First record of Megaramphoprion (Annelida; Polychaeta) in Laurentia

Abstract

The Huntington cluster (USNM 536849; Fig. 1) measures 4.1 mm in total length and is comprised of five elements of the maxillary apparatus; the first and second pair of maxillae (right and left MI and MII) and the basal plate (Bp) fitted into the bight of the right MI (for descriptive terminology for ramphoprionids, see Kielan-Jaworowska, 1966; Eriksson, 2001; Fig. 2). Both the MI are broken and lack approximately a third of the anterior end. The right MI also lacks part of its posterior denticulated ridge; the posteriormost tip (p in Fig. 1.2) is, however, still preserved and partly embedded in the slab. Most of the right MII is missing and only a thin rim is exposed, showing the outline of the element. The left MII is almost complete, lacking only a fifth of the anterodorsal end. The basal plate is well preserved and can be seen in full detail, except for a part of the antero-dextral flange, which is broken off (Fig. 1.3). Adjacent to the maxillary apparatus are other fragments that might be the carriers (Fig. 1.4), i.e., the posteriormost, supporting elements of the apparatus. Except for these possible carriers, all elements are more or less in natural position.