Index fossils

Archaeocyatha (, "ancient cups") is a taxon of extinct, sessile, reef-building marine sponges that lived in warm tropical and subtropical waters during the Cambrian Period. It is thought that the centre of the Archaeocyatha origin is now located in East Siberia, where they are first known from the beginning of the Tommotian Age of the Cambrian, 525 million years ago (mya). In other regions of the world, they appeared much later, during the Atdabanian, and quickly diversified into over a hundred families. They became the planet's first reef-building animals and are an index fossil for the

mineralized fossils, many only a few millimetres long, with a nearly continuous record from the latest stages of the Ediacaran to the end of the Early Cambrian Period.

Olenellus is an extinct genus of redlichiid trilobites, with species of average size (about long). It lived during the Botomian and Toyonian stages of the Lower Cambrian (Olenellus-zone), , in what is currently North America, part of the palaeocontinent Laurentia.

Redlichia is a genus of redlichiid trilobite in the family Redlichiidae, with large to very large species (up to long). Fossils of various species are found in Lower Cambrian (Toyonian)-aged marine strata from China, Korea, Pakistan, the Himalayas, Iran, Spain, southern Siberia, and Antarctica, and from Middle Cambrian (Ordian)-aged marine strata of Australia.

Pachydiscus is an extinct genus of ammonite from the Late Cretaceous and Early Paleocene with a worldwide distribution, and type for the desmoceratacean family Pachydiscidae. The genus' type species is P. neubergicus. Altogether some 28 species have been described.

Treptichnus is a genus of trace fossils (with modern analogues) representing a three-dimensional burrow. These fossil traces are known from marine, brackish, and freshwater deposits from the Ediacaran (550 million years ago) to the Upper Oligocene (24 mya).

Psiloceras is an extinct genus of ammonite. Psiloceras is among the earliest known Jurassic ammonites, and the appearance of the earliest Psiloceras species form the definition for the base of the Jurassic. Unlike most earlier ammonites, which had complex shell shapes and ornamentation, Psiloceras had a smooth shell.

thumb|Monograptus sp. from the Wenlock of Vailhan, Hérault, France. 12 cm block. Graptolites preserved in three dimensions.

Discoaster is a genus of extinct star-shaped marine algae, with calcareous exoskeletons of between 5-40 μm across that are abundant as nanofossils in tropical deep-ocean deposits of Neogene age. Discoaster belongs to the haptophytes. About 100 species can be recognized.

Berriasella is a discoidal evolute perisphinctacean ammonite, and type genus for the neocomitid subfamily Berriasellinae. Its ribbing is distinct, consisting of both simple and bifurcated ribs that extend from the umbilical seam across the venter; its whorl section generally compressed, the venter more or less narrowly rounded. The species Berriasella jacobi traditionally has been regarded an index fossil defining the base of the Cretaceous, however since 2016 this had been replaced by the first occurrence of Calpionella alpina. Some authors regard B. jacobi as instead belonging to the genus S

species of alga

Acanthodiscus is an extinct ammonoid cephalopod genus from the order Ammonitida and included in the persphinctacean family Berriasellidae. The type species, named by Bruguière, 1792, is Acanthodiscus radiatus.

Hindeodus is an extinct genus of conodonts in the family Anchignathodontidae. The generic name Hindeodus is a tribute to George Jennings Hinde, a British geologist and paleontologist from the 1800s and early 1900s. The suffix -odus typically describes the animal's teeth, essentially making Hindeodus mean Hinde-teeth.

thumb|200 px|Spitidiscus seunesi (Wilfrid Kilian|Kilian) [[Barremian, Brestak, Cr1 426X1 (Coll. St. Breskovski) at the Sofia University Museum of Paleontology and Historical Geology]] Spitidiscus is a genus of ammonites placed in the family Holcodiscidae.

Phyllograptus is a graptolite genus of the order Graptoloidea, in the family Tetragraptidae.