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Anatomy of Patagonykus puertai (Theropoda, Avialae, Alvarezsauridae), from the Late Cretaceous of Patagonia

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Abstract

The fragmentary skeleton of a new Late Cretaceous avialan theropod from Patagonia is described. Patagonykus puertai possesses caudal trunk vertebrae that are slightly convex caudally. The last sacral centrum is ball-shaped caudally, a condition that is also found in the caudal vertebrae. Caudal synsacral vertebrae are keeled ventrally. The humérus is craniocaudally compressed, and the internal tuberosity is unusually robust. Distally, the humerus has only one large subspherical condyle for articulation with the ulna and radius. The ulnar olecranon is strongly developed. The carpometacarpal is dorsoventrally compressed and quadrangular in dorsal view. Phalanx 1 of digit I has a pair of strong proximoventral hooklike processes. The ilium lacks the cranioventral fossa for the origin of the femoral protractor M. cuppedicus. The pubic pedicel of the ilium is cranioventrally oriented. The long and slender pubis is caudoventrally directed and ends distally in a massive pubic “foot”. The presence of a deep proximal socket on the calcaneum suggests that the fibula was in articulation with the tarsus. Metatarsal III is proximally narrower than metatarsals II and IV.Patagonykus puertai is closely related to another Patagonian taxon, Alvarezsaurus calvoi, and also to the Mongolian Mononykus olecranus. Alvarezsauridae encompass these three taxa, sharing outstanding synapomorphies such as procoelous sacral and caudal vertebrae, and a stout ungual in the first digit of the manus. The Patagonian taxa are geologically older and morphologically more primitive than Mononykus olecranus. Alvarezsauridae documents a group of theropods widely distributed in late Mesozoic times, relevant to discussions of bird origins.
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... Asimismo, las formas intermedias conocidas recientemente para este clado son registradas a partir del Cretácico Inferior de China, incluyendo a Xiyunykus pengi proveniente del Grupo Tugulu (Barremiano-Aptiano; , Bannykus wulatensis de la Formación Bayingobi (Aptiano; Xu et al., 2018), y Tugulusaurus faciles de la Formación Lianmugin (Barremiano-Aptiano; Dong, 1973;Xu et al., 2018). En cuanto a las formas patagónicas, estas se conocen a partir del Cretácico Superior, y sus holotipos constan de elementos fragmentarios a parcialmente completos tales como Alnashetri cerropoliciensis de la Formación Candeleros (Cenomaniano; ; Patagonykus puertai de la Formación Portezuelo (Turoniano-Coniaciano; Novas, , 1997, Alvarezsaurus calvoi y Achillesaurus manazzonei provenientes de la Formación Bajo de la Carpa (Santoniano; , y Bonapartenykus ultimus de la Formación Allen (Campaniano medio-Maastrichtiano bajo; Agnolin et al., 2012). No obstante, los dos taxones provenientes de la Formación Bajo de la Carpa han sido propuestos como sinónimos . ...
... En la Cuenca Neuquina se han encontrado alvarezsáuridos tanto en depósitos fluviales como eólicos Novas, , 1997Salgado et al., 2009;Agnolin et al., 2012;. Se ha observado una tendencia similar en Parvicursorinae, cuyos restos se han encontrado en depósitos pertenecientes a canales fluviales entrelazados (Naish y Dyke, 2004;Averianov y Sues, 2017), fluviales serpenteantes Nesbitt et al., 2011), deltaico fluvial , llanuras de inundación fluviales con canales de estuarios y pantanos (Longrich y Currie, 2009), aluviales y eólicos (Perle et al., 1993;Karhu y Rautian, 1996;Chiappe et al., 1998;Alifanov y Barsbold, 2009;Turner et al., 2009;Lee, 2018). ...
... 1º Objetivo-Realizar un estudio osteológico detallado del esqueleto de los Alvarezsauridae Alvarezsaurus calvoi (MUCPv 54;, Patagonykus puertai (MCF PVPH 37/38;Novas, , 1997, cf. Patagonykus puertai (MCF PVPH 102; , Achillesaurus manazzonei , 4º Objetivo-Realizar un análisis cladístico de Alvarezsauria a partir de un set de datos propios generado y contrastar hipótesis previas de relaciones filogenéticas referidas a este clado de terópodos coelurosaurios. ...
Thesis
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.
... Early-diverging alvarezsauroids are known from the Late Jurassic and Early Cretaceous of China (Choiniere et al., 2010(Choiniere et al., , 2014a(Choiniere et al., , 2014bXu et al., 2018;Qin et al., 2019). Non-parvicursorine alvarezsaurids were present in the Late Cretaceous of North and South America (Bonaparte, 1991;Novas, 1996Novas, , 1997Martinelli and Vera, 2007;Longrich and Currie, 2009;Agnolin et al., 2012). Parvicursorinae, the most derived clade of Alvarezsauridae, was widely distributed in Asia and North America during the Late Cretaceous (Perle et al., 1993(Perle et al., , 1994Karhu and Rautian, 1996;Chiappe et al., 1998Chiappe et al., , 2002Suzuki et al., 2002;Alifanov and Barsbold, 2009;Xu et al., 2010Xu et al., , 2011Xu et al., , 2013Nesbitt et al., 2011;Hone et al., 2013;Lü et al., 2018;Lee et al., 2019;Fowler et al., 2020;Freimuth and Wilson, 2021;Lopatin, 2021, 2022). ...
... The humerus ZIN PH 2619/16 closely resembles that of Patagonykus (Novas, 1996(Novas, , 1997 in overall proportions. Its head and internal tuberosity have similar relative sizes but are not as clearly delineated and the proximal end of the internal tuberosity is not truncated. ...
... These differences are likely ontogenetic, with ZIN PH 2021/16 representing a juvenile and ZIN PH 2020/16 an adult animal. Two small facets distal to the humeral articular facet on the ulna ZIN PH 2020/ 16 possibly contacted the two small proximolateral surfaces on the radius, similar to those present in Patagonykus (Novas, 1997). In Mononykus and Trierarchuncus, the radius articulated with the ulna by a proximal sutural contact and a distal aponeurosis tubercle (Perle et al., 1994;Fowler et al., 2020). ...
Article
A new alvarezsaurid theropod, Dzharaonyx eski, gen. et sp. nov., is documented by a variety of dissociated but well-preserved postcranial bones from the Upper Cretaceous (Turonian) Bissekty Formation at Dzharakuduk, Uzbekistan. It has opisthocoelous posterior dorsal vertebrae lacking infrapostzygapophyseal fossae. The posterior caudal vertebrae are procoelous and have a longitudinal canal within the neural arch. The humerus is intermediate in structure between those of the Argentinian alvarezsaurid Patagonykus and the Mongolian parvicursorine Mononykus in having a small internal tuberosity, similar-sized radial and ulnar condyles, a distally protruding radial condyle, and a greatly reduced entepicondyle. The ulna has a hypertrophied olecranon process, a globular carpal trochlea, and a facet for the aponeurosis tubercle of the radius. On the carpometacarpus, the articular surface of metacarpal III is in line with the distal articular joint of metacarpal II. On manual phalanx II-1, the flexor ridges are similarly developed and the dorsolateral process and the ‘hook-like’ ventrolateral process are absent. The collateral grooves on manual ungual phalanx II-2 are either partially open or completely enclosed to form ventral foramina. The pubis bears a preacetabular tubercle. The pes is arctometatarsalian. Metatarsal II forms a posterolateral flange. Pedal phalanx IV-1 has a protruding proximomedial process, a proximoventral notch, and asymmetrical distal condyles. The flexor tubercles on the pedal ungual phalanges are small. Phylogenetic analysis found Dzharaonyx within Parvicursorinae in a polytomy with other Asiatic taxa. Dzharaonyx is the most plesiomorphic and geologically oldest member of Parvicursorinae known to date.
... This is a synapomorphy (283[2]) for the clade including Nemegtonykus and Parvicursorinae (Fig. 23). In Alvarezsaurus and Patagonykus at least the anterior and middle dorsal vertebrae are amphicoelous (Bonaparte 1991;Novas 1996Novas , 1997. The posterior part of a dorsal vertebra of Patagonykus with a strongly convex centrum articulation surface (Novas 1996, fig. ...
... Ceratonykus and Nemegtonykus (Perle et al. 1994;Novas 1996Novas , 1997Alifanov & Barsbold 2009;Lee et al. 2019). This character is likely to be subject to ontogenetic and individual variation and therefore has little phylogenetic value. ...
... In Patagonykus, Parvicursor and Linhenykus the popliteal fossa is open distally, with a wide space separating the medial condyle from the ectocondylar tuber in distal view (Novas 1997;Xu et al. 2013). In contrast, in Xixianykus, Mononykus and Shuvuuia the medial condyle and the ectocondylar tuber are close to each other in distal view, closing the popliteal fossa distally (Perle et al. 1994;Xu et al. 2010). ...
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Parvicursor remotus Karhu & Rautian, 1996 Karhu, A. A. & Rautian, A. S. 1996. A new family of Maniraptora (Dinosauria: Saurischia) from the Late Cretaceous of Mongolia. Paleontological Journal, 30, 583–592. [Google Scholar], based on a fragmentary skeleton from the Campanian Barungoyot Formation at Khulsan, in the Gobi Desert of Mongolia, is re-described in detail. Contrary to the original description, we find no evidence that the last dorsal vertebra is opisthocoelous. A biconvex last dorsal vertebra could be present in Parvicursor as in other parvicursorines. The transversely compressed sacral centrum with a sharp ventral keel is the last sacral, not the first sacral as originally alleged. The pelvic bones are not fused at the acetabulum. The holotype of P. remotus, the smallest known alvarezsaurid specimen, is a juvenile individual far from skeletal maturity. New morphological details of Parvicursor that are revealed include a ventral ridge on the posterior dorsal vertebrae; a horizontal supraacetabular crest of the ilium whose anterior end is placed anterior to the most ventrally projecting part of the pubic peduncle; the possible presence of a pubic obturator foramen; an entocondylar tuber on the femur; internal flexor flanges on metatarsals II and IV; a lateral flexor ridge on metatarsal IV; and a proximoventral notch on pedal phalanx IV-1. The Tugriken Shireh alvarezsaurid is not referable to Parvicursor because of its much larger ungual phalanx on the second pedal digit. Kol ghuva is excluded from Alzarezsauridae. The two successive sister taxa for Parvicursor are Ceratonykus and Linhenykus. Ceratonykus differs little from Parvicursor and might be a synonym of the latter. Linhenykus is very similar to Parvicursor in all overlapping skeletal elements. The Parvicursorinae includes all Asian Late Cretaceous alvarezsaurids except Qiupanykus and Nemegtonykus.
... This is particularly true for theropod dinosaurs. The Late Cretaceous South American theropod record is taxonomically diverse and comprised of widely divergent clades, including Noasauridae (Bonaparte and Powell, 1980;Bonaparte, 1991), Abelisauridae (Bonaparte, 1985;Bonaparte and Novas, 1985;Aranciaga Rolando et al., 2021), Carcharodontosauridae (Coria and Salgado, 1995;Novas and Pol, 2005;Canale et al., 2014;Canale et al., 2022), Megaraptoridae (Novas, 1998;Porfiri et al., 2014;Coria and Curie, 2016), early diverging coelurosaurs (Kellner, 1999;Novas et al., 2012), alvarezsaurs (Novas et al., 1997), and paravians including avialans (Chiappe and Walker, 2002;Makovicky et al., 2005;Agnolín and Martinelli, 2008;Novas et al., 2008b;Agnolín et al., 2017). To date, the southernmost non-Antarctic record of non-avian theropods comes from the Santa Cruz Province in Argentinean Patagonia, which includes the abelisauroid Austrocheirus isasii and the megaraptorid Orkoraptor burkei (Novas et al., 2008a) both from the Cerro Fortaleza Formation (Campanian-Maastrichtian), and the recently described megaraptorid Maip macrothorax (Aranciaga from the Chorrillo Formation (Campanian-Maastrichtian). ...
... The teeth of H. escuilliei are recurved with slight carinae, are elliptical in cross section, and appear to have convex sides (Cau et al., 2017) but are described as completely lacking denticles (Cau et al., 2017) as in known alvarezsaurids (see Altangarel et al., 1994;Hendrickx et al., 2019). Other taxa recovered from South America do not have described dentition (Novas, 1997), precluding comparison. ...
... 19A,19B,. Similar structures are known in alvarezsaurids (Novas, 1996(Novas, , 1997, oviraptorosaurs (Osmólska, Currie & Barsbold, 2004), therizinosauroids (Barsbold, 1976;Perle, 1981;Clark, Marya nska & Barsbold, 2004;Kirkland et al., 2005) and dromaeosaurids (Ostrom, 1969;Brinkman, Cifelli & Czaplewski, 1998). The massive entepicondyle of alvarezsaurids is bulbous, subconical and slightly curved medioproximally (Novas, 1996(Novas, , 1997, unlike the more block-like, medially projecting structure of E. lengi. ...
... Similar structures are known in alvarezsaurids (Novas, 1996(Novas, , 1997, oviraptorosaurs (Osmólska, Currie & Barsbold, 2004), therizinosauroids (Barsbold, 1976;Perle, 1981;Clark, Marya nska & Barsbold, 2004;Kirkland et al., 2005) and dromaeosaurids (Ostrom, 1969;Brinkman, Cifelli & Czaplewski, 1998). The massive entepicondyle of alvarezsaurids is bulbous, subconical and slightly curved medioproximally (Novas, 1996(Novas, , 1997, unlike the more block-like, medially projecting structure of E. lengi. In oviraptorosaurs the entepicondyle has been described as projecting anteriorly (Osmólska, Currie & Barsbold, 2004, p. 175). ...
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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
... The Alvarezsauridae is a group of theropod dinosaurs known from the Upper Cretaceous of Asia, North and South America (Bonaparte, 1991;Perle et al., 1993Perle et al., , 1994Chiappe et al., 1996Chiappe et al., , 1998Chiappe et al., , 2002Karhu and Rautian, 1996;Sereno, 2001;Suzuki et al., 2002;Alifanov and Barsbold, 2009;Longrich and Currie, 2009;Xu et al., 2010Xu et al., , 2011Xu et al., , 2013Nesbitt et al., 2011;Agnolin et al., 2012;Hone et al., 2013;Pittman et al., 2015;Averianov and Sues, 2017;Lee et al., 2019;Ding et al., 2020;Fowler et al., 2020;Averianov and Lopatin, 2022). The non-alvarezsaurid alvarezsauroids are known from the Upper Jurassic e Lower Cretaceous of Asia and Upper Cretaceous of South America (Novas, 1996(Novas, , 1997Choiniere et al., 2010;Agnolin et al., 2012;Choiniere et al., 2014;Xu et al., 2018;Qin et al., 2019), suggesting that the group was originated in Asia and dispersed early in South America were primitive taxa survived until the end of the Cretaceous (Agnolin et al., 2012). The most diverse alvarezsaurids are united in the clade Parvicursorinae, which is known exclusively, or almost exclusively from the Upper Cretaceous of Asia (attribution of poorly known alvarezsaurid taxa from the Upper Cretaceous of Europe and North America to this clade is not certain). ...
Article
Ondogurvel alifanovi gen. et sp. nov. (Alvarezsauridae, Parvicursorinae) is described based on a partial postcranial skeleton from the Upper Cretaceous (Campanian) Barungoyot Formation at the Nemegt locality in Mongolia. The new taxon differs from all other alvarezsaurids in having metatarsals II and IV completely fused along their contact area. The phylogenetic analysis places Ondogurvel in a clade with the Late Cretaceous Asiatic parvicursorines Xixianykus and Albinykus, which have proximally co-ossified metatarsals II and IV. Two morphological types of the parvicursorine carpometacarpus can be recognized. In the first type exemplified by Mononykus and Ondogurvel, the articular surfaces of metacarpals III and IV are located along the lateral margin of the carpometacarpus and small, but functional digits III and IV were flexed in a plane almost perpendicular to the flexion plane of digit II. In the second type exemplified by the Bissekty alvarezsaurid and Linhenykus, the articular surface of metacarpal IV is missing and the articular surface of metacarpal III is located along the distal margin of the carpometacarpus, in line with the distal condyles of metacarpal II. In this case, the small functional digit III was flexing in the same plane as the main digit II. Linhenykus has the carpometacarpus of the second type, but the distal articular surface of metacarpal III is greatly reduced and manual finger III was apparently absent. This drastic difference in the morphology of the carpometacarpus may suggest a deep divergence between the parvicursorine lineages represented by the Bissekty alvarezsaurid – Linhenykus and Mononykus – Ondogurvel.
... 26F, 27F). Only the posterior half of the isolated sacral vertebra shows a keeled ventral surface (Fig. 27F), less prominent than those in alvarezsaurids (Perle et al., 1994;Novas, 1997). Pneumatic foramina are absent on lateral surfaces of sacral vertebrae, whereas a pleurocentral depression is present on each lateral side of the first centrum (Fig. 26C, E). ...
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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.
... The Neuquén Group is the principal lithostratigraphic unit regarding the theropod fossil record in northern Patagonia (e.g., Leanza et al., 2004;Garrido, 2010), and it is subdivided in nine formations that mainly encompass the Upper Cretaceous (middle Cenomanian-middle Campanian) (Garrido, 2010). however, theropod remains are scarce from the Río Neuquén Subgroup (Portezuelo, Los Bastos, Sierra Barrosa and Plottier formations; middle Turonian-lower Santonian), except for the Portezuelo Formation (Novas, 1997(Novas, , 1998Novas & Puerta, 1997;Calvo et al., 2004a;Novas & Pol, 2005). This paucity of theropods mainly affects the allosauroid record, since only two specimens have been recorded from the middle Late Cretaceous (Coria & Currie, 2016;Porfiri et al., 2018). ...
Article
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The Late Cretaceous theropod fauna of South America is composed of Abelisauridae, Noasauridae, Spinosauridae, Carcharodontosauridae, Megaraptora, and Coelurosauria. These groups include mostly small (Noasauridae and Coelurosauria) and medium- tolarge-sized taxa (Carcharodontosauridae, Abelisauridae, and Megaraptora). Some of these lineages are predominantly Gondwanic (Abelisauridae, Noasauridae, Carcharodontosauridae, Megaraptora) and poorly represented in Laurasian landmasses. Particularly, several theropods have been reported from Patagonia, known either due to distinct anatomical features or due to their high degree of preservation, such as Carnotaurus, Skorpiovenator, Giganotosaurus, Megaraptor, Alvarezsaurus, and Unenlagia. Here we describe a new incomplete tibia (MAU-PV-CM-653) from the Sierra Barrosa Formation (middle Coniacian, Upper Cretaceous), Patagonia, Argentina. MAU-PV-CM-653 shows an anteroposteriorly reduced cnemial crest that is strongly curved laterally. Finally, the tibia lacks a proximal extension of the fibular crest. These traits are reminiscent of tetanuran morphology and, together with the stratigraphic provenance of MAU-PV-CM-653, they allow us to assign it to an allosauroid theropod, thus improving the Allosauroidea global record for the middle Late Cretaceous.
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Alvarezsauroidea (Tetanurae) are non‐avian theropod dinosaurs whose forelimb evolution is characterised by overdevelopment of digit I, at the expense of the other two digits, complemented by a drastic forelimb shortening in derived species (Parvicursorinae). These variations are recognised as evolutionary developmental anomalies. Evolutionary teratology hence leads to a double diagnosis with 1) macrodactyly of digit I and microdactyly of digits II and III, plus 2) anterior micromelia. The teratological macrodactyly/microdactyly coupling evolved first. Developmental mechanisms disturbing limb proportion are thought to be convergent with those of other Tetanurae (Tyrannosauridae, Carcharodontosauridae). As for the manual anomalies, both are specific to Alvarezsauroidea (macrodactyly/microdactyly) and inherited (digit loss/reduction). While considering the frame‐shift theory, posterior digits develop before the most anterior one. There would therefore be a decrease in the area devoted to digits II (condensation 3) and III (condensation 4), in connection with the Shh signalling pathway, interacting with other molecular players such as the GLI 3 protein and the Hox system. Developmental independence of digit I (condensation 2) would contribute to generate a particular morphology. Macrodactyly would be linked to a variation in Hoxd‐13, impacting Gli3 activity, increasing cell proliferation. The loss/reduction of digital ray/phalanges (digits II and III), would be associated to Shh activity, a mechanism inherited from the theropodan ancestry. The macrodactyly/macrodactyly coupling, and then anterior micromelia, fundamentally changed the forelimb mechanical function, compared to the 'classical' grasping structure of basal representatives and other theropods. The distal ossification of the macrodactylian digit has been identified as physiological, implying the use of the structure. However, the debate of a particular 'adaptive' use is pointless since the ecology of an organism is interactively complex, being both at the scale of the individual and dependent on circumstances. Other anatomical features also allow for compensation and a different predation (cursorial hindlimbs). This article is protected by copyright. All rights reserved.
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