Ana Archangelsky

Cuticular characters adapted to volcanic stress in a new Cretaceous cycad leaf from Patagonia, Argentina. Considerations on the stratigraphy and depositional history of the Baqueró Formation

Abstract The cuticle of a new cycad, Pseudoctenis ornata Archangelsky et al., sp. nov. is described and discussed in relation to the physical paleoenvironment in which the plant lived. The specimens occur in the Early Cretaceous Baquero Formation, near Estancia El Verano in the Santa Cruz Province, Argentina. A detailed stratigraphic section records four facies, namely (1) fluvial channel, (2) flood plain, (3) lacustrine, and (4) flat and extended plains. A detail of each facies is provided. Pseudoctenis cuticles are found in the flood plain facies; the other components of the plant association are Gleichenites, Araucaria and Taeniopteris . The depositional history of this succession is related to a braided river that periodically received volcanic ash. Plants grew until complete burial by ash. Leaves of Pseudoctenis are pinnate, hypostomatic, with polycyclic stomata that form ill-defined rows. Abundant papillae and hair bases are present, especially on the lower cuticle. Comparisons are made with other Pseudoctenis species found in the same formation, and in other regions of the world. It is suggested that the paleoenvironment had a strong influence on the vegetation, especially the ash fall, and that it may have played a role in the formation of xeromorphic structures that characterize several gymnosperms present in this stratigraphic unit, including Pseudoctenis ornata . The lack of burning features on the cuticle suggests a cold ash fall. This fall probably was responsible for changes in edaphic patterns and atmospheric conditions that governed the growth and distribution of plant communities during the deposition of the Baquero Formation.

Aptian Angiosperm Pollen from the Ticó Flora Patagonia, Argentina

Six angiosperm pollen types studied with SEM are recorded in the Cretaceous (early Aptian) Ticó flora on the basis of material recovered from two localities: Anfiteatro de Ticó and Bajo Tigre. Clavatipollenites dominates, with four types described. The other two types, based on single specimens, were referred to Retimonocolpites and to the Anacostia type. Comparisons are made with similar species found in other Cretaceous paleofloristic regions and with other Aptian pollen assemblages from Patagonia. The chloranthaceous affinity of Clavatipollenites agrees with known paleobotanical, sedimentological, and paleoclimatical data obtained for the same fossiliferous horizons of the Anfiteatro de Ticó Formation studied here. During the early Aptian, a warm and humid paleoclimatic belt extended to latitudes greater than 60°S in SW Gondwana. This belt is known to have persisted until the late Aptian in southern Patagonia. The angiosperm pollen variety is further underscored by fossil leaves found in two of the horizons studied here, suggesting that angiosperms may have existed during the Barremian in SW Gondwana (Patagonian Province).

Taxonomic and stratigraphic revision of Lower Cretaceous cicatricose spores from Patagonia: 2. Genera Cicatricosisporites Potonié & Gelletich and Ruffordiaspora Dettmann & Clifford

Taxonomic and stratigraphic revision of Lower Cretaceous cicatricose spores from Patagonia. 2. Genera Cicatricosisporites Potonie & Gelletich and Ruffordiaspora Dettmann & Clifford. Nine species of the genus Cicatricosisporites and five species of the genus Ruffordiaspora were found in several surface and subsurface sections of Lower Cretaceous sediments from the Austral Basin, Patagonia, Argentina. Two new species: Cicatricosisporites pramparoana and Ruffordiaspora cardielensis, are described, while 5 species: Cicatricosisporites cf. C. hallei, C. minutaestriatus, C. venustus, Ruffordiaspora cf. R. crassiterminatus nov. comb. and R. ludbrookiae are mentioned for the first time in Argentina. In view of the similarities that may be found between some species, and in order to facilitate comparisons and determinations, the main characters for each taxon here considered are resumed in a table. It is concluded that during the Lower Cretaceous spores of the family Anemiaceae were frequent components of pollen assemblages from the Austral Basin. Three groups of species studied are recognized: 1) species that are present in all stages of the Lower Cretaceous (Cicatricosisporites annulatus, C. cuneiformis, C. hughesii, C. sp. 2, Ruffordiaspora australiensis, R. ludbrookiae and R. ticoensis), 2) species that are found only in Aptian and Albian deposits (Cicatricosisporites cf. C. hallei, C. pramparoana and Ruffordiaspora cardielensis), and 3) species present excusively in albian sediments (Cicatricosisporites venustus, C. minutaestriatus and Ruffordiaspora cf. R. crassiterminatus).

Revisión taxonómica y estratigráfica de esporas cicatricosas del Cretácico Inferior de Patagonia: 1. Géneros Appendicisporites Weyland & Krieger, Nodosisporites Deák y Plicatella Maljavkina

Taxonomic and stratigraphic revision of Lower Cretaceous cicatricose spores from Patagonia. 2. Genera Cicatricosisporites Potonié & Gelletich and Ruffordiaspora Dettmann & Clifford. Nine species of the genus Cicatricosisporites and five species of the genus Ruffordiaspora were found in several surface and subsurface sections of Lower Cretaceous sediments from the Austral Basin, Patagonia, Argentina. Two new species: Cicatricosisporites pramparoana and Ruffordiaspora cardielensis, are described, while 5 species: Cicatricosisporites cf. C. hallei, C. minutaestriatus, C. venustus, Ruffordiaspora cf. R. crassiterminatus nov. comb. and R. ludbrookiae are mentioned for the first time in Argentina. In view of the similarities that may be found between some species, and in order to facilitate comparisons and determinations, the main characters for each taxon here considered are resumed in a table. It is concluded that during the Lower Cretaceous spores of the family Anemiaceae were frequent components of pollen assemblages from the Austral Basin. Three groups of species studied are recognized: 1) species that are present in all stages of the Lower Cretaceous (Cicatricosisporites annulatus, C. cuneiformis, C. hughesii, C. sp. 2, Ruffordiaspora australiensis, R. ludbrookiae and R. ticoensis), 2) species that are found only in Aptian and Albian deposits (Cicatricosisporites cf. C. hallei, C. pramparoana and Ruffordiaspora cardielensis), and 3) species present excusively in albian sediments (Cicatricosisporites venustus, C. minutaestriatus and Ruffordiaspora cf. R. crassiterminatus).

Juan Carlos Gamerro (1923–2013)

Juan Carlos Gamerro, pionero de la Palinología en nuestro país, falleció el 20 de marzo en su residencia de San Isidro, Provincia de Buenos Aires. Las Ciencias Naturales han perdido así una de sus figuras más destacadas. Educador e investigador incansable, humilde y bondadoso, deja como herencia discípulos, colegas y amigos que fueron beneficiados por su saber en los diferentes sitios donde trabajó. J.C. Gamerro desarrolló sus estudios en la Universidad de La Plata donde obtuvo el título de Licenciado en Botánica en el año 1952. Entre 1949 y 1958 trabajó en la Dirección de Agricultura de la Provincia de Buenos Aires y desde 1957 a 1966 fue docente en la Universidad de Buenos Aires. En 1966, y hasta 1979, pasó a desarrollar su actividad académica en la Universidad Nacional de La Plata. En ese lapso publicó importantes trabajos de investigación. En 1976 J.C. Gamerro ingresó a la Carrera del Investigador del CONICET desarrollando sus actividades en el Centro de Investigaciones en Recursos Geológicos (CIRGEO) hasta 1983. A partir de esa fecha y hasta su jubilación en el año 1997, se desempeñó como Sub-Director del Instituto de Botánica Darwinion (IBODA). Fue jurado de Tesis y Concursos en las Universidades Nacionales del Sur, de La Plata, Universidad de Buenos Aires y en la Universidad Federal de Rio Grande do Sul (Brasil). Dictó seminarios, conferencias y cursos en las universidades de Buenos Aires y Federal de Rio Grande do Sul. A lo largo de su carrera participó en diversos Congresos nacionales e internacionales. Dirigió becarios, tesistas e investigadores y participó de campañas paleontológicas. Fue miembro de Comisiones Asesoras del CONICET (años 1992-1993). Fue Vocal (1965-1979), Vice-Presidente (1976-1977) de la Asociación Paleontológica Argentina, y Director de AMEGHINIANA (1967-1982). En 1973 fue miembro fundador de la Asociación Latinoamericana de Paleobotánica y Palinología y desde 1983 hasta 1997 fue Co-Director de la revista Darwiniana. Ha publicado cerca de 50 trabajos originales de investigación y difusión, como único autor o en colaboración, abarcando temas de botánica y fundamentalmente de palinología fósil y actual. Revistas extranjeras difundieron sus investigaciones: Svenska Botanica Tidskrift, en colaboración con Gunnar Erdmann (1951), Review of Palaeobotany and Palynology, Revista Española de Micropaleontología, Botanical Journal of the Linnean Society y Annals of the Missouri Botanical Gardens. En el país publicó principalmente en Ameghiniana y Darwiniana. Sus trabajos han contribuido a que tanto Neontólogos, cuanto Geólogos y Paleontólogos tomáramos seriamente el concepto de variabilidad biológica, lo que produjo un mejoramiento sustancial en la creación y revisión de taxones actuales y fósiles. J.C. Gamerro siempre priorizó en sus investigaciones los detalles técnicos en la preparación del material polínico y la puesta a punto del instrumental óptico o electrónico para obtener excelentes documentos fotográficos que se reproducen en sus trabajos. Analizaba minuciosamente los granos de polen y esporas cuidando que todos los caracteres morfológicos tuviesen una documentación visual adecuada. A ello sumaba siempre una exhaustiva búsqueda bibliográfica antes de concluir su tarea. Por su labor científica, J.C. Gamerro fue laureado por la Academia Nacional de Ciencias con el premio “Cristóbal Hicken, bienio 1967–1968”. La Asociación Paleon-

Pilunsporites un nuevo género de espora cretácica de Patagonia

Pilunsporites, a new genus of a cretaceous spore from Patagonia. The new early cretaceous genus Pilunsporites is established for trilete spores found exclusively in a restricted area of the Austral Basin in the Patagonian offshore. The spores have a robust equatorial cingulum that thickens at the three angles to form a solid auriculate hemisphaeric structure. The proximal ornament consists of triangular muri or solid pads that bear sporadical verrucae. The distal ornament is verrucate, rugulate or has few anastomosed muri. A perisporium layer is often present. The three species described, Pilunsporites muratus n. sp., P. rugulatus n. sp and P. verrucatus n. sp., partly share characters with putative pteridaceous spores, and most likely are related to this fern family. The restricted geographic and stratigraphic range of Pilunsporites underscores its endemic nature and further supports the large variety that ferns attained in Patagonia during the Early Cretaceous.