Ziphirostrum du Bus, 1868

Lambert O., 2005, Systematics and phylogeny of the fossil beaked whales Ziphirostrum du Bus, 1868 and Choneziphius Duvernoy, 1851 (Mammalia, Cetacea, Odontoceti), from the Neogene of Antwerp (North of Belgium), Geodiversitas 27 (3), pp. 443-497 : 447

Genus Ziphirostrum du Bus, 1868

Ziphirostrum du Bus, 1868: 622 .

Mioziphius Abel, 1905: 98 , partim.

TYPE SPECIES. — Ziphirostrum marginatum du Bus, 1868 by present designation.

OTHER INCLUDED SPECIES. — Z. turniense du Bus, 1868 and Z. recurvus ( du Bus, 1868) n. comb.

EMENDED DIAGNOSIS. — A fossil ziphiid genus differing from:

– Choneziphius , Tusciziphius , and Ziphius in: the absence of elevated longitudinal maxillary crest on the supraorbital process; less asymmetrical premaxillary sac fossae (ratio between maximum widths of left and right fossae higher or equal to 0.69); and anterodorsally shorter nasals;

– Choneziphius in: the excavation of a prenarial basin at the base of the rostrum margined by a wide strip of the maxillae elevated towards the antorbital notches; flat surface of the premaxillary sac fossa lacking a strong anterior concavity;

– Aporotus in: fused premaxillae above the mesorostral groove; strip of the maxilla limiting the prenarial basin anterolaterally, without valley along the lateral side of the elevated premaxilla on the rostrum;

– Beneziphius n. gen. in: a relatively longer and less pointed rostrum; a deeper prenarial basin; the lack of excrescences on the dorsal surface of the maxilla along the prenarial basin;

– other known ziphiids in the fusion of the thickened premaxillae above the mesorostral groove and the presence of a prenarial basin.

Most of the characters defining Ziphirostrum are present in Messapicetus , except the very dense rostrum, which is variable in Ziphirostrum . The prenarial basin is probably shallower in Messapicetus . Those two genera might therefore be more closely related than suggested by Bianucci et al. (1994) (see discussion below).

REMARK

When du Bus (1868) used for the first time the genus name Ziphirostrum , he intended to refer several new species to the same genus than Dioplodon d’Hemixem Van Beneden, 1860 . However, the specimen on which Van Beneden (1860) based Dioplodon d’Hemixem (later renamed by Van Beneden [1864] Ziphirostre d’Hemixem ) was lost, and Van Beneden (1860, 1864) did not provide any illustration. Abel (1905) therefore suggested a new genus name, Mioziphius , to clarify the situation, and he named a new single species, M. belgicus . However, more recent authors always use the genus name Ziphirostrum ( Mead 1975; Muizon 1984, 1991; Bianucci et al. 1992, 1994; McKenna & Bell 1998; Fordyce & Muizon 2001). Because there is no evidence to determine what specimen constitutes the species Dioplodon d’Hemixem , and because of the Principle of Priority ( ICZN 1999: Art. 23), the genus name that should be used is Ziphirostrum . Within Ziphirostrum , the first species that can be identified from its original description is Z. marginatum du Bus, 1868 . The single specimen included in this species by du Bus (1868: 624) was the partial skull IRSNB 3783-M.1878.