Laura C. Sarzetti

Odonatan Endophytic Oviposition from the Eocene of Patagonia: The Ichnogenus Paleoovoidus and Implications for Behavioral Stasis

Abstract We document evidence of endophytic oviposition on fossil compression/impression leaves from the early Eocene Laguna del Hunco and middle Eocene Río Pichileufú floras of Patagonia, Argentina. Based on distinctive morphologies and damage patterns of elongate, ovoid, lens-, or teardrop-shaped scars in the leaves, we assign this insect damage to the ichnogenus Paleoovoidus, consisting of an existing ichnospecies, P. rectus, and two new ichnospecies, P. arcuatum and P. bifurcatus. In P. rectus, the scars are characteristically arranged in linear rows along the midvein; in P. bifurcatus, scars are distributed in double rows along the midvein and parallel to secondary veins; and in P. arcuatum, scars are deployed in rectilinear and arcuate rows. In some cases, the narrow, angulate end of individual scars bear a darkened region encompassing a circular hole or similar feature indicating ovipositor tissue penetration. A comparison to the structure and surface pattern of modern ovipositional damage on dicotyledonous leaves suggests considerable similarity to certain zygopteran Odonata. Specifically, members of the Lestidae probably produced P. rectus and P. bifurcatus, whereas species of Coenagrionidae were responsible for P. arcuatum. Both Patagonian localities represent an elevated diversity of potential fern, gymnosperm, and especially angiosperm hosts, the targets of all observed oviposition. However, we did not detect targeting of particular plant families. Our results indicate behavioral stasis for the three ovipositional patterns for at least 50 million years. Nevertheless, synonymy of these oviposition patterns with mid-Mesozoic ichnospecies indicates older origins for these distinctive modes of oviposition.

The Aestivation Chamber of the Giant Earthworm Glossoscolex bergi (Glossoscolecidae) in the Subtropical Rainforest of Misiones (Argentina)

Glossoscolex bergi (Glossoscolecidae) is a giant earthworm from the rainforest of Misiones (Argentina). The large size of its aestivation chamber and the meniscate burrows connected to it allow us to describe morphological details and reinterpret some characteristics of the fossil counterpart Castrichnus incolumis. The concavity of menisci, either in the burrow or in those pellets lining the chamber, shows concentric ridges and radiating striae that result from the impression of the last segments of the body. The meniscate burrows associated to the chamber are different from described ichnospecies of Taenidium, because of the surface texture of the meniscus. The aestivation chamber was produced during an atypical four-month drought in a region that lacks a seasonal climate. This suggests that Castrichnus incolumis would be also an indicator of drought periods even in non seasonal climates.

The Phanerozoic Four Revolutions and Evolution of Paleosol Ichnofacies

The analysis of a database composed of 166 cases of invertebrate and root trace fossils in paleosols allowed us to recognize four major evolutionary steps in the Phanerozoic evolution of paleosol ichnofaunas. Each step constitutes a revolution that is reflected in the appearance of a new ichnofacies. The emergence of the first vascular plants during the late Silurian–Early Devonian produced the most significant change in soil evolution, the appearance of rooted Histosols, Spodosols, Alfisols, Ultisols, and forest Oxisols through the Devonian and Carboniferous. The first revolution, then, occurred in the Early Devonian with these first paleosols that exhibit ichnoassemblages composed of rhizoliths. Paleosols bearing only rhizoliths constitute half of the cases in the Paleozoic and are recorded through the whole Phanerozoic. These cases may compose an archetypal ichnofacies termed the Rhizolith Ichnofacies. The Rhizolith Ichnofacies would be indicative of subaerial exposure and depending on needed studies on root morphology, probably would yield more precise and significative data on paleoenvironment and vegetation in the near future. Other cases of Paleozoic ichnoassemblages can be included in the Scoyenia Ichnofacies. The second revolution took place after the end-Permian mass extinction. It is characterized by the appearance of trace fossil assemblages that include or are dominated by earthworm and crayfish trace fossils. These ichnoassemblages are grouped in a new archetypal ichnofacies, the Camborygma Ichnofacies. The second revolution was followed by stasis that ended during the Cretaceous, when the third revolution occurred. By that time, the appearance and diversification of flowering plants triggered the diversification of groups of soil-inhabiting insects, such as ants, termites, bees, wasps, and certain beetles, which were capable of constructing linings and free-standing walls for their chambers and nests that consequently acquired a high potential of preservation. By the Late Cretaceous, the first recognizable insect trace fossils in paleosols appear as isolated examples, integrating the Camborygma Ichnofacies, or composing a new one: the Celliforma Ichnofacies. The fourth and most diverse revolution took place in the Middle Eocene, with the advent of grass-dominated habitats during the long-term cooling-drying period after the EECO, and the full establishment of all groups of modern insects, including the ball-making dung beetles. The spread of grasses produced the last step in soil evolution, that is, the appearance of soils with fine granular peds that derived in Mollisols. Traces of cicadas, dung beetles, bees, sphinx moths, ants, termites, cleptoparasites, and detritivores appear or diversify during this revolution composing the Coprinisphaera Ichnofacies. By the Oligocene, in closed-forest environments, the first assemblage dominated by termite trace fossils is recorded, composing the Termitichnus Ichnofacies. This last revolution is followed during the Neogene by a stasis only interrupted by the occasional appearance of new trace fossils from the same groups of insects.

Predation of Soil-Nesting Centris muralis (Insecta: Apidae) by Armadillos (Zaedyus pichiy) (Mammalia: Cingulata) in La Rioja Province, Northwestern Argentina

Abstract This paper documents the predation of Centris muralis by Zaedyus pichiy. It presents the first detailed observations of the predation of solitary bee nests by a mammal in soils and reports the alternative use of soil mounds as a nesting site by Centris muralis.

The Nest Architecture of Diadasia hirta (Jörgensen) (Apidae: Emphorini) from La Rioja Province, Northwestern Argentina

Abstract Nests of Diadasia hirta are documented here for the first time. Nests have a cylindrical turret, one vertical principal burrow, cells disposed in linear series, and an oval pollen mass. Almost all observed behavioral traits and nest architecture features resemble those of other species of Diadasia. One exceptional behavior observed was pollen removal from the nest.