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Maquetación 1 ISSN (print): 1698-6180. ISSN (online): 1886-7995 www.ucm.es /info/estratig/journal.htm Journal of Iberian Geology 33 (2) 2007: 173-190 A contribution to knowledge of the development of marine life during the Permian and Triassic through the analysis of life histories of genera Contribución al conocimiento del desarrollo de la vida marina en el Pérmico y Triásico a través del análisis de la duración en el tiempo de los géneros Salvador Reguant Catedrático Emérito de Estratigrafía, Facultad de Geologia, Universidad de Barcelona, 08028 Barcelona, Spain [email protected] Received: 12/01/06 / Accepted: 19/06/06 Abstract Data recently published on the longevity of various marine animal genera permits in-depht study of the history of marine life. The Permo-Triassic boundary, as well as the Permian and Triassic periods themselves, constitute a particularly interesting point in the history of life in the Phanerozoic, in that they straddle the most extensive extinction ever recorded.The analysis of the development of abundant genera (using classes and orders) in 13 marine animal taxa reveals that, on the one hand, all the taxa studied suffered the biggest change in their generic composition during these two periods precisely at the Permo-Triassic boundary, and, on the other hand, that certain groups display patterns during these two periods that do not conform to the overall trend. Keywords: Permian, Triassic, marine genera, life-history, diversity, extinctions Resumen El análisis de los datos que se conocen sobre la duración en el tiempo de todos los géneros marinos perminte profundizar en el conocimiento de la historia de la Vida. El límite Pérmico-Triásico y, en general, la historia de la Vida durante estos dos períodos presenta un particular interés debido a la existencia de la extinción más importante de seres vivos en el Fanerozoico. El análisis del comportamiento de los géneros en 13 grupos animales que presentan una particular abundancia ha permitido confi rmar la situación en el tiempo del extraordinario cambio conocido como extinción permo-triásica y ver las diferencias en el comportamiento que cada grupo de los considerados presentan a lo largo del Pérmico y del Triásico. Palabras clave: Conodontos, Permian, Triassic, marine genera, life-history, diversity, extinctions. 1. Introduction Studies relating to this theme refer to both event and the probable causes of this crisis in the history of life. According to Sepkoski’s (1984) classifi cation, the Likewise, the appearances, extinctions and biodiversity transition from Paleozoic to modern fauna occurs at the of living beings throughout fossiliferous periods are con- Permo-Triassic boundary, at the point of the largest mass stantly being analysed, as shown by the number of papers extinction in the history of Phanerozoic. published in specialized journals. These papers approach vol 33_2.indb 173 12/07/2007 18:57:57 174 Reguant / Journal of Iberian Geology 33 (2) 2007: 173-190 the subject from highly varying perspectives (see, for These candidates include: a possible meteorite impact example, Sepkoski, 1989; Erwin, 2000; Foote, 2003 and (Becker et al., 2004); the deterioration of atmospheric 2005; Bambach et al., 2004; Jablonski, 2005; Rohde and conditions leading to a drop in oxygen levels (Wignall Muller, 2005). The papers of Foote are based on the Sep- and Hallam, 1992; Wignall and Twitchett, 1996; Wei- koski compendium). dlich et al., 2003; Foster and Afonin, 2005); a decrease The publication of the compendium of fossil marine in primary biological productivity (Twitchett, 2001); sea- animal genera (Sepkoski, 2002), collated from the mate- level changes (Hallam and Wignall, 1999); and vulcanism rial published up to that point, has allowed us to review (Wignall, 2001; Mundil et al., 2004). the history of marine life at the end of the Paleozoic and In order to obtain a more complete view of how life beginning of the Mesozoic, a period of particular interest evolved in this period and in response to a considerable due to the aforementioned extinction and the path to re- interest surrounding the extinction, we posed the follow- covery that marine life took after the great catastrophe. ing question: what was the faunal composition of marine This paper describes this review and reveals some as- environments across the entire Permian and Triassic, not pects of interest that may contribute to understanding the just at the time immediately preceding and following the history of life in the Permian and Triassic periods. extinction? The description that follow aims to make a contribution to this knowledge and may help to explain 2. The history of Life and of the Earth in the the complexity of this event. Permo-Triassic 3. The Sepkoski compendium and how it is used here Uncovering the history of the Permian, and in some aspects, the Triassic, has historically proven more chal- Jack John Sepkoski Jr’s death in May 1999, meant that lenging than of any of the other geological periods of the the compendium of fossil marine animal genera he had Phanerozoic. been collating had to be published by his two friends, Da- The most important geologists of the nineeteenth cen- vid Jablonski and Michel Foote, of the University of Chicago. tury, for example, had obtain permission from the author- This compendium is very important, including infor- ities to be able to visit Russia and study the stratigraphic mation that Spekoski basically obtained from the vol- void that existed in the succession above the well-known umes of the Treatise on invertebrate Paleontology for in- Carboniferous. On this return to Britain, one of these ge- vertebrates, from Romer (1966) for vertebrates and from ologists, Roderick Impey Murchison, wrote to Tsar Nich- Loeblich and Tappan (1998) for foraminifera. olas I, informing him of the discoveries and that theyhad On publishing the work, his colleagues checked the named the new system the Permian, based on sedimen- material, made some correction and explained how this tary deposits with a large fossil record in the area they compendium was produced. visited near the Urals (Baars, 1992) Here, given that we only intend to analyse the history Studying the Triassic has also been complex, since the of marine animals in the Permian and Triassic, we have original outcrops of three layers found in Germany, which selected 13 varied taxa (mostly orders but also classes) give it its name – “trias” – do not provide much informa- that together represent a large proportion of the diversity tion on the history of life in this period. More complete of marine life existing during the time periods studied. information has been obtained in areas outside Germany, Erwin (1993) also adopted this approach when studied starting with the alpine area which, has given its name to teh Permian and part of the Triassic using data on the some of the stages of the system. existence of particular families found in previously pub- Despite these diffi culties, these periods have been the lished catalogues. subject of numerous papers, thanks to interest in the Per- The large number of studies, mentioned in the introduc- mo-Triassic mass extinction. These papers have either tion, which were published before the compendium itself described the size of the extinction and diversity recovery (though some of their authors had access to unpublished process, or discussed possible causes of the catastrophe. data that was later used in the compendium), has allowed Two authors have made very complete descriptions us to analyse general aspects, not limited to the periods of this extinction: P. Wignall and D. H. Erwin (Wignall, considered here, of the appearance and extinction of gen- 1992; Erwin, 1994, 1996a, 1996b and 2006). They have era, and biodiversity throughout the fossiliferous periods. been able to determine a single cause, as evidence that Our contribution aims to complete the vision of certain points towards various candidates has been found in the aspects of the history of marine life that have not been geological record. specifi cally dealt with previously. vol 33_2.indb 174 12/07/2007 18:57:57 Reguant / Journal of Iberian Geology 33 (2) 2007: 173-190 175 Ord. AXINELLIDA Epoch Age dt (in Ma) Ord. TABULOSPONGIDA Ord. (uncertain) Norian 16.9 LATE TRIASSIC Cl. CALCAREA (Ph. PORIFERA) Carnian 11.5 Ord. HETERACTINIDA Ord. PHARETRONIDA Ladinian 9 MIDDLE TRIASSIC Ord. PERMOSPHINCTA Anisian 8 Ord. SPHAEROCOELIDA Ord. (uncertain) Olenekian 4.7 EARLY TRIASSIC Ord. ARCHAEOGASTROPODA (Cl. GASTROPODA) Induan 1.3 Ord. NEOTAENIOGLOSSA (Cl. GASTROPODA) Ord. NAUTILIDA (Cl. CEPHALOPODA) Tatarian 9.4 LATE PERMIAN Ord. PTERIOIDA (Cl. BIVALVIA) Guadalupian 10.2 Ord. PODOCOPIDA (Cl. OSTRACODA) Ord. RHYNCHONELLIDA (Cl. ARTICULATA) Leonardian 9.4 Ord. SPIRIFERIDA (Cl. ARTICULATA) EARLY PERMIAN Sakmarian 14.6 Ord. TEREBRATULIDA (Cl. ARTICULATA) Asselian 4.4 Cl. OSTEICHTHYES Ord. COELOCANTHIFORMES Table 1.- Epochs, ages and time duration in the Permian and Triassic Ord. PALAEONISCIFORMES (see text for details) Ord. PTYCHOLEPIFORMES Tabla 1.- Épocas, edades y lapsos temporales del Pérmico y el Triásico (ver texto para más detalle) Ord. BOBASATRANIFORMES Ord. SAURICHTHYFORMES Ord. PHOLIDOPLEURIFORMES 4. The data considered and its treatment Ord. PERLEIDIFORMES Ord. PELTOPLEURIFORMES 4.1. Chronostratigraphy Ord. SEMIONOTIFORMES Ord. PYCNODONTIFORMES Inconsistencies in the nomenclature used to refer to dif- Ord. AMIIFORMES ferent chronostratigraphic units in the compendium, to the Ord. MACROSEIMIIFORMES extent that some names were not taken from the Interna- Ord. PACHYCORMIFORMES tional Stratigraphic Chart published by the “International Commission on Stratigraphy”, required us to spend some 4.3. Treatment applied time consulting chronostratigraphic scales and analysing equivalences. The epochs and ages we fi nally used, and For each of the taxa indicated, for each age, we calcu- their estimated duration (dt) can be seen in Table 1. lated the number of fi rst (FA) and last (LA) appearances, the number of existing genera (N) in that taxon in that 4.2.
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