Anfiteatro De Research Articles

Fourier Transform Infrared Spectroscopy Studies of Cretaceous Gymnosperms from the Santa Cruz Province, Patagonia, Argentina

Premise of research. In this contribution, the spectroscopic characterization of gymnosperm fossil remains belonging to Pteridospermophyta, Cycadophyta, Ginkgophyta, and Coniferophyta collected from the Anfiteatro de Ticó and Punta del Barco Formations (Baqueró Group; Aptian) and Springhill (Hauterivian-Barremian) and Piedra Clavada/Kachaike (Albian) Formations, outcropping in the Santa Cruz Province, Argentina, is presented. From these lithostratigraphic units, specimens of several fossil taxa showing the existence of a diverse plant assemblage during the Lower Cretaceous in Patagonia were selected.Methodology. The fossils consist of foliar compressions with very well-preserved cuticles, which are chemically characterized by Fourier transform infrared spectroscopy. Foliar remains are analyzed in two sample forms: (1) compressions (Cps; including coalified mesophyll and cuticles) and (2) cuticles (Cts). Additionally, semiquantitative data are evaluated through principal component analysis, revealing the functional groups preserved at the mesophyll and cuticle levels for all analyzed fossil taxa.Pivotal results. In general, the species from the Baqueró Group show similar chemical compositions between the Cp and Ct sample forms, whereas the chemistry of the foliar compressions from the Springhill and Piedra Clavada/Kachaike Formations reveals the presence of a high contribution of aromatic structures making up the cuticles.Conclusions. The compressions of Pseudoctenis ornata, Ginkgoites tigrensis, and Squamastrobus tigrensis probably underwent, during and after diagenesis, a natural oxidation process most likely caused by the recurrent volcanic activity that occurred during the Aptian sedimentation of the Baqueró Group. In contrast, Ruflorinia orlandoi, Ptilophyllum micropapillosum, and Ginkgoites skottsbergii have cuticles presumably composed of highly aromatic structures (such as phenylpropanoids and aromatic domains) in cutins and cutans as well due to the presence of other phenolic compounds. A new term, vitrinitic compression, is proposed here for G. skottsbergii, while P. ornata, G. tigrensis, S. tigrensis, P. micropapillosum, and R. orlandoi are called liptinitic compressions.

Reconstrucción virtual del anfiteatro de Tarragona a través de la procesión inaugural

<p>This paper is focused on a three-dimensional (3D) reconstruction of Tarragona’s amphitheatre. The intention is to improve the current museography of the monument, which poorly performs its main purpose: cultural heritage dissemination. Firstly, most of the grandstands and the main entrance are the results of a partial restoration carried out during the 1960s, based more on pragmatic rather than scientific criteria, and with many historical inaccuracies. Secondly, the worship complex, consisting of a sanctuary on the arena and another one down of, goes unnoticed by most visitors. Finally, the only area where the grandstands remain, and the only one where someone can understand the vaulted construction technique, it is not available for public entrance.</p><p>Facing this situation, the present reconstruction proposal provides people with a useful tool to comprehend the Roman building, especially where the remains are poorly preserved or inaccurately restored. In this regard, a set of rendered images has been created and, by such means, people can compare the reconstruction of the Roman building with its current remains. For this purpose, scientific methods have been employed, as well as 3D modelling technologies. First and foremost, all publications relating to Tarraco’s amphitheater have been thoroughly reviewed. Then, the archaeological remains have been redrawn using CAD tools. Henceforth, the plans and sections have been reconstructed, 3D modelled and rendered.</p><p>While the reconstruction was being developed, Roman ludic processions were found to be an interesting topic that could serve as a common thread. This way, the sectors to be reconstructed were sequenced as follows. First, the eastern entrance or Porta Triumphalis, which led the entourage to the arena. Second, the upper sacellum, where the priests conducted the liturgies to inaugurate the games. Third, the southern area, through which the gladiators and the authorities left the arena to their positions (for the first group, the service's rooms located in the underground, while for the second one, the authorities stand). Last but not least, the sanctuary under the arena, where the gladiators could perform their last prayers before the combat began.</p><p>Along with the text below, images of the reconstruction can be found next to photographs of the state of preservation, following the aforementioned sequence. Therefore, Figures 2, 3 and 4 explain the image and functioning of the main entrance (Porta Triumphalis): while Figures 2 and 4 show virtual restorations from the inside and the outside, Figure 3 presents the development of the corridor in section and plan. Figures 6 and 7 display how the upper sanctuary had looked like from the arena and once inside respectively. Figures 9 and 10 are a 2D restoration of the southern area, where its role as a hub can be understood. Figure 11 shows the southern sector from the outside, where the double entrance can be appreciated, as well as the outside stairs used by the authorities to climb to the first level and one of the multiple configurations that the façade could have taken. Figure 12 reproduces the authorities stand as the Roman spectators would have seen it. Finally, Figures 13 and 14 are images of the lower sacellum, as seen by the gladiators down the arena and in axonometry together with the upper sanctuary.</p><p>In summary, this work aims to improve the museography of Tarragona’s amphitheatre. An immediate application would be including the images in the signposting. Furthermore, they can be used as a basis to undertake a bigger project to adapt the whole museography to be better understood by society.</p><p>Highlights:</p><ul><li><p>Reconstrucción del anfiteatro de Tarragona presentada a través de un catálogo de imágenes realizadas mediante software de tratamiento 3D.</p></li><li><p>Propuesta para la divulgación del patrimonio arqueológico a través de una reconstrucción virtual didáctica e históricamente rigurosa.</p></li><li><p>Interpretación de los restos arqueológicos del anfiteatro de Tarraco desde una nueva óptica: las ceremonias de inauguración de los juegos.</p></li></ul>

Palynological, megafloral and mesofossil record from the Bajo Grande area (Anfiteatro de Ticó Formation, Baqueró Group, Upper Aptian), Patagonia, Argentina

The late Aptian flora of Baqueró is one of the best known and accurately dated Cretaceous plant associations from Gondwana, recognized for their well-preserved fossil remains. The Cerro Bayo (Bajo Grande area, Argentinean Patagonia) is one of its classical locations and includes the northernmost fossiliferous outcrops of the Baqueró Group, which belong to the Anfiteatro de Ticó Formation. It yields diverse and numerous plant megafossils and reproductive structures with associated pollen. We report a complete systematic study of a palynological association with 124 species, including 26 that are identified for the first time in the unit. This allowed the first record of three major botanical groups not reported before (i.e., lycophytes, hornworts and angiosperms), as well as algae and fungal spores. The same fossiliferous levels also yielded megafloral remains and the first record of a mesofossils assemblage for the Baqueró flora. By integrating all these floristic data sources, relative abundance analyses, and sedimentological data it is possible to propose a paleoenvironmental reconstruction of the Bajo Grande area during the late Aptian: a diverse forest growing in a temperate to warm climate with subtle variations between those associations from floodplains with water instability within a delta and those that grew into a more stable area out of the flooding influence. Thus, the presumed xeromorphic features identified in the Cerro Bayo flora (sunken stomata, papillae, epicuticular waxes) may have been related to contemporaneous volcanic activity recorded in Patagonia rather than to dry conditions.

Palynology of the Baqueró Group (upper Aptian), Patagonia Argentina: An integrated study

A palynological study on samples obtained from the Anfiteatro de Ticó and Punta del Barco formations (Baqueró Group, Macizo del Deseado area, Santa Cruz Province) is carried out. A total of 162 taxa are identified in this work, including the recognition of 59 not previously reported in the unit. Furthermore, 9 new species are proposed: Coptospora santacrucensis sp. nov., Crybelosporites corrugatus sp. nov., Cycadopites grossus sp. nov., Cyclusphaera annularis sp. nov., Cyclusphaera punnulosa sp. nov., Densoisporites patagonicus sp. nov., Peromonolites globosum sp. nov., Retitriletes ornatus sp. nov. and Taurocusporites inaequalis sp. nov. Continental algae, recovered from the Anfiteatro de Ticó Formation, are illustrated for the first time. Comparisons with other Lower Cretaceous palynological zones from regions located at similar paleolatitudes (e.g. Australia, India) and from the Potomac Group (USA) are carried out. Finally, changes in the floral composition across the Baqueró deposits are analyzed considering a context of progressive increase of volcanic activity that most certainly had some effect in the dynamics of the floristic community.

Eobowenia gen. nov. from the Early Cretaceous of Patagonia: indication for an early divergence of Bowenia?

BackgroundEven if they are considered the quintessential “living fossils”, the fossil record of the extant genera of the Cycadales is quite poor, and only extends as far back as the Cenozoic. This lack of data represents a huge hindrance for the reconstruction of the recent history of this important group. Among extant genera, Bowenia (or cuticles resembling those of extant Bowenia) has been recorded in sediments from the Late Cretaceous and the Eocene of Australia, but its phylogenetic placement and the inference from molecular dating still imply a long ghost lineage for this genus.ResultsWe re-examine the fossil foliage Almargemia incrassata from the Lower Cretaceous Anfiteatro de Ticó Formation in Patagonia, Argentina, in the light of a comparative cuticular analysis of extant Zamiaceae. We identify important differences with the other member of the genus, viz. A. dentata, and bring to light some interesting characters shared exclusively between A. incrassata and extant Bowenia. We interpret our results to necessitate the erection of the new genus Eobowenia to accommodate the fossil leaf earlier assigned as Almargemia incrassata. We then perfom phylogenetic analyses, including the first combined morphological and molecular analysis of the Cycadales, that indicate that the newly erected genus could be related to extant Bowenia.ConclusionEobowenia incrassata could represent an important clue for the understanding of evolution and biogeography of the extant genus Bowenia, as the presence of Eobowenia in Patagonia is yet another piece of the biogeographic puzzle that links southern South America with Australasia.

Two new angiosperm leaf morphotypes from the Anfiteatro de Ticó Formation (mid-Aptian) Santa Cruz Province, Argentina

Floodplain deposits of the Anfiteatro de Ticó Formation (Baqueró Group, Aptian), in Patagonia (Argentina), are rich in plant remains and contain some of the oldest angiosperm records of southern Gondwana. Many gymnosperm and pteridophyte species, as well as three morphotypes of medium sized angiosperm leaves, have already been described from this unit at different fossiliferous outcrops. We report two new angiosperm morphotypes from the Bajo Tigre locality. Both morphotypes (AT1 and AT2) consist of nano- to microphyllous leaves, nearly elliptic, with untoothed margins and pinnate brochidodromous venation. These leaves mostly exhibit characteristics of a high first or low second rank vein system. This combination of characters is associated with early angiosperm evolution. Morphotype AT1 is similar to one of the brochidodromous morphotypes from the La Cantera Formation (uppermost Aptian), which could be possibly conspecific. Morphotype AT2 has gross features already observed in leaf records from the younger Kachaike Formation (Albian ̶ lower Cenomanian) though they differ in lamina shape and secondary venation features. The angiosperm leaves of the Anfiteatro de Ticó Formation suggest that the early stages of angiosperm evolution in Patagonia had included forms with more than one type of growth habit.

Revised stratigraphic framework of the Cretaceous in the Bajo Grande area (Argentinean Patagonia) inferred from new U–Pb ages and palynology

The revision of the stratigraphy of the Cerro Bayo in the Bajo Grande area (Argentinean Patagonia) and the new 206Pb/238U age of 116.85 ± 0.26 Ma constrain the dating of the Baqueró flora, one of the most abundant Aptian floras of southern Gondwana. This flora, preserved in the Baqueró Group, represents an extinct biome that flourished ca. 118 Ma ago and was affected by increasing regional volcanism during the subsequent four millions years. The outcrops of the Cerro Bayo are characterized by fluvio-lacustrine deposits divided into three facies associations that include nine lithofacies. The first palynological record for the locality confirms the correlation of the lower part of the outcrops with the Anfiteatro de Ticó Formation (the oldest unit of the Baqueró Group). The new radiometric age and stratigraphy support recognition of the Bajo Tigre Formation (the middle unit of the Baqueró Group) in the area and date the earliest stage in angiosperm diversification in southern South America. Stratigraphic relationships among the Baqueró, Chubut and Divisadero groups are briefly discussed.

Late Aptian angiosperm pollen grains from Patagonia: Earliest steps in flowering plant evolution at middle latitudes in southern South America

The angiosperm pollen record from the Anfiteatro de Ticó and Punta del Barco formations (Baqueró Group) is reported. The relevance of these floras is that they are accurately dated as late Aptian, and one of the oldest floras southern South America with fossil angiosperms. Twelve samples were studied, showing Clavatipollenites and Retimonocolpites as dominant types. A new species, Jushingipollis ticoensis sp. nov., is proposed. A doubtful angiosperm pollen grain, Lethomasites sp., is also identified and described. A multivariate analysis of similarities between different Early Cretaceous angiosperm pollen assemblages suggests that the Baqueró Group assemblages have great similarities with other coeval units from Argentina, Australia and United States, which were located in a similar paleolatitude.

The Early Cretaceous megaflora of the Springhill Formation, Patagonia. Paleofloristic and Paleonvironmental inferences

The Springhill Formation (Lower Cretaceous) is considered as one of the most important oil producer units within the Austral Basin in Argentina. However, knowledge regarding this formation's plant community composition is still very scarce. In this work a thorough survey of the outcrops of the Springhill Formation was conducted regarding both geological and palaeobotanical aspects. Abundant fossil plant material was collected at the Estancia El Salitral and Río Correntoso localities in Santa Cruz Province, Argentina, consisting primarily of compressions of leafy shoots with several branching orders, completely to partially preserved fronds, simple to pinnate leaves and fertile scales. Analysis of these materials made it possible to describe 20 new taxa which add to the already known flora of the Springhill Formation; nine of these taxa were found in Estancia El Salitral, and the remaining 11 were found in Río Correntoso. The floristic diversity of the unit has increased through the discovery of the first megafossils of ginkgophytes (Baiera sp. 1 and Baiera? sp. 2), whereas new taxa have been described within the divisions of Pteridophyta, Pteridospermophyta, Cycadophyta and Pinophyta. Analysis of the vegetative and reproductive epidermal structures of the various groups included within this megaflora has been demonstrated to be a valuable tool for the recognition and differentiation of species. Analysis has also made it possible to suggest paleoenvironmental inferences. Finally, the megaflora from the Springhill Formation was compared to other relevant plant assemblages from the Lower Cretaceous of Western Gondwana. The megaflora was determined to be most similar to that of the well-known Patagonian Anfiteatro de Ticó Formation and most different from that of the Brazilian Crato Formation.

Estudios palinológicos del Grupo Baqueró (Cretácico Inferior), provincia de Santa Cruz, Argentina. X. Polen de Gymnospermae y Apéndice Final

Palynological studies from the Baqueró Group (Lower Cretaceous), Santa Cruz Province, Argentina. X. Pollen of Gymnospermae and final Appendix. In the present paper, the palynological study of Gymnosperm pollen from the Anfiteatro de Ticó Formation is completed. The material was collected in Anfiteatro de Ticó and Estancia Bajo Tigre localities from the Santa Cruz Province. The Anfiteatro de Ticó Formation, the basal unit of the Baqueró Group, has an Aptian age. The study includes 9 genera and 11 species. One new genus ( Ticoites ), and three new species ( Araucariacites spinosus , Ephedripites acutus and Ticoites gamerroi ) are described. Also, Dilwynites granulatus Harris is cited for the first time in the Lower Cretaceous of Argentina. This paper, the final contribution of the series, indicates the presence of a wide variety of gymnosperms, a group that nowadays is almost extinct in Patagonia due to large recurrent climatic changes that have occurred since the Aptian.

High-precision U–Pb zircon age from the Anfiteatro de Ticó Formation: Implications for the timing of the early angiosperm diversification in Patagonia

The Baqueró Group is one of the most relevant units regarding the study of the early diversification of angiosperms in South America. Whereas the age of the upper part of the Group, namely the Punta del Barco Formation, has been recently dated at 114.67 ± 0.18 Ma, the rest of the unit still lacks precise dating. In this contribution a CA-TIMS U–Pb zircon age of 118.23 ± 0.09 Ma for a tuff interlayered with fossiliferous rocks of the Anfiteatro de Ticó Formation (lower part of the Baqueró Group) is reported. This age constrains the duration of deposition of the Baqueró Group to approximately 4 Ma and provides new evidence for the age interpretation of the previously described angiosperm flora and associated pollen assemblages from this unit, until now interpreted as early Aptian or possibly Barremian in age. The Aptian age of the Baqueró Group allows a better comparison between the paleofloras from this southernmost region.

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).

Leaf Cuticle Anatomy and the Ultrastructure ofGinkgoites ticoensisArchang. from the Aptian of Patagonia

The leaf cuticle of the Ginkgoites ticoensis Archang. type material from the Aptian Anfiteatro de Tico Formation in Patagonia, Argentina, is fully characterized with additional scanning and transmission electron microscopic observations. Many new anatomical and ultrastructural cuticular features are identified in the four-lobed leaf of G. ticoensis: the leaf shows a hypostomatic and papillate laminae, straight and pitted anticlinal and granulate periclinal walls, actinocytic stomata with between five and seven papillate, striate subsidiary cells, and guard cells with anticlinal smooth walls. The TEM studies on ordinary epidermal cells, papillae, subsidiary cells, and guard cells reveal general ultrastructural features of Ginkgoaceae: an outer polylamellate layer A made with A1 and a granular inner layer A2; A1 with an upper part A1U with continuous and straight translucent lamellae; a lower part A1L with significantly disrupted and waving translucent lamellae; and the fibrillar cuticular layer B1 as the i...

Consideraciones Sistemáticas y Bioestratigráficas Acerca de Thoatheriopsis Mendocensis Soria, 2001 (Litopterna, Proterotheriidae)

Abstract. SYSTEMATIC AND BIOSTRATIGRAPHIC CONSIDERATIONS ON THOATHERIOPSIS MENDOCENSIS SORIA, 2001 (LITOPTERNA, PROTEROTHERIIDAE). The revision of the Family Proterotheriidae has led to the study of the specimen MLP 81-XI-28-1 of Thoatheriopsis mendocensis Soria, found in the so-called Anfiteatro de Cacheuta (Mendoza Province, Argentina). We expanded the diagnosis, incorporating dental characters that were not considered previously. Its origin is uncertain, but it could correspond to the finding mentioned by Rolleri in an unpublished report, in the “Marino beds”, without totally discarding the possibility of being Minoprio the collector of the fossil. We conclude that the specimen MLP 81-XI-28-1 comes from the Marino Formation, though it cannot be established whether it comes from the Areniscas Entrecruzadas Member or the Estratos de Marino Member, both outcropping at Anfiteatro de Cacheuta. It constitutes in any case a new faunal element of this formation and adds to the mammals found at the Areniscas En...

Morfología y Anatomía de un Helecho Creciendo Bajo Condiciones de Estrés en el Aptiano de Santa Cruz, Argentina

MORPHOLOGY AND ANATOMY OF A FERN GROWING UNDER STRESS CONDITIONS FROM THE APTIAN OF SANTA CRUZ, ARGENTINA. The morphology and anatomy of pteridophyte fronds attached to rhizomes with adventitious roots from the Aptian Anfiteatro de Ticó Formation, Santa Cruz province, Argentina are described. The fossils consist of impressions and compressions preserved in lithofacies dominated mainly by volcanic ash-fall. Observations made with scanning electron microscope on rhizomes and rachides revealed the presence of primary xylem tissues; protoxylem, metaxylem fibers and parenchyma. According to the general morphology, this fern is included in the morphogenus Cladophlebis Brongniart. Comparisons made with known Cladophlebis species of Argentina show that the material here studied has different morphological features. Furthermore, rachides in organic connection to rhizomes having a well preserved anatomy was not reported for Cladophlebis species from Argentina. Therefore, a new name, Cladophlebis cinerium, is assigned to this fern. Finally, it is suggested that this fern probably grew under humid conditions given by the fluvio-lacustrine environment of the Anfiteatro de Ticó Formation, but also with continuous stress caused by the abundant ash fall produced by the recurrent explosive andean vulcanism that took place during the Lower Cretaceous in Patagonia.

An Early Cretaceous zamiaceous cycad of South West Gondwana: Restrepophyllum nov. gen. from Patagonia, Argentina

The record of Cycadales in Patagonia begins in the Triassic and extends up to the Oligocene. In this region the group is highly diversified and includes several taxa represented by trunks, leaves and pollen cones. A new cycadalean genus and species, Restrepophyllum chiguoides, form the Aptian Anfiteatro de Ticó Formation, Santa Cruz province, Argentina, is described here. The fossil is a leaf compression with well-preserved cuticle. Its morphology, anatomy and ultrastructure are studied by means of light and electron microscopy. The leaf is lanceolate, serrate, and possesses a prominent midvein and decurrent laterals showing an open, simple or dichotomous venation. The leaf is hypostomatic, and the abaxial cuticle is thinner than the adaxial one. The stomata are irregularly distributed and indistinctly oriented between veins. They are monocyclic to imperfectly dicyclic (haplocheilic); the suprastomatal aperture is raised over the epidermis and the guard cells are sunken. Scattered trichomes and crystalliferous idioblasts are also present. The cuticle is composed of three layers: the outer and inner layers are lamellate, while the middle one is granulate. This new cycad leaf is compared with similar fossil leaves from Gondwana and Europe/North America, and also with similar extant cycad leaves. Based on the general morphology and the main characters of the cuticle, R. chiguoides is assigned to the family Zamiaceae; moreover it is more closely related to the living Zamia ( Chigua) restrepoi (D. Stevenson) Lindstrom than to any other member of the Cycadales. Paleophytogeographic evidence suggests a South American origin of Zamia/Chigua and a further migration to northern latitudes. This new type of leaf also suggests the putative existence of a Chigua clade that may be traced back to the Early Cretaceous when two cycadalean families, Zamiaceae and Stangeriaceae, were already well-established in Patagonia.

Fossil Record of the Rubiaceae

Fossils of 134 taxa attributed to the Rubiaceae are described or mentioned in 115 publications dating from 1850 and from deposits as old as the Cretaceous and Paleocene. Close scrutiny of these records indicates, however, that the oldest and most likely (accepted) representatives of the family are four genera, Emmenopterys Oliv. from the Middle Eocene of Oregon and Washington, U.S.A., Faramea Aubl. from the Late Eocene of Panama, and Guettarda L. (cf. as †Guettardidites; †= fossil taxon) and Canthium Lam. (as †Rubipollis oblatus) from the Late Eocene of Australia, and a probable fifth genus, the alternate-leaved †Paleorubiaceophyllum eocenicum from the Middle Eocene of Tennessee/Kentucky, U.S.A. The record represents three subfamilies (Rubioideae, Ixoroideae, Cinchonoideae) from three widely separated geographic regions, implying an earlier origin in the Late Cretaceous or Paleocene. From the Oligocene, there are six accepted genera, Coprosma J. R. Forst. & G. Forst., Coprosma–Opercularia, Faramea Aubl., Macrosphyra Hook. f. (as †Triporotetradites hoekeni), Mitragyna Korth. (as †Retitricolporites annulatus), and Pinckneya Michx. from Africa (Cameroon), Australia and New Zealand, U.S.A. (Oregon), and Puerto Rico. The period of greatest diversification and radiation was in the Miocene, with 20 accepted genera reported from North America, Central America, South America, Southeast Pacific–Asia, Africa, and Europe. Stages in the evolution of three characters are further suggested by the fossil record. The relatively uncommon occurrence of alternate leaves among modern taxa is typical of advanced genera (e.g., Didymochlamys Hook. f., Sabicea Aubl., Theligonum L.), but this feature may have already developed by the Middle Eocene (†Paleorubiaceophyllum). Polyploidy is suggested in the Middle Eocene P. eocenicum var. lawrensis by epidermal cells 32 µm in diameter or nearly twice the size of the other varieties. Pollen polymorphism, possibly coordinated with or as a prelude to heterostyly, is represented by the diporate pollen of Faramea in the Late Eocene, and triporate and tetraporate forms in the Miocene and Pliocene. Currently, the principal needs are: (1) to clarify pending Paleocene records of †Cinchonidium (Cinchona L.), North Dakota, U.S.A.; Galium L., Greenland; and †Psilatricolpites coprosmoides (Coprosma, Chile); and (2) to examine the several large Cretaceous megafossil floras now under study (e.g., Anfiteatro de Ticó, Argentina; Crato, Brazil; Turonian-age floras, New Jersey and Sweden) for specimens with features that suggest a rubiaceous complex or with an aggregation of features suggesting presence of the family.

Cretaceous pCO 2 estimation from stomatal frequency analysis of gymnosperm leaves of Patagonia, Argentina

Stomatal frequency of fossil conifers and ginkgoals cuticles were considered as potential indicators of the pCO 2 values in the Patagonian palaeoatmosphere during the Cretaceous. Samples are from continental deposits of early Upper Aptian age (Anfiteatro de Ticó and Punta del Barco formations) and Upper Albian–Lower Cenomanian age (Kachaike Formation), both outcropping in Andean and extra-Andean portions of Santa Cruz province, Argentina. It can be inferred that the CO 2 atmospheric content was similar during both stages, or was slightly higher toward the Late Albian–Early Cenomanian. The CO 2 content estimated from the conifers is between ~ 700 and 1400 ppmv (or lower from the mid-Aptian ginkgoals). This CO 2 range is consistent with those predicted worldwide by previous studies (stomatal indices, biogeochemical models and carbon isotopes), and implies a CO 2 content 2.3–4.0 times higher than present. The high atmospheric CO 2 content during the Middle Aptian and Late Albian–Early Cenomanian was probably linked to a warming process at high latitudes during these times. This is consistent with the floristic development recorded during both stages in Patagonia.

Early Cretaceous riparian vegetation in Patagonia, Argentina

Early Cretaceous riparian vegetation in Patagonia, Argentina. An autochthonous plant as-semblage found at the Bajo Grande locality, Anfiteatro de Ticó Formation, Baqueró Group, Early Aptian of Santa Cruz province, Argentina, is described. Sedimentological data show an alternation of sandstone and lime-stone, with recurrent fossil levels associated to a fluvial system. The frequent flood in areas close to the levee had an influence on the vegetation growing along the banks of the channels. A plant assemblage composed of Ricciopsis grandensis nov. sp. (bryophyte), Adiantopteris tripinnata nov. sp., Schizaeaceae pinnules (ferns), and the gnetalean fructification Ephedra verticillata nov. sp. was found in this paleoenvironment. The taphonomical studies suggest that the plant assemblage was autochthonous, and it grew and was buried in an area near a levee. This result is congruent with environmental data provided by living representative of the fossil taxa analyzed.

Estudios cuticulares de Ginkgoites Seward del Cretácico Inferior de Patagonia

Cuticular studies of Ginkgoites Seward from the Lower Cretaceous of Patagonia. The anatomy and ultrastructure of the leaf cuticles of Ginkgoites ticoensis Archang. and G. skottsbergii Lund. is studied. Both taxa were collected in Santa Cruz province, G. ticoensis from the Anfiteatro de Tico Formation (Aptian) and G. skottsbergii from the Kachaike Formation (Albian). The cuticular studies were made by means of electronic microscopy (SEM, TEM). These observations showed that G. ticoensis has hypostomatic leaves, papillae on both cuticles, and monocyclic stomata with 5-7 papillate subsidiary cells; while G. skottsbergii presents amphistomatic leaves, and monocyclic to dicyclic stomata with 6-8 subsidiary cells partially papillate. At the ultrastructural level the cuticular membrane has three layers, which are clearly distinct in both species. Comparisons with the leaf cuticle of other ginkgoalean taxa are also made.