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A new dromaeosaurid from the Horseshoe Canyon Formation (Upper Cretaceous) of Alberta, Canada
... The antorbital fenestra is roughly equal in height and length or taller than longer in Saurornitholestes langstoni UALVP 55700, Sinornithosaurus millenii IVPP V12811 (Xu and Wu 2001;Currie and Evans 2020), and most likely in Atrociraptor marshalli (Powers et al. 2022). The ventral margin of the antorbital fenestra tapers anterodorsally, at an angle equal to 24° (measured between the ventral margin of the antorbital fossa and ventral margin of the antorbital fenestra), which is an angle not observed in any specimen of V. mongoliensis (up to 15°); however, it is similar to that of Bambiraptor feinbergi AMNH FARB 30556 and Atrociraptor marshalli (Burnham et al. 2000;Currie and Varricchio 2004). The ventral margin of the antorbital fossa extends below the dorsal extent of maxillary alveoli, as in V. mongoliensis, Shanag ashile, and Saurornitholestes langstoni, but in contrast to "Velociraptor" osmolskae, T. mangas and L. exquisitus (Powers et al. 2022). ...
... It differs from the condition seen in L. exquisitus, and T. mangas where the single promaxillary fenestra is more ventral than the maxillary one (Norell et al. 2006;Xu et al. 2010Xu et al. , 2015. Closely located maxillary and promaxillary fenestrae are also seen in Achillobator giganticus, Atrociraptor marshalli, and "V." osmolskae (Currie and Varricchio 2004;Godefroit et al. 2008;Turner et al. 2012); however, in the latter, the promaxillary fenestra is of similar large size as the maxillary one. ...
... In V. mongoliensis (AMNH FARB 6515, MPC-D 100/25, MPC-D 100/54), L. exquisitus (IVVP V1692) and T. mangas (MPC-D 100/1015) there is a simple suture with the maxillary process of the jugal overlapping the maxilla dorsally. The longitudinal notch on the posterior part of the jugal ramus of the Atrociraptor marshalli TMP 1995.166.0001 maxilla suggests the presence of the Z-shaped suture (Currie and Varricchio 2004;Powers et al. 2022). that is also visible on the left side of the specimen of Saurornitholestes langstoni UALVP 55700 (Currie and Evans 2020). ...
Numerous dromaeosaurid taxa recovered from the Upper Cretaceous strata of the Gobi Desert raise questions over niche
partitioning among closely related species. Here, I describe a dromaeosaurid specimen from the Baruungoyot strata of
the Khulsan locality, containing a partial skull in close association with the left hind limb. The material can be referred
to the velociraptorine Shri devi, until now known only from a single specimen lacking a skull, collected from the same
site. The referral is based on the apomorphic morphology of the pes, including the highly hypertrophic ungual of the
second digit and details of the metatarsus. The skull of S. devi confirms its close affinities with Velociraptor mongoliensis,
but shows distinctive features among Velociraptorinae, including a short antorbital fenestra, a Z-shaped maxillo-jugular
suture, a distinct labial ridge above the supralabial foramina row of the maxilla, and the posterior position of the last
maxillary tooth. The skull of S. devi is slender, but relatively short when compared to other velociraptorines, suggesting
convergence to the North American eudromaeosaurians. The Baruungoyot strata with S. devi represent less arid conditions
than the aeolian Djadokhta strata yielding V. mongoliensis, supporting earlier observations linking the elongation
of the dromaeosaurid snout with the environment.
... Early Cretaceous North American dromaeosaurids include Deinonychus antirrhopus, Utahraptor ostrommaysi, and Yurgovuchia doellingi (e.g., Brinkman et al., 1998;Kirkland et al., 1993;Ostrom, 1969;Senter et al., 2012). Several other taxa are known from the Late Cretaceous, but almost all are from the Campanian, although it is noted that Atrociraptor marshalli comes from the Maastrichtian (probably early Maastrichtian) portion of the Horseshoe Canyon Formation (e.g., Burnham, 2004;Burnham et al., 2000;Currie & Varricchio, 2004;Longrich & Currie, 2009;Larson et al., 2010;Jasinski, 2015a;Matthew & Brown, 1922;Sues, 1978). Recently, two taxa (Acheroraptor temertyorum and Dakotaraptor steini) were named from the upper Maastrichtian Hell Creek Formation, but, aside from these two skeletal fossil specimens, non-tooth material of Maastrichtian taxa is rare (e.g., DePalma et al., 2015;Evans et al., 2013;. ...
... Additionally, the denticles tend to be proximodistally (or dorsoventrally) shallow in relation to craniocaudal depth. Additional dromaeosaurids possessing distal (caudal) denticles that are not apically hooked (and instead are rounded) are Acheroraptor temertyorum and Tsaagan mangas whereas others, such as Atrociraptor marshalli and Saurornitholestes langstoni, are apically hooked (Currie & Evans, 2019;Currie & Varricchio, 2004;Larson, 2008). On the apical end of the rostral edge of the tooth, there is a wear facet that measures approximately 7 mm along the curvature of the tooth from the distal tooth tip where it would occlude with a dentary tooth. ...
... Raked here refers to the tooth curving caudally, as in the motion of sweeping with a rake or broom. This latter aspect of the teeth differs from those of Atrociraptor, Bambiraptor, and Deinonychus, where the teeth are strongly raked caudally (e.g., Burnham, 2004;Burnham et al., 2000;Currie & Varricchio, 2004;Ostrom, 1969). ...
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.
... With the exception of Deinonychus antirrhopus, Velociraptor mongoliensis (Osborn, 1924;Makovicky, 1997, 1999;Barsbold and Osmólska, 1999;Hone et al., 2012), and now Saurornitholestes langstoni (Sues, 1976;Currie and Evans, 2019), derived dromaeosaurids are largely known from single articulated or associated skeletons (Matthew and Brown, 1922;Perle et al., 1999;Norell et al., 2006;Xu et al., 2010;Turner et al., 2021), or, more commonly, fragmentary remains (Currie and Varricchio, 2004;Godefroit et al., 2008;Evans et al., 2013). The limited material for eudromaeosaurians and other small-bodied vertebrates is in part due to preservational biases being skewed towards large-bodied organisms (e.g., Brown et al., 2013). ...
... The limited material for eudromaeosaurians and other small-bodied vertebrates is in part due to preservational biases being skewed towards large-bodied organisms (e.g., Brown et al., 2013). Of the material known for eudromaeosaurians, one of the most diagnostic skeletal elements has been the maxilla (Currie and Varricchio, 2004;Godefroit et al., 2008;Evans et al., 2013). Because of the incomplete nature of the specimens attributed to a substantial number of eudromaeosaurians, attempts have been made to extract as much taxonomic information from the available elements as possible, with considerable attention to the maxilla because of its morphological complexity and variability within the clade. ...
... Both Evans et al. (2013) and Powers et al. (2020) recovered Acheroraptor as a North American velociraptorine; however, Powers et al. (2020) noted that the proportions and morphology of the posterior region of the holotype suggest similarities to North American taxa such as Atrociraptor and Saurornitholestes and that more detailed comparisons are needed to determine the relationships of this taxon. On the other side of proportional variation in eudromaeosaurian maxillae, Atrociraptor marshalli (Currie and Varricchio, 2004) possesses an extremely deep maxilla, thought to be apomorphic to this taxon. This specimen is only partially described because the specimen was not fully prepared at the time of its initial description. ...
Eudromaeosauria is a clade of derived dromaeosaurids that typifies the common perception of ‘raptor’ dinosaurs. The evolutionary history of this clade has been controversial due to conflicting views of taxonomic identity, and because, due to taphonomic bias, several species were diagnosed primarily or solely by the maxilla. The maxilla is therefore crucial in understanding the phylogenetic relationships within the clade. Morphometric characterization has been commonly applied to recognize and distinguish major dromaeosaurid clades. However, morphometrics mainly showed morphological convergence rather than phylogenetic relationships. This approach has made it difficult to get resolution of phylogenetic relationships among eudromaeosaurian taxa, often resulting in large polytomies or inconsistent placement of key species. To test previous character statements, computed tomography was used to analyze the maxillae of Acheroraptor, Atrociraptor, and Deinonychus, and compare them with other eudromaeosaurians from Asia and North America. Morphometric characters were examined, and regressions were used to look for allometric trends in maxillary dimensions and the relationship to topological landmarks within Eudromaeosauria and its outgroups. Characters were improved and implemented to better capture eudromaeosaurian morphological variation and better resolve their phylogenetic relationships. Phylogenetic analysis recovered three well-defined clades within Eudromaeosauria and corroborated occurrence data within the fossil record. Acheroraptor and Atrociraptor were recovered as derived members of Saurornitholestinae. Deinonychus is recovered as a basal eudromaeosaurian, sharing features with dromaeosaurines and saurornitholestines. These results challenge previous biogeographic hypotheses suggesting Asian and North American faunal interchange during the Late Cretaceous and support convergence of traits relating to snout dimensions and proportions.
... Although the maxillary fenestra abuts the anterior margin of the antorbital fossa as in Tsaagan (Norell et al., 2006;Turner et al., 2012), it never extends to the anteroventral corner unlike that of Linheraptor (Xu et al., 2015). The maxillary fenestra is expanded posteriorly to occupy slightly more than the half the length between the anterior margin of the antorbital fossa and that of the antorbital fenestra, as in troodontids (Currie and Varricchio, 2004). The maxillary fenestra is expanded dorsoventrally as well, while separated from the ventral margin of the antorbital fossa. ...
... Maxillary fenestra and other openings on antorbital fossa One of the notable characters of Fukuivenator, the large maxillary fenestra occupying more than half the area between the anterior margins of the antorbital fossa and fenestra, is also present in most troodontids (character 27). Such condition of the maxillary fenestra is scored as a second derived state for Troodontidae by Currie and Varricchio (2004;character 22 (2)) and incorporated into the TWiG dataset by Turner et al. (2012;character 27). However, this character scoring was modified in the latter study into the first derived state (state 1) for most troodontids as possessing the smaller maxillary fenestra, except for jinfengopterygines, although the maxillary fenestra is apparently larger also in other troodontids Pei et al., 2017). ...
A bizarre coelurosaurian theropod Fukuivenator paradoxus is known only from the holotype specimen preserving majority of the skeleton from the Kitadani Dinosaur Quarry of the Lower Cretaceous Kitadani Formation, Tetori Group, Fukui, Japan. With aids of computed tomography techniques, a re-examination of the holotype specimen reveals additional features of Fukuivenator which was unobservable in the original description, such as the presence of parietals and a quadrate, and the fusion of the posteriormost caudal vertebrae. The thorough description in this study results in the emendation of diagnosis including the retraction of the large promaxillary fenestra subequal in size to maxillary fenestra, and the addition of the large maxillary fenestra expanded well dorsally above the suprantral strut. Expansion of morphological information elaborates the phylogenetic dataset, resulting in locating Fukuivenator as an unambiguous member of Maniraptora at the basalmost position of Therizinosauria. This phylogenetic position of Fukuivenator is supported by several therizinosaurian synapomorphies such as the subotic recess on the braincase, 11 cervical vertebrae some of which having two pneumatic foramina, and distal articular condyles on the anterior surface of the humerus. Among numerous diagnostic features, eight characters shared with some non-maniraptoran coelurosaurs and five shared with different clades within Maniraptora, highlighting the notably mosaic condition of Fukuivenator proposed in the original description. The combination of characters for herbivorous and carnivorous diets suggests the omnivory of Fukuivenator, projecting the dietary shift in the earliest evolutionary stage of Therizinosauria. Also, the large olfactory ratio revealed by the revised brain endocast highlights the unusually high olfactory acuity further developed than the plesiomorphic condition, implying that the acute sense of smell might be a characteristic of therizinosaurian theropods.
... Dromaeosaurids are known from the Cretaceous (Norell & Makovicky, 2004). Their skeletal remains were found in various geological formations in Argentina (Gianechini & Apesteguía, 2011;Novas & Puerta, 1997), Canada (Currie & Evans, 2020;Currie & Varricchio, 2004;Matthew & Brown, 1922;Sues, 1978), China (Poust et al., 2020;Xu et al., 1999Xu et al., , 2000Xu et al., , 2003Zheng et al., 2010), Mongolia (Barsbold et al., 1999;Osborn, 1924), Romania (Brusatte et al., 2013;Csiki et al., 2010), the USA (Burnham et al., 2000;Kirkland et al., 1993;Ostrom, 1969;Senter et al., 2012) and Uzbekistan (Kurzanov, 1976). Some fragmentary remains have even been reported from Antarctica (Case et al., 2007). ...
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.
... This taxon is North America's only named microraptorine and the youngest one worldwide by almost 45 million years (Longrich and Currie, 2009). Atrociraptor marshalli is a fragmentary taxon recovered from the similarly aged Horseshoe Canyon Formation from the same part of Canada (Currie and Varricchio, 2004). It consists of a partial rostrum, including both premaxillae, a right maxilla, and both dentaries. ...
An unabated surge of new and important discoveries continues to transform knowledge of pen-naraptoran biology and evolution amassed over the last 150+ years. This chapter summarizes progress made thus far in sampling the pennaraptoran fossil record of the Mesozoic and Paleocene and proposes priority areas of attention moving forward. Oviraptorosaurians are bizarre, nonparavian pennaraptorans first discovered in North America and Mongolia within Late Cretaceous rocks in the early 20th century. We now know that oviraptorosaurians also occupied the Early Cretaceous and their unquestionable fossil record is currently limited to Laurasia. Early Cretaceous material from China preserves feathers and other soft tissues and ingested remains including gastroliths and other stomach contents, while brooding specimens and age-structured, single-species accumulations from China and Mongolia provide spectacular behavioral insights. Less specialized early oviraptorosaurians like Incisivosaurus and Microvenator remain rare, and ancestral forms expected in the Late Jurassic are yet to be discovered, although some authors have suggested Epidexipteryx and possibly other scansoriopterygids may represent early-diverging oviraptorosaurians. Long-armed scansoriopterygids from the Middle-Late Jurassic of Laurasia are either early-diverging oviraptorosaurians or paravians, and some have considered them to be early-diverging avialans. Known from five (or possibly six) feathered specimens from China, only two mature individuals exist, representing these taxa. These taxa, Yi and Ambopteryx, preserve stylopod-supported wing membranes that are the only known alternative to the feathered, muscular wings that had been exclusively associated with dinosaurian flight. Thus, scansoriopterygid specimens-particularly those preserving soft tissue-remain a key priority for future specimen collection. Dromaeosaurids and troodontids were first discovered in North America and Mongolia in Late Cretaceous rocks. More recent discoveries show that these animals originated in the Late Jurassic, were strikingly feathered, lived across diverse climes and environments, and at least in the case of dromaeosaurids, attained a global distribution and the potential for aerial locomotion at small size.
... The hooked denticles of Troodontidae tend to be particularly large, bulbous, and widely separated, being strongly different from the denticles of Dromaeosauridae. According to Hendrickx et al. (2019), between dromaeosaurids, hooked denticles are present in the eudromaeosaurians Atrociraptor (TMP 1995.166.01;Currie and Varricchio, 2004; fig. 14.7) and Saurornitholestes (Currie et al., 1990;Sankey, 2001). ...
The upper Barremian (Lower Cretaceous) palaeontological site of Vadillos-1 is located
in the North of the Cuenca Province, Spain. It includes a sedimentary succession in
“Weald” facies of brown and grey mudstones and red clays, corresponding to an
alluvial-palustrine muddy floodplain. Among the collected fossils, there are several
vertebrate remains belonging to theropod dinosaurs, including some teeth (VD1-197,
VD1-178, VD1-179, and VD1-180) that are described and identified for the first time.
The taxonomic assignment was approached following two methods beside the classical
consideration of their overall morphology: a cladistic analysis performed on a tooth
based data matrix, and a discriminant analysis performed on a large dataset including
measurements of non-avian theropod teeth. The DSDI>1.2 and the braided enamel
present seen in VD1-197 suggest that the specimen belongs to a Dromaeosauridae or a
non-tyrannosaurid Tyrannosauroidea, but the cladistics analysis classifies this tooth in
the latest. The analysis showed that VD1-178, VD1-179 and VD1-180 can be ascribed
to Dromaeosauridae. The dental features characteristic of this clade and present in our
specimens include a DSDI>1.2, labial and lingual depressions, and a braided enamel
surface texture, which allows to place these teeth more specifically within the
Eudromaeosauria. The results show, for the first time, the presence of dromaeosaurids
and possibly non-Tyrannosaurid Tyrannosauroidea at Vadillos-1, thus providing new
data to the European Barremian record, and contributing to the updating the geographic
distribution of these dinosaurs.
... This latter alternative would imply that the promaxillary fenestra of E. lengi must have been proportionally large compared to that of Guanlong, Dilong, Proceratosaurus, Bistahieversor and tyrannosaurids (Xu et al., 2004(Xu et al., , 2006Carr, Williamson & Schwimmer, 2005;Carr & Williamson, 2010;Rauhut, Milner & Moore-Fay, 2010;Brusatte, Carr & Norell, 2012). The promaxillary fenestra is both comparatively large, and visible in lateral view, in some maniraptorans (Currie & Varricchio, 2004). However, the typical condition for tyrannosauroids is that the promaxillary fenestra is smaller than the maxillary fenestra and tucked up against the rim of the antorbital fossa such that it is partly concealed from lateral view (Xu et al., 2004(Xu et al., , 2006Carr, Williamson & Schwimmer, 2005;Carr & Williamson, 2010;Rauhut, Milner & Moore-Fay, 2010;Brusatte, Carr & Norell, 2012). ...
Eotyrannus lengi Hutt et al., 2001 from the Lower Cretaceous Wessex Formation (part of the Wealden Supergroup) of the Isle of Wight, southern England, is described in detail, compared with other theropods, and evaluated in a new phylogenetic analysis. Eotyrannus is represented by a single individual that would have been c. 4.5 m long; it preserves the anterior part of the skull, a partial forelimb and pectoral girdle, various cervical, dorsal and caudal vertebrae, rib fragments, part of the ilium, and hindlimb elements excluding the femur. Lack of fusion with regard to both neurocentral and sacral sutures indicates subadult status. Eotyrannus possesses thickened, fused, pneumatic nasals with deep lateral recesses, elongate, tridactyl forelimbs and a tyrannosaurid-like scapulocoracoid. The short preantorbital ramus of the maxilla and nasals that are approximately seven times longer than they are wide show that Eotyrannus was not longirostrine. A posterodorsally inclined ridge on the ilium's lateral surface fails to reach the dorsal margin: a configuration seen elsewhere in Juratyrant. Eotyrannus is not arctometatarsalian. Autapomorphies include the presence of curving furrows on the dentary, a block-like humeral entepicondyle, and a distoproximally aligned channel close to the distolateral border of the tibia. Within Tyrannosauroidea, E. lengi is phylogenetically intermediate between Proceratosauridae and Yutyrannus and the clade that includes Xiongguanlong, Megaraptora, Dryptosaurus and Tyrannosauridae. We do not find support for a close affinity between Eotyrannus and Juratyrant. Our analysis supports the inclusion of Megaraptora within Tyrannosauroidea and thus increases Cretaceous tyrannosauroid diversity and disparity. A proposal that Eotyrannus might belong within Megaraptora, however, is based on character states not present in the taxon. Several theropods from the Wessex Formation are based on material that overlaps with the E. lengi holotype but none can be shown to be synonymous with it. Subjects Paleontology, Zoology
... RCPS-VJ2003 can be readily distinguished from Dromaeosaurinae for the absence of serrations on the mesial carina. RCPS-VJ2003 resembles Microraptorinae (e.g., Microraptor, Wulong, Changyuraptor, Graciliraptor and Tianyuraptor), Velociraptorinae (e.g., Tsaagan and Velociraptor) and Saurornitholestinae whose mesial denticles are minute or absent (Currie et al. 1990;Burnham et al. 2000;Xu et al. 2000Xu et al. , 2010Hwang et al. 2002;Currie and Varricchio 2004;Xu and Wang 2004a;Norell et al. 2006;Lü et al. 2007;Godefroit et al. 2008;Zheng et al. 2010;Han et al. 2014;Chiarenza et al. 2020;Currie and Evans 2020;Poust et al. 2020). ...
Recently, a new fossil site containing microvertebrate remains has been discovered in the upper part of the Nenjiang Formation (early Campanian) in the Songliao Basin, northeast China. Five isolated theropod teeth were discovered. The teeth were analysed based on morphological traits and the results showed that they correspond to the clades of Troodontidae, Dromaeosauridae and ?Tyrannosauridae. One dromaeosaurid tooth can be furtherly assigned to Dromaeosaurinae. It is the first discovery of theropod teeth from the Nenjiang Formation, also the first record of the Dromaeosaurinae from China. This study extends the known geographic range of these clades of theropods. The new materials also expand knowledge of the terrestrial ecosystem during the Late Cretaceous of the Songliao Basin.
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.
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