Cluster analysis of Cambrian-Ordovician marine benthic communities and community-trophic analysis of Late Cretaceous shelf faunas indicate that major ecological innovations appeared in nearshore environments and then expanded outward across the shelf at the expense of older community types. This onshoreinnovation, offshore-archaic evolutionary pattern is surprising in light of the generally, higher species turnover rates of offshore clades. This pattern probably results from differential extinction rates of onshore as compared to offshore clades, or from differential origination rates of new ecological associations or evolutionary novelties in nearshore environments.

https://science.sciencemag.org/content/sci/222/4628/1123.full.pdf

Onshore-offshore patterns in the evolution of phanerozoic shelf communities.

Evolution of the freshwater ecosystem: The fossil record

A new molecular phylogeny is presented for the highly diverse, bivalve molluscan subclass Heterodonta. The study, the most comprehensive for heterodonts to date, used new sequences of 18S and 28S rRNA genes for 103 species from 49 family groups with species of Palaeoheterodonta (Trigoniidae, Margaritiferidae and Unionidae) as outgroups. Results confirm previous analyses that the Carditidae/Astartidae/Crassatellidae clade is basal to all other heterodonts including Anomalodesmata (often classified as a separate subclass or order). Thyasiroidea occupy a near basal position between the Crassatelloidea and Anomalodesmata. Lucinidae form a well-supported monophyletic group distinct from Thyasiridae and Ungulinidae. The Solenoidea and Hiatelloidea link as sister groups distant from the Tellinoidea and Myoidea, respectively, where they had been previously associated. The position of the Gastrochaenidae is unstable but does not group with myoidean taxa. Species of four families of Galeommatoidea form a clade that also includes Sportellidae of the Cyamioidea. The Cardioidea and Tellinoidea form highly supported, long branched, individual clades but group as sister taxa. A major clade including Veneroidea, Mactroidea, Myoidea and other families is given the unranked name Neoheterodontei. There is no support for a separate order Myoida (Myoidea and Pholadoidea). Dreissenidae group within the clade including Myidae, Corbulidae, Pholadidae and Teredinidae. The Corbiculoidea is confirmed as polyphyletic with the Sphaeriidae and Corbiculidae forming separate clades within the Neoheterodontei; Corbiculidae grouping with the Glauconomidae. Hemidonacidae are unrelated to the Cardiidae, as previously proposed, but nest within the Neoheterodontei. The Gaimardiidae group near to the Ungulinidae and not with Cyamioidea where most recently classified. The family Ungulinidae, previously classified in the Lucinoidea, forms a well-supported clade within the Neoheterodontei and is elevated to superfamily rank — Ungulinoidea. The monophyletic status of Glossoidea, Arcticoidea and Veneroidea is unconfirmed. A brief review of the fossil record of the heterodonts indicates that the basal clades of Crassatelloidea, Anomalodesmata and Lucinoidea diverged very early in the Lower Palaeozoic. Other groups such as the Hiatelloidea, Solenoidea, Gastrochaenidae probably were of late Palaeozoic origins. The Cardioidea and Tellinoidea originated in the Triassic while major groups of Neoheterodontei radiated in the Late Mesozoic. The phylogenetic position of the Thyasiroidea and Galeommatoidea suggests a longer fossil history than has so far been recognized.

A molecular phylogeny of heterodont bivalves (Mollusca: Bivalvia: Heterodonta): new analyses of 18S and 28S rRNA genes

ABSTRACT Some 1,048 names at the rank of subtribe, tribe, subfamily, family and superfamily have been proposed for Recent and fossil bivalves. All names are listed in a nomenclator giving full bibliographical reference, date of publication, type genus, and their nomenclatural availability and validity under the International Code of Zoological Nomenclature. Another 274 names, established for categories above the family-group are listed separately. A working classification attempts to group all bivalve family-group names into a single system based on current hypotheses of relations and synonymies. At several rank levels, the groups are given in alphabetical rather than some assumed phylogenetic arrangement, reflecting current uncertainties and conflicting results from anatomical, molecular, and fossil data. Altogether, the classification recognizes as valid a total of 324 families, of which 214 are known exclusively as fossils and 110 occur in the Recent with or without a fossil record.

Nomenclator of bivalve families; with a classification of bivalve families by R. Bieler, J. G. Carter & E. V. Coan.

Some 1,048 names at the rank of subtribe, tribe, subfamily, family and superfamily have been proposed for Recent and fossil bivalves. All names are listed in a nomenclator giving full bibliographical reference, date of publication, type genus, and their nomenclatural availability and validity under the International Code of Zoological Nomenclature. Another 274 names, established for categories above the family-group are listed separately. A working classification attempts to group all bivalve family-group names into a single system based on current hypotheses of relations and synonymies. At several rank levels, the groups are given in alphabetical rather than some assumed phylogenetic arrangement, reflecting current uncertainties and conflicting results from anatomical, molecular, and fossil data. Altogether, the classification recognizes as valid a total of 324 families, of which 214 are known exclusively as fossils and 110 occur in the Recent with or without a fossil record.

https://bioone.org/journals/Malacologia/volume-52/issue-2/040.052.0201/Nomenclator-of-Bivalve-Families-with-a-Classification-of-Bivalve-Families/10.4002/040.052.0201.pdf

Nomenclator of Bivalve Families With a Classification of Bivalve Families

The history of the Heteroconchia is traced from the earliest Ordovician, where they occur in shallow, marine sand and silt and inshore mud facies throughout the Palaeozoic, where in contrast to Mesozoic and more recent times they are numerically less important than the Anomalodesmata in the number of species present in the infauna. Evidence for the relationship of the heteroconch superfamilies from Cycloconchacea to Chamacea is discussed and a number of modifications to their existing classification made.

The infaunal descendants of the Cycloconchidae: an outline of the evolutionary history and taxonomy of the Heteroconchia, superfamilies Cycloconchacea to Chamacea

Two classes of Mollusca have successfully emerged from the sea: the Bivalvia to fresh waters but the Gastropoda, in addition to invading the fresh water habitat, have also become fully air-breathing and live on the land. There is today a complete range from those taxa that are in every respect fully marine to those that are completely independent of the sea. The possible pathways from the sea to these environments are by surviving reduced or varying salinities, which it might be assumed occur in intertidal or estuarine conditions, or by surviving periodic and increasing exposure in air, again a condition of the intertidal environment. The prerequisite for emergence from the sea must have been the presence of food. In the initial emergence this could have been provided by detritus derived from the sea and deposited along a feature such as a storm beach. Such an environment is probably important for some Ellobiidae today. To spread onto the land and into the fresh water Mollusca, as other essentially grazing or suspension feeding animals, were presumably preceded by Bacteria or plants, or both. The initial modifications to metabolic and reproductive processes, outlined by Little (1983), may have taken place high in the littoral zone, supported by detritus and, as in the Ellobiidae, remaining dependent on the sea during larval life. The expansion and radiation of the Mollusca that has followed may have been related to the increase in habitats made available by the plants.

http://www.jstor.org/stable/pdfplus/2396364.pdf

N. J. Morris

Papers

The infaunal descendants of the Cycloconchidae: an outline of the evolutionary history and taxonomy of the Heteroconchia, superfamilies Cycloconchacea to Chamacea

Other Non-Marine Invertebrates