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High-resolution computed tomography (CT) scans through two fossilized lesions in hadrosaur bone guided paleohistological and stable-isotopic sampling to examine the stages and structures of bone repair in hadrosaurs. Two hadrosaur caudal neural spines from late Cretaceous bonebeds in Alberta, Canada, exhibit calluses produced during healing of traumatic fractures. In both CT scans and paleohistologic sections, these specimens display a combination of reptilian and non-reptilian characteristics in dinosaurian skeletal repairs. In one specimen the callus is dominated by a trabecular lattice that lacks signs of remodeling. Trabeculae in this callus are distinctively textured by clusters of densely packed, randomly oriented lacunae, two orders of magnitude larger than typical osteocyte lacunae and reminiscent of hypertrophic chondrocytes in cartilage of reptiles. The lattice represents early mineralization of callus tissue, and it preserves a δ18O value in mineral phosphate 0.6‰ lower than adjacent non-pathologic cortex, suggesting that the repair site was ∼2.5°C warmer than uninjured tissue. The elevated temperature results from locally enhanced cellular activity around the fracture, a common consequence of bone injury in vertebrates. In the second specimen, the callus has been extensively remodeled, with several areas transformed to dense secondary Haversian bone typical of modern birds. Stable oxygen isotopes in bone phosphate of this callus show no isotopic offset, indicating that this injury had progressed further through the healing process before the animal's death. High-resolution CT scans reveal tissue density and structure differences between the two lesions, suggesting that this technology could eventually be used to gauge relative healing without altering unique fossil specimens.
The Palaeospinacidae are a highly diverse clade (> 30 species) within the Synechodontiformes, which are considered to be a monophyletic group of basal galeomorph sharks. Four genera, Macrourogaleus, Paraorthacodus, Palidiplospinax, and Synechodus, are included in the Palaeospinacidae, ranging in age from the Early Permian to the Paleogene. So far, the only described palaeospinacids from the Upper Jurassic lithographic limestones of southern Germany are several specimens of Macrourogaleus from the Solnhofen area, and a single one of Paraorthacodus jurensis from Nusplingen. The presence of Synechodus in the Upper Jurassic of southern Germany was only indicated by a single figured but undescribed tooth. An incomplete and disarticulated skeleton of a small neoselachian shark and additional isolated teeth from the Kimmeridgian of Baden-Württemberg represent the first record of Synechodus in the Upper Jurassic lithographic limestones of Germany. The skeleton includes parts of the vertebral column, the left palatoquadrate, the right Meckel's cartilage, several fragments of calcified cartilage of the cranial skeleton, 32 teeth, and several placoid scales. The dental features unique to this species include a slender and sub-triangular main cusp, a crown ornamentation consisting of long ridges, a basal reticulation pattern that does not extend basally to the crown-root boundary, and a basal labial depression of the main cusp in anterior teeth.
Ptychodus (Elasmobranchii: Ptychodontidae) is an enigmatic durophagous shark known from Cretaceous marine deposits nearly worldwide based primarily on isolated teeth. Here, we describe a specimen of P. occidentalis Leidy from the Greenhorn Limestone (middle Cenomanian—early Turonian) in Nebraska, U.S.A. The specimen does not offer any new taxonomic information concerning the unresolved ordinal placement of Ptychodus. However, it is significant because it preserves a partial skull including teeth, incomplete jaws, and neurocranial fragments as well as placoid scales and vertebrae, all of which provide a wealth of new anatomical information. The specimen contains at least 267 teeth and shows that the two dental plates are anteroposteriorly elongate. The partial paired Meckel's cartilages show a long, fused jaw symphysis and elongate jaw rami. The distribution of presumed neurocranial fragments and placoid scales with respect to the position of the dental plates suggests that the shark had a broad head with a narrow, subterminal mouth. The morphology of placoid scales suggests that the shark was a rather sluggish swimmer and had a stout, streamlined body similar to that in the extant orectolobiform sharks (e.g., Ginglymostoma). Based on the jaw length, the individual of P. occidentalis was approximately 2 m in total length (TL), while some of the largest Ptychodus known from younger Cretaceous horizons in the North American Western Interior likely attained at least 7 m TL. Ptychodus occidentalis is inferred to be an opportunistic generalist (rather than a hard prey specialist) that fed on a variety of readily available prey using inertial suction feeding.
Megapiranha paranensis from the Upper Miocene of Argentina is described based on a large, partially toothed premaxilla as a new genus and species of serrasalmid fish (pacus and piranhas) and is diagnosed and distinguished from other serrasalmids based on the following unique combination of characters: seven premaxillary teeth with the first four arranged in a shallow, zig-zag row, and third tooth shaped similarly to the fourth and fifth teeth; large, triangular, unicuspid crowns with finely serrated cutting edges. The phylogenetic position of Megapiranha was determined by parsimony analysis of morphological characters. The resulting analysis recovered Megapiranha as sister to the piranha clade (Pygopristis, Pygocentrus, Pristobrycon, Serrasalmus) and is supported by two synapomorphies: (1) teeth triangular in labial view with well-developed cutting edges, and (2) serrations along both sides of tooth cutting edges. The pattern of tooth placement exhibited by the fossil Megapiranha is intermediate between the double-row condition of pacus and the single-row condition of piranhas, and suggests how the double row of teeth may have been rearranged into a single row in the evolution of piranhas.
Three extraordinarily well-preserved skeletons and skeleton parts of an Early Miocene sunfish are described. These unique fossils allow a precise osteological description of one of the largest if not the largest sunfish (320 cm) known so far and represent one of the largest teleost fossils of the Cenozoic Era. This new sunfish genus is the sister-taxon of the extant MolaMasturus clade and, together with these two genera, forms the sister-clade of Ranzania. The radiation of modern-type sunfishes therefore already had occurred during Oligocene times. The finding from the earliest Miocene narrows the gap between the oldest known Eocene primitive sunfish and the Middle and Upper Miocene records, which are all referable to extant genera. Austromola is introduced as a new genus of the family Molidae; Austromola angerhoferi is described as a new species.
A fossil ceratioid anglerfish of the extremely rare genus Acentrophryne is described from a single specimen collected from the Miocene (upper Mohnian) diatomaceous metric and meristic features suggest a close similarity with the extant Acentrophryne longidens from which it apparently differs in having a longer illicium. The fossil provides the first osteological information about this genus of the family Linophrynidae. The analysis of the present and past distribution of the very rare material assigned to Acentrophryne has revealed that it is restricted to the tropical and subtropical sectors of the Eastern Pacific. Moreover, living and fossil representatives of this genus appear to be exclusive of the oxygen-depleted deep waters associated with the upwelling phenomena in the Eastern Pacific.
A newly discovered, small lepospondyl from the Early Permian of Oklahoma is demonstrated to be a new genus and species of ostodolepid ‘microsaur’ and is given the name Nannaroter mckinziei. The holotype and only known specimen comes from the Permian-aged fissure fill deposits in the Ordovician limestone from the Dolese Brothers Limestone Quarry, the richest, most diverse Paleozoic assemblage of exclusively terrestrial vertebrates. The superbly preserved skull is identified as the smallest known ostodolepid for its characteristic cranial architecture. Like all ostodolepids, it has a wedge-shaped skull with a high posterior profile and broad occipital surface, and a lower temporal emargination. Like ostodolepids, gymnarthrids, pantylids, and Rhynchonkos, the anterior rostrum is overturned, producing a recumbent snout. Despite its small size, Nannaroter has a massively ossified skull with deeply interlocking sutures designed to tightly resist anteroposteriorly directed forces. Medial laminae are present on all circumorbital bones producing thick orbital walls, and there is a well-developed ventral process of the frontal that is suturally attached to the sphenethmoid portion of the braincase anterodorsally. In addition, a massive, triangular pterygoid-epipterygoid complex reinforces the posterolateral wall of the braincase and contacts the tabular and parietal portion of the dermatocranium. This description is the first part of a revision of the ostodolepids, which will explore adaptations in amphibians to a fossorial lifestyle.
The anatomy of individuals is described from a ‘pelycosaur’ aggregation preserving two age classes, from the Middle Permian of the South African Karoo Basin, that have been referred to Heleosaurus scholtzi. These skeletons allow the recognition of new features for H. scholtzi, including a strong anterior inclination of the occiput, exclusion of the quadratojugal from the temporal fenestra, a maxilla-prefrontal contact, and a maxilla-quadratojugal contact. In addition to some of these features, the absence of an anterodorsal contact between the squamosal and the jugal allows us to assign H. scholtzi to the varanopid clade Mycterosaurinae. Phylogenetic analysis of Varanopidae using an augmented data matrix from the literature positions Heleosaurus as the sister taxon of Elliotsmithia within the varanopid subfamily Mycterosaurinae. Both this sister-group relationship and the monophyly of Mycterosaurinae are weak and collapse with one extra step. Many of the clades discovered in the analysis exhibit the same support level, however, indicating that further studies on varanopids are needed.
A large collection of recently prepared, complete specimens of Keichousaurus hui provides a wealth of new anatomical data for this taxon. Sexual dimorphism can be unambiguously quantified by proportions of the humerus as well as ratios of humerus length to standard length and femoral length. Multivariate (principal components and discriminant) analysis identified ratios most useful in distinguishing the sexes. Sexual maturity was reached in males at approximately 126 mm snout-vent length (SVL), and in females by 122 mm SVL. Mean SVL for mature males is approximately 161 SVL, and for mature females, at most 149 mm SVL. Although the last dimension predicts a mean hatchling SVL of approximately 50 mm based on data from extant squamates, the relationship between mean SVL of mature females and mean SVL of hatchling/neonate in squamates is quite variable. As a result, a mean value of 40.4 mm SVL for several tiny isolated individuals of Keichousaurus is well within the 95 percent confidence ellipse calculated from data from extant squamates. Therefore, there is not reason to postulate that the common occurrence of tiny individuals of between 33.5 mm and 48.2 mm SVL is the result of spontaneous abortions.
Abundant, readily identifiable, and biostratigraphically resolved specimens make mosasaurs ideal candidates to test fluxes in generic richness and morphological trends among marine vertebrates during the late Cretaceous. More than 1800 globally distributed mosasaur specimens are allocated to fifteen substage-level stratigraphically correlated assemblages. These data are quantitatively analyzed to illuminate trends within the group. Following their first appearance in the Cenomanian, mosasaurs experienced a significant radiation in the Coniacian and Santonian. Richness levels continued increasing into the Maastrichtian while mosasaurs incrementally exploited new predatory niches recognized via accumulation of novel dental morphologies. Their extinction at the end of the Cretaceous occurred at the zenith of mosasaur morphological and ecological diversity.
New material of Plioplatecarpus nichollsaeCuthbertson et al, 2007 (Squamata: Mosasauridae) clarifies many problematic features of the holotype. New observations demonstrate its unique cranial features among plioplatecarpines (=Ectenosaurus, Platecarpus and Plioplatecarpus), such as a parallel-sided frontal shield, a large, oval pineal foramen, and a highly inflated basal tubera of the basioccipital. Although the quadrate morphology is virtually identical to that of Platecarpus ictericus, Plio. nichollsae exhibits more synapomorphies with stratigraphically younger members of the genus than Platecarpus does, including newly recognized characters such as a pair of well-developed parolfactory-bulb recesses and anteriorly diverging ventro-lateral processes found on the frontal. Re-characterization of the species indicates its closest anatomical resemblance to descriptions given for the contemporary Platecarpus somenensis specimens (lower middle Campanian) from North America, which indicates that the current generic assignment for the latter taxon needs to be re-evaluated.
Previous works discussing interrelationships of squamates, mosasauroids, and aigialosaurs have alternately suggested Opetiosaurus bucchichi and Aigialosaurus dalmaticus to be accurately diagnosed, congeneric, and in some cases, conspecific taxa. Recent systematic work has shown that these two species, as basal mosasauroids, are critical to understanding the evolutionary history of mosasaurs. Because earlier attempts at descriptions of O. bucchichi have proven insufficient for systematic purposes, the specimen is redescribed here based on the counterpart skull to the holotype part specimen, revealing new anatomical details unavailable to previous workers. This comparison of O. bucchichi and A. dalmaticus reveals no morphological differences that support a generic differentiation of the two specimens assigned to these monospecific genera. The genus Opetiosaurus is therefore a junior synonym of Aigialosaurus and O. bucchichi is re-diagnosed as A. bucchichi; the species A. bucchichi is retained because some minor differences are present between the individual specimens assigned to the respective species. Incorporation of new anatomical information into a phylogenetic analysis lends support to suggestions from previous workers that the paddle-shaped limb evolved more than once within Mosasauroidea; however, the tree topologies are not robust. The results of this study indicate that the systematic relationships of halisaurine mosasaurs are of primary importance in the study of mosasauroid interrelationships.
The axial skeleton of hyposaurine dyrosaurids differs significantly from that of extant crocodylians, most notably in the height of the neural spines, the vertically oriented thoracic ribs and osteoderms that lack external keels. This indicates a different configuration of the epaxial musculature for hyposaurine dyrosaurids compared with extant crocodylians and possibly all other fossil species. In the trunk, m. transversospinalis tendons formed a tendinal lattice. M. tendinoarticularis and m. longissimus dorsi were divided into high, medially open myoseptal cones. M. iliocostalis of hyposaurine dyrosaurids was larger than in extant crocodylians and braced the arcade of the vertebral column during locomotion. The trunk bracing-system of hyposaurine dyrosaurids is referred to as a Hyposaurus-type bracing system, and is modeled as a segmented, hydraulically stabilized string-and-bow-construction, with the single segments consisting of inverse T-beams. The trunk bracing-system and osteoderm morphology of hyposaurine dyrosaurids indicate that the vertebral column could not be sufficiently stabilized against dorsoventral shear loads, and possibly transverse shear loads. As a consequence, the high walk and gallop could only be performed by individuals with low body mass. In the tail, the enormously elongated neural spines indicate a large cross section of the epaxial musculature, which facilitated the effective use of aquatic locomotor modes like axial and hybrid swimming.
Crocodilian cranial material from the Eocene Rundle Formation of eastern-central Queensland is herein attributed to Kambara taraina sp. nov. This is the fourth species of Kambara, the earliest genus of the diverse Australasian subfamily, Mekosuchinae. Although members of this subfamily diversified and radiated throughout the middle and late Tertiary, the clade as a whole is still poorly understood and their early evolutionary history is somewhat enigmatic. The Rundle Formation has yielded an unprecedented amount of crocodilian material for this epoch, with exquisite preservation. The new species is unique in possessing an increased attachment area for the mandibular adductors on the retroarticular process, rostrally extended palatal fenestrae, a rostrocaudally aligned ridge within the pterygoid fossa, and a reduction in maxillary alveoli (14). This combination of characters may reflect a functional divergence of K. taraina from other species, indicating disparate feeding strategies. The inclusion of this fourth species makes Kambara an increasingly diverse genus and as such the generic and specific diagnoses are herein modified accordingly.
The Cameros Basin, distributed over Soria, La Rioja and Burgos provinces in NE Spain, is apparently one of the richest sources of pterosaur footprints, with six ichnospecies of Pteraichnus named to date. The Cameros Basin exposes 9 km thickness of Late Jurassic and Lower Cretaceous continental deposits that are richly fossiliferous. Of the six alloformations in this sequence, the Huérteles Alloformation is a succession of alluvial siliclastics and lacustrine limestones dated as Tithonian-Berriasian in age. The pterosaur footprints are described, and compared with related forms from elsewhere. Of the six ichnospecies named from the Cameros Basin, Pteraichnus palacieisaenzi and P. cidacoi are nomina dubia because they lack holotypes housed in a public institution. Further, P. manueli and P. vetustior cannot be characterized at present, and so are also regarded as nomina dubia until diagnostic characters may be identified. P. longipodus and P. parvus are probably valid taxa, distinct from P. saltwashensis and P. stokesi, named previously from North America. Of the four supposed pterosaurian ichnogenera, Pteraichnus is valid, and Purbeckopus and Haenamichnus may be valid, but Agadirichnus is a nomen dubium because it is poorly characterized and lacks type specimens.
The recent discovery of early dinosauromorphs from North America demonstrates that they were contemporaries with dinosaurs and other basal archosaurs during a substantial portion of the Late Triassic Period. Hindlimb material (femora, tibiae, a fibula, astragalocalcanea, and phalanges) of Dromomeron romeri, a non-dinosauriform dinosauromorph from the Petrified Forest Member of the Chinle Formation from north-central New Mexico, is described. A new species of Dromomeron from the lower portion of the Chinle Formation (eastern Arizona) and Dockum Group (northern Texas) is also described, based on several disarticulated femora and tibiae. D. romeri, Lagerpeton, and the new taxon form the sister group to all other dinosauromorphs and demonstrate that this clade, Lagerpetidae, persisted well into the Norian. Lagerpetidae is supported by several synapomorphies: femoral head hook-shaped in medial and lateral views; ventral emargination on the anterolateral side of the femoral head; an enlarged posteromedial tuber of the proximal end of the femur; femoral crista tibiofibularis larger than the medial condyle; anteromedial corner of the distal end of the femur forms 90° or acute (>90°) angle; and a posterior ascending process of the astragalus. An ontogenetic series of the femur of Dromomeron indicates that some character states previously used in phylogenetic analyses of early dinosaurs may be ontogenetically variable.
Thoracic epaxial muscles of diplodocid and dicraeosaurid sauropods are reconstructed for the first time using an Extant Phylogenetic Bracket approach. In the dorsal vertebral column, three different epaxial muscle groups were present. The medialmost m. transversospinalis and the laterally adjacent m. longissimus dorsi were connected to the neural arches. The lateralmost m. iliocostalis was connected to the dorsal ribs. The medial part of m. transversospinalis of diplodocids and dicraeosaurids comprised at least two tendon systems that had a trellis-like arrangement. Osteological characters of the dorsal vertebrae in related taxa suggest a similar configuration of the thoracic epaxial muscles in all eusauropods, although there was variation in tendon arrangements and in the cross-section of each muscle. The thoracic epaxial musculature in eusauropods played an important role for trunk support; its variation in different eusauropods is directly connected with bony support structures and influenced the mobility of the trunk and locomotion. Modifications in the thoracic epaxial musculature are especially apparent in Saltasauridae, which suggests differences in their locomotor capabilities, such as increased trunk mobility or larger stride lengths.
Plausible poses were identified for the hind limb of Tyrannosaurus rex and three other non-avian theropod dinosaurs at mid-stance of locomotion using constraint-based exclusion. This new method, validated by analysis of two species of birds, involves applying demonstrably realistic geometric and kinetic (force-based) constraints from extant animals to exclude, rather than include, potential poses. Starting with a “configuration space” of millions of candidate poses, we used a step-wise series of criteria to constrict the volume to a small subset of solutions, which can serve as starting points for reconstructing complete stride cycles. It was found that the maximum relative mid-stance limb force, as well as the relative number of configurations at lower forces, decreased with increasing body size. Constraint-based exclusion restricted Tyrannosaurus to a narrow region of neither very columnar nor very flexed poses that may have allowed relatively slow running, but no reasonable combinations of input parameters and pose produce forces large enough for high speeds. This analysis shows that skeletal information alone has limited value for discerning mid-stance poses. Despite additional assumptions, unpreserved parameters such as masses, forces, and moments are required to study a fossil as a functioning animal, rather than as a moving set of bones. Constraint-based exclusion is a transparent, reproducible framework for evaluating functional hypotheses in dinosaurs and other taxa.
The lacustrine deposits of the Jiufotang Formation, Liaoning Province, China have yielded a diverse avifauna representing a wide spectrum of basal lineages. Here we add to this diversity by describing the longirostrine enantiornithean taxon Rapaxavis pani gen. et sp. nov. The specimen possesses the following autapomorphies: (1) caudoateral processes of the sternum with two prominent branches and a smaller third branch, (2) paired triangular thoracic elements of unknown homology, and (3) the combination of six sacral vertebrae and six free caudal vertebrae. Otherwise, this genus is closely allied with the Yixian Formation species Longirostravis hani, sharing elongate, curving rostrum with teeth restricted to the premaxilla and rostral-most dentary, and a derived manus lacking unguals. The holotype of Rapaxavis is exquisitely preserved, with such details as distal tarsals, keratinous sheaths of the pedal unguals and some three-dimensional features of the bones intact. The holotype appears to lack a fused tibiotarsus and a fused carpometacarpus. These features may indicate that the specimen is not yet fully grown, though the life stages of members of the Enantiornithes will not be clear until a complete ontogenetic series can be constructed. A comparison of the proportions of the pedal phalanges of Rapaxavis to modern birds shows Rapaxavis to be highly adapted to a grasping, arboreal lifestyle. The combination of strongly arboreal pedal adaptations and the probing adaptations in the rostrum is here confirmed in a member of the Enantiornithes for the first time in the literature, adding to their already impressive known functional diversity.
The analysis of recently recovered ground sloth remains from Minas Gerais, Bahia, and Piauí (Brazil) results in a major reinterpretation of the Scelidotheriinae and Megalonychidae of tropical Brazil. Among the specimens collected from Lagoa Santa (Minas Gerais) by Lund during the first half of the 19th century are skeletal elements attributable to two scelidotheriine species, as Lund himself determined and Winge corroborated. This is in contrast to the interpretation of these remains as representing a scelidotheriine and the postcranial remains of a peculiar megalonychid, as most authors, following Hoffstetter, have believed. A new combination is proposed here for one of the species. Another scelidotheriine recently described from Piauí by Guérin and Faure is a synonym of this species.
New data on the last representatives of the Spanish Miocene Moschidae (Mammalia, Ruminantia) are presented and discussed. A new species of Micromeryx, Micromeryx soriae, is described on the basis of fossil material from the locality of La Roma-2 (upper Vallesian; MN 10, Teruel province, Spain, previously assigned to Micromeryx sp.), Batallones-1, and Batallones-10 (upper Vallesian; local zone J, MN 10, Madrid province, Spain). The new species is characterized by possessing relatively hypsodont lower molars of advanced morphology and a unique type of Palaeomeryx-fold. M. soriae gives insight to the last representatives of the genus, which achieved an overall lower molar morphology that mimics to certain degree that of Hispanomeryx. several characters of the upper molars of the Miocene moschids Micromeryx and Hispanomeryx are described that are useful for characterizing both genera. These characters are used to solve the taxonomic problems of PM-659, an upper molar from Puente Minero (MN 11, Teruel province, Spain) that represents one of the last survivors of the Moschidae in the Iberian Peninsula. The systematic utility of the upper molars of Hispanomeryx and Micromeryx is demonstrated, and the use of size as the only way to distinguish between the two genera is refuted. Finally, the study of the morphological characters of PM-659 clearly supports its generic change from Micromeryx sp. to Hispanomeryx sp., thus recording the presence of Hispanomeryx in the Iberian Peninsula as late as the lower Turolian.
Mimotonids have recently been recognized as the likely ancestors to Lagomorpha (rabbits, hares, and pikas). Here a new species of mimotonid, Gomphos ellae, from Tsagaan Khutel locality, Valley of Lakes, Mongolia is described. This new material shows typical mimotonid features while also exhibiting important derived lagomorph features and helps to bridge the morphological and temporal gap between mimotonids and lagomorphs. The fossils comprise a right dentary, including cheek teeth and incisor, and a partial maxilla with two teeth. The dental features of G. ellae are similar to the mimotonid G. elkema, but G. ellae is distinguished from G. elkema and all other mimotonids by its long diastema. The diastema length of G. ellae is intermediate between all other mimotonids and all living and extinct lagomorphs. This feature distinguishes mimotonids from lagomorphs and the intermediate diastemal length of G. ellae further supports a strong pattern of lengthening of the diastema throughout Duplicidentata. Geologic and paleontological evidence suggest that the specimen is of Middle Eocene age, consistent with the notion that this taxon is an advanced mimotonid that likely lies near the ancestry of the lagomorphs.