Cranial Crest Research Articles

Osteology of the two-fingered oviraptorid Oksoko avarsan (Theropoda: Oviraptorosauria)

Abstract Oviraptorosaurs are among the most diverse and best-known extinct theropod groups. Their bizarre anatomy and their social and reproductive behaviour are now well understood. Among the oviraptorid subclade, the two-fingered Oksoko avarsan is particularly well-represented. It is known from several exquisite skeletons, preserving not only the entire skeleton, but multiple stages through ontogeny, providing an exemplar for understanding the anatomy of oviraptorids and the changes that their skeletons experienced over their lifetimes. Here I comprehensively describe the osteology of Oksoko avarsan and comment on its ontogenetic variation. Excellent preservation of the specimens provides unparalleled detail into the anatomy of an oviraptorid, providing valuable context for interpreting other oviraptorosaurs. Several changes are observed to occur through ontogeny relating to robustness of the bones and proportions of the skeleton, but there is little evidence suggesting that discrete features like the cranial crest arose late in ontogeny. Instead, early development of the cranial crest in oviraptorids, and its internal connection with the nasal passages and other pneumatic spaces, argue in favour of a role in vocalization, perhaps alongside sexual display. Detailed anatomical and ontogenetic data, like those provided by known specimens of Oksoko avarsan, are necessary to help to underpin ongoing research into the palaeobiology and macroevolution of Oviraptorosauria.

Reprogramming of trunk neural crest to a cranial crest-like identity alters their transcriptome and developmental potential

Neural crest cells along the body axis of avian embryos differ in their developmental potential, such that the cranial neural crest forms cartilage and bone whereas the trunk neural crest is unable to do so. Previous studies have identified a cranial crest-specific subcircuit that can imbue the trunk neural crest with the ability to form cartilage after grafting to the head. Here, we examine transcriptional and cell fate changes that accompany this reprogramming. First, we examined whether reprogrammed trunk neural crest maintain the ability to form cartilage in their endogenous environment in the absence of cues from the head. The results show that some reprogrammed cells contribute to normal trunk neural crest derivatives, whereas others migrate ectopically to the forming vertebrae and express cartilage markers, thus mimicking heterotypically transplanted cranial crest cells. We find that reprogrammed trunk neural crest upregulated more than 3000 genes in common with cranial neural crest, including numerous transcriptional regulators. In contrast, many trunk neural crest genes are downregulated. Together, our findings show that reprogramming trunk neural crest with cranial crest subcircuit genes alters their gene regulatory program and developmental potential to be more cranial crest-like.

Hindlimb Skeletal Morphology of the Helmeted Guinea Fowl (Numida meleagridis)

Abstract The Guinea fowl (Numida meleagridis) is a semi-domestic bird whose commercial popularity is on the increase. The gross anatomy of the hindlimbs of 8 helmeted Guinea fowls of equal sexes were studied. The pubic shafts were free, thus they did not fuse ventrally to form a symphysis. The ilium had a quadrilateral and roughly triangular pre and post acetabular wings, respectively. A conspicuous renal fossa was observed in the post acetabular wing. An incomplete concentric obturator foramen, lacking a caudal margin, was formed by the ventral border of the ischium and dorsal border of the cranial pubic shaft, while a prominent ischiopubic fissure was formed by the same bones, caudally. The incomplete concentric nature of the obturator foramen created a common space between it and the ischiopubic fissure. The femoral major trochanter was more proximal than the head, while the minor tro-chanter and the head were on the same horizontal level. The femur lacked a visible pneumatic foramen. The tibiotarsus had a prominent cranial cnemial crest. The fibular spine terminated at the tibia mid-shaft, leaving one interosseous space. An intertarsal sesamoid bone was identified, indicative of an adult skeleton. Crests and channels depicted the hypotarsus. Vascular foramen was identified in the distal extremity of the tibiotarsus. Digit I was oriented to the planter direction. These results, and others, were compared with those of other birds in the available literature, and some morpho-functional paradigm of the Guinea fowl hindlimb skeleton was established.

A taxonomic revision of the Sinopterus complex (Pterosauria, Tapejaridae) from the Early Cretaceous Jehol Biota, with the new genus Huaxiadraco.

Tapejarids are edentulous pterosaurs particularly abundant in the Chinese Jiufotang Formation, counting with over 10 described specimens and dozens of undescribed ones. A total of seven nominal tapejarid species (within two genera) have been proposed, though it is disputed how many of those are valid instead of sexual or ontogenetic morphs of fewer, or a single, species. However, detailed revisions of the matter are still lacking. In the present work, we provide a specimen-level survey of anatomical variation in previously described Jiufotang tapejarid specimens, as well as of six new ones. We present qualitative and morphometric comparisons, aiming to provide a basis for a taxonomic reappraisal of the complex. Our results lead us to interpret two Jiufotang tapejarid species as valid: Sinopterus dongi and Huaxiadraco corollatus (gen. et comb. nov.). Our primary taxonomic decisions did not rely around cranial crest features, which have typically been regarded as diagnostic for most of these proposed species albeit ever-growing evidence that these structures are highly variable in pterosaurs, due to ontogeny and sexual dimorphism. However, a reassessment of premaxillary crest variation in the Sinopterus complex reveals that while much of the observed variation (crest presence and size) can easily be attributed to intraspecific (ontogenetic and sexual) variation, some of it (crest shape) does seem to represent interspecific variation indeed. A phylogenetic analysis including the species regarded as valid was also performed.

Анатомо-топографические особенности заднебедренной группы мышц тазобедренного сустава у благородного пятнистого оленя

The article presents the morphological and functional characteristics of the posterior femoral muscle group of the hip joint in the noble spotted deer. The research was carried out at the Department of Anatomy and Histology of Animals named after Professor A. F. Klimov of the Moscow State Academy of Veterinary Medicine and Biotechnology – MBA named after K. I. Scriabin. The objects of research were a mature noble spotted deer (n=5). The article presents anatomical features of the posterior femoral group of hip extensors in the subspecies of red deer – spotted deer, which are absent in the available literature. The topological features of anatomical formations of the sciatic tubercle are revealed – the presence of dorsal, lateral and medial outgrowths on it. The last outgrowth of the spotted deer is on the same level with the lateral one, unlike the reindeer, which has a ventral outgrowth located below the dorsal outgrowth. As a result of our research, it was found that the gluteal-biceps muscle of the noble spotted deer is fleshy, the largest among the thigh muscles, forms a convex (rounded) contour in the gluteal region, filling most of the gluteal region. Extending in the distal direction, the muscle participates in the formation of the lateral and caudal contour of the thigh, and on the lateral surface of the lower leg forms a flattened tendon, following from the lateral surface of the kneecap, the cranial crest of the tibia to the calcaneal mound of the flattened. The established structural communications of the studied muscles may reflect their functional relationship. The data obtained are reference in assessing the biomechanics of the stato-locomotor act in representatives of the reindeer, as well as in the diagnosis of damage to the musculoskeletal system.

Dental follicle cells show potential for treating Parkinson's disease through dopaminergic-neuronogenic differentiation.

Among all the adult stem cells, odontogenic stem cells inherit the characterization of neurogenic potential of their precursor ones-the cranial crest cells. Dental follicle cells (DFCs), one of the special kind of odontogenic stem cells, are raising interest in applying to regenerative medicine for they possess multi-differentiation potential, relatively free access and ethic-friendly characteristic. Parkinson's disease (PD), as one of the common neurodegenerative disorders, affects about 0.3% of the general population. Stem cell therapies are thought to be effective to treat it. Aiming at tackling ethical-concernings, confined sources and practically applicational limits, we made use of dopaminergic neurongenic differentiation potential of the DFCs and dedicated every effort to applying them as promising cell source for treating PD. Dental follicle cells were cultured from human dental follicle tissues collected from 12 to 18-year-old teenagers' completely impacted third molars. Our data demonstrated that hDFCs were expressing mesenchymal stem cell-associated surface markers, and possessed the ability of osteogenic, adipogenic and neurogenic differentiation in vitro. Additionally, hDFCs formed neuron-like cells in vitro and in vivo, as well as expressing dopaminergic-neuronogenic marker-TH. Moreover, hDFCs survived in the transplanted areas of the Parkinson's disease model of mouse over six weeks post-surgery, and the number of TH-positive DFCs in the DFCs-Grafted group surpassed its counterpart of the MPTP group with statistically significant difference. This study indicated that hDFCs might be a promising source of dopaminergic neurons for functional transplantation, and encouraged further detailed studies on the potential of hDFCs for treating PD.

THE CLINICAL CASE OF HEMIFACIAL MICROSOMIA IN THE NEWBORN BOY FROM MOTHER WITH Z-21

Hemifacial Microsomia (HFM) is a term used to identify facial deformities associated with the development ofthe first and second pairs of branchial arches, characterized by underdevelopment of one half of the face. One typeof hemifacial microsomia is oculo-auriculo-vertebral dysplasia or Goldenhar syndrome.The incidence of HFM is 1:3500-1:7000 of live births and occurs in 1 case per 1000 children with congenitaldeafness. The ratio of boys to girls is 3:2. The etiology and type of inheritance is studied insufficiently. There are threepossible pathogenetic models: vascular abnormalities and hemorrhages in the craniofacial region, damage of Meckel'scartilage, and abnormal cell development of the cranial nerve crest. Environmental factors, maternal internal factors,and genetic factors (OTX2, PLCD3, and MYT1 mutations) may also cause the development of hemifacial microsomia.The article demonstrates a clinical case of hemifacial microsomia in a newborn boy from a mother with Z-21 inthe form of deformation of the left auricle with atresia of the auditory canal and "false" ears on the right, combinedwith congenital anomaly of heart (atrial septal defect) and brain (hypoplasia of the corpus callosum).Emphasis is placed on the need of involving a multidisciplinary team of specialists in the management of thispatient both in the neonatal period and in the system of subsequent follow-up.

Two New Species of Pristimantis (Anura: Strabomantidae) from the Serranía de los Paraguas: A Priority Site for Conservation of Amphibians in Colombia

The Serrania de los Paraguas is a mountainous region situated in the central part of the Cordillera Occidental of Colombia. It rises some 2500 m above the wet forest and supports a high concentration of species richness and endemism for plants and terrestrial vertebrates (amphibians, birds, and mammals). In the case of amphibians, 61 named species occurring in The Serrania de los Paraguas are recognized in the literature, which are mostly the works of J.D. Lynch and P. Ruiz-Carranza in the 1990s. During a 9-d survey in the wet season (19–27 July 2019) on the Reserva Natural Comunitaria Cerro El Ingles (one of the hills of the Serrania de los Paraguas) on the frontier between Choco and Valle del Cauca departments, we discovered two new species of the genus Pristimantis. Both species share a divided palmar tubercle as well as a distinctive color pattern on the groin, of which both are distinctive within Pristimantis. The first new species is distinguished by its small size and having a distinctive carmine red color pattern on groin, uniform lateral fringes on fingers (no crenulated), palmar tubercle deeply bifid (or divided), advertisement call composed of a short single note distinctly pulsed, and absence of nuptial pads as well as hyperdistal tubercles, inner tarsal tubercle and fold, and partial fusion of Toe IV and V. The second new species is distinguished by having dermal ridges on scapular region, conical tubercle on upper eyelid and heel, palmar tubercle divided, differentiated tympanic membrane, males with vocal slits, orange spots on groin, advertisement call composed of distinctly pulsed 6–8 notes, and absence of dorsolateral folds as well as cranial crest, hyperdistal tubercles, and toe webbing. Considering these new species, the number of amphibians inhabiting the Serrania de los Paraguas has increased to 63 species. It is important to point out that within this outstanding species richness of amphibians, there are 10 endemic species and 17 threatened species according to the International Union for Conservation of Nature Red List (7 Critically Endangered, 5 Endangered, and 5 Vulnerable). Likewise, it is noteworthy that 29 terraranan species can be found in the Reserva Natural Comunitaria Cerro El Ingles. Thus, based on the species richness, endemism, diversity at higher taxonomic levels, and the number of threatened species, it seems reasonable to say that the Serrania de los Paraguas is a priority site for conservation of amphibians in Colombia.

Description and rediagnosis of the crested hadrosaurid (Ornithopoda) dinosaur Parasaurolophus cyrtocristatus on the basis of new cranial remains.

For nearly 60 years, skulls of Parasaurolophus species have been differentiated primarily on the basis of crest shape rather than on unique morphologic characters of other cranial elements. Complicating matters is the fact that crests dramatically change shape throughout ontogeny. Without a complete growth series, it has become difficult to assess the taxonomic distinctness of each species through the lens of allometric growth. Parasaurolophus cyrtocristatus has proven to be especially troublesome to assess because of the poorly preserved nature of the type and only skull. A new, partial skull from the Fossil Forest Member of the Fruitland Formation—the same geologic unit as the type specimen—is the first opportunity to re-diagnose this species as well as redefine the genus with many new traits. An undescribed, short-crested subadult skull from the Kaiparowits Formation of Utah previously assigned to cf. P. cyrtocristatus allows detailed comparisons to be made between the unnamed Utah taxon and the material of this species from the type locality. We find that several characteristics of the squamosal, supraoccipital, and premaxilla shared between the referred skull and the type skull are unique to P. cyrtocristatus (senso stricto) within the genus, irrespective of the overall crest shape. A phylogenetic analysis that includes six new characters posits that P. cyrtocristatus and P. tubicen are sister taxa, and that the latter does not share a closest common ancestor with the long-crested P. walkeri as previously hypothesized. This result helps to explain why both taxa are found in northeastern New Mexico, USA and in sequential geologic units (Fruitland Formation and Kirtland Formation, respectively). Additionally, the exquisitely preserved new skull provides the first opportunity to unequivocally identify the osteological make-up of the Parasaurolophus cranial crest. Unlike in previous reconstructions, the crest composition in Parasaurolophus follows what is seen in other lambeosaurines such as Corythosaurus, where the dorsal process of the premaxilla dominates the crest, with the nasal forming 80% of the ventral paired tubes, and the lateral premaxillary process acting a lateral cover between the dorsal and ventral tubes. The skull of P. cyrtocristatus is still incompletely known, so more complete material will likely reveal new features that further differentiate this species and aid in determining the pace of ornamental crest evolution.

Bimodal function of chromatin remodeler Hmga1 in neural crest induction and Wnt-dependent emigration.

During gastrulation, neural crest cells are specified at the neural plate border, as characterized by Pax7 expression. Using single-cell RNA sequencing coupled with high-resolution in situ hybridization to identify novel transcriptional regulators, we show that chromatin remodeler Hmga1 is highly expressed prior to specification and maintained in migrating chick neural crest cells. Temporally controlled CRISPR-Cas9-mediated knockouts uncovered two distinct functions of Hmga1 in neural crest development. At the neural plate border, Hmga1 regulates Pax7-dependent neural crest lineage specification. At premigratory stages, a second role manifests where Hmga1 loss reduces cranial crest emigration from the dorsal neural tube independent of Pax7. Interestingly, this is rescued by stabilized ß-catenin, thus implicating Hmga1 as a canonical Wnt activator. Together, our results show that Hmga1 functions in a bimodal manner during neural crest development to regulate specification at the neural plate border, and subsequent emigration from the neural tube via canonical Wnt signaling.

Sex and Ontogenetic Variation in the Crest of Numida meleagris: Implications for Crested Vertebrates.

Crested vertebrates are known from a wide variety of modern and fossil taxa, however, the actual formation and function of the crest is still debatable. Among modern birds, the globally distributed guinea fowl (Numida meleagris) is characterized by having a cranial bony crest (overlain by keratin), but surprisingly little is known about its development. Here, we studied the crest of 202 wild guinea fowl from the same population, using anatomical measurements as well as 2D-morphometry. Our results show that juveniles have smaller skulls than adults and have smaller, simpler crests that are visible even in very young individuals. Among adults, female skulls are smaller than males, and they have smaller, simpler shaped crests, which permit a discrimination between the sexes of 93% when the keratin is preserved with the bony crest, and of 89% when only the bony crest is available. By extrapolation, these results confirm that the crest can be used as an ontogenetic character, as well as for sex discrimination in the fossil record. Our results also show that the overlying keratin does not always mimic the underlying bony crest, which should be considered when reconstructing extinct crested vertebrates. Anat Rec, 303:1018-1034, 2020. © 2019 American Association for Anatomy.

A novel tibial tuberosity advancement technique with cranial implant fixation (TTA CF): a pilot study in sheep

BackgroundCranial cruciate ligament rupture is the most frequent orthopedic disorder in human and animals. An array of surgical techniques have been described to stabilize the stifle joint in dogs, including intraarticular stabilization, extraarticular stabilization, and tibial osteotomy techniques. Tibial plateau leveling osteotomy and tibial tuberosity advancement with a lot of modifications are the most common. In this study we report the possibility of fixing the novel titanium implant for tibial tuberosity advancement with two screws in a craniocaudal direction. The aim of our study was to improve the clinical benefit of the tibial tuberosity advancement surgical technique where an attempt was made to reduce the number of screws and obtain a strong implant fixation with minimal bone traumatization. This way of attachment allows to distribute the forces evenly on medial and lateral side of osteotomy gap.ResultsTibial tuberosity advancement with cranial implant fixation was performed in four sheep. Complete radiographic and clinical follow up was recorded. All four sheep had a complete osteotomy line healing at a mean of 10 weeks postoperative (range 8–12 weeks). None of the animals had osteotomy gap healing grades of poor. Minor complication included the minimally cracked Maquet hole on the postoperative radiographs, without displacement of the tibial crest which occurred in 2 sheep. Major complication grade 1, major complication grade 2 and catastrophic were not found.ConclusionsThe novel surgical technique for tibial tuberosity advancement with cranial implant fixation is technically comparable to the recent trend in tuberosity advancement techniques, where partial osteotomy of the cranial tibial tuberosity crest is performed. A cranial implant fixation allows to distribute the forces evenly on medial and lateral side of osteotomy gap, which may result in less number of major complications in dogs. A novel titanium implant decreases the tibial traumatisation by reducing the number of screws.

New Information on the osteology and a taxonomic revision of The genus Thalassodromeus (Pterodactyloidea, Tapejaridae, Thalassodrominae)

ABSTRACTThalassodromeus sethi (Pterodactyloidea, Tapejaridae, Thalassodrominae) is a unique pterosaur from the Romualdo Formation, Araripe Basin (Early Cretaceous, Albian). A large sagittal cranial crest (the largest known ossified crest of any pterosaur) and unusual toothless bladed jaws constitute some of its outstanding anatomical features. Its holotype (DGM 1476-R, almost complete skull and mandible in three dimensions) represents one of the largest pterosaur skulls ever found. Here, we provide a detailed osteological redescription of the holotype, which has only been preliminarily described. We also describe and depict for the first time some skeletal regions of Th. sethi, including the occiput, the palatal openings, and a dentary fragment. Finally, in the light of new information concerning this species, we revisited the specimen NMSG SAO 251093 (an incomplete mandible), also from the Romualdo Formation and originally referred to Th. sethi but recently redescribed as a new species of dsungaripterid pterosaur named Banguela oberlii. Here, the analysis of a cast (MN 4703-V) and its inclusion in a phylogenetic analysis recovered NMSG SAO 251093 within the Thalassodrominae, as a sister taxon of Th. sethi and indeed different from it at the species level. We hereby rename it Thalassodromeus oberlii, comb. nov. These considerations provide new data for discussions concerning the morphology of the Tapejaridae, the diversity of the Araripe pterosaur fauna, and the complex evolution of the pterodactyloid palatal region, as well as data for future morphofunctional studies of Thalassodromeus.SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVPCitation for this article: Pêgas, R. V., F. R. Costa, and A. W. A. Kellner. 2018. New information on the osteology and a taxonomic revision of the genus Thalassodromeus (Pterodactyloidea, Tapejaridae, Thalassodrominae). Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2018.1443273.

A new species of direct-developing frog of the genus Pristimantis (Anura: Terrarana: Craugastoridae) from Cordillera del Cóndor, Ecuador, with comments on threats to the anuran fauna of the region.

A new frog in the genus Pristimantis is described from a cloud forest on the western flanks of the Cordillera del Cóndor and eastern Andean slopes in the province of Zamora Chinchipe, southeastern of Ecuador. We inferred its phylogenetic position using DNA sequences of mitochondrial and nuclear genes. The new species is strongly supported as part of a clade that includes P. ardalonychus, P. cajamarcensis, P. ceuthospilus, P. chalceus, P. minutulus, P. luteolateralis, P. parvillus, P. ockendeni, P. unistrigatus, and P. walkeri. It can be distinguished from all other species from Cordillera del Cóndor and congeneric species by the unique combination of the following characters: (1) iris light blue with black reticulations; (2) skin of dorsum finely shagreen with scattered pustular tubercles and absence of dorsal folds; (3) tympanic membrane and tympanic annulus visible; (4) snout rounded in dorsal and lateral view; (5) upper eyelid bearing two or three enlarged subconical tubercles; (6) cranial crest absent; (7) males lacking vocal sac and slits; and (8) venter uniformly bright red, light red, salmon or orange. The new species is most closely related to P. ardalonychus, P. cajamarcensis, P. ceuthospilus, P. ockendeni and P. unistrigatus. We consider the new species to be Endangered following IUCN criteria because it has been severely affected by large scale open-pit mining in some localities. Currently, the amphibian fauna of the Cordillera del Cóndor and nearby protected areas are threatened by large-scale copper and gold mining projects with devastating effects on ~20 species, including several undescribed ones.

Anhanguera taxonomy revisited: is our understanding of Santana Group pterosaur diversity biased by poor biological and stratigraphic control?

BackgroundAnhanguerids comprise an important clade of pterosaurs, mostly known from dozens of three-dimensionally preserved specimens recovered from the Lower Cretaceous Romualdo Formation (northeastern Brazil). They are remarkably diverse in this sedimentary unit, with eight named species, six of them belonging to the genus Anhanguera. However, such diversity is likely overestimated, as these species have been historically diagnosed based on subtle differences, mainly based on the shape and position of the cranial crest. In spite of that, recently discovered pterosaur taxa represented by large numbers of individuals, including juveniles and adults, as well as presumed males and females, have crests of sizes and shapes that are either ontogenetically variable or sexually dimorphic.MethodsWe describe in detail the skull of one of the most complete specimens referred to Anhanguera, AMNH 22555, and use it as a case study to review the diversity of anhanguerids from the Romualdo Formation. In order to accomplish that, a geometric morphometric analysis was performed to assess size-dependent characters with respect to the premaxillary crest in the 12 most complete skulls bearing crests that are referred in, or related to, this clade, almost all of them analyzed first hand.ResultsGeometric morphometric regression of shape on centroid size was highly statistically significant (p = 0.0091) and showed that allometry accounts for 25.7% of total shape variation between skulls of different centroid sizes. Premaxillary crests are both taller and anteroposteriorly longer in larger skulls, a feature consistent with ontogenetic growth. A new diagnosis is proposed for Anhanguera, including traits that are nowadays known to be widespread within the genus, as well as ontogenetic changes. AMNH 22555 cannot be referred to “Anhanguera santanae” and, in fact, “Anhanguera santanae”, “Anhanguera araripensis”, and “Anhanguera robustus” are here considered nomina dubia.DiscussionHistorically, minor differences in crest morphology have been used in the definition of new anhanguerid species. Nowadays, this practice resulted in a considerable difficulty in referring well-preserved skulls into known taxa. When several specimens are analyzed, morphologies previously believed to be disparate are, in fact, separated by a continuum, and are thus better explained as individual or temporal variations. Stratigraphically controlled excavations on the Romualdo Formation have showed evidence for faunal turnover regarding fish communities. It is thus possible that some of the pterosaurs from this unit were not coeval, and might even represent anagenetic morphotypes. Unfortunately, amateur collecting of Romualdo Formation fossils, aimed especially at commerce, resulted in the lack of stratigraphic data of virtually all its pterosaurs and precludes testing of these further hypotheses.

Premaxillary crest variation within the Wukongopteridae (Reptilia, Pterosauria) and comments on cranial structures in pterosaurs.

Cranial crests show considerable variation within the Pterosauria, a group of flying reptiles that developed powered flight. This includes the Wukongopteridae, a clade of non-pterodactyloids, where the presence or absence of such head structures, allied with variation in the pelvic canal, have been regarded as evidence for sexual dimorphism. Here we discuss the cranial crest variation within wukongopterids and briefly report on a new specimen (IVPP V 17957). We also show that there is no significant variation in the anatomy of the pelvis of crested and crestless specimens. We further revisit the discussion regarding the function of cranial structures in pterosaurs and argue that they cannot be dismissed a priori as a valuable tool for species recognition.

New specimens of the crested theropod dinosaur Elmisaurus rarus from Mongolia

New specimens of Elmisaurus rarus from the Upper Cretaceous of Mongolia (Nemegt Formation) preserve bones not previously found in “elmisaurids” that help elucidate their relationships to Leptorhynchos elegans and other oviraptorosaurs. Elmisaurus rarus and the North American Leptorhynchos elegans are known from numerous but incomplete specimens that are closely related to, but nevertheless clearly distinguished from, Chirostenotes pergracilis and Epichirostenotes curriei. These specimens include the first known cranial bone attributed to Elmisaurus, the frontal, which clearly shows this animal had a cranial crest (most of which would have been formed by the nasal bones). The first vertebrae, scapula, femora, and tibiae from Elmisaurus are also described. The Elmisaurinae can be distinguished from the Caenagnathinae by the coossification of the tarsometatarsus and smaller size at maturity. Examination of oviraptorosaur hindlimbs reveals four distinct morphotypes, possibly attributable to paleoecological di...

Ranas terrestres de los Andes Surorientales de Ecuador II: Una nueva especie de <em>Pristimantis</em> verde espinosa de los bosques montanos del Parque Nacional Sangay (Anura: Craugastoridae)

Describimos una nueva especie de rana verde espinosa del género Pristimantis diagnosticada por presentar tímpano, cresta craneal, tubérculos cónicos grandes en las extremidades posteriores y anteriores y por su coloración ventral crema. Se presenta información acústica sobre los llamados de advertencia y cortejo y comparaciones detalladas de la especie nueva con algunas especies similares de los Andes de Ecuador. La nueva especie forma parte de un particular ecotipo de aproximadamente 12 especies de ranas terrestres de los bosques montanos de Ecuador agrupadas en por lo menos cuatro grupos parafíléticos de Pristimantis. La condición de cresta craneal con bordes frontoparietales elevados, sugiere una relación cercana de la nueva especie con el grupo-de-especies P. devillei.

Tres nuevas especies de ranas terrestres <em>Pristimantis</em> (Anura: Craugastoridae) de lacuenca alta del Río Pastaza, Ecuador

Describimos tres nuevas especies de ranas terrestres Pristimantis de los bosques siempreverde montanos circundantes al Volcán Tungurahua en la cuenca alta del Rio Pastaza, estribaciones orientales de Ecuador. La primera especie se diferencia por la distintiva forma de sus dígitos (alargados, estrechos y con discos solo un poco más anchos que los dedos); la segunda exhibe cresta craneal y presenta tamaño corporal menor a 31 mm; y la tercera es espinosa y exhibe un distintivo patrón de coloración rojo-vino finamente delineado con crema.

Neurodevelopment. Parasympathetic ganglia derive from Schwann cell precursors.

Neural crest cells migrate extensively and give rise to most of the peripheral nervous system, including sympathetic, parasympathetic, enteric, and dorsal root ganglia. We studied how parasympathetic ganglia form close to visceral organs and what their precursors are. We find that many cranial nerve-associated crest cells coexpress the pan-autonomic determinant Paired-like homeodomain 2b (Phox2b) together with markers of Schwann cell precursors. Some give rise to Schwann cells after down-regulation of PHOX2b. Others form parasympathetic ganglia after being guided to the site of ganglion formation by the nerves that carry preganglionic fibers, a parsimonious way of wiring the pathway. Thus, cranial Schwann cell precursors are the source of parasympathetic neurons during normal development.