ISSN 0031-0301, Paleontological Journal, 2008, Vol. 42, No. 8, pp. 830–858. © Pleiades Publishing, Ltd., 2008. Biogeography of the Recent Brachiopods O. N. Zezina Shirshov Institute of Oceanology, Russian Academy of Sciences, Nakhimovskii pr. 36, Moscow, 117997 Russia e-mail: [email protected] Received July 3, 2007 Abstract—The vertical, latitudinal, and circumcontinental zonality of the distribution of the species, genera, and families of recent brachiopods is considered. The distortions of the latitudinal and meridional symmetry of the biogeographic structure of the ocean are analyzed in view of the patterns of the global circulation of the surface and intermediate waters. Thus ancient faunas may be reconstructed based on data on the structural char- acteristics of the taxocene of recent brachiopods. The features of the paedomorphic evolution of brachiopods from the different families in extreme habitats (interstitial, underwater caverns, submarine rises, abyssal depths, hydrothermal areas, and margins of habitats) are discussed. The biogeographic structure of bottom dwellers is shown to simplify with depth as well as with simplification of the hydrological structure of the ocean. The important role of the bathyal oceanic zone (slopes of continents, islands, submarine mountains, ridges, and rises) in the preservation of faunal relicts is shown. The historical change from brachiopods to bivalves that occurred from the Paleozoic to the Mesozoic and Cenozoic is shown to have resulted not from competitive exclusion, but from complex and global changes in the plankton composition, which were unfavorable for artic- ulate brachiopods, which had already developed specialized feeding habits, feeding on food that led to the pro- duction of almost no metabolic waste products; they had even partly lost their alimentary canal. The develop- ment of shelly plankton and, especially, of diatoms hampered the post-Paleozoic revival of large assemblages of articulate brachiopods in shallow-water habitats. The unfilled ecological niches were colonized by bivalves, which were widely adapted to feeding on live phyto- and zooplankton. Recent articulate brachiopods, which are adapted to feeding on the products of decay of dead plankton, form a belt of densely populated settlements of the organic biofilter outside the photic zone on the seaward edge of shelves and on the upper parts of the slopes of continents, islands, and submarine rises throughout the world. DOI: 10.1134/S0031030108080078 INTRODUCTION study of the large collection of the Shirshov Institute of Oceanology, Russian Academy of Sciences. This col- Much progress has been achieved in the last four decades in biogeography, a science dealing with the lection was formed during the expeditions of the irregular distribution of life on our planet. The same research vessels Vityaz, Akademik Kurchatov, Dmitrii concerns biooceanology. The seas and oceans now Mendeleev, Professor Shtokman, and Akademik occupy twice as much area on the Earth as the land. At Mstislav Keldysh. The manned submersibles Paisis and the end of the 20th and beginning of the 21st century, Mir were also used. Some material was collected dur- people study the seas and oceans in order to find new ing scientific exploration expeditions on the ships of the sources of seafood, as a source of protein for the rapidly Russian Federal Research Institute of Fisheries and growing human population. Marine biogeography, Oceanography (VNIRO), Pacific Fisheries Research which is useful in the human economy, also became Center (TINRO), Atlantic Research Institute of Marine theoretically useful as it allows the reconstruction of Fisheries and Oceanography (AtlantNIRO), in the spe- the history of the development of ancient marine faunas cial cruises of the Zoological Institute, Russian Acad- based on the actualistic approach. Some new concepts emy of Sciences, and also during incidental collecting of marine biogeography were discussed in the recent on geologically oriented cruises. The author also exam- literature. In the present paper we shall consider those ined collections gathered during the expeditions on the concepts which are important for paleobiology, and Danish research vessel Galathea, the American especially for the sections connected with the study of research vessels Atlantis, Chain, and Panulirus, inter- brachiopods. national expeditions of the German research vessel Brachiopods are marine invertebrates that are repre- Polarstern, and also in the course of the French projects sented in the recent seas and oceans by 370 species, BENTHEDI and NORFOLK-2. The results of the treat- 116 genera, and 26 families. Since the late 1960s they ment of the materials were published in the Trudy Insti- were especially carefully studied in detail in the context tuta Okeanologii, other journals, and monographs. of modern zoology and biogeography based on the Twenty-six new species, 5 subspecies, 9 genera, 1 sub- 830 BIOGEOGRAPHY OF THE RECENT BRACHIOPODS 831 family, and 2 families were described based on the orig- Number of species inal data. The taxonomic composition of recent brachi- 50 100 opods, their distribution, and dependence of character- 0 istic features of the recent animals on the habitat conditions were specified and clarified based on the treatment of the above-mentioned collections and sum- 1 marizing of all available literature data. 2 Here we give an account of the generalized results on the determination of both geographical and vertical 500 3 distributions of species, genera, and families and con- sider peculiarities of the symmetry of the latitudinal A and altitudinal faunal belts distinguished based on the distribution of modern taxa. The distortions of the lati- tudinal and meridional symmetry in the biogeographic structure of the ocean are considered in connection with Depth, m the patterns of global circulation of the surface and 1000 intermediate waters. The peculiarities of brachiopod evolution in optimal and extreme habitat conditions are 25 50 analyzed. The possibility of the paleoreconstruction of 0 ancient faunas accounting for the structural and func- 100 B tional characteristics of the recent brachiopod taxocene is discussed. 200 300 C The historical change from brachiopods to bivalves D that occurred from the Paleozoic to the Mesozoic and 400 Cenozoic is considered to have resulted not from com- petitive exclusion, but from complex and global Fig. 1. Change in the number of brachiopod species with changes in the plankton composition, which were unfa- depth in the upper horizons of the benthic zone. Designa- vorable for articulate brachiopods, which had already tions: (A) total number of species: (1) number of species developed specialized feeding habits, feeding on food within each 10 m interval of depth; (2) number of species that do not go deeper than 700 m; (3) number of species that that led to the production of almost no metabolic waste go deeper than 700 m; (B), (C), and (D): distribution of sub- products; they had even partly lost their alimentary littoral species: (B) in the littoral and phytal zones; canal. The development of shelly plankton and, earlier, (C) within the whole sublittoral zone; and (D) in the elit- of diatoms hampered the post-Paleozoic revival of large toral zone. assemblages of articulate brachiopods in shallow-water habitats. The unfilled ecological niches were colonized by bivalves, which were widely adapted to feeding on The range of the vertical distribution of species var- live phyto- and zooplankton. Recent articulate brachio- ies from a few meters to three or five kilometers. The pods, which are adapted to feeding on the products of depth ranges are known not for all species and for many decay of dead plankton, form a belt of relatively deep- of them only solitary indications of depth were pointed sea organic biofilter outside the photic zone on the sea- out. Thus the vertical range of distribution has been ward edge of shelves and on the upper parts of the reliably established for only 200 species. slopes of continents, islands, and submarine rises throughout the world. The general pattern of vertical brachiopod distribu- tion (Fig. 1) shows that the number of species increases with depth from the water line, reaches its maximum VERTICAL DISTRIBUTION between depths of 100 and 150 m, and then decreases. The following points in the vertical change in the spe- Recent brachiopods inhabit all oceanic depths cies composition of brachiopods are distinguished except the deep oceanic trenches, from the tidal (lit- based on the change in the total number of species toral) zone down to ocean floor (abyss). Of inarticulate within each 50 m depth interval and the curves showing brachiopods, several lingulid and discinid species the density of the boundaries between the vertical inhabit the littoral zone, and the cosmopolitan Pelago- ranges of species (number of species that appeared and discus atlanticus reaches the maximum depth known disappeared). for any brachiopod, in the abyssal zone. Of articulate brachiopods, the North Atlantic Diestothyris frontalis (1) The maximum number of species appears and and Megerlina davidsoni from the Indian Ocean inhabit disappears in the upper horizons of the benthic zone, the littoral zone, and the cosmopolitan Abyssothyris i.e., it is here that the most intense change of fauna wyvillei was found in the abyss. occurs. PALEONTOLOGICAL JOURNAL Vol. 42 No. 8 2008 832 ZEZINA Table 1. Endemic species in the vertical zones ris cancellata and Diestothyris frontalis, are known from the upper horizon (0–10 m). Six species are Number of species % of endemics endemics of depths of 300–700 m below sea level: Cra- Zones, m total more than total more than nia patagonica, Cryptopora boettgeri, Gryphus tokio- number once met number once met nis, Lioyhyrella winteri, Campages asthenia, and Magellania sp. (Thomson, 1918). 0–300 184 154 59 51 One-third of the recent brachiopod species are 300–700 114 94 23 6 known from waters deeper than 700 m. Most of the 700–2000 58 56 10 7 61 species that were found more than once deeper than deeper than 34 27 35 18 700 m are also known from depths above 700 m.