A NEW ECHINOID FROM THE EOCENE LA MESETA FORMATION

A NEW ECHINOID FROM THE EOCENE
LA MESETA FORMATION OF SEYMOUR ISLAND,
ANTARCTIC PENINSULA
URSZU LA RADW ANSKA
Radwariska, U. 1996. A new ec hinoid fro m the Eoce ne La Meset a Form ation of Se ym our
Island , Antarctic Penin sul a. In : A. Gaidzicki (ed.) Palaeont ologic al Result s of the Polish
An tarctic Expeditions . Part 11. - Palaeontologia Poloni ca 55 ,11 7-1 25.
A new cid aro id echinoid is described fro m the low erm ost part (U nit L Telm I ) of the La
Meseta Forma tion (Eocene) on Sey mo ur Island, Antarctic Penin sul a. It is repr esented by
se veral specimens of the new species. Austrocidaris seymo urensis sp. n., of the subfa mily
Ctenocidari nae Mort ensen , 192 8, hit herto known fro m the living form s, and one uncertain
occ urre nce from the Eoce ne of Patagoni a. An extre me ly sha llow-marine habitat the ne w
species co mes from, and bath ymetric requi rem ent s of the present -day spec ies, indi cate that
the ex tant ge nus Aus troci daris H.L. Clark. 1907, escaped a vertica l shift into grea ter depths
after the Eocene time, a featur e so typ ical of other marin e fa unas record ed in the La Meseta
For mation.
K e y wo r d s : Ec hinoidea , taxonomy, La Meseta Fo rmatio n, Tertiar y, Antarc tica .
Urszula Radwatiska , Insl)'11I/ Geo log ii Pod stawo wej U. w. . A leja tlVirki i Wig llr)' 93.02-089
WarszalVa, Pol and.
Rece ived 30 May 1995, acce pted 29 Se ptem ber 1995
118
URSZULA RADWANSKA
CONTENTS
Introdu ction
11 8
Ackn owled gements
118
Previou s re port s on the Seym ou r Island ec hino ids
119
System ati c paleont ology . . . ..
120
Ord er Cidaroida CLAUS, 1880
120
Fami ly Ci dar idae GRAY, 1825
120
Sub famil y Cten ocid arin ae MORTENSEN, 192 8
120
Genus Austrocidaris H.L. CLARK, 1907
120
Fin al co ncl usio ns
122
Refer ences
124
. . . .
INT RO DUCTION
Th e purpose of thi s pap er is to describe a ne wl y di sc o ver ed cida ro id echinoi d fro m th e La M eseta
Formation (Eoce ne) on Se ym our (Mara m bio) Isl and in the Antar ctic Peninsul a sector.
Several specime ns of reason abl y well prese rved tests, with basal parts of so me prim ar y spines adhered,
were found by Andrzej G AZDZICKI during th e Ar gentine-Poli sh field party in th e aus tra l sum me r season
of 199 3-94. The collected material represents a new spec ies, ass ig ned to the subfam ily Ct en ocidarinae
MORTENSEN, 1928 , which is poorl y represented in the fo ssil record (FELL 1966, p. U32 3) . Th e studied
echinoid material was coll ected at the locality ZPAL I, ne ar th e L6pez de Bertodan o Ba y, southwest of
Cross Vall ey (Te xt-fig. I ). This location ha s recently been named Bill Hill (GAZDZICKI and T ATUR 1994)
to honor Professor Wi lliam (Bill) J. ZINSM EISTER.
At thi s locality, g ray to red -brown limonitic sa ndy siltsto nes and sa nds tones w ith interca lations of
she lly hash and fo ssil-bearing hori zon s form up to 2 m thi ck int er val of basal faci es (U nit I, Telm I ) of
the La Me set a Formation (SADLER 1988; STILWELL a nd ZINSMEISTER 1992).
The studied echinoids, are hou sed in the C oll ecti on o f the Inst itute of Paleobi ol ogy of the Po lish
Acad em y o f Sciences, Warszaw a, und er the Catalo gu e Number s Z PAL E. VII/l -5.
Pre viou s reports on ec hino ids coll ect ed during the Pol ish A ntarc tic Exp editions (J ESIONEK -S ZYMANSK A
19 84 , 1987 ) co nce rn rath er poor specimens of Terti ary age fro m Kin g George Isl and, South Shetland
Islands. This echinoid m ateri al ca me from the so-called "Pecten Con gl om er ate" (= Lo w Head Member
of th e Pol on ez Cove Fo rm ati on ) attr ibuted to Pli ocen e, a nd late r correc ted to be of Ol igocene age
(J ESION EK -SZYMANSKA 19 84 ; BIRKENMAJER and G AZDZI CKI 19 86), and from the Cap e Mel vill e Formatio n
of Lower Mi ocene age (J ESIONEK-S ZYr-tANSKA 1987 ). O f the c ida ro ids, J ESIONEK-SZYr-IANSKA ( 198 4, 1987 )
described so me fr agm ent ary mate rial and one almost co m plete , stro ng ly weathered test of ?Notocidaris sp.
Acknowledgemen ts. - The author ex presses her most sincere th anks to Assoc . Pro f. Dr. A . G AZDZI CKI
for hi s kind invitation to study th e co llected cidaroid faunule , for survey ing all the locati on data and some
bibliogr aphic references, fo r hi s help in making SEM ph ot os, and for valua ble co mme nts which improved
the co ntent of thi s pap er. Mrs. G . DZI EWI NSK A is acknowl ed ged for making ph ot os of th e stud ied specimens .
119
A NEW ECHINOID FROM THE LA MESETA FORMATION
Cape Wiman
Lopez de Bertodano Bay
Penguin Bay
o
Ikm
~ - --~
Fig . I
Morphologic sketch-map of the northern part of Seymour Island showing the locality (ZPAL I, Bill Hill) where the studied echinoid faunule of Austro cidari s seymourensis sp. n. was collected.
PREVIOUS REPORTS ON THE SEYMOUR ISLAND ECHINOIDS
The Cretaceous and Tertiary shallow-marine sequences of Seymour Island have long been known to
yield ubiquitous fossils, quite often taxonomically unique (FELDMANN and WOODB URNE 1988). Since the
beginning of the Antarctic paleontological research the echinoids have always been noted as an important,
although usually rare, component of successive biotic assemblages on Seymour Island. The first report
was that by LAMBERT (1910) on the Upper Cretaceous Cyathocidaris, represented by three species, and
on two Tertiary irregular forms (Cassidulus, and Schi zaster) collected by the 1901-03 Swedish South
Polar Expedition (LAMBERT 1910; HOTCHKISS 1982). This was also the first report of any fossil echinoids
from Antarctica.
The Tertiary sequence of Seymour Island (Seymour Island Group) has subsequently been stated to
range from the Paleocene to possibly the Lower Oligocene (ELLlOT and TRAuTMAN 1982). The upper part
of this sequence has been distinguished by ELLlOT and TRAuTMAN (1982) as the La Meseta Formation of
late Early Eocene to possibly early Oligocene age (ZINSMEISTER and CAMACHO 1980; STILWELL and
ZINSMEISTER 1992; TAMB USSI et al . 1994). Its depositional environment has recently been interpreted by
POREiBSKI (1995) as a tectonically controlled (subsiding) incised-valley estuary.
Echinoids have been known to occur, sometimes even abundantly, in the La Meseta Formation,
although not recognized taxonomic ally (HOTCHKISS 1982, pp. 679 and 682), except for LAMBERT 'S (1910)
forms revised as Stigmatopygus and Abatus, and supplemented with a new material of the latter genus,
by McKI NNEY et al. (1988) .
To the present author's knowledge, cidaroid echinoids have not hitherto been recorded from the Tertiary
sequence of Seymour Island. Moreover, the Southern Oceans cidaroid subfamily Ctenocidarinae, to which
120
URSZULA RADWANSKA
the studied forms belong, have not been recovered from any fossil deposits of the whole Antarctica, at
least to the time of a summarizing review by HOTCHKI SS (1982, p. 681) , and except of an uncertain
occurrence in the Eocene of Patagonia (DE LORIOL 1902 ; FELL 1966 , p. U323) .
The fauna of the La Meseta Formation is composed of a wide range of diverse shallow-marine
invertebrates. The whole assemblage has been discussed by RASM USSEN (1979), FELDMANN and WOODBURNE (1988), STILWELL and ZINSMEISTER (1992), F ELDMANN (1994) , BAUMILLER and GAZDZICKI (1994,
1996 this volume). The assemblage includes numerous molluscs (gastropods and bivalves), brachiopods, crustacean decapods, balanomorph barnacles, crinoids and starfishes, many genera of which live
today only at greater depths. It has therefore been suggested that they migrated into deeper waters due
to the deteriorating climatic conditions controlled by the onset of Cenozoic glaciation of West Antarctica, the oldest spell of which is dated as the Early/Middle Eocene (BIRK ENMAJER 1992; see also
GAZDZICKI et al. 1992).
All specimens of studied cidaroids were collected from a single exposure in the basal facies of Unit I
(Telm1) of the La Meseta Formation, at locality ZPAL 1, Bill Hill (Text-fig. 1). They eo-occur with
multi lamellar bryozoans (GAZDZICKI and HARA 1994 ; HARA 1995) , brachiopods (BITNER 1996 this volume), stylasterids (STOLARSKI in preparation) and scleractinian corals (STOLARSKI 1996 thi s volume).
Among the echinoderms associated with the cidaroids at the locality ZPAL 1 important are the
excellently preserved starfishes Buterminaster elegans BLAKE reported by BLAKEand ZINSM EISTER (1988).
No less important are crinoids, described recently by BAUMILLER and GAZDZICKI (1994, 1996 this volume)
and represented in this locality by the isocrinid, Eometacrinus australis BAUMILLER et GAZDZICKI, 1996,
and the peculiarly shaped, aberrant cyrtocrinid Cyathidium holopus STEENSTRUP, 1847, the latter having
heretofore been known typically from the older Paleogene of Europe, precisely from the famous Danian
occurrence at Fakse in Denmark (RASMUSSEN 1972).
SYSTEMATIC PALEONTOLOGY
Order Cidaroida
CLAUS ,
1880
Family Cidaridae GRAY, 1825
Subfamily Ctenocidarinae MORTENSEN, 1928
Genus Austrocidaris H.L. CLARK, 1907
Austrocidaris seymourensis sp. n.
(Pis 28-31 and Text-figs 2-3)
Holotype : The specimen ZPAL E. VIUI , presented in PI. 28: la -lc.
Type horizon : Telm I , La Meseta Formation; Eocene .
Type locality: ZPAL I (Bill Hill) , Seymour Island, Antarctic Peninsula.
Derivation of the name : After a neo-Latinized adjective of the Seymour Island; in reference to the locality of the newly
established species .
Diagnosis. - Te st. Low, with narrow, sunken, naked median furrow, and characteristic pits at the
median angles in lA ; interambulacrals with a strongly elevated scrobicular ring; scrobicular tubercles
and miliaries not very numerous; bosses large and very squat; areoles deep a nd narrow; adapical
primary tubercles subcrenulate; ambulacrals slightly sinuate, one-fourth wide as the lA; pores non-conjugate, closely spaced, distinctly oblique, separated by a narrow but strongly elevated wall, non-perforate; poriferous zone as wide as the interporiferous zone of the plate; two or three ambulacral
tubercles. A p i c a I s y s t em . Small, amounting about 40 % of horizontal diameter; ocular plates
strongly convex; ocular pore situated about one-third of the plate height, near the outer angle, not
surrounded by the elevated wall. Pr i m a r y s pin e s. Short, circular in cross-section, slightly tapering; shaft covered by small thorns, longitudinally arranged.
Material. - Five, almost complete tests with few broken primary and several secondary (scrobicular)
spines adhered; Aristotle's lanterns partly preserved in position; all tests are more or less compressed; two
of them have the surface strongly abraded.
121
A NEW ECHINOID FROM THE LA MESETA FORMATION
Dimens ions (in mm):
Coil . Number
hd
vd
Number
o f/A
Number
of A per lA
Figured in
PI. 28: 1-4
Holotype
5-6
9-10
PI. 29: 1-3
(6)
6-7
9-10
PI. 30: 1-5
8
5-6
9-10
PI. 31 : I
ZPAL E. VlU4
9
6- 7
9- 10
PI. 3 1: 2
ZPALE. VlU5
7
6-7
9-10
PI. 31: 3
19
(6)
ZPALE. VIU2
23
ZPAL E. VIU3
(23)
ZPALE. VIUI
Paratypes:
Abbre viation s used: hd - horizontal diamet er, vd - vertical diameter , A plates; in brackets are measurements of compre ssed specimens.
ambulacral plate s, lA -
interambulacral
Description. - The test (PI. 28: la-lc ; PI. 30: la-lc and PI. 31: 1-3) is small, and low (compactionally
collapsed), the height exceeding one-third of the horizontal diameter. The aboral and oral sides are slightly
sunken . The edge of the peristome is slightly pentagonal in outline.
The slightly sinuate ambulacra (PI. 28: 3a-3b and PI. 29: 3b) are about one-fourth as wide as the
interambulacra; the poriferous zone is as wide as the non-poriferous part of the plate or a little wider ; the
pores are non-conjugate, placed obliquely, closely spaced together, slightly amygdaloid in outline, separ ated by a narrow, but conspicuous, raised wall, non-confluent (PI. 28: 3b). The ambulacral plates are very
narrow and sinuous in outline (PI. 28: 3b and PI. 29: 3b); the pores are large, and they cover almost the
whole poriferous zone; the upper side of the pores is narrow, but distinctly raised. The primary ambulacral
tubercle s are conspicuous. At the lower edge of the plate there occurs a smaller tubercle. Sometimes, at
the oral side there also occurs a third , miliary tubercle. The median furrow is not distinct. There are 9-10
ambu lacral plate s to each interambulacral plate at the ambitu s.
The interambulacral plates are high, numbering 6-7 in a series; the areole s are narro w and deep (PI. 29:
lc and PI. 30: 3a) ; the 2-3 proximal areoles are confluent. The perforate tubercles are large , with
prominent, swollen bosses; some adapical tubercle s are furni shed with delicate crenulation (PI. 29: 1-2).
The scrobicular ring (PI. 29: la-lc) is strongly elevated; scrobicular tubercles are prominent, not numerous; the other secondary tubercles are also not numerous, and scarcely diminishing towards the narrow,
sunken , median furrow . The region of the admedian angle s is distinctl y sunken (PI. 28: 2 and PI. 29:
la-Ic ), shaped into pits triangular in outline. The adradial and admedian zones are narrow.
The apical system is relatively small, up to about 40 % of the horizontal diameter (PI. 28: la and PI. 30:
l a). The ocular plate s (PI. 28: 4) are strongly convex, a little broader than high. The ocul ar pore is situated
at one-third of the plate height , near the outer angle. There is no elevated wall surrounding the pore , and
the tubercles cover a part of the plate , above the ocul ar pore . The genital plates (preserved inside the tests)
are regular, subtri angul ar in outline; the (?)female genital pore is large, situated near the outer edge
(Text-fig. 2); almo st the whole surface of the plate is adorned with small tubercles. The madreporite is
not reco vered .
The peristom e (PI. 28: le), slightly pentagonal in outlin e, is of the
same size as the apical system. Ari stotle 's lantern s partly preserved,
with its ossicle s (joined demip yramid s with a tooth , rotula s) kept
almo st in their life position.
The primary spines (Text-fig. 3 and PI. 30: 3-5) are short, generally shorter than the horizontal diameter of the test. They are slender,
circular, slightly taperin g. The shaft is covered by small thorns , longitudinally arranged. The neck is lmm long ; the collar is a bit shorter
than the neck , and increasing in size towards the milled ring ; the base
is of the same length as the collar (PI. 30 : 3-4). The scrobicular spines
(PI. 29: 3c and PI. 30: 2) are spatulate, flatten ed, and appressed.
Remarks. - The studied specimens are assigned to the subfamily
Ctenocidarinae MaRTENSEN, 1928, due to such feature s as the oblique,
Fig . 2
very clo sely arrang ed pore s in the ambulacrals, the mode of joining Sketch of the genital (?female) plate of
of the interambulacral plate s with a narrow, but well marked , sunken Au strocidaris seymourensis sp. n., x 6.
122
URSZULA RADWANSKA
median furrow, as well as the shape and sculpture of primary spines (MaRTENS EN 1928). An oblique and
close arrangement of pores in the ambulacrals is also known (MaRTENSEN 1928) in some representatives
of the genera Goniocidaris DESa R, 1846 and Rhopalocidaris MaRTENSEN, 1927 in the re lative subfamily
Goniocidarinae MaRTENSEN, 192 8. The studied specimens, however, differ from
the latter subfamily, by their lack of horizontal grooves in the interambulacrals,
and by the shape, length , and sculpture of their spines.
Within the subfamily Ctenocidarinae MaRTENSEN, 1928, there occur several
genera di splaying features very similar to each other, both among the present-day
forms, as well as the very few, uncertain fos sil ones (F ELL 1954 , 1966; JESIaNEKSZYM ANSKA 1984 , 1987) . This is particularly true if only the structure of the tests
and spines is taken into account. Of such genera, especially Ctenocidaris MaRTENSEN, 19 10; Eurocidaris MaRTENSEN, 1909 ; Noto cidaris MaRTENSEN, 1909;
Ogmo cidaris MaRTENSEN, 1921; and Austrocidaris H .L. CLARK , 1907, should
primarily be indicated (MaRTENSEN 1909, 1910, 192 1, 1928 ; FELL 1954, 1966;
cf. also H.L. CLARK 1907). The most important and distinctive features of their
tests and spines , and a comparison with those of the studied material are listed
in Table I .
It is worth to note, that the examined specimens are the mo st similar to tho se
of the genera Ogmocidaris and Au stro cidaris. In the present-da y faunas, these
two genera are distinguishable by the structure of their peristome plates and
pedicellarids, the both not pre servable in the fossil state.
An analysis of the structure of the tests , that is a comparable diameter of the
test and apical system, the presence of subcrenulate tubercles, and a lack of the
wall surrounding the ocular pores particularly, involved an attribution of the
studied specimens to the genu s Au strocidaris H .L. CLARK, 1907 .
In the fossil state, only one species of that ge nus has hitherto been known,
namely Au stro cidaris jorgens is (DE L oruo i., 1902) from the Eocene strata of
Fig. 3
Ske tch of th e primary Patagonia. That species ha s been recorded solely by a few isolated int erambulacral
s p i ne of Austrocidari s plates (DE Lomoi, 1902; M aRTENSEN 1910 , p. 25 and 1928, p. 141).
seymo urensis sp . n., x 3.
The specimens of A ustrocidar is sey mo urensis sp. n. differ distinctl y from the
latter, A. j orgensis (DE L omor., 1902) , by their much sma ller size, and much lower
number of secondary (scro bicular and miliary) tubercles, and probably by the narrower median furrow.
The pre servation of the tests of Austrocidaris sey mo urensis sp. n. that bear the spines adhered and
Aristotle 's lanterns nearly in po sition sug gest their rapid burial, most lik el y du e to such a hydrodynamic
agent, as e.g . storm agitation and deposition.
Occurrence. - Seymour Island, La Me seta Formation : ZPAL I (B ill Hill ), Telml.
FINAL CONCLUSIONS
The subfamily Ctenocidarinae MaRTENSEN, 192 8, to whi ch the newl y es tablished species A ustrocidaris
sey mourensis sp. n. belongs, is con fined tod ay to the circum-Antarcti c region (FELL 1966) where it
appeared alr eady in the Eocene of Patagonia (DE L oaroi. 1902; noted wi th a question mark by FELL 1966,
p. U323) and of the herein reported Seymou r Island , havin g not yet bee n recog nize d fro m intermediate
ages.
Within this region, the representatives of the family Cidar idae GRAY, 1825, are typical co mpo nents of
all the echinoid faunas (MaRTENSEN 1909 , 192 1, 1928 ; FELL 1954 ). No teworthy is not onl y their taxonomic
variability, but also a very peculiar behavior and/or morphologic adap tat ion, prim aril y ex pressed by th e
parental care of their broods, as first reco gni zed i.a. in A ustro cidaris and illustrated by W YVI LLE-T Ha MSa N
(1876; re-figured e.g. by Ma RTENSEN 1928, fig. 25/2 , and FELL 1966, fig. 241/3). The bro odin g may result
in modification of the arch itecture of the tests, to produ ce very specialized brood structures (ma rsupia)
and individualize the marsupi ate type of the cida ro id tests, and to create separate taxa, eve n at the ge nus
level. Such marsupiate cidaroids appea r on Se ymo ur Island as ea rly as the uppermost Cretace ou s (Maastrichtian) as has been recently demonstrated by BLAKE and ZINSMEI STER ( 199 1), who describ ed a un iqu e
123
A NEW ECHINOID FROM THE LA MESETA FORMATION
female specimen of a new taxon Almu cida ris durhami BLAKE et ZINSM EISTER, in which all five genital
plates have been transformed into deep brood ch ambers.
Variou s non-cidaroid marsupiate echinoids are also quite common in Eocene strata of south-eastern
Au stralia (PHILIP and Fo sTER 1971). It is thus highly probable that the marsupiate forms of cidaroids, the
studied genus Austrocidaris and its new species including, may also be present in the La Meseta Formation
on Seymour Island.
It is also hoped that future collecting in the La Meseta Formation on Seymour Island may provide
more echinoid material to study the phylogeny, behavioral evolution and/or migration of the extant taxa,
to comply the echinoid data with those of other echinoderms from the La Me seta Formation, including
the starfishes (BLAKE and ZINSM EI STER 1988), and the crinoids (M EY ER and On 1993; BAUMILLER and
GAZDZICKI 1994, 1996 thi s vo lume) .
Finally, it is reasonable to record that of all the genera of the subfamily Ctenocidarinae MORTENSEN,
1928, the only genus found in shallow-marine en vironments (MORTENSEN 1909, 1910, 1921; FELL 1954)
is Au strocidaris. It wa s MORTENSEN (1910, pp . 17-1 8) who recorded Au stro cidaris fro m low wat er s,
commonly on stony bottoms with algae, down to sublittoral depths (10-17, maximum 40 m). Thus,
understandable is the presence of the ne wl y established species A. seymourens is sp . n. in the ba sal facies
of the La Me set a Formation (Unit I , Telml ) which have always been regarded as shallow, or even
extremely sha llow-marine (SADLER 1988), and recently interpreted as es tua rine (PORI;BS KI 1995). Among
other echinoderms associated with the studied faunule of A. seymourensis sp. n., cons istent with that
stat ement is the pre sence of the aforementioned crinoid Cyath idium holopus STEENSTRUP, 1847, which in
its type locality of Danian age in Denmark lived in shallow waters , within the photic zone , although in
cryptic habitats (RASMUSSEN 1972). The present-day occurrence of thi s species is, however, confined to
mu ch greater depths, not lesser than 380 m (R ASM USSEN 1972). Similarly di stributed is also the crinoid
genus Meta crinus, living today at depths not lesser than 96 m (BAUMILLER and GAZDZICKI 1994), while
the closely related Eometacrinus australis BAUMILLER et GAZDZICKI, 1996, lived in the sam e setting as
Au strocidaris seym ourensis sp . n. On the other hand, the comatulid Notocrinus seym ourensis BAUMILLER
Table I
Dist incti ve fea tures of the tests and spines of so me ge nera included into the subfam ily Ct enocidarinae MORTENSEN, 1928,
to co mpare with those of the studied Aust rocidaris species. Co mpi led after the referen ced papers (CLARK 1907 ; MORTENSEN, 1909, 1910, 192 1, 1928; FELL 1954, 1966).
~s
Austrocidaris
Austrocida ris
seymourensis sp.n.
Ctenocidaris
Eurocidaris
Notoc ida ris
Ogmocidaris
hei ght of the test
low
low
low
low
low
low
number of lA plates
8-9
6-8
5-7
6-7
6-8
6-7
number of A per lA
pl ates
5-6
6-7
6-7
8-9
5-8
9- 10
C haracters
45%
45%
55%
55%
40%
40%
obliq ue.
confluent
oblique .
co nflue nt
oblique,
co nfluent
obliq ue,
non- confl uent
oblique,
non -conflu ent
oblique,
non -confluent
tub ercles
no traces
of cre nulation
no traces
of cre nulation
no traces
of crenulatio n
no traces
of crenulation
upper
tub ercle s
subcre nulate
upper tube rcl es
subcrenulate
medi an furrow in lA
not sharply
we ll mark ed
no naked
naked sunken we ll marked
na ked, sunke n
narrow medi an
median furrow
med ian furrow medi an furrow
median furrow
furrow
well marked
nar row medi an
furro w
median furro w in A
we ll mark ed
no naked
no naked
no naked
median furrow medi an furro w medi an fu rrow medi an furro w
usuall y we ll
mar ked
medi an furro w
(?) no nak ed
medi an furro w
oc ular pore
surro unded by surro unded by surro unde d by
elevated wall eleva ted wa ll e leva ted wa ll
not we ll
not surro unde d
marked
by wall
ele vate d wa ll
not surro unde d
by wa ll
long, two or
th ree tim es
as long as hd
lon g, tw o or
ge ne rally shor t
three times
(= hd)
as lon g as hd
sho rt
(lesser than hd )
apical sys tem
ambulacral pores
primary spines
shor t (= hd),
with tho rns
short (= hd ),
with thorn s
124
URSZULA RADWANS KA
et GAZDZICKI, 1996, known fro m the Telm2, the locality ZPAL 6 situated (BAUM ILLER and G AZDZICKI
1994 , 1996 thi s vo lume), nearl y that o ne yielding Austrocidaris seymourensis sp. n. belongs to the genus
which is found today in Ant arctic sha llow shelf water s very clo se to Seymour Island co asts (MEYER and
011 1993). Thi s suggests th at some echino de rrns, such as the cidaro id Austrocidaris and the co matulid
crino id Notoc rinus, which were compone nts of fauna l assemblages of the La Me seta Formation on
Seymour Island , have escaped the ge nera l trend of an offs hore shift into oceanic depths since post-Eocene
tim e, and have managed to surv ive in shallo w waters since the onse t of glac ial co nditions in Antarctic a.
REFERENCES
BAUMILLER, T K. a nd GAZDZICKI, A. 1994 . C rino ids from the lo wer part of th e La Meseta Form ation (Eoc e ne) . An ta rctica .
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Palaeontologia Polonica, No. 55, 1996
U. RADWANSKA: A NEW ECHINOID FROM TH E EOCEN E LA MESETA FORM ATION
OF SEY MOU R ISLAND, ANTARCTIC PENINSULA
PLATE 28
Austrocidaris seymourensis sp. n.
120
Fig. I. Test, a - abora l view, b - lateral view, c - oral view; x 3.
Fig. 2. Interambul acrum with narrow, sunken median furrow.
Fig. 3. Ambulacrum , a - ambulacrum with associated interambul acral plates, b - ambulacral plates with non-conju gate pores.
Fig. 4. Ocul ar plate.
Holotype ZPAL E.VII/I, ZPAL 1, Telml , magnification in SEM photos (Figs 2-4) indicated by bars.
Palaeontologia Polonica, No. 55, 1996
U. RADWANSKA: A NEW ECHINOID FROM THE EOCENE LA MESETA FORMATION
OF SEYMOUR ISLAND. ANTARCTIC PENINSULA
Pi. 28
Palaeontologia Polonica, No. 55, 1996
U. RADWANSKA: A NEW ECHINOID FROM THE EOCENE LA MESETA FORMATION
OF SEYMOUR ISLAND, ANTARCTIC PENINSULA
PLATE 29
Austrocidaris seymourensis sp. n.
120
Fig . I . Interambulacrum, a - interambulacral plate with perforate tubercle (arrowed), b - interambulacral plate with
swollen boss and narrow areole, c - interambulacral plate with e levated scrobicular ring.
Fig . 2. Adapical interambulacral tubercle with delic ate crenulation.
Fig . 3. Ambulacrum, a - ambulacrum with associated interambulacral plate s and ocular plate , b - aboral part of
ambulacrum, c - interambulacral tubercle with adhered scrobicular spine s.
Holotype ZPAL E.VII/l, ZPAL I, Telm l , magnification in SEM photos (Figs 1-3) indicated by bars.
Palaeontologia Polonica, No. 55, 1996
U. RADWANSKA: A NEW ECHINOID FROM THE EOCE NE LA MESETA FORMATION
OF SEYMO UR ISLAND, ANTARCTIC PENINSULA
PI. 29
Palaeontologia Polonica, No. 55, 1996
U. RADWANSKA: A NEW ECHINOID FROM THE EOCENE LA MESETA FORMATION
OF SEYMOUR ISLAND, ANTARCTIC PENINSULA
PLATE 30
Austrocidaris seymourensis sp. n.
120
Fig. I. Test, a - aboral view, b - lateral view, c - oral view; x 3.
Fig. 2. Fragment of primary spine with appressed scrobicular spines.
Fig. 3. Fragment of primary spine attached to tubercle, a - interambulacrum with spine, b - close-up of spine base.
Fig. 4. Fragment of primary spine, a - basal part of spine, b - base, collar, neck and fragment of shaft.
Fig. 5. Cross-section of primary spine.
Paratype ZPAL E.VII/2, ZPAL 1, Telml, magnification in SEM photos (Figs 2-5) indicated by bars.
Palaeontolo gia Polonica, No. 55, 1996
U. RADWANSKA: A NEW ECHINOID FROM THE EOCENE LA MESETA FORMATION
OF SEYMOUR ISLAND, ANTARCTIC PENINSULA
PI. 30
Palaeontologia Polonica, No. 55. 1996
U. RADWANSKA: A NEW ECHINOID FROM THE EOCENE LA MESETA FORMATION
OF SEYMOUR ISLAND, ANTARC TIC PENINSULA
PLATE 3 1
Austrocidaris seymourensis sp . n.
Fig . I. Test, a - abora l view, b - oral view ; ZPAL E.VIII3 (paratype) , ZPAL 1, Telml, x 3.
Fig . 2. Test, a - abora l view, b - latera l view, C - oral view; ZPAL E.VIII4 (paratype) , ZPAL I, Telm I, x 3.
Fig . 3. Test, a - aboral view, b - lateral view, C - oral view; ZPAL E.VII/5 (paratype), ZPAL I, Telm I, x 3.
120
Palaeontologia Poloni ca, No. 55, 1996
U. RADWANSKA: A NEW ECHINOID FROM THE EOCENE LA MESETA FORMATION
OF SEYMOUR ISLAND, ANTARCTIC PENINSULA
PI. 31

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