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Five cross sections of major limb bones of Deinonychus. (A) Ulna, MCZ 8791 (juvenile). (B) Femur, MOR 1178. C. Radius, MOR 1178. (D) Humerus, MOR 1178. (E) Fibula, MOR 1178. (F) Tibia, MOR 1178. Scale bars are all equal to 1 cm. Copyright of images of MCZ specimens held by Museum of Comparative Zoology, Harvard University. Copyright of images of MOR specimens held by Museum of the Rockies.
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Developmental and/or functional implications are described for aspects of Deinony- chus antirrhopus scapula, pedal, and long bone morphology. Differences in claw curvature are identi- fied as indicators of juvenile development, and the presence of periosteal rest lines as evidence for determinate growth is confirmed. The asymmetric ventral keel mor...
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... histology of the radius of the older individual specimen MOR 1182 is almost com- pletely remodeled by secondary osteon replace- ment, but the radius of the young adult speci- men MOR 1178 (physical maturity at 11 to 12 years of age according to LAGs) (Fig. 4C) still possesses a considerable amount of intact histo- logical information such as zonal fibrolamellar tissue, lines of arrested growth, remnants of the more medial LAGs still apparent between sec- ondary osteons, the condensing of lines of ar- rested growth which is the probable point of sexual maturity, and periosteal rest lines. ...
Citations
... The pedal ungual of Dineobellator shows a similar condition with a pronounced flexor tubercle (Figure 16), although not to the same degree as that of the manual ungual. The pedal claws of dromaeosaurids have been hypothesized to be capable of serving both defensive and predatory functions (e.g., Adams, 1987;Colbert & Russell, 1969;Gianechini et al., 2020;Manning et al., 2006Manning et al., , 2009Ostrom, 1969Ostrom, , 1990Parsons & Parsons, 2009;Senter, 2009). The flexor tubercle in the pedal ungual of Dineobellator is approximately 67% the height of the articular surface. ...
Dromaeosaurids (Theropoda: Dromaeosauridae), a group of dynamic, swift predators, have a sparse fossil record, particularly at the end of the Cretaceous Period. The recently described Dineobellator notohesperus, consisting of a partial skeleton from the Upper Cretaceous (Maastrichtian) of New Mexico, is the only diagnostic dromaeosaurid to be recovered from the latest Cretaceous of the southwestern United States. Reinterpreted and newly described material include several caudal vertebrae, portions of the right radius and pubis, and an additional ungual, tentatively inferred to be from manual digit III. Unique features, particularly those of the humerus, unguals, and caudal vertebrae, distinguish D. notohesperus from other known dromaeosaurids. This material indicates different physical attributes among dromaeosaurids, such as use of the forearms, strength in the hands and feet, and mobility of the tail. Several bones in the holotype exhibit abnormal growth and are inferred to be pathologic features resulting from an injury or disease. Similar lengths of the humerus imply Dineobellator and Deinonychus were of similar size, at least regarding length and/or height, although the more gracile nature of the humerus implies Dineobellator was a more lightly built predator. A new phylogenetic analysis recovers D. notohesperus as a dromaeosaurid outside other previously known and named clades. Theropod composition of the Naashoibito Member theropod fauna is like those found in the more northern Late Cretaceous North American ecosystems. Differences in tooth morphologies among recovered theropod teeth from the Naashoibito Member also implies D. notohesperus was not the only dromaeosaurid present in its environment.
... For instance, Ostrom (1976) found similar differences between Deinonychus antirrhopus specimens (MCZ 4371, YPM (2015); Additional photos by Stephen L. Brusatte 5205) that suggested individual, ontogenetic, or sexual variation. It has also been accounted for as ontogenetic changes from immature to adult specimens (Parsons and Parsons 2009). Among other morphological similarities, the specialised second pedal toe has led to wide discussion of the phylogenetic relationships between Dromaeosauridae and Troodontidae (Colbert and Russell 1969;Ostrom 1969b;Barsbold 1974;Osmólska 1982Osmólska , 1987Gauthier 1986;Barsbold et al. 1987). ...
Dromaeosaurids are poorly known in Europe and their fossil records are mostly postcranial remains. To date, the French faunal records of the family Dromaeosauridae include two taxa: Pyroraptor olympius and Variraptor mechinorum. Nevertheless, their taxonomic validity and phylogenetic relationships as dromaeo-saurids are controversial. Here, we report a new record of a dromaeosaurid-like pedal ungual from the 'Grès à Reptiles' Formation (Campanian-Maastrichtian) of the Upper Cretaceous of southern France. The French specimen was assigned to cf. Dromaeosauridae on the basis of an extensive qualitative analysis. The new specimen has a strongly curved morphology with a tall, narrow cross-section, which is one of the most characteristic anatomical features of the family. Direct comparison reveals that the claw is similar to that of Pyroraptor olympius (MNHN BO001) from a stratigraphically correlated locality. ARTICLE HISTORY
... Posteriorly, the ventral edge of the scapula is confluent with both the lateral ridge and the lateral margin of the blade. In the anterior margin of the scapular glenoid, near to its dorsal margin there is a small elliptical excavation that represents the attachment of the scapulohumeral ligament (Figure 12a), as occurs in living birds and Bambiraptor and Deinonychus (Parsons & Parsons, 2009). On the medial surface of the bone, and dorsal to the glenoid, there is a well-defined elliptical excavation, similar to that present in Deinonychus (YPM 5236) and Herrerasaurus (Sereno, 1993), probably representing the site of attachment of the medial head of the M. subscapularis. ...
Unenlagia comahuensis was originally described as a phylogenetic link between nonavian dinosaurs and birds. Later it was interpreted by some authors as belonging to the deinonychosaurian clade Dromaeosauridae, and more recently as phylogenetically closer to birds than to dromaeosaurids. The only known specimen is represented by an incomplete skeleton, including vertebrae, incomplete scapular girdle, pelvis, and limbs, coming from Upper Cretaceous beds of Neuquén province, Patagonia, Argentina. The aim of the present paper is to include a detailed anatomical description of Unenlagia (currently only known by preliminary descriptions). Detailed analysis of Unenlagia anatomy resulted in the recognition of one possible additional Unenlagiidae synapomorphy (i.e., the presence of cup‐like iliac articulation on ischium). We recognize derived anatomical traits that Unenlagia and kin share with birds, lending support to the interpretation that unenlagiids are stem‐Avialae. Particularly, some appendicular features (e.g., scapula with subtriangular and relatively reduced acromion, poor outward projection of the glenoid and glenoidal lips on the scapula, lateral orientation of scapular glenoid, craniolaterally oriented deltopectoral crest of humerus) may be related to the acquisition of anatomical novelties that in birds are associated with flight. The present contribution on Unenlagia provides new data regarding the early evolution of avian features.
... Among the Dromaeosauridae, subadult to adult specimens of Deinonychus (MOR 1178) (Parsons and Parsons, 2009), Velociraptor (IGM 100/986; Parsons and Parsons, 2009), and Microraptor (CAGS 20-7-004 and CAGS 20-8-001) (Hwang et al., 2002) reportedly possess fused scapulocoracoids, whereas the two elements are only sutured in obvious juveniles (Deinonychus MCZ 8791;Parsons and Parsons, 2015). However, the scapula and coracoid remain connected by a suture in putatively adult specimens of some taxa, including in Buitreraptor (MPCA-245) (Makovicky et al., 2005) and Sinornithosaurus (IVPP V12811) (Xu et al., 1999). ...
As key components of the tetrapod pectoral girdle, the scapula and coracoid have played a significant role in the evolution of forelimb locomotion among terrestrial vertebrates. The transition from a rigid fused scapulocoracoid in ancestral non-avian theropods to a presumably more flexible separated scapula-coracoid in early birds is considered to be one of the key morphological transitions related to the rapid refinement of flight. In most Mesozoic birds (e.g., Enantiornithes and Ornithuromorpha) and crown birds the scapula and coracoid are separate (unfused), with few exceptions (e.g., flightless paleognaths). In contrast, in Confuciusornis, a basal pygostylian from the Early Cretaceous Jehol Biota known from thousands of specimens, the scapula and coracoid remain plesiomorphically fused. This raises questions regarding the influence of shoulder girdle architecture on the early evolution and refinement of avian flight. The paravian scapula-coracoid joint has never previously been investigated using histology, and thus joint morphology has only been inferred superficially. In order to better understand the evolution of this joint in Mesozoic birds, we make the first histological study of the scapulocoracoid glenoid joint in Confuciusornis. The results demonstrate that the scapula and coracoid both consist of cancellous and compact bone, with both fibrolamellar and parallel-fibered structure. A thin layer of calcified cartilage is present on the glenoid fossa surface, representing remnants of the articular surface for the humerus. Both histology and computed tomography reveal that the scapulocoracoid of Confuciusornis is fully fused, forming a synostosis. Humeral histology suggests the studied individual was nearing completion of its first year of growth, suggesting the Confuciusornis scapulocoracoid fused before skeletal maturity was achieved, as in flightless paleognaths, whereas in the plesiomorphic condition fusion occurs late in ontogeny. We hypothesize the fused scapulocoracoid of Confuciusornis is secondarily evolved and suggest the primary factor responsible for this morphology may have been a decrease in mechanical stimulation at the glenoid of Confuciusornis relative to other volant birds, linked to the unique flight style of this taxon. Further investigation into the histology of the glenoid joint in other Mesozoic paravians and extant birds will help to clarify the morphological transition of the scapula-coracoid joint in early avian evolution.
... Cau et al. 32 presented cross-sections of the long bones of the forelimb (the humerus, radius and ulna) and suggested the morphology of these cross sections was allied with the flattened state seen in the forelimbs of marine reptiles and diving birds 32 . However, this comparison is not precise or well-justified, as the distal humerus, radius and ulna of Halszkaraptor are clearly ellipsoid in cross-section (Fig. 1e-h in 32 ) and clearly similar to the ellipsoid cross-sections of the upper forelimb bones of other paravians, such as Archaeopteryx 77 and Deinonychus 78 . In contrast, the cross-sections of the forelimb bones of long-necked marine reptiles, including nothosaurs 79 and plesiosaurs 80 , are far more flattened and do not show a clearly elliptical cross-section (Fig. 3 in 79; Fig. 2a in 80). ...
... The morphology of the cross-sections of the long bones of Halszkaraptor presented by Cau et al. 32 also show an additional flaw in the hypothesis that this taxon was semiaqautic. The bones of Halszkaraptor are clearly internally hollow to a similar extent as other paravian dinosaurs 77,78 . ...
The evolution of birds from dinosaurs is a subject that has received great attention among vertebrate paleontologists. Nevertheless, the early evolution of the paravians, the group that contains birds and their closest non-avian dinosaur relatives, remains very poorly known. Even the most basal members of one paravian lineage, the Dromaeosauridae, already show a body plan that differs substantially from their closest non-paravian relatives. Recently, the dromaeosaurid Halszkaraptor escuilliei was described from the Cretaceous of Mongolia. Halszkaraptor possesses numerous unserrated premaxillary teeth, a platyrostral rostrum with a developed neurovascular system, an elongate neck, bizarrely-proportioned forearms, and a foreword-shifted center of mass, differing markedly from other paravians. A reevaluation of the anatomy, taphonomy, environmental setting, and phylogenetic position of H. escuilliei based on additional comparisons with other maniraptorans suggests that, rather than indicating it was a semiaquatic piscivore, the body plan of this dinosaur bears features widely distributed among maniraptorans and in some cases intermediate between the conditions in dromaeosaurids and related clades. I find no evidence for a semiaquatic lifestyle in Halszkaraptor. A phylogenetic reevaluation of Halszkaraptorinae places it as the sister clade to Unenlagiinae, indicating the bizarre features of unenlagiines previously interpreted as evidence of piscivory may also represent a mosaic of plesiomorphic, derived, and intermediate features. The anatomy of Halszkaraptor reveals that dromaeosaurids still possessed many features found in more basal maniraptoran and coelurosaur clades, including some that may have been tied to herbivory. Rather than being a semiaquatic piscavore, Halszkaraptor was a basal dromaeosaurid showing transitional features.
... The dromaeosaurid Deinonychus antirrhopus [1] is known from several specimens collected from the Early Cretaceous Cloverly Formation of Montana [1][2][3] and one specimen from the Antlers Formation of Oklahoma, Oklahoma Museum of Natural History (OMNH) 50268 [4]. ...
... Still, the shallow, open morphology of the scapular glenoid in D. antirrhopus as well as its lateral orientation [3] would have allowed for a considerable arc of movement that was well within the range of functional avian wing flapping. This scapular glenoid would have allowed for the forelimb/wing to have been raised and lowered in a vertical manner and extended to some degree in a cranial direction. ...
This research resulted from the determination that MCZ 8791 is a specimen of Deinonychus antirrhopus between one and two years of age and that the morphological variations within particular growth stages of this taxon have yet to be described. The primary goal of the research is to identify ontogenetic variations in this taxon. Histological analyses determined that the Deinonychus specimens AMNH 3015 and MOR 1178 were adults. Comparisons are made between MCZ 8791 and these adult specimens. The holotype, YPM 5205, and the other associated specimens of this taxon within the YPM collection are similar in size and morphology to AMNH 3015. Further comparisons were made with the three partial specimens OMNH 50268, MCZ 4371, and MOR 1182. Although these specimens represent only a partial ontogenetic series, a number of morphological variations can be described. One secondary goal of this research is to compare the known pattern of variable, informative , ontogenetic characters in MCZ 8791 to a similar pattern of morphological characters in the sub-adult dromaeosaurid specimen Bambiraptor feinbergorum, AMNH FR: 30556. If the characters that have been determined to represent variable juvenile morphology in the ontogeny of Deinonychus are exhibited in Bambiraptor, this study will begin the process of determining whether a similar, conservative, ontogenetic pattern exists throughout the rest of Dromaeosauridae. If defensible, it may reduce the number of sympatric taxa within this clade. The other secondary goal relates to the forelimb function. The approximate body size, forelimb length, wrist development, and the presence of a more prominent olecranon on the ulna of MCZ 8791 support the hypothesis that juveniles of this taxon possessed some form of flight capability.
A new small-bodied theropod dinosaur, Migmanychion laiyang gen. et sp. nov., is erected based on appendicular skeletal material from the Lower Cretaceous of the Pigeon Hill locality, Inner Mongolia, China. This theropod shows a peculiar combination of features in the hand, in part shared with therizinosauroids, oviraptorosaurs and with the enigmatic Fukuivenator paradoxus from Japan. Phylogenetic analysis supports the closest affinity of Migmanychion with Fukuivenator, yet alternative placements among Oviraptorosauria or among the non-avialan paravians result suboptimal descriptions of the character distribution. Although this new taxon is confidently referred to Maniraptora, this result is based uniquely on derived features of the hand: only additional material could substantiate its precise placement among the bird-like theropods. Fragmentary appendicular material from the same locality cannot be unambiguously referred to Migmanychion. One specimen, including associated partial pelvis and hindlimbs, is tentatively referred to a paravian maniraptoran.
Since the beginning of the 1990s, palaeontologists have been interested in understanding biological processes recorded within the bone microstructure of deinonychosaurian theropods, the group comprising Troodontidae and Dromaeosauridae. Several studies were published on this subject, and the growing database requires the first revision of used terminology and older interpretations. Furthermore, a platform correlating the developmental characters of all investigated taxa is missing. Hence, we lack a perspective to evaluate the potential of deinonychosaurian osteohistology for understanding their evolution and that of their close relatives, including avialans. This study aimed to fill in this gap by offering a comprehensive review of the previous osteohistological investigations published on deinonychosaurians and Archaeopteryx. Four significant evolutionary phenomena are assumed from the investigated deinonychosaurian taxa: (1) it is likely that troodontids evolved general osteohistology closer to basal avialans than to dromaeosaurids, (2) in troodontids, reticular vasculature is correlated to maturation timing, (3) the first growth deceleration occurs later in smaller deinonychosaurs (e.g. Changyuraptor, Sinornithosaurus) than in larger forms (e.g. Buitreraptor), and (4) the growth rate of the deinonychosaurs' hind limbs might be correlated with a specific type of locomotion.
In amniotes, the predominant developmental strategy underlying body size evolution is thought to be adjustments to the rate of growth rather than its duration. However, most theoretical and experimental studies supporting this axiom focus on pairwise comparisons and/or lack an explicit phylogenetic framework. We present the first large-scale phylogenetic comparative analysis examining developmental strategies underlying the evolution of body size, focusing on non-avialan theropod dinosaurs. We reconstruct ancestral states of growth rate and body mass in a taxonomically rich dataset, finding that contrary to expectations, changes in the rate and duration of growth played nearly equal roles in the evolution of the vast body size disparity present in non-avialan theropods-and perhaps that of amniotes in general.
This Doctoral Thesis presents an exhaustive review of the Patagonian alvarezsaurids (Dinosauria, Theropoda). It includes a detailed osteological description of specimens of Patagonykus puertai (Holotype, MCF-PVPH-37), cf. Patagonykus puertai (MCF-PVPH-38), Patagonykinae indet. (MCF-PVPH-102), Alvarezsaurus calvoi (Holotype, MUCPv-54), Achillesaurus manazzonei (Holotype, MACN-PV-RN 1116), Bonapartenykus ultimus (Holotype, MPCA 1290), and cf. Bonapartenykus ultimus (MPCN-PV 738). A phylogenetic analysis and a discussion about the taxonomic validity of the recognized species and the taxonomic assignment of the materials MCF-PVPH-38, MCF-PVPH-102 and MPCN-PV 738 are presented. Different evolutionary and paleobiological studies were carried out in order to elucidate functional and behavioral aspects.
Alvarezsaurus calvoi (MUCPv-54), Achillesaurus manazzonei (MACN-PV-RN 1116), Patagonykus puertai (MCF-PVPH-37) and Bonapartenykus ultimus (MPCA 1290) are valid species due to the presence of many autapomorphies. In this sense, the hypothesis proposed by P. Makovicky and collaborators that Achillesaurus manazzonei is a junior synonym of Alvarezsaurus calvoi is rejected. Likewise, certain morphological evidence allows hypothesizing that Alvarezsaurus calvoi represents a growth stage earlier than skeletal maturity. Specimen MCF-PVPH-38 is referable as cf. Patagonykus puertai, while MCF-PVPH-102 is considered an indeterminate Patagonykinae. In turn, MPCN-PV 738 is assigned as cf. Bonapartenykus ultimus based on the little overlapping material with the Bonapartenykus ultimus holotype.
The results obtained from the mineralogical characterization through the X-ray diffraction method of specimens MPCN-PV 738 and the holotype of Bonapartenykus ultimus (MPCA 1290), allow to suggest that both specimens come from the same geographical area and stratigraphic level.
The phylogenetic analysis, which is based upon the matrix of Gianechini and collaborators of 2018 with the inclusion of proper characters, and the database of Xu and collaborators of 2018, recovered the South American members of Alvarezsauria, such as Alnashetri cerropoliciensis (Candeleros Formation; Cenomanian), Patagonykus puertai (Portezuelo Formation, Turonian-Coniacian), Alvarezsaurus calvoi and Achillesaurus manazzonei (Bajo de La Carpa Formation, Coniacian-Santonian), and Bonapartenykus ultimus (Allen Formation, Campanian-Maastrichtian), nesting within the family Alvarezsauridae. In this sense, the forms that come from the Bajo de La Carpa Formation (Coniacian-Santonian) are recovered at the base of the Alvarezsauridae clade, while Alnashetri cerropoliciensis nests as a non-Patagonykinae alvarezsaurid. Regarding the type specimens of Patagonykus puertai and Bonapartenykus ultimus, they are recovered as members of the Patagonykinae subclade, a group that is recovered as a sister taxon of Parvicursorinae, both nested within the Alvarezsauridae. In addition, the topology obtained allows discerning the pattern, rhythm and time of evolution of the highly strange and derived alvarezsaurian skeleton, concluding in a gradual evolution. The Bremer and Bootstrap supports of the nodes (Haplocheirus + Aorun), [Bannykus + (Tugulusaurus + Xiyunykus)], and Patagonykinae, show indices that represent very robust values for these nodes. Likewise, these values suggest that two endemic clades originated early in Asia, while one endemic clade is observed in Patagonia, i.e., Patagonykinae.
The analysis of the directional trends of the Alvarezsauria clade, tested by means of a own database on body masses based on the Christiansen and Fariña method, subsequently calibrated with the group's phylogeny using the R software, shows two independent miniaturization events in the alvarezsaurid evolution, namely the former originating from the base of the Alvarezsauridae (sustained by Alvarezsaurus), and the latter within the Parvicursorinae. Analysis of the Alvarezsauria dentition reveals possible dental synapomorphies for the Alvarezsauria clade that should be tested in an integrative phylogenetic analysis. The general characterization of the forelimb and a partial reconstruction of the myology of alvarezsaurs demonstrate different configurations for Patagonykinae and Parvicursorinae. The multivariate analyzes carried out from the databases of Elissamburu and Vizcaíno, plus that of Cau and collaborators, show that the Patagonykinae would have had ranges of movements greater than those observed in Parvicursorinae, although the latter would have had a greater capacity to carry out more strenuous jobs. The morphometric analysis of the hindlimb and the use of the Snively and collaborators equations, show that the configuration of this element in Alvarezsauria is indicative of a highly cursorial lifestyle, as well as possible particular strategies for more efficient locomotion. The topology obtained in the phylogenetic analysis that was carried out in this Doctoral Thesis, allowed clarifying the ontogenetic changes observed in the ontogenetic series of the manual ungueal element II-2 within the clade Alvarezsauridae. In addition, the multivariate analysis carried out from the manual phalanx II-2 allows us to infer that alvarezsaurs could have performed functions such as hook-and-pull and piercing, where the arm would function as a single unit. The anatomy and myology of the alvarezsaurian tail show that the caudal vertebrae of alvarezsaurians exhibit a combination of derived osteological features that suggests functions unique among theropods, such as considerable dorsal and lateral movements, as well as exceptional abilities to support distal loading of their long tail without compromising stability and/or mobility.
