Pseudoscalibregma Ashworth, 1901

Mendes, Samuel Lucas Da Silva Delgado, Paiva, Paulo Cesar De & Rizzo, Alexandra E., 2024, New species of Pseudoscalibregma Ashworth, 1901 (Annelida: Scalibregmatidae Malmgren, 1867) from Brazil, Zootaxa 5399 (1), pp. 19-36 : 20-21

Genus Pseudoscalibregma Ashworth, 1901

Type species. Pseudoscalibregma parvum ( Hansen, 1879)

Diagnosis. Body elongated,arenicoliform.Prostomium with frontal horns.Peristomium as a single ring, encompassing prostomium dorsally and forming mouth upper lip ventrally; lower lip formed from elements of peristomium and chaetiger 1. Posterior parapodia with dorsal and ventral cirri; interramal papillae present; postchaetal lamellae absent. Branchiae absent. Chaetae include capillaries, lyrate chaetae, and sometimes few inconspicuous spinous chaetae among capillaries of chaetigers 1 to 2, blunt, pointed, or bifurcated, representing homologues of lyrate chaetae found on following chaetigers; large conspicuous spines absent. Pygidium with long anal cirri.

Remarks. Ashworth (1901) erected the genus Pseudoscalibregma , and included three species: P.parvum ( Hansen, 1879) , P. longisetosum ( Théel, 1879) and P. reticulata ( McIntosh, 1885) . Both P. reticulata and P. longisetosum were previously considered as members of the currently invalid genus Eumenia Örsted, 1843 . Day (1961) examined the type material of Eumenia reticulata McIntosh, 1885 and questioned Ashworth’s (1901) transference to the genus Pseudoscalibregma ; consequently Furreg (1925) treated this species as a synonym of P. parvum . So, Day (1967) concluded that E. reticulata must be referred to as Hyboscolex reticulata ( McIntosh, 1885) . Hartman (1978) referred the genus Eusclerocheilus Hartman 1967 to Pseudoscalibregma , afterwards Blake (1981) confirmed this synonymy. Kudenov & Blake (1978) transferred P. aciculata Hartman, 1967 to Oligobregma aciculata ( Hartman, 1967) and delimited the diagnostic characteristics of both Pseudoscalibregma and Oligobregma Kudenov & Blake, 1978 . Blake (1981) continued advances on the taxonomy of the genus, combining P. collaris Levenstein, 1975 and P. bransfieldia collaris Hartman, 1978 and described a new species Oligobregma collare Blake, 1981 . In addition, Blake also corrected the wrong replacement of E. bransfieldia Hartman, 1967 with Hyboscolex bransfieldia ( Hartman, 1967) , made by Blake & Kudenov (1978), transfering H. bransfieldia to P. bransfieldium ( Hartman, 1967) . More recently, Bakken et al. (2010) and Bakken et al. (2014) synonymized: Scalibregma parvum , Eumenia longisetosa Théel, 1879 and P. logisetosum ( Théel, 1879) , to P. parvum , giving priority to Hansen’s (1879) name. Scḩller (2008), Imajima (2009), Blake (2015) provide the most recent taxonomic revision and Blake (2023) describe new species in this genus and extending its distribution to abyssal depths.

Currently, Pseudoscalibregma is a small genus, with ine valid species: a) P. parvum ( Hansen, 1879) from Norwegian Sea, North Atlantic; b) P. pallens Levenstein, 1962 from Kermadec Trench, Pacific Ocean; c) P. bransfieldium ( Hartman, 1967) from Bransfield Strait, Antarctica; d) P. usarpium Blake, 1981 from Ross Sea, Antarctica; e) P. hartmanae ( Blake, 1981) from Weddel Sea, Antarctica; f) P. papilia Sch ̧ller, 2008 from South Sandwich Islands, Southern Atlantic; g) P. orientalis Imajima, 2009 from Kashima Sea, Pacific Ocean; h) P. palmeri Blake, 2015 from East Antarctic Peninsula; and i) P. glandipodium Blake, 2023 from Eastern Australia, Pacific Ocean ( Blake 1981, Scḩller 2008, Parapar et al. 2021, Blake 2023). Most of these species occur on soft bottoms at great depths, being reported from all oceanic regions ( Parapar et al. 2021). Possible occurrences from the Brazilian coast may be related to species formally reported from the Antarctic and Atlantic oceans, including P. bransfieldium , P. usarpium , P. hartmanae , P. papilia and P. palmeri ( Blake 1981; Scḩller 2008; Blake 2015).

This genus belongs to a subgroup of scalibregmatids with an “arenicoliform” body, presenting both dorsal and ventral cirri on parapodia and lacking acicular spines on anterior chaetigers ( Ashworth 1901; Day 1967; Kudenov & Blake 1978; Blake 1981; Kudenov 1985; Blake 2015; Blake 2020; Blake 2023). Importantly, the presented diagnosis followed Blake (2015), and the only character that separates Pseudoscalibregma from Scalibregma Rathke, 1843 is the absence of branchiae on body chaetigers in the first and presence in the second, especially on chaetigers 2–5. Ashworth (1901) established the first taxonomic arrangement of the family, separating the species in two groups related to the general body shape. This has been followed until recently and Kudenov & Blake (1978) expanded Ashworth’s proposal. However, we reinforce that the taxonomic arrangement of the family proposed by Ashworth (1901) and by Blake & Kudenov (1978) is problematic, due to the overlap of several characters between genera ( Blake 2000; Blake 2015; Parapar et al. 2021).