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An extinct and specialized group of land fossil birds that lived during the Cretaceous Period. Enantiornithes represents the most diverse avian group in the Mesozoic. This group was not discovered until 1981, at which time some very unusual, isolated bones from the Late Cretaceous of Argentina were recognized as belonging to a new group of birds. Enantior- nithine birds are now known to be widely distri- buted, with remains from Argentina, North America, Mexico, Mongolia, Australia, Spain, and China. Because their anatomy includes a mixture of specialized and primitive features, they are thought to represent an evolutionary side branch in early avian evolution that became extinct at the end of the Cretaceous and left no living descendants.
Industry:Science
An extinct clade (evolutionary lineage) of eosaurop-terygian reptiles (that is, a suborder of Eosauropterygia) that also includes pachypleurosaurs (suborder Pachypleurosauria) and pistosaurs (suborder Pistosauroidea). Representatives of these groups are known from uppermost Lower Triassic to Upper Triassic marine deposits in Europe, the Near and Middle East, Northern Africa, China, and North America. Triassic nothosaurs and their relatives are typically restricted to near-shore habitats or shallow epicontinental seas. Some derived members of the pistosaurs constitute the sister group (closest relatives) to plesiosaurs, a clade that greatly diversified during the Jurassic and Cretaceous.
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An extinct class of small, disk-shaped echinozoans in which the lower surface of the body probably consisted of a suction cap for adhering to substrate, and the upper surface was covered by separate plates arranged in concentric rings. The mouth lay at the center of the upper surface, and the anus, also on the upper surface, lay some distance between the margin and the mouth. Little is known of the habits of cyclocystoids. They occur in rocks of middle Ordovician to middle Devonian age in Europe and North America.
Industry:Science
An extinct class of the division Lycophyta, comprising primitive vascular land plants that evolved from the rhyniophytes and reached a relatively brief peak in the late Early Devonian, when they were an ecologically important and widely distributed element of the exclusively herbaceous terrestrial flora.
Industry:Science
An extinct family of flying birds that represents one of the most primitive avian groups. It comprises three genera (<i>Confuciusornis</i>, <i>Changchengornis</i>, and <i>Jinzhouornis</i>) and is known exclusively from western Liaoning Province and neighboring areas in northeastern China. Fossils of this group have been collected from the Yixian and Jiufotang formations, which represent freshwater lake deposits that were formed in the Early Cretaceous period 125–120 million years ago.
Industry:Science
An extinct group of Cretaceous toothed birds. All members were foot-propelled, seagoing birds that could reach the size of a modern Emperor penguin. The largest known hesperornithiform reached a maximum length of over 5 ft (1.5 m). All of the known fossils are from marine rocks that are Cretaceous in age (about 100–65 million years old); they are most abundant from North America, especially Kansas. Although these birds are thought to be closely related to living birds (the group or clade Neornithes)—along with Ichthyornithiformes—the evolutionary interrelationships among Hesperornithiformes are not well understood by paleontologists.
Industry:Science
An extinct group of epifaunal bivalves that constructed reefs during the late Mesozoic. The valves of rudists are coiled to cylindrical in external form, and the shapes and sizes of rudist shells are extreme relative to other members of the class Bivalvia. Rudists lived as solitary individuals or in large clusters on predominantly carbonate substrates in low to mid-paleolatitudes until their demise near or at the end of the Cretaceous.
Industry:Science
An extinct group of fossil organisms generally referred to as the Mesozoic stromatoporoids. As originally proposed by Othmar Kühn in 1927, the order included the Mesozoic stromatoporoids (Sphaeractiniidae), the heterastridiids (a group of obscure spherical Mesozoic fossils commonly regarded as hydrozoans), and the spongiomorphs. Kühn placed all of these in the class Hydrozoa. The discovery of spicules (spikelike supporting structures) in some genera of the sphaeractinids has allowed some genera formerly considered Mesozoic stromatoporoids to be classified in the Porifera as representatives of the class Demospongiae and the subclasses Ceractinomorpha and Tetractinomorpha. This discovery has opened the probability that all the sphaeractinids will eventually be referable to living sponge families and orders, if traces of spicules can be found in them. Both Mesozoic and Paleozoic stromatoporoids are now considered to be poriferans; the Paleozoic representatives are best considered a class of the phylum separated from the Mesozoic forms by time, lack of spicules, and microstructure. Those genera of the Mesozoic group that, at present, cannot be assigned to a living poriferan taxon owing to the lack of (or our failure as yet to discover) spicules are a disparate orphan group that can best be informally referred to as sphaeractinids or Mesozoic stromatoporoids.
Industry:Science
An extinct group of mainly Lower Cambrian marine sponges which, although lacking spicules, possessed an intricate, highly porous skeleton of calcite. It was probably a monophyletic group; that is, all representatives were derived from a single ancestor. The position of the Archaeocyatha within the Porifera is uncertain, but they were probably most closely related to the class Demospongiae. Their fossil record is well known, as archaeocyaths represent the first large skeletal animals to have been associated with reefs; they were widespread in the shallow, warm waters that surrounded the many continents that occupied tropical latitudes during the Cambrian.
Industry:Science
An extinct order in the class Mammalia, subclass Allotheria, comprising a major group of early mammals, ranging from Late Jurassic to Late Eocene (about 155 to 35 million years ago). The group is best known from North America, Mongolia, and Europe. Most multituberculates were mouselike in size, although the North American Paleocene <i>Taeniolabis</i> was larger, probably closer to the woodchuck (<i>Marmota monax</i>) in its proportions. Multituberculates appear primarily to have been terrestrial creatures, but some were probably arboreal (living in trees) and others fossorial (adapted for digging). The Eocene decline and extinction of multituberculates may reflect competition from small placental mammals, especially primates and rodents.
Industry:Science
