Australomonstrillopsis Suárez-Morales & McKinnon, 2014

Suárez-Morales, Eduardo & Mckinnon, A. David, 2014, The Australian Monstrilloida (Crustacea: Copepoda) I. Monstrillopsis Sars, Maemonstrilla Grygier & Ohtsuka, and Australomonstrillopsis gen. nov., Zootaxa 3779 (3), pp. 301-340 : 315

Genus Australomonstrillopsis Suárez-Morales & McKinnon gen. nov.

Diagnosis for males. Cephalothorax with paired perioral sac-like protrusions on ventral surface and folds on dorsal surface. Antennules geniculate, five-segmented; terminal antennular segment bearing two inner rounded expansions; apical element 2 modified into short, curved sabre-like structure, element 1 subequally long. Cephalothorax with anteroventral perioral sac-like protuberances and dorsal cuticular folds. Legs 1–4 with usual segmentation and armature of monstrilloids except for absence of inner seta on first exopodal segment. Fifth legs absent. Urosome 5-segmented. Genital complex poorly developed, with extremely short shaft and minute, rounded lappets. Postgenital somite with ventral rounded process. Caudal rami with 5 setae, rami symmetrical but strongly modified, massively developed, with several protuberances armed with one or two setae each. Females unknown.

Etymology. Combined name referring to Australia, the country from which it was first collected and Monstrillopsis , the genus to which it has the closest morphological affinity.

Type species. Australomonstrillopsis crassicaudata sp. nov.

Remarks. The new genus is erected to accommodate a male specimen with a remarkable combination of important genus level characters not present in any other genus of the Monstrilloida . It has a 5-segmented geniculate antennule that resembles that of Monstrillopsis in its general structure and armature, particularly in the presence of an inner protuberance of the last segment and the structure of the apical elements. Setal element 2 (sensu Huys et al. 2007) forms a distinctive sabre-like structure in males of Monstrillopsis ( Huys & Boxshall 1991; Suárez-Morales et al. 2006) and element 1 is relatively short, as in Mon. fosshageni , Mon. chathamensis , and Mon. cahuitae ( Suárez-Morales & Dias 2001; Suárez-Morales & Morales-Ramírez 2009; Suárez-Morales et al. 2013). In the new genus element 2 is short, curved and only slightly longer than element 1. This character is not present in males of Monstrillopsis . Another unique character present in the new genus is the peculiar cuticular processes of the cephalothorax, forming sac-like protuberances on the anteroventral surface but also dorsal folds. An important apomorphy found in this genus is the absence of an inner seta on the first segment of the exopods of legs 1–4. The absence of such a seta is shared only with Maemonstrilla ( Grygier & Ohtsuka 2008) .

As in males of Monstrillopsis and Cymbasoma , but also in species of Monstrilla , the fifth legs are absent, but the extremely reduced genital complex diverges not only from those found in Monstrillopsis but from all other known monstrilloids for which males have been described ( Suárez-Morales & Dias 2001; Suárez-Morales et al. 2006; Suárez-Morales & Morales-Ramírez 2009; Suárez-Morales et al. 2013). This genital complex has some resemblance with that depicted for Monstrilla cf. helgolandica Scott, 1909 ( Huys & Boxshall 1991). The presence of a ventral process on the first post-genital somite is also a unique character; the ventral surface of all postgenital somites is always smooth. This kind of structure has not been described in any other monstrilloid; its function and/ or homology are intriguing. The urosome segmentation is similar to that found among males of Monstrillopsis , but the remarkably odd structure of the caudal rami with a massive size and bearing armed lobes is probably the most striking character of this genus; it strongly diverges from the usual pattern found among the Monstrilloida . The number of caudal setae, which is 5 in the new genus, falls within the range known in males of Monstrillopsis (4–6). The new genus is monotypic.