Redescription Of A Unique Feather Star (Echinodermata: Crinoidea: Comatulida: Comasteridae) With The Diagnosis Of A New Genus

6 Pages·1995·3.9 MB·

by  C G Messing

PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON
108(4):656-66L 1995
Redescription of a unique feather star
(Echinodermata: Crinoidea: Comatulida: Comasteridae)
with the diagnosis of a new genus
Charles G. Messing
Nova Southeastern University Oceanographic Center, 8000 North Ocean Drive,
Dania, Florida 33004, U.S.A.
—
Abstract. A new genus, Aphanocomaster, is erected for Comasterpulcher
A. H. Clark, which is known only from the holotype. The genus is similar to
Comaster in having an apparent cryptosynarthry in the primibrach series, the
first brachial syzygy chiefly between the first and second brachials on arms
arising from the tertibrach series, and a central mouth. It differs in lacking a
transverse initial comb tooth. The new genus differs from all other comasterid
genera in having secundibrach series of four ossicles series in which both the
first and second ossicles and the third and fourth are united by synarthrial
articulations.
In the course of revising the Indo-West- of ossicles following radial or axil and in-
ern Pacific genus Comaster L. Agassiz, a cluding the next axil; I-IVBr: first through
re-examination of Comaster pulcher A. H. fourth brachitaxes (written out primi-, se-
Clark revealed that the single known spec- cundi-, terti-, and tetrabrachitaxis, or tetra-
imen lacks a critical feature of the genus as brach series); Arabic numeral immediately
currently diagnosed and exhibits another, following indicates number of ossicles in
previously unnoticed characteristic unique that brachitaxis (e.g., IIBr2). Arm: unbran-
to the family. The combination requires re- ched series of ossicles following distalmost
moval of the species from Comaster and axil; brachial (br; plural, brr): arm ossicle;
establishment of a new generic name for it. subscript number indicates specific ray os-
In addition, published descriptions are uni- sicle (brachitaxis or arm) counting from
formly incomplete (A. H. Clark 1912, 1918, first ossicle after preceding axil or radial
WL
1931). (e.g., IIBr2, br7); ofray ossicle: median
Terms, abbreviations, measurements and width to midaboral length ratio when
—
symbols are as follows: Centrodorsal: cen- viewed aborally. Synarthry ( ) (See
tral aboral plate. Cirri: aboral, segmented "Note" below): articulation typically be-
hooks attached to centrodorsal; Roman and tween first two ossicles of a brachitaxis or
Arabic numerals indicate numbers of cirri/ arm consisting of two ligament bundles
individual and segments (cirrals)/cirrus, re- separated by an aboral-oral fulcral ridge,
spectively (a range of values is usually giv- sometimes with midaboral swelling. Cryp-
LW
en); of cirral: length to median width tosynarthry: synarthry modified as a tight
ratio when viewed laterally. Ray: one of junction, visible externally as a fine line;
five branched series of ossicles radiating the articular faces either smooth or with
from center of specimen. Radial: (n.) first round or elongate, often concentric raised
ossicle of a ray or (adj.) a structure asso- areas (Hoggett & Rowe 1986, fig. 2c). Syz-
ciated or oriented with a ray. Axil: ossicle ygy (+): articulation between two succes-
at which a ray branches. Brachitaxis: series sive ray ossicles consisting of radiating
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VOLUME 108, NUMBER 4 657
ridges and grooves and appearing externally an unusual distribution of synarthries, they
as a perforated line (e.g., br3+4); intersyzy- must be clearly indicated. However, even if
gial interval: number of articulations be- additional specimens eventually demon-
tween successive syzygies. Pinnules (P): strate that the distribution of synarthries de-
unbranched segmented appendages arising scribed below is an abnormality, the unique
from alternate sides of successive brachials, combination of other features exhibited by
and from exterior side of brachitaxes of this specimen requires diagnosis of a new
more than two ossicles; on brachitaxes, sub- genus, as follows.
script Roman numerals indicate brachitaxis
from which pinnule arises (e.g., Pn on IIBr); Aphanocomaster, new genus
on arms, subscripts count pinnules from the
—
most proximal; Arabic numbers and letters Diagnosis. A genus of Comasteridae
refer to pinnules along exterior and interior with IBr2 ossicles appa—rently united—by
side of an arm, respectively (that is, the cryptosynarthry; IIBr2(l 2) and 4(1 2,
sides away from and toward the extrapolat- 3—4); IIIBr2(l—2), 4(1—2, 3^) and
ed axis of the preceding axil) (e.g., P4, P^); 4(1—2, 3 + 4) [possibly also 2(1 + 2)]; in
LW
of pinnule ossicles (pinnulars): length brachitaxes of four ossicles, the second os-
to median width ratio. Comb: modification sicle (IIBr2 and IIIBr2) laterally enlarged ex-
of distal pinnulars of proximal (oral) pin- teriorly to accommodate robust base of Pn
nules producing comblike profile. Disk: and Pni, respectively; first brachial syzygies
central visceral mass or, specifically, its oral chiefly brj+2,3+4 on arms arising from IIIBr;
surface; anal interambulacral area: area on br3+4 alone on exterior arms arising from
disk surrounded by food grooves and bear- IIBr; comb teeth tall, triangular or spade-
ing anal papilla. For further discussions and shaped, confluent with exterior lateral mar-
examples of comatulid morphometries, gin of pinnular; initial tooth sometimes
meristics, abbreviations and symbology, see slightly twisted, but not oriented transverse-
A. M. Clark & Rowe (1971), Breimer ly; mouth central; anal papilla midway be-
(1978), Hoggett & Rowe (1986) and Mess- tween mouth an—d disk margin.
&
ing Dearborn (1990). In all illustrations, Type species. Comaster pulcher A. H.
sparse uniform stippling indicates articula- Clark (1912), —by monotypy.
tions between successive ossicles. Etymology. From aphanes {a(j)ave^),
Note: The following descriptions include unseen, invisible, secret, obscure (Brown
an exception to standard comatulid sym- 1978), and the genus name Comaster. Gen-
bology. Syna—rthries are designated by one- der is masculine—.
em dashes ( ), following the usage ofGis- Distribution. Known only from a single
len (—1934), so that, for example, IIBr4(l station in the Kei Islands, Indonesia, 0-52
m
2, 3 4) indicates a secundibrach series of (A. H. Clark 1931).
fourossicles in which both the first and sec- Remarks.—A. H. Clark (1921) and Gis-
ond and the third and fourth ossicles are len (1934) considered the few records in co-
united by synarthry. In comatulid crinoids, matulids of four-ossicle brachitaxes con-
the first two ossicles following a radial or sisting oftwo synarthrial pairs as abnormal.
axil are joined either by synarthry (some- They recorded this pattern in only three
times modified as a cryptosynarthry) or species: Cyllometra manca (Carpenter)
syzygy. Typically, only the latter is shown (Colobometridae) (originally as C. anomala
(as a + sign) in written symbology. When A. H. Clark), Heterometra quinduplicava
a syzygy is not present, a synarthry is as- (Carpenter) (Himerometridae) and Adelo-
sumed in this position (e.g., in IIIBr2, the metra angustiradia (Carpenter) (Antedoni-
two ossicles are joined by synarthry). Be- dae). A. H. Clark (in A. H. Clark & A. M.
cause the species discussed herein exhibits Clark 1967) suggested that the single
658 PROCEEDINGS OFTHE BIOLOGICAL SOCIETY OF WASHINGTON
known specimen of A. angustiradia might length, becoming compressed and slightly
LW
be ajuvenileHimerometra orrelated genus, expanded distally; eighth segment with
but placed it in the Antedonidae on the ba- = 1.1-1.3; one or two segments preceding
sis ofits cirri and pinnules. Messing (1975) penultimate with LW = 1.0-1.1 (Fig. lb,
noted IIBr4 without IIBr3+4 in several spec- c). Fourth and following segments with
imens ofCrinometra brevipinna (Pourtales) low, aboral, subdistal, transverse swelling
(Charitometridae), but did not otherwise or ridge, sometimes finely spinulose, nar-
identify the articulation between the third rower on more distal segments, becoming
and fourth ossicles. low blunt and triangular on the four to five
If, in specimens collected in the future, segments preceding penultimate (Fig. Id,
brachitaxes with two pairs of synarthries e). Fourth and following segments shiny.
prove to be abnormally doubled forms of Opposing spine low and wide, sharp or
the much more widespread (among comat- blunt.
ulids) brachitaxes of two ossicles united by Arms 35, all in single plane, none com-
synarthry, a new genus still must be erected plete. Radials very short, just visible. IBr2
for the type specimen of Comasterpulcher. ossicles joined by tight articulation, proba-
No genus currently exists in the Comaster- bly cryptosynarthry (see remarks). IBrj
idae with the combination of features ex- very short, WL = 4.5-5.0, completely sep-
hibited by this specimen: first brac—hial syz- arated orjust touching at proximal comers,
ygy chie—fly br,+2,3+4, both IIIBr2(l 2), and and slightly narrower distally so that adja-
IIIBr4(l 2, 3 + 4) present; no initial cent IBr, are separated by V-shaped gap
transverse comb tooth; mouth central. Only (Fig. la). One IIBr2(l—2) bearing IIIBr4-
3+4) 3^)
if the IIIBr4(l—2, are also highly (1—2, exteriorly and II—IBr4(l—2,
unusual and all brachitaxes are normally of 3+4) interiorly; ni—ne nBr4(l—2, 3 4) bear-
two ossicles in future specimens would ing nine IIIBr2(l 2) [one of these with a
pulcher fall within a currently recognized close articulation;possibly IIIBr2(l + 2)] and
genus: Comissia (Hoggett & Rowe 1986). three mBr4(l—2, 3 + 4) [two of the latter
arising from one IIBr4]. IHBr developed in
Aphanocomasterpulcher pairs or interiorly on IIBr. One interior
(A. H. Clark, 1912) IVBr2(l + 2)?; the articulation uniting its os-
Fig. 1 sicles a tight line similar to syzygy on prox-
imal brr, but perforations not clearly visible.
Comaster pulcher A. H. Clark, 1912:22.-
First ossicles of adjacent brachitaxes beyond
1918:37, 40, 275, pi. 14, figs. 14, 15.-
1931:443-444, pi. 50.—Gislen, 1919:14. the first (H-IVBri) joined interiorly for most
— or all of their length; adjacent IIBr and fol-
Holotype. University of Amsterdam, lowing brachitaxes separated interiorly by
Zoological Museum, U.Cri.-2114. Siboga narrow U-shaped gaps; gaps becoming nar-
Expedition Station 257, Du-roa Strait, Kei rower between more distal brachitaxes, but
Islands, Indonesia, 0-52 m, 11 Dec 1899. 1 remaining distinct between adjacent arm
mm
specimen. — bases. Width at IIBr4 axil 1.6 (1.3 at
Description. Centrodorsal a thick, IIIBr axil).
mm
rounded pentagonal disk, 4.1 across Br, slightly longerexteriorly; adjacentbr,
(Fig. la). Aboral pole slightly depressed, joined interiorly; in arm bases with br, 2 unit-
with cirrus sockets encroaching on margin. ed by synarthry, br2 cuneate and projecting
Cirri XXXIV, 15-17, up to 11.2 mm long, exteriorly to accommodate base of large P,.
in crowded double marginal row; first seg- Proximal brachials otherwise oblong as faras
ment short, second with LW = 1.5-2.0; br6.8, WL = 1.7; triangular or almost so by
third segment longest, with LW 2.8; fourth about br9_,o, WL = 1.9. Middle brachials tri-
and following segments decreasing in angular, WL = 1.3-1.4. Distal brachials elon-
VOLUME 108, NUMBER 4 659
Fig. 1. a-i. Aphanocomasterpulcher (A. H. Clark), holotype. a. Aboral view showing centrodorsal, bases
ofcirri, bases ofthree rays, and basal few ossicles of proximal pinnules, b. Cirrus with weak aboral ornamen-
tation, c. Cirrus with strong aboral ornamentation, d. Oblique view of fourth (left) and fifth cirrals showing
finely spinulose transverse subdistal ridge, e. Oblique view oftenth (left) to thirteenthcirrals showing transverse
aboral swelling narrowing to triangular process on more distal segments, f. P„ reconstructed from fragments;
mostofcomb lost. g. Pj. h. Lateral viewofproximal partofcomb from adetachedoral pinnule showing slightly
twistedproximaltooth (arrow), i. Same,obliqueview.j. Comasterdistinctus(Carpenter),lateral viewofproximal
partofcombfrom adetachedoral pinnule showing well-developedtransversely-orientedproximal tooth (arrow).
Scale bar: a, 2 mm; b, c, f, g, 1 mm; d, e, h-j, 0.5 mm.
660 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON
gated, shaped like bent hourglasses, WL = tooth. [Compare with initial transverse
0.5 (LW = 1.9). tooth of Comaster distinctus (Carpenter),
Aboral surface ofrays smooth, somewhat Fig. Ij.] Comb either rising abruptly with
flattened. On II and IIIBr4(l—2, 3—4), II tall first tooth, or developing gradually over
and IIIBr2 cuneate with exterior lateral mar- 1-3 increasingly tall teeth. Distal teeth
&
gin projecting for articulation of very ro- smaller shorter but still well developed.
bust Pn and Pm; Pn and P^ so leirge that the Combs coiling planospirally; present to at
ossicle bearing them almost appears as an least Pg.
asymmetric axil (Fig. la). Synarthries on Pg of 18 segments, no teeth, L = 5.4 mm;
brachitaxes sometimes weakly swollen most segments (except at base and tip) lon-
midaborally. Distal margins of mid-arm ger than wide, cylindrical and constrictedin
LW
brachials finely dentate but not flared or middle, to 2.0; distal segments with
thickened. Distal brachials smooth. Epi- cluster of lateral spines; hooks on last 3
dermis fairly thick, obscuring several artic- segments. P7 and Pg first genital pinnules;
ulations. spherical gonads developed on fourth-sixth
First brachial syzygies chiefly br,+2,3+4 on segments. Middle pinnules of 17-18 seg-
mm
arms arising from IIIBr; br3+4 alone on ex- ments, 6.0 long; first two segments
terior arms arising directly from IIBr4 (one short, third and fourth squarish; these first
with br3+44+5, another with br4+5 instead) four segments stout; following segments
(Fig. la). On one ray, the exterior arms aris- narrower so pinnule tapers to slender tip;
ing from a pair of adjacent IIIBr2 both lack most segments little longer than broad with
bri+2 (one has br3+4, the other is broken at bundle of strong spines along lateral mar-
mm
br2); interiorly, one of these IIIBr2 bears an gin. Distal pinnules of 17 segments, 7.2
arm with br^+2,3+4; the otherbears a IVBr2(l long; first two segments short; following
+ 2) which, in turn, bears an interior arm segments elongate (except near tip), and of
with brj+2,3+4 and an exterior arm with br3+4 about equal length but becoming more slen-
LW
alone. Next syzygy brj^+n. Distal intersy- der distally; increasing from about 3.3
zygial interval chiefly 4 (occasionally 3 or proximally to 5.2 distally (not including
5). basal or distalmost segments).
P„ of 35+ segments, comb lost; estimat- Disk completely naked; oral integument
ed length —14 mm; very robust at base, ta- somewhat transparent with tiny sclerites
pering to slender and flagellate distally; visible in tissue. Mouth central; anal papilla
LW
middle segments longer than broad (to large, about midway between mouth and
= 1.5); no spines visible (Fig. If). One de- disk margin; anal interambulacral area only
tached oral comb of 15 teeth possibly be- slightly larger than other interambulacral
longs to P„ or Pijj. P, of 37 segments with areas. —
11 teeth, L ~ 10.0 mm; similar to Pn but Color. Whit—e in alcohol.
slightly less robust; apparently shorter with Distribution. Kei Islands, Indonesia.
fewer segments. P2 of 31-33 segments, 12 Known only—from the type specimen.
teeth, L = 8.2 mm; much less robust than Remarks. The identities of the articu-
Pj (Fig. Ig). P^ of at least 26 segments with lations in several brachitaxes are uncertain.
6 teeth (tip possibly lost), remaining length The two ossicles ofeach IBr2 arejoined by
= 7.6 mm. Pf of at least 22 segments with a tight articulation that may be either a syn-
7 teeth (tip possibly lost), remaining length arthry or cryptosynarthry. No trace of the
= 5.7 mm. Comb teeth tall, triangular or external perforations exists that would iden-
spade-shaped and at least slightly incurved, tify these articulations as syzygies and place
confluent with exterior lateral margin of the specimen in the genus Comatula. The
pinnular. Initial tooth sometimes slightly articulation has not been dissociated for de-
twisted (Fig. Ih, i); no initial transverse tailed examination because the specimen is
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VOLUME 108, NUMBER 4 661
unique. The articulations between the two hospitality, and J. Bleeker of the Instituut
ossicles of the single IVBr2, and the IIIBr2 voor Taxonomische Zoologie, University of
that precedes it, are tight, similar to syzy- Amsterdam, for making the type specimen
gies on the proximal brachials, but with of Comasterpulcher available to me. I also
perforations not clearly visible. thank Nadia Cominardi (curator of echino-
The specimen is in somewhat poorer derms, MNHN) for bringing the availability
condition than when last photographed (A. of funding to my attention, and for provid-
H. Clark 1931). However, the current re- ing research space, great assistance and ex-
description is substantially more detailed traordinary generosity during my stay in
and differs in several important respects Paris. This is Contribution no. 8 from the
from those previously published (A. H. Deep Ocean Society, Inc., Hollywood, Flor-
Clark 1912, 1918, 1931). I found XXXIV ida.
rather than XXVII cirrus sockets with the
longest cirrus segment having LW = 2.8 Literature Cited
ratherthan 3 to 4. Theprevious—descriptions Brown, R. W. 1978. CompositionofScientificWords.
refer to a single IIBr2(l 2), nine SmithsonianInstitutionPress,Washington,D.C.
IIBr4(l—2)(3 + 4), and all IIIBr2(l + 2). 882 pp.
This re-examination clearly shows that syz- Clark, A. H. 1912. Seventeen new East Indian cri-
ygies are not present in the IIBr, and that noids belonging to—the families Comasteridae
andZygometridae. ProceedingsoftheBiolog-
the IIIBr includes 4(1—2, 3—4), 4(1—2, 3
ical Society ofWashington 25:17-28.
+ 4), 2(1—2) and, possibly, 2(1 + 2). . 1918.—Unstalked crinoids of the Siboga Ex-
In addition to the diagnostic characteris- pedition. Siboga Expedition 42b:1-300, 28
tics of brachitaxes and pinnule combs, sev- pis.
eral other features also distinguishA. pulch- . 19—21. A monograph ofthe existing crinoids.
1(2). Bulletin of the United States National
er from the several nominal cirrus-bearing Museum 82. xxvi + 795 pp., 57 pis.
species of Comaster of similar size: C. fru- . 1931. A monograph ofthe e—xisting crinoids.
ticosus A. H. Clark, C. brevicirrus (Bell), 1(3) SuperfamilyComasterida. Bulletinofthe
C schoenovi A. H. Clark, C. sibogae, A. United States National Museum 82. viii + 816
sHe.rrCaltaursk,(AC.. Hd.istCilnacrtku)s. (ICnartpheensteerC)omaansdteCr p,p.&, 8A2.pMis.. Clark. 196—7. A monograph of the
existing crinoids 1(5). Bulletin of the United
spp., the longest cirral is usually the fourth, States National Museum 82:1-860.
not the third; cirrals bear well developed Gislen, T. 1919. Results of Dr. Mjoberg's Swedish
aboral transverse ridges with a stronger op- Scientific Expedit—ion to Australia, 1910-1913.
XXIII. Crinoids. Kungl. svenska Vetenskap-
posing spine; middle brachials are shorter
sakademiens Handlingar 59(4):3-37, 1 pi.
and usually cuneate with everted spinose 1934. A reconstruction problem; analysis of
.
distal margins; the first syzygy following fossil comatulids from N. America with a sur-
bri+2 (or br3+4, when present) occurs at vey of all—known types of comatuHd arm-ram-
bfio+ii to t)ri2+i3; the distal intersyzygial in- ifications. Kungl. Fysiografiska Sallskapets
Handlingar N.E 45(11):1-59.
terval is usually 3, not 4, and the disks usu- Hoggett, A. K., & E W. E. Rowe. 1986. A reappraisal
ally bear at least some slender conical nod- of the family Comasteridae A. H. Clark, 1908
ules. (Echinodermata: Crinoidea), with the descrip-
tion of a new subfamily and a new genus.
Acknowledgments Zoological Journal of the Linnean Society 88:
103-142.
This research was carried out as part of Messing,C. G. 1975. Thesystematicsanddistribution
a grant awarded to the author by the Mu- oMfactrhoephCrreiantoiindae)acCoollmeacttueldibdya t(heexcRl/usVivGeerodfathien
seum national d'Histoire naturelle, Paris for the Straits of Florida and adjacent waters. Un-
July 1993. I thank Alain Crosnier for mak- published MS Thesis, University of Miami.
ing the grant available to me, and for his Coral Gables, Florida, x + 284 pp.