Echinocardium marylandiense, new species
figures 2, 3;
Figures 1, 2
1904:430, pl. 119: figs. 1 a-c—Clark and Twitchell, 1915: pl. 98: figs.
1 a-c, 2ac— Schoonover, 1941:92-93.—Cooke, 1942:60 [the specimens from
Maryland belong to this species].—Vokes, 1957: 39, pl. 30: figs.
1-3.—Cooke, 1959: pl. 33: figs. 1-5.
characterized by petals expanding adapically, with outer poriferous
zones of an anterior petal forming almost continuous arc with those of
posterior petal; wide test with width equal to length, height 54-69
percent L, central apical system, width of area circumscribed by
internal fasciole 37-44 percent L, prominent nodes on interambulacral
specimens of this species have been found, particularly near
Scientists' Cliffs, Calvert County, Maryland. Large slabs from there
are filled with specimens (Schoonover, 1941). The description here is
based on specimens from this locality, and the statistics were taken
from 15 individuals.
Shape and size.—Largest
specimen 57.0 mm long, smallest 43.5, mean 47.4 (SD 4.1, CV 8.7, N-15)
; test wide, nearly as wide as long with width 94-104 percent L, mean
97.9 (SD 3.0, CV 3.1, N - 1 5 ) , greatest width anterior of center;
test high with height 54—69 percent L, mean 59.0 (SD 4.4, CV 7.4,
N-14), greatest height posterior of apical system; posterior
truncation oblique with periproct slightly visible from above.
genital pores, ethmolytic with genital 2 extending far posteriorly;
located at distance from anterior margin to center of genital pores
equal to 40-51 percent L, mean 46.4 (SD 2.9, CV 6.2, N - 1 5 ).
ambulacrum not petaloid (Plate 7: figure 2), in groove from apical
system to peristome, at margin depth of groove equal to 3.9 percent L
(SD 0.8, CV 20.3, N-14) ; porepairs within internal fasciole oblique
with adapical pore of pair larger than adoral, small node between
pores of each pair; pores in plates between internal fasciole and
phyllode very small, single or slit-like; 7 pores in single poriferous
zone from internal fasciole to peristome.
Anterior paired petals very wide with large porepairs outside of
internal fasciole and 3-5 large porepairs within internal fasciole in
posterior poriferous zone, none in anterior poriferous zones within
internal fasciole, petals only slightly depressed, narrowing distally;
9-11 (mean 9.7) large porepairs outside of internal fasciole in petal
IIa, 5-8 (mean 6.4) large porepairs outside of internal fasciole in
Posterior paired petals with no large porepairs within internal
fasciole, 9-11 (mean 9.8) large porepairs in petal Va outside of
internal fasciole, 8-10 (mean 8.8) in petal Vb outside of internal
fasciole; outer poriferous zones of anterior and posterior petals
forming almost continuous arc; ambulacral plates beyond petals with
single pores except within anal fasciole, where 2 porepairs are in
each single poriferous zine.
prominent node on each interambulacral plate; 22-24 plates in
interambulacrum 5, 15-17 in interambulacrum 1, 10-11 in 2 from
internal fasciole to peristome.
distance from anterior margin to anterior edge of peristome equal to
28-34 percent L, mean 31.6 (SD 1.5, CV 4.8, N-15) ; opening wider than
high with width 21-25 percent L, mean 21-25 (SD 1.1, CV 4.8, N-14).
high on posterior truncation, opening slightly higher than wide with
height 10-16 percent L, mean 12.6 (SD 1.6, CV 12.6, N-12), width 11-14
percent L, mean 12.8 (SD 0.9, CV 7.0, N—13) ; located between plates
Oral plate arrangement.—Labrum
wide (Figure 6), extending across almost entire width of peristome,
extending posteriorly two-thirds height of first ambulacral plate;
length of labrum 7-11 percent L, mean 9.1 (SD 0.8, CV 9.1, N-15) ;
plastron extending to posterior margin, length 50-55 percent L, mean
52.0 (SD 1.8, CV 3.4, N-15) width 33-36 percent L, mean 34.8 (SD 1.1,
CV 3.1, N-15) ; first plate of interambulacra 1,4 very narrow.
Ambulacra widening near peristome (Figure 6), phyllodes with 5 pores
in ambulacrum III, 7-8 in II, 6 in I.
fasciole prominent, greatest width of tract 2.9 mm in specimen 48 mm
long or 6.0 percent L, fasciole crossing ambulacral plates 7a and
marylandiense, new species: Adoral plate arrangement of
figured paratype USNM 174467 from the middle Miocene Choptank
Formation, Scientists' Cliffs, Calvert County, Maryland (X 1.6).
(For detailed locality data, see description of species.)
ambulacrum III, 20a and 17b in ambulacrum II, 21a and 23b in
ambulacrum I, lla-12a or b in interambulacrum 5, 9a-10a or b in 1, 7a
or 7b in 2; greatest width of area circumscribed by internal fasciole
anterior of apical system, width 37^-4 percent L, mean 39.1 (SD 2.1,
CV 5.5, N-14). Subanal fasciole occurring on posterior truncation
below periproct, area circumscribed by fasciole 14.4 mm wide on
specimen 45 mm long or 32 percent L, maximum width of tract 1.7 mm
wide on specimen 45 mm long or 3.7 percent L; crossing plates 3-5 of
interambulacrum 5, plates 6a-8a of ambulacrum I, plates 6b-8b of
ambulacrum V. Anal fasciole present but tract not clear.
Comparison with other species.—Echinocardium
marylandiense differs from E. orthonotum from the Upper
Miocene Yorktown Formation of Virginia and Upper Miocene of South
Carolina in having a wider, more angular, and higher test, a wider,
more posteriorly situated peristome, a narrower periproct, shorter,
wider plastron, longer labrum, wider fascioles, and a wider area
curcumscribed by the internal fasciole, and more prominent nodes on
the interambulacral plates. See Table 1 for the statistical expression
of these differences. Of all the living species, E. marylandiense
most resembles E. cordatum (Pennant). It differs in the
1. Lower test lacking the greatly
inflated area posterior to the apical system.
2. Apical system centered, whereas in
E. cordatum it is posteriorly very eccentric.
3. Wider area circumscribed by internal
4. Anterior poriferous zones more
5. Larger pores in posterior poriferous
zones of anterior petals within internal fasciole; in E. cordatum
these pores are microscopic, whereas in E. marylandiense they
are distinguished easily with the naked eye.
6. Posterior truncation tilting in E.
marylandiense so diat periproct is almost visible from above,
whereas in E. cordatum the truncation is vertical to
7. Area circumscribed by subanal fasciole
much wider, widi width greater than height, whereas in E. cordatum
it is much narrower, with width less than height.
8. Plastron less inflated and labrum with
longer posterior extension.
9. Anterior ambulacrum much less
depressed from apical system to margin.
USNM 174460; figured specimens: USNM 174467, 498960a,b, 559489.
Stratigraphic position and geographic localities.— Middle Miocene
Choptank Formation, typespecimens and measured specimens came from
slabs (Schoonover, 1941) collected 2200 feet N of stairway and
artesian well at Scientists' Cliffs, which in turn is 1.5 miles N of
Kenwood Beach ( = Governor's Run), and about 1 mile S of mouth of
Parker Creek, Calvert County, Maryland. The slabs were found 18 feet
above mean high tide within a vertical range of three or four inches,
which extends about 12 feet along face of cliff. The slabs consist
mainly of quartz sand and come from a horizon near the contact between
the Calvert and Choptank Formations and 18 feet below the bottom of
Shattuck's (1904) Zone 17 of the Choptank, according to Schoonover
(1941). T. G. Gibson of the United States Geological Survey has
studied the Foraminifera in one echinoid from these slabs and states (personal
communication, 1971) that the assemblage is typical of the Choptank
Formation in this area. Other localities: Jones Wharf, Patuxent River,
Maryland, and specimens provisionally referred to this species from
Grubin Neck, 1 mile N of Howell Point, Talbot County, Maryland.
Planches 7 et 8