ECHINODERMATA - KU ScholarWorks - University of Kansas

BLASTOID STUDIES 105
Type.-Holotype, 7,225/1, Woodman collection,
American Museum of Natural History, New York.
Genus TROOSTICRINUS Shumard, 1866
Type-species, by subsequent designation (ETHERIDGE & CARPENTER ;
1882).-Pentremites reinwardti TROOST, 1835.
Generic diagnosis.-Spiraculate blastoids with five
paired spiracles, consisting of four paired spiracles and
a paired anispiracle, with a superdeltoid, two cryptodeltoids,
and a hypodeltoid, edges of the cryptodeltoids
slightly exposed; lancet covered by side plates,
one pore between adjacent side plates along ambulacral
margins, radials overlapping deltoids; ambulacra
short, directed outward and downward, with three to
five hydrospire folds on each side of an ambulacrum;
pelvis long, deltoids not visible in side view but hypodeltoid
visible in side view, and steeply obconical in
side view. Silurian, Missouri, Oklahoma, Tennessee,
Kentucky, Indiana, Illinois, Ohio.
Remarks.-The genus Troosticrinus may have
been derived from a form similar to Polydeltoideus
in which the sinuses closed, or both of these genera
may have come from an unknown group of echinoderms
with diverse structures that early differentiated
the Fissiculata from the Spiraculata. An Ordovician
group of echinoderms that may have given rise to the
blastoids is the newly distinguished class Edrioblastoidea,
proposed in an article to appear in the "Journal
of Paleontology." The only genus known in this
group is Astrocystites, which has many regular thecal
plates and deep infolds crossing the sutures, with five
regular straight petaloid or widely linear ambulacra.
TROOSTICRINUS REINWARDTI (Troost)
Plate 19, figures 1-5; text-figs. 218-221
Pentremites reinwardti TROOST, 1835, P. 224, pl. 10, figs. 10-11.
Pentatrematites reinwardtii ROEMER, 1851, p. 373, pl. 6, figs. 13a-c;
1860, p. 60, pl. 3, figs. 2a-c; 1876, pl. 11, fig. 10.
Troosticrinus reinwardti SHUMARD, 1866, p. 385, footnote.
Troostocrinus reinwardti ETHERIDGE & CARPENTER, 1886, p. 193,
text-fig. 7, p. 194, pl. 12, figs. 11-12, pl. 17, fig. 17; BATHER,
1900, p. 87, fig. 8; WOOD, 1909, pp. 13, 17, pl. 3, figs. 2-4;
SPRINGER, 1913, p. 170, fig. 264; JAEREL, 1918, p. 107, fig. 101;
SPRINGER, 1926, p. 141, pl. 33, figs. 1-8; WANNER, 1933, p. 495,
fig. 32; AMSDEN, 1949 (as Troosticrinus), pp. 82-83, pl. 12,
figs. 5-7, text-fig. 29.
Description.-The holotype is obconical in side view,
23 mm. long by 8 mm. wide, vault 5 mm. long, pelvis 18
mm. long, pelvic angle 30 degrees; periphery at radial
lips above mid-height, and rounded pentagonal in top
view. Basal circlet conical in side view, 9 mm. long, with
three normally disposed basals. Radials five, each approximately
14 mm. long by 5 mm. wide, with short
radial limbs and linear sinuses. The radial limbs on the
anal side are shorter than those on the other sides. Radials
overlap deltoids.
Deltoids four, short, externally appearing as an inverted
V, each with a paired spiracle elongate in its
medial portion. Deltoids not visible in side view except
along sinus areas. On the anal side are four anal deltoids.
The small superdeltoid is adjacent to the oral opening,
and the two elongate cryptodeltoids rest on the aboral
face of the superdeltoid, separating the anal opening from
the adjacent hydrospire canals internally and partly externally.
The pentagonal hypodeltoid almost covers the
cryptodeltoids but the suture between these plates is
visible along sinus margins in well-preserved specimens.
The elongate hypodeltoid is visible in side view and
abuts against the short radial limbs on the anal side. The
cryptodeltoids reach the exterior slightly and therefore a
paired anispiracle is present, in which the anal opening
and adjacent hydrospire canals are incompletely fused.
Thus, five paired openings surround the mouth, consisting
of four paired spiracles and a paired anispiracle. There
are three to five hydrospire folds on each side of an
ambulacrum, distinguishing this genus from Metablastus,
which has four or five hydrospire folds, and Tricoelocrinus,
which has three small folds in the substance of
the radial plates.
EXPLANATION OF PLATE 36
FIGURE PAGE
1-3. Tanaoblastus missouriensis (SuumARD), hypotype, 3,576,
Carl C. Branson coll., Univ. Missouri; Lower Mississippian,
Chouteau Limestone, quarry near Sweeney, Mo.; oral,
"D" ambulacral, aboral views of specimen figured by Peck
(1938, pl. 26, fig. 39) (all X6.9) 104
4-6. Tanaoblastus tennis (HANIRAGH), hypotype, 3,572, Carl C
Branson coll., Univ. Missouri; Lower Mississippian, Chouteau
Limestone, near Providence, Mo.; oral, "D" ambulacral,
aboral views of specimen figured by Peck (1938, pl.
26, figs. 16,22) (all X7.2) 105
7-12. Tanaoblastus roemeri (SHUMARD). 7-9. Hypotype, 1,143,
Blair coll., Univ. Missouri; Lower Mississippian, Chouteau
Limestone, near Sedalia, Mo.; oral, "D" ambulacral, aboral
views of specimen figured by Peck (1938, pl. 26,
figs. 24,28,32) (all X8.5).-10 12. Plesiotypes, 19,106,
Gurley coll., Univ. Chicago; Lower Mississippian, Chouteau
Limestone, Sedalia, Mo.; 10, polished cross section of
summit showing cryptodeltoids adjacent to anal opening
( X9.6); 11, oral view of polished cross section with "A"
ambulacrum upward, showing two hydrospire folds on
each side of ambulacrum ( X6.6); 12, oral view of another
specimen showing lack of pores along margins of
deltoid plates (X7.5) 102