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Fil: Genise, Jorge Fernando. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina

Fossil bee cells, attributable to the ichnospecies Palmiraichnus castellanosi, are recorded from the Pleistocene and Holocene of the easternmost Canary Islands. Cells bear a chamber with internal smooth lining, spiral closure, and an antechamber. They have a discrete wall that surrounds both the chamber and antechamber. The antechamber shows an internal smooth surface and a structureless filling of palaeosol material. These features enable this material to be assigned to the ichnospecies P. castellanosi, originally described from the Palaeogene of Uruguay. This record constitutes the first documented evidence for bees, and Hymenoptera, in the Quaternary of the Canaries and the first for this ichnospecies from Africa. By comparison with extant cells, the potential constructors are bees of the genus Andrena (Andrenidae). Palaeoecological and statistical data suggest that five species may have produced P. castellanosi in the Canary Islands. One on Lanzarote in the Holocene, another in south Fuerteventura in the Upper Pleistocene, two on Gran Canaria and another on Montan&tild;a Clara islet during the Middle Pleistocene. A high level of breeding success was probably favoured by the lack of predators or parasites and optimal environmental conditions, at least in the Pleistocene. During the Pleistocene, the abundance of P. castellanosi in the lowlands suggests a rich endemic shrubby flora and palaeoclimatic conditions similar to the present, but probably with a higher humidity. The land-snail assemblage associated with low densities of P. castellanosi in the Holocene mid-altitude belt suggests a cool moist palaeoenvironment, less favourable for P. castellanosi producers. Fil: La Roche, Francisco. Universidad de La Laguna; España Fil: Genise, Jorge Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; Argentina Fil: Castillo, Carolina. Universidad de La Laguna; España Fil: Quesada, María Luisa. Universidad de La Laguna; España Fil: García Gotera, Cristo M.. Universidad de La Laguna; España Fil: De la Nuez, Julio. Universidad de La Laguna; España

The known ichnospecies of Coprinisphaera have been usually linked to dung beetles of coprophagous habits living in grass-dominated environments inhabited by large herbivorous, which provide the dung for constructing brood balls. A new ichnospecies consisting of bispherical and thin-walled structures, Coprinisphaera akatanka, is separated from the pear-shaped and thick-walled structures that remains in C. tonni. C. akatanka consists of an egg chamber separated from the provision chamber by a deep neck. This morphology is comparable with brood balls constructed by extant species of Canthon showing necrophagous habits. This similarity suggests that the producers of C. akatanka might also display necrophagous feeding habits. The newbispherical structures were found in Sanandresian Aridisols (Early Pleistocene) developed in loess deposits of the Pampean region. Such paleosols record stable floodplains, covered with herbaceous and shrubby vegetation, under a seasonal, semiarid temperate-cold climate during a phase of glacier expansion in Patagonia. Sanandresian Land Mammal Substage shows a sparse record of large herbivorous, potential producers of suitable pads for dung beetles; only Neuryurus sp. and Glossotherium sp. are recorded in the area. The extinction of autochtonous taxa associated to palaeoenvironmental stress conditions during the Sanandresian Substage and the absence of the allochtonous taxa involved in Great American Biotic Interchange produced a bottleneck for dung availability. Such scenario of reduced dung resources would have favored dung beetle necrophagy in the Pampean region reflected herein with C. akatanka record. Fil: Cantil, Liliana Fernanda. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales; Argentina Fil: Sánchez, María Victoria. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales; Argentina Fil: Bellosi, Eduardo Sergio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales; Argentina Fil: Gonzalez, Mirta Gladys. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales; Argentina Fil: Sarzetti, Laura Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales; Argentina Fil: Genise, Jorge Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales; Argentina

Independently, Roselli (1939) and Sauer (1955) described and named similar fossil brood balls from the Paleogene of Uruguay (Devincenzia murguiai) and from the Quaternary of Ecuador (Coprinisphaera ecuadoriensis), respective- ly. In their contributions, they illustrated and described fossil brood balls characterized by the presence of a medium-sized hole piercing the wall of spherical to sub-spherical chambers. Newly collected brood balls from palaeosols of the Cangahua Formation (Ecuador), and other previously deposited in ichnological collections from Ecuador, Uruguay, and Argentina, including type material, were revised to update Coprinisphaera ichnotaxonomy. Coprinisphaera ecuadoriensis Sauer (1955) is a subjective junior synonym of Coprinisphaera murguiai (Roselli, 1939). Coprinisphaera murguiai sensu Laza, 2006 (non Roselli, 1939) is in turn a new ichnospecies named herein Coprinisphaera lazai isp. n. Additionally, a new ichnospecies, named herein as Coprinisphaera kitu isp. n.., was found in the Cangahua Formation. It is represented by a spherical to sub-spherical chamber having a discrete wall, with a crown composed of a hemispherical structure on one pole. The statistical analysis of the size of the two ichnospecies found in the Cangahua Formation suggests that C. kitu and C. murguiai may represent two stages (closed and emerged balls, respectively) of a unique original morphology (C. kitu) and producer. There are no extant dung beetle species that construct brood balls with a morphology similar to that of C. kitu. The producer of C. kitu would be the recently described fossil Phanaeini, Phanaeus violetae. Phytoliths extracted from infillings of closed C. kitu revealed that Poaceae were mostly included in the diet of the herbivores that produced the dung. Considering the vertebate fossil record for the Pleistocene Cangahua Formation, ground sloths, mastodons, and horses could have been the dung providers. The record of Tombownichnus plenus, Lazaichnus fistulosus, and Castrichnus incolumis suggests the presence of cleptoparasites and detritivores in the dung community. Cangahua sediments accumulated in a volcaniclastic, intermontane setting located at 2500–2900 m.a.s.l. and under fluctuat- ing syneruptive conditions. Changes in facies associations and palaeosol types enable to distinguish three stages in evolution of sedimentation and landscapes. Calcic Andisols, andic Aridisols, and andic Mollisols, in the upper section, are the pedotypes that more commonly include Coprinisphaera. The intravolcanic environments where dung beetles, and probably large herbivores, better developed were temperate, seasonal, semiarid to subhumid, grasslands and wooded grasslands. They were covered by ashfalls reworked by wind and minor volcaniclastic flows. Fil: Sánchez, María Victoria. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales; Argentina Fil: Genise, Jorge Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales; Argentina Fil: Bellosi, Eduardo Sergio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales; Argentina Fil: Román Carrión, Jose Luis. Museo de Historia Natural "Gustavo Orcés V."; Ecuador Fil: Cantil, Liliana Fernanda. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales; Argentina

The ichnospecies Asthenopodichnium xylobiontum comprises U-shaped traces in wood, usually attributed to the activity of mayfly nymphs (Insecta, Ephemeroptera), which indicate the presence of freshwater palaeoenvironments. The record of a new ichnospecies in wood, Asthenopodichnium lignorum, in the Miocene of New Caledonia, strongly indicates that it may correspond to other trace makers because the potential producing Ephemeroptera are absent around these Miocene oceanic islands and in a wide area comprising New Zealand and Australia. We present herein the evidence for wood rotting fungi as potential trace maker of the new ichnospecies that has been previously recorded from Argentina, Egypt, Czech Republic, USA, and Lithuania. The new ichnospecies A. lignorum, in contrast with A. xylobiontum, is an indicator of terrestrial, humid to subhumid, palaeonvironments. Fil: Genise, Jorge Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; Argentina Fil: Garrouste, Romain. Centre National de la Recherche Scientifique; Francia. Muséum National d'Histoire Naturelle; Francia Fil: Nel, Patricia. Centre National de la Recherche Scientifique; Francia. Muséum National d'Histoire Naturelle; Francia Fil: Grandcolas, Philippe. Muséum National d'Histoire Naturelle; Francia. Centre National de la Recherche Scientifique; Francia Fil: Maurizot, Pierre. Bureau de Recherches Géologiques et Minières; Francia Fil: Cluzel, Dominique. Universidad de Nueva Caledonia; Francia Fil: Cornette, Raphaël. Muséum National d'Histoire Naturelle; Francia Fil: Fabre, Anne-Claire. Muséum National d'Histoire Naturelle; Francia. Colegio Universitario de Londres; Reino Unido. Université Paris Diderot - Paris 7; Francia Fil: Nel, André. Centre National de la Recherche Scientifique; Francia. Muséum National d'Histoire Naturelle; Francia

The possible producer and environmental setting of large meniscate burrows (Nagtuichnus meuleni igen. and isp. nov.) occurring in late Miocene and Holocene aeolian deposits from Argentina are discussed. These are unbranched burrows with an uniform meniscate filling that range in width from 46 to 78 mm. N. meuleni distinguishing features are a filling composed of a discontinuous, outer massive layer between a central meniscate core and the excavation boundary, sets of parallel ridges in the external wall, and a particular outline plus the presence of paired pits in the concave surface of menisci (or hollows in the convex surface). The late Miocene lower member of the Rio Negro Formation at La Loberia (Rio Negro province) is interpreted as aeolian dune, damp interdune and dry interdune deposits. The Holocene sediments from Gran Salitral (southwestern La Pampa province) represent aeolian dune, wet interdune and dry interdune deposits. N. meuleni occurs only in damp and dry interdune deposits. The composite ichnofabric produced by N. meuleni in the Holocene of the Gran Salitral is composed of two suites of trace fossils. A former Skolithos suite includes Skolithos linearis, Taenidium barretti, Polykladichnus aragonensis and root traces developed in lacustrine calcareous mudstone deposits (wet interdune). This suite is overprinted by N. meuleni, with subordinate participation of S. linearis and root traces, composing the Nagtuichnus suite. The later suite is developed in brown silt and sand of dry interdune areas. The Nagtuichnus ichnofabric is considered indicative of damp to dry interdune facies of late Miocene to Holocene age. The burrow systems of the likely producers of the Holocene N. meuleni structures were studied in the field and in the laboratory. The candidates were selected from the extant local fauna of the Gran Salitral, including southern cavies (Microcavia australis, Rodentia), tuco-tucos (Ctenomys azarae, Rodentia), and pink fairy armadillos or pichiciegos (Chlamyphorus truncatus, Xenarthra). The most likely producer of N. meuleni are pichiciegos because they have fully subterranean habits and insectivorous diet involving the production of long, unbranched, horizontal burrows excavated in sand, which are mostly backfilled. In contrast to this, tuco-tucos and southern cavies, which are herbivores that forage aboveground, use their more permanent burrows for dwelling and reproduction. As observed in a live, captive-kept C. truncatus, the meniscate structure of the fill can be explained by the animal packing the excavated sand with its rump plate. This mechanism also results in a massive layer of sediment in the burrow fill. Other significant bioglyphs that are a sort of fingerprint of pichiciegos are the outline of menisci in cross-section (mimicking their rump plate) and pairs of rounded pits in the concave surface of menisci (probably tail traces).

Dung beetles use the dung of herbivores, particularly large mammals, to provision their underground nests in which they construct brood balls where the egg is laid. These insects are usually linked to grass-dominated habitats (GDH) inhabited by abundant and large mammals, which, feeding on grasses, produce large amounts of the insects' food: dung. Fossil brood balls of dung beetles, included in the ichnogenus Coprinisphaera, are typical trace fossils of Southern South American Cenozoic palaeosols. This ichnogenus includes five ichnospecies, C. murguiai, C. isp. A, C. kheprii, C. tonnii, and C. kraglievichi, all of which are represented in a pyroclastic fluvial and loessic (eolian) sequence of the middle Eocene-lower Miocene Sarmiento Formation at the classic palaeontological locality of Gran Barranca (Chubut, Argentina). This locality bears a detailed litho and chronostratigraphic framework that is based on several sedimentologic and magnetostratigraphic profiles and numerous radiometric ages. These provide a high-resolution stratigraphy for tracking the changes in dung beetle faunas as reflected in their trace fossils, and accordingly, to record the evolution of GDH. Particular objectives are to analyze: 1) the first Coprinisphaera records; 2) the increase in Coprinisphaera size and its relationship to mammal size; 3) the relative sizes of ichnospecies of Coprinisphaera to infer the potential dung beetle diversity; and (4) the major changes in the evolution of GDH as reflected by dung beetle trace fossils. About 1200 specimens of Coprinisphaera belonging to the five ichnospecies and to 15 statigraphical levels were collected, sectioned, identified, and measured. The parameters statistically analyzed were: relative abundance of ichnospecies, density of specimens per m2, and equatorial diameter (ED). From this analysis it was possible to recognize several episodes in the evolution of dung beetle faunas and the associated GDH of southern South America. The first episode, by the late middle Eocene (39.8 Ma), records a favorable palaeoenvironmental change that achieved the critical point to support a GDH suitable for the appearance of the first dung beetles. This episode finishes with the total absence of dung beetle traces due to arid conditions. The second episode, by the early late Eocene (approximately 37.3 Ma), records a burst in the density, abundance, and diversity of Coprinisphaera and dung beetles favored probably by the settlement of GDH with large herbivores. This episode concluded near the Eocene–Oligocene transition, with another xeric period without Coprinisphaera records. During the early late Oligocene (approximately 26 Ma), the third episode shows similar parameters than the second one recording the return to the optimal palaeoenvironmental conditions of the second episode. The fourth episode (approximately 24.7 Ma), during the middle late Oligocene, reflects changes within a relatively stable ecosystem, recording a significant increase in Coprinisphaera size, along with the disappearance of the smallest specimens, triggered by the appearance of large to huge herbivores. During the Oligocene–Miocene transition, the fifth episode (24.2–20.4 Ma) records stability in palaeoenvironmental conditions, suggested by similar parameters to those of the previous episode. During the middle early Miocene (approximately 19.8 Ma), the sixth episode records unfavorable environmental changes for dung beetles and GDH at Gran Barranca. This episode records the first evidence of a deterioration of the dung beetle fauna. From the latest early Miocene onward (19.3–18.7 Ma), there is no more evidence of Coprinisphaera, suggesting unfavorable environmental conditions that led to the disappearance of dung beetles from the area of the Gran Barranca.

This study includes three aspects: 1) the ichnotaxonomic treatment of large and dominantly vertical burrows ornamented with sharp bioglyphs from the fluvial Neogene Vinchina and Toro Negro formations (northwest Argentina); 2) the description and interpretation of the sedimentary facies where these burrows occur; and 3) neoichnologic observations on large ornamented burrows from seasonal wetlands of the Rio Pilcomayo National Park (Argentina) as possible modern analogues of the trace fossils and the sedimentary environment. A new ichnogenus and ichnospecies, Capayanichnus vinchinensis, is proposed to include the large striated burrows. The new ichnotaxon is distinguished by a combination of a predominantly vertical orientation, overall “L” shape (when fully developed), absence of lining and burrow bifurcation, a distinct surface texture, and lack of burrow enlargements. The hosting sedimentary facies of the Vinchina Formation can be grouped into fluvial channel and splay (floodplain) facies associations. The rivers of that unit were of two main types: single channel rivers with frequent channel avulsion and overbank flow and multichannelised rivers with poorly defined margins. At least some of these rivers were ephemeral or with intermittent discharge. The climate was probably seasonal and semiarid, as suggested by sedimentologic evidence. C. vinchinensis was dominantly recorded from the top of fluvial channels (interpreted as abandoned channels) and proximal, intermediate and distal splay facies. The large ornamented burrows found in an extant comparable example were constructed by freshwater crabs. These burrows can be distinguished by the overall architecture, the taxonomy and sex of its occupants, and the environmental setting where they were found. The neoichnologic signatures used in the interpretation of the fossil example include the common oval burrow cross-section and the surface texture. In particular, the surface texture in the modern crab burrows includes abundant comma-shaped marks, sets of grooves oblique to burrow axis, and long segmented grooves. The predominantly oval cross-section, absence of lining, and the strongly ornamented burrow surface suggest that C. vinchinensis was produced by freshwater crabs. The key features of the surface ornament are long sets of three–four ridges whose width is in average one third of the burrow major axis. Other features that also point to a crab origin are a massive filling, common burrow ends in a casing mudstone, chevron pattern in sets of surface ridges, and possible cheliped marks. The new ichnotaxon is restricted, in the Vinchina and Toro Negro formations, to fluvial facies and is absent in shallow lacustrine facies.

The analysis of the total number of phytoliths, and the absolute frequencies of the different morphotypes, extracted from fossil dung beetle brood balls (Coprinisphaera) from the Middle Eocene–Early Miocene Sarmiento Formation (Patagonia, Argentina), revealed that this trace fossil represents a concentrated locus for phytolith sampling. Particularly, differences found in the total number of phytoliths among parts of that trace fossil and the bearing paleosol, allowed to infer that the infilling represents mostly a sample of the original surrounding soil, whereas in most cases the wall shows a significantly higher number of phytoliths than in the paleosol or infilling. Modern brood balls also revealed that in an environment with high density of grasses, the walls, composed of soil and dung fibres, showed a lower concentration of phytoliths than the soil. In contrast, in other environment with scarce grass coverage, the dung, which had a higher concentration of phytoliths than the soil, added to the wall produced an increase in the number of phytoliths in it. Accordingly, the larger number of phytoliths of the Coprinisphaera wall in comparison with that of the paleosol, would be reflecting the addition of dung fibres to the wall in palaeoenvironments with moderate to poor presence of phytolith-bearing plants. The absence of differences in the total number of phytoliths between the internal and the external layer of the brood ball wall, suggests that the dung fibres would have been uniformly distributed in most of the wall, due to the addition of dung fibres during the brood ball construction by the dung beetle. In contrast, the absence of differences among wall and paleosol or infilling, could be suggesting that no dung fibres were added to construct the wall, that those added had no phytoliths, that the Coprinisphaera involved could had been a brood ball of a necrophagous scarab, or that the soils were richer in phytoltihs than the dung. Those balls that showed evidence of increased numbers of phytoliths in the wall, likely caused by dung fibres added to it, enable the study of diet preferences of the herbivores that produced the dung. Differences found in the phytolith morphotype frequencies among the wall, and the other two samples (infilling and paleosol), allow to infer that some herbivores were more generalists among phytolith-bearing plants feeding on the most abundant grasses and palms, whereas others preferred more rare grasses and dicots.

The breeding trace fossils described herein along with the high density of Loloichnus baqueroensis in the Cretaceous formations of Patagonia suggest that crayfishes were soil engineers along the Cretaceous in southern South America, and that they had acquired many of the K-breeding behaviours recorded by insects in latest and post-Cretaceous soils, such as pelletal constructions and excavation of breeding cells. The K-T event was probably responsible for changes in environmental conditions in such a way that crayfishes finally became restricted to two small distributional areas in southern South America, and K-breeding insects replaced them as keystone organisms in Cainozoic and modern soils. Dagnichnus titoi igen. and isp. nov. and Cellicalichnus meniscatus isp. nov., are created to include the new trace fossils attributable to crayfishes from the Cretaceous of Patagonia, Argentina. The attribution to crayfishes is based on their association and morphological affinities with the crayfish fossil burrows L. baqueroensis from the same geologic units. D. titoi is represented by hemispherical chambers surrounded by thick and short, meniscate burrows, which can be arranged in two or three tight whorls in the more regular specimens. Meniscate burrows are curved downwards and have no neck. Walls are unlined. C. meniscatus are necked, horizontal, and straight cells, showing meniscate fillings, attached to sub-vertical shafts, which are relatively much wider than the neck of cells. Both, shafts and cells show a thin and smooth lining. The presence of cells or burrows smaller than the putative parental burrows and comparisons with breeding traces of marine Decapoda support the interpretation of breeding traces, Calichnia, of terrestrial crustaceans. C. meniscatus is interpreted as cells excavated from parental burrows, whereas D. titoi are probably breeding structures completely produced in a different palaeoenvironment where the female release juveniles. Fil: Genise, Jorge Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Museo Paleontológico Egidio Feruglio; Argentina Fil: Bedatou, Emilio. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; Argentina Fil: Melchor, Ricardo Nestor. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; Argentina

The trace fossil, Loloichnus baqueroensis igen. and isp. nov., from Late Jurassic-Late Cretaceous continental deposits of Patagonia, Argentina, includes thickly lined, mostly passively-filled, and Y-branched burrows. Other important features of this ichnofossil are the inner surface texture of lining showing transversal, elongated, and adjacent grooves, and less commonly, the pelletal filling of burrows. L. baqueroensis is recorded from the Bajo Grande, Bajo Tigre, Punta del Barco, and Laguna Palacios Formations, which were deposited in different volcaniclastic environments of the Deseado Massif and San Jorge Basin geological provinces, respectively. The described burrows are found in many levels of palaeosols developed in reworked piroclastic deposits, where they are the main component of the ichnofabrics, in association with meniscate and thinly lined burrows and a diffuse and complex boxwork of small diameter burrows. Root traces are also present, and in many cases, occur inside L. baqueroensis. Considering general morphology, surface texture, filling types, palaeoenvironments in which they occur, and comparisons with extant and fossil decapod burrows, the likely trace makers of L. baqueroensis were crayfishes (Decapoda: Astacidea), probably Parastacidae. The producers of L. baqueroensis inhabited soils, where their burrows probably reached the water table, and contained roots that were used for feeding. Considering climatic preferences of extant parastacids, it is proposed a temperate climate for central Patagonia during the deposition of the studied units. The widespread presence of crayfishes during Late Jurassic-Late Cretaceous times in central Patagonia, supports the monophyletic origin of this group during the Triassic, and suggests that the present restricted geographic distribution in southern South America is a relict of a broader one. Fil: Bedatou, Emilio. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; Argentina Fil: Melchor, Ricardo Nestor. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; Argentina Fil: Bellosi, Eduardo Sergio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; Argentina Fil: Genise, Jorge Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Museo Paleontológico Egidio Feruglio; Argentina

Four new trace fossils of termites are described from the Upper Miocene and Lower Pliocene continental sandstones of the northern Chad basin. Coatonichnus globosus, ichnogenus and ichnospecies nov. is a large ellipsoidal termite calie (20?40 cm in diameter) more or less flattened at both poles. It is morphologically very similar to the nest of extant termite Hodotermes mossambicus from South Africa. It exhibits an internal shelved pattern of modern Hodotermitidae such as the superposition of flat chambers separated vertically by ramps, columns, walls, and pillars. It is interpreted as the nest of an ancestral species of Hodotermes (Hodotermitidae).The new ichnospecies Vondrichnus planoglobus is composed of dense swarms of tens of chambers connected by a net of straight galleries developed in a single plane. The chambers (5?12 cm in diameter) have a spherical shape with a planar base. Generally, short galleries connect each chamber to the straight main tunnel of meter to decameter-scale length. Vondrichnus planoglobus is interpreted as polychambered diffuse nests of fungus-growing termites (Macrotermitinae, Termitidae). Microfavichnus alveolatus, ichnogenus and ichnospecies nov. is a small-scale alveolar mass (3?8 cm by 2?4 cm). The base of the construction is flat to concave. It is entirely composed of a sub-horizontally layered, alveolar-like structure composed of a regular juxtaposition of millimetre-scale round pellets or balls (mylospheres). Microfavichnus alveolatus is interpreted as fossilized fungus combs of ?fungus-growing? termites (Macrotermitinae, Termitidae). Termitichnus schneideri, ichnospecies nov. is a large-scale extremely flattened construction (15?60 cm in diameter and 6?18 cm in height). The internal shelved pattern is composed of flat chambers separated by columns, walls, and pillars. Each level is connected by ramps. An external wall surrounds the framework constructed. One to several peripheral funnel-shaped tunnels occur sub-perpendicular to the construction. This new Termitichnus ichnospecies is interpreted as being a possible central hive of the Vondrichnus planoglobus net. Fil: Duringer, Philippe. Universite Louis Pasteur; Francia Fil: Schuster, Mathieu. Université de Poitiers; Francia Fil: Genise, Jorge Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina Fil: Mackaye, Hassan T.. Université de N'Djaména; Chad Fil: Vignaud, Patrick. Université de Poitiers; Francia Fil: Brunet, Michel. Université de Poitiers; Francia

This paper discusses the lithofacies distribution and ichnotaxonomic assignment of invertebrate, vertebrate and plant trace fossils in an Early Mesozoic ephemeral fluvio-lacustrine system from northwest Argentina. The overall palaeoenvironment is envisaged as a distal, low-gradient fluvio-lacustrine setting under semi-arid climate, similar to a terminal fan. Depositional lobes (facies association A) are composed of distributary ribbon channels (facies A1), and associated pond and sheetflood deposits (facies A2). Lowlands between depositional lobes (facies association B) contained poorly drained floodplain zones similar to wetlands (facies B1) and shallow closed lakes (facies B2). Depositional lobes were fringed by playa-lake settings (facies association C), including mudflats (facies C1) that are partially eroded by ephemeral fluvial channels (facies C2). The ichnofauna of the Santo Domingo Formation displays high ichnodiversity (30 trace fossil types) and includes 5 trace fossil assemblages that are linked to sedimentary facies. These trace fossil assemblages are highly distinctive as half of the recognised trace fossil types are assigned to different assemblages. The ephemeral fluvial channel assemblage (facies A1 and C2) displays the lower ichnodiversity (n = 6) and includes Skolithos linearis, Diplichnites sp., Palaeophycus tubularis, Taenidium barretti, Dicynodontipus sp. and footprints in cross-section. The floodplain pond assemblage (facies A2) shows the higher ichnodiversity (n = 15) and is composed of Diplichnites sp., Helminthoidichnites tenuis, P. tubularis, Rusophycus carbonarius, S. linearis, Spongeliomorpha carlsbergi, T. barretti, appendage marks, burrows with brush-like features, epichnial bilobed traces, hypichnial bilobed ridges, bird-like footprint type A, tridactyl footprints, footprints preserved in cross-section, and small epichnial rounded pits. The poorly drained floodplain assemblage (facies B1) is of moderate ichnodiversity (n = 10) and consists of H. tenuis, S. carlsbergi, ?Spongeliomorpha sp., imbricated backfilled burrow fillings, root trace type A, Tetrasauropus sp., bird-like footprint type A, large pentadactyl footprints, tridactyl footprints, and footprints preserved in cross-section. The high ichnodiversity (n = 13) nearshore lacustrine assemblage (facies B2) is the only assemblage that lacks vertebrate traces, and is composed of Cochlichnus anguineus, Cruziana problematica, H. tenuis, Palaeophycus heberti, P. striatus, P. tubularis, Scoyenia gracilis, S. carlsbergi, T. barretti, epichnial bilobed traces, hypichnial bilobed ridges, root trace type B, and scratch marks. The intermediate ichnodiversity (n = 9) mudflat assemblage (facies C1) is typified by the largest ichnodiversity of vertebrate tracks and includes H. tenuis, P. tubularis, S. carlsbergi, Dicynodontipus sp., Tetrasauropus sp., bird-like footprints of types B and C, large pentadactyl footprints, and tridactyl footprints. The trace fossil assemblages from Santo Domingo Formation are typical representatives of the Scoyenia ichnofacies. The distinctiveness of the studied trace fossil assemblages suggests that a future division of the Scoyenia ichnofacies would be possible, provided that occurrences of invertebrate, vertebrate and plant trace fossils in definite sedimentary facies are considered. The subdivision of the Scoyenia ichnofacies into recurrent groups of trace fossils (ichnosubfacies) with a palaeoecological and palaeoenvironmental meaning can be based on two approaches: distinction of associations of vertebrate tracks and recognition of ichnocoenoses related to substrates with different degrees of water saturation and firmness. The first approach can be based on an evaluation of the recurrent vertebrate ichnoceonoses used to recognise vertebrate ichnofacies. In this way, some of the candidate vertebrate ichnofacies are proposed as subdivisions of the Scoyenia ichnofacies. The second approach is based on the identification of crosscutting relationships between trace fossils and between trace fossils and sedimentary structures within some trace fossil assemblages. Using this methodology, it is possible to define distinct assemblages of trace fossils: a "pre-desiccation suite" with structures lacking ornamentation and developed in a soft substrate and a "desiccation suite" typified by striated traces that crosscut the former. These trace-fossil assemblages help to characterise the changes in organism-sediment interaction during progressive desiccation of a water-lain substrate. Additional neoichnological studies are necessary to assess the exact meaning of different trace fossil features in terms of substrate consistency. Fil: Melchor, Ricardo Nestor. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; Argentina Fil: Bedatou, Emilio. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; Argentina Fil: de Valais, Silvina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Museo Paleontológico Egidio Feruglio; Argentina Fil: Genise, Jorge Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Museo Paleontológico Egidio Feruglio; Argentina

The Late Cretaceous Laguna Palacios Formation in Central Patagonia (San Jorge Basin), southern South America, is composed of tuffaceous deposits supplied by periodical volcanic ash falls partly reworked by rivers, on broad plains. Variations in ash-fall rates allowed the formation of stacked, mature paleosols, which are one of the most characteristic features of this formation. The mature paleosols show well-developed horizons, ped structure and bear an intricate network of trace fossils mostly produced by small roots and invertebrates. Two different insect trace fossils could be recognized in this formation: sweat bee nests and coleopteran pupal chambers. Fossil bee nests are composed of inclined tunnels with cells attached to them by means of short necks, a typical construction of bees of the subfamily Halictinae. Similar halictine constructions were reported from the Cretaceous of the USA. Coleopteran pupal chambers are discrete, ovoid structures, having an internal cavity with a smooth surface, and an outer wall of lumpy appearance composed of different layers of soil material. They are commonly constructed by the larvae of different families of Coleoptera. Similar trace fossils were previously reported from the Asencio Formation (Late Cretaceous–Early Tertiary) of Uruguay and from the Djadokhta Formation of Mongolia (Late Cretaceous). These trace fossils constitute some of the only paleontological data from the Laguna Palacios Formation, allowing inferences about its paleoecology, paleoclimatology and paleogeography. Ecological preferences of Halictinae, as well as some features of the nests, suggest a temperate, seasonal climate and an environment dominated by low vegetation for the Laguna Palacios Formation, which is also compatible with sedimentologic and pedogenic evidence. The morphology of the nests, typical of North American halictinae, adds more evidence to the hypothesis of the existence of faunal interchange between North and South America by the Late Cretaceous. The fossil nests constitute some of the oldest evidence of bees in the fossil record, the third known record of bees of Cretaceous age and the first for the Southern Hemisphere. The two traces described are, together with those of Dakota and the Gobi Desert, the only trace fossils from paleosols of Cretaceous age that can be certainly attributed to insects.

A new fossil termite nest, Tacuruichnus farinai n. ichnogen. n. ichnosp., is described from the Barranca de Los Lobos Formation (late Pliocene) of Buenos Aires province (Argentina). The preserved part of the nest is cup-shaped, being composed of a wall, 10 cm thick, bearing a net of anastomosed tunnels, and surrounding a central cavity filled with sediments. The exterior shows the remains of a peripheral tunnel system. The morphology of Tacuruichnus farinai closely resembles the hypogeal part of extant Cornitermes cumulans nests. C. cumulans is the southern species of the genus, which presently inhabits northern Argentina, about 1000 km north of the ichnofossil locality, in areas with an annual rainfall of more than 1500 mm and mean temperatures of more than 21°C. This new evidence is congruent with the warm and wet conditions postulated elsewhere for the Marplatan stage based upon other kinds of data, and contributes to a more precise statement of its palaeoclimatic conditions.