The cloudinids, an early metazoan family containing the genera Acuticocloudina, Cloudina and Conotubus, lived in the late Ediacaran period about 550 million years ago. and became extinct at the base of the Cambrian. They formed millimetre-scale conical fossils consisting of calcareous cones nested within one another; the appearance of the organism itself remains unknown. The name Cloudina honors the 20th-century geologist and paleontologist Preston Cloud.
Vernanimalcula guizhouena is an acritarch dating from 600 to 580 million years ago; it was between 0.1 and 0.2 mm across. Vernanimalcula means "small spring animal", referring to its appearance in the fossil record at the end of the Marinoan Glaciation and the belief upon discovery it was an animal.
The halkieriids are a group of fossil organisms from the Lower to Middle Cambrian. Their eponymous genus is Halkieria, which has been found on almost every continent in Lower to Mid Cambrian deposits, forming a large component of the small shelly fossil assemblages. The best known species is Halkieria evangelista, from the North Greenland Sirius Passet Lagerstätte, in which complete specimens were collected on an expedition in 1989. The fossils were described by Simon Conway Morris and John Peel in a short paper in 1990 in the journal Nature. Later a more thorough description was undertaken in 1995 in the journal Philosophical Transactions of the Royal Society of London and wider evolutionary implications were posed.
The Ediacaranbiota is a taxonomic period classification that consists of all life forms that were present on Earth during the Ediacaran Period. These were enigmatic tubular and frond-shaped, mostly sessile, organisms. Trace fossils of these organisms have been found worldwide, and represent the earliest known complex multicellular organisms. The term "Ediacara biota" has received criticism from some scientists due to its alleged inconsistency, arbitrary exclusion of certain fossils, and inability to be precisely defined.
The Chancelloriids are an extinct family of superficially sponge-like animals common in sediments from the Early Cambrian to the early Late Cambrian. Many of these fossils consists only of spines and other fragments, and it is not certain that they belong to the same type of organism. Other specimens appear to be more complete and to represent sessile, radially symmetrical hollow bag-like organisms with a soft skin armored with star-shaped calcareous sclerites from which radiate sharp spines.
Shelly limestone is a highly fossiliferous limestone, composed of a number of fossilized organisms such as brachiopods, bryozoans, crinoids, sponges, corals and mollusks. It varies in color, texture and hardness. Coquina is a poorly indurated form of shelly limestone.
Helcionellid or Helcionelliformes is an order of small fossil shells that are universally interpreted as molluscs, though no sources spell out why this taxonomic interpretation is preferred. These animals are first found about 540 to 530 million years ago in the late Nemakit-Daldynian age, which is the earliest part of the Cambrian period. A single species persisted to the Early Ordovician. These fossils are component of the small shelly fossils (SSF) assemblages.
The small shelly fauna, small shelly fossils (SSF), or early skeletal fossils (ESF) are 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. They are very diverse, and there is no formal definition of "small shelly fauna" or "small shelly fossils". Almost all are from earlier rocks than more familiar fossils such as trilobites. Since most SSFs were preserved by being covered quickly with phosphate and this method of preservation is mainly limited to the late Ediacaran and early Cambrian periods, the animals that made them may actually have arisen earlier and persisted after this time span.
The Cambrian explosion is an interval of time approximately 538.8 million years ago in the Cambrian period of the early Paleozoic when a sudden radiation of complex life occurred, and practically all major animal phyla started appearing in the fossil record. It lasted for about 13 to 25 million years and resulted in the divergence of most modern metazoan phyla. The event was accompanied by major diversification in other groups of organisms as well.
Tumulduria is a Cambrian small shelly fossil. It is phosphatic, and approximately bilaterally symmetrical. It was first described by Missazhevskii from the Tommotian Stage of the Aldan River. It represents part of a pateriniid brachiopod.
Tommotiids are an extinct group of Cambrian invertebrates thought to be early lophophorates.
Stenothecidae is an extinct family of fossil univalved Cambrian molluscs which may be either gastropods or monoplacophorans.
Eiffelia is an extinct genus of sponges known from the Middle Cambrian Burgess Shale as well as several Early Cambrian small shelly fossil deposits. It is named after Eiffel Peak, which was itself named after the Eiffel Tower. It was first described in 1920 by Charles Doolittle Walcott. It belongs in the Hexactinellid stem group. 60 specimens of Eiffelia are known from the Greater Phyllopod bed, where they comprise 0.11% of the community.
Stenothecoida is a taxon of bivalved fossils from the Early to middle Cambrian period. They look a bit like brachiopods or bivalve molluscs.
Mongolitubulus is a form genus encapsulating a range of ornamented conical small shelly fossils of the Cambrian period. It is potentially synonymous with Rushtonites, Tubuterium and certain species of Rhombocorniculum, and owing to the similarity of the genera, they are all dealt with herein. Organisms that bore Mongolitubulus-like projections include trilobites, bradoriid arthropods and hallucigeniid lobopodians.
The anabaritids or angustiochreids are enigmatic tubular, mineralizing organisms with a trifold symmetry known from their Lower Cambrian fossils. They may have represented cnidaria, but their affinity within the Metazoa is difficult to constrain.
Protoconodonts are an extinct group of Cambrian animals known from fossilized phosphatic tooth-like structures. They were originally described as an informal group of early conodonts, though more recent studies consider them to be more closely related to chaetognaths.
Tannuolina is a genus of tommotiid, belonging to the brachiopod stem lineage.
The camenellans, consisting of the genera Camenalla, Dailyatia, Kennardia, Kelanella, Wufengella and Lapworthella, are a group of Tommotiid invertebrates from the Cambrian period, reconstructed as sister to all others. They are primarily known from isolated sclerites, but are believed to have a scleritomous, Halkieria-like construction. This was confirmed by the discovery of Wufengella, known from articulated remains, which showed camenellans to be mobile, worm-like animals.
