Cranial Crests Research Articles

Case Report on a Supracondylar Process of the Humerus: Morphological and Morphometric analysis

The supracondylar process is a rare anatomical variation characterized by an irregular bone prominence with a variable size. Found in the anteromedial part of the distal region of the humerus, can compress the median nerve and other structures. The aim of this paper was to perform a morphological and morphometric evaluation of this variation in a right dry humerus. Faces, margins, and shape of the process were observed. Measurements was taken from the process and the entire bone. The apex of the process points toward the transition between the trochlea and the humeral capitulum. The bony spicule was 6.24 mm long. The base of the spicule measured 6.80 mm in length and 4.18 mm in width. Longitudinal crests associated with the base of the process and a deep longitudinal depression were observed. The combined longitudinal length of the caudal and cranial crests together was 32.37 mm. The distance from the bone spicule to the medial epicondyle was 65.29 mm. In pathological cases, vascular disturbances, sensory deficits, and decreased muscle strength can be observed. A comprehensive description of this variation is crucial for enhancing current knowledge and awareness in clinical practice, as it aids in accurate diagnosis and treatment.

Cretaceous pterosaur history, diversity and extinction

Abstract Pterosaurs, the first vertebrates to evolve powered flight, dominated Mesozoic skies from the Late Triassic to the end Cretaceous, a span of around 154 Myr (∼220–66 Ma). They achieved their greatest diversity in the mid-Cretaceous and had become globally distributed, even occurring at high latitudes and in a wide range of habitats. The pterosaur record is dominated by occurrences in conservation Lagerstätten in just a handful of countries and a narrow range of temporal windows, most notably China, Germany and Brazil, and the Middle–Upper Jurassic and mid-Cretaceous. During the Cretaceous, two major pterosaur clades evolved edentulism, such that by the end of the Cretaceous, no toothed pterosaurs survived, having become extinct by the mid-Cenomanian. A distinctive aspect of pterosaur evolution during the mid-Cretaceous was the achievement of gigantic wingspans, perhaps in excess of 10 m, hyper-elongation of the neck vertebrae in Azhdarchidae, and the evolution of highly elaborate cranial crests. For many years, pterosaur diversity in the terminal stage of the Late Cretaceous was regarded as low, but discoveries in the last few decades have indicated pterosaur taxic diversity remained high until the end Maastrichtian, although morphological diversity may have been low. The demise of the Pterosauria at the K/Pg boundary was most likely due to the same causes as the coeval dinosaur extinction associated with the Chicxulub bolide impact and its environmental repercussions. Faunal replacement by avians is no longer considered a significant factor in pterosaur extinction.

Single-cell RNA-seq of in vitro expanded cells from cranial neural crest reveals a rare odontogenic sub-population.

Ecto-mesenchymal cells of mammalian tooth germ develops from cranial neural crest cells. These cells are recognised as a promising source for tooth development and regeneration. Despite the high heterogeneity of the neural crest, the cellular landscape of in vitro cultured cranial neural crest cells (CNCCs) for odontogenesis remains unclear. In this study, we used large-scale single-cell RNA sequencing to analyse the cellular landscape of in vitro cultured mouse CNCCs for odontogenesis. We revealed distinct cell trajectories from primary cells to passage 5 and identified a rare Alx3+/Barx1+ sub-population in primary CNCCs that differentiated into two odontogenic clusters characterised by the up-regulation of Pax9/Bmp3 and Lhx6/Dmp1. We successfully induced whole tooth-like structures containing enamel, dentin, and pulp under the mouse renal capsule using in vitro cultured cells from both cranial and trunk neural crests with induction rates of 26.7% and 22.1%, respectively. Importantly, we confirmed only cells sorted from odontogenic path can induce tooth-like structures. Cell cycle and DNA replication genes were concomitantly upregulated in the cultured NCCs of the tooth induction groups. Our data provide valuable insights into the cell heterogeneity of in vitro cultured CNCCs and their potential as a source for tooth regeneration.

Correlation of skull morphology and bite force in a bird-eating bat (Ia io; Vespertilionidae)

BackgroundGenetic and ecological factors influence morphology, and morphology is compatible with function. The morphology and bite performance of skulls of bats show a number of characteristic feeding adaptations. The great evening bat, Ia io (Thomas, 1902), eats both insects and birds (Thabah et al. J Mammal 88: 728-735, 2007), and as such, it is considered to represent a case of dietary niche expansion from insects to birds. How the skull morphology or bite force in I. io are related to the expanded diet (that is, birds) remains unknown. We used three-dimensional (3D) geometry of the skulls and measurements of bite force and diets from I. io and 13 other species of sympatric or closely related bat species to investigate the characteristics and the correlation of skull morphology and bite force to diets.ResultsSignificant differences in skull morphology and bite force among species and diets were observed in this study. Similar to the carnivorous bats, bird-eaters (I. io) differed significantly from insectivorous bats; I. io had a larger skull size, taller crania, wider zygomatic arches, shorter but robust mandibles, and larger bite force than the insectivores. The skull morphology of bats was significantly associated with bite force whether controlling for phylogeny or not, but no significant correlations were found between diets and the skulls, or between diets and residual bite force, after controlling for phylogeny.ConclusionsThese results indicated that skull morphology was independent of diet, and phylogeny had a greater impact on skull morphology than diet in these species. The changes in skull size and morphology have led to variation in bite force, and finally different bat species feeding on different foods. In conclusion, I. io has a larger skull size, robust mandibles, shortened dentitions, longer coronoid processes, expanded angular processes, low condyles, and taller cranial sagittal crests, and wider zygomatic arches that provide this species with mechanical advantages; their greater bite force may help them use larger and hard-bodied birds as a dietary component.

An unusual ‘shovel-billed’ dinosaur with trophic specializations from the early Campanian of Trans-Pecos Texas, and the ancestral hadrosaurian crest

We describe a new genus and species of hadrosaurid dinosaur, Aquilarhinus palimentus, from the lower shale member of the Aguja Formation (lower Campanian) of Big Bend National Park, south-western Texas. This species is characterized by several autapomorphies of the facial skeleton and mandible, including a crest composed of broadly arched nasals. Notably, the symphyseal processes of the dentary are elongated and reflected dorsally, causing the dentaries to meet with a ‘W’-shaped anterior profile. A hypothesized shovel-shaped ‘bill’, associated with widening of the skull, in A. palimentus might have been used in shovelling out and scooping up semiaquatic vegetation. This animal is otherwise superficially similar to kritosaurins like Gryposaurus but differs in the retention of key plesiomorphic character states in the maxilla and jugal. Phylogenetic analysis reveals Aquilarhinus to be a non-saurolophid hadrosaurid allied to Latirhinus from the late Campanian of Mexico, which bears a similar broadly arched nasal. The recognition of this lineage adds to the diversity of non-saurolophid hadrosaurids and points to the existence of a hitherto unknown diversity of ‘duck-billed’ dinosaurs outside of the saurolophine-lambeosaurine radiation. Cranial crests were ancestral for early hadrosaurids and evolved before the saurolophid radiation. Ancestrally, crests were ‘solid’, and consisted of arched nasals. These were retained among kritosaurins and subsequently modified into the diverse crest morphologies observed among derived saurolophines. Lambeosaurine ‘hollow-crested’ crest morphology departed from the ancestral, ‘solid-crested’ pre-saurolophid condition early following the origin of that clade.http://www.zoobank.org/urn:lsid:zoobank.org:pub:F7CE1BE7-1A76-4628-8510-93C37A1A807E

Similar skull morphologies are found in seals and sea lions due to combat or to feeding style

Many carnivorans exhibit sexual dimorphism in the skeleton, variously due to aggression, feeding styles, or other behaviors. Some species of seals and sea lions only use vocal displays between males for access to mates and territory, but other species engage in outright combat between individuals. Species with higher intraspecific aggression are characterized by skulls with more crest development for the emplacement of biting muscles than less‐aggressive species. Are these more prominent skull characteristics due entirely to levels of aggression?To answer this, we observed the placement of 26 bony landmarks on 14 species of seals and sea lions (n = 45, including 29 adult males and 16 adult females) using a geometric morphometric approach. We categorized these species by reported level of intraspecific aggression and diet. We found that skull proportions did differ between males from more‐aggressive and less‐aggressive categories. Particularly, we found that the skulls of most less‐aggressive species were characterized by little dimorphism between sexes, a more rounded cranium, and a relatively narrow zygomatic width. On the other hand, within more‐aggressive species, notable dimorphism in skull morphology existed between males and females. Most males from highly‐aggressive species developed more prominent nuchal and sagittal crests and wider zygomatic arches while females retained a more rounded skull morphology similar to less‐aggressive species.However, there were species that were categorized as being less‐aggressive but still possessed the more developed skull morphology of more‐aggressive species. For example, the Weddell seal and the leopard seal both developed wider zygomatic arches and taller cranial crests and they also lack notable intraspecific sexual dimorphism, but are not reported to engage in frequent combat. We propose that their skull morphologies are more likely due to the emplacement of larger muscles for feeding on larger prey.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

A new minute Pristimantis (Amphibia: Anura: Strabomantidae) from the Andes of southern Ecuador.

We describe a new rainfrog species (Pristimantis), from the wetland complex Oña, Nabón, Saraguro and Yacuambi, in the Andes of southern Ecuador, at altitudes ranging between 3000–3400 m a.s.l. Pristimantis tiktik sp. nov. is a small frog, displaying sexual dimorphism (the males with dorsum of various shades of gray, brown, orange or green and a whitish or pinkish yellow venter; females with brownish gray or gray dorsum and a reticulated white and black venter), with SVL ranging between 19.7–20.4 mm in females (n = 3) and 16.1–18.4 mm in males (n = 6). The skin on dorsum is tuberculated, that on venter is coarsely areolate, dorsolateral folds are absent, tympanic membrane is absent but the tympanic annulus is evident, cranial crests are absent, discs on fingers just slightly expanded, heel is lacking enlarged tubercles, inner edge of tarsus is bearing a long fold, Toe V is slightly longer than Toe III and the iris coloration is bronze with fine black reticulations. The males have a large subgular vocal sac that extends onto the chest and vocal slits but lack nuptial pads. The unique advertisement call consists of long duration series of periodically repeated clicks: “tik”. Molecular analyses place the new species in the recently resurrected P. orestes group, as the sister species of the assemblage that contains P. bambu, P. mazar, P. simonbolivari and an undescribed species.

A new species of semiarboreal toad of the Rhinella festae group (Anura, Bufonidae) from the Cordillera Azul National Park, Peru.

A new semiarboreal species of the Rhinella festae group is described from montane forests of the Cordillera Azul National Park between 1245 and 1280 m a.s.l. in the Cordillera Oriental, San Martín region, northern Peru. The new species is morphologically and genetically compared with members of the Rhinella acrolopha group (former genus Rhamphophryne) and members of the R. festae group. The new species is characterized by its large size (female SVL 47.1–58.3 mm, n = 4), eight presacral vertebrae, fusion of the sacrum and coccyx, long protuberant snout, snout directed slightly anteroventral in lateral view, cranial crests moderately developed, absence of occipital crest, presence of tympanic membrane, dorsolateral rows of small conical tubercles extending from parotoid gland to groin, hands and feet with long digits, fingers basally webbed and toes moderately webbed. Phylogenetically it is a member of the R. festae group which is most closely related to R. chavin and R. yanachaga from Peru. Morphologically the new species shares similarities with R. tenrec and R. truebae, members of the R. acrolopha group from Colombia.

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.

A Basal Tapejarine (Pterosauria; Pterodactyloidea; Tapejaridae) from the Crato Formation, Early Cretaceous of Brazil.

A three-dimensional and almost complete pterosaur mandible from the Crato Formation (Early Cretaceous of Northeastern Brazil), Araripe Basin, is described as a new species of a tapejarine tapejarid. Tapejarines are a particular group of toothless pterosaurs, characterized by well-developed cranial crests, downturned rostra, and have been proposed to represent frugivorous flying reptiles. Though comparatively well represented and distributed, the evolutionary history of the group is still poorly known, and the internal relationships of its members are not well understood. The new species here reported, named Aymberedactylus cearensis gen. et sp. nov., adds new data concerning the evolution of the group, concerning their morphology and geographical origin. It differs from known tapejarids due to its unusually elongate retroarticular process and a shallow fossa on the splenial exhibiting distinctive rugose texture. Furthermore, it exhibits a suite of basal and derived conditions within the Tapejaridae, demonstrating how their morphological traits probably evolved and that these forms were even more diverse than already acknowledged. The discovery of Aymberedactylus cearensis sheds new light on the evolutionary history of the Tapejarinae.

Otra nueva especie de rana <em>Pristimantis</em> (Anura: Terrarana) de las estribaciones occidentales del Volcán Pichincha, Ecuador

Describimos una nueva especie de rana terrestre Pristimantis de las estribaciones occidentales de los Andes de Ecuador, en la provincia de Pichincha, Ecuador. La especie forma parte del grupo de especies P. devillei y se caracteriza por presentar cresta craneal elevada frontoparietalmente, tímpano oculto, pliegues dorsolaterales, flancos glandulares, y tubérculos subcónicos en el párpado, región ulnar y talón.

Model‐Based Identification of Mechanical Characteristics of Sinosaurus (Theropoda) Crests

AbstractThe paired cranial crests of Sinosaurus (Theropoda) have been hypothesized as too weak to resist mechanical loads during combat. Finite element analysis (FEA) is used to test this hypothesis, first with geometry obtained through direct laser scanning of a well‐preserved fossil of the crest, and then with two conceptual FE models of both crests analyzing the structure‐deformation effects of fenestration. In the original fossil model, under direct loading on the dorsal faces of the crest, we found that the areas surrounding cavities on the crest experience shear stress that implies a high chance of material failure – the fracture of bone. In the conceptual model, a series of computational studies were conducted with varying loading directions. One simulation found that the shear stress and strain in the material around the cavity presented more deformation compared with the conceptual model without the cavities, and under this morphologically realistic scenario the loading conditions would result in local bone fractures. These model‐based computational results indicate that the crest could not resist high loads, because it could not effectively decentralize the loading stress. Future investigations need to focus on more comprehensive computational experiments with more conditions, e.g. dynamical loading conditions, and direct palaeontological evidence.

Sexually Dimorphic Tridimensionally Preserved Pterosaurs and Their Eggs from China

The pterosaur record is generally poor, with little information about their populations, and pterosaur eggs are even rarer, with only four isolated and flattened eggs found to date. We report here a population of a new sexually dimorphic pterosaur species (Hamipterus tianshanensis gen. et sp. nov.), with five exceptionally well-preserved three-dimensional eggs, from the Early Cretaceous deposit in northwestern China. About 40 male and female individuals in total were recovered, but the actual number associated might be in the hundreds. All of the discovered skulls have crests, which exhibit two different morphologies in size, shape, and robustness. The eggs show pliable depressions with cracking and crazing on the outer surface. The eggshell, observed by scanning electron microscopy and energy-dispersive spectroscopy, comprises a thin calcareous external hard shell followed by a soft membrane. These fossils shed new light on the reproductive strategy, ontogeny, and behavior of pterosaurs. The cranial crests show sexually dimorphic morphologies, with presumed males and females differing in crest size, shape, and robustness. Ontogenetic variation is reflected mainly in the expansion of the rostrum. The eggs have some external rigidity of the general pliable eggshell, and the microstructure of the eggshell is similar to that of some modern "soft" snake eggs. We suggest that this new pterosaur nested in colonies and thus exhibited gregarious behavior, a possible general trend for at least derived pterodactyloid pterosaurs.

Skull variation and the shape of the sagittal premaxillary crest in anhanguerid pterosaurs (Pterosauria, Pterodactyloidea) from the Araripe Basin, Northeast Brazil

Sagittal cranial crests are evident in several groups of pterosaurs, although their exact function has still not been determined. One of the most distinctive features of the Anhangueridae is a sagittal premaxillary crest on the anterior portion of the skull. A comparison of the skulls of anhanguerids revealed that they all have similar skull and crests shapes. In this paper, six anhanguerids from Araripe Basin were analysed using bidimensional geometric morphometrics. As a result, the taxa were arranged in two groups and two isolated taxa in the morphospace: elongated skulls, with crests high and expanded, representing 40% of the skull length; and median size skulls; and low and short crests starting posteriorly on the region of the seventh and fourth pairs of alveoli. Some of these groupings also share a phylogenetic relationship. Despite this separation in morphospace, the difference between the morphology of the crest was not as striking as in other pterodactyloid pterosaurs. Crest variation in Anhangueridae presented in this paper is considered as non-specific, with some patterns of similarity, such as the shape and the beginning of this structure on the premaxilla. In addition, the presence of positive allometric growth in the skull was observed and no trend in sexual dimorphism could be pointed.

New Material of Feilongus (Reptilia: Pterosauria) from the Lower Cretaceous Jiufotang Formation of Western Liaoning

AbstractBased on a new nearly naturally preserved skull and four cervical vertebrae of the pterosaur Feilongus sp. from the lower Cretaceous Jiufotang Formation of Beipiao, western Liaoning province, northeastern China, the diagnosis of Feilongus is amended. The revised diagnosis notes long, curved, needle‐shaped teeth that are confined to the jaw far anterior to the nasoantorbital fenestra; posterior teeth that are slightly smaller than the anterior teeth; cervical vertebrae elongated with a ratio of length to width greater than 5; tooth number of about 78; and two cranial sagittal crests.

A new species of the Rhinella margaritifera species group (Anura, Bufonidae) from the montane forest of the Selva Central, Peru.

We describe a new species of the bufonid toad genus Rhinella from transition montane forest of the buffer zones of the Yanachaga-Chemillén National Park and the Pui Pui Protected Forest (eastern slopes of Andes, Selva Central, Peru). The new species belongs to the Rhinella margaritifera species group (confirmed by mtDNA data) and differs from all its members by the absence of tympanic membrane and tympanic annulus. It is characterized by medium size (SVL 57.5–65.5 mm, n = 5), moderately developed cranial crests, absence of neural crest of vertebrae, absence of bone protrusion at angle of jaw, presence of lateral rows of enlarged tubercles, and absence of subgular vocal sac and vocal slits in males. In addition, based on the molecular phylogenetic analyses of selected Rhinella species we propose the monophylum containing R. chavin, R. festae, R. macrorhina, R. manu, R. nesiotes, R. rostrata, and R. yanachaga as a new species group under the name Rhinella festae species group.

A new unusual tapejarid (Pterosauria, Pterodactyloidea) from the Early Cretaceous Romualdo Formation, Araripe Basin, Brazil

ABSTRACTA new unusual tapejarid pterosaur from the Early Cretaceous Romualdo Formation (Araripe Basin, Brazil) is described, based on a skull, lower jaw and some postcranial elements.Caupedactylus ybakagen. et sp. shows the typical high nasoantorbital fenestra of the Thalassodrominae but lacks a palatal ridge, and shares with the Tapejarinae several features, including a downturned rostral end, allowing its allocation to that clade. Furthermore, the new species differs in having an anteriorly and posteriorly expanded premaxillary sagittal crest, the lacrimal process of the jugal strongly inclined, and a slit-like postpalatine fenestra, among other characters. The region of the left jugal-quadratojugal-quadrate shows a pathology that is likely the result of an infection. The lateral surface of the premaxillary crest presents grooves that were interpreted in other pterosaurs as impressions of blood vessels, corroborating growing evidence that cranial crests could have been involved in thermoregulation. Also, the new species has a well-preserved palate with a large palatine forming the anterior region of the choanae and the postpalatine fenestra and a secondary subtemporal fenestra. Since the latter has been regarded as unique to non-pterodactyloids, its occurrence inCaupedactylusdemonstrates that the evolution of palatal region in pterosaurs is more complex than previously thought.

Oscillation of an Anuran Hybrid Zone: Morphological Evidence Spanning 50 Years

BackgroundThe hybrid zone between the primarily forest-dwelling American toad, Anaxyrus americanus, and the prairie-adapted Canadian toad, A. hemiophrys, in southeastern Manitoba is known to have shifted its position during the past 50 years. Hybrid zones are areas of interbreeding between species and their movement across a landscape should reflect their underlying dynamics and environmental change. However, empirical demonstrations of hybrid zone movements over long periods of time are rare. This hybrid zone is dominated by individuals of intermediate morphology and genetic composition. We sought to determine if it had continued to move and if that movement was associated with shifts in habitat, as predicted.Methodology/Principle FindingsWe used variation in the toads’ most diagnostic morphological feature, the separation between their interorbital cranial crests, to determine the geographic position of the hybrid zone center at four times between 1960 and 2009 using maximum likelihood methods. The hybrid zone center moved west by 38 km over 19 years and then east again by 10 km over the succeeding 29 years. The position of the hybrid zone did not track either the direction or the magnitude of movement of the forest-prairie habitat transition over the same time period.Conclusions/SignificanceThis is the first reported evidence of oscillation in the position of a hybrid zone. The back and forth movement indicates that neither species maintains a selective advantage over the other in the long term. However, the movement of the hybrid zone was not bounded by the breadth of the habitat transition. Its oscillation suggests that the hybrid zone is better described as being elastically tethered to the habitat transition.

The Flight Dynamics of Tapejara, a Pterosaur From the Early Cretaceous of Brazil with a Large Cranial Crest

Abstract:Tapejara wellnhoferi, a small azhdarchoid pterodactyloid from the Early Cretaceous Santana Formation of Brazil, provides critical information about the aerodynamic function of its spectacular head crest. The cranial crests in pterodactyloids were sexually dimorphic and are thought to have evolved in adult males in response to female mate choice. However, the location of cranial crests in front of the center of gravity would create instability in the yaw axis during flight and may seem like a handicap. Vertically aligned webbed feet probably suppressed the yawing rotations and instability from the crest. Here we show that the crest functioned as a front rudder to make agile turn and mediate flight control. A computer simulation model suggests that Tapejara had a large excess of muscle power available above the power required for continuous flapping flight. It could easily takeoff from a perch, ground, or water surface and land safely on the ground. It was an excellent glider with a gliding angle close to 4° and a cruising speed of 27 km/h. Tapejara could soar efficiently on the windward side of cliffs or circle on rising thermals over tropical waters for efficient long‐distance flight. Various control surfaces in the wings of Tapejara analogous to the slat, aileron, elevator, fin, rudder, and horizontal stabilizer of an aircraft made pterodactyloids versatile flyers.

A New Crested Pterosaur from the Early Cretaceous of Spain: The First European Tapejarid (Pterodactyloidea: Azhdarchoidea)

BackgroundThe Tapejaridae is a group of unusual toothless pterosaurs characterized by bizarre cranial crests. From a paleoecological point of view, frugivorous feeding habits have often been suggested for one of its included clades, the Tapejarinae. So far, the presence of these intriguing flying reptiles has been unambiguously documented from Early Cretaceous sites in China and Brazil, where pterosaur fossils are less rare and fragmentary than in similarly-aged European strata.Methodology/Principal Findings Europejara olcadesorum gen. et sp. nov. is diagnosed by a unique combination of characters including an unusual caudally recurved dentary crest. It represents the oldest known member of Tapejaridae and the oldest known toothless pterosaur. The new taxon documents the earliest stage of the acquisition of this anatomical feature during the evolutionary history of the Pterodactyloidea. This innovation may have been linked to the development of new feeding strategies.Conclusion/SignificanceThe discovery of Europejara in the Barremian of the Iberian Peninsula reveals an earlier and broader global distribution of tapejarids, suggesting a Eurasian origin of this group. It adds to the poorly known pterosaur fauna of the Las Hoyas locality and contributes to a better understanding of the paleoecology of this Konservat-Lagerstätte. Finally, the significance of a probable contribution of tapejarine tapejarids to the early angiosperm dispersal is discussed.