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BULLETIN OF MARINE SCIENCE. 46(3): 688-700. 1990
A NEW "LIVING FOSSIL" ECHINOID (ECHINODERMATA)
AND THE ECOLOGY AND PALEOBIOLOGY OF
CARIBBEAN CASSIDULOIDS
Rich Mooi
ABSTRACT
A new Recent species of cassiduloid echinoid, Eurhodia relicta. is described and illustrated
from two specimens collected off Venezuela and Surinam. E. relicla is the only known living
member of a genus formerly thought to have become extinct in the Late Eocene, and most
closely resembles the higher·-tested species of the southeastern North American and Caribbean
fossil genus Eurhodia. Previously described criteria used to distinguish between the fossil
cassidulids Eurhodia. Cassidu/us. and Rhyncho/ampas are not sufficiently diagnostic when
they are also applied to the Recent type species of these genera. Soft tissue and/or petaloid
characters must also be employed. A review of the ecology of Caribbean cassiduloids indicates
that
Eurhodia
burrows in terrigenous substrates, that
Echinolampas
and
Cassidulus
burrow
in carbonates, and that Cono/ampas is an epifaunal, deeper water form living on relatively
fine carbonates. The distributions of living Caribbean cassiduloids are mapped along with
fossil localities for New World Eurhodia species. The occurrence of Recent Eurhodia in the
southern Caribbean might be related to the same factors causing the existence of relict faunas
from the northern coast of South America.
In his review of the concept of "living fossils," Schopf (1984: 272) listed six
definitions that previous authors have used in recognizing such taxa. After dis-
cussing the various merits of these definitions, he suggested a seventh: "A relatively
little morphologically modified representative of a relatively archaic lineage with
little modem representation." This last definition emphasizes the two main fea-
tures of most previously described "living fossils": relatively little morphological
change over geological time, and extinction of most known closely related taxa.
In spite of the interpretive scope afforded by Schopfs wording, I would suggest
that when all the previously known taxa in a speciose clade of organisms have
been described only from Eocene deposits, the label "living fossil" could be
reasonably applied to any living species later placed in that clade. Such is the case
for the new cassiduloid described in the present paper. Schopfs seventh sum-
marizing criterion is of primary importance in a cladistic and ecological sense
because the extinction of other members of the clade to which the "relatively
little morphologically modified" Recent species belongs suggests special reasons
for the persistence of living cassiduloids.
The order Cassiduloida (sensu Kier, 1962) consists of burrowing irregular echi-
noids typically possessing a relatively high test, short spines, a posteriorly displaced
periproct, and well-developed circum-oral spine-bearing regions (bourrelets) ad-
jacent to the mouth. Although abundant as Mesozoic and Cenozoic fossils, cas-
siduloid species have dramatically declined in number since the Eocene (Kier,
1974; Suter, 1988)-only 30 species have survived to the present (Mooi, 1990).
Five species are known to occur in the Americas; three of these commonly occur
in the Gulf of Mexico and the Caribbean:
Echinolampas depressa
Gray, 1851,
Conolampas sigsbei
(A. Agassiz, 1878), and
Cassidulus caribaearum
Lamarck,
1801. There are very few recent works deaiing with the biology and distribution
of Recent cassiduloids (but see Cram, 1971; Thurn and Allen, 1975; 1976; Higgins,
1974; Baker, 1983), and even fewer (Gladfelter, 1978; Serafy, 1979) are specifically
concerned with cassiduloids of the Americas.
688
MOOI: A NEW "LIVING FOSSIL" CASSIDULOJD
689
During a survey of the cassiduloid material at the United States National Mu-
seum of Natural History (USNM), Washington, D.C., two specimens previously
identified as
Cassidulus caribaearum
and dredged by the R/V PILLSBURYfrom
over 50 m off the northern coast of South America were found. C.
caribaearum
usually occurs at depth of less than 2 m, typically burrowed in coarse sand at the
foreslope of protected beaches in lagoons (Gladfelter, 1978; Telford and Mooi,
in prep.). A detailed examination revealed that the two specimens were unlike
any known living species, and belonged to no known living genus. Examination
of fossil material and the paleontological literature suggested that the specimens
were actually members of the genus
Eurhodia,
commonly found in Europe, Africa,
India, Pakistan, and the Americas as Paleocene or Lower Eocene fossils. Ap-
proximately 13European, Asian, and African species have been assigned to
Eurho-
dia
(Lambert and Thiery, 1909; Roman and Gorodiski, 1959), and the genus is
particularly well-represented in Late Eocene strata of the southeastern U.S. and
the Caribbean by another 7 species (Sanchez Roig, 1951; Kier, 1980; Carter and
Beisel, 1987). In this paper, I describe the new Recent species of
Eurhodia,
com-
pare it with the known American fossil material of this genus, and comment on
the status of the new species as a "living fossil." I also review the criteria used
by Carter and Beisel (1987) to distinguish among
Eurhodia, Cassidulus,
and
Rhyn-
cholampas
in order to assess their applicability to the Recent type species of the
latter two genera, and the new species of
Eurhodia.
The biology and habitat
preferences of the known living Caribbean cassiduloids are compared.
MATERIALSANDMETHODS
Museum Material. - The following Recent material was examined from the collections at the USNM,
the Museum of Comparative Zoology, Harvard (MCZ), and the Museum National d'Histoire Naturelle
(MNHN) (catalogue numbers in parentheses): Cassidulus caribaearum Lamarck, 1801 (USNM E13765,
E13755, E18703, E18705, E29508, E34329, E36116-E36125, E36150, E37102), Eurhodia relicta sp.
nov. (USNM E20480, EI2971), plus all the USNM material of Rhyncholampas pacificus (A. Agassiz,
1863), Echinolampas depressa Gray, 1851, and Conolampas sigsbei (A. Agassiz, 1878). Data were
also collected from the Indo-Pacific species Oligopodia epigonus (van Martens, I865)(USNM E 16309,
E34026, E35684, E35877; MCZ 2697; MNHN EcEkll). The following USNM fossil material was
examined: Eurhodia holmesi (Twitchell, 1915) (562203,264048,264049,264592,353256, plus seven
collections of uncatalogued E. holmesi from the Springer Room's Biologic Set), Eurhodiaelbana Cooke,
1942 (Holotype, 498981), and Eurhodia matleyi (Hawkins, 1927) (uncatalogued, U.S. Geological
Survey number 18710, Eocene of Jamaica).
Behavioral. Bathymetric, and Biogeographic Data. -Observations and collections of Cassidulus cari-
baearum were made in the spring of 1986 at Loblolly Bay, Anegada, British Virgin Islands. Gut
contents and substrate found associated with Recent Caribbean museum material of Echinolampas
depressa and Conolampas sigsbei were qualitatively assessed for carbonate content, particle size, and
foraminiferal content. Bathymetric and geographic ranges of Recent and fossil cassiduloids in the Gulf
of Mexico and the Caribbean were determined from collection data for museum specimens, and from
the literature.
Measurements. - The following measurements were taken to the nearest 0.1 mm from Eurhodia and
Cassidulus specimens: test length, width, height; apical system position (from the anterior edge of the
test to the anterior edge of the madreporic plate); peristome length, width, position (from the anterior
edge of the test to the anterior edge of the peristome); periproct width, position (from the anterior
edge of the test to the posterior edge of the hood over the periproct); petaloid lengths, widths.
External Appendages and Test Morphology. -Individual spines and pedicellariae were removed from
the test of the holotype of Eurhodia relicta. and compared with those from Cassidulus caribaearum.
Appendages removed from these species were placed in a droplet of 2% sodium hypochlorite solution
(bleach) on a microscope slide. Using a compound microscope equipped with a camera lucida. the
cleaned skeletal elements were then examined and drawn. Sphaeridia, and spicules from a small portion
of the peristomial membrane were drawn using the same procedure. Sutural patterns and podial pores
were made visible for mapping with a camera lucida mounted on a dissecting microscope by lightly
690
BULLETIN OF MARINE SCIENCE, VOL. 46, NO.3, 1990
brushing the test with a solution made of equal parts of glycerol and absolute ethanol. Terminology
for appendages and test morphology is that of Mooi (1989).
SYSTEMATICACCOUNT
Order CASSIDULOIDA Claus, 1880
Family Cassidu1idae L. Agassiz and Desor, 1847
Eurhodia Haime in d'Archaic and Haime, 1853
Eurhodia relicta new species
Figures 1-4
Diagnosis. - Small (less than 15 mm in length) cassiduloid echinoids with rela-
tively highly domed test. Periproct slightly hooded, almost invisible in top view;
almost vertical, shallow trough (anal sulcus) leading adorally from adoral edge of
periproct. Peristome longer than wide, slightly anterior, with almost vertical sides
and bourrelets leading upwards to slightly sunken mouth. Distinctive, pitted,
naked zone on oral surface; very prominent and wide in interambulacrum 5, but
narrower and shorter in ambulacrum III. Petaloids slightly reduced, with fewer
than 40 pore pairs in each. Outer pore of each respiratory pore pair round, or
only slightly elongate;
a
and
b
columns of respiratory podia of each petaloid
approximately equal in length. Phyllodes with 7 to 10 pores in outer series, 2 or
3 in inner series. Very few (no more than 6) hydropores in madreporic plate.
Spine-bearing tubercles on oral surface not especially enlarged. No spicules in
podia.
Type Locality. - Continental shelf off the northern coast of South America. The
holotype was dredged from 57 m depth at 07°42'N x 57°32'W, off Surinam, and
the paratype from 112 m depth at 11°00'N x 65°55'W, off Venezuela.
Type Material. - Holotype (USNM E20480) and a single paratype (USNM E12971),
dry specimens deposited in the National Museum of Natural History, Smithsonian
Institution, Washington, D.C. Although MCZ and MNHN collections were ex-
amined, these two specimens, dredged by the R/V PILLSBURYin July, 1968,
constitute the entire known material of Eurhodia relicta.
Etymology. -L. relictus ="abandoned," in reference to the fact that this is the
only known living species of a genus formerly thought to have disappeared from
the Americas before the end of the Eocene.
Description. - In the following description all linear measurements are given as
percentages of test length (L). When measurements or meristics are given, the first
figure refers to the holotype, and the figure in parentheses to the paratype.
GENERALTESTCHARACTERISTICS.The test length of the holotype (Fig. 1A,
B)
is 12.5 mm, that of the paratype is 13.2 mm. At 93.6% L (90.2), the test of the
new species is relatively wide in comparison to the majority of its congeners, and
forms a high arch when viewed from the posterior end (Fig. 2D). This species
appears to be variable in height, 57.6% L (70.5), with the highest point occurring
at the apical system.
APICALSYSTEM.The apical system is monobasal, and consists of a madreporic
plate pierced by 5 or 6 hydropores (Fig. 2A) that is accompanied by five small
ocular plates, each of which is perforated by a small but prominent terminal pore.
The apical system of the holotype has four gonopores, but the para type appears
to have lost the gonopore in interambulacrum 4, possibly through injury when
juvenile. The anterior edge of the madreporite is 36.0% L (28.8) from the anterior
edge of the test.
MOO!: A NEW "LIVING FOSSIL" CASSIDULO!D 691
Figure 1. Eurhodia relicta new species: (A) Aboral surface of holotype, USNM E20480; (B) Oral
surface of holotype showing naked zone posterior to peristome. Scale bars are 5 mm long.
AMBULACRA.The petaloids are very narrow (Fig. lA, 2A). Petaloid III is 12.8%
L
(12.1), peta10ids II and IV are 12.0%
L
(11.4), and peta10ids I and V are 10.4%
L
(9.8) in width. In all petaloids, the interporiferous zone is as wide as, or slightly
narrower than a single poriferous zone. The length of petaloid III is 23.2%
L
(22.0), petaloids II and IV are 21.6%
L
(22.7), and petal aids I and V are 29.6%
L
(31.1). There is a total of 23 (26) respiratory podial pore pairs in petaloid III,
19 (24) in petaloid II, and 25 (35) in petaloid I. The aand
b
columns of respiratory
podia in each petaloid are approximately equal in length, with the difference in
number of pore pairs in the aand bcolumns never exceeding one. The pore pair
of each respiratory podium is conjugated by a shallow groove, and the outer pore
of each pore pair is round, or only slightly elongated. The ambulacra adoral to
the ends of the petaloids are also very narrow, with a single accessory podia1 pore
at the adoral edge near the adradial suture of each ambulacral plate (Fig. 2A-D).
No spicules could be found in the podia that originate from these pores. There
are 7 to 10 phyllopores in the outer series of each phyllode, with 2 to 3 phyllopores
in the inner series, one pore occurring in each ambulacral plate near the peristome
(Fig. 2B). There is a single buccal podial pore in each ambulacral basicoronal
plate. Three to 5 sphaeridia (Fig. 31) occur in each ambulacrum in shallow pits
near the perradial suture just adapical to the ambulacral basicoronals.
INTERAMBULACRA.The interambulacra are extremely wide at the ambitus (Fig.
2A-D), but narrow to a double row of very small, staggered plates adjacent to
the apical system. The bourrelets are prominent, but form only slight bulges into
the peristome. Each bourrelet occurs on the adoral portion of an interambulacral
basicoronal plate, and bears more than 25 closely spaced tubercles, each of which
supports a strongly curved circumoral spine (Fig. 3C).
PERISTOME.The anterior edge of the peristome is 37.6%
L
(37.9) from the
anterior edge of the test. The peristome is longer than wide, its length being 12.0%
L
(11.4), and its width 9.6%
L
(9.1). The mouth is located at the end of a shallow,
692
BULLETIN OF MARINE SCIENCE, VOL. 46, NO.3, 1990
Figure 2. Plate patterns on the holotype, USNM E20480, of Eurhodia re/ieta new species: (A) Aboral
surface; (B) Oral surface; (C) Left side; (D) Posterior end. Scale bar in
mm,
but steep-sided infundibulum, and is surrounded by a thin peristomial membrane
in which are embedded evenly distributed, lobulated spicules (Fig. 3H).
PERIPROCT.
The periproct is 18.4%, L (16.7) in width, and is partially obscured
from above by a very slight aboral hood that overhangs the top edge of the
periproct (Fig. 2C). The test under the hood and around the periproctal membrane
supports long, tapered spines (Fig. 3B). Below the periproct is a shallow, almost
vertical trough, or anal sulcus that leads from the adoral edge of the periproct to
the ambitus (Figs. lA, 2B, D). The periproctal plates are distributed in two regions
(Fig. 4A), an aboral zone of very small plates bearing few spines, and an adoral
zone of larger plates that support a total of 4 or 5 primary spines, numerous
miliary spines, and large tridentate pedicellaria.
NAKED ZONE. There is a conspicuous region almost denuded of spines running
along the midline of the oral surface of the test, anterior and posterior to the
peristome in ambulacrum
III
and interambulacrum 5 (Fig. IB), and partially
invading the regions aboral to the basicoronal plates in interambulacra I, 2, 3,
and 4. There are irregularly arranged, occasionally quite deep pits in the test
underlying this zone that appear to represent greatly reduced spine tubercles.
SPINES.
Although largely denuded, the holotype still possesses a few isolated
patches of spines, particularly around the peristome and periproct. The miliary
spines of the aboral surface are approximately 400
#Lm
long, and terminate in a
slight crown typical of the miliaries of other cassidulids (Fig. 3A). Judging from
its bleached appearance, wear on the spine tubercles, and the presence of a small
MOO!: A NEW "LIVING FOSSIL" CASSIDULOID 693
A
B
C
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500
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Figure 3. External appendages of the holotype, USNM E20480, of Eurhodia relicta new species:
(A) Miliary spine from aboral surface; (B) Primary spine from just under hood, near periproct; (C)
Circumoral spine from bourrelet, near peristome; (D) Large tridentate pedicellaria from periproctal
plate; (E) Single valve oftriphyllous pedicellaria from just under hood, near periproct; (F) Single valve
of tridentate pedicellaria depicted in (D); (G) Stem of triphyllous pedicellaria from just under hood,
near periproct; (H) Spicules from peristomial membrane, natural grouping; (I) Sphaeridium from pit
in ambulacrum V. All scale bars in ~m.
polychaete worm tube on the test, the paratype was dead long before collection,
and bears no spines.
PEDICELLARIAE.Two types of pedicellariae were found on the holotype. Around
the periproct, and on the periproctal plates, there is a very large form ofpedicellaria
consisting of tridentate jaws mounted via a very short neck on a short, thick stalk
(Fig. 3D). The individual valves of the jaw are approximately 150
J.Lm
long, and
bear fine teeth on their distal edges (Fig. 3F) that interdigitate with those on
adjacent valves. The second form of pedicellaria is triphyllous, with very short,
wide valves bearing long, comblike distal serrations (Fig. 3E). The serrations of
these pedicellariae also interdigitate with those on adjacent valves in a manner
typical for triphyllous pedicellariae of irregular echinoids. Each set ofthree valves
is mounted on a slender, 150
J.Lm
long stalk (Fig. 3G) via a long neck that is
approximately the same length as the stalk. Through comparison with other cas-
sidulids, ophicephalous pedicellariae should occur in E. relicta, although none
could be found on the partially denuded holotype. Intrafamilial comparison also
suggests that globiferous pedicellariae will not be found on this species.
REMARKS
Family Placement and Characterization oj the Genus Eurhodia.
-Kier (1962)
created the family Pliolampadidae for the type genus Pliolampas Pomel, 1888,
Eurhodia, and 10 other genera of uncertain affinities. He suggested that the "Plio-
lampadidae are not very homogeneous and may not represent a natural or phy-
logenetic grouping," and noted that pliolampadids differed from other families
694
BULLETIN OF MARINE SCIENCE, VOL. 46, NO.3, 1990
A
I!,
~~~~§jiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii~~~~~iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii~~~~~,
o
5
Figure 4. Periproctal plate patterns of cassiduloids: (A) Eurhodia relicla new species, holotype, USNM
E20480, 12.5 mm long;
(B)
Cassidulus caribaearum
Lamarck, specimen 12.7 mm long. Primary spines
are indicated by two concentric circles, miliary spines by a single open circle. Anal opening in solid
black. Scale bar in mm.
such as the Echinolampadidae and Cassidulidae in part by lacking " ... a narrow,
naked, granular zone in interambulacrum 5 (except in Ilarionia and some species
of Gitolampas)" (p. 192). Curiously, he did not also cite Eurhodia as an exception
to this supposed diagnostic feature. All New World members of the genus Eurhodia
are characterized by a strongly developed, pitted, naked zone on the medial portion
of the oral surface. Eurhodia also differs from most other genera that Kier places
in the Pliolampadidae in having the periproct on the aboral surface or at the
ambitus, always in a shallow anal sulcus. Kier's (1962) assignment of Eurhodia
to the Pliolampadidae seems to be based largely on the tendency towards elon-
gation of the peristome, and perhaps on overall test shape.
Of all the cassiduloid families, Eurhodia most closely fits the description of the
Cassidulidae. Past difficulties in correct placement of some species in either Eurho-
dia or Cassidulus testifies to the similarity between the genera (see Cooke, 1961).
However, the tests of species of Eurhodia can be distinguished from those of
Cassidulus in two major ways. First, in Eurhodia, the aand bcolumns of respi-
ratory podia in the petaloids contain approximately the same number of pore
pairs. If the numbers in each column differ, they do so only by one. In Cassidulus,
the aand bcolumns of respiratory podia in each petaloid differ significantly in
length, with the difference in number of pore pairs in the two columns exceeding
5 or 6 in some cases. This inequality is most conspicuous in the posterior paired
ambulacra (I and V). Second, the peristome of Eurhodia is usually longer than it
is wide. That of Cassidulus is wider than it is long. Carter and Beisel (1987) have
cast doubt on the reliability of peristomial elongation as a feature distinguishing
between these genera. Instead, they cite Eurhodia's large, deep pits in the naked
zone, longitudinal depression on the oral surface, large phyllodes, and large, sunken
oral tubercles. Although these features work reasonably well for the fossil taxa
Carter and Beisel (1987) examined, Cassidulus caribaearum and Rhyncholampas
pacificus (both type species of their genera) have prominent pits in the naked
zone, enlarged, sunken locomotory spine tubercles, and an oral, longitudinal
depression. The phYllodes in C. caribaearum are small, but those of R. pacificus
are as well-developed as in most species of Eurhodia. Carter and Beisel's (1987)
preferred characters must therefore be used with caution.
MOOI: A NEW "LIVING FOSSIL" CASSIDULOID 695
Living species of
Eurhodia
and
Cassidulus
are easily identified now that some
ofthe external appendages and soft tissue structures ofa living species ofa Recent
Eurhodia
have been described.
E. relicta
differs from
Cassidulus caribaearum
in
having a relatively large region of small plates in the periproctal membrane, and
relatively few primary spines in the larger plates in the more adoral region of the
periproct (Fig. 4A). C.
caribaearum
has approximately twice as many large plates
bearing many primary spines in the adoral zone of the periproctal membrane,
and much fewer small plates (Fig. 4B). The periproct is also relatively small in
Eurhodia
in comparison with that of
Cassidulus.
The large tridentate pedicellariae
from the periproctal region of
E. relicta
are similar to those of C.
caribaearum,
but the valves of the triphyllous pedicellariae of the former (Fig. 3E) are wider
relative to length than those of the latter (Mortensen, 1948: pI. XI, fig. 9), and
have fewer teeth. In this respect, the triphyllous pedicellariae of
E. relicta
are
much more like those of
Oligopodia epigonus
(Mortensen, 1948: pI. XII, fig. 14)
than those of
Cassidulus.
Aboral primary spines are unknown for
E. relicta,
but
the miliary spines appear to be typical for members of the Cassidulidae. The
spicules from the peristomial membrane of
E. relicta
are very different from those
of C.
caribaearum.
In the former, they are small (seldom greater than 40 ~m in
greatest linear dimension) compact and lobulated (Fig. 3H), whereas in the latter,
the spicules are relatively large (often greater than 100 ~m in greatest linear
dimension), with an open trabecular structure consisting of branches (Mortensen,
1948: 208, fig. 182a) and sometimes closed loops. Usually, there are two or three
spicules in the suckers of respiratory podia of C.
caribaearum,
but these were not
detected in the podia of
E. relicta.
Species Similar to
Eurhodia relicta.-Cooke (1959) recommended retention of
Gisopygus
Gauthier, 1899, as a subgenus of
Eurhodia,
and placed
E. holmesi
in
this subgenus. Cooke suggested this because of a lack of intermediates between
the elongate, somewhat flattened test of most species of
Eurhodia,
and the rela-
tively short, high test of
E. holmesi.
Neither Mortensen (1948) nor Kier (1962)
employ the subgenus
Gisopygus
in their monographs, nor does Kier (1980) rec-
ognize it in his treatment of fossils from the Santee and Castle Hayne limestones.
I do not advocate splitting of
Eurhodia,
but if evidence for division is ever found
(or if
Gisopygus
is elevated to the genus level) both
E. holmesi
and
E. relicta
should be referred to
Gisopygus.
E. relicta
differs from
E. holmesi
in being smaller, and in having narrower
petaloids, much narrower interporiferous zones, and fewer respiratory podia.
E.
relicta
is also similar to
E. matleyi
from the Eocene of Jamaica and
E. corralesi
Sanchez Roig, 1951, from the Eocene of Cuba in some aspects of test shape, but
the latter two species have narrower tests, and considerably larger petaloids than
E. relicta. E. elbana,
a poorly known species represented only by a badly damaged
holotype from the Eocene of Alabama, resembles
E. relicta,
but in
E. elbana,
the
peristome is at least as wide as it is long. This observation led Cooke (\ 959: 64)
to doubt the correct generic assignment of
E. elbana,
noting that its "equilateral
peristome distinguishes it from other species of
Eurhodia."
Using their new cri-
teria, Carter and Beisel (1987) believe that
E. elbana
is a
Cassidulus,
but my
examination of the holotype suggests that the petaloid columns are equal in length
like those of
Eurhodia. E. relicta
is much wider and higher than
E. trojanus,
which
is more like
Cassidulus
in petaloid column inequality (Cooke, 1959: pI. 24, fig.
1) than any
Eurhodia.
This, and other problems cited in the generic comparison
above suggest that re-examination of Carter and Beisel's (\ 987) characters with
respect to type species of
Cassidulus
and
Rhyncholampas
is much needed before
696
BULLETIN OF MARINE SCIENCE, VOL. 46, NO.3, 1990
problematic fossils such as
Eurhodia elbana
and
Eurhodia trojanus
(sensu Carter
and Beisel, 1987) can be correctly placed.
There is an intriguing similarity between
E. re/icta
and
O/igopodia epigonus,
a
cassiduloid occurring in the southwest Pacific and Indian Oceans. Both species
have a globose test, somewhat reduced petaloids, few hydropores, a periproct in
a shallow, almost vertical sulcus, an elongate peristome, and small, lobulated
peristomial membrane spicules. As noted above, there are also some similarities
in pedicellarial morphology. In fact,
E. re/icta
and
O. epigonus
are so similar that
additional material of these species might demonstrate that they are congeneric.
If synonymized, the genus
Eurhodia
Haime, 1853, has priority over
O/igopodia
Duncan, 1889, and
O. epigonus
would be another "living fossil" species of
Eurho-
dia.
I am currently revising the systematics of the living cassiduloids, and it is
premature to revise these genera without a rigorous phylogenetic analysis, which
is beyond the scope of this paper.
E. re/icta
differs from
0, epigonus
in having a
slightly more pronounced naked zone, and in having a periproct that is wider
than high.
DISCUSSION
General Biology of Caribbean Cassiduloids.
-Carter et al. (1989) felt that fossil
Eurhodia,
particularly the flattened forms, might have inhabited substrates with
substantial mud content, without burrowing completely. The higher-tested
E.
re/icta
appears to be like most other cassiduloids (Higgins, 1974; Gladfelter, 1978),
burrowing into relatively coarse sand, swallowing smaller substrate particles, and
digesting the organisms living in and on them.
E. re/icta
inhabits sediments with
high siliceous content (Fig.
sq,
judging from the quartz grains associated with
the holotype. This is consistent with the observation that much of the continental
shelf substrate of northern South America is of terrigenous origin (Petuch, 1981).
E. re/icta
occurs at depths greater than SOm, in relatively cool (less than 22°C,
R/V
OREGONstation data), offshore waters. This habitat is in sharp contrast to
that of
Cassidulus,
the only other living genus of cassidulid from the Caribbean.
Observations made at Anegada indicate that
Cassidulus
inhabits warm, shallow
water, burrowing into carbonate substrates with high oolitic content that occur
on the edges of beaches in lagoons (Fig. SA).
Echinolampas depressa
and
Conolampas sigsbei,
the two other known living
species of cassiduloid in the Caribbean, are usually collected by dredging, or by
deep sea submersible.
E. depressa
is typically found at depths of 30 to over 310
m. C.
sigsbei
inhabits slightly deeper water, from over 120 m to 800 m. Few direct
field observations of these species exist, although substrate collected with the
specimens and in their guts suggests that
Echinolampas
lives in relatively coarse
carbonate sand composed largely of coralline and algal fragments. Gut contents
of museum specimens support Mortensen's (1948) suggestion that
Echinolampas
feeds largely on foraminiferans. McNamara and Philip (1980) have speculated,
largely on the basis of staining patterns on dead specimens and the positions of
the ends of the petaloids, that
Echinolampas ovata
lives inclined in the substrate,
buried up to the level of the petaloids. The only direct observation ofa cassiduloid
(Rhyncholampas pacificus)
living in this manner is that of Agassiz (1872). If
Echinolampas
lives inclined and buried up to the ends of its petaloids, it is unlikely
to do so to enhance respiration, as
Cassidulus caribaearum
(Gladfelter, 1978) and
Apatopygus recens
(Higgins, 1974) have no difficulty in living deeply buried, and
neither do such actively burrowing spatangoids as
Meoma, Brissus,
and
Plagiobris-
sus
(Kier and Grant, 1965). As McNamara and Philip (1980) note, intraspecific
MOOI: A NEW "LIVING FOSSIL" CASSIDULOID
697
500
meters
depth
Figure 5. Life habits ofliving Caribbean cassiduloids: (A) Cassidulus earibaearum in coarse carbonate
sand of beach foreslope; (B) Eehinolampas depressa in coarse carbonate sand; (C) Eurhodia relieta in
fine to coarse, siliceous terrigenic sand; (D) Conolampas sigsbei crawling on fine carbonate substrate.
Depth axis logarithmic, drawings of echinoids approximately to scale.
698
BULLETIN OF MARINE SCIENCE, VOL. 46, NO.3, 1990
United States
Pacific Ocean
90'
80'
South America
70'
I"'lii='"""'----""I,
1000 km
Western North Atlantic
60'
50'
3d'
20'
10"
Figure 6. Geographic distribution ofliving Caribbean cassiduloids, and collection localities of New
World Eurhodia species. Key: c.c.
=
Cassidulus caribaearum, c.s.
=
Conolampas sigsbei, E.c.
=
Eurhodia corralesi, E.d.
=
Echinolampas depressa, E.e.
=
Eurhodia elbana, E.h.
=
Eurhodia holmesi,
E. baumi, and E. rugosa, E.m.
=
Eurhodia matleyi, E.p.
=
Eurhodia patelliformis. E.T.
=
Eurhodia
relicta.
burrowing behavior is extremely variable, and it is probable that Echinolampas
depressa spends a considerable amount of its time completely covered (Fig. 5B).
Observations from submersibles (David Pawson, Charles Messing, pers. comm.)
show that Conolampas sigsbei lives on the surface of substrates composed of fine
carbonate particles and small foraminiferans. Conolampas fills its gut with this
material as it moves over the surface, leaving a trail as wide as its test (Fig. 5D).
This species has a conspicuously flattened oral surface that aids in locomotion by
increasing the number of oral locomotory spines in contact with the substrate.
E. re/icta differs from other Caribbean cassiduloids in its preference for terrig-
enous substrates. The significance of this is not yet clear. Telford and Mooi (1986)
noted similar restrictions of sand dollars to either siliceous (Mellita quinquies-
perforata) or carbonate (Leodia sexiesperjorata) substrates, but were unable to
suggest an explanation for the mutual exclusion of these echinoids on their pre-
ferred bottom types.
Biogeography and Paleobiology. - The ranges of Recent cassiduloids in the Gulf
of Mexico and the Caribbean are shown in Figure 6. None of these species is
known from the Pacific side of Central America, although the cassidulid Rhyn-
cholampas pacificus occurs in Panama and the Gulf of California. The known
range of Cassidulus caribaearum is unusual in its degree of disjunction, with a
seemingly isolated occurrence in Belize (Fig. 6). Although this species has not yet
been reported from the western part of the Greater Antilles, it should be present
in appropriate habitats of Cuban and Jamaican waters.
MOOI: A NEW "LIVING FOSSIL" CASSIDULOID 699
Figure 6 also shows the localities at which New World fossil and Recent Eurho-
dia species have been found. The distribution of the higher-tested and more
globose Eocene forms of Eurhodia (E. holmesi, E. corralesi, and E. matleyi) was
once much wider than the current occurrences of E. relicta suggest. E. relicta
undoubtedly has a wider range than is indicated by the known material, but
probably not significantly so, as dredging by the PILLSBURYand other research
vessels (e.g., GERDAand COQUETTE)on appropriate substrates and depths along
the coasts of Central and South America has failed to turn up material elsewhere.
The New World range of Eurhodia has therefore been greatly reduced since the
Eocene. Although Eurhodia matleyi and E. corralesi occur in Eocene deposits in
Jamaica and Cuba, no fossil Eurhodia species have been reported from South
America, perhaps because of a lack of appropriate Cenozoic outcrops. If these
exist, then future work should uncover this genus in South American Eocene or
younger strata. However, Cooke's (1961) work with Miocene echinoids from
Venezuela failed to turn up any Eurhodia, although he did describe another
cassidulid, Cassidulus falconensis, from those strata. Weisbord (1969) reported
only a single cassiduloid from the Lower Pliocene of Venezuela, a poorly preserved
specimen probably attributable to the genus Echinolampas.
Petuch (1976; 1981; 1982) described Neogene molluscan "relict pockets" oc-
curring along the coasts of eastern Colombia and Venezuela. Eurhodia relicta also
occurs in this area, under much the same conditions that Petuch described for
his relict molluscan assemblages. However, the extreme age and wide biogeo-
graphic distribution of the most closely related fossil congeners of E. relicta imply
three possibilities: (I) that the cassiduloid situation has nothing to do with Petuch's
relict faunas, (2) the cassiduloid situation is related to Petuch's relict faunas, and
that fossils intermediate in age between the Upper Eocene and the Lower Pleis-
tocene exist but have not yet been found, or were not preserved, or (3) E. relicta
represents both a temporal and biogeographic extension of the relict fauna con-
cepts described by Petuch. Possibility (I) would be supported if strong evidence
that the Indo-Pacific form Oligopodia is the sister group of Eurhodia could be
found. If either (2) or (3) pertain, then the continued existence of Eurhodia might
be related to the same factors that Petuch (1981; 1982) cites for Neogene relict
gastropods, namely that the "atypical Caribbean environment ofthe Recent north-
ern South American coast probably approximates what had been the typical
shallow water marine environment of much of the Neogene southern Caribbean"
(Petuch, 1981: 312). Depressed temperatures and turbidity caused by strong "wind-
driven upwelling systems," and a strong terrigenous substrate component are
proposed physiological and ecological barriers to other, more typical Caribbean
forms, "shielding" and isolating the relict faunas.
ACKNOWLEDGMENTS
I would like to thank D. Pawson, R. Aronson, and B. Carter for helpful suggestions that greatly
improved the manuscript. The latter also graciously provided a preprint of a paper on substrate
preferences of Eocene echinoids. Special thanks to C. Ahearn for her tireless efforts in locating collection
data. Work in the British Virgin Islands was supported by the Natural Sciences and Engineering
Research Council of Canada (NSERC) through Operating Grant #A4696 to Dr. M. Telford. Additional
support was provided by an NSERC Postdoctoral Fellowship and the Smithsonian Institution.
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DATE ACCEPTED: April 24, 1989.
ADDRESS: Department of Invertebrate Zoology, Smithsonian Institution, Washington, D.C. 20560.
