**2. Materials and methods**

to commence its benthic life immediately after hatching. (2) Lecithotrophic development in which, after hatching, the larva spends from a few minutes to several days as a veliger without feeding or growing. (3) Planktotrophic development, in which the larva hatches as a veliger and spends a few days to several months in the planktonic mode of life during which it feeds and grows [1]. In all cases, a larval shell is formed which is called

The size of fossilized early protoconches suggests that feeding (planktotrophic) embryos first appeared at the transition from the Cambrian era to the Ordovician as Ordovician protoconches were smaller than Cambrian ones indicating smaller Ordovician eggs and offspring. It is believed that planktotrophy would prolongate their escape from benthic predators and that an increasing nutrient supply and availability of photoautotrophic plankton in the world oceans of that period have facilitated both planktotrophy and suspension feeding [2]. The eventual loss of planktotrophy in the Pliocene has been documented in some taxa of Conoidea (*Raphitoma*, *Bela*) and is believed to be irreversible [3]. The same phenomenon has occurred in the families such as Cerithiidae (*Bittium*), Turritellidae (*Turritella*), Rissoidae (*Rissoa*, *Pusillina*),

Planktotrophic mode of life with long-living planktonic larvae is considered advantageous in the dispersal of the larvae as they may drift considerable distances with the currents [6, 7]. In addition, it has been demonstrated that the switch in some conoidean taxa from the planktotrophic to the non-planktotrophic development has increased their adaptive radiation, especially in polar or insular region, or in groups with narrow bathymetric distribution [3, 7]. In the case of *Oenopota elongata* Bogdanov, 1989, and in the polar genus or bathyal Indo-Pacific genus *Bathytoma* Harris & Burrows, 1891, the loss of planktotrophy actually preceded

Within the Neogastropoda, Conoidea is a diverse superfamily of venomous and exclusively marine gastropods which harbors more than 300 genera, 4000 known species, and an estimated number of over 12,000 existing species [3, 12, 13]. Due to the species richness and the extensive homoplasy among shell's features and the anterior alimentary system, they have resisted repeated attempts to be permanently classified with those attempts to be hindered primarily by the absence of a stable phylogenetic framework. Rather recently, DNA analysis provided an updated classification and divided the superfamily of Conoidea into 13 families [14–16]. Among them, the position of Raphitomidae is not sufficiently secured as a clade of Conoidea and for that reason there has been an on-going attempt to clarify the phylogeny of its Mediterranean members through a greater number of taxonomic data [17, 18]. These later publications have taken into account the pioneering works of Thorson [19, 20], concerning the relationship between the morphology of the protoconch and the type of the larval development in Caenogastropoda, e.g., the dichotomy "multispiral protoconch/planktotrophic development" and "paucispiral protoconch/lecithotrophic development" that has been widely accepted [6, 21]. Although some authors have used this dichotomy to divide species into planktotrophic genera and non-planktotrophic ones [3, 22, 23], it has been clearly demonstrated that such a division based exclusively on the morphology of the protoconch produces

protoconch.

24 Organismal and Molecular Malacology

and Nassariidae (*Nassarius*) [4, 5].

adaptive radiation [8–11].

Sampling of gastropods specimens was conducted from October 2008 to October 2016 in certain locations of Greece, according to Manousis and Galinou-Mitsoudi [30]. The *Raphitoma* species recognition was based on (a) systematic guides and atlases [23, 31–38], (b) faunistic and review articles [39, 40], (c) studies on the Mollusca fauna in the Hellenic seas [30, 41–47]. Information from specific websites was also taken into account. For the species nomenclature update (31 December 2016), besides the Marine Biodiversity and Ecosystem Functioning EU Network of Excellence (MarBEF, www.marbef.org) and the World Register of Marine Species (WoRMS, http://www.marinespecies.org), the Taxonomic on-line Database on European Marine Mollusca (CLEMAM, www.somali.asso.fr,) was followed. In addition, the Ellenic Network on Aquatic Invasive Species (ELNAIS, https://services.ath.hcmr.gr, 31 December 2016) and the Marine Mediterranean Invasive Alien Species database (MAMIAS, http:// mamias.org/taxonomicgroup.php) were used for the status of possible alien species in the Hellenic and Mediterranean seas. Protoconch whorls were counted according to Verduin [48]. The measurement of the protoconch maximum diameter was performed at top view according to Gofas and Oliver [49]. The shell's slenderness (h/w) was estimated including the outer lip of the aperture in the shell's width. The protoconch I maximum diameter deriving after each hypothetical additional cleavage of the stem cells was calculated by multiplying measured maximum diameter of the lecithotrophic protoconch of each, so-called, sibling species by the approximate factor of 0.7937 receiving as a fact that each stem cell is a sphere that divides into two equal spheres at cleavage.

The specimens are deposited in the premises of the Alexander Technological Educational Institute of Thessaloniki and those of Dr T. Manousis, Mr Constantinos Kontadakis, Mr George Mbazios and Mr Georgios Polyzoulis. Scientists are welcome to have access to the biological material at will.
