1,721,081 research outputs found
South American Sauropodomorphs: What Their Bone Histology Has Revealed to Us
No full textGiven that bone microstructure is a very important source of paleobiological information, several paleohistological studies have been conducted on sauropodomorph dinosaurs, possibly making this clade the most studied histologically. Despite these paleohistological studies on sauropodomorph dinosaurs from South America are relatively scarce in comparison with other regions of the world, significant progress on this matter (i.e. paleohistology of South American sauropodomorphs) has been made during the last decade. Following an order from rather specific to more generalized issues, the most important advances are related to the origin of particular skeletal elements (i.e. osteoderms, sacral supraspinous ossifications and extremely elongated cervical ribs), the growth patterns of basal sauropodomorphs and the variation on sauropod growth dynamics and its relationship with gigantism. Regarding the origin of osteoderms and extremely elongated cervical ribs, these structures have been formed by metaplastic ossification of dermal and tendinous tissues, respectively. Their histological characterization has been helpful to discover that the alleged osteoderms of Agustinia ligabuei were actually dorsal and cervical ribs. The long bone histology of basal sauropodomorphs has revealed that the cyclical growth pattern assumed for this group actually showed some degree of variation. Finally, a clade of basal sauropods (i.e. lessemsaurids) was characterized by a cyclical growth pattern, not previously reported for other sauropods, combined with episodes of highly accelerated growth rates. The gigantic body sizes obtained by lessemsaurids were therefore reached through a growth strategy different from that developed by eusauropods (i.e. rapid and continuous growth).Fil: Cerda, Ignacio Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigación en Paleobiología y Geología; Argentin
Caudal pneumaticity in derived titanosaurs (Dinosauria: Sauropoda)
No full textAmong extant vertebrates, only birds have a respiratory system associated with pneumatic diverticula. However, several extinct clades also had pneumatic diverticula, including the sauropod dinosaurs. Among sauropods, Saltasaurini are characterized by extreme postcranial pneumaticity, which extends as far down the spinal column as the posterior caudal vertebrae. In this paper the pneumatic foramina in both the neural arches and the centra are described in detail, and the relative proportion of air spaces in the caudal vertebrae is established, revealing that the skeleton of Rocasaurus muniozi was more pneumatized than that of Neuquensaurus australis, with Saltasaurus loricatus intermediate. The level of pneumatization varies between the three saltasaurine taxa: in Neuquensaurus, only the neural arch is pneumatized, whereas in the other two saltasaurines both neural arches and centra are pneumatized. This allows us to hypothesize that the timing of pneumatization varied between the three species, with Rocasaurus muniozi pneumatized earliest in ontogeny. This ontogenetic pattern is correlated with evolutionary derivation: the most derived taxa show pneumatization in both the neural arch and the centrum.Fil: Zurriaguz, Virginia Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigación en Paleobiología y Geología; Argentina. Universidad Nacional de Río Negro. Sede Alto Valle; ArgentinaFil: Cerda, Ignacio Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigación en Paleobiología y Geología; Argentina. Universidad Nacional de Río Negro. Sede Alto Valle; Argentin
Plasticidad fenotípica del crecimiento en el sauropodomorfo basal Mussaurus patagonicus Bonaparte y Vince 1979: Evidencia paleohistológica
Full text linkSi bien la dinámica de crecimiento de los dinosaurios sauropodomorfos ha sido extensivamente estudiada durante los últimos años, la mayor cantidad de contribuciones se han enfocado en formas derivadas (i.e., Neosauropoda). Con el objeto de incrementar el conocimiento en cuanto a la dinámica de crecimiento de formas basales de Sauropodomorpha, se realizó un estudio paleohistológico de Mussaurus patagonicus. Se analizaron trece elementos, incluyendo húmeros, fémures y fíbulas, de seis individuos (MPM-PV-1813/10, MPM-PV-1851, MPM-PV-1815, MLP-61-III-20-22, MLP-68-II-27-1, MLP- 61-III-20-23) procedentes de la Formación Laguna Colorada (Jurásico Temprano, Santa cruz, Argentina). Considerando lalongitud del fémur, el rango de tamaño de la muestra oscila entre los 12 y 80 cm. Si bien el patrón de variación histológica durante la ontogenia es similar al reportado en otros dinosaurios no avianos (i.e., formación temprana de tejido fibrolamelar altamente vascularizado, el cual progresivamente cambia a pseudolamelar menos vascularizado), no existe una clara correlación entre el tamaño y el estadio ontogenético. Asimismo, la distribución de marcas de crecimiento revela importantes variaciones en cuanto a la dinámica de crecimiento (continua durante la primer parte de la ontogenia y volviéndosecíclica tardíamente en algunos individuos y cíclica durante toda la ontogenia en otros). La falta de correlación entre estadio ontogenético y tamaño ha sido reportada en otros sauropodomorfos basales (Plateosaurus), siendo vinculada a un importante grado de plasticidad fenotípica durante el crecimiento. Dicha plasticidad podría también explicar la variación en a la dinámica de crecimiento de Mussaurus, la cual no ha sido reportada en otros sauropodomorfos.Fil: Cerda, Ignacio Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigación en Paleobiología y Geología; ArgentinaFil: Pol, Diego. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Museo Paleontológico Egidio Feruglio; ArgentinaXXXIII Jornadas Argentinas de Paleontología de VertebradosCórdobaArgentinaAsociación Paleontológica Argentin
The first record of a soft-shelled turtle (Testudines: Pan-Trionychidae) from southern Balkans (Pliocene, Gefira, N. Greece) and new information from bone histology
Full text linkSoft-shelled turtles (Pan-Trionychidae) are not included in the present-day chelonian fauna of Greece and have been unknown in the Greek fossil record up to now. Here we report the first fossil occurrence of a soft?shelled turtle from Greece, originating from the Pliocene Gefira Member (Angelochori Formation), in the lower Axios valley. The corresponding specimens were discovered with several mammalian remains, most of them attributable to the mastodon of Auvergne, Anancus arvernensis. The chelonian material includes five carapacial fragments that belong to the same individual and can be attributed to Pan-Trionychidae based on the typical sculpturing on the dorsal side of the carapace. Most of these bony plates were histologically sampled and thereby provide evidence for the ?plywood? structure, another characteristic of pan-trionychids. They represent the first extended sampling of trionychid plates that belong to the same individual, allowing the documentation of the variation of the relevant trionychid morphologies in the carapace. These findings expand the paleobiogeographic range of this taxon to the southern Balkans and Greece and allow a better estimation of the chelonian paleo-fauna of the area. They are also important for the temporal distribution of this clade in the Paleoarctic, as they join specimens from Italy as being the last trionychids in Europe.Fil: Vlachos, Evangelos. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Museo Paleontológico Egidio Feruglio; ArgentinaFil: Cerda, Ignacio Alejandro. Universidad Nacional de Río Negro. Sede Alto Valle. Instituto de Investigaciones en Paleobiología y Geología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Tsoukala, Evangelia. Aristotle University of Thessaloniki; Greci
Histología de osteodermos de archosaurioformes no Avemetatarsianos: nuevas inferencias paleobiológicas
No full textLa presencia de osteodermos es un rasgo compartido por numerosos grupos de Archosauriformes (principalmente dentro de Pseudosuchia y formas no arcosaurianas), cuyo estudio micronanatómico e histológico se ha incrementado en los ultimos años. En esta contribución se presentan los principales avances en los distintos taxones estudiados, incluyendo Doswelliidae, Proterochampsidae, Revueltosaurus Hunt, 1989, Aetosauria, Erpetosuchidae y ?Rauisuchia?, como así también las futuras líneas de investigación surgidas de los mismos. En lo que se refiere al modo de origen de los osteodermos, se ha establecido que el mismo se basa mayormente en una osificación de tipo intramembranosa. Existe entre y dentro de los distintos clados una enorme variación en cuanto a su grado de compactación. En este sentido, a diferencia de otros tipos de elementos óseos (e.g. huesos apendiculares), no parece existir una relación directa entre el grado de compactación de los osteodermos y su hábito de vida (e.g. terrestre, acuático). Todos los grupos estudiados de archosauriformes no avemetatarsianos exhiben marcas de crecimiento (i.e. líneas de crecimiento detenido y annuli) en su tejido primario, lo cual permite efectuar estimaciones de edad relativa. Esto último ha sido empleado en Aetosauria para reconstruir curvas de crecimiento. Los resultados indican una tasa de crecimiento relativamente más baja en comparación a los peudosuquios vivientes (cocodrilos) y una maduración sexual relativamente temprana. Los próximos estudios a encarar en esta temática tienen como objeto ampliar el muestreo a grupos no estudiados (e.g. Ornithosuchidae) e incorporar datos histológicos de otras partes del postcraneo.Fil: Cerda, Ignacio Alejandro. Universidad Nacional de Río Negro. Sede Alto Valle. Instituto de Investigaciones en Paleobiología y Geología; Argentina. Museo Provincial “Carlos Ameghino”; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; ArgentinaFil: Desojo, Julia Brenda. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Paleontología Vertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaReunión de Comunicaciones de la Asociación Paleontológica ArgentinaSan LuisArgentinaUniversidad Nacional de San Luis; Asociación Paleontológica Argentin
Dentition and histology in titanosaurian dinosaur embryos from Upper Cretaceous of Patagonia, Argentina
Full text linkExceptionally preserved sauropod embryos from the Late Cretaceous Anacleto Formation in Auca Mahuevo (Neuquén Province, Argentina), have provided fundamental information on titanosaurian ontogeny. This paper describes the dental composition and disposition as well as bone microstructure of the specimens. Embryonic teeth show size disparity, with lengths that vary from 1 to 3 mm, and diameters ranging from 0.15 to 0.26 mm, the most frequent length values between 2.5 and 3 mm. Seemingly, a typical “pencil–like” teeth morphology, and a dental formula Pm 4, M 7-8 / D10? remained constant during titanosaurian ontogeny, whereas their arrangement in the skull shows notable ontogenetic changes. Absence of wear facet on teeth would indicate absence of pre–natal chewing movements. The enamel proportion is significantly higher in embryos than in mature titanosaurs, which suggests that this relation varies during ontogeny. Embryonic bony tissue is composed by a highly vascularized and cellular woven bone. Absence of osteonal tissue, high degree of vascularization, presence of numerous osteocytes and low development of periosteal bone reveal that the Auca Mahuevo titanosaurs would have had a high early growth rate, and they were not entombed in an advanced embryonic stage.Fil: García, Rodolfo Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Cerda, Ignacio Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentin
Paleohistology of two dicraeosaurid dinosaurs (Sauropoda; Diplodocoidea) from La Amarga Formation (Barremian–Aptian, Lower Cretaceous), Neuquén Basin, Argentina: Paleobiological implications
No full textDespite the large number of paleohistological studies carried out on sauropodomorph dinosaurs, some particular groups, such as dicraeosaurids, have been little explored. The current knowledge about the osteological microanatomy of this family is limited to that from specimens of Dicraeosaurus spp. and the holotype specimen of Suuwassea emiliae. We have examined the bone microstructure of the femur, humerus, and dorsal rib of the holotype of Amargasaurus cazaui and the femur of the holotype of Amargatitanis macni. The main purpose of this study is to obtain information regarding the ontogenetic stages of these individuals and, in a more general sense, to increase our understanding about the growth dynamics of dicraeosaurid sauropods. We interpret that Amargatitanis represents a more maturational stage than Amargasaurus, due to its high degree of bone remodeling and to the greatest number of lines of arrested growth (LAGs). Sexual maturity, mainly evidenced by the relative abundance of LAGs in the outer cortex of stylopodial bones, appears to have been reached by both individuals prior to death. Nevertheless, only Amargatitanis shows somatic maturation, evidenced by the presence of an External Fundamental System (EFS). In Amargasaurus, the dorsal rib preserved more LAGs than the long bones, supporting previous hypotheses that the dorsal ribs are good elements for making age estimates.Fil: Windholz, Guillermo Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigación en Paleobiología y Geología; ArgentinaFil: Cerda, Ignacio Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigación en Paleobiología y Geología; Argentina. Museo Carlos Ameghino; Argentin
Osteohistology of Aucasaurus garridoi (Dinosauria, Theropoda, Abelisauridae): inferences on lifestyle and growth strategy
No full textAlthough osteohistology has proven to be useful to discern several palaeobiological traits and systematics in non-avian dinosaurs, the bone microstructure of several groups (e.g., abelisaurid theropods) is still poorly documented. Here, we provide a microstructural description of different bones (a cervical epipophysis, three dorsal ribs, three grastralia, and the left femur) of the type specimen of the abelisaurid Aucasaurus garridoi, its ontogenetic stage and compare its growth with other theropods, especially abelisauroid taxa. The cortical bone is mostly composed by fibrolamellar bone tissue composed of a woven-fibred matrix. Secondary remodelling varies among the different elements. The compacta of the rib shows eleven growth marks (with an additional seven in the external fundamental system), implying that the specimen was at least eleven years old and had reached somatic maturity when it died. The presence of lines of arrested growth/annuli supports a cyclical growth strategy, as in Niebla, Quilmesaurus, and Abelisauridae indet. MMCh-PV 69. All these abelisaurids indicate that the maturity based on cyclical growth marks spacing is not reliable, due to considerable variability of this parameter within a single element. This study represents the first intensive osteohistological investigation for an Abelisauridae member, providing new information on palaeobiological traits of this clade.Fil: Baiano, Mattia Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Confluencia; Argentina. Provincia del Neuquén. Municipalidad de Villa El Chocón. Museo Paleontológico "Ernesto Bachmann"; Argentina. Universidad Nacional de Río Negro; ArgentinaFil: Cerda, Ignacio Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigación en Paleobiología y Geología; Argentina. Museo Provincial Carlos Ameghino; Argentin
Bone microstructure of the sphenodont rhynchocephalian Priosphenodon avelasi and its paleobiological implications
No full textSphenodontians are a group of vertebrates with a vast taxonomic diversity and worldwide distribution of their fossils. Although they have been the subject of many studies on their phylogeny and morphology, those focused on their paleobiology are still scarce. We present here the osteohistology of eleven postcranial elements corresponding to a single specimen of Priosphenodon avelasi, an eilenodontine sphenodontian from Cenomanian–Turonian rocks of Río Negro (Argentina). The bone samples described here share a parallel-fibered type of matrix. The degree of vascularization varies in all the samples, but none of them present a significant density of primary vascular canals. Lines of arrested growth were observed in all appendicular elements, being better preserved in the humerus, radius and fibula. Extrinsic fibers were observed only in reduced regions of the cortex of the ulna and in one of the phalanges. The primary bone tissue suggests that the specimen had a relatively low growth rate with alternation between slow and accelerated stages. The latter could explain why this taxon reached the largest sizes of all known sphenodontians.Fil: Cavasín, Sol Aldana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigación en Paleobiología y Geología; ArgentinaFil: Cerda, Ignacio Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigación en Paleobiología y Geología; ArgentinaFil: Apesteguía, Sebastián. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Fundación de Historia Natural Félix de Azara; Argentin
Palaeobiological inferences of the aetosaur Aetosauroides scagliai (Archosauria: Pseudosuchia) based on microstructural analyses of its appendicular bones
No full textAetosaurs were a group of armoured pseudosuchians, recorded in most of the Upper Triassic continental deposits worldwide. Several osteohistological contributions of aetosaurs focused on their osteoderms, but rarely on appendicular bones. Here, we analyse the microstructure of the humerus, femur and tibia of Aetosauroides scagliai (specimens PVL 2073 [holotype] and PVL 2052). These exhibit cortical bone formed by highly vascularised fibrolamellar bone present in the inner portion of the cortex, mixed with scarce parallel-fibred bone. Also, they show parallel-fibred bone in the outermost portion of the cortex. A general growth pattern that includes a first rapid stage followed by a slow stage is reported. Nevertheless, the growth rate and the presence of parallel-fibred bone embedded in fibrolamellar bone layers recognise more variation within Aetosauria. The value of appendicular bones and osteoderms as age estimators is variable, the first being useful in early stages, and in late stages the osteoderms are better (based on the particular growth of osteoderms). Through morphological (neurocentral sutures) and histological (EFS absent) information, the holotype (PVL 2073) was recovered between juvenile and subadult stages. Using a statistical model that combines microanatomical and morphological data, a terrestrial lifestyle is inferred for Aetosauroides, which concur with previous analyses.Fil: Ponce, Denis Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigación en Paleobiología y Geología; ArgentinaFil: Desojo, Julia Brenda. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; ArgentinaFil: Cerda, Ignacio Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigación en Paleobiología y Geología; Argentin
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