In many marine gastropods other than the opisthobranchs , there are separate sexes; most land gastropods, however, are hermaphrodites. Courtship is a part of the behavior of mating gastropods with some pulmonate families of land snails creating and utilizing love darts , the throwing of which have been identified as a form of sexual selection. The diet of gastropods differs according to the group considered. Marine gastropods include some that are herbivores , detritus feeders, predatory carnivores , scavengers , parasites , and also a few ciliary feeders, in which the radula is reduced or absent.
Land-dwelling species can chew up leaves, bark, fruit and decomposing animals while marine species can scrape algae off the rocks on the sea floor. In some species that have evolved into endoparasites, such as the eulimid Thyonicola doglieli , many of the standard gastropod features are strongly reduced or absent. A few sea slugs are herbivores and some are carnivores. The carnivorous habit is due to specialisation.
Many gastropods have distinct dietary preferences and regularly occur in close association with their food species. Some predatory carnivorous gastropods include, for example: Cone shells , Testacella , Daudebardia , Ghost slug and others. Gastropods exhibit an important degree of variation in mitochondrial gene organization when compared to other animals. The first gastropods were exclusively marine, with the earliest representatives of the group appearing in the Late Cambrian Chippewaella , Strepsodiscus ,  though their only gastropod character is a coiled shell, so they could lie in the stem lineage, if they are gastropods at all.
As such, it's not until the Ordovician that the first crown-group members arise.
Fossil Behavior Compendium | Taylor & Francis Group
Commonly, fossil gastropods from the rocks of the early Palaeozoic era are too poorly preserved for accurate identification. Still, the Silurian genus Poleumita contains fifteen identified species. Fossil gastropods were less common during the Palaeozoic era than bivalves. Most of the gastropods of the Palaeozoic era belong to primitive groups, a few of which still survive. By the Carboniferous period many of the shapes seen in living gastropods can be matched in the fossil record, but despite these similarities in appearance the majority of these older forms are not directly related to living forms.
It was during the Mesozoic era that the ancestors of many of the living gastropods evolved. One of the earliest known terrestrial land-dwelling gastropods is Maturipupa , which is found in the Coal Measures of the Carboniferous period in Europe, but relatives of the modern land snails are rare before the Cretaceous period, when the familiar Helix first appeared. In rocks of the Mesozoic era, gastropods are slightly more common as fossils; their shells are often well preserved.
Their fossils occur in ancient beds deposited in both freshwater and marine environments. The " Purbeck Marble " of the Jurassic period and the " Sussex Marble " of the early Cretaceous period, which both occur in southern England, are limestones containing the tightly packed remains of the pond snail Viviparus. Rocks of the Cenozoic era yield very large numbers of gastropod fossils, many of these fossils being closely related to modern living forms.
The diversity of the gastropods increased markedly at the beginning of this era, along with that of the bivalves. Certain trail-like markings preserved in ancient sedimentary rocks are thought to have been made by gastropods crawling over the soft mud and sand. Although these trace fossils are of debatable origin, some of them do resemble the trails made by living gastropods today. Gastropod fossils may sometimes be confused with ammonites or other shelled cephalopods.
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An example of this is Bellerophon from the limestones of the Carboniferous period in Europe, the shell of which is planispirally coiled and can be mistaken for the shell of a cephalopod. Gastropods are one of the groups that record the changes in fauna caused by the advance and retreat of the Ice Sheets during the Pleistocene epoch. A cladogram showing the phylogenic relationships of Gastropoda with example species: .
Cocculiniformia , Neomphalina and Lower Heterobranchia are not included in the above cladogram. Since Darwin , biological taxonomy has attempted to reflect the phylogeny of organisms, i. The classifications used in taxonomy attempt to represent the precise interrelatedness of the various taxa. However, the taxonomy of the Gastropoda is constantly being revised and so the versions shown in various texts can differ in major ways.
In the older classification of the gastropods, there were four subclasses: . The taxonomy of the Gastropoda is still under revision, and more and more of the old taxonomy is being abandoned, as the results of DNA studies slowly become clearer. Nevertheless, a few of the older terms such as "opisthobranch" and "prosobranch" are still sometimes used in a descriptive way. New insights based on DNA sequencing of gastropods have produced some revolutionary new taxonomic insights. In the case of the Gastropoda, the taxonomy is now gradually being rewritten to embody strictly monophyletic groups only one lineage of gastropods in each group.
Integrating new findings into a working taxonomy remain challenging. Consistent ranks within the taxonomy at the level of subclass, superorder, order, and suborder have already been abandoned as unworkable. Ongoing revisions of the higher taxonomic levels are expected in the near future. Convergent evolution , which appears to exist at especially high frequency in gastropods, may account for the observed differences between the older phylogenies, which were based on morphological data, and more recent gene-sequencing studies.
In the past, the taxonomy of gastropods was largely based on phenetic morphological characters of the taxa. This has made the taxonomical ranks and their hierarchy controversial. The debate about these issues is not likely to end soon. In the Bouchet, Rocroi et al. Whenever monophyly has not been tested, or is known to be paraphyletic or polyphyletic, the term "group" or "informal group" has been used. The classification of families into subfamilies is often not well resolved, and should be regarded as the best possible hypothesis.
In , Brian Simison and David R. Lindberg showed possible diphyletic origins of the Gastropoda based on mitochondrial gene order and amino acid sequence analyses of complete genes.
Debris-carrying camouflage among diverse lineages of Cretaceous insects
This article incorporates CC-BY From Wikipedia, the free encyclopedia. Main article: Gastropod shell. Main articles: Sensory organs of gastropods and Nervous system of gastropods. Main articles: Digestive system of gastropods and Radula. Main article: Circulatory system of gastropods.
Main article: Excretory system of gastropods. Main article: Reproductive system of gastropods. See also: Mating of gastropods. In Ponder, W.
Phylogeny and evolution of the Mollusca. University of California Press. Classification and nomenclator of gastropod families. Malacologia: International Journal of Malacology, 47 ConchBooks: Hackenheim, Germany. Fossil Plants and Spores.
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Plate legends are located in the color folder. Review quote "In this complete and thorough update of Arthur Boucot's seminal work, Evolutionary Paleobiology of Behavior and Coevolution, Boucot is joined by George Poinar, who provides additional expertise and knowledge on protozoans and bacteria as applied to disease.
It is neither a textbook with lucid explanations of complex concepts, nor a symposium volume of detailed case studies, nor an engaging narrative of intrepid scientific adventures. Rather, the book is filled with a plethora of anecdotes and data that provide a springboard into further explorations of the vast literature on fossil behavior.
This work takes paleobiology from a record of the succession of fossil taxa through time certainly important to answering questions about evolution to a much more exciting representation of changes in whole communities and ecosystems. This book will contribute greatly to our perspectives on how integrated communities and ecosystems have developed through time.
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