Sternaspidae Carus, 1863

Sendall, Kelly & Salazar-Vallejo, Sergio I., 2013, Revision of Sternaspis Otto, 1821 (Polychaeta, Sternaspidae), ZooKeys 286, pp. 1-74 : 15-16

Family Sternaspidae Carus, 1863

Type genus.

Sternaspis Otto, 1821.

Diagnosis.

Body peanut-shaped. Introvert with falcate, tapered or subdistally expanded hooks. Segments 7-8 constricted, with genital papillae protruding ventrally. Pre-shield region with 7 or 8 segments. Ventro-caudal shield usually stiff, often provided with radiating ribs and concentric lines, rarely flexible. Marginal shield chaetal fascicles include lateral and posterior chaetae, sometimes peg chaetae or additional delicate chaetae present. Branchiae coiled, abundant filaments, emerging from two lateral dorsal plates, near the anus, or directly from the body wall. Additional, thinner coiled interbranchial papillae present.

Composition. Three genera: Sternaspis , Caulleryaspis gen. n. and Petersenaspis gen. n.

Remarks.

Vejdovský (1882) published a very thorough account of the anatomy, physiology and development of Sternaspis scutata ; only a few months later, Rietsch (1882) published an equally thorough account of the same species. The reason Sternaspis was given so much attention was likely due to the argument over the distinction between “Gephyrea” and Chaetopoda within Annelida, and that Sternaspis had attributes that pertained to both groups. In general, Sternaspis does resemble an echiurid from the exterior, even more so if one confuses the anterior end with the posterior, as was the case until corrected by Krohn (1842). Vejdovský (1882) and Rietsch (1882) outlined the affinities aligning Sternaspis with the polychaetes and shortly afterwards Sternaspis was accepted as a polychaete ( Dahl 1955).

The family was proposed by Carus (1863: 453) and one hundred years later, it was regarded as forming an independent order by Dales (1962). This proposal was accepted by Fauchald (1977), Pettibone (1982), George and Hartmann-Schröder (1985), and Hartmann-Schröder (1996). An analysis of morphology and six genes ( Zrzavý et al. 2009) did not clarify the affinities for sternaspids because different approaches gave different topologies or affinities. Thus, their Bayesian combination indicates Sternaspidae are a sister group to a clade including sabellids-serpulids, sabellariids, and Trochochaeta - Spionidae - Poecilochaetus . The unweighted maximum-parsimony indicates they form a clade with sabellariids, which is a sister group to Sabellidae and Trochochaeta - Spionidae - Poecilochaetus . The weighted maximum-parsimony indicates they group with Fauveliopsidae , and together become a sister group for Sabellidae - Serpulidae , which is a sister group to Sabellariidae and the other grouped taxa of former analysis.

Key to genera of Sternaspidae Carus, 1863