Contributions to Zoology, 69 (4) 213-222 (2000) SPB Academic Publishing bv, The Hague Crustacean biodiversity through the marine fossil record J.+John Sepkoski+Jr. (†) Department of the Geophysical Sciences, University of Chicago, Chicago, IL 60637, USA Keywords: Crustacean biodiversity, marine fossil record, extinction rates, Ostracoda, Malacostraca, Cirripedia Abstract Introduction 2,600 ofmarine crustaceans have been Approximately genera Arthropods constitute an important component of recognized in the fossil record, and crustaceans constitute the the fossil record, just as they constitute a major major componentof marine arthropod diversity from the mid- part of the living fauna both on land and in the Paleozoic to the Recent. Despite problems of sporadic fossil oceans. In the marine realm, approximately 16 per- preservation and/or taxonomic ambiguity, some general state- cent of all described of fossil animals ments can be made about the history of crustacean biodiversity, genera are based taxonomic data bases. Ostracodes the first on global were arthropods; on land, fossil arthropods at the family major to radiate,attaining high diversity during the Ordo- level group have proportions that are even higher (Laban- vician Period with other members ofthe Paleozoic evolutionary deira and Sepkoski, 1993). Among fossil marine of extinction and extinctions fauna;rates responses to mass were a constituent is the Crustacea, also similar those of within the Paleozoic fauna. arthropods, major to groups Malacostracans and and barnacles (cirripedes), the two other crusta- including predominantly ostracodes, cirripedes, cean with had minor malacostracans. with groups important fossil records, diversity Together minor groups, they throughout the Paleozoic Era. Both diversifi- groups experienced include 45 percent of described arthropod fossil cation from the mid-Mesozoic to Recent with lower extinction genera from marine strata, exceeded only by the rates, as characteristic members of the Modern evolutionary diverse and rapidly trilobites of the Pa- fauna. evolving leozoic Era. In this contribution, 1 examine these numbers for crustaceans as relate to time Contents they geologic and therefore to and fossil evolutionary history pres- ervation. or taxonomic of fos- Introduction 213 Diversity, richness, sils in taxonomic databases Caveats 214 provides a variety of 214 Biostratigraphy quantitative information. The simplest is just our Ostracode 214 taxonomy knowledge of the fossil record: The numberof fossil Malacostracan preservation 214 taxa described can be compared to other measures Crustacean diversity in the fossil record 214 modern of importance, such as diversity or fossil Relative to other arthropods 214 to deduce the of knowl- of in the fossil record 215 abundance, quality our Diversity major groups Ostracodes 216 edge of the fossil record. For example, copepods Barnacles , 217 are the most abundant arthropods in modern ma- Malacostracans 217 but rine pelagic ecosystems, their fossil record is Comparison to Phanerozoic diversification 219 But with minimal. even varying quality of the fossil Summary 220 statements can be made Acknowledgements 220 record, qualitative about References 220 evolutionary history, which is the usual goal of Addendum 221 studies of fossil diversity. The data here based analyzed are upon a com- of of pilation geologic ranges all marine animal that I have described genera previously (e.g., Sepkoski, 1996, 1997). The compilation has in- Downloaded from Brill.com10/08/2021 03:03:48AM via free access - and 214 J.J. Sepkoski Crustacean biodiversity fossils standard such the as zonal fossils of the volved summarizing sources, as occasionally through parts review- Mesozoic and Cenozoic. crustaceans as Treatise on Invertebrate Paleontology, and However, have ing primary literature to increase stratigraphic reso- a whole been viewed as having a sporadic in fossil record and therefore oflimited use lution of first and last appearances and to add newly telling taxonomic level of time. there has been limited for described fossil genera. The Thus, impetus is between detailed search and the genus employed as a compromise study. the immense, idiosyncratic, and historically com- plicated taxonomic descriptions of fossil species Ostracode taxonomy and the limited numbers of crustacean families described from the fossil record (therefore subject in In- The volume on ostracodes the Treatise on taxonomic lev- to small-sample variation). At the vertebrate Paleontology (Benson, 1961) was a major els of both genus and family, some might object breakthrough for the understanding of the system- that supra-specific taxa are arbitrary constructs and atics of these fossils. Since that publication, the not reflect How- may any evolutionary patterns. number of described ostracode genera has more and model ever, empirical (Sepkoski et ah, 1981) is difficult this world- than doubled. It to survey (Sepkoski and Kendrick, 1993) studies have indi- wide literature and compile all revisions in strati- traditional and families reflect cated that genera graphic ranges ofolder ostracode genera. Therefore, species-level patterns of diversity quite well (see data ostracodes’ ranges in any synoptic set, despite also Gaston and Williams, 1993). In fact, when large diversity among fossil crustaceans (see below), the potential preservation of animals is quite low, minimum will be largely ranges. taxa as in the case of many crustaceans, higher reflect of may better patterns underlying species than fossil themselves (Sepkoski diversity speices Malacostracan preservation and Kendrick, 1993). I few caveats about the Below, present a more Many malacostracans and other crustaceans have data. I then illustrate summaries of the history of nonmineralized to weakly mineralizedexoskclctons. for the major fossil classes of marine genus diversity The result is a sporadic fossil record. The most crustaceans and these to the history of compare abundantcrustaceans in the oceans today, the cope- the three evolutionary faunas of the Phan- great pods, have virtually no fossil record, and marine erozoic. that forms are inferred largely from cysts parasitic copepods produce in echinoderms. Among mala- costracans, the fossil record is somewhat better, Caveats especially with the Mesozoic evolution of brach- with calcified exoskeleton. Still their yurans a In attempting to interpret crustacean diversity known history, like the history of other malacos- through geologic time, it is clear that both the is sensitive the tracan groups, very to geologic quantity of taxonomic attention and the quality of - distribution of exceptional fossil deposits Lager- preservation influence patterns seen in taxonomic statten. But if these weakly sclerotized taxa appear databases. Neitherattention nor quality is ideal for then more and more frequently in Lagerstatten, we in world crustaceans, but even an imperfect major can infer that they were becoming more important evolutionary trends in diversity are potentially in the biotic environment time. and through perceptible. Below, I discuss three problems their resolutions: Crustacean diversity in the fossil record Biostratigraphy Relative to other arthropods Crustaceans have not been used as index fossils fossil of through most of the Phanerozoic geologic record. Of the approximately 5,800 genera ma- Ostracodes are an exception and have been used rine arthropods currently recognized, about 2,600 Downloaded from Brill.com10/08/2021 03:03:48AM via free access Contributions to Zoology, 69 (4) - 2000 215 I. The described of all the Phanerozoic. Crustacean is the fig. genus diversity marinearthropods through genus diversity illustratedby lower Dots indicate data “Ma” is millions of before Abbreviations for field. points. years present. geologic periods are as follows: C=Cambrian; 0=Ordovician; S=Silurian; D=Devonian; C=Carboniferous;P=Permian; T=Triassic; J=Jurassic; K=Cretaceous; T=Tertiary. are crustaceans. The majority of the remaining fossil tacean diversification has not been homogeneous, the genera are trilobites, which did not survive as described below. such the Paleozoic Era. Other groups, as extant to have nierostomes and pycnogonids, appear never been diverse for the the (except perhaps eurypterids). Diversity of major crustacean groups in fossil This pattern is illustrated in Fig. 1, which exhibits record the total described diversity of marine arthropods through the Phanerozoic with crustacean diversity Fig. 2 illustrates the Phanerozoic history of the three field. crus- segregated into a separate As evident, major groups of fossil crustaceans: ostracodes, taceans have been important components of ma- barnacles (cirripedes), and malacostracans. Total rine biodiversity since the Ordovician Period and diversity in this graph differs somewhat from that compose virtually the entire fossil arthropod fauna' in Fig. 1 because two adjustments have been made the Mesozoic and Cenozoic Eras when to minimize biases in the fossil data. through they First, genera attain maximum observed diversity. However, crus- confined to single stratigraphic intervals havebeen Downloaded from Brill.com10/08/2021 03:03:48AM via free access 216 Sepkoski - Crustacean biodiversity andfossils Marine the Phanerozoic with accommodate described in the Fig. 2. crustacean genus diversity through manipulations to biases, as text. The three fossil of indicate cumulative Abbreviations the in major groups crustaceans are by fields. arc same as Fig. I. eliminated in order