Cnidaria is a phylum under kingdom Animalia containing over 11,000 species of aquatic invertebrates found both in fresh water and marine environments, including jellyfish, hydroids, sea anemones, corals and some of the smallest marine parasites. Their distinguishing features are an uncentralized nervous system distributed throughout a gelatinous body and the presence of cnidocytes or cnidoblasts, specialized cells with ejectable flagella used mainly for envenomation and capturing prey. Their bodies consist of mesoglea, a non-living, jelly-like substance, sandwiched between two layers of epithelium that are mostly one cell thick. Cnidarians are also some of the few animals that can reproduce both sexually and asexually.
The Ediacaran is a geological period of the Neoproterozoic Era that spans 96 million years from the end of the Cryogenian Period at 635 Mya to the beginning of the Cambrian Period at 538.8 Mya. It is the last period of the Proterozoic Eon as well as the last of the so-called "Precambrian supereon", before the beginning of the subsequent Cambrian Period marks the start of the Phanerozoic Eon, where recognizable fossil evidence of life becomes common.
Placozoa is a phylum of free-living (non-parasitic) marine invertebrates. They are blob-like animals composed of aggregations of cells. Moving in water by ciliary motion, eating food by engulfment, reproducing by fission or budding, placozoans are described as "the simplest animals on Earth." Structural and molecular analyses have supported them as among the most basal animals, thus, constituting a primitive metazoan phylum.
Kimberella is an extinct genus of bilaterian known only from rocks of the Ediacaran period. The slug-like organism fed by scratching the microbial surface on which it dwelt in a manner similar to the gastropods, although its affinity with this group is contentious.
Beothuk, also called Beothukan, is an extinct language once spoken by the indigenous Beothuk people of Newfoundland. The Beothuk have been extinct since 1829, and there are few written accounts of their language. Hence, little is known about it, with practically no structural data existing for Beothuk.
Medusozoa is a clade in the phylum Cnidaria, and is often considered a subphylum. It includes the classes Hydrozoa, Scyphozoa, Staurozoa and Cubozoa, and possibly the parasitic Polypodiozoa. Medusozoans are distinguished by having a medusa stage in their often complex life cycle, a medusa typically being an umbrella-shaped body with stinging tentacles around the edge. With the exception of some Hydrozoa, all are called jellyfish in their free-swimming medusa phase.
Staurozoa is a class of Medusozoa. It has one extant order: Stauromedusae with a total of 50 known species. A fossil group called Conulariida has been proposed as a second order, although this is highly speculative. The extinct order is largely unknown and described as a possibly cnidarian clade of marine life with shell-like structures, the Conulariida. Staurozoans are small animals that live in marine environments, usually attached to seaweeds, rocks, or gravel. They have a large antitropical distribution, a majority found in boreal or polar, near-shore, and shallow waters. Few staurozoans are found in warmer tropical and subtropical water environments of the Atlantic, Indian, and Pacific Ocean basins, but most are known from the Northern Hemisphere. Over the years the number of discovered species has increased, with an estimated 50 species currently recognized. Information on Staurozoa is sparse, and it is one of the least studied groups within Cnidaria. While often neglected, correctly recognizing the characteristics of this class is crucial for understanding cnidarian evolution.
Vendobionts or Vendozoans (Vendobionta) are a proposed very high-level, extinct clade of benthic organisms that made up of the majority of the organisms that were part of the Ediacaran biota. It is a hypothetical group. It would be the oldest of the animals that populated the Earth about 580 million years ago, in the Ediacaran period. They became extinct shortly after the so-called Cambrian explosion, with the introduction of fauna forming groups more recognizably related to modern animals, however sponges may be descended from this clade. It is likely that the whole Ediacaran biota is not a monophyletic clade and not every genus placed in its subtaxa is an animal.
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.
Marine invertebrates are invertebrate animals that live in marine habitats, and make up most of the macroscopic life in the oceans. It is a polyphyletic blanket term that contains all marine animals except the marine vertebrates, including the non-vertebrate members of the phylum Chordata such as lancelets, sea squirts and salps. As the name suggests, marine invertebrates lack any mineralized axial endoskeleton, i.e. the vertebral column, and some have evolved a rigid shell, test or exoskeleton for protection and/or locomotion, while others rely on internal fluid pressure to support their bodies. Marine invertebrates have a large variety of body plans, and have been categorized into over 30 phyla.
The urbilaterian is the hypothetical last common ancestor of the bilaterian clade, i.e., all animals having a bilateral symmetry.
The Avalon explosion, named from the Precambrian faunal trace fossils discovered on the Avalon Peninsula in Newfoundland, eastern Canada, is a proposed evolutionary radiation of prehistoric animals about 575 million years ago in the Ediacaran period, with the Avalon explosion being one of three eras grouped in this time period. This evolutionary event is believed to have occurred some 33 million years earlier than the Cambrian explosion, which had been long thought to be when complex life started on Earth.
The Mistaken Point Formation is a geologic formation in Newfoundland and Labrador. It is recognized as a Lagerstätte preserving fossils dating back to the Ediacaran period. It contains a stratum dated to 565 ± 3 million years ago.
Haootia quadriformis is an extinct animal belonging to the Ediacaran biota. Estimated to be about 560 million years old, H. quadriformis is identified as a cnidarian polyp, and represents the earliest known evidence for muscle tissue in an animal. Discovered in 2008 from Newfoundland in eastern Canada, it was formally described in 2014. It is the first Ediacaran organism discovered to show fossils of muscle fibres. Structural examination of the muscles and morphology indicate that the animal is a cnidarian, though, which class H. quadriformis belongs to was undetermined until a 2024 study found it to be a staurozoan.
Pambikalbae is a monospecific genus known from the Ediacaran Period of South Australia. Its morphology resembles the morphology of colonial cnidarians, such as sea pens or siphonophores.
Frondosity is the property of an organism that normally flourishes with fronds or leaf-like structures.
Ikaria wariootia is an early example of a wormlike, 2–7 mm-long (0.1–0.3 in) bilaterian organism. Its fossils are found in rocks of the Ediacara Member of South Australia that are estimated to be between 560 and 555 million years old. A representative of the Ediacaran biota, Ikaria lived during the Ediacaran period, roughly 15 million years before the Cambrian, when the Cambrian explosion occurred and where widespread fossil evidence of modern bilaterian taxa appear in the fossil record.
Hylaecullulus fordi, also described as dumbbells, is an extinct species of Ediacaran petalonamid whose fossils were found in the Charnwood Forest of Leicestershire, England. It serves as an important rangeomorph because of its multifoliate anatomy. Its overall body plan is similar to that of a goblet, from which its name, Hylaecullulus, alongside its common name of dumbbell, is derived from.
Lobodiscus is an extinct genus of Ediacaran trilobozoans from China, discovered early in 2024. The genus contains a single species, Lobodiscus tribrachialis.
