Triassic: the Crucial Period of Post- Palaeozoic Crinoid Diversification

Triassic: the crucial period of post- Palaeozoic crinoid diversification Swiss Journal of Palaeontology ISSN 1664-2376 Volume 130 Number 1 Swiss J Palaeontol (2010) 130:91-112 DOI 10.1007/ s13358-010-0009-9 1 23 Your article is protected by copyright and all rights are held exclusively by Akademie der Naturwissenschaften Schweiz (SCNAT). This e-offprint is for personal use only and shall not be self-archived in electronic repositories. If you wish to self-archive your work, please use the accepted author’s version for posting to your own website or your institution’s repository. You may further deposit the accepted author’s version on a funder’s repository at a funder’s request, provided it is not made publicly available until 12 months after publication. 1 23 Author's personal copy Swiss J Palaeontol (2011) 130:91–112 DOI 10.1007/s13358-010-0009-9 Triassic: the crucial period of post-Palaeozoic crinoid diversification Hans Hagdorn Received: 26 July 2010 / Accepted: 24 September 2010 / Published online: 7 December 2010 Ó Akademie der Naturwissenschaften Schweiz (SCNAT) 2010 Abstract After their near-extinction around the end of was added. Crinoidal limestones, as common in the Pal- the Permian, crinoids recovered during the Triassic and re- aeozoic, had their last appearance in Middle Triassic times. occupied almost all ecological niches they had held in Palaeozoic times. Triassic crinoids comprise 33 genera in Keywords Crinoids Á Triassic Á Diversity Á Functional 12 well-defined families and 5 orders of the subclass Ar- morphology Á Evolutionary biology Á Palaeoecology Á ticulata; the systematic position of 4 additional families is Niche adaptation unknown. The highest diversity was before the Mid Car- nian Wet Intermezzo that caused the extinction of the order Encrinida. Major morphologic changes were connected Introduction with the adaptation to various benthic habitats and to pseudoplanktonic and eleutherozoic modes of life. Con- Triassic crinoids gained scientific interest (Agricola 1546) vergently, the cups of Encrinida and Holocrinida–Isocrin- long before their echinoderm nature was known (Rosinus ida became cryptodicyclic with large muscular radial 1719). Encrinus liliiformis, the stone lily of the eighteenth facets, arm numbers increased from 5 to more than 300, century naturalists, was a favorite object in art cabinets. and the arms of Encrinida became gradually biserial. The Moreover, crinoidal limestones from the Muschelkalk were Encrinida remained permanently fixed to hardgrounds and named by early stratigraphers using Agricola’s term acted as frame builders in bioherms. By encrusting bivalve trochites (wheelstones) for the cylindrical encrinid col- mudstickers some dadocrinids also became secondary soft umnals. The Trochitenkalk (Schlotheim 1820) has nowa- bottom dwellers. The holocrinid stem evolved preformed days the rank of a formation. Since then, Encrinus rupture points at the lower nodal facets, allowing these liliiformis has become one of the best known crinoids in crinoids to attach intermittently by cirri. The pseudo- morphological, palaeoecological and taphonomic respects, planktonic traumatocrinids evolved extremely long, flexi- and the Trochitenkalk became a model for crinoidal ble stems with multiple pore systems and terminal root limestone formation. Although several Triassic crinoid cirri. Paracomatulids and eocomatulids reduced their stems species and genera have been added subsequently (for an and adapted to an eleutherozoic mode of life. Somphocri- overview see Biese 1934 and Simms 1990b), their true nids miniaturized and remodeled their skeleton towards diversity has long been disregarded, as many taxa were lightweight construction and adapted to a planktonic life later included into the synonymy of Encrinus or Pentac- style. After the Triassic no fundamentally novel adaptation rinus. Other taxa are based on poorly preserved and fragmentary material. This is particularly true for the family Isocrinidae, whose Triassic record consists mainly of isolated columnals and cirrals. They are found in Lagersta¨tten, in which autotomized and subsequently disarticulated dis- & H. Hagdorn ( ) tal stem parts have been accumulated. Muschelkalkmuseum Ingelfingen, Schloss-Str. 11, 74653 Ingelfingen, Germany This is the state of the art as reflected in the crinoid e-mail: encrinus@hagdorn-ingelfingen.de volumes of the Treatise (Moore and Teichert 1978) which Author's personal copy 92 H. Hagdorn reported only nine genera and five families for the entire comprises the families Encrinidae, Dadocrinidae, Trau- Triassic. In the meantime, many publications have matocrinidae, and Ainigmacrinidae. The true diversity of increased the number of well-defined taxa. They shed new Triassic crinoids is probably even broader, because there light on the post-Palaeozoic crinoid phylogeny (Klikushin are new finds from the early Carnian Cassian Formation of 1992; Simms 1990a, b; Simms and Sevastopulo 1993; the Dolomites (Italy) and from the middle Carnian Hagdorn 1995; Simms 1999). Hanwang Formation of Sichuan (Central China) that still Due to Hans Hess’s experience and effort, the Articulata await description. volume of the revised Crinoid Treatise has been finished The present paper is based on the classification that and awaits publication (Hess 2010a). It includes all post- Hans Hess used in the new Treatise. It does not deal with Palaeozoic crinoids and lists 33 Triassic genera in 12 well- the Palaeozoic ancestors and their extinction (Simms and defined families and 5 orders; the systematic position of 4 Sevastopulo 1993), nor with the Early Triassic echinoderm additional families is uncertain (Fig. 1). Unlike the 1978 bottleneck, which has only recently been summarized by Treatise that assigned Encrinidae (with only one valid Twitchett and Oji (2005). Its aim is rather to give a pre- genus) to the subclass Inadunata, this clade is now regarded liminary and concise overview of radiations and morpho- as a separate order Encrinida of the subclass Articulata and dynamics during the Triassic recovery, in particular (1) Fig. 1 Triassic crinoid diversification. Genus and higher taxonomic etching process during preparation. In this paper 5 well characterized units are based on Hess (in press). Numbers indicate valid species as Osteocrinus species were selected. Nominal species attributed to the referenced in the Appendix. Artefacts may originate from the limited parataxonomic genus Entrochus were excluded. A distinct faunal fossil record. Conservation Lagersta¨tten with diverse crinoid palae- change caused by the ‘‘Mid Carnian Wet Intermezzo’’ is indicated by ocommunities such as the Anisian Muschelkalk or the late Ladinian/ the extinction of order Encrinida, while Isocrinida and Millericrinida early Carnian Cassian Formation may be overrepresented compared persisted into the Norian and later Mesozoic. Thus, four Triassic to early Ladinian or early Norian sediments that have yielded benthic crinoid associations can be distinguished (cf. Fig. 11), (1) an relatively few crinoids. Moreover, the diversity of Isocrinidae Early Triassic Holocrinida association of extremely low diversity, (2) recorded in countless nominal ‘‘Isocrinus’’ species based on isolated a diverse Middle Triassic Holocrinida/Encrinida association, (3) an columnals (Simms 1990a, b) is certainly higher than in this chart. The early Late Triassic Isocrinida/Encrinida association, (4) a late Late species concept of Osteocrinus (ca. 15 nominal species) and of the Triassic Isocrinida/Millericrinida association. The major turnover benthic microcrinoids is also based on isolated sclerites showing happened in Carnian times after the overall Triassic diversity had minimal differences, many of which may have resulted from the reached its peak Author's personal copy Triassic: the crucial period of post-Palaeozoic crinoid diversification 93 crinoid diversity through the Triassic stages and substages, 8. ligamentary articulations in distal arms; (2) character evolution and functional morphology with a 9. brachials pinnulate, with the second pinnular longer focus on convergent adaptations, (3) ecological niches. than the first; With regard to the entire class Echinodermata, post-Pal- 10. proximal stem pentagonal, distally becoming aeozoic radiation has been dealt with by Simms (1990a), circular; Hagdorn (2000) and Twitchett and Oji (2005). Due to their 11. proximal nodals with cirri; poor fossil record and fragmentary preservation, the 12. terminal discoid holdfast. Quingyanocrinidae (Stiller 2000) and the Triassic microc- During the Triassic, most of these characters underwent rinoid families Tulipacrinidae, Lanternocrinidae and significant changes. Thereby, the morphospace expanded Leocrinidae (Kristan-Tollmann 1990) have also been with the derived character sets being distinctive for the excluded. They are taken into account, however, in the more advanced later clades. Ancestral features, however, diversity chart (Fig. 1). may be preserved in juveniles. Examples are the uniserial arms in advanced encrinids or rudimentary cirri in some encrinids, or even discoid holdfasts in extant comatulids. Evolutionary trends and morphodynamics The living Proisocrinus has retained a holdfast even in the adult stage and reduced the cirri to the proximal stem. The fossil record of the less derived Early and Middle The rich fossil record of the Encrinida and the less Triassic crinoids contains a set of ancestral characters continuously documented lineage leading from Holocrinida shared by the orders

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