Using the extreme-macro technique to acquire images of microfossils is quite a recent methodology, easily accessible and do not require particular skills nor technical knowledge as the one required, as example, for electron microscopy. Both are complementary (SEM can attain of course huge magnifications, impossible with extreme-macro systems).
Microfossils are fossils that have generally a dimension included between 0.001mm and 1 mm in size, the study of which requires the use of light or electron microscopy. Fossils that have a dimension lower than 0.05m (50µm) are classed also in the nanofossils group.
Can be considered microfossils all the organisms or elements of organisms that have a bigger dimension, constituted by carbonate of calcium, silica, phosphate, organic components (chitina, sporopollenin), fragments of different origin and agglutinated together to create a “test” where the individual is living or part of a reproductive element, like pollens, oogones green algae (characeae).
Conodonts are tooth-like microfossils known from the Cambrian to the very end of the Triassic. Though their classification was long in limbo, and knowledge about their soft tissues remains limited, they are believed to be elements from extinct jawless chordates that resembled eels. Conodonts are important index fossils.
Scolecodonts are the jaws of polychaete annelids (segmented bristle worms). Fossil scolecodonts are particularly common in Ordovician, Silurian, and Devonian marine deposits, but the organisms they come from have existed from the Cambrian to the Present. The vast majority of species are marine. Though scolecodonts are generally tiny, one of the largest scolecodonts ever found—Websteroprion armstrongi from the Devonian of Canada —was more than a centimeter in length and is estimated to have belonged to a giant worm that may have grown as long as a meter.
Foraminifera are the external shells (or “tests”) of single-celled protists (that is, organisms that are classified as neither animal, plant, or fungus). Most foraminifera are marine, and the majority of these species live on or within seafloor sediment. In their forms and shapes, they are among the most diverse of microscopic creatures. As fossils, they are valued as indicators of paleoclimate and as index fossils.
Charophyta is a group of specialized freshwater algae that includes the closest relatives of the embryophyte plants (that is, most of what we think of as vegetation: liverworts, mosses, ferns, vascular plants, gymnosperms, and flowering plants). Oogonia are female reproductive structures in charophytes and appear as rounded cells or sacs containing one or more fertilizable gametes (sex cells).
Ostracods, are a class of the Crustacea. They are small typically around 1 mm in size, but varying from 0.2 to 30 mm in the case of Gigantocypris. Their bodies are flattened from side to side and protected by a bivalve-like, chitinous or calcareous valve or “shell”. Marine ostracods can be part of the zooplankton or (most commonly) are part of the benthos, living on or inside the upper layer of the sea floor. Many ostracods are also found in fresh water, and some terrestrial species are known from humid forest soils of South Africa, Australia and New Zealand. Ostracods are by far the most common arthropods in the fossil record with fossils being found from the early Ordovician to the present. Ostracods have been particularly useful for the biozonation of marine strata on a local or regional scale, and they are invaluable indicators of paleoenvironments.
Extinct genus of conical fossils of uncertain affinity, class Tentaculita. This class is known from Lower Ordovician to Middle Jurassic deposits, shell composed by calcite. Tentaculitids have ribbed, cone-shaped shells which range in length from 5 to 20 mm. They were suspension feeder with a worldwide distribution. Some species are septate arguing for cephalopod affinity; their embryonic shell, which is retained, forms a small, sometimes spherical, chamber.
Chitinozoa is a taxon of “flask-shaped” organic walled marine microfossils produced by an as yet unknown organism. They are common from the Ordovician to Devonian and have had a worldwide distribution making them a valuable stratigraphic biomarker. They are interpreted as sac egg, juvenile stages of graptolites, tintinnids, amoebae, photosynthesis organisms, juvenile stage of some kind of marine organism, or a test of an undefined protist…
The Radiolaria are small protozoa of a diameter of 100-200µm characterized by a complex transparent silica skeleton. Distributed worldwide, appeared in the Cambrian period. Their skeletons are frequently used in geological dating, including the oil exploration and paleoclimatology.
Its not rare to find, in marine sediments characterized by sand, marls, and clays, microfossils of teeth of fishes, small bones, otolites (part of auditive organ of fishes). The sands coming from the Maastrichtian (upper Cretaceous) of Morocco are extremely riches on these fossils.