(Figs 5, 16, 20–21, 31, 46, 56)
Halipeurus sp.; Hilburn, 1990: 187.
Halipeurus sp. nov. (A); Zonfrillo, 1993: 327. Halipeurus sp. GLA 959; Hammer et al., 2010: 1114, 1116.
TYPE HOST: Pterodroma madeira Mathews, 1934.
TYPE LOCALITY: Madeira Island, North Atlantic Ocean.
HOLOTYPE: 3 in MONZ.
DIAGNOSIS: Male: habitus as in Fig. 20; clypeal signature as in Fig. 5; terminalia (ventral view) as in Fig. 31; genitalia as in Fig. 56. Female: habitus as in Fig. 21; clypeal signature as in Fig. 16; terminalia (ventral view) as in Fig. 46.
Measurements of both sexes as in Table 1.
ETYMOLOGY: The species epithet atlanticus is a noun in apposition derived from the word Atlantic, referring to the ocean where the geographical ranges of the hosts of this louse are situated. MATERIAL EXAMINED
Types
Ex Pterodroma madeira: Holotype 3 (MONZ, AI.023873), allotype Ƥ, Madeira I., North Atlantic Ocean, Sep. 1990, F. Zino (MONZ). Twenty-four paratypes as follows: 23, 1 Ƥ, Madeira I., North Atlantic Ocean, 30 May 1987, F. Zino (MONZ; MFMP); 13, 1 Ƥ, Madeira I., North Atlantic Ocean, Jul. 1989, F. Zino (MONZ); 33, 2 Ƥ, Madeira I., North Atlantic Ocean, 10 Apr. 2003, F. Zino (MONZ; MFMP); 33, 4 Ƥ, Madeira I., North Atlantic Ocean, 21 Apr. 2005, F. Zino (MONZ; MFMP); 7 Ƥ, Madeira I., North Atlantic Ocean, 31 May 2006, F. Zino (MONZ; MFMP).
Non-types
Ex Pterodroma cahow (Nichols & Mowbray, 1916): 13, 1 Ƥ, Inner Pier, Bermuda, 16 Jun. 1969 (MONZ); 13, 1 Ƥ, Nonsuch I., Bermuda, 31 Mar. 1988, D. Wingate & D. Hilburn (MONZ); 1 Ƥ, Azores Is, North Atlantic Ocean, Nov. 2003, B. Zonfrillo (MONZ).
DISCUSSION: Morphologically, Halipeurus atlanticus is extremely similar to H. procellariae (J.C. Fabricius, 1775) recorded from five species of Pterodroma (Price et al. 2003: 188). Males only differ in details of the genitalia, and females are indistinguishable at present. However, molecular analysis has shown that they are not as closely related as their morphology would indicate. Values calculated as percentage sequence divergence between H. atlanticus (ex Pt. madeira) and Halipeurus procellariae (ex Pt. lessonii) are 12.7– 13 % for the 12 S gene, and 14.5% for the COI gene (Joseph Hughes pers. comm. 2007). Furthermore, Hammer et al. (2010) have found that H. procellariae and H. consimilis Timmermann, 1960 are sister species, and that H. atlanticus (as H. sp GLA 959) is sister to these two taxa. However, the phylogenetic trees in Hammer et al. (2010: 1113) for this clade show that bootstrap support and Bayesian posterior probabilities are low for these relationships. Therefore, morphological data may still be showing the true relationship between H. atlanticus and H. procellariae as sister species.
Recent research by Jesús et al. (2009) on the phylogeny of the two subspecies of Pterodroma feae (Salvadori, 1899) and Pt. madeira shows that these species are more closely related to each other than to other North Atlantic species such as Pt. cahow and Pt. hasitata (Kuhl, 1820). Considering that both Pterodroma feae deserta (Mathews, 1934) and Pt. hasitata harbour Halipeurus theresae Timmermann, 1969 (Zonfrillo 1993), the presence of H. atlanticus on Pt. madeira and Pt. cahow is incongruent with the phylogeny of its hosts.