129
mentioned in this context. The fi rst pair was obviously
introduced to refl ect the position of the ooecium relative to
the frontal plane of the colony, whereas the second pair
refl ects the relation between the basal part of the ooecium
and the proximal part of the frontal wall of the distal
(ooecium- producing) zooid, i.e. the extent of the “common
wall” between them (see also Canu and Bassler 1920 ). Ryland
( 1968 ) was critical of “recumbent” as a term, but it still
appears in taxonomic descriptions. “Dependent” (the ovicell
fl oor is broad-based on the distal zooid, constituting a considerable part of its frontal wall; see, for instance, see Fig. 1 in
Introduction, 2.6a (A) and 2.22 ) and “independent” (ooecia
have a narrow base, with the ovicell fl oor either situated above
or constituting a small part of the frontal wall of the distal
zooid; see Figs. 2.3 , 2.5 , 2.7a (A), and 2.41 ) have not been
adopted, partly because the basal part of the ooecium is often
obscured by neighboring zooids, “secondary calcifi cation” or
both. It would be logical therefore to retain the well- known
term “hyperstomial” or its synonym “prominent (raised)” for
ovicells with ooecia of both types (1 and 2), in which half or
more of the spherical brood cavity appears above the colony
surface (Figs. 1.18A, B , 1.20E , 2.11A , 2.12D, E , 2.13 , 2.14A,
C–F , 2.15B , 2.16 , 2.17C, D , 2.19 , 2.22 , 2.23 , 2.26A, B ,
2.27A , 2.33A–D, F , 2.34 , 2.35A, B, D , 2.36 , 2.40A, B , 2.41 ,
2.42 , 2.43 , 2.44 , 2.45 , 2.48 , 2.49 , 2.63 , and 2.65 ).
When well-exposed terminal ovicells are positioned at the
edge of the colony, they could also be termed prominent or
hyperstomial despite the fact that more than half or even the
entire brood cavity may be situated below the colony surface,
corresponding to “subimmersed” and “immersed” ovicell
types (Figs. 1.25A , 1.27D , 1.28C , 1.30B , 1.32A, B , 1.36 ,
2.6a (D–F), b (A), 2.17B , 2.29 , 2.33D , and 2.60E ) (see also
illustrations in Levinsen 1909 ; Wass and Banta 1981 ). Most
of the “spinose” and “costate” ovicells recently described in
some fossil and Recent cheilostomes (Ostrovsky and Taylor
2004 , 2005a , Gordon and Taylor 2008 ) belong to the hyperstomial/prominent type (Figs. 2.10C–F , 2.54A–C , 2.57C, D ,
2.58A–E , 2.59C–E , 2.60A, B, D , and 2.61 ), although in
some species they show some degree of immersion (see for
instance Figs. 2.56 , 2.57A, B , and 2.60C ).
If less than half the brood cavity is above the colony surface, then the ovicell can be termed “subimmersed”
(Figs. 2.7a (F, G, I), 2.8F , 2.15A , 2.24 , 2.56 , 2.57A, B , and
2.60C ) (Hincks 1880 ; Ryland 1968 ). As is often the case
with transitional morphologies, this defi nition is not very
precise since, again, it is diffi cult to estimate the size of the
immersed part without sectioning. The term “subimmersed”
could be applied to all ovicells that are less prominent than
hyperstomial but more raised than immersed and endozooidal (that are “seated internally between two contiguous zooecia but as a rule chiefl y project[ing] into the bottom” of the
distal zooid (Levinsen 1902 , p. 11), and “enclosed in autozooecia” (Levinsen 1909 , p. 56)). In the latter two instances,
the entire or near-entire brood cavity is below the colony surface (Figs. 2.6b (B), 2.7a (H), and 2.7b (A, B)), whereas in
sub immersed types about one-third of the brood cavity is
above the colony surface (Figs. 2.7a (F, G, I) and 2.15A ).
Such ovicells are widespread among the Cheilostomata,
characterizing an evolutionary trend towards immersion of
the incubation chamber (Ostrovsky and Taylor 2004 ;
Ostrovsky et al. 2009a ). For instance, some calloporids and
cribrilinids possess both prominent (Figs. 2.13A , 2.19A, C ,
and 2.27A ) and subimmersed (Figs. 2.7a (I) and 2.15A )
ovicells, sometimes found in the same species ( Callopora
lineata , Puellina radiata ).
The terms “immersed” (Hincks 1880 ) and “endozooidal” [“endozooecial” of Levinsen ( 1902 , 1909 ), “entozooecial” of Harmer ( 1926 ) and “entozooidal” of Ryland
( 1970 ); modifi ed by Silén ( 1945 ) and Ryland ( 1968 )], are
often considered synonymous. However, it would be preferable, following tradition, to reserve “endozooidal” for
ovicells whose brood cavity is in the proximal part of the
distal zooid, as in many fl ustrids (Figs. 1.17 , 2.7b (A), 2.31 ,
and 2.32 ), some cribrilinids (Figs. 2.27B, C, E, G and
2.28 ) and eurystomellids (Fig. 2.7a (H)), and some catenicellids (Fig. 1.24A ) and candids (Fig. 2.30A ), and
“immersed” for those with the brood cavity in the distal
part of the maternal zooid as occurs in some microporids
(Fig. 1.28C, D ), cribrilinids (Figs. 2.6b (A) and 2.29 ),
eurystomelids (Fig. 2.6b (B)), calloporids (Figs. 2.7b (B)
and 2.25A ) and candids (Fig. 2.30B ) (see also Hastings
1945 for discussion). In both cases, the ooecium is level
with the colony surface or only very slightly above it.
Species of the cribrimorph genus Puellina possess prominent (Fig. 2.27A ), subimmersed (Fig. 2.7a (I)) and endozooidal ovicells (Figs. 2.27B, C, E, G and 2.28 ), sometimes
in the same species (Figs. 2.7a (I), 2.27A , and 2.28A ).
It should be stressed that, when viewed using SEM, ooecia
often appear more prominent in cleaned (i.e. bleached to
show the skeleton only) than non-cleaned colonies, which
retain their cuticularized surfaces (compare Fig. 2.14B, C ).
In addition, in many ascophorans the ovicell is transformed
in ontogeny from hyperstomial/prominent to subimmersed
depending of the degree of subsequent secondary calcifi cation (“ooecial” or “ovicellar cover”, or “secondary calcareous layer” in Levinsen 1909 , Ryland 1968 , Ryland and
Hayward 1977 ; Banta 1977 ; discussed in Zágoršek et al.
2011 ) (Figs. 2.7a (G), 2.8E, F , 2.40A, B , and 2.41A ). Thus,
varying degrees of ovicell immersion may be found in the
same colony. In extreme cases when the ovicell completely
“sinks” into a matrix of secondary calcifi cation, the term
“endozooidal” can be provisionally used, even though the
ooecium is immersed into the frontal shield of the distal
zooid, not its cavity (see Levinsen 1909 , pl. 24, fi g. 18;
Moyano 1968 , fi gs. 1.20, 1.23, 1.25; Carson 1978 , pl. 3, fi gs.
12, 14; Sandberg 1977 , pl. 6. fi g. 3).
2.2 Classifi cation and Terminology
mentioned in this context. The fi rst pair was obviously
introduced to refl ect the position of the ooecium relative to
the frontal plane of the colony, whereas the second pair
refl ects the relation between the basal part of the ooecium
and the proximal part of the frontal wall of the distal
(ooecium- producing) zooid, i.e. the extent of the “common
wall” between them (see also Canu and Bassler 1920 ). Ryland
( 1968 ) was critical of “recumbent” as a term, but it still
appears in taxonomic descriptions. “Dependent” (the ovicell
fl oor is broad-based on the distal zooid, constituting a considerable part of its frontal wall; see, for instance, see Fig. 1 in
Introduction, 2.6a (A) and 2.22 ) and “independent” (ooecia
have a narrow base, with the ovicell fl oor either situated above
or constituting a small part of the frontal wall of the distal
zooid; see Figs. 2.3 , 2.5 , 2.7a (A), and 2.41 ) have not been
adopted, partly because the basal part of the ooecium is often
obscured by neighboring zooids, “secondary calcifi cation” or
both. It would be logical therefore to retain the well- known
term “hyperstomial” or its synonym “prominent (raised)” for
ovicells with ooecia of both types (1 and 2), in which half or
more of the spherical brood cavity appears above the colony
surface (Figs. 1.18A, B , 1.20E , 2.11A , 2.12D, E , 2.13 , 2.14A,
C–F , 2.15B , 2.16 , 2.17C, D , 2.19 , 2.22 , 2.23 , 2.26A, B ,
2.27A , 2.33A–D, F , 2.34 , 2.35A, B, D , 2.36 , 2.40A, B , 2.41 ,
2.42 , 2.43 , 2.44 , 2.45 , 2.48 , 2.49 , 2.63 , and 2.65 ).
When well-exposed terminal ovicells are positioned at the
edge of the colony, they could also be termed prominent or
hyperstomial despite the fact that more than half or even the
entire brood cavity may be situated below the colony surface,
corresponding to “subimmersed” and “immersed” ovicell
types (Figs. 1.25A , 1.27D , 1.28C , 1.30B , 1.32A, B , 1.36 ,
2.6a (D–F), b (A), 2.17B , 2.29 , 2.33D , and 2.60E ) (see also
illustrations in Levinsen 1909 ; Wass and Banta 1981 ). Most
of the “spinose” and “costate” ovicells recently described in
some fossil and Recent cheilostomes (Ostrovsky and Taylor
2004 , 2005a , Gordon and Taylor 2008 ) belong to the hyperstomial/prominent type (Figs. 2.10C–F , 2.54A–C , 2.57C, D ,
2.58A–E , 2.59C–E , 2.60A, B, D , and 2.61 ), although in
some species they show some degree of immersion (see for
instance Figs. 2.56 , 2.57A, B , and 2.60C ).
If less than half the brood cavity is above the colony surface, then the ovicell can be termed “subimmersed”
(Figs. 2.7a (F, G, I), 2.8F , 2.15A , 2.24 , 2.56 , 2.57A, B , and
2.60C ) (Hincks 1880 ; Ryland 1968 ). As is often the case
with transitional morphologies, this defi nition is not very
precise since, again, it is diffi cult to estimate the size of the
immersed part without sectioning. The term “subimmersed”
could be applied to all ovicells that are less prominent than
hyperstomial but more raised than immersed and endozooidal (that are “seated internally between two contiguous zooecia but as a rule chiefl y project[ing] into the bottom” of the
distal zooid (Levinsen 1902 , p. 11), and “enclosed in autozooecia” (Levinsen 1909 , p. 56)). In the latter two instances,
the entire or near-entire brood cavity is below the colony surface (Figs. 2.6b (B), 2.7a (H), and 2.7b (A, B)), whereas in
sub immersed types about one-third of the brood cavity is
above the colony surface (Figs. 2.7a (F, G, I) and 2.15A ).
Such ovicells are widespread among the Cheilostomata,
characterizing an evolutionary trend towards immersion of
the incubation chamber (Ostrovsky and Taylor 2004 ;
Ostrovsky et al. 2009a ). For instance, some calloporids and
cribrilinids possess both prominent (Figs. 2.13A , 2.19A, C ,
and 2.27A ) and subimmersed (Figs. 2.7a (I) and 2.15A )
ovicells, sometimes found in the same species ( Callopora
lineata , Puellina radiata ).
The terms “immersed” (Hincks 1880 ) and “endozooidal” [“endozooecial” of Levinsen ( 1902 , 1909 ), “entozooecial” of Harmer ( 1926 ) and “entozooidal” of Ryland
( 1970 ); modifi ed by Silén ( 1945 ) and Ryland ( 1968 )], are
often considered synonymous. However, it would be preferable, following tradition, to reserve “endozooidal” for
ovicells whose brood cavity is in the proximal part of the
distal zooid, as in many fl ustrids (Figs. 1.17 , 2.7b (A), 2.31 ,
and 2.32 ), some cribrilinids (Figs. 2.27B, C, E, G and
2.28 ) and eurystomellids (Fig. 2.7a (H)), and some catenicellids (Fig. 1.24A ) and candids (Fig. 2.30A ), and
“immersed” for those with the brood cavity in the distal
part of the maternal zooid as occurs in some microporids
(Fig. 1.28C, D ), cribrilinids (Figs. 2.6b (A) and 2.29 ),
eurystomelids (Fig. 2.6b (B)), calloporids (Figs. 2.7b (B)
and 2.25A ) and candids (Fig. 2.30B ) (see also Hastings
1945 for discussion). In both cases, the ooecium is level
with the colony surface or only very slightly above it.
Species of the cribrimorph genus Puellina possess prominent (Fig. 2.27A ), subimmersed (Fig. 2.7a (I)) and endozooidal ovicells (Figs. 2.27B, C, E, G and 2.28 ), sometimes
in the same species (Figs. 2.7a (I), 2.27A , and 2.28A ).
It should be stressed that, when viewed using SEM, ooecia
often appear more prominent in cleaned (i.e. bleached to
show the skeleton only) than non-cleaned colonies, which
retain their cuticularized surfaces (compare Fig. 2.14B, C ).
In addition, in many ascophorans the ovicell is transformed
in ontogeny from hyperstomial/prominent to subimmersed
depending of the degree of subsequent secondary calcifi cation (“ooecial” or “ovicellar cover”, or “secondary calcareous layer” in Levinsen 1909 , Ryland 1968 , Ryland and
Hayward 1977 ; Banta 1977 ; discussed in Zágoršek et al.
2011 ) (Figs. 2.7a (G), 2.8E, F , 2.40A, B , and 2.41A ). Thus,
varying degrees of ovicell immersion may be found in the
same colony. In extreme cases when the ovicell completely
“sinks” into a matrix of secondary calcifi cation, the term
“endozooidal” can be provisionally used, even though the
ooecium is immersed into the frontal shield of the distal
zooid, not its cavity (see Levinsen 1909 , pl. 24, fi g. 18;
Moyano 1968 , fi gs. 1.20, 1.23, 1.25; Carson 1978 , pl. 3, fi gs.
12, 14; Sandberg 1977 , pl. 6. fi g. 3).
2.2 Classifi cation and Terminology