OLIGOPYGUS WETHERBYI de Loriol
Plates 1 (figs. 3-5), 4 (figs. 1, 2, 4), 5, 8 (figs.
10 (figs. 1, 3-5), 13, 14, 16 (fig. 8) ; text figs.
11a, 17, 24,25,26,30,38,39
Material.—Description based on 140 specimens from the Crystal
River Formation near Ocala, Fla., the lectotype, and paralectotype.
Shape.—Test elongate, with greatest width posterior to center,
greatest height at apical system, adapical surface slightly convex,
sides smoothly curving, adoral surface deeply depressed in wide sulcus
at peristome ; shape of test only slightly variable, with lengthwidth
ratio quite constant, width 80-86 percent of length (text fig. 24)
although length-height more variable, height 40-50 percent of length (text
fig. 30b) ; large specimens subpentagonal in marginal outline, average
length 36 mm, largest 54.
Apical system.—Central to slightly anterior; monobasal, central
area strongly inflated (pi. 1, figs. 3, 4), two to four tubercles on
madreporite; ocular plates (pi. 1, fig. 4; text fig. 25d) small,
inflated on well-preserved specimens ; four genital pores located in
suture between madreporite and interambulacra ; large genital pores in
some specimens, very small in others, probably sexually dimorphic ;
anterior pair closer together than posterior; present on specimen 18
Ambulacra.—Petals well developed, straight, open, with greatest
width at extremities of petals, petal III longest, petals II, IV
shortest; interporiferous zones expanding distally, slightly
constricted at extremities of petals, approximately twice as wide as
poriferous zone at extremity of petal; pores strongly conjugate (pi.
2), oblique, with outer pore of pair more distal to inner; pores in
sutures between plates, converging somewhat interiorly (text fig. 2),
ambulacral plates of petals very thin; adradial suture surface not
vertical resulting in ambulacra being narrower at interior of test
than at exterior; in specimen 54 mm long 52 pore-pairs in single
poriferous zone petal III, 47 in petal II, 48 in petal V ; petal III
with from 4 to 12 (average 6) more pore-pairs than petal II, petal II
with from 1 to 7 (average 4) fewer pore-pairs than petal V (text figs.
Beyond petals ambulacral plates single pored; at extremity of petal (text
figs. 25a, 26a) pores very numerous in many demi- and included plates;
beyond this area and continuing most of length of ambulacrum each
large primary has 31/2 to 6 small demi- or included (text
figs. 26b, c) plates along its adradial border; small plates very thin,
on slightly weathered specimens some missing ; all absent on
moderately weathered specimen ; in ambulacra II, III, and IV beyond
petal approximately 66 primary plates, in ambulacra V and I, 82 large
plates; near peristome pores less crowded (text fig. 25c) ; 115 pores
in single poriferous zone of petal III ; ambulacra terminate at
peristome with two large plates arranged in normal manner with larger
plate in right zone of ambulacrum III, adapical in ambulacrum IV,
adoral in all others; buccal pores visible on some specimens,
difficult to see on most.
Interambuhcra.—Two columns of plates in each area except at
peristome where column terminating in single plate; approximately 34
plates in interambulacra 4 or 1, 39 in 5, 36 in 2 or 3 (in specimen 37
Peristome.—Central, wider than high (pl. 4, fig. 1), curved
anteriorly, pointed posteriorly ; located in deep, transverse
depression (pl. 4, fig. 2) considerably wider than high, 40-50 percent
as wide as test, anterior of depression more steeply sloping than
Periproct.—Small, 2.1 mm wide in specimen 45 mm long; circular,
located midway between peristome and posterior margin in large
specimens, slightly nearer the posterior margin in smaller.
Tuberculation.—Test covered with small, irregularly arranged
tubercles; scrobicules deep, with vertical sides; boss large, almost
two-thirds diameter of scrobicule, extending upward as high as
surrounding surface of test ; crenulated ; mamelon small, extending in
height above surface of test, perforated ; crenulations and mamelon
present only in well-preserved specimens ; small secondary tubercles
scattered over area between tubercles.
Interior.—Test with thick plates (text fig. 11a), in specimen 47
mm long adapical ambulacral plates at midlength of petal III 3.6 mm
thick, at adoral interambulacrum 5 midway between posterior margin and
peristome 3.9 mm thick ; on adoral surface ambulacra much thinner than
interambulacra producing deep grooves in ambulacra in interior.
Location of type specimens.—The lectotype, herein designated,
is the specimen figured by de Loriol (1888) on his plate 17, fig. 7,
and herein on plate 13, figs. 1, 2. The paralectotype, figured on de
Loriol's plate 17, fig. 18, is herein figured on plate 13, figs. 3, 4.
These specimens are in de Loriol Collection at the Museum d'Histoire
Naturelle in Geneva, Switzerland. Specimens figured by Cook and Kier (herein)
are in the U.S. National Museum : USNM nos. 562271, 562272, 164660
(holotype of 0. floridanus), 137881, 649832, 649833, 649838, 649841,
649842, 649843, 649849, 649851, 649853.
Occurrence.—Late Eocene, Crystal River Formation, and Williston
Formation, Florida. For an extensive list of localities see Cooke
(1959, p. 28).
Comparison with other species.— O. wetherbyi is found
commonly with O. haldemani and on first impression they look
quite similar. In O. wetherbyi, however, the periproct is
always much nearer the peristome than in O. haldemani. I
measured the distance from the periproct to the posterior margin in
all the specimens from one locality and plotted them on a scatter
diagram (text fig. 27). The points fall into two widely separated
patterns with no overlap.
Usually the periproct opening in O. wetherbyi is more circular,
there are more pore-pairs in petals III and V, I (text figs. 38, 39),
the test is slightly narrower (text fig. 24), and the greatest width
posterior (particularly in larger specimens). Also the interambulacral
plates are more commonly tumid. These differences, however, are slight
and not consistent. O. wetherbyi reaches a larger size than
O. haldemani: one of the larger O. wetherbyi is 54 mm long
(average 36 mm), the largest O. haldemani 37 mm (average 21
Remarks.—I agree with Cooke (1959, p. 28) in considering O.
floridanus Twitchell as a junior subjective synonym of O.
wetherbyi. Twitchell's holotype differs from specimens of O.
wetherbyi that occur with it only in appearing to have narrower
poriferous zones. This appearance is due to the fact that the holotype
is a badly weathered specimen.
Palmer (in Sanchez Roig, 1949, p. 166) erected a variety Oligopygus
floridanus, var. laevis for some specimens from the late
Eocene (middle or late occurring to Brodermann, 1949, in Sanchez Roig,
p. 325) of Cuba. Unfortunately he did not figure his specimens and
from his description I cannot be sure that these specimens should be
referred to O. wetherbyi.