El registre paleontològic de l’illa d’Eivissa a jaciments litorals pleistocens

[cat] Es presenta des d’una visió històrica, l’estudi del registre paleontològic del Pleistocè de l’illa d’Eivissa, des dels seus inicis a finals del segle XIX fins l’actualitat, per després comentar els jaciments de platja i els que contenen fòssils continentals. Els primers són escassos per la qual cosa hi ha un registre baix de tàxons marins. Els jaciments d’origen continental són nombrosos i el registre paleontològic es caracteritza per a presentar mol·luscs endèmics (Tudorella ferruginea) i en alguns indrets traces fòssils d’insecte (i.e. Rebuffoichonus casamiquelai).[eng] This article gives a historical view of the Pleistocene on the island of Ibiza, from its beginnings in the late nineteenth century to the present. Then, beach deposits are synthetically described focusing on paleontological content and finally, the deposits that contain continental fauna. The first ones are scarce, for this reason there is a few marine taxa registers. Moreover, there are a high number of continental deposits and their paleontological data is characterized by endemic Mollusca and in some sites there are insect traces

Rhizolith balls from the Lower Cretaceous of Patagonia: Just roots or the oldest evidence of insect agriculture?

A new type of trace fossil from the Lower Cretaceous of Patagonia that may record the oldest evidence of insect agriculture is represented by biconvex, sub-spherical, carbonate balls composed of a dense mass of rhizoliths. The best preserved balls show an external wall, a tunnel entrance, and vertical, large rhizoliths crossing from top to base, from which a mass of smaller rhizoliths arise. In some cases there is a pelletal surface texture in internal layers of the wall. Some specimens show meniscate tubes attributed to organisms different than the constructors of the chambers, probably attracted by the original organic matter. Micromorphology, analyzed by thin sections and SEM, shows strong evidence of high fungal activity associated to the original roots. Four different hypotheses are analyzed to explain the origin of the balls. The less probable ones are either that the balls were produced only by a self induced and localised overgrowth of secondary and tertiary rootlets from a group of neighbouring primary roots, or that they were crayfishes' feeding chambers. Rhizolith arrangement, as well as other characters, essentially rule out both hypotheses. The hypotheses involving social insects, termites and ants, are more risky, considering the lack of support from the body fossil record, the biogeography of these extant insects, and particularly the lack of definitive evidence of discrete fungus or bacterial gardens in the balls. However, the trace fossils described herein partially resemble the nests and behaviour of the African termite Sphaerothermes sphaerothorax, particularly because of the presence of roots inside a thick lined chamber excavated around them to cultivate bacterial combs. The ant origin of these balls is at least a hypothesis to explore considering the size, shape, wall, entrance tunnel, presence of traces of associated organisms, and particularly roots. The roots and wall relate these balls to hypothesised scenarios for the origin of fungus agriculture in ants. One hypothesis suggests that primitive Attini developed fungus agriculture from the habit of feeding on fungi associated with roots (mycorrhizae) and still other proposes that adventitious fungi on nest walls were responsible for the arise of fungiculture. The balls would supply physical evidence that by the lower Cretaceous some social insects excavated chambers around uncut roots, which in turn provided optimal conditions for fungi development. These rhizolith balls possibly constitute the oldest physical evidence for the origin of fungiculture in social insects, and represent a critical contribution of ichnology to this hot topic intensively discussed on the basis of a scattered body fossil record and molecular phylogen

Traces within traces : holes, pits and galleries in walls and filling of insect trace fossils in paleosols

Fossil insect nests with constructed walls (ichnogenera Uruguay ROSELLI 1938, Palmiraichnus ROSELLI 1987, Rosellichnus GENISE and BOWN 1996), as well as fossil brood masses from dung beetles (Monesichnus ROSELLI 1987) often display pits or galleries made by inquilines, parasitoids, cleptoparasites and scavengers, which develop and/or feed inside them. Some of these "traces within traces" can be distinguished, using morphologic criteria, as separate ichnotaxa. Tombownichnus n. igen. is represented by circular to subcircular holes or paraboloid external pits occurring in discrete walls of chambers made of agglutinated soil material. T. plenus n. isp. consists of a complete perforation, mostly cylindrical in longitudinal section, which pierces whole thickness of the cell wall. Tombownichnus parabolicus n. isp. includes incomplete perforations, i.e. pits, parabolic, conic or subcylindrical in longitudinal section, on the external surface of the chamber wall. Lazaichnus fistulosus n. igen., n. isp. is composed of circular to subcircular holes occurring in constructed walls of chambers made of agglutinated soil material, which are connected to an internal gallery in their infillings. The trace fossils described herein may be the first formal records of this hitherto neglected but promising field of ichnologic research

Traces within traces : holes, pits and galleries in walls and filling of insect trace fossils in paleosols

Fossil insect nests with constructed walls (ichnogenera Uruguay ROSELLI 1938, Palmiraichnus ROSELLI 1987, Rosellichnus GENISE and BOWN 1996), as well as fossil brood masses from dung beetles (Monesichnus ROSELLI 1987) often display pits or galleries made by inquilines, parasitoids, cleptoparasites and scavengers, which develop and/or feed inside them. Some of these "traces within traces" can be distinguished, using morphologic criteria, as separate ichnotaxa. Tombownichnus n. igen. is represented by circular to subcircular holes or paraboloid external pits occurring in discrete walls of chambers made of agglutinated soil material. T. plenus n. isp. consists of a complete perforation, mostly cylindrical in longitudinal section, which pierces whole thickness of the cell wall. Tombownichnus parabolicus n. isp. includes incomplete perforations, i.e. pits, parabolic, conic or subcylindrical in longitudinal section, on the external surface of the chamber wall. Lazaichnus fistulosus n. igen., n. isp. is composed of circular to subcircular holes occurring in constructed walls of chambers made of agglutinated soil material, which are connected to an internal gallery in their infillings. The trace fossils described herein may be the first formal records of this hitherto neglected but promising field of ichnologic research

New termite trace fossils: galleries, nests and fungus combs from the Chad Basin of Africa (Upper Miocene-Lower Pliocene)

International audienc

Megarhizoliths in Pleistocene aeolian deposits from Gran Canaria (Spain): Ichnological and palaeoenvironmental significance

The Pleistocene dune field of Tufia, located on the east of Gran Canaria (Spain), contains different stratigraphic levels of indurated pillar-like structures that are interpreted as megarhizoliths. The megarhizoliths occur at the top of different aeolian sets and reach 31.5 cm in diameter and over 1 m in height. These scattered, free-standing, vertical, cylindrical-to-slightly conical columns usually appear as hollow cylinders, displaying elliptical cross-sections aligned with the prevailing wind. On the leeward side of some specimens the external wall shows a tail of rock matrix resembling a sort of “wind shadow”. These tails and other remains of the associated rock matrix show a texture composed of long, horizontal, parallel cylinders orientated with the wind. Internally the most complete structures show five concentrically arranged zones: Zone (a), is a central pore corresponding to the cavity originally occupied by the root; Zones (b) and (c), which include alveolar and laminated carbonate textures indicating that carbonate precipitation was mostly induced by the roots and their associated microorganisms; and Zones (d) and (e), consisting mostly of aeolian sands. In (d) the sand grains show thin micritic coatings whereas in (e) vadose aragonite cements can be seen on the grain surface suggesting a less biogenic influence in their formation. The degree of cementation and the time of the precipitation of carbonate around the roots controlled the preservation of these zones. Thus, in some cases, Zones b, c and/or d are not preserved. Cylinders are up to 30× the diameter of the root that nucleated them. The presence of the megarhizoliths at the top of the aeolianite beds indicates that aeolian sedimentation halted several times, allowing soil formation and plant colonisation during slightly more humid periods. The occurrence of megarhizoliths is further proof of the alternation of arid and slightly more humid climates in the north Atlantic during the last glacial period. It is also noted that they may be misinterpreted as animal trace fossils or tree trunk casts, resulting in incorrect ichnological or palaeoenvironmental interpretations

Nesting behaviour and larval biology of Sphex opacus Dahlbom (Hymenoptera, Sphecidae) from Brazil

Aspects of the nesting behaviour of Sphex opacus Dahlbom, 1845 are presented for the first time, based on observations carried out in a coastal habitat from southeastern Brazil. Larval behaviour and development were studied in laboratorial conditions.<br>Aspectos do comportamento de nidificação de Sphex opacus Dahlbom, 1845 são apresentados pela primeira vez, com base em observações feitas em um habitat costeiro do sudeste do Brasil. O comportamento e o desenvolvimento da larva foram estudados em condições de laboratório