Enigmatic prehistoric animal genera

Tullimonstrum, colloquially known as the Tully monster or sometimes '''Tully's monster, is an extinct genus of soft-bodied bilaterian marine animal that lived in shallow tropical coastal waters of muddy estuaries during the Pennsylvanian, about 310 million years ago. A single species, T. gregarium', is known. Examples of Tullimonstrum'' have been found only in sediments deposited far from the palaeocoast (formally termed the Essex biota), in the Mazon Creek fossil beds of Illinois, United States. Its classification has been the subject of controversy, and interpretations of the fossil have lik

Kimberella is an extinct genus of marine 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.

Yunnanozoon lividum (from Yunnan, and Ancient Greek ζῷον (zôion), meaning "animal", with specific name coming from Latin lividum; (lead-coloured), referring to preserved colour of specimens) is an extinct species of bilaterian animal from the Lower Cambrian Chengjiang biota of Yunnan province, China. Its affinities have long been the subject of controversy.

Trilobozoa, from Ancient Greek τρεῖς (treîs), meaning "three", λοβός (lobós), meaning "lobe", and ζῷον (zôion), meaning "animal", is a phylum of extinct, sessile animals that were originally classified into the Cnidaria. The basic body plan of trilobozoans is often a triradial or radial sphere-shaped form with lobes radiating from its centre. Fossils of trilobozoans are restricted to marine strata of the Late Ediacaran period.

Parvancorina is a genus of shield-shaped bilaterally symmetrical fossil animal that lived in the late Ediacaran seafloor. It has some superficial similarities with the Cambrian trilobite-like arthropods.

Dinomischus is an extinct genus of stalked filter-feeding animals within the Cambrian period, with specimens known from the Burgess Shale, the Maotianshan Shales, the Kaili Formation and the Marjum Formation. While long of uncertain affinities, recent studies have suggested it to be a stem-group ctenophore.

Arkarua adami is a small, Precambrian disk-like fossil with a raised center, a number of radial ridges on the rim, and a five-pointed central depression marked with radial lines of five small dots from the middle of the disk center. Fossils range from 3 to 10 mm in diameter.

Namacalathus is a problematic metazoan fossil occurring in the latest Ediacaran. The first, and only described species, N. hermanastes, was first described in 2000 from the Nama Group of central and southern Namibia.

Yuyuanozoon magnificissimi, from the Cambrian Stage 3 Chengjiang lagerstatte, is the largest known vetulicolian, an extinct species of marine animal, with specimens up to 20 cm in length compared to 5–14 cm for other vetulicolian species.

Funisia is a genus of extinct, colonial sponge-like organisms from the late Ediacaran of South Australia. It is the most common genus within the fossils beds it is known from, and may have partially driven the paleoenvironment and paleoecology of the areas in which it was found by stopping other organisms from taking hold, or providing nutrients upon a mass death. It is a monotypic genus, containing only Funisia dorothea.

Inaria is an Ediacaran fossil. It is found in the Chace Range in Australia, and the White Sea area in Russia.

Thectardis avalonensis is a triangular-shaped member of the Ediacaran biota, dating from . The organism took the form of an elongated cone with a central depression, and its apex was anchored to the substrate. Sperling et al. (2011) suggest that Thectardis was a sponge, while Antcliffe et al. (2014, 2015) instead suggest that it is the decayed remains of rangeomorphs.

Volborthella is an animal of uncertain classification, whose fossils pre-date . It has been considered for a period a cephalopod. However discoveries of more detailed fossils showed that Volborthella’s small, conical shell was not secreted but built from grains of the mineral silicon dioxide (silica), and that it was not divided into a series of compartments by septa as those of fossil shelled cephalopods and the living Nautilus are. This illusion was a result of the laminated texture of the organisms' tests. Therefore, Volborthella's classification is now uncertain. It has been speculated tha

Echmatocrinus brachiatus is an extinct species of Cambrian animal which resembles a crinoid or an octocoral. Its exact taxonomy is still a subject of debate. It is known only from the Burgess Shale. Around 20 specimens of Echmatocrinus are known; these comprise <0.02% of the community.

Anabarites is a problematic lower Cambrian genus, and is one of the small shelly fossils. It was abundant in the early Tommotian and is also found in the Nemakit-Daldynian. The fossils represent the triradially symmetrical mineralised tube in which the organism dwelt; it was sedentary. It is named after the Anabar region in Yakutia, Russia; its name does not imply 'heavy'.

Burykhia hunti is an Ediacaran fossil from the White Sea region of Russia dating to . It is considered of possibly ascidian affinity, due to the sac-like morphology and a series of distinctly perforated bands reminiscent of a tunicate pharynx. If B. hunti is a tunicate, it could be the oldest ascidian fossil known as of its publication in 2012. It is also possibly related to the slightly younger Ausia, another putative ascidian from the Vendian biota in Namibia.

Eoandromeda is an Ediacaran organism consisting of eight radial spiral arms, and known from two taphonomic modes: the standard Ediacara type preservation in Australia, and as carbonaceous compressions from the Doushantuo formation of China, where it is abundant.

Xianguangia is a soft-bodied stem ctenophore assigned to Dinomischiidae from the Chengjiang Biota of China.

Skeemella is a genus of elongate animal from the Middle Cambrian Wheeler Shale and Marjum lagerstätte of Utah. It has been classified with the banffozoan vetulicolians.

Vaveliksia is an extinct genus of Ediacaran Sponge-like organism with a long, tubular-shaped body from the formations within Northwestern Russia, Ukraine, and possibly Australia.

Tommotia is a small shelly fossil from the Early Cambrian Period. Originally, only a cone-shaped shell was recognized, which was originally thought to be an early cephalopod, with either squid-like tentacles or a snail-like foot. More recent investigation has shown that the cone is not the remains of a complete animal, but a sclerite of a larger, soft-bodied animal that would have resembled a chiton or a sea mouse. The fossils called Camanella may be another type of sclerite from the same animal.

Armillifera parva is a species of Ediacaran proarticulate first described by Mikhail Fedonkin in 1980. Its fossils were discovered in the White Sea area, Arkhangelsk Region, Russia. These fossils of A. parva were restricted to almost the same stratigraphic range as Kimberella, although fossils of both organisms have been rarely found.