questionable ontogenetic stage of the specimen. Examination of the effects of continuous data on the analysis suggest that while it contains a phylogenetic signal congruent with that of discrete data and provides better resolution than discrete data alone, it can affect topologies in unpredictable ways, particularly in areas of the tree where there are large amounts of missing data. The phylogeny presented here will form the basis for future work on the palaeobiology of the plated dinosaurs."
Europatitan eastwoodi, a new sauropod from the lower Cretaceous of Iberia in the initial radiation of somphospondylans in Laurasia
Europatitan eastwoodi Fernández-Baldor et al., 2017  *This image is copyright of its original author Reconstruction credits: Davide Bonadonna Abstract: "The sauropod of El Oterillo II is a specimen that was excavated from the Castrillo de la Reina Formation (Burgos, Spain), late Barremian–early Aptian, in the 2000s but initially remained undescribed. A tooth and elements of the axial skeleton, and the scapular and pelvic girdle, represent it. It is one of the most complete titanosauriform sauropods from the Early Cretaceous of Europe and presents an opportunity to deepen our understanding of the radiation of this clade in the Early Cretaceous and study the paleobiogeographical relationships of Iberia with Gondwana and with other parts of Laurasia. The late Barremian–early Aptian is the time interval in the Cretaceous with the greatest diversity of sauropod taxa described in Iberia: two titanosauriforms, Tastavinsaurus and Europatitan; and a rebbachisaurid, Demandasaurus. The new sauropod Europatitan eastwoodi n. gen. n. sp. presents a series of autapomorphic characters in the presacral vertebrae and scapula that distinguish it from the other sauropods of the Early Cretaceous of Iberia. Our phylogenetic study locates Europatitan as the basalmost member of the Somphospondyli, clearly differentiated from other clades such as Brachiosauridae and Titanosauria, and distantly related to the contemporaneous Tastavinsaurus. Europatitan could be a representative of a Eurogondwanan fauna like Demandasaurus, the other sauropod described from the Castrillo de la Reina Formation. The presence of a sauropod fauna with marked Gondwananan affinities in the Aptian of Iberia reinforces the idea of faunal exchanges between this continental masses during the Early Cretaceous. Further specimens and more detailed analysis are needed to elucidate if this Aptian fauna is caused by the presence of previously unnoticed Aptian land bridges, or it represents a relict fauna from an earlier dispersal event." |
| Users browsing this thread: |
| 1 Guest(s) |