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Este libro es una reseña histórica de los primeros catorce años de actividad del equipo de investigación sobre dinosaurios de la Universidad Nacional de la Patagonia San Juan Bosco (1983-1997), la primera institución de la Patagonia en desarrollar esa línea de investigación. Junto a cada uno de los descubrimientos paleontológicos y su valoración científica, se relatan muchas anécdotas que reflejan el quehacer cotidiano del paleontólogo en el campo, la progresiva consolidación de un equipo que ha aportado al conocimiento universal varias y novedosas formas de vida de los dinosaurios del Cretácico tardío de la Patagonia Central. Fil: Martínez, Rubén Darío. Universidad Nacional de la Patagonia "San Juan Bosco". Facultad de Ciencias Naturales - Sede Comodoro; Argentina Fil: Rodriguez, Jorge Francisco. Universidad Nacional de la Patagonia "San Juan Bosco". Facultad de Ciencias Naturales - Sede Comodoro; Argentina Fil: Luna, Marcelo. Universidad Nacional de la Patagonia "San Juan Bosco". Facultad de Ciencias Naturales - Sede Comodoro; Argentina Fil: Ibiricu, Lucio Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico de Geología y Paleontología; Argentina Fil: Casal, Gabriel. Universidad Nacional de la Patagonia "San Juan Bosco". Facultad de Ciencias Naturales - Sede Comodoro; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

RESUMEN En este trabajo se reporta por primera vez la presencia de estromatolitos en afloramientos cretácicos en la localidad nacientes del río Chico en la Cuenca del Golfo San Jorge. Los mismos se encuentran en la parte superior de la Formación Lago Colhué Huapi (Coniaciano-Maastrichtiano), unidad correspondiente al Grupo Chubut. La presencia de, hasta el momento, cuatro estructuras interpretadas como estromatolitos en esta localidad, no solo tiene importancia por ser el primer registro en la cuenca, sino porque contribuye al conocimiento de estas bioconstrucciones en los ambientes continentales. Se caracteriza y discute en detalle el estromatolito denominado E1, que se encuentra asociado a un abundante y diverso registro fósil, representado por palinomorfos, fragmentos de troncos silicificados, restos de dinosaurios y cáscaras de huevos de dinosaurios. El estudio, integrado fundamentalmente con el polen y las esporas registradas, es importante para las interpretaciones paleoambientales del sitio y contribuye al entendimiento paleoecológico y paleoclimático del intervalo estratigráfico más moderno del Grupo Chubut. ABSTRACT The presence of stromatolites from Cretaceous outcrops at the headwaters of the río Chico locality in the Golfo San Jorge Basin is reported for the first time. They are present in the uppermost part of the Lago Colhué Huapi Formation (Coniacian-Maastrichtian) of the Chubut Group. The presence of, up to now, four structures interpreted as stromatolites in this locality are not only important because it is the first record in the basin, but because it contributes to the knowledge of these bioconstructions in continental environments. The stromatolite called E1, which is characterized and discussed in detail, is associated with an abundant and diverse fossil record represented by palynomorphs, fragments of silicified trunks, dinosaur remains and eggshells. The study, integrated mainly with the recorded pollen and spores, is important for paleoenvironmental interpretations of the site and contributes to the paleoecological and paleoclimatic understanding of the most modern stratigraphic interval of the Chubut Group.

RESUMEN En este trabajo se proporciona nueva información sedimentológica y fosildiagenética de restos de cuatro dinosaurios preservados en depósitos de diferentes subambientes fluviales de la sección media de la Formación Lago Colhué Huapi, en la Cuenca del Golfo San Jorge. En todos los casos, la estructura ósea originalmente constituida por hidroxiapatita fue modificada por sustitución iónica a francolita. Los restos fósiles contenidos en litoarenitas finas con alta participación de arcillas que sufrieron fuerte compactación, exhiben deformación plástica e intensa fracturación, que afectó la microestructura ósea. La francolita presenta una textura cavernosa con alto índice de cristalinidad y un menor contenido en carbonato que evidencia procesos de disolución del mineral en un medio ácido. La hematita presente externamente como costras y nódulos, e internamente en los bordes de los canales vasculares, se vincula a la precipitación de óxidos de hierro en zonas bien oxigenadas relacionadas con fluctuaciones del nivel freático. La permineralización de los canales vasculares con hematita, y con cristales bien desarrollados de fluorapatita de neoformación habría ocurrido durante la diagénesis temprana. En contraste, los restos fósiles contenidos en litoarenitas gruesas con escasas arcillas sufrieron menos compactación y están mejor preservados. En estos casos, la francolita presenta una textura maciza con menor índice de cristalinidad y mayor contenido en carbonato. La permineralización de los canales vasculares con hematita y con cristales bien desarrollados de calcita habría ocurrido en un medio alcalino y durante la diagénesis tardía. En los cuatro casos de estudio pudo determinarse que los índices de cristalinidad de la francolita y los contenidos en carbonato, suponen una correlación positiva del índice con el incremento relativo del contenido de flúor y el aumento de la fragilidad de los restos fósiles. De esta manera, los estudios sedimentológicos y fosildiagenéticos, en particular los procesos de permineralización en las cavidades vasculares, permiten aproximarnos al conocimiento de las condiciones físicas y químicas existentes durante la litificación y fosilización de los restos en diferentes subambientes fluviales de la Formación Lago Colhué Huapi. ABSTRACT New sedimentological and fossil-diagenetic information from remains of four dinosaurs is herein provided. The fossil material was preserved in deposits of different fluvial sub-environments from the middle section of the Lago Colhué Huapi Formation, Golfo San Jorge Basin. In all the studied cases, the bone structure originally constituted by hydroxyapatite was modified by ionic substitution to francolite. The fossil remains contained in fine lithoarenites with high clay minerals content, affected by lithostatic compression, exhibit plastic deformation and intense fracturing which affected the bone microstructure. The francolite presents cavernous texture with high crystallinity index and a lower carbonate content, evidencing processes of mineral dissolution in an acidic environment. The hematite is present as crusts and nodules on the surface of the bones and internally at the edges of the vascular channels. It is related to the precipitation of iron oxide in well oxygenated areas with fluctuating water table. The permineralization of the vascular channels with hematite and well-developed crystals of fluorapatite of neoformation, would have occurred during the early diagenesis. By contrast, the fossil remains contained in coarse lithoarenites with scarce clay minerals, have been less affected by lithostatic compression and are better preserved. The francolite exhibits a massive texture with a lower index of crystallinity and higher carbonate concentration. The permineralization of the vascular channels with hematite and well-developed crystals of calcite would have occurred in an alkaline environment during the late diagenesis. In the four study-cases it could be determined that the crystallinity indexes of the francolite and the carbonate content, display a positive correlation with the relative increase of fluorine content and the fragility of the fossil remains. Therefore, the sedimentological and fossil-diagenetic studies, in particular the permineralization processes in the vascular channels, enhance our understanding of the physical and chemical conditions that prevailed during the lithification and fossilization of the remains in different fluvial sub-environments from the Lago Colhué Huapi Formation.

RESUMEN En este trabajo se proporciona nueva información sedimentológica y fosildiagenética de restos de cuatro dinosaurios preservados en depósitos de diferentes subambientes fluviales de la sección media de la Formación Lago Colhué Huapi, en la Cuenca del Golfo San Jorge. En todos los casos, la estructura ósea originalmente constituida por hidroxiapatita fue modificada por sustitución iónica a francolita. Los restos fósiles contenidos en litoarenitas finas con alta participación de arcillas que sufrieron fuerte compactación, exhiben deformación plástica e intensa fracturación, que afectó la microestructura ósea. La francolita presenta una textura cavernosa con alto índice de cristalinidad y un menor contenido en carbonato que evidencia procesos de disolución del mineral en un medio ácido. La hematita presente externamente como costras y nódulos, e internamente en los bordes de los canales vasculares, se vincula a la precipitación de óxidos de hierro en zonas bien oxigenadas relacionadas con fluctuaciones del nivel freático. La permineralización de los canales vasculares con hematita, y con cristales bien desarrollados de fluorapatita de neoformación habría ocurrido durante la diagénesis temprana. En contraste, los restos fósiles contenidos en litoarenitas gruesas con escasas arcillas sufrieron menos compactación y están mejor preservados. En estos casos, la francolita presenta una textura maciza con menor índice de cristalinidad y mayor contenido en carbonato. La permineralización de los canales vasculares con hematita y con cristales bien desarrollados de calcita habría ocurrido en un medio alcalino y durante la diagénesis tardía. En los cuatro casos de estudio pudo determinarse que los índices de cristalinidad de la francolita y los contenidos en carbonato, suponen una correlación positiva del índice con el incremento relativo del contenido de flúor y el aumento de la fragilidad de los restos fósiles. De esta manera, los estudios sedimentológicos y fosildiagenéticos, en particular los procesos de permineralización en las cavidades vasculares, permiten aproximarnos al conocimiento de las condiciones físicas y químicas existentes durante la litificación y fosilización de los restos en diferentes subambientes fluviales de la Formación Lago Colhué Huapi.

This paper reports on the biostratigraphic, paleobiogeographic and paleoecologic aspects of palynoflora recovered from sedimen- tary rocks preliminarily assigned to the Lago Colhué Huapi Formation, in the Golfo San Jorge Basin. The present palynological assemblage includes Maastrichtian marker species of the austral Proteacidites/Nothofagidites Province such as Quadraplanus brossus and Tubulifloridites lilliei. Typical species of the Maastrichtian paleotropical Palmae Province, Buttinia andreevi and Gabonisporis vigourouxii, are also recognized in the palynoflora. These facts indicate the mixed character of the paleoflora and the prevalence of transitional climatic conditions at the paleolatitude of the Chubut Province in the uppermost Cretaceous. The palynoflora composition suggests the local existence of a warm and low energy freshwater body.

Las características litológicas, estratigráficas y paleontológicas del registro más moderno del Grupo Chubut en la Cuenca del Golfo San Jorge (Argentina), permiten proponer una nueva unidad litoestratigráfica dentro del grupo, la Formación Lago Colhué Huapi (nov. nom.). Esta unidad se dispone por encima de la Formación Bajo Barreal y por debajo de la Formación Laguna Palacios o de la Formación Salamanca. La base y el techo son transicionales, con excepción del contacto con la Formación Salamanca que en algunos casos es erosivo. Sus afloramientos se extienden ampliamente en el ámbito de la cuenca. Su localidad tipo se encuentra ubicada en las nacientes del río Chico y se propone un estratotipo compuesto: el holoestratotipo está constituido por el intervalo aflorante en las nacientes del río Chico (53 m de espesor), y el paraestratotipo es el intervalo aflorante en la margen sureste del Codo del río Senguerr (160 m de espesor). Los criterios para su reconocimiento consisten en la coloración rojiza de sus fangolitas y su posición estratigráfica. Se diferencia de la Formación Bajo Barreal (miembro superior) porque esta última se compone principalmente de fangolitas grises, mientras que se distingue de la Formación Laguna Palacios por la ausencia de niveles tobáceos y paleosuelos. En su localidad tipo se interpretó un paleoambiente fluvial con sistemas canalizados de alta sinuosidad con planicies de inundación bien drenadas, vinculados a un paleoclima semi-árido. El contenido paleontológico de restos de dinosaurios permitió definir una edad comprendida entre el Coniaciano-Maastrichtiano, y afinidades faunísticas con la Formación Allen de la Cuenca Neuquina. Lithologic, stratigraphic and paleontological features of the most recent record of the Chubut Group in the Golfo San Jorge Basin (Argentina), allowed us to propose the definition of a new lithostratigraphic unit in the Group: Lago Colhué Huapi Formation (nov. nom.). This unit overlies the Bajo Barreal Formation (Upper Member) and it is covered by the Laguna Palacios or Salamanca Formation. Although its base and top are transitional, this unit is sometimes limited by an erosional surface in its contact with the Salamanca Formation, and it is widely exposed in the basin. Its type locality is located in the headwaters of the Chico river and we propose a composed type-strata: the holostratotype is constituted by a stratigraphic section outcropped in the headwaters of the Chico river (53 m thick), and the parastratotype is the interval outcropped in the southeastern margin of the Senguerr river (160 m thick). Criteria for the recognition of the proposed unit are its reddish mudstones and the stratigraphic position. The Lago Colhué Huapi Fomation differs from the Bajo Barreal Formation (Upper Member) because the latter is characterized by grey mudstones. This unit also differs from Laguna Palacios Formation because of the absence of tuffaceous strata and paleosoils. In its type locality, we interpreted a fluvial paleo-environment with high-sinuosity channels and well-drained floodplains, probably developed under semiarid paleoclimatic conditions. The dinosaur record of the formation allowed us to define an age ranging between Coniacian-Maastrichtian, and faunistic affinities with the Allen Fomation of the Neuquén basin. Fil: Casal, Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de la Patagonia "San Juan Bosco". Facultad de Ciencias Naturales - Sede Comodoro. Departamento de Geología; Argentina Fil: Allard, Jose Oscar. Universidad Nacional de la Patagonia "San Juan Bosco". Facultad de Ciencias Naturales - Sede Comodoro. Departamento de Geología; Argentina Fil: Foix, Nicolas. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de la Patagonia "San Juan Bosco". Facultad de Ciencias Naturales - Sede Comodoro. Departamento de Geología; Argentina

Notohypsilophodon comodorensis Mart��nez, 1998 Figs. 2���10 Holotype. UNPSJB-Pv 942 (Figs 2���10). A partial skeleton including four cervical vertebrae, seven dorsal vertebrae, four sacral vertebrae, six caudal vertebrae (all of the vertebrae are partially preserved), rib fragment, a portion of the left scapula, right coracoid, right humerus, left and right ulnae, an incomplete left femur, right tibia, an incomplete left tibia, left fibula, an incomplete right fibula; right astragalus, left calcaneum and 13 pedal phalanges. Emended diagnosis. A small ornithopod dinosaur distinguished from all other basal ornithopods by the following autapomorphies originally proposed by Martinez (1998) and supported in this study: Anteromedial bulge on the proximal extremity of the tibia, calcaneum with a pronounced posterodistal projection. Additionally, the following new autapomorphies are proposed: Distal tip of the sacral neural spine strongly projected posteriorly, sternal process of the coracoids markedly reduced (see below). Locality and horizon. 28 km northeast of the town of Buen Pasto, in the central-south of Chubut Province, Patagonia, Argentina (Fig. 1). Bajo Barreal Formation, Lower Member (Late Cretaceous, Cenomanian, see Martinez & Novas 2006). Description and comparisons. As mentioned by Mart��nez (1998), the morphology of the material clearly differs from that seen in the most derived ornithopods (i.e., hadrosaurids). Likewise, the material does not possess synapomorphies or anatomical similarities of marginocephalians (i.e., pachycephalosaurs and ceratopsians). For this reason, members of both groups were excluded from our comparisons. Therefore, in order to ascertain the evolutionary affinities of Notohypsilophodon within Ornithischia, we compared the specimen to the following genera: basal neornithischians - Hexinlusaurus (Barrett et al. 2005) and Yandusaurus (He 1979; He & Cai 1984); basal (non-iguanodontian) ornithopods - Changchunsaurus (Zan et al. 2005; Butler et al. 2011), Gasparinisaura (Coria & Salgado 1996; Salgado et al. 1997), Gideonmantellia (Ruiz-Ome��aca et al. 2012), Haya (Makovicky et al. 2011), Hypsilophodon (Galton 1974 a; Torres & Viera 1994), Jeholosaurus (Xu et al. 2000; Han et al. 2012), Koreanosaurus (Huh et al. 2010), Orodromeus (Horner & Weishampel 1988), Oryctodromeus (Varricchio et al. 2007), Parksosaurus (Parks 1926; Galton 1973), Thescelosaurus (Gilmore 1915; Galton 1974 b; Boyd et al. 2009), Trinisaura (Coria et al. 2013), and Yueosaurus (Zheng et al. 2012); non-hadrosaurid iguanodontians - Anabisetia (Coria & Calvo 2002), Camptosaurus dispar; Camptosaurus prestwichii = Cumnoria prestwichii, Camptosaurus aphanoecetes = Uteodon aphanoecetes [Gilmore 1909; Galton and Powell 1980; Carpenter & Wilson 2008, see McDonald 2011), Dryosaurus (Janensch 1955; Galton 1981), Iguanodon (Norman 1980), Macrogryphosaurus (Calvo et al. 2007), Mantellisaurus (Hooley 1925; Norman 1986; Paul 2006, 2008; McDonald 2012), Mochlodon (��si et al. 2012), Ouranosaurus (Taquet 1976), Talenkauen (Novas et al. 2004), Tenontosaurus (Forster 1990; Winkler et al. 1997), Valdosaurus (Galton & Taquet 1982; Galton 2009; Barrett et al. 2011), and Zalmoxes (Nopcsa 1900; Weishampel et al. 2003). Additionally, other specimens (e.g., the Australian ornithopods) as well as isolated and partially persevered materials are also used in the present comparison (see below). Cervical vertebrae. The cervical vertebrae (Fig. 2) of Notohypsilophodon comodorensis, based on the morphology of the centra and the portions of the neural arches preserved are presumably middle cervicals. The centra are amphyplatian as in Haya, Hypsilophodon and Jeholosaurus. In more derived ornithopods (e.g., Camptosaurus, Cumnoria, Dryosaurus, Tenontosaurus, Valdosaurus and Zalmoxes), on the other hand, the cervical centra are slightly opisthocoelous or amphicoelous, as in Macrogryphosaurus. The centra of Notohypsilophodon are slightly wider than tall, as is the case in most basal neornithischians and basal ornithopods (e.g., Changchunsaurus, Hypsilophodon, Yueosaurus). In ornithopods more derived than Camptosaurus (see Galton 2009: fig. 20), Macrogryphosaurus and Talenkauen, the cervical centra are anteroposteriorly longer than tall. In lateral view, the centra are ���divided��� in two slightly concave surfaces as in basal ornithopods due to the presence of the longitudinal ridge at approximately centrum midheight. Ventrally, the cervical vertebrae of Notohypsilophodon exhibit a thin midline keel similar to those seen in Anabisetia, Changchunsaurus, Gasparinisaura, Hypsilophodon, Macrogryphosaurus, and Valdosaurus (see Barrett et al. 2011: fig. 2) and unlike the thicker, rugose ventral keels, present in some basal iguanodontids (e.g., Camptosaurus, Cumnoria, Tenontosaurus, Uteodon, Zalmoxes: Carpenter & Wilson 2008; Norman 2004). In anterior view, the cervical vertebrae have pentagonal articular surfaces with an acute ventral apex as the rhabdodontid ornithopod Zalmoxes (Weishampel et al. 2003: fig. 15) and the basal ornithopod Yueosaurus (Zheng et al. 2012: fig. 3); however, in the latter, the ventral apex is more pronounced than in Notohypsilophodon and Zalmoxes. The neural canal is proportionally large and ovoid in outline (a feature which could be related to the juvenile status of Notohypsilophodon, see below). The articular facets of the prezygapophyses are subcircular in outline and project strongly anterodorsally as in Hypsilophodon. Based on the preserved portion of the cervical neural spines, they appear to be notably reduced, a condition also reported in the basal ornithopods Hypsilophodon, Gasparinisaura and the basal iguanodontian Talenkauen. In lateral view, the centra exhibit an open neurocentral suture, indicating that Notohypsilophodon was not somatically mature (as Martinez 1998, pointed out in his original study, see below). A parapophysis located just below the neurocentral suture is also present in Tenontosaurus and Thescelosaurus. Dorsal vertebrae. The dorsal vertebrae (Fig. 3) are slightly amphicoelous and hourglass-shaped in ventral view as a consequence of their lateral compression. There are strongly-developed longitudinal striations around the margins of each of the articular surfaces, probably related to the insertion of soft tissues (i.e., the dorsal hypaxial musculature: Butler et al. 2010; Butler et al. 2011; Zheng et al. 2012). These longitudinal striations are comparable to those observed in many ornithopods, such as Camptosaurus, Dryosaurus, Macrogryphosaurus, Tenontosaurus, Thescelosaurus and a set of dorsal vertebrae recovered in Cretaceous outcrops of the Bajo Barreal Formation (Cenomanian-Turonian; UNPSJB-PV 960 see Ibiricu et al. 2010). Ventrally, the centra of Notohypsilophodon bear a midline keel as in the cervical vertebrae; however, this structure is not as sharp or as well defined as in the cervicals. A similar ventral keel is also seen in Changchunsaurus, Hypsilophodon, Trinisaura and Yueosaurus, whereas non-hadrosaurid iguanodontians (e.g., Cumnoria, Iguanodon, Mantellisaurus, Tenontosaurus, Zalmoxes and UNPSJB-PV 960) have centrum ventral surfaces that lack keels and which are more concave and rounded. The posterior surfaces of the centra are suboval in outline, a feature present in basal neornithischians (e.g., Hexinlusaurus and Yandusaurus) and basal iguanodontians (e.g., Camptosaurus, Iguanodon and Mantellisaurus). The transverse processes preserved in Notohypsilophodon project laterally, at approximately the same level as the zygapophyses, as is characteristic of basal ornithopods (Norman 2004; Makovicky et al. 2011). The preserved dorsal neural spine appears to be relatively low and anteroposteriorly narrow. This feature is comparable to the anatomy of basal ornithopods and differs from that seen in the more derived members of the group (i.e., nonhadrosaurid iguanodontians), where the dorsal neural spines are elevated and rectangular in shape (Norman et al. 2004). Sacral vertebrae. Due to the disarticulated nature of the sacral vertebrae, it is difficult to determine with confidence the positions of two of the sacral vertebrae recovered. Nevertheless, the sacral vertebra possessing a posterior articular surface that is laterally wider than its anterior counterpart is considered the dorsosacral (Fig. 4, also see Butler et al. 2011). Unfortunately, it is not possible to determine the full sacral number (including the sacrodorsal vertebra) due to the absence of complete articulation. However, based on the preserved elements, we considered a putative number of five or six, as also known in many other ornithischians (e.g., Dryosaurus, Gasparinisaura, Haya, Hexinlusaurus, Hypsilophodon: also see Galton 1974 a). On the other hand, with the exception of Oryctodromeus (Varricchio et al., 2007), some derived ornithopods, such as rhabdodontids (e.g., Zalmoxes and probably Mochlodon; see ��si et al. 2012) and derived iguanodontians, possess more than six sacral vertebrae. Of the two sets of sacral vertebrae recovered with Notohypsilophodon, three vertebrae, probably representing the anterior ones, are co-ossified (Fig. 4 A���C���E), whereas the other set, of two sacral vertebrae, are articulated but not co-ossified (Fig. 4 B���D���F). The sacral rib preserved (which is considered to be the first true sacral rib) is robust. The centra are slightly laterally compressed and are cotton-reel-shaped in ventral view. Circumscribing the articular surfaces, well-developed longitudinal striations are present. These striations continue onto the ventral surfaces of the centra, where they become more pronounced. The preserved sacral neural spine is wider anteroposteriorly than transversely. The distal end of the neural spine is posteriorly extended. In ventral view, the centra are comparable to those in Gasparinisaura, in possessing slightly concave ventral surfaces, whereas in many other basal ornithopods a longitudinal keel or ridge is present (e.g., Changchunsaurus and Haya). Caudal vertebrae. The caudal vertebral centra (Fig. 5) are slightly amphicoelous, as in Gideonmantellia and UNPSJB-PV 960, and they are significantly longer anteroposteriorly than wide transversely. Additionally, comparisons with well-preserved caudal sequences (e.g., Hypsilophodon, Tenontosaurus) demonstrate that these caudal vertebrae were located in the anterior portion of the tail. Notohypsilophodon possesses subrectangular intercentral articular surfaces, a feature shared with Tenontosaurus and UNPSJB-Pv 960. There are relatively welldeveloped longitudinal striations toward each lateral and ventral margin. This feature may be related to the insertion of soft tissue (e.g., the caudofemoralis musculature). Ventrally, the caudal centra of Notohypsilophon exhibit a marked longitudinal groove and well-developed facets for the insertion of the haemal arches. These last two features are also seen in several basal ornithopods and basal non-hadrosaurid iguanodontians (e.g., Gasparinisaura, Hypsilophodon, Macrogryphosaurus, Zalmoxes, UNPSJB-Pv 960 and, although less developed, in the basal ornithopod Jeholosaurus). The presence of the marked longitudinal groove could be related to either ontogenetic status (Han et al. 2012) or sexual dimorphism (Nopcsa 1929; Ibiricu et al. 2010). No ossified tendons are preserved in Notohypsilophodon, which may be related to preservation rather than genuine absence. Scapula. The left scapula of Notohypsilophodon (Fig. 6 A���B; Table 1) preserves the proximal end and a portion of shaft, which is transversally narrow as in Gasparinisaura. The scapula and coracoids are unfused as in the majority of small ornithischians (Han et al. 2012), and unlike Koreanosaurus and Oryctodromeus. The proximal end is expanded as in basal ornithopods (e.g., Gasparinisaura, Hypsilophodon) and basal iguanodontians (e.g., Dryosaurus, Tenontosaurus). The acromial process is not complete; therefore, it cannot be determined if it process was well developed, as in Anabisetia, or only moderately developed, as in Gasparinisaura (Coria & Calvo 2002). In dorsal view, the scapula of Notohypsilophodon exhibits two asymmetrical surfaces, the glenoid fossa and the coracoid articulation. The former is concave, whereas the latter is gently convex. The glenoid fossa is subrectangular in outline. Likewise, dorsally to this fossa, a marked concavity (= supraglenoid fossa; Zheng et al. 2012) is also present. This last feature is shared with various ornithischians including: Hexinlusaurus, Hypsilophodon, Lesothosaurus (Thulborn 1972), Thescelosaurus, Tenontosaurus, Uteodon, and Yueosaurus. However, the supraglenoid fossa in Notohypsilophodon is more pronounced than in all of these taxa with the exception of Tenontosaurus, whose fossa is similar to that seen in Notohypsilophodon (Martinez 1998). Element Measurement Humerus Total length 127.3 Ulna Total length 91.3 Femur (proximal end) Maximun anteroposterior width 44.9 Maximun lateral width 47.7 Femur (distal end) Maximun anteroposterior width 45.5 Tibia Total length 211.5 Greatest proximal width 56.5 Greatest distal width 45.5 Fibula Total length 192 Greatest proximal width 29.6 Greatest distal width 14.1 Phalanx (?- 1) Total length 36.1 Coracoids. The semicircular shape of the right coracoid (Fig. 6 C), with a slightly convex lateral surface and medially concave surface, is comparable to that of Gasparinisaura, Hypsilophodon and Yandusaurus. Conversely, in Changchunsaurus, Jeholosaurus and Koreanosaurus, the coracoids are sub-rectangular in shape with flat surfaces. In Trinisaura, the coracoid is semicircular in outline, as in Notohypsilophodon; however, in the former the dorsal margin is interrupted by a marked concavity (see Coria et al. 2013: fig. 3). The sternal process, in Notohypsilophodon is not as well-developed as those of Anabisetia, Gasparinisaura, Haya, Koreanosaurus, Tenontosaurus or Trinisaura. Although, it is taphonomically affected on its lateral size, in Notohypsilophodon the sternal process is markedly more reduced than in those ornithopods (see below). The coracoid foramen is circular in outline, proportionately large and completely enclosed. The coracoid foramen in Notohypsilophodon is placed well above the scapula-coracoid suture (i.e., there is no contact between the foramen and scapula). The shape and position of the coracoid foramen is similar to those of Anabisetia, Gasparinisaura, Trinisaura and Tenontosaurus (see Winkler et al. 1997: fig. 16 a), and unlike that observed in Hypsilophodon. In the latter taxon, the foramen is positioned close to the suture and connected to the scapula by a groove (Galton 1974 a; Huh et al. 2010). In more basal forms (e.g., Changchunsaurus, Koreanosaurus), the foramen is smaller than in Notohypsilophodon and located more towards the center of the coracoid plate. Humerus. The right humerus (Fig. 7 A���C; Table 1) of Notohypsilophodon is gracile (1.5 cm, measurement of the shaft taken in anterior view below the deltopectoral crest) as in Anabisetia, Gasparinisaura, Talenkauen and Trinisaura, whereas in the rhabdodontid Zalmoxes (approximately 3 cm, measurement taken from Weishampel et al. 2003: fig. 20 d) and the basal iguanodontian Tenontosaurus, the humerus is robust (Norman et al. 2004). The shaft is slightly twisted, as is characteristic of a variety of basal ornithopods (Norman et al. 2004). Nevertheless, the rotation of the humeral shaft appears to be less than in Hypsilophodon (Galton 1974 a: figs. 38���39) and resembles the condition of Anabisetia. In anterior view, the shaft is bowed as in Yandusaurus and unlike those of Anabisetia and Trinisaura where the bowing is less marked. The deltopectoral crest is reduced (i.e., to shallow rugosities for the pectoral muscle insertions) and is positioned in the proximal portion of the humerus as in Anabisetia, Bugenasaura (Norman et al. 2004), Gasparinisaura, Talenkauen and Trinisaura. By contrast, the deltopectoral crests of basal neornithischians and ornithopods (e.g., Haya, Hypsilophodon, Jeholosaurus, Koreanosaurus, Yandusaurus, among others) are well developed and angular in outline. Likewise, the deltopectoral crest in basal (non-hadrosaurid) iguanodontians is robust and it occupies approximately 50 % of total humerus length (Norman et al. 2004). The proximal end of the humeral head is transversally expanded as in Anabisetia and Gasparinisaura, and exhibits a marked tuberosity, similar to that described in Dryosaurus (Mart��nez 1998). Thus, the proximal end is wider than the distal end as in Anabisetia and Trinisaura. Conversely, in Hypsilophodon, Yandusaurus and basal iguanodontians (e.g., Tenontosaurus), the proximal and distal ends of the humerus are approximately equal in mediolateral width. The distal end of the humerus exhibits moderately developed radial and ulnar condyles, as well as an intercondylar groove (=fossa) on its anterior surface. This condition differs from that seen in Hypsilophodon, Thescelosaurus and non-hadrosaurid iguanodontians (e.g., Camptosaurus, Iguanodon, Mantellisaurus) where the condyles and the groove are more strongly developed. The lateral radial condyle is expanded anteroposteriorly and the medial ulnar condyle is rounded, both of which are features that Notohypsilophodon shares with basal neornithischians and ornithopods such as Yandusaurus and Koreanosaurus. Ulna. The ulna (Fig. 7 D���E���F; Table 1) of Notohypsilophodon is slender, as in Hypsilophodon, in contrast to the more robust ulnae of non-hadrosaurid iguanodontians. In proximal view, the ulna is triangular in outline (formed by the head of the ulna and the lateral and medial processes according to Butler et al. 2011) with the lateral border convex, the medial slightly concave and the articular surface for the radius gently concave. The olecranon process is redu, Published as part of Ibiricu, Lucio M., Mart��nez, Rub��n D., Luna, Marcelo & Casal, Gabriel A., 2014, A reappraisal of Notohypshilophodon comodorensis (Ornithischia: Ornithopoda) from the Late Cretaceous of Patagonia, Argentina, pp. 401-422 in Zootaxa 3786 (4) on pages 402-414, DOI: 10.11646/zootaxa.3786.4.1, http://zenodo.org/record/226293, {"references":["Martinez, R. D. (1998) Notohypsilophodon comodorensis gen. et sp. nov. Un Hypsilophodontidae (Ornithischia: Ornithopoda) del Cretacico Superior de Chubut, Patagonia central, Argentina. Acta Geologica Leopoldensia, 21, 119 - 135.","Martinez, R. D. & Novas, F. E. 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Aeolosaurus colhuehuapensis es un titanosaurio procedente del lago Colhué Huapi, en el Sur de Chubut, Argentina. Los materiales estudiados incluyen veintiuna vértebras caudales y siete hemapófisis, y se hallaron articulados en facies correspondientes a depósitos de desbordamientos vinculados a sistemas fluviales multicanalizados y de alta sinuosidad presentes en los aquí denominados ?estratos del lago Colhué Huapi? de edad Campaniano-Maastrichtiano. Estos sistemas poseían importantes fluctuaciones estacionales en la paleodescarga y estaban enmarcados en un clima semi-árido. La historia tafonómica fue inferida a partir del análisis de diversas características presentes en los restos y de observaciones sedimentológicas macro y microscópicas. La presencia tenue de estriamiento longitudinal, la escasa exfoliación, el grado de articulación y el arqueamiento dorsal de la serie caudal, sugieren un corto tiempo de exposición subaérea y rápido sepultamiento. La falta de marcas de abrasión en los elementos conservados indica escaso o nulo transporte, por lo que los mismos podrían ser considerados autóctonos. El curvamiento dorsal de la cola muestra un arqueamiento opistótono, también presente en algunos terópodos y saurópodos, pero aun no documentado en el Grupo Chubut. Las condiciones climáticas actuales, con variaciones de extrema humedad y sequía, afectaron marcadamente los elementos fósiles preservados. El presente trabajo constituye el primer caso de estudio tafonómico en detalle de un dinosaurio preservado en facies de planicie de inundación proximal para el Grupo Chubut. Finalmente, el hallazgo de saurópodos en estas facies es relevante, dado que este tipo de subambiente posee una alta tasa de aporte sedimentario y reducido a nulo retrabajo de los restos óseos, favoreciendo la preservación de elementos esqueletales articulados. Esto es de suma importancia para el análisis taxonómico y filogenético del clado de los titanosaurios, donde la mayoría de los taxones están representados por restos desarticulados y aislados. Palabras clave: Tafonomía, Postura opistótona, Titanosauria, Patagonia. Fil: Casal, Gabriel A.. Universidad Nacional de la Patagonia "san Juan Bosco"; Argentina Fil: Ibiricu, Lucio Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; Argentina Fil: Allard, Jose Oscar. Universidad Nacional de la Patagonia "san Juan Bosco"; Argentina Fil: Martínez, Rubén D.. Universidad Nacional de la Patagonia "san Juan Bosco"; Argentina Fil: Luna, Marcelo. Universidad Nacional de la Patagonia "san Juan Bosco"; Argentina Fil: Gonzalez Riga, Bernardo Javier. Universidad Nacional de Cuyo; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Científico Tecnológico Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina

The Bajo Barreal Formation (Cenomanian, Late Cretaceous; central Patagonia, Argentina) preserves an important and rich fossil record. Among the dinosaurs described, a small ornithischian, Notohypsilophon comodorensis, was named in the 1990s. This small-bodied dinosaur, the most complete representative of the group discovered in that formation, was described as a ?hypsilophodontid? ornithopod based on close morphological affinities with other members of that group, which is currently regarded as paraphyletic. Within this context, we present a restudy of Notohypsilophodon. This dinosaur is considered a basal ornithopod, probably more basal than Gasparinisaura. Likewise, this analysis emends and provides additional unique anatomical characters that support its taxonomic validity and position. On the basis of weak evidence, Notohypsilophodon might share the presence of gastroliths with other basal ornithopods (Gasparinisaura and Haya), which could suggest a specific behavior in response to its food ingestion. Finally, this study increases our knowledge of the evolutionary dynamics of South American Cretaceous ornithopods, and therefore broadens our knowledge of the early Late Cretaceous continental vertebrate assemblages of central Patagonia and of the Southern Hemisphere in general. Fil: Ibiricu, Lucio Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; Argentina Fil: Martínez, Rubén D.. Universidad Nacional de la Patagonia. Sede Esquel; Argentina Fil: Luna, Marcelo. Universidad Nacional de la Patagonia. Sede Esquel; Argentina Fil: Casal, Gabriel A.. Universidad Nacional de la Patagonia. Sede Esquel; Argentina

Se describe nuevos materiales y se re-describen materiales previamente publicados del Miembro Inferior de la Formación Bajo Barreal (Cenomaniano-Turoniano), en la Cuenca del Golfo San Jorge (Grupo Chubut). Los materiales fueron hallados en afloramientos expuestos en las proximidades de las estancias Ocho Hermanos y Los Sauces-Laguna Palacios en la Patagonia central, Argentina. Estos materiales corresponden a un conjunto de dos vértebras dorsales, las cuales fueron encontradas asociadas en los afloramientos arriba mencionados. Los mismos se asignan a Titanosauria en base a sus rasgos morfológicos, como representantes basales para el grupo. La determinación de los mismos reviste importancia ya que amplía el registro de titanosaurios a nivel global, para el Cretácico Superior, y a nivel local para la Formación Bajo Barreal, de titanosaurios noepachthosaurines. We report a new material and re- described material from the Lower Member of the Bajo Barreal Formation (Cenomanian-Turonian), in the Golfo San Jorge Basin (Chubut Group). The materials were recovered in outcrops exposed in the proximity of Ocho Hermanos and Los Sauces-Laguna Palacios ranches, in central Patagonia, Argentina. The materials correspond to a set of two dorsal vertebrae which was found associated in the above mentioned outcrops. We interpret these materials as belonging to Titanosauria and based on morphological features, as basal representatives for the group. The description of these materials is significant in that it adds to the generally sparse global record of Cretaceous (especially Late Cretaceous) titanosaurids. Furthermore, the materials enhance the fossil record of titanosaurian non-pachthosaurines in the Bajo Barreal Formation. Descrevem-se novos materiais e se re-descrevem materiais do Membro Inferior da Formação Bajo Barreal (Cenomaniano-Turoniano), da Bacia do Golfo San Jorge (Grupo Chubut). Os materiais foram achados de afloramentos expostos nas proximidades das Estâncias Ocho Hermanos e Los Sauces-Laguna Palacios na Patagônia central, Argentina. Os materiais correspondem a um conjunto de duas vértebras dorsais, as quais foram encontradas associadas nos afloramentos acima mencionados. Os mesmos são interpretados como pertencentes à Titanosauria e baseados em suas características morfológicas, como representantes basais para o grupo. A determinação dos mesmos é importante já que aportam ao registro global cretáceo de titanossaurios (especialmente ao Cretáceo Superior). Assim mesmo, os materiais aumentam o registro fóssil de titanossaurios nao-epachthosaurineos para a Formação Bajo Barreal. Nous signalons du matériel inédit et redécrivons du matériel provenant du Membre Inférieur de la Formation Bajo Barreal (Cénomanien-Turonien) du Bassin du Golfe de San Jorge (Groupe Chubut). Ces éléments proviennent d’affleurements situés à proximité des ranchs Ocho Hermanos et Los Sauces-Laguna Palacios en Patagonie centrale (Argentine). Ils comprennent un jeu de deux vertèbres dorsales retrouvées associées dans les affleurements sus-mentionnés. Nous interprétons ces éléments comme appartenant aux Titanosauria et, sur la base de caractères morphologiques, comme à des représentants de la base de ce groupe. La description de ces éléments est intéressante en ce qu’elle complète le registre global, généralement clairsemé, des titanosauridés crétacés (en particulier du Crétacé supérieur). De plus, ces éléments enrichissent le répertoire fossile des titanosaures non-pachthosaurines de la Formation Bajo Barreal. Fil: Ibiricu, Lucio Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; Argentina Fil: Casal, Gabriel. Universidad Nacional de la Patagonia "San Juan Bosco". Facultad de Ciencias Naturales - Sede Comodoro; Argentina Fil: Martínez, Rubén D.. Universidad Nacional de la Patagonia "San Juan Bosco". Facultad de Ciencias Naturales - Sede Comodoro; Argentina Fil: Navarrete Granzotto, César Rodrigo. Universidad Nacional de la Patagonia "San Juan Bosco". Facultad de Ciencias Naturales - Sede Comodoro; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina