222
without necessarily killing it. In any case, all available evidence suggests a close
relationship of these gastropods to their host sponges. There are hints that they are
not obligate sponge eaters but it seems that sponges are the preferred source of food.
At least they belong, as Turridae and other gastropods, “in guilds of commensals,
associates and parasites” (Bouchet et al. 2009). It must be emphasized that feeding
observations are scarce covering few species so that generalizations must be considered with caution.
Triphoridae and Cerithiopsidae are small (usually <10 mm), high-spired or barrel shaped and commonly have a constricted body whorl in fully-grown specimens
(Fig. 6.5). The great majority of species in both families share a reticulate teleoconch ornament, commonly with asymmetrical knobby spiral cords that are rounded
and shallowly sloping anteriorly and steeply sloping posteriorly (Fig. 6.5c, h). This
represents probably a ratchet sculpture which facilitates penetration of the sponge
tissue and prevents uncontrolled back-slipping. Signor (1982) reported similar
ornaments for burrowing gastropods. Commonly cerithiopsids and triphorids have
a constricted body whorl and/or a rounded base resulting in an overall elongated
pear-shape which may have facilitated intrusion into the host sponge tissue
(Fig. 6.5a, d, e, g). Triphorids and Cerithiopsidae sensu strictu have a minimum
Paleogene age (see below).
Triphoridae
Triphoridae encompass at least 1000 living species, many of them undescribed.
Fernandes and Pimenta (2017) counted more than 600 recent species based on the
WORMS database (http://www.marinespecies.org/). Most species belong to the
sinistrally coiled subfamily Triphorinae. They have a complex aperture with an
anterior and a posterior siphonal canal, sometimes both are tube-like (Fig. 6.5d, e).
The posterior siphonal canal forms the outlet for special tentacles emerging form
the mantle cavity that may help to ventilate it (Nützel 1998). Triphoridae possess the
rhinioglossate radula—the number of teeth per row varies from 5 to 63 (Marshall
1983) (Fig. 6.6h).
Undoubted sinistrally coiled Triphoridae (Triphorinae) are present since the
Danian (e.g., Ravn 1933; Nützel 1998; Wesenberg and Schnetler 2014) (Fig. 6.5d)
and few Late Cretaceous forms have been reported but those need confirmation
(e.g., Kaunhowen 1897; Nützel 1998; Kaim 2004).
Cerithiopsidae
Cerithiopsidae is another highly diverse family of spongivorous small, high-spired
caenogastropods. Cerithiopsidae may closely resemble non-parasitic small
Cerithioidea for instance the genus Bittium and protoconch morphology is needed
to separate both groups. However, protoconch preservation is rare, especially in fossil gastropods (e.g., Nützel 2014). Cerithiopsidae are taenioglossate having seven
A. Nützel
without necessarily killing it. In any case, all available evidence suggests a close
relationship of these gastropods to their host sponges. There are hints that they are
not obligate sponge eaters but it seems that sponges are the preferred source of food.
At least they belong, as Turridae and other gastropods, “in guilds of commensals,
associates and parasites” (Bouchet et al. 2009). It must be emphasized that feeding
observations are scarce covering few species so that generalizations must be considered with caution.
Triphoridae and Cerithiopsidae are small (usually <10 mm), high-spired or barrel shaped and commonly have a constricted body whorl in fully-grown specimens
(Fig. 6.5). The great majority of species in both families share a reticulate teleoconch ornament, commonly with asymmetrical knobby spiral cords that are rounded
and shallowly sloping anteriorly and steeply sloping posteriorly (Fig. 6.5c, h). This
represents probably a ratchet sculpture which facilitates penetration of the sponge
tissue and prevents uncontrolled back-slipping. Signor (1982) reported similar
ornaments for burrowing gastropods. Commonly cerithiopsids and triphorids have
a constricted body whorl and/or a rounded base resulting in an overall elongated
pear-shape which may have facilitated intrusion into the host sponge tissue
(Fig. 6.5a, d, e, g). Triphorids and Cerithiopsidae sensu strictu have a minimum
Paleogene age (see below).
Triphoridae
Triphoridae encompass at least 1000 living species, many of them undescribed.
Fernandes and Pimenta (2017) counted more than 600 recent species based on the
WORMS database (http://www.marinespecies.org/). Most species belong to the
sinistrally coiled subfamily Triphorinae. They have a complex aperture with an
anterior and a posterior siphonal canal, sometimes both are tube-like (Fig. 6.5d, e).
The posterior siphonal canal forms the outlet for special tentacles emerging form
the mantle cavity that may help to ventilate it (Nützel 1998). Triphoridae possess the
rhinioglossate radula—the number of teeth per row varies from 5 to 63 (Marshall
1983) (Fig. 6.6h).
Undoubted sinistrally coiled Triphoridae (Triphorinae) are present since the
Danian (e.g., Ravn 1933; Nützel 1998; Wesenberg and Schnetler 2014) (Fig. 6.5d)
and few Late Cretaceous forms have been reported but those need confirmation
(e.g., Kaunhowen 1897; Nützel 1998; Kaim 2004).
Cerithiopsidae
Cerithiopsidae is another highly diverse family of spongivorous small, high-spired
caenogastropods. Cerithiopsidae may closely resemble non-parasitic small
Cerithioidea for instance the genus Bittium and protoconch morphology is needed
to separate both groups. However, protoconch preservation is rare, especially in fossil gastropods (e.g., Nützel 2014). Cerithiopsidae are taenioglossate having seven
A. Nützel