Ecophenotypic variations of Encrinus liliiformis (Echinodermata: Crinoidea) from the middle Triassic Muschelkalk of Sout
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Ecophenotypic variations of Encrinus liliiformis (Echinodermata: Crinoidea) from the middle Triassic Muschelkalk of Southwest Germany Janina F. Dynowski • James H. Nebelsick
Received: 22 June 2010 / Accepted: 1 October 2010 / Published online: 2 December 2010 Akademie der Naturwissenschaften Schweiz (SCNAT) 2010
Abstract Encrinus liliiformis is a well known crinoid from the middle Triassic Muschelkalk of Europe. A statistical analysis of crown shape was conducted in order to quantify possible differences in crown morphology of E. liliiformis originating from three localities in Southwest Germany (Upper Muschelkalk). These differences basically refer to the length of the brachia and ornamentation patterns on the aboral surfaces of the brachials. The populations originate from different environments: Crailsheim, reflecting a shallow water habitat on a carbonate ramp; Neckarwestheim and Mistlau, originating from a deeper basinal environment. The analysis led to a distinction of two ecophenotypes adapted to the varying habitats: (1) an ecophenotype originating in shallow water showing shorter brachia with less ornamented surfaces of brachials; this type is represented by the Crailsheim population; (2) an ecophenotype originating in a deeper water environment showing longer brachia and a higher degree of ornamentation on brachial surfaces, as represented by the Neckarwestheim population. The crinoids from the Mistlau locality take up an intermediate position in morphology, but the low number of specimens does not allow for statistically significant comparisons. Interpretations of these differences in crown morphology are made with respect to reactions to predatory pressure as well as to variations in
J. F. Dynowski (&) Staatliches Museum fu¨r Naturkunde Stuttgart, Rosenstein 1, 70191 Stuttgart, Germany e-mail: [email protected] J. F. Dynowski J. H. Nebelsick Institut fu¨r Geowissenschaften, Eberhard Karls Universita¨t Tu¨bingen, Sigwartstraße 10, 72076 Tu¨bingen, Germany
water flow energy which is of prime importance for obtaining food resources for these filter feeding animals. Keywords Crinoids Ecophenotypes Encrinus liliiformis Muschelkalk Triassic
Introduction Phenotypic plasticity is an important and thus intensively discussed subject in functional morphology from both ecological and genetic standpoints. Even for Recent organisms, where detailed information on morphology, living conditions as well as genetics is available, it is still difficult to determine and disseminate the interactions of morphology and environment and potential reasons for differences in phenotypes (for further details see WestEberhard 2003 or DeWitt and Scheiner 2004). As far as organisms from the fossil record are concerned, only morphological features and palaeoecological data are available to interpret coherences of skeletal morphology and the ambient environment. Genetic information is unknown for the majority of fossils, being restricted to relatively young material preserved under very special conditions. It is t
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