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Journal of Paleontology

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Syzygial Brachials from the Upper Muschelkalk (Middle Triassic, Ladinian) of Poland and Their Implication for an Early Origin of Comatulid Crinoids

Mariusz A. Salamon¹, Michat Zato¹ and Przemysaw Gorzelak¹

¹ University of Silesia, Faculty of Earth Sciences, Bdziska Street 60, Pl-41-200 Sosnowiec, Poland, <paleo.crinoids@poczta.fm>

The first 20% of the full text of this article appears below.

	INTRODUCTION

 
ACCORDING TO Ubaghs (1978), syzygies are brachial articulations in which radiating ridges and furrows on the two joint faces oppose each other rather than interlock as in symplexies. Cryptosyzygies differ from syzygies by having very short ridges that may be replaced by rows of tubercles or granules, with a tendency toward irregular arrangement and disappearance. Among Triassic crinoids, only representatives of the orders Isocrinida Sieverts-Doreck, 1952 and Comatulida Clark, 1908 had cryptosyzygial or syzygial brachial articulation, respectively. According to Rasmussen (1978), among Isocrinidae the articulations of primibrachial 1 and 2 and secundibrachial 1 and 2 were cryptosyzygial or synarthrial (but see also comments in Simms, 1988a). Among Comatulida, syzygial articulations generally occur between brachials 3 and 4 and in more distal arm parts.

The syzygial brachial plates from Middle Triassic (Ladinian, Longobardian) Upper Muschelkalk of the Holy Cross Mountains (Central Poland) represent the oldest record of syzygial articulation in crinoid arms. Because the representatives of order Comatulida are known from the Carnian? (Simms, 1988a) and the Norian/Rhaetian (Hagdorn and Campbell, 1993), the authors assign the Ladinian remains to holocrinids, whose columnals and cirrals were encountered in the investigated locality.

	MATERIAL AND METHODS

 
Four bulk interval samples from cleaned faces at four outcrops of Ceratites Beds at Brudzów (Middle Triassic, Upper Muschelkalk, enodis Zone, Longobardian sensu Trammer, 1975) in the Holy Cross Mountains (Central Poland) were obtained, each weighing ca. 30 kg. Brachial plates with a syzygial pattern and accompanying columnals and cirrals were gathered only at one of the localities (Fig. 1.1). The samples were very rich in fossils such as bivalves, ceratitid ammonoids (see Niedwiedzki et al., 2001), and brachiopods (detailed faunal assemblage in Trammer, 1975). Among echinoderms, isolated asteroid ossicles and echinoid spines were common. On the . . . [Full Text of this Article]