. Bulletins of American paleontology. 16 Bulletin 368 Terminology Crinoid terminology follows Ubaghs et al. in Moore and Teichert (1978). with nioditications by Webster (1974) and Webster and Lane (1987). Blastoid termi- nology follows the Treatise (Moore, 1967). as modi- fied by Breimer and Macurda (1972). Columnal nod- itaxis formulae are after Webster (1974), and measure- ment and curvature teminology are after Webster and Jell (1999a). Basal Cup aud Proximal Stent The terms stem impression, basal concavity, and basal invagination have been used interchangeably and indiscriminantly by vario
. Bulletins of American paleontology. 16 Bulletin 368 Terminology Crinoid terminology follows Ubaghs et al. in Moore and Teichert (1978). with nioditications by Webster (1974) and Webster and Lane (1987). Blastoid termi- nology follows the Treatise (Moore, 1967). as modi- fied by Breimer and Macurda (1972). Columnal nod- itaxis formulae are after Webster (1974), and measure- ment and curvature teminology are after Webster and Jell (1999a). Basal Cup aud Proximal Stent The terms stem impression, basal concavity, and basal invagination have been used interchangeably and indiscriminantly by various authors in the past. For uniformity of description, we propose and apply the following terminology when describing the base of the cup (Te.\t-fig. 3). Horizontal infrahasal or basal circlet.âforms a planar fused (one single plate) or articulated (two to five plates) plate at the base of the cup normal to the linear axis of the crinoid, irrespective of the living ori- entation of the animal (Text-hg. 3A). There is no flex- ure in the plate(s) although the exterior surface distal to the stem facet may contain elevated or depressed ornamentation. Stem facet.âis the circular or polygonal attachment scar formed where the stem attaches to the base of the cup. Stem facet refers only to the configuration of the attachment scar, which may or may not be horizontal and may or may not have a central depression (Text- tig. 3B). The stem facet may be flush with the external surface of the cup (usually the infrabasal or basal cir- clet) or, more commonly, at the base of an impression. Stem facet is distinct from articular facet. Articular facet is applied to the proximal and distal articular sur- faces of columnals, but these are easily distinguished in context, and usually referred to as columnal facets. Stem impression.âis the depression on the external surface of the cup (usually the infrabasal or basal cir- clet) formed by an inset of the proximal columnal into the cup with or witho
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