| Trimeroceratidae Temporal range: | |
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| Inversoceras perversum, Barrande from Prague Zadní Kopanina (Czech Republic) at the National Museum (Prague) | |
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| Family: | Trimeroceratidae Hyatt and Zittel 1900 |
Trimeroceratidae is a family of molluscs in the order Oncocerida. These molluscs were fast-moving nektobenthic carnivores. They lived in the Silurian period.
Species have been found in Silurian-era strata of Canada (Québec), China, Czechia, Italy, Russia, Sweden, and the United States (Indiana, Wisconsin).
The Ordovician is a geologic period and system, the second of six periods of the Paleozoic Era, and the second of twelve periods of the Phanerozoic Eon. The Ordovician spans 41.6 million years from the end of the Cambrian Period 485.4 Ma to the start of the Silurian Period 443.8 Ma.
The PaleozoicEra is the first of three geological eras of the Phanerozoic Eon. Beginning 538.8 million years ago (Ma), it succeeds the Neoproterozoic and ends 251.9 Ma at the start of the Mesozoic Era. The Paleozoic is subdivided into six geologic periods, Cambrian, Ordovician, Silurian, Devonian, Carboniferous and Permian. Some geological timescales divide the Paleozoic informally into early and late sub-eras: the Early Paleozoic consisting of the Cambrian, Ordovician and Silurian; the Late Paleozoic consisting of the Devonian, Carboniferous and Permian.
The Silurian is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at 443.8 million years ago (Mya), to the beginning of the Devonian Period, 419.2 Mya. The Silurian is the third and shortest period of the Paleozoic Era, and the third of twelve periods of the Phanerozoic Eon. As with other geologic periods, the rock beds that define the period's start and end are well identified, but the exact dates are uncertain by a few million years. The base of the Silurian is set at a series of major Ordovician–Silurian extinction events when up to 60% of marine genera were wiped out.
The Early Devonian is the first of three epochs comprising the Devonian period, corresponding to the Lower Devonian series. It lasted from 419.2 ± 3.2 to 393.3 ± 1.2 and began with the Lochkovian Stage 419.2 ± 3.2 to 410.8 ± 1.2, which was followed by the Pragian from 410.8 ± 3.2 to 407.6 ± 1.2 and then by the Emsian, which lasted until the Middle Devonian began, 393.3± 1.2 million years ago. During this time, the first ammonoids appeared, descending from bactritoid nautiloids. Ammonoids during this time period were simple and differed little from their nautiloid counterparts. These ammonoids belong to the order Agoniatitida, which in later epochs evolved to new ammonoid orders, for example Goniatitida and Clymeniida. This class of cephalopod molluscs would dominate the marine fauna until the beginning of the Mesozoic Era.
Cardiola is an extinct genus of saltwater clams, marine bivalve molluscs that lived from the Silurian to the Middle Devonian in Africa, Europe, and North America.
Cornulitida is an extinct order of encrusting animals from class Tentaculita, which were common around the globe in the Ordovician to Devonian oceans, and survived until the Carboniferous. Organisms that may be the oldest cornulitids have been found in Cambrian sediments of Jordan.
Heloplax is a genus of worm-like molluscs. Its soft parts are preserved in three dimensions in the Silurian Herefordshire Lagerstatte; its disarticulated valves are known from other Silurian deposits. It is very bizarre by modern standards; it bears serially repeated units, and has spines. It probably falls somewhere between the aplacophorans and polyplacophora; its valves were composed of aragonite
Cobcrephora is a genus of that resembles the Palaeoloricates, known from the Silurian of Gotland. Its interpretation as a polyplacophoran is widely challenged.
Acaenoplax is an extinct worm-shaped mollusc known from the Coalbrookdale Formation of Herefordshire, England. It lived in the Silurian period. It was a couple of centimetres long and half a centimetre wide, and comprises serially repeated units with seven or eight shells, and rings of 'spines'.
†Archinacellidae is an extinct family of paleozoic molluscs of uncertain position.
Bucaniidae is an extinct family of Paleozoic molluscs of uncertain position possibly being either gastropods or monoplacophorans in the superfamily Bellerophontoidea. The family lived from the Lower Ordovician to the Devonian and have shells in which the apertural margins tend to flare. Most genera have a slit and selenizone, others some modification of this feature.
Gotlandochiton is an extinct genus of polyplacophoran mollusc. Gotlandochiton became extinct during the Silurian period.
The Heloplacidae are a group of plated aplacophora known from Silurian deposits. Their best understood representative, Acaenoplax, can be taken as representative of the family; it is the only genus for which soft part anatomy is known.
Holopea is an extinct genus of fossil sea snails, Paleozoic gastropod mollusks in the family Holopeidae.
Panenka is a genus of fossil saltwater clams, marine bivalve molluscs in the family Praecardiidae. Like most bivalves, these molluscs were suspension feeders. They lived in the Devonian Period.
Kulindroplax perissokomos is a Silurian mollusk, known from a single fossil from the Coalbrookdale Formation fauna of England. It lived during the Homerian Age. It is considered a basal aplacophoran. Unlike all modern aplacophorans, which are shell-less, Kulindroplax has a chiton-like shell, and it is considered a transitional fossil in the evolution of molluscs.
Paleontology in Indiana refers to paleontological research occurring within or conducted by people from the U.S. state of Indiana. Indiana's fossil record stretches back to the Precambrian, when the state was inhabited by microbes. More complex organisms came to inhabit the state during the early Paleozoic era. At that time the state was covered by a warm shallow sea that would come to be inhabited by creatures like brachiopods, bryozoans, cephalopods, crinoids, and trilobites. During the Silurian period the state was home to significant reef systems. Indiana became a more terrestrial environment during the Carboniferous, as an expansive river system formed richly vegetated deltas where amphibians lived. There is a gap in the local rock record from the Permian through the Mesozoic. Likewise, little is known about the early to middle Cenozoic era. During the Ice Age however, the state was subject to glacial activity, and home to creatures like short-faced bears, camels, mammoths, and mastodons. After humans came to inhabit the state, Native Americans interpreted the fossil proboscidean remains preserved near Devil's Lake as the bones of water monsters. After the advent of formal scientific investigation one paleontological survey determined that the state was home to nearly 150 different kinds of prehistoric plants.
The Laketown Dolomite is a dolomite geologic formation in Nevada and Utah. It preserves fossils dating back to the Silurian period.
Megamastax is a genus of lobe-finned fish which lived during the late Silurian period, about 423 million years ago, in China. Before the discovery of Megamastax, it was thought that jawed vertebrates (gnathostomes) were limited in size and variation before the Devonian period. Megamastax is known only from jaw bones and it is estimated that it reached about 1 metre long.
Phragmolites is an extinct genus of molluscs in the family Bucaniidae, paleozoic molluscs of uncertain position possibly being either Gastropods or Monoplacophorans in the superfamily Bellerophontoidea.
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