ECHINODERMATA - KU ScholarWorks - University of Kansas

1 1 0 THE UNIVERSITY OF KANSAS PALEONTOLOGICAL CONTRIBUTIONS
new genus; so-called Metablastus hispanicus of the
Devonian of Spain, probably does not belong to this
genus; forms identified as Orbitremites aplatus, O.
calycinus, O. excavatus, O. fimbriatus, O. grandis, O.
magnificus, O. ornatus, O. parvus, O. spathatus, O.
spinuliferus, and O. tvachsmuthi probably belong to
diverse genera, some perhaps to new genera, but seemingly
not to Orbitremites; Phaenoschisma? kentuckyense
probably does not belong to Phaenoschisrna. It
is hoped that others will restudy blastoids in collections
of various museums in order to fill in gaps
in knowledge such as are here suggested.
It is significant that very few blastoids have been
described from Pennsylvanian deposits and that records
of blastoids in South America, Africa, Antarctica,
Asia, and the North Polar regions are meager or lacking.
Evidently the study of blastoids is not yet far
advanced. It is premature to say that the center of
dispersal of blastoids is the mid-Continent region of
the United States, merely because the oldest and most
primitive blastoids occur in Silurian deposits of this
region. The basis for this sort of statement is that
Silurian blastoids have not been described from other
continents, but it would not be surprising if they are
discovered in various regions outside of North
America.
There is little in common between blastoid genera
of Europe and North America, or between those of
Timor and Europe, or between Timor and North
America, and yet when lineages are traced, a tie between
these regions seems to exist. "Missing links,"
both stratigraphic and geographic, are postulated to
account for the differences; when missing links are
found, the literature on blastoids will probably be
double its present size. To date, approximately 800
articles have been published on blastoids; they treat
some 33 genera of the Fissiculata and 35 genera of the
Spiraculata, together including about 350 species.
KEY TO FAMILIES AND GENERA OF
BLASTOIDEA
The following key is offered as an aid to those
who may wish to identify genera of blastoids, as now
known and understood. The key is arranged by families
belonging to the two orders Fissiculata and
Spiraculata. In using the key, one should proceed by
noting the characters recorded under succesive letters
and numbers until the desired end is reached.
Hydrospire fields exposed or spiracular slits
present
FISSICULATA
Hydrospire fields concealed, pores and
spiracles present
SPIRACULATA
FISSICULATA [Families, see nos. 1-5]
1. Exposed hydrospire fields ten (Phaenoschismatidae)
A
2. Exposed hydrospire fields nine
(Brachyschismatidae)
3. Exposed hydrospire fields eight (Codasteridae)
4. Spiracular slits ten (Orophocrinidae) D
5. Spiracular slits eight (Astrocrinidae)
SPIRACULATA [Families, see nos. 6-10]
6. Spiracles five, simple (Pentremitidae)
7. Spiracles five, paired (Troosticrinidae) G
8. Spiracles nine (Granatocrinidae) H
9. Spiracles ten, anus separate, cryptodeltoids
exposed (Nucleocrinidae)
10. Spiracles ten, anus separate, cryptodeltoids
absent (Schizoblastidae)
A. PHAENOSCHISMATIDAE (Silurian-Permian)
[Genera, see nos. 11 -311
11. Anal deltoids four to six 14, 15
12. Anal deltoids three Decaschisma
13. Anal deltoids two or one 16, 17
14. Hydrospire slits reduced in number on
anal side
Deltoschisma
15. Hydrospire slits not reduced in number
on anal side 18, 19
16. Ambulacra with lancets widely exposed
Phaenoblastus
17. Ambulacra with lancets covered by
side plates 22, 23
18. Ambulacra directed laterally outward,
six anal deltoids
Polydeltoideus
19. Ambulacra directed downward, four
anal deltoids 20, 21
20. Hydrospire slits completely exposed .. Pleuroschisma
21. Hydrospire slits almost hidden, with
formation of pores
Hyperoblastus
22. Ambulacra five 24, 25
23. Ambulacra two Dipteroblastus
24. Ambulacra extremely long 26, 27
25. Ambulacra moderately long to extremely short 28, 29
26. Ambulacra flaring outward into elongate
wings
Thaumatoblastus
27. Ambulacra projecting downward aborally,
calyx globular Nymphaeoblastus
28. Ambulacra moderately long 30a, 30b, 31
29. Ambulacra extremely short Neoschisma
30a.Calyx conical, ambulacra narrow Con oschisma
30b. Calyx conical, ambulacra broad Phaenoschisma
31. Calyx flattened Notoblastus