This study uses a comprehensive, revised, and updated global bivalve dataset combining information from two major databases available to study temporal trends in Phanerozoic bivalve richness: the Sepkoski Compendium and the Paleobiology Database. This compilation results in greater taxonomic and stratigraphic coverage than possible with either of the two databases alone. However, there are challenges in directly comparing these two sources due to differences in their taxonomic designations and stratigraphic range information. Moreover, both of these datasets are fraught with a number of taxonomic errors, which can significantly bias the overall richness estimate. Additionally, a substantial number of taxonomic corrections were made before a new Phanerozoic bivalve richness curve was produced. The new generic taxonomic curve is comparable with the trajectory of the Sepkoski's modern fauna and shows rapid and substantial diversification through the Ordovician, followed by a Paleozoic plateau, a Mesozoic high, and Cenozoic diversification after a small reduction in richness associated with the K/Pg extinction. The steep Cenozoic rise documented in the raw richness curve derived from the new dataset is likely real, and reflects the overall robustness and completeness of the bivalve fossil record. © 2015 The Paleontological Society.

SUBHRONIL MONDAL

Geology

University of Calcutta (informally known as Calcutta University or CU) is a collegiate public state university located in Kolkata, West Bengal, India.&nbsp;Within India it is recognized as a &quot;Five-Star University&quot; and accredited &quot;A&quot; Grade by National Assessment and Accreditation Council.

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The University of Calcutta has secured the Fifth position among the Universities of India in the prestigious &quot;Indian University Ranking 2019&quot; list, released by the NIRF of the Ministry of Human Resource Development, Government of India.

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It was established on 24 January 1857, and was one of the first institutions in Asia to be established as a multidisciplinary and Western-style university. Its alumni and faculty include several heads of state, heads of government, social reformers, prominent artists, only academy award winner and Dirac medal winner in India, many Fellows of the Royal Society and five Nobel laureates as of 2019 which is highest in South Asia.

University Of Calcutta

Paleobiology

Ecologic diversity within marine invertebrates has typically been reconstructed by examining three components: mobility, feeding habit, and tiering. Based on various combinations of these three features, a wide range of hypothetical ecospaces or "cubes" (the agglomeration of which forms a "Bambachian cube") can be delineated. Given the range of constraints on a specific Glade's morphologic diversity, however, only a relatively limited proportion of these possible combinations are actualized. Previous studies investigating Phanerozoic trends have documented the general pattern of ecologic diversity measured as the total number of filled cubes of all metazoan groups which displays a major increase in the range of ecospace inhabited. However, detailed, Glade-specific studies are limited. In this Phanerozoic-level study on the Class Bivalvia, a group with a very robust and virtually unparalleled fossil record, the Glade's ecologic diversity is reconstructed based on a set of newly compiled taxonomic and ecologic databases that were initially derived from a combination of the Sepkoski Compendium and the Paleobiology Database. These data have been binned into 94 intervals, from the Fortunian up to the Piacenzian. The ecologic position of each genus was determined relative to the 140 ecologic cubes that reflect the hypothetical range of ecospace bivalves may have inhabited (i.e. fundamental cubes or ecospaces) and which are based on a substantially modified version of the earlier Bambachain cube (Bambach et al., 2007). The overall results show several features: (1) given the various morphologic constraints, bivalves have only occupied 44 of the total, hypothetically available cubes which represents the Glade's realized ecospace; (2) the most significant and dramatic phase of increase in the range of ecologic types occurred during the Ordovician; following this event, new ecospace was exploited in a much more limited fashion; (3) most changes in ecospace utilization involved increased packing within a relatively limited suite of cubes; and (4) mass extinctions had a very limited impact on ecospace utilization despite their impacts on bivalve taxonomic richness; only the K-Pg extinction had significant effect on the overall ecologic diversity of bivalves, largely reflecting the demise of a novel reef-building group, the rudistids. (C) 2015 Elsevier B.V. All rights reserved.

Journal	Paleobiology
Publisher	Paleontological Society
ISSN	0094-8373
Open Access	No