<strong>Phylogeny of Eunicida (Annelida) based on morphology of jaws</strong>

Abstract

Eunicida have a complex jaw apparatus with a fossil record dating back to the latest Cambrian. Traditionally, Eunicidae, Onuphidae, and Lumbrineridae were considered closely related families having labidognath maxillae, whereas Oenonidae with prionognath type maxillae were thought to be derived. Molecular phylogenies place Oenonidae with Eunicidae/Onuphidae, and Lumbrineridae as the most basal taxon. Re-evaluation of the jaw types based on morphology and ontogeny demonstrated that the labidognaths Eunicidae and Onuphidae have a closer relationship to the prionognath Oenonidae than was previously thought. Lumbrineridae are neither labidognath nor prionognath; therefore a new type, Symmetrognatha, is proposed. Homologies of jaw elements and considerations of functional aspects of the jaw apparatus are explored to present a hypothesis of the Eunicida phylogeny. The earliest fossils are of placognath and ctenognath types, lacking maxillary carriers. While the former are extinct, the latter are represented by the extant Dorvilleidae. The interpretation of relationships between the carrier-bearing families depends on whether the carriers are thought to have evolved once only or twice independently. The similarity of the carrier structure and their associated muscles suggests the former, placing the Lumbrineridae as sister to Eunicidae/Onuphidae and Oenonidae. However, the ontogeny of the eunicid/onuphid apparatus as well as its adult structure differ greatly from those of lumbrinerids, indicating that the lumbrinerid carriers may have evolved independently and earlier than in eunicids/onuphids and oenonids.

Diet of Worms Emended: An Update of Polychaete Feeding Guilds

“…First, we use the term jaws only for a pair of rigid structures that through the operation of integral hinges and musculature can bite or chew food, reducing it to smaller sizes or at least altering its mechanical properties. This term clearly applies to the hinged jaws of Eunicida (Paxton 2009). Nereididae and Polynoidae (scaleworms) have strongly articulated, multifunctional jaws, and we tentatively propose that these jaws use a muscle articulation joint similar to that of cephalopod beaks (Uyeno & Kier 2005) to achieve multifunctionality comparable to eunicidan jaws.…”

Jaw elements in Plumulites bengtsoni confirm that machaeridians are extinct armoured scaleworms

“…The sister group of the Phyllodocida, the Eunicida, is well documented from the Early Ordovician onwards [29] but unequivocal records of the Phyllodocida were not known until the Middle Devonian fossil Arkonips [43]. The presence of crown-group phyllodocidans in the Ordovician confirms that major cladogenetic events in this taxon had already occurred by this time, as is the case in Eunicida, in which the majority of family-level divergences had occurred by the Middle or Late Ordovician [28,37]. Data accessibility.…”

Reconciling taxonomy and phylogeny in the bristleworm family Eunicidae (polychaete, Annelida)

“…Pair of cirri on posterior peristomial ring present or absent. Asymmetric eulabidognath jaws ( sensu Paxton ) bearing 4 or 5 paired plates and 1 unpaired. Biramous parapodia, notopodia reduced to notopodial cirri.…”