| Mattheviidae | |
|---|---|
 | |
| Plates of Matthevia . Coin: 19 mm diameter | |
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Mollusca |
| Class: | Polyplacophora |
| Order: | † Paleoloricata |
| Family: | † Mattheviidae Walcott, 1885 |
| Genera | |
| |
Mattheviidae is an extinct taxonomic family of fossil chitons, marine polyplacophoran mollusks that are found in Cambrian-Silurian deposits. [1]
An exoskeleton is the external skeleton that supports and protects an animal's body, in contrast to the internal skeleton (endoskeleton) of, for example, a human. In usage, some of the larger kinds of exoskeletons are known as "shells". Examples of animals with exoskeletons include insects such as grasshoppers and cockroaches, and crustaceans such as crabs and lobsters, as well as the shells of certain sponges and the various groups of shelled molluscs, including those of snails, clams, tusk shells, chitons and nautilus. Some animals, such as the tortoise and turtle, have both an endoskeleton and an exoskeleton.
A sclerite is a hardened body part. In various branches of biology the term is applied to various structures, but not as a rule to vertebrate anatomical features such as bones and teeth. Instead it refers most commonly to the hardened parts of arthropod exoskeletons and the internal spicules of invertebrates such as certain sponges and soft corals. In paleontology, a scleritome is the complete set of sclerites of an organism, often all that is known from fossil invertebrates.
Chitons are marine molluscs of varying size in the class Polyplacophora, formerly known as Amphineura. About 940 extant and 430 fossil species are recognized.
Monoplacophora, meaning "bearing one plate", is a polyphyletic superclass of molluscs with a cap-like shell now living at the bottom of the deep sea. Extant representatives were not recognized as such until 1952; previously they were known only from the fossil record, and were previously thought to have become extinct over 380 million years ago.
The evolution of the molluscs is the way in which the Mollusca, one of the largest groups of invertebrate animals, evolved. This phylum includes gastropods, bivalves, scaphopods, cephalopods, and several other groups. The fossil record of mollusks is relatively complete, and they are well represented in most fossil-bearing marine strata. Very early organisms which have dubiously been compared to molluscs include Kimberella and Odontogriphus.
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.
Chiton magnificus, the liquorice sea cradle, is a Southeast Pacific species of edible chiton, a marine polyplacophoran mollusk in the family Chitonidae, the typical chitons.
Mattheva is a class of fossil mollusc, which might be better incorporated in a different class. It was erected to accommodate chiton-like organisms such as Matthevia. Phosphatic fossils have been questionably included in this class even though molluscs do not use phosphate.
Matthevia is a genus of Cambrian molluscs, perhaps related to the chitons. It consists of repeated monoplacophoran-like shells; according to one hypothesis, chitons arose when these tall shells began to overlap over the generations. The tall element of the shell was retained and forms the tips of modern chiton plates. There are distinct head, 'centre', and tail valves, which occur approximately in the ratio 1:5:1 — suggesting a seven-plated configuration.
Robustum nodum is the one species of a problematic genus of Ordovician hemithecellid mollusc proposed by Stinchcomb and Darrough in 1995. Its similarities to Matthevia were outlined by Vendrasco & Runnegar.
Hemithecella is a problematic genus of Ordovician mollusc proposed by Stinchcomb and Darrough in 1995. Hemithecella belongs to what are informally known as multiplated molluscs; it is found in the late Cambrian of the Ozarks and the Lower Ordovician of the same region as well as in Minnesota and the southern Appalachian Mountains. Hemithecella has muscle scars identical to a monoplacophoran and not the musculature of a chiton to which some authors have suggested the multiplated molluscs belong. It is therefore classified in the Mattheviidae.
The Conococheague Formation is a mapped Appalachian bedrock unit of Cambrian age, consisting primarily of limestone and dolomite. It occurs in central Maryland, southern and central Pennsylvania, the Valley and Ridge of Virginia and easternmost West Virginia.
Paradycheia is a genus of polyplacophoran known from the Upper Cambrian Eminence Dolomite, Missouri, USA.
Dycheiidae is a wastebasket taxon containing problematic polyplacophora from Upper Cambrian strata in the USA.
Allochiton is a genus of upper Cambrian chitons with a circular head valve.
The Paleoloricata are valved polyplacophora without sutural laminae or insertion plates. The "order" probably represents a paraphyletic grouping.
Chelodina is a suborder of polyplacophoran mollusc that appeared during the Cambrian and became extinct during the Cretaceous. It is known from fossils from Europe and North America.
Multiplacophora is a stem-group of chitons with a number of plates arranged in 7 rows along the body. They date to at least the Upper Cambrian, but two lower Cambrian fossils- Ocruranus and Trachyplax - may extend the range downwards.
Glaphurochiton is a genus of fossil chitons known from the Mazon Creek biota.
The orthothecids are one of the two hyolith orders.
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