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HARVARD UNIVERSITY
Library of the
Museum of
Comparative Zoology
SAaj
REMIPEDIA. PART I. SYSTEMATICS
FREDERICK R. SCHRAM*
JILL YAGER**
AND
MICHAEL J. EMERSON* I IBR^?Y
*San Diego Natural History Museujrijj ^ ^ ^qpr
San Diego, California 92112
HARVARD
*Old Dominion University, UNIVERSITY
Norfolk, Virginia 23508
SAN DIEGO
SOCIETY OF NATURAL HISTORY
MEMOIR 15
1986
REMIPEDIA. PART I. SYSTEMATICS
FREDERICK R. SCHRAM*
JILL YAGER"
AND
MICHAEL J. EMERSON*
*San Diego Natural History Museum,
San Diego, California 92112
**Old Dominion University,
Norfolk, Virginia 23508
SAN DIEGO
SOCIETY OF NATURAL HISTORY
MEMOIR 15
5 June 1986
Speleonecies ondinae, ventral surface. Animal swimming and executing a 180° turn. From a photograph
by Dennis Williams.
Table of Contents
SYNOPSIS 4
INTRODUCTION 5
SYSTEMATICS 6
Speleonectes lucayensis 6
Speleonectes ondinae 16
Lasionectes entrichoma 23
Godzillius robustus 41
Tesnusocaris goldichi 51
DISCUSSION 53
ACKNOWLEDGMENTS 59
REFERENCES 59
SYNOPSIS
The order Nectiopoda is a relatively new taxonomic addition to crustacean biology. First
collected during the early 1980s from caves in the Bahamas and Turks and Caicos Islands,
these living representatives of the apparently ancient class Remipedia are known from
analogous habitats on both sides of the Atlantic.
The three known nectiopodans are reviewed here, and one species is described: Godzillius
robustusgen. & sp. nov., sole representative of the Godzilliidae. A detailed, illustrated analysis
of each species, based on SEM and light microscopy, is given with known data on natural
history, distribution, and relationships within the Nectiopoda. A new study of the Carbon-
iferous fossil Tesnusocaris goldichi Brooks from West Texas reveals additional details of
cephalic morphology in the monotypic order Enantiopoda that suggest a closer affinity with
the living nectiopodans than previously indicated.
These five living and fossil species are compared with each other and all other Crustacea,
using cladistic analysis to identify the most parsimonious relationships possible. The resulting
implications for crustacean evolution are discussed with reference to existing theories.
Remipedia. Part I. Systematics
Frederick R. Schram,' Jill Yager- and Michael J. Emerson'
INTRODUCTION
In 1981, Yager described a new crustacean from
Lucayan Cavern, an anchialine cave in Grand Ba-
hama. It was so unlike any other known crustacean
that establishment of a new class was necessary, the
Remipedia. This animal, Speleonectes lucayensis,
seemed to bear some resemblance to a problematic
Carboniferous species, Tesnusocaris goldichi Brooks
(Schram 1983a), which had been placed in its own
order Enantiopoda (Birshtein 1960). Though the two
animals are distinct, the overall similarities proved
so striking that a sister group relationship was in-
dicated, and Schram ( 1 986) erected a separate order,
the Nectiopoda, for the speleonectids allying both
groups within the class Remipedia.
Since the first remipede was described, other nec-
tiopodan taxa have been discovered from the West
Indies and the Canary Islands (Garcia- Valdecasas
1984, Yager and Schram 1986). Several features of
all these taxa, fossil and living, denote these as a
most intriguing group. The complete lack of tag-
mosis in the trunk, as well as the serial nature of
several organ systems (such as limbs, gut, and pos-
sibly reproductive system and cephalic glands) marks
the remipedes as among the most primitive of known
crustaceans (Schram 1986). The phylogenetic im-
portance of this group requires a detailed series of
diagnoses and descriptions for the known taxa, based
on more extensive materials than was available be-
fore. A summary taxonomy of the class as currently
understood is as follows:
Phylum Crustacea Pennant, 1777
Class Remipedia Yager, 1981
Order Nectiopoda Schram, 1986
Family Speleonectidae Yager, 1981
Family Godzilliidae new
Order Enantiopoda Birshtein, 1960
Tesnusocarididae Brooks, 1955
An analysis of internal anatomy will follow in Part
II of this monograph. It will be based on study of
Lasionectes entrichoma. the only nectiopodan so
far known from sufficient numbers of specimens to
allow for sectioning and staining of many individ-
uals.
The present study is concerned only with the de-
scription and analysis of adult nectiopodans. Ap-
parently, these animals reach maturity when the body
grows to approximately 30 trunk segments. At that
size the animals have developed the trunk pleural
lobes, into which the midgut diverticula extend. Pre-
liminary study of serial sections of Lasionectes en-
trichoma indicates that nectiopodans may be her-
maphroditic. Several localities have yielded
specimens of juvenile Nectiopoda (see table 5), but,
these exist in insufficient numbers for a detailed
study at this time.
Specimens of Remipedia are located in several
different collections. These are indicated by a prefix
to the catalog numbers as follows:
K — Zoologisches Institut, Hamburg, West
Germany.
MNCN — Museo Nacional de Ciencias Naturales.
Madrid. Spain.
SDSNH —San Diego Society of Natural History,
Crustacean collections.
USNM —National Museum of Natural History,
Washington, Crustacean collections.
USNMP— National Museum of Natural History.
Washington. Paleobiology collections.
' San Diego Natural Historv Museum, San Diego, California
92112.
- Old Dominion University, Norfolk, Virginia 23508.
Additional material was also used from Yager's pri-
vate collection, and is so designated when refer-
enced.
Schram, Yager and Emerson
SYSTEMATICS
Class REMIPEDIA Yager, 1981
£)/a^«05W.— Crustaceans without trunk tagmosis;
lacking carapace but possessing well-developed
subquadrangular cephalic shield: labrum well de-
veloped, forming large atrium oris behind mouth;
(?) mandibles lacking palps; raptorial posterior
mouthparts; biramous, paddle-like trunk limbs, rami
of trunk limbs with three or more segments.
Remarks. —The query on mandibular palps is dis-
cussed below under Remarks on Tesnusocans gold-
ichi.
Order NECTIOPODA Schram, 1986
Genus SPELEONECTES Yager, 1981
Speleonectes Yager, 1981:328.
Morlockia Garcia- Valdecasas, 1984:329.
Diagnosis.— T\i\T<i endite of maxillule large with
robust setae, fourth endite moderately developed
and bearing pair of robust apical setae; second endite
of maxillae with long simple setae as well as apical
seta; maxillae and maxillipedes prehensile, with long
simple setae on distal segments of limb, terminal
claws developed as horseshoe-shaped scraper with
dense comb-like row of spines (Fig. 7).
Type species.— Speleonectes lucayensis Yager,
1981.
Diagnosis. —No eyes; cephalon with ventral,
spined frontal processes; large biramous antennules
with basal pad of aesthetascs; paddle-like biramous
antennae; mandibles "internalized" into atrium oris;
maxillules, maxillae and maxillipedes as well-de-
veloped, uniramous, raptorial mouthparts with el-
bows; maxillules with terminal claw or "fang," basal
maxillulary endites functioning in place of "exter-
nal" mandibles; maxillae with basal complex of three
digitiform endites; maxillipedal segment fused to
cephalon; trunk limbs ventro-laterally directed from
body, gonopores located on bases of fourteenth trunk
limbs; anal segment with simple oval caudal rami.
Family SPELEONECTIDAE Yager, 1981
(=Morlockiidae Garcia- Valdecasas, 1984)
Diagnosis.— Head shield subrectangular; ventral
ramus of antennules with many segments; antennal
segments generally with single rows of setae along
margins, except for double row along distal edge of
third endopodal segment; mandibles markedly
asymmetrical; maxillule second segment with broad,
ventral, pad-like setose, endite; maxillule third seg-
ment as broad, long, subtriangular endite; maxillae
with four segments beyond elbow of limb; maxil-
lipede basal endite broad and pad-like, with five
segments beyond elbow of limb; posterior trunk seg-
ments generally without sternal plates, but with dif-
ferentiated sternal bars.
Remarks.— The collection of more material of
Speleonectes lucayensis, as well as recognition of an
additional family of nectiopodan remipedes allows
a more detailed diagnosis to be provided here than
was possible by Yager (1981).
SPELEONECTES LUCAYENSIS Yager, 1981
Speleonectes lucayensis Yager 1981:328.
Diagnosis.— Apical setae on mouthpart endites
robust and without subsetules; stemite bar on four-
teenth trunk segment with sub-triangular flaps ex-
tending over genital pores located on limb protopod;
posterior trunk segments with stemite bars some-
what wide and convex posteriorly.
Holotype. -VSNM 184343, coll. March 13, 1980.
Type locality. —Lucayan Cavern, Grand Bahama
Island.
.Additional material.— Yager Private Collection,
3 adults, from type locality, coll. between Oct. 1 979-
Nov. 1980. SDSNH 2189, from type locality, coll.
Nov. 10, 1983.
Description. —The cephalon is approximately '/i.
the total body length (Fig. lA). The cephalic shield
tapers anteriorly where it bears a faint median trans-
verse groove in addition to a prominent transverse
groove about midlength on the head shield. The
adult animal has 29 to 32 free segments in the trunk.
The tergite of the first trunk segment is reduced in
size from those which follow, and is usually partially
covered by the posterior margin of the cephalic
shield. The trunk segments are produced laterally
as prominent pleurites that are rounded anteriorly
and somewhat concave posteriorly. The last tergite
is reduced and appears to be partially fused to the
anal segment. The stemites of the trunk segments
are reinforced with well-developed transverse bars.
The bar on the fourteenth segment bears sub-tri-
angular flaps that extend over the genital pores lo-
cated on the bases of the limb protopods. The sternal
bars posterior to the fourteenth segment are some-
Remipedia Systemalics
3mm
B-C-D
400 ym
E
500 jjm
caudal ramus
Fig. 1 . Speleonecles lucayensis. A) dorsal surface of body; B) posterior view of first trunk limb; C) tenth trunk limb, with x. y, and
z as variant setal types; D) twenty-eighth trunk limb; E) anal segment with caudal rami.
Schram, Yager and Emerson
Fig. 2. Speleonectes lucayensis. A) left frontal filament, lateral view; B) left antennule. anterior view; C) left antenna, ventral view,
with X as plumose seta on margins.
what concave on their posterior margins, but at about
segment 26 the bars become distinctly convex pos-
teriorly and have an almost subtriangular form. The
anal segment (Fig. IE) is slightly longer than wide.
The caudal rami are slightly shorter than the length
of the anal segment. The caudal rami terminate in
tufts of about six simple setae, and bear two or three
simple setae along their median margins. Measure-
ments of specimens are provided in Table 1.
There is a small pair of frontal processes (Fig. 2 A)
on the anterior part of the ventral cephalon, located
near the base of the antennules. They are rod-like.
Remipedia Systematics
1 acini a
mobil is
molar
process
Fig. 3. Speleonectes lucayensis. A) labrum, venlral surface; B) left mandible dorso-postenor view with enlargement; C) nght mandible
dorso-posterior view with enlargement.
terminally tapered, and equipped with thumb-like
spines about halfway along their length (Fig. 6A).
The biramous antennules (Fig. 2B) are very well-
developed and somewhat ventro-laterally directed.
The peduncle is composed apparently of two arti-
cles, though the separating suture is not well devel-
oped. The proximal joint is enlarged ventrally to
accommodate a pad that bears a battery of closely
packed rows with from two to four long aesthetascs
per row (Fig. 6 A, B). These aesthetascs extend pos-
teriorly towards the labrum and cover the antennae.
The distal segment of the antennular peduncle is
bifurcate, each branch bearing a flagellum. The dor-
sal flagellum is robust and composed of 1 2 segments.
The ventral flagellum is shorter than the dorsal by
half and is composed of eight segments. Each seg-
ment of these flagella has a tuft of two to four short,
simple setae on the disto-ventral margin, in addition
to scattered setae along the shafts of each segment.
Both flagella terminate in tufts of short simple setae.
The biramous antennae (Fig. 2C) are moderate in
size. The protopod has two articles, the proximal
joint is somewhat longer than the distal unit, and
the line of articulation between the two articles is
somewhat oblique. The proximal segment of the
protopod is equipped with a row of 5 short setae
along the median margin, whereas the distal joint
has a row of seven short to moderate setae. The
exopod is an oval scale extending medially and pos-
teriorly from the second protopod segment. It bears
along its margins about 21 setae, the bases of which
are more robust than the distal shafts. The endopod
is composed of three broad, subequal segments which
arc laterally from their origin on the distal aspect of
the protopod. Each segment is equipped with setae
along its margins; the most proximal with approx-
10
Schram, Yager and Emerson
endites I
Fig. 4. Speleonectes lucayensis. Right maxillule, posterior surface, with I-IV and c providing details of designated endites and limb
tip.
imately seven, the next with about eight, and the
most distal with 19. These distal 19 are not in a
single row, rather 10 are arranged in a double row
along the distal margin, whereas the proximal an-
terior and posterior margins of this segment bear
single rows of setae. All the setae on the antennal
segments are plumose (Fig. 2C-x).
The labrum (Fig. 3A) is a large fleshy structure.
It narrows anteriorly to form a subtriangular portion
marked off posteriorly by a slight furrow. The bul-
bous posterior portion extends over the mouth
proper to form an atrium oris. The posterior margin
of the labrum bears a median setose lobe.
The mandibles (Fig. 3B, C) are asymmetrical. They
take origin on the side of the cephalon and extend
ventrally under the posterior lobe of the labrum into
the atrium oris. The molar processes are located on
pedestals, and are composed of broad flat basins
covered with a dense row of spines. The left incisor
process is a row of four large denticles. The right
incisor process is formed by a row of three large
denticles. Between the incisor and molar processes
are prominent laciniae mobiles; that on the left is
concave and sickle-like, that on the right is formed
by a row of three large denticles.
The paragnaths flank the atrium oris, and are cov-
ered by fine, densely packed setae.
The maxillules (Fig. 4) are very robust, unira-
mous, prehensile, and seven-segmented. Segments
one to four are equipped with robust endites (Fig.
6C). Although all segments are capable of move-
ment in relation to adjacent segments, the principal
point of flexure for an elbow occurs between seg-
ments four and five. The first four segments bear
one endite each. The most proximal of these (Fig.
4, endite I) terminates in a stout spine, adjacent to
Remipedia Systematics
11
200 pm
Fig. 5. Speleonectes lucayensis. A) left maxilla, anterior surface, with c as postero-oblique view of limb tip; B) left maxillipede,
anterior view, with cl as anterior view of limb tip.
12
Schram. Yager and Emerson
Table 1. Representative measurements in mm of Speleonectes
lucayensis. Not all dimensions could be measured on all the
specimens at hand.
Feature
Range
n
.V
s
V
Body length
15.0-23.8
3
20.0
4.5
+
3.2
22.5
Head length
1.5-2.5
4
2.0
0.4
+
0.2
20.0
Head width
1.6-1.8
2
1.7
0.1
+
0.1
5.9
Trunk segs.
29-32
4
30
1.3
±
0.7
4.3
Tl length
0.3-0.4
3
0.4
0.1
+
.04
25.0
Tl width
1.2-1.2
-)
1.2
T2 length
0.4-0.5
4
0.5
0.1
+
.04
20.0
T2 width
1.4-1.9
3
1.6
0.2
±
0.2
12.5
T14 length
0.6-0.8
4
0.7
0.1
+
0.1
14.3
T14 width
1.4-2.1
3
1.8
0.4
+
0.2
22.2
Anal seg. length
0.5-0.6
4
0.5
0.1
+
O.I
20.0
Anal seg. width
0.3-0.6
3
0.5
0.2
+
0.1
40.0
Caudal ramus length
0.3-0.5
4
0.4
0.1
+
.05
25.0
Caudal ramus width
0.1-0.2
4
O.I
.05
+
.03
50.0
which is a row of six stout simple setae. The next
endite (Fig. 4, endite II) is rather broad and flap-
Hke; the proximal margin has three simple setae, the
distal margin has four long simple setae, and the
apical margin has eight to nine robust spine-like
setae each flanked by small simple setae. The third
segment of the limb has two short, robust setae at
the apex of its cone-like endite (Fig. 4, endite III).
The flanks of the cone have six slender, simple setae
scattered around the anterior and posterior surfaces.
The fourth segment is relatively long, and bears a
large lobate endite (Fig. 4, endite IV) that has a
single, robust seta at its apex. This apical seta, when
the segment is flexed, interlocks with the two apical
setae on endite III (Fig. 6C). Distal to the apical seta
on endite IV are 12 variously short and long simple
setae extending in rows toward the articulation with
the fifth segment. The fifth segment has a cluster of
six to eight simple setae on the disto-ventral surface
of the segment. The sixth segment has a cluster of
eight simple setae about -h the length of the joint on
the ventral surface and another cluster of eight sim-
ple setae along the anterior aspect of the disto-dorsal
margin of the segment. The seventh joint terminates
in a prominent talon-like structure (Fig. 4, inset)
which is surmounted by a large pore. At the base of
this claw, along the ventral surface of the segment,
is a cluster of seven medium to large simple setae.
The maxillae (Fig. 5A) are robust, uniramous,
prehensile limbs, composed of seven segments. The
principal point of flexure occurs between the third
and fourth segments. The first segment is relatively
long and bears a series of three endites (Fig. 5A,
endites I to III). The first endite is small and has a
modestly robust simple seta at its apex, and two
short simple setae proximally. The second endite is
modest in size and has a robust simple seta at its
apex, and three short simple setae proximally. The
third endite is relatively large, has a robust, simple
seta at its apex that is flanked proximally by a row
of four or five small simple setae, and distally by a
row of three large simple setae. The second segment
of the limb is almost thumb-like and bears a large,
lobe-like endite. This endite is surmounted by a
small, spine-like seta that is abutted distally along
the margin of the endite by a row of about 1 2 densely
packed moderate to long simple setae. The third
segment of the limb is very long, and has its ventral
surface developed as an arcuate double crested en-
dite. Each crest is marked by a row of 14 to 15
moderate to long simple setae. The third to sixth
segments decrease in length as one proceeds distally
in the series. These segments do not have endites,
but do bear rows of moderate to long simple setae
along their ventral margins. The seventh segment
terminates in a distinctive claw composed of a row
of densely spaced spines arranged in an arcuate or
horseshoe-shaped crest. This spine row is opposed
by a setose thumb-like pad. Between the setal pad
and the spine row on the posterior surface of the
claw is a separate arcuate spine (Fig. 5A-c).
The maxillipedes (Fig. 5B) are very long, unira-
mous, robust, prehensile limbs composed of eight
segments. The principal flexure occurs between the
third and fourth segments. With the exception of
the basal endites, these limbs are very similar in
form to that of the maxillae. The two most proximal
segments each bear a weakly developed endite with
moderate to long simple setae. The endite of the
second segment is somewhat better developed than
that of the first. The third segment bears an arcuate,
double-crested endite, each crest with 16 to 18 mod-
erate to long simple setae along its length. The fourth
through seventh segments are progressively shorter
as one proceeds distally in the series, and each seg-
ment has a row of moderate to long setae along its
medial edge. The eighth segment of the limb is
equipped with a distinctive claw identical to that
seen on the maxilla terminus (Fig. 5B-cl; Fig. 7 A,
B).
The trunk limbs are all biramous and nearly ho-
monomous in form. The first limb has somewhat
narrower rami than those which follow (Fig. IB).
The majority of the trunk limbs have broad sub-
rectangular to oval segments on the rami (Fig. IC).
The most posterior limbs in the series, while bira-
mous, are somewhat less setose than the larger an-
terior limbs, and are also smaller in size. All trunk
limbs present a basic similarity in regard to the ar-
Remipedia Systematics
13
Fig. 6. Speleonectes lucayensis. A) anterior view of front edge of cephalon (specimen cut along midline), with anterior margin of
head shield in front of frontal filament and aesthetascs of antennule behind; B) lateral view of A, showing pad of aesthetascs at base
of biramous antennules; C) endites of maxillule (numbered I-IV), note apical setae on endites III and IV lack subsetules; D) comb
seta of tenth trunk limb.
14
Schram, Yager and Emerson
Fig. 7. Speleonectes maxilla and maxillipede limb tips. A, B) S. lucayensis maxillipede. A) lateral oblique view, B) ventral view; C,
D) S. ondinae maxilla, C) lateral oblique view, D) lateral view.
Remipedia Systematics
15
exopod
endopod
600 pm
Fig. 8. Speleonectes ondinae. A) dorsal surface of body, B) posterior view of first trunk limb, with x as comb seta; C) fourteenth
trunk limb, with y as plumose seta of margins and genital flap on protopod; D) last trunk limb; E) anal segment with caudal rami.
16
Schram, Yager and Emerson
Table 2. Representative measurements in mm of available
specimens of Speleonecles ondinae.
Feature
Range
n
.V
s
V
Body length
8.3-16.1
6
11.2
2.7
+
1.2
24.1
Head length
1.2-2.2
6
1.6
0.3
+
0.1
18.8
Head width
0.7-1.5
6
1.2
0.3
+
0.1
25.0
Trunk segs.
19-25
6
21
2.2
-t-
1.0
10.5
Tl length
0.2-0.4
6
0.3
.08
±
.04
26.7
Tl width
0.3-1.1
6
0.8
0.3
+
0.1
37.5
T2 length
0.3-0.6
6
0.4
0.1
+
.04
25.0
T2 width
0.7-1.5
6
1.0
0.3
+
0.1
30.0
TI4 length
0.4-0.8
6
0.6
0.1
+
.06
16.7
TI4 width
0.7-1.6
6
1.1
0.3
+
0.1
27.3
Anal seg. length
0.3-0.4
6
0.4
.05
+
.02
12.5
Anal seg. width
0.3-0.6
6
0.4
0.1
+
.05
25.0
Caudal ramus length
0.4-0.8
6
0.7
0.2
+
.07
28.6
Caudal ramus width
0.1-0.2
6
0.2
.04
+
.02
20.0
rangement of different setal types on the rami. The
most prominent setae are of the large plumose type
and occupy most of the margins of the segments
(Fig. lC-.\). A second type of seta has a comb-like
form (Fig. IC-y) in which a tall tapering shaft has
round processes arranged along the margins of the
shaft. The base of the seta is marked by a fan or
crest of densely arranged comb-like spines (Fig. 6D).
These distinctive comb setae are placed on the distal
corners of the intermediate rami of the trunk limbs.
They resemble similar comb-like setae in other
groups of crustaceans that appear to be used in
combing out or carding the subsetules of plumose
setae. One additional kind of seta is noted on the
disto-median comers of the two proximal segments
of the endopods on the middle segments of the body.
These are short, simple, spine-like setae (Fig. IC-
z).
Remarks. —The above description is considerably
more detailed than that found in Yager (1981). This
is due not only to the fact that more material of this
species is now available, but also to new insight into
understanding the anatomy of the species, derived
from the discovery of additional taxa of nectiopo-
dans.
SPELEONECTES ONDINAE
(Garcia-Valdecasas), 1984
Morlockia ondinae Garcia-Valdecasas, 1984:329.
Diagnosis. — KohusX apical setae on endites of
mouthparts with subsetules (Fig. 13C); fourteenth
limb protopod with subtriangular flap over opening
to gonopore; no differentiation of posterior stemite
bars; rami of trunk limbs with segments longer than
broad.
Holotype. -M'^ClSi 14-VIII-84.
Type locality. — Tunel de la Atlantida, Jameos del
Agua, Lanzarote, Canary Islands.
.Additional material (examined by us). — USNM
216979 (dissected for SEM), K 32945-7. Yager Pri-
vate Collection, 6 specimens, coll. from type locality
between 1982-1984.
Description.— The cephalon is approximately %
the total length of the body (Fig. 8A). The cephalic
shield tapers only slightly anteriorly; it bears a faint
transverse groove about mid-length, and also a pair
of short lateral grooves at the extreme anterior end
of the cephalon. The animals at hand have 19 to 25
trunk segments (Table 2), with a mode of 20. The
first tergite of the trunk is reduced in length and
width over those that follow, and it is partially cov-
ered by the posterior margin of the cephalic shield.
The trunk segments are produced laterally as broad-
ly rounded pleurites, including the last tergite, which
has moderately prominent pleura. The stemites of
the trunk are reinforced with well-developed bars
that are not particularly differentiated from each
other along the length of the body (Frontispiece).
The anal segment is wider than long (Fig. 8E). The
caudal rami are somewhat longer than the anal seg-
ment, terminate in tufts of four simple setae, and
bear two or three simple setae along their median
margin. Measurements of available specimens are
provided in Table 2.
There is a pair of short and relatively robust fron-
tal processes (Fig. 9A) on the anterior part of the
cephalon near the base of the antennules. These pro-
cesses are almost club-like, terminally rounded, and
have a small, thumb-like spine that arises halfway
along their length.
The biramous antennules (Fig. 9B) are well de-
veloped, ventro-laterally directed, and extend well
beyond the cephalon. The peduncle is composed of
two segments, though the separating suture is weakly
developed. The proximal joint bears a large pad
ventrally, which contains a battery of closely packed
rows of long aesthetascs. These extend posteriorly
over the antennae. The distal segment of the pe-
duncle is somewhat bifurcate terminally where the
flagella attach. The dorsal flagellum is the longer,
and is composed of 1 2 articles. The ventral flagellum
is composed of eight joints and is less than half the
length of the dorsal ramus. Each segment of these
flagella bear tufts of at least four simple setae along
their disto-ventral margins, and both rami termi-
nate in a tuft of three or four simple setae.
The biramous antennae (Fig. 9C) are small to
modest in size. The protopod is composed of two
Remipedia Systematics
17
200 ym
B
600 pm
exopod
Fig. 9. Speleonectes ondinae. A) left frontal filament, lateral view, B) left antennule, anterior view, with few aesthetascs of basal pad
drawn; C) left antenna, ventral view, with x as plumose seta of margins.
articles. The proximal segment is much longer than
the distal segment, and the line of articulation be-
tween them lies at an oblique angle. The proximal
segment is equipped with a row of six short setae
along the medial margin near the distal end of the
limb. The distal segment of the protopod has a row
of eight setae on the medial margin. The exopod is
an oval scale extending medially and posteriorly
from the lateral edge of the distal protopodal seg-
ment. The exopod bears along its margins about 50
setae, the bases of which are only slightly more ro-
bust than the distal shafts. The endopod is com-
posed of three subequal segments which arc laterally
from their point of origin on the distal end of the
18
Schram, Yager and Emerson
lacinia_^
mobilis
\1nc1sor
process
Fig. 10. Speleonectes ondmae. A) labrum, ventral surface; B) left mandible dorsal view; C) right mandible anterior view.
second segment of the protopod. Each segment is
equipped with setae along its margins; the first two
of these have about nine such setae along the an-
terior edges of the segments, and the most distal has
about 30 setae. These last are not in one simple row,
rather 16 are arranged in a double row along the
distal lateral margin, whereas the anterior margin
has a row of nine setae and the posterior has a row
of five. All the setae on the antennal segments are
plumose (see Fig. 9C-x).
The labrum (Fig. lOA) is a prominent, rather fleshy
structure. It is narrow and somewhat rounded an-
teriorly, and dilineated by a furrow from the pos-
terior portion that forms the atrium oris. The pos-
terior margin of the labrum is equipped with a dense
array of ribbon-like setae, and the surface just an-
terior to this is decorated with a slight fossa.
The mandibles (Fig. lOB, C) are asymmetrical.
The body of the limbs are very large and occupy the
sides of the cephalon. The working ends of the limbs
insert under the labrum into the atrium oris. The
molar processes are located on pedestals, and are
composed of a broad flat basin covered by dense
rows of spines. The left incisor process has a row of
four large denticles; the right incisor process is formed
by a row of three denticles. Between the molar and
incisor processes are well-developed laciniae mo-
biles; that on the left is sickle-like, that on the right
is composed of a row of three large denticles.
The paragnaths flank the opening to the atrium
oris, and are covered by fine, densely packed setae.
The uniramous maxillules (Fig. 1 1) are very ro-
bust, prehensile, and composed of seven segments.
The four most proximal segments are equipped with
robust endites, and the principle point of flexure for
the limb occurs between the fourth and fifth seg-
ments. The most proximal segment bears an endite
(Fig. 1 1, endite I) that is rather long and narrow,
and terminates in a stout spine located somewhat
anteriorly on the distal end of the endite. Adjacent
to this spine is a double row of six shorter, stout,
spine-like setae located along the apical edge of the
endite. The most posterior of these is subsetulate
(Fig. 13C). The endite of the second segment (Fig.
1 1, endite II) is rather broad and flap-like. It bears
a row of five spine-like setae along the proximal
Remipedia Systematics
19
endites I
Fig. 1 1 . Speleonectes ondmae. Left maxillule, anterior surface, with I-IV providing details of designated endites and limb tip; IVa
detail of left limb illustrated, IVb and cl details of nght limb postenor surface.
margin; a row of four moderate to long, simple setae
along the distal margin; short to moderate simple
setae scattered on the anterior face, especially near
the outer margin; and several additional simple se-
tae in one or more rows near the outer margin of
the posterior face. The lobes of the paragnaths are
inserted between the first two endites of this limb,
and the whole complex flanks the mouth laterally.
The third segment of the limb is rather short and is
developed ventrally as a cone-shaped endite (Fig.
1 1 , endite III). This endite is surmounted at its apex
by two short, very stout, spine-like, subsetulate setae
(Fig. 13C) that are flanked by a few, short, simple
setae. The fourth segment of the limb is relatively
long and bears a large, lobate, subtriangular endite
whose apex is located proximally on the segment
(Fig. 1 1, endite IV). The apex is equipped with five
robust subsetulate setae. These vary in different in-
dividuals from being rather long and slender (Fig.
11, endite IVa) to quite short and stout (Fig. 11,
20
Schram, Yager and Emerson
endites III
A-B
200 ]jm
Fig. 12. Speleonectes ondinae. A) left maxilla, anterior surface, wtih I-IV and c providing details of designated endites and limb tip;
B) left maxillipede, anterior surface.
Remipedia Systematics
21
endite IVb). These apical setae are flanked distally
by a double row of six to ten moderately long, weakly
subsetulate setae. An additional cluster of five of
these setae appears on the posterior face of some
specimens (Fig. 1 1, endite IVb). The fifth segment
of the limb is slightly shorter and narrower than the
fourth, and bears two clusters of at least 12 mod-
erately long, simple setae on the anterior and pos-
terior faces of the disto- ventral margin of the seg-
ment. The sixth segment of the maxillule is very
short. It has anterior and posterior rows of long,
simple setae on the ventral surface approximately
'h of the way along the length of the segment, as well
as matching rows on the lateral surface about % of
the way along the length of the article. The seventh
segment is short, and developed as a single, long,
talon-like claw or fang (Fig. 13B) terminating in a
large pore (Fig. 1 1-cl). There are small clusters of
densely packed, short to moderate, simple setae ar-
ranged around the base of the claw.
The uniramous maxillae (Fig. 12A) are robust,
prehensile limbs composed of seven segments. The
principal point of flexure occurs between the third
and fourth articles of the limb. The first segment is
relatively long, somewhat bent about midway along
its length, and bears three digitiform endites di-
rected towards the mouth. These increase in size as
one proceeds distally in the series. The most prox-
imal endite (Fig. 12A, endite I) has a single, apical,
spine-like seta that is flanked proximally by three
and distally by two short to moderate simple setae.
The middle endite (Fig. 12A, endite II) terminates
in a spine-like seta, which is flanked proximally by
a row of four short, simple setae and distally by
about three moderately long, simple setae. The dis-
tal endite (Fig. 12A, endite III) is surmounted api-
cally by a single spine-like setae that is flanked proxi-
mally by six short, simple setae and distally by about
seven moderate to long simple setae. The second
segment of the limb, lying at an angle to the distal
joint, bears a somewhat conical endite (Fig. 12A,
endite IV) that bears three stout setae on the apex,
the middle one subsetulate. with two groups of mod-
erately long setae arranged distally. The more an-
terior cluster is composed of about five very fine
setae and the more posterior row has about five
robust setae. These latter are subsetulate. The third
segment of the limb is long, with a gently convex
ventral surface bearing two rows of about eight to
12 long simple setae. The fourth segment is some-
what shorter than the third, with the ventral margin
convex distally, where it bears seven or more mod-
erate to long simple setae. The distodorsal margin
is armed with two moderately long, simple setae.
The fifth segment of the maxilla is about '/: the length
of the fourth and bears a cluster of setae of varying
lengths distoventrally, and two simple setae on the
distodorsal margin. The sixth segment has several
small clusters of moderate to long simple setae along
the ventral surface and another cluster on the dis-
todorsal margin. The seventh segment is short and
terminates in a complex claw (Fig. 12A-c). The ter-
minus of the claw is an arcuate or horseshoe-shaped
row of densely spaced spines that is flanked poste-
riorly by a single stout arcuate spine. These are op-
posed by a thumb-like setose pad whose filamentary
elements typically lie within the basin of the arcuate
spine row (Fig. 7C, D).
The uniramous maxillipedes (Fig. 12B) are long,
robust, prehensile limbs, and are composed of eight
segments. The principal point of flexure occurs be-
tween the third and fourth segments. The most prox-
imal segment is short, showing complex folding on
its surface, or what may be the very weak devel-
opment of a ventral lobe. There are several mod-
erate, simple setae along the ventral surface. The
second segment of the limb has a small, rounded,
distinctly pad-like endite with at least five short to
moderate simple setae on the posterior surface and
about four long simple setae on the anterior surface.
The third segment is long, and the ventral surface
has about 23 to 24 moderate to long, simple setae
arranged in two rows of about 11 to 13 setae each.
These setae are arranged along an arcuate convex
surface that forms a sort of very weak endite. The
fourth maxillipedal segment is long, but somewhat
shorter than the third. Its distoventral surface is
slightly inflated, with about 17 moderate to long
simple setae in two rows. The fifth through seventh
segments of the limb are progressively shorter as
one proceeds distally in the series, and each segment
has rows of moderate to long simple setae arranged
along the distoventral edges of the articles. The eighth
segment of the limb is equipped with a distinctive
claw identical to that seen on the terminus of the
maxillae.
The trunk is composed of from 1 9 to 25 homono-
mous segments (Fig. 8A), each bearing a pair of
biramous, paddle-like limbs. Most of the limbs bear
oval segments on the rami (Fig. 8C) and are all
similar to each other, except in the first pair the
rami are rather slender (Fig. 8B) and in the posterior
limbs the segments are small and have fewer setae
(Fig. 8D). All the trunk limbs present basically the
same arrangements and kinds of setae. The most
prominent and common are the plumose setae along
22
Schram, Yager and Emerson
Fig. 13. Speleonecles ondmae. A) first endite of maxillule showing subsetulate setae; B) maxillule limb tip showing talon-hke claw
with terminal pore, limb tightly flexed with tip opposed to basal endites; C) subsetulate apical seta of third endite of maxillule; D)
comb seta of second trunk limb.
Remipedia Systematics
23
the margins of the segments (Fig. 8C-y). A second
setal type has a comb-hke form (Fig. 8B-x), in which
a tall, tapering shaft has pointed processes arranged
along it margins. The bases of these comb setae are
marked with a fan or crest of densely arrayed spines
(Fig. 1 3D). This distinctive setal type is found at the
distal and outer comers of the intermediate seg-
ments of the rami.
Remarks.— In the original description of this
species Garcia- Valdecasas (1984) placed this taxon
in its own genus, Morlockia, and in a separate mono-
typic family. However, our analysis reveals this
species to be a close relative of Speleonectes lucay-
ensis. Both taxa share several derived features evi-
dent in the diagnosis of Speleonectes provided above.
The most notable of these is the distinctive horse-
shoe shaped comb on the claws of the maxillae and
maxillipedes. Knowledge of these claws in other gen-
era of nectiopodans, to be described below, shows
that these structures are especially diagnostic. The
sharing of such a derived feature probably indicates
the common ancestry of S. hicayensis and 5'. on-
dinae. Separate generic and familial placement is
therefore not justified for these two species.
Specimens examined in the present study exhibit
considerable variation, not only in segment number
but also body size (Table 2), more so than that in
other known species of nectiopodans (see e.g.. Ta-
bles 1 or 3). Most adult nectiopodans vary in seg-
ment number by only one or two, with body sizes
varying in a similar manner. In 5. ondinae. the ratio
of head length to total body length is relatively large,
about 1:7, while a more typical ratio is that seen for
5". hicayensis, about 1:12. The larger ratio is actually
more akin to that noted in juveniles of several nec-
tiopodan species currently being studied by us. It
may be of importance that the subsetulation char-
acteristic of setae on mouthparts of S. ondinae is
also seen on mouthparts of juveniles that appear to
belong to S. hicayensis. Finally, the last limbs in the
trunk series are especially small and lacking in se-
tation, again more like that seen in juvenile nectio-
podans than in adults (compare e.g., Fig. 8D to
ID).
Taken together, these observations suggest that
specimens of 5". ondinae are possibly immature in-
dividuals. However, the specimens appear to be be-
yond a juvenile stage: they have well-developed trunk
pleurites and segmental digestive diverticula (fea-
tures that are generally absent from juvenile forms).
Therefore, it would not be surprising if future col-
lections of the Canary Island nectiopodans pro-
duce larger animals of around 30 trunk segments.
with relatively small head to body length ratios.
However, because of the strong suspicion on our
part that the known specimens of S. ondinae are
subadults, we have chosen at this time not to include
the head/body ratio and the low trunk segment num-
ber in the diagnosis of this species. It is conceivable,
however, that 5'. ondinae may be a paedomorphic
derivative exhibiting a "juvenilized" head/body ra-
tio and subsetulate setae as a result of evolution from
some form more akin to S. hicayensis.
Genus LASIONECTES Yager and Schram, 1986
Lasionectes Yager and Schram, 1986:65.
Diagnosis. — Ma\\\\aQ and maxillipedes subche-
late, with segments three and those distal having
rows of fine hair-like setae along medial edges, en-
dites of second segments with central basin flanked
by arrays of setae and pores, termini with distinctive
trifid claw opposed to thumb-like setal pad.
Type species. —Lasionectes entrichoma Yager and
Schram, 1986.
LASIONECTES ENTRICHOMA Yager and
Schram, 1986
Lasionectes entrichoma Yager and Schram, 1986:
65.
Diagnosis.— SmcQ there is only a single species
currently recognized, the diagnosis is the same as
that of the genus.
//o/o/vpe.-USNM 216978, coll. April 6, 1983.
Type locahty. —Old Blue Hill Cave (tannic pool),
Providenciales Island, Turks and Caicos, British
West Indies.
.Additional material.— Type locality. Yager Pri-
vate Collection: 2 individuals, coll. Dec. 1982; 1
individual, coll. Oct. 29, 1982; 2 individuals, coll.
Oct. 30, 1982. SDSNH Crustacean Collection: 2191,
7 individuals, coll. April 6, 1983; 2196, 2 individ-
uals, coll. April 7, 1983; 2195, 4 individuals, coll.
Oct. 1983; 2002, 1 sectioned individual, coll. April
6, 1983; 2003-2008, 6 sectioned individuals, coll.
April 7, 1983; 2217, dissected and parts mounted
for SEM.
Old Blue Hill cave (clear water pool), Providen-
ciales, Turks and Caicos Islands. SDSNH Crusta-
cean Collection: 2192, 4 individuals, coll. April 6,
1983; 2194, 6 individuals, coll. Oct. 17, 1983; 2009-
2011, 3 sectioned individuals, coll. April 6, 1983;
2012-2013, 2 sectioned individuals, coll. April 7,
1983; 2014, 1 sectioned individual, coll. Oct. 17,
1983; 2216, whole mounted for SEM.
24
Schram, Yager and Emerson
Fig. 14. Lasionectes entrichoma. A) dorsal surface of body; B) posterior view of first trunk limb; C) tenth trunk limb, with x and
y as variant setae found along trunk limb margins; D) twenty-ninth trunk limb; E) anal segment with caudal rami.
Cottage Pond, North Caicos, Turks and Caicos
Islands. SDSNH Crustacean Collections: 2197, 3
individuals, coll. Oct. 20, 1983; 2198, 2 individuals,
Oct. 22, 1983.
Description. —The cephalon is about '/,, the total
length of the body (Fig. 14 A). The cephalic shield
is slightly narrower anteriorly than posteriorly and,
at the point of narrowing, bears a faint transverse
Remipedia Systematics
25
A-C
I 1
200 ijm
dorsal
Fig. 15. Lasionectes entnchoma. A) left frontal filament, posterior view; B) left antennule, anterior view; C) left antenna, ventral
view, with x as plumose seta found along margins.
groove that does not quite meet in the midhne. There
is an additional transverse groove on the shield about
halfway along its length. The anterior margin of the
shield folds ventrad over the front of the cephalon.
The adult trunk has a maximum of 32 segments.
The tergite of the first trunk segment is narrower
and shorter than those that immediately follow, and
is frequently covered in whole or in part by the
posterior margin of the head shield. The trunk seg-
ments of the adult are produced laterally as prom-
26
Schram, Yager and Emerson
1 acini a
mobil is
inci sor
process
molar process
600 jjm
B-C
400 jjm
Fig. 16. Lasionectes entrichoma. A) labrum, ventral surface; B) left mandible dorsal view with enlargment; C) right mandible dorso-
postenor view with enlargement.
inent pleura, and are rounded on their anterior and
posterior comers. The most posterior trunk seg-
ments are greatly reduced (Fig. 14E). The stemites
of the trunk segments bear distinct transverse bars
along their posterior aspect (Fig. 27A). The bar of
the fourteenth segment is developed at its lateral
extent as triangular flaps that shield the gonopores
located on the bases of the protopods of the four-
teenth trunk limbs. The sternal bars from segments
24 posteriad are concave. The anal segment is about
as wide as it is long, and the terminal anus is pro-
tected by a small anal flap (Fig. 27D). The caudal
rami are slightly shorter than the length of the anal
segment, and bear a cluster of short to moderate
setae on their termini and 2 moderate setae along
the medial surfaces (Fig. 14E). Measurements of a
representative series of specimens are provided in
Table 3.
A small pair of frontal filaments or processes are
located on the anterior part of the ventral cephalon.
Remipedia Systematics
27
endites I
Fig. 17. Lasionectes entnchoma. Left maxillule, anterior surface, with I-II and c providing details of designated endites and limb
tip.
near the bases of the antennules (Fig. 19A). These
rod-like structures appear to have the cuticle of the
basal portion somewhat less sclerotized than that of
the distal portion (Fig. 19B). The thinner distal part
of the filament is tapered, and a small spine-like
process arises at the point of transition from the
basal to distal portions of the filament (Fig. 15A).
The biramous antennules (Fig. 15B) are well de-
veloped and of the typical speleonectid form. The
peduncle is composed apparently of two segments,
though the suture marking the articulation is weakly
developed. The most proximal bears a pad which
has three to four rows of densely packed aesthetascs
(Fig. 1 9C) draped back over the antennae (Fig. 20A).
The distal segment is bifurcate at its terminus. The
long dorsal ramus is composed of 12 segments; and
the ventral ramus, '/2 to -A the length of the dorsal,
is composed of eight segments. Except for the prox-
imal two articles of the dorsal ramus, the elements
are long and slender, and are equipped with fine
setae arranged in rows along their ventral margins
in tufts distoventrally, and scattered distodorsally.
The terminal segments of each ramus bear distal
tufts of four to six hair-like simple setae.
The biramous antennae (Fig. 15C) are well de-
veloped but modest in size. They do not extend
beyond the margin of the cephalic shield. The prox-
imal segment of the protopod is somewhat longer
than the distal unit, and is wider at its base than at
its terminus. It bears two setae along its medial mar-
gin. The distal segment of the protopod is equipped
with about 1 2 setae medially, and laterally bears the
28
Schram, Yager and Emerson
endites I
II
IV
III
V
Fig. 18. Lasionectes entrkhoma. A) left maxilla, anterior surface, with c providing anterior and posterior details of limb tip; B) left
maxillipede, anterior view.
Remipedia Systematics
29
oval exopod. The exopod is a scale-like structure
with about 35 to to 40 long setae arranged around
its margins. The three-segmented endopod arcs lat-
erally from the distal end of the protopod. The first
segment bears about 1 2 or 1 3 setae along its anterior
margin; the second is equipped with about 1 1 or 12
setae along its anterior edge; the third segment has
some 24 setae arranged along its margins. With re-
gard to the latter, the setae along the proximal an-
terior and the posterior margins are in single rows,
and those along the distal anterior and distal mar-
gins are in a double row (Fig. 20B). The anterior
surface of the third endopodal segment is equipped
with an array of large pores (Fig. 20C). All the mar-
ginal setae of the antennae are of the plumose type
(Fig. 1 5C-X), distinctly enlarged at their bases (Fig.
20D).
The labrum (Fig. 16A) is a large fleshy lobe. An-
teriorly it narrows to a point, and posteriorly is
marked by a furrow where it folds back to form the
atrium oris. This bulbous posterior portion is marked
with a fossa on its margin which bears a dense array
of ribbon setae (Fig. 21 A).
The mandibles (Fig. 16B, C) are asymmetrical.
They take origin on the side of the cephalon (Fig.
19D), extending ventrally to insert distally under
the posterior lobe of the labrum and into the atrium
oris (Fig. 2 IB). The molar processes (Fig. 22A, B)
are located on pedestals. They are composed of
broad, flat basins with a complex array of spines.
Along the edges are located long, thin, densely packed
spines (Fig. 22C) that mark the edge of the basin.
Within the basin the spines are arranged in rows
(Figs. 23A) and are of two types: flanking the axes
of the basins are densely packed short spines, and
along the axes of the basins are low round tubercles
(Fig. 22D). Near the lateral extent of the central axes
the tubercles are mixed with four low cones with
apical pores (Fig. 23A, B). (That these pores produce
some kind of secretion is indicated by the fact that
the spines in the basin of the molar process can
sometimes be clogged with an amorphous sub-
stance, see e.g.. Fig. 2 ID). The right incisor process
is composed of a row of three large denticles (Figs.
16C, 22A); the left incisor process is composed of
four large denticles with a smaller tooth between the
two posterior major teeth (Figs. 16B, 22B). Prom-
inent laciniae mobiles are found between the incisor
and molar processes: the right one is formed by three
large denticles, the left is concave and sickle-like.
The paragnaths flank the atrium oris (Fig. 2 IB).
Their margins are covered by densely packed ribbon
Table 3. Representative measurements in mm of specimens of
Lasionectes entrichoma. (Not all dimensions could be measured
on all specimens.)
Feature
Range
n
X
s
V
Body length
11.8-31.5
47
20.4
4.7
+
0.7
23.0
Head length
1.4-3.3
50
2.4
0.5
+
0.1
20.8
Head width
1.1-2.6
50
2.0
0.4
+
.05
20.0
Trunk segs.
26-32
50
30
1.5
+
0.2
5.0
Tl length
0.2-0.6
47
0.4
0.1
+
.02
25.0
Tl width
0.8-1.7
50
1.4
0.2
+
.03
14.3
T2 length
0.4-0.8
50
0.6
0.1
±
.02
16.7
T2 width
1.1-2.7
50
2.1
0.4
+
.06
19.0
T14 length
0.5-1.0
50
0.8
0.1
±
.02
12.5
T14 width
1.3-3.2
50
2.4
0.4
+
.06
16.7
Anal seg. length
0.3-0.7
48
0.5
O.I
+
.02
20.0
Anal seg. width
0.3-0.6
48
0.5
0.1
4-
.01
20.0
Caudal ramus
length
0.2-0.5
48
0.4
0.1
+
.01
25.0
Caudal ramus
width
.06-0.1
48
0.1
.01
+
.001
10.0
setae (Fig. 21C), and they insert into the space be-
tween the two basal-most endites of the maxillules.
The uniramous maxillules (Fig. 1 7) are robust and
prehensile. They are composed of seven segments,
of which the three most basal are equipped with
well-developed endites. The principal point of flex-
ure occurs between segments four and five. The first
segment bears a large endite (Figs. 1 7, endite I; 23C)
that terminates in a long stout spine flanked postero-
proximally by a row of six stout spine-like setae.
The endite of the second segment is broad and plate-
like (Figs. 17, endite II, 23C). It has six short, stout
setae along its posterior margin, paralleled by an
irregular row of many tiny setae distally. In turn,
this array is flanked along the anterior margin by
eight moderate to long simple setae. The third seg-
ment of the limb is developed into a cone-like endite
(Fig. 17, endite III) that is surmounted apically by
two robust, spine-like setae and one or two small,
simple setae. The fourth segment of the limb is rath-
er long, with a subtriangular endite whose apex is
near the proximal end of the limb (Fig. 17, endite
IV). The endite is double crested and bears a row
of moderate to long, simple setae along each crest.
At the apex is a short, stout, spine-like seta which
interdigitates with the two apical setae on endite III
when the limb is flexed. The fifth segment is as long
as the third, but is not equipped with any endites.
It does bear two clusters of eight to ten simple setae
on the antero- and postero-distal margins of the
segment. The sixth maxillulary segment is short and
bears two clusters of about 1 2 moderately long, sim-
ple setae distally on the antero- and postero- ventral
30
Schram, Yager and Emerson
Fig. 19. Lasionecles entnchoma. A) view of anterior body, ff— frontal filaments, al — antennule, mxl — maxillule, mx2 — maxilla; B)
posterior views of frontal filaments, note thinner cuticle of filament base and spine (s) allowing cuticle to shrivel and distort; C) antero-
oblique view of aesthetasc pad of antennule; D) lateral view of cephalon, al —antennule. 1 — labrum, mn — mandible, mxl —maxillule,
mx2 — maxilla, mxpd — maxillipede, Tl— first trunk segment, tl — first trunk limb, hs — head shield.
Remipedia Systematics
31
Fig. 20. Lasionectes entnchoma. A) ventral view of anterior part of cephalon showing relationship of antennule and antenna beneath
it, aes— aesthetascs. al —antennule, a2 — antenna; B) on end view of distal margin of third segment of antennal endopod showing
double row of plumose setae; C) ventral surface of third segment of antennal endopod showing surface pores; D) detail of basal aspect
of antennal plumose setae.
32
Schram, Yager and Emerson
Fig. 21. Lasionectes enlrichoma. A, B) mouth region, 1 — labrum, mn — mandible, enl —first maxillular> endite, en2 — second max-
illulary endite, mxl— distal portion of maxillule, pg— paragnaths; C) detail of paragnaths showing nbbon setae; D) surface view of
right molar process, note secretory material clogging spines on lower aspect of process.
Remipedia Systematics
33
Fig. 22. Lasionectes entnchoma. A) right mandible; B) left mandible; C) lateral oblique view of left mandible molar process showing
differences between spines on edge and those of basin; D) detail of central axis of left molar process basin.
34
Schram, Yager and Emerson
Fig. 23. Lasionecles enlnchoma. A) surface view of dorsal portion of molar process of left mandible; B) detail of A showmg cones
with pores; C) first and second endites of maxillule with talon-like tip of limb projecting down from above; D) tip of maxillule with
terminal pore.
Remipedia Systematics
35
Fig. 24. LuiioncLici entnchoma. A) lateral view of maxilla base showing opening (p) of maxillary pore; B) lateral view of tightly
flexed maxilla showing how tip becomes opposed to basal pads; C) oblique view of maxilla endite IV showing setae flanking porous
central trough; D) detail of some pores on maxillary endite IV.
36
Schram, Yager and Emerson
Fig. 25. Lasionectes entrichoma. A) antero-lateral view of digitiform endites at base of maxilla; B) medial view of endites m A; C)
postenor aspect of tip of maxilla; D) anterior aspect of tip of maxilla (see text for discussion).
Remipedia Systematics
37
Fig. 26. Lasionectes entrichoma. A) anterior aspect of tip of maxillipede showing location of pores on claw; B) ventral view of weak
basal endite of maxillipede; C) oblique view of second pad-like endite of maxillipede showing rows of simple setae flanking central
porous trough; D) detail of setae in C.
38
Schram, Yager and Emerson
Fig. 27. Lasionecles enlnchoma. A) ventral surface of antenor portion of trunk; m.\pd — maxillipede, tl— first trunk limb, t2 —
second trunk limb, t3 — third trunk limb, sb — stemite bar; B) gonopore region on fourteenth trunk somite, pr— protopod of fourteenth
limb, gp— gonopore, gf— genital flap on the lateral most aspect of the stemite bar; C) comb setae seen on trunk limbs; D) ventro-
posterior aspect of postenor end of body, t32 — thirty-second trunk limb, as — anal segment, af— anal flap, cr— caudal rami.
Remipedia Systematics
39
margins and two clusters of six short, simple setae
distally on the antero-and postero-lateral margins.
The seventh segment of the limb is short and ter-
minates in a long, gently arcing, talon-like claw. This
bears a large pore at its apex (Fig. 23D). Rows of
seven to ten simple setae flank the bases of the claw
on the anterior and posterior surfaces of the seg-
ment.
The uniramous maxillae (Fig. 18A) are robust,
subchelate limbs. They bear a prominent maxillary
gland pore on the posterior surface of the limb base
(Fig. 24 A). They are composed of seven segments,
and the principal point of flexure occurs between
the third and fourth segments. The most proximal
segment bears a series of three digitiform endites
(Figs. 18, endites I-III, 25A, B) that increase in size
distally. The second and third endites have clusters
of four to five short simple setae on their anterior
surfaces (Fig. 25A). The first endite has a short,
spine-like seta at the apex, a cluster of up to twelve
short, simple setae proximal to this, and a long,
simple seta on the lateral margin with some short
simple setae clustered around its base. The second
endite has a moderately long, spine-like seta at the
apex, up to a dozen simple setae along the proximal
margin of the endite, and a long, simple seta on the
lateral margin. The third endite has a large spine-
like seta at the apex, a dozen or more short, simple
setae along the proximal margin, and three long,
simple setae along the lateral margin. The second
segment of the limb bears a prominent pad-like en-
dite (Fig. 1 8, endite IV; 24B, C). This bears clusters
of short setae in two rows along a central basin well
equipped with secretory pores (Fig. 24C). When the
limb is tightly flexed the terminal claw rests in or
close to the basin of this endite. The third segment
of the limb is very long, and has an arcuate endite
with two rows of densely packed, simple setae along
two crests. Segments four through six of the maxillae
are narrow and progressively shorter distally. Their
ventral margins are decorated with a densely packed
row of short, hair-like setae. Segment five has one
or two simple setae at the disto-dorsal margin of the
rim, and segment six has two clusters of about four
simple setae, each located distally on the antero-
and postero-dorsal surfaces of the segment. The sev-
enth segment of the limb is rather short and armed
with a distinctive claw (Figs. 18A-C, 25C, D). This
is basically a trifid structure of three denticles, the
central one being the longest. Between the central
and anterior denticles is a comb-like row of about
five or six short, delicate spines. A large pore is
located on the dorsal surface of the base of the cen-
tral tooth and another on the side of the central tooth
beneath the comb row (Fig. 26A). Opposed to this
complex is a thumb-like pad bearing long, simple
setae.
The uniramous maxillipedes (Fig. 18B) are sim-
ilar to the maxillae, but are markedly longer. They
are composed of eight segments, with the subchelate
flexure occurring between the third and fourth seg-
ments. The first segment is relatively long and has
a weakly developed lobe on its ventral surface (Fig.
26B) that bears some simple setae and pores. The
second segment of the limb bears a pad-like process
similar in many respects to endite IV of the maxillae
in that it bears two rows of setae along a central
basm equipped with numerous pores (Fig. 26C).
These setae are actually terraced (Fig. 26D). Both
these endites are opposed by the terminal claw of
the maxillipede when the limb is tightly flexed. The
long, third segment is similar to that of the maxillae.
Beyond the flexure, however, there are five segments
on the maxillipede. The first four are similar to the
first three on the maxillae. The eighth maxillipede
segment is almost identical to the seventh on the
maxillae, including the complex trifid claw.
The trunk limbs are all biramous paddles. The
first pair are somewhat more slender (Fig. 14B) and
are located slightly more dorsally on the segment
than any of the following trunk limbs (Figs. 19D,
27A). The more posterior trunk limbs have rami
with subrectangular intermediate segments and oval
terminal ones (Fig. 14C). The posterior trunk limbs
are much like those anterior to them except that
they are smaller and bear few setae (Fig. 14D). The
arrangement of setal types around the margins of
the limbs are similar for all limbs, though the exact
number on each limb (and even each member of a
pair) varies. The most common are plumose setae
(Fig. 14C-X) occupying most of the margins. Next
are the comb-like setae found on the distal comers
of the intermediate segments. These have a long,
thin shaft with small, sharp, curved denticles along
the margins of the shaft (Figs. 14C-y, 27C), and a
fan-like comb of densely packed spines at the base
(Fig. 27C). As mentioned above, it is assumed these
setae are used in combing out or carding the setules
of the plumose setae.
Remarks.— The description and iflustrations of
this species presented here are considerably more
detailed than for those of any other nectiopodan
because the available material is so abundant. In-
deed, though species of the genus Speleonectes were
40
Schram, Yager and Emerson
Fig. 28. Godzillius robustus. A) dorsal surface of body; B) posterior view of first trunk limb; C) fourteenth trunk limb, with x and y
as variant setae from margins, and genital flap with pore at base; D) twenty-nmth trunk limb; E) ventral view of anal segment with
caudal rami.
Remipedia Systematics
41
the first to be discovered, because those species are
so rare, L. entrichoma will undoubtedly become
the standard morphological type of reference for the
order.
One interesting fact noted in the course of SEM
study of this material is the porous nature of the
cuticle. Pores are found everywhere: the cephalic
shield (Fig. 19A). body segments, and the surfaces
of endites and limbs (Fig. 24D). In addition, the
cuticle surface is often equipped with fine sensillia;
these are especially common on the surfaces of the
anal segment and caudal rami. These latter are prob-
ably related to mechanoreception, but the deter-
mination of whether the pores are chemo- or mecha-
noreceptors, or secretory must await TEM studies
of these structures and their underlying cuticle.
Family GODZILLIIDAE nov.
Diagnosis. —Cephalic shield subtrapezoidal, wid-
er posteriorly than anteriorly; frontal filaments with
several "joints"; ventral ramus of antennules with
few segments, terminal segment very long and blade-
like; antennae with multiple rows of plumose setae
on all segments of endopod; mandibles only slightly
asymmetrical; maxillule endite III weakly devel-
oped, endite IV club-like; maxillae and maxillipedes
subchelate. subtriangular endites on third segments
massive and densely setose, with segments distal to
elbow relatively thin and delicate, terminal claws
seven-pronged; maxillae with three segments be-
yond elbow; maxillipede with four segments beyond
elbow; trunk tergites laterally pointed; protopod of
fourteenth trunk limb with flap protecting genital
pore; trunk stemites developed as plates.
Remarks. — Besides the large adult size of these
nectiopodans (at least twice that of any other known
species in the order), the morphology, especially of
the cephalic limbs, is so distinctive as to warrant
separate familial status.
Genus GODZILLIUS nov.
Diagnosis. —Smce only one genus is currently rec-
ognized, the diagnosis is the same as that of the
family.
Etymolog\'.—A reference to the almost mon-
strously large size of these animals as adults, the
extreme styliform talon on the maxillule, and the
grappling-like claws on the maxillae and maxil-
lipedes.
Type species. —Godzillius robustus nov.
GODZILLIUS ROBUSTUS nov.
Diagnosis.— Smct only one species is currently
recognized, the diagnosis is the same as that of the
family and genus.
Etymology.— A reference to the large size of this
species.
//o/on'pe.-USNM 216980, coll. Oct. 22, 1983.
Type locality. —Cottage Pond, North Caicos,
Turks and Caicos Islands, British West Indies.
Additional material.-SDSNH 2215, coll. Oct. 22,
1983 from the type locality.
Description —The cephalon is about % the total
length of the body (Fig. 28A). The cephalic shield
is subtrapezoidal, the widest portion is posterior,
the narrowest part in the middle, and the anterior
part wider than the middle but narrower than the
posterior. The adult is composed of about 29 trunk
segments. The trunk tergites are very prominent and
somewhat pointed postero-laterally. The first trunk
segment is shorter than those which immediately
follow, but is not especially narrower, and is ap-
parently not covered to any degree by the posterior
margin of the head shield. The stemites of the trunk
segments are developed as plates. The protopod of
the fourteenth trunk limb bears a triangular flap on
the ventral margin near the base of the limb which
serves to protect the opening of the genital pore (Fig.
28C). The anal segment is markedly wider than long
(Fig. 28E). The caudal rami are shorter than the anal
segment, situated and directed ventro-posteriorly
on the distal end of the segment, and bear terminal
clusters of setae. Short, fine setae are scattered over
much of the cuticle, and these frequently issue from
papilla-like structures embedded in the semi-trans-
parent epicuticle. Measurements of the specimens
at hand are provided in Table 4.
There is a relatively prominent set of frontal fil-
aments (Fig. 29A) on the anterior portion of the
ventral cephalon near the base of the antennules.
The main shaft is rather long, and appears to be
divided into three subequal "articles" by two joints
or points of flexion. The distal "article" bears a
small spine about '/) its length from its base.
The biramous antennules (Fig. 28B) are well de-
veloped. The peduncle is composed of two seg-
ments. The proximal one is relatively long, and ven-
trally bears the characteristic nectiopodan pad with
several rows of long aesthetascs. The distal segment
of the peduncle is relatively short and deeply bifur-
cate at its tip. The dorsal ramus is very long; the
three basal segments are of modest length; the next
seven segments are very long and narrow; the elev-
42
Schram, Yager and Emerson
Fig. 29. GodziUius robustus. A) left frontal filament, lateral view; B) left antennule, anterior view, C) left antenna, ventral view, with
X as plumose seta of the margins.
Remipedia Systematics
43
lacinia
mobilis
5
500)jm
B
600 )jm
C
200 pm
Fig. 30. Godzillius robustus. A) labrum, ventral surface; B) left mandible dorso-postenor view with enlargement; C) detail of right
mandible.
enth and terminal segment is very short. The basal-
most segment tends to have its rows of short hair-
like setae closer to the distal ends. The intermediate
segments have rows of short, hair-like setae all along
their medial margins. The terminal segment is se-
tose on all its margins. The lateral margins of most
segments can have tiny hair-like setae near their
distal ends. The ventral ramus of the limb is quite
short and apparently composed of only three seg-
ments. What appear to be the two most proximal
segments are short and do not seem to bear any
setae. Most of the length of the ramus is made up
by the distal-most third segment, which bears a row
of fine hair-like setae along its undulate, lateral mar-
gin and its terminus.
The biramous antennae (Fig. 29C) are noteworthy
for their extremely setose margins. The limb is of
modest size with a two-segmented peduncle. The
peduncular segments are subequal: the proximal
segment has only three setae located on its distal
medial aspect; the distal segment has about 1 7 setae
along its medial margin with an extra seta set slightly
44
Schram, Yager and Emerson
Fig. 31. Godzillius robustus. Left maxillule, anterior surface, with a-c as details of subsetulate seta, papilla, and limb tip respectively.
dorsal at the distal end. The oval exopod is some-
what narrower posteriorly than anteriorly, and bears
a single row of 60 to 70 setae along its margins. The
articulation between the exopod and the distal pe-
duncular segment is not well developed. The three
endopodal segments arc laterally, and all bear mul-
tiple rows of setae along their anterior margins, and,
where they occur, only a single row along the pos-
terior margins. The first or most proximal segment
has a total of 33 setae in three unequal rows along
the margin, and what appears to be four additional
setae near the proximal end. The intermediate seg-
ment has close to 35 setae along its anterior margin.
Twenty of these are arranged primarily in three un-
equal rows, and the remaining setae are clustered in
a dense array at the distal end of the segment. This
intermediate segment also has an additional row of
five or six setae located distally on the posterior
margin. The third or most distal segment has close
to 55 setae in three unequal rows along its anterior
margin, with what appear to be three additional
setae near the proximal end. In addition, the distal
and posterior margins of the segment have a single
row of about 1 7 setae. All these marginal setae on
the antennae are very long and plumose in form
(Fig. 29C-V).
The labrum (Fig. 30A) is a large, lobate structure.
The anterior portion is subtriangular, with the apex
pointed anteriorly. This is separated from the pos-
terior portion by a deep furrow, which acts to pinch
off the anterior portion of the labrum from the pos-
terior. Ridges on both the anterior and posterior
portions flank the furrow. The posterior free margin
of the labrum is marked by a large, broad fossa
which bears a dense array of setae.
The mandibles (Fig. 30B, C) are only slightly
Remipedia Systematics
45
J_L
5
Fig. 32. Godzillius rohustus. A) left maxilla, anterior surface; B) left maxillipede, with c as detail of limb tip.
46
Schram, Yager and Emerson
Fig. 33. Godzillius robuslus. A-C) tip of right mandible; A) dorsal view; B) anterior view; C) lateral-most portion of molar process,
note spike-like spines along margin and shorter spines of basin with basal accessory spinose lobes; D) comb seta of second trunk limb.
Remipedia Systematics
47
Fig. 34. GodziUius robiistus. Right maxillipede claw; A) disto-oblique view; B) ventral view; C) proximo-oblique view; D) closeup
of fleshy setose pad of C.
48
Schram, Yager and Emerson
Table 4. Representative measurements in mm of the two avail-
able specimens oi Godzttlius robuslus. Not all measurements could
be taken on SDSNH 2215, since the specimen was dissected
before detailed laboratory study could be undertaken.
USNM
SDSNH
Feature
216980
2215
Body length
43.2
—
Head length
4.9
—
Head width
3.6
3.7
Trunk segs.
29
Tl length
0.6
0.5
Tl width
3.7
3.6
T2 length
0.8
0.7
T2 width
4.0
—
T14 length
1.7
1.5
T14 width
4.2
—
Anal seg. length
0.7
1.2
Anal seg. width
1.0
1.1
Caudal ramus length
0.5
0.5
Caudal ramus width
0.1
0.2
asymmetrical. The left incisor process is composed
of a row of three large denticles that are developed
with serrated crests along their anterior edges. The
most anterior tooth has a small accessory denticle
near its base on the anterior surface. The right in-
cisor process (Fig. 33A) has three denticles (one bro-
ken off on the specimen SDSNH 2215), but the
median tooth is serrated along both its edges. The
left lacinia mobilis is composed of six denticles. The
right lacinia is formed by three denticles with broad-
ly serrate surfaces (Fig. 33A, B). The molar processes
are situated on pedestals, and have broad flat basins
covered with dense rows of spines. Those along the
edges are spike-like; those in the basins are smaller
but these bear spinose lobes near their individual
bases (Fig. 33C). The surfaces of the molar processes
are somewhat T-shaped, with the top of the T par-
alleling the laciniae mobiles.
The paragnaths flank the opening to the atrium
oris and are covered by dense arrays of setae.
The uniramous maxillules (Fig. 31) are robust
prehensile limbs. They are composed of seven seg-
ments, with the principal point of flexure between
the fourth and fifth segments. Segment one bears a
large endite (Fig. 3 1 , endite I) surmounted at its apex
by a robust spine flanked by a cluster of eight highly
sclerotized, tooth-like setae arranged in a row. The
teeth of these endites on either side of the animal
are opposed to each other at the opening to the
atrium oris. The endite of the second segment is a
broad, thin, lobate structure (Fig. 31, endite II). Its
apical margin is marked with about 12 moderate to
long, relatively robust simple setae. The third seg-
ment of the maxillule essentially lacks an endite.
though its ventral surface is broadly rounded and
bears one short, simple seta (Fig. 3 1 , endite III). The
fourth segment of the limb is relatively long and
bears a large, club-like process as an endite near the
proximal end of the segment (Fig. 31, endite IV).
This is marked on its distal surface by six or so
rounded, tooth-like papillae interspersed with mod-
erate to long, simple setae. These papillae appear to
have a duct through the cuticle connecting their tips
with underlying tissue (Fig. 3 1 -b). At the base of the
club is a small cluster of five long, subsetulate setae
(Fig. 31 -a). The fifth segment of the limb is long and
bears a diagonal row of moderate to long, simple
setae and small papillae that extend across the ven-
tral anterior surface of the segment. Near the prox-
imal end of the antero- ventral surface is a cluster of
seven small, simple setae. The sixth segment is very
short and has a row of about 19 moderate to long
simple setae clustered on the ventral margin, and a
row of about four short simple setae anterior to that.
Near the dorsal margin is a row of seven long, simple
setae on the anterior surface, and in a similar spot
on the posterior surface is a pair of simple setae.
The seventh segment of the limb is a long, styliform,
talon-like claw surmounted by a large pore. At the
base of the claw on the medial surface of the segment
is a cluster of about 13 long, simple setae. Light
microscopy reveals a large, membrane-lined duct
leading from the pore to a granular mass of tissue
and the presence of many structural grooves within
the talon, the outer surface of which is abraded (Fig.
31-c).
The uniramous maxillae (Fig. 32A) are subchelate
limbs composed of six segments, the principle point
of flexure being between the third and fourth seg-
ments. The proximal three segments are very robust;
the distal three segments are long, thin, and delicate.
A prominent groove appears on the anterior surface
of the fourth and fifth segments. The most proximal
segment of the limb bears three digitiform endites
(Fig. 32A, endites I-III); the smallest is most prox-
imal; the largest most distal. Each endite is sur-
mounted with a short, rounded, tooth-like spine.
These are flanked by two to seven short, spine-like
setae along the crests of the apical margins. Each
endite also bears one or two large, simple setae with
disc-like bases located along the antero-distal mar-
gins of the endites. The second segment of the max-
illa is developed as a simple, tall, cone-like endite
with two small, simple setae near the apex (Fig. 32A,
endite IV). When the limb is tightly flexed, this cone
appears to fit into a groove along the postero-distal
margin of the third of the digitiform endites. The
Remipedia Systematics
49
third segment of the limb is extremely wide, espe-
cially at its proximal end. The ventral surface is
developed as a long, double-crested endite with dense
rows of moderate to long, simple setae along its
crests. Internally, this segment accommodates a well-
developed musculature to flex the distal segments
of the limb. The fourth segment of the limb is almost
as long as the third, but is a long, thin, narrow ele-
ment that lies in the valley between the two crests
of the third segment. The ventral surface is covered
with a dense row of small, appressed, simple setae,
and the dorsal surface bears two short setae at the
distal margin. The fifth segment of the limb is rel-
atively short and bears setae similar to the fourth,
with additional clusters of short to moderate, simple
setae near the distal margin on the posterior surface
and flanking the appressed ventral setae. The sixth
segment is very short and is developed as a distinc-
tive ten pronged, grappling hook-like claw. The ten
denticles are arranged in an arc, directed ventrally,
and are opposed by a fleshy pad bearing an array of
setae.
The uniramous maxillipedes (Fig. 32B) are very
similar to the maxillae in form, but are composed
of seven segments. The limb is subchelate, with its
principal point of flexure between the third and
fourth segments. The three basal segments are very
robust, the four distal segments are thin and delicate.
The first segment of the limb bears a weakly de-
veloped endite with four or five short to moderate
simple setae. The short second segment of the limb
bears no endites. The third segment of the limb is
very long and wide, and has its ventral surface de-
veloped as a double crested endite bearing rows of
moderate to long simple setae. As in the maxilla,
this segment accommodates a very robust muscu-
lature to flex the distal segments of the limb, and
bears an intermittent groove on the dorsal and an-
terior surfaces. The fourth through sixth segments
of the limbs are thin and delicate and appear to act
as a unit in opposition to the endite on the third
segment. These segments bear an anterior groove
and ventral setation similar to those of the maxillae.
The distal setation of the sixth segment resembles
that of the maxilla's fifth, but the dorsal setae are
reduced to a single seta at the distal margin of the
fourth segment. As with the juncture of the maxilla's
fourth and fifth segments, the articulations between
the fourth, fifth, and sixth segments of the maxil-
lipede are diagonal. The seventh segment of the limb
is developed with a ten-pronged claw (Fig. 32B-C,
34 A-D) similar to that seen on the maxilla.
The trunk limbs are all biramous paddles. The
first pair is somewhat shorter but not markedly nar-
rower than those that immediately follow (Fig. 28B,
C). The last trunk limb is much reduced (Fig. 28D).
The trunk limb rami are elongate and subrectan-
gular. The terminal segments of the rami are dis-
tinctly oval. The most common setae along the mar-
gins of the rami are plumose (Fig. 28C-x). On the
distal comers of the intermediate rami are located
the comb-like setae so characteristic of these limbs
(Fig. 28C-y). In Godzilliiis these are characterized
by a very long shaft with laterally directed, sharp,
curved denticles restricted to the distal half of the
shaft (Fig. 33D).
Order ENANTIOPODA Birshtein, 1960
Diag}iosis.— Compound eyes sessile; (?) anten-
nules and antennae biramous; mouthparts raptorial;
trunk segments with pairs of homonomous, paddle-
like limbs bearing five- or six-segmented "exopods"
and flap-like "endopods."
Remarks.— The published report with illustra-
tions and reconstruction of Brooks (1955) presented
an animal with simple flap-like mouthparts. De-
tailed restudy of the type and only known specimen
now indicates that the previous description of this
animal was not entirely accurate. Though the ma-
terial is too poorly preserved to allow a complete
reconstruction, suflicient evidence is at hand that
casts doubt on earlier diagnoses of this taxon.
Brooks (1955:853) originally described Tesnuso-
caris goldichi as "unlike any known arthropod." To
this end he employed a rather non-specific termi-
nology for the appendages, e.g., referring to a "first
cephalic appendage" rather than calling it an anten-
nule or antenna, but nonetheless placed the animal,
for no particular reason, within the Branchiopoda
incerta sedis. However, while Brook's paper was in
press, Sanders (1955) described the cephalocarid
Hutchinsomella macracantha. In a footnote to his
publication. Brooks (1955:853) assigned Tesnuso-
cans to the cephalocarids on ". . . the basis of the
unspecialized nature of the postcephalic tagma and
the presence of jointed appendages." It was Bir-
shtein (1960) who then formally recognized the sep-
arate status of these two genera and erected ordinal
names to accommodate them: Brachypoda for
Hutchinsoniella and allies, Enantiopoda for Tes-
nusocahs. However, Hessler (1969) rejected Tes-
niisocaris as having any relationship to brachypo-
dans.
The discovery of living nectiopodans sheds new
light on the question of enantiopodan affinities. Of
50
Schram, Yager and Emerson
compound eyes
antennule —
?trunk limbs
trunk sternite
Fig. 35. Tesnusocaris goldichi. Camera lucida drawing of holotype, USNMP 124173.
the two characters used by Brooks to define Tes-
nusocaris vis-a-vis the brachypodans, one — pres-
ence of jointed hmbs — is a general feature of all
arthropodous groups (see Schram, I986:chapter 2).
The other feature — unspeciaHzed post-cephahc tag-
mata — is not a characteristic of cephalocarids, even
scnsu lata. All crustaceans, except for the remipedes
and conchostracans, exhibit some degree of trunk
tagmosis. In the case of brachypodans, the thorax
is marked by the possession of multiramous leaf-like
limbs, but the abdomen lacks appendages altogether.
The presence of unspeciaHzed post-cephalic tagma
IS distinctive, but not of cephalocarids — or for that
matter any phyllopodans. It is, however, a diagnos-
tic feature of the remipedes!
This latter fact suggested to Schram (1983a) that
Remipedia Systematics
51
Tesmisocaris and the living remipedes were possibly
sister-groups. Further analysis (Schram, 1986) in-
dicated that nectiopodans and enantiopodans form
a primitive clade near the base of the crustacean
lineage (see below).
Family TESNUSOCARIDIDAE Brooks. 1955
Diagnosis. —Since there is only one family, the
diagnosis is the same as that of the order.
Type genus. — Tesmisocaris Brooks, 1955
Genus TESNUSOCARIS Brooks, 1955
Diagnosis. —Since there is only one genus, the di-
agnosis is the same as that of the family.
Type species. — Tesmisocaris goldichi Brooks, 1955
TESNUSOCARIS GOLDICHI Brooks, 1955
Diagnosis. Smce there is only one species cur-
rently recognized, the diagnosis is the same as that
of the genus.
//o/o/ype.— USNMP 124173, concretion with two
counterparts.
Locality. -V^Q%X of Rough Creek, 4300 ft. S 51 E
of Hill 4334. Dove Mountain Quadrangle, Brewster
County, Texas.
Stratum.— Tesrwis Formation, Lower Pennsyl-
vanian.
Remarks.— The description of this species by
Brooks (1955) is generally accurate regarding gross
body form. However, certain observations concern-
ing the cephalic limbs have proven to be inaccurate
and are corrected here. The preservation of this fos-
sil leaves much to be desired. Body outline and
shape are clearly discemable (Fig. 36A), but details
of appendage structure are obscure. Generally, best
results were obtained (FRS) by immersing the fossil
m alcohol, but the details thus revealed are difficult
to photograph (Fig. 36). To assist future workers in
study of this specimen, a camera lucida drawing of
the holotype (Fig. 35) is presented.
The shape of the cephalic shield and the sessile
compound eyes are as Brooks described. The sep-
arate first and second cephalic appendages of Brooks,
however, appear to form together a single biramous
limb. The short anterior branch (first cephalic ap-
pendage of Brooks) is not the single-segment flap-
like structure originally described, rather it appears
to be composed of at least five segments. The pos-
terior margin is setose, with the distal and basal
segments bearing longer setae than the intermediate
segments. This branch appears to arise from an ob-
scure basal portion that is closely associated with
the most proximal segment of the posterior branch
of the limb. This posterior branch (second cephalic
appendage of Brooks) is as originally described; and
the long, medially directed, somewhat curved setae
near the base are overlain by the long setae on the
base of the anterior branch. These branches taken
together would seem to be the antennules.
The real second cephalic limb of this animal was
not noted at all by Brooks. It is best observed with
very oblique lighting. The basal and distal parts of
the limb are not preserved on this specimen. How-
ever, just posterior to the base of the large posterior
branch of the antennules are a series of laterally
directed, setose and spinose segments that seem to
form parts of a pair of modest sized, biramous,
subflagellate limbs. These appear to represent the
antennae.
The labrum generally corresponds to the "bell-
shaped" form described by Brooks (Fig. 36B, C).
However, it should be noted that the anterior ex-
tremity is rather pointed, extending anteriorly be-
tween the bases of the antennules and antennae. In
addition, the posterior portion of the labrum is de-
hneated by a groove that appears to mark off"a struc-
ture that forms a large atrium oris. Under this lobate
posterior portion of the labrum can be clearly seen
the large molar processes of the mandibles described
by Brooks. These are so large, however, that they
do not seem to have been completely enclosed with-
in the atrium oris. Some material seems to have
fallen out of the fossil on the right side of the better
preserved counterpart, and the outline of these miss-
ing items is reminiscent of the form of the lacinia
mobilis and incisor process seen on nectiopodan
mandibles. No palp can be seen on the mandibles.
The fourth and fifth cephalic limbs outlined by
Brooks do not appear to exist at all in the forms he
described and reconstructed. Rather this region, lat-
eral to and posterior of the mandibles, is a complex
jumble of very setose and spinose segments with
their armatures directed medially (Fig. 36B). The
exact form, length, and number of the limbs rep-
resented by these segments can not be discerned on
the holotype. There are probably at least three pairs
of these limbs that seem to be directed somewhat
laterally. Posterior to these laterally oriented ap-
pendages there are an undeterminable number of
limbs that are directed posteriorly. These latter ap-
pear to have short, broad, and faintly setose joints;
and are actually rather similar in form to what is
known of the more clearly preserved trunk limbs
seen more posteriad on the body. It would appear
that the region just posterior to the mouth was
52
Schram, Yager and Emerson
Fig. 36. Tesnusocaris goldichi. Holotype, USNMP 1 24 1 73; A) whole body, 1 .0 x ; B) closeup of postoral region, 4.3 x ; C) closeup of
anterior head, 5.4 x. al— antennule, a2— antenna, 1 — labrum, mn — mandible, e— eyes, mp— mouthparts.
Remipedia Systematics
53
equipped with an array of robust mouthparts, and
that these were closely followed by the flap-like trunk
limbs that were already known from Brooks" de-
scription.
Unfortunately, the preservation of USNMP
124173 does not allow an accurate reconstruction
to be made of the ventral cephalon of Tesnusocahs.
However, the interpretation of the specimen that is
presented here (Fig. 35) does suggest that even more
clearly resolved relationships to the nectiopodans
may be drawn. The antennules and antennae seem
to be biramous, and the antennules bear long setae
on their bases that are suggestive of the aesthetasc
pads so characteristic of living remipedes. The la-
brum. now that distinct anterior and posterior areas
can be delineated, is very similar to that seen in
nectiopodans, as is the relationship of the molar
process of the mandible to the atrium oris. The limbs
in proximity to the mouth and mandibles, with their
robust setose and spinose endites, are evocative of
the grappling mouthparts of the Nectiopoda. Of
course, the significance of the apparent lack of trunk
tagmosis and the possession of simple, biramous,
paddle-like limbs on the segments of this region
have already been discussed by Schram (1983a,
1986).
More and better material of this species must be
sought in order to clarify our understanding of the
pertinent features of cephalic anatomy of this group.
Several characters declaim a separate status for en-
antiopodans from nectiopodans. The sessile com-
pound eyes, possible flagellar form of the antennae,
large size of the mandibular molar processes and
their apparently incomplete incorporation into the
atrium oris, and the possibly robust (but not nec-
essarily prehensile or subchelate) posterior mouth-
parts would appear to be unique.
DISCUSSION
The recognition and detailed description of sev-
eral species of nectiopodans now allow an outline
of the phylogenetic relationships within the order
to be proposed. At this stage, a phylogenetic scheme
of remipedes is tentative, and should be treated as
a working hypothesis. For this reason we have de-
liberately kept the supraspecific taxonomy of the
group rather simple, recognizing only three genera
in two clearly delineated families within the order
Nectiopoda.
Polarization of characters in a "new" group such
as this is difficult, especially because so many fea-
tures indicate that the taxon in question is a prim-
itive one near the base of the crustacean clade. Un-
der such a constraint, the sister group— all other
crustaceans — happens to contain what are com-
monly thought to be advanced taxa. However, no
group is ever completely derived nor completely
primitive in all its characters. One therefore cannot
make blanket judgements about individual char-
acters among taxa. To mitigate against this, one
should establish outgroups beyond the Crustacea,
but as Anderson (1973), Manton(1977), and Schram
(1978, 1986) have pointed out, the position of the
Crustacea (whether one accepts a distinct phylum
status or not) is so distinct from other arthropodous
types that selection of an outgroup from among the
many potential living and fossil groups is nearly
impossible. However, one can use the array of known
living and fossil articulates to construct some kind
of ancestral structural plan from which all crusta-
ceans could be derived. Conclusions drawn from
such an animal should be tempered by the caveats
of the uncertainty principle outlined by Schram
(1983/1).
As an example of the problems to be encountered,
let us consider polarization of some prominent rem-
ipede features. The chief distinguishing features of
remipedes are the presence of limbs on every trunk
segment and the lack of trunk tagmosis (features
homoplastic with similar conditions in Conchostra-
ca). Comparison to other crustaceans reveals some
ambiguous insights. For example, malacostracans
also have limbs on every trunk segment, but like
most other crustaceans the Malacostraca have trunk
tagma. Clearly, scoring of the polarity of these rem-
ipede characters on the basis of this comparison
would have to be uncertain. Considering outgroups
to Crustacea, both living (e.g., myriapods, primitive
uniramians) and fossil types (e.g., trilobites as well
as some of the Middle Cambrian, Burgess Shale
articulates, like Branchiocaris), would seem to in-
dicate that a condition with limbs on all segments
and no trunk tagmosis is a primitive one, that is,
classic theory for ancestral arthropod types (Hessler
and Newman 1975). In this case, remipedes would
be scored as primitive in limb location and lack of
trunk tagmosis.
A prominent nectiopodan feature is the devel-
opment of robust, uniramous, grappling mouth-
54
Schram, Yager and Emerson
Tesnusocans
Godzillius
Lasionectes
Speleonectes
goldichi
robustus
entnchoma
lucayensis ondmae
\
\
\
\ r^i
\
\
\
\39 /-37
\
\
\
\7-i(>
\
\
\-
26
y
\
-V22 ^
i-'L
-/40
\
\23
\^,0
-/-4I
\
■V24
\"
-/-12
\
\25
\
7^43
\
-V26
\
A 44
\
-V27
\
,y
-45
\
-V-28
y
\
\29
/
\
-V30
-32
\
-V31
33
-V-s
\
■f-M
-V-7
\
7*^35
-Vs
7^10
7^-12
-f-M
-/-16
-/-18
\-/-20
-/-36
Fig. 37. Cladogram of relationships of currently recognized
Remipedia. Apomorphic features: 1— broad, subquadrangular.
cephalic shield; 2 — bulbous labrum forming large atrium oris;
3 — mandible at least partly within the atrium oris; 4 — (?) man-
dible lacking palp; 5 — (?) mouthparts raptorial; 6 — (?) frontal
filaments absent; 7 — huge mandibular molar process; 8 — trunk
limb endopods with seven segments; 9 — no eyes; 10 — frontal
filaments with spines; 1 1— antennular aesthetasc pad; 12 — an-
tenna paddle-like; 13 — mandible tip completely within atrium
oris; 14 — mouthparts uniramous; 15 — mouthparts with elbow to
allow grappling; 16 — maxillule with terminal fang; 17 — basal
maxillulary endues mandible-like; 18 — maxilla with three diti-
form endites; 19 — maxillipedal segment fused to cephalon; 20 —
gonopores on base of fourteenth trunk limb; 21 —cephalic shield
subtrapezoidal; 22 — frontal filaments with "joints'"; 23 — anten-
nular ventral ramus blade-like; 24 — antenna with multiple rows
of setae on margins of endopod; 25 — third maxillulary endite
club-like; 26 — maxilla and maxillipede subchelate; 27 — maxilla
and maxillipede third segment wide with dense rows of setae on
crests; 28 — maxilla and maxillipede with grappling hook-like ter-
minal claws; 29 — maxilla with three segments beyond elbow;
30 — maxillipede with four segments beyond elbow; 31— genital
flap on leg base; 32 — maxillule with subtriangular endite on seg-
ment three; 33 — maxillule third endite cone-like; 34 — maxilla
with four segments beyond elbow; 35 — maxillipede with five seg-
ments beyond elbow; 36 — loss of sternal plates; 37 — posterior
segments at least with differentiation of sternal bars; 38 — maxilla
and maxillipede with trifid terminal claws; 39 — genital flap on
fourteenth sternal bar; 40 — maxiUules with robust apical setae
on endites of second and (41) third segments; 42 — maxilla and
maxillipede prehensile; 43 — maxilla and maxillipede bear ar-
cuate endites on third segment; 44 — maxilla and maxillipede
have rows of widely spaced simple setae on distal segments of
limb; 45 — maxilla and maxillipede with comb-like, semi-circu-
lar, terminal claws; 46 — apical setae on maxillulary endites sub-
setulate. A negative character ( - ) denotes reversal of feature.
parts. In the analysis of this feature, changes in our
understanding of nectiopodan outgroups has caused
some problems. Schram (1986:chapter 43) consid-
ered the sister group of the Nectiopoda, the enan-
tiopodan Tesmisocahs goldichi. He noted that
Brooks described and reconstructed the first two
post-mandibular appendages as simple setose lobes.
Examination of the outgroup to remipedes, i.e., all
other crustaceans, revealed simple setose mouth-
parts was the norm. Hence, it might have been as-
sumed that the grappling form of the mouthparts of
the nectiopodans is an advanced condition.
However, the recognition herein that Tesnuso-
caris also may have had raptorial mouthparts makes
the issue of the form of ancestral crustacean mouth-
parts an open one. Though other crustaceans gen-
erally have simple setose lobes for maxillules and
maxillae, there are some exceptions (e.g., some co-
pepods and ostracodes) in which the mouthparts are
raptorial. Furthermore, in light of the discussion of
the evolution of crustacean feeding types by Schram
(1986:chapter 44) it would appear that a series of
raptorial type mouthparts may prove primitive, and
that the simple setose lobes so common among otlier
crustaceans may be derived. In light of this possi-
bility, reliance for the time being is placed on the
tendency of evolution to go frequently from the sim-
ple to the more complex. In this instance, simple
mouthparts are scored primitive and raptorial forms
are considered derived; thus the form of the mouth-
parts in nectiopodans, and possibly enantiopodans
as well, are judged as an autapomorphy.
In the present study, we utilized 46 characters for
five species. However, our analysis was tempered
by the recognition of two (possibly three) additional
nectiopodan species not described. These taxa are
known only from single specimens, and we have
chosen not to describe them at this time pending
the collection of more material. These taxa appear
to be related rather closely to the genus Speleonectes
and were useful in delineating the order of appear-
ance of certain characters in the cladogram of Figure
37. The analysis was done using the computer fa-
cilities of the California State University system;
and employed PIMENTEL, an option within the
PHYSYS package. This is basically a modification
of the well-known WAGNER 78 program that seeks
to produce the most parsimonious arrangement of
taxa with the highest degree of congruence and low-
est amount of homoplasy of the characters used.
The class Remipedia is distinguished by a broad,
rectangular cephalic shield ( 1 ); a bulbous, well-de-
veloped labrum which extends posteriorly to form
Remipedia Systematics
55
a large atrium oris (2); mandibles that are at least
partially within the atrium oris (3); (?) mandible
lacking a palp (4); and (?) raptorial mouthparts (5).
Recognition of characters 2 and 3 have resulted from
the present study, but the resolution of characters 4
and 5 must await the discovery of more and better
material of Tesnusocaris.
The order Enantiopoda is characterized by a pos-
sible lack of frontal filaments (6), an enlarged molar
process on the mandible (7), and the trunk limb
endopods with 5 or possibly 6 segments (8). The
possession of eyes, biramous antennules, and subfla-
gelliform biramous antennae are ajudged as prim-
itive features (though the sessile and compound na-
ture of the eyes might be apomorphic). The fact that
the mandibles of Tesnusocaris are only partially in-
corporated into the atrium oris might be an inter-
mediate step between a condition where the man-
dibles are a completely external set of limbs — as seen
in almost all other crustaceans— and one in which
the mandibles are completely incorporated into the
atrium oris — as seen in the Nectiopoda. The long,
lash-like setae seen on the basal segments of the
antennular rami of Tesnusocaris could also be in-
terpreted as an intermediate stage towards the de-
velopment of the prominent aesthetasc pad seen at
the base of the nectiopodan antennules. In short,
the Enantiopoda seem to provide insight into how
the class Remipedia evolved.
The order Nectiopoda is characterized by a lack
of eyes (9); frontal filaments with an accessory spine
(10); an aesthetasc pad on the antennules (11); pad-
dle-like form of the very setose antennae (12); man-
dibles with their distal ends completely incorporat-
ed into the atrium oris (13); uniramous mouthparts
(14); mouthparts developed with an elbow to allow
some kind of flexion of the limbs for grappling (15);
maxillules developed as a fang-like claw (16); the
two most proximal maxillulary endites "mandibu-
lariform," and these endites flanking the mouth in
the place of the mandibles (17); the maxillae with
the proximal-most endites as three digitiform struc-
tures (18); fusion of the maxillipedal segment to the
cephalon (19); and gonopores located on the bases
of the fourteenth trunk limbs (20). Most of these
diagnostic features are directed towards the spe-
cialized mode of carnivorous feeding seen in nec-
tiopodans (further discussion in this regard will await
the analysis of internal anatomy now under way).
The family Godzilliidae possesses a number of
very distinct features. The head shield is subtrape-
zoidal, i.e., rather narrow in its anterior aspect (21);
the frontal filaments are very long and seem to have
a number of "joints" along their length (22); the
antennular ventral ramus is blade-like (23); the an-
tenna bears multiple rows of plumose setae along
the margins of the endopod (24); the maxillulary
third endite is a large club-like process (25); the
maxillae and maxillipedes are subchelate (26); the
maxillae and maxillipedes have very wide third seg-
ments, and bear dense rows of simple setae along
their entire lengths (27); the maxillae and maxil-
lipedes have terminal claws in the form of multi-
pronged grappling hooks (28); the maxillae have
three segments beyond the elbow (29); the maxil-
lipede has four segments beyond the elbow (30); and
the genital flap that protects the opening of the gen-
ital pore is located on the base of the leg (3 1 ). Several
of the aptations of this creature, especially those of
the maxillules, seem to indicate a large animal hav-
ing to locate and immobilize large prey items.
The family Speleonectidae can be characterized
generally, vis-a-vis godzilliids, as more delicately
structured beasts. They are defined by the maxillules
having a modestly well-developed, thumb-like en-
dite on the second segment (32) and a subtriangular
endite on the third segment (33), the maxillae have
four segments beyond the elbow (34), the maxil-
lipedes have five segments beyond the elbow (35),
the sternites generally are not developed as plates
(36) though the form of the sternal bars is differ-
entiated (37).
The genus Lasionectes bears certain similarities
to Godzillius. The maxillae and maxillipedes are
subchelate (26) and the third segment of these limbs
is quite wide, having dense rows of simple setae all
along the edge (27). However, the terminal claws of
the maxillae and maxillipedes are trifid (38) and the
genital flap that protects the genital opening is lo-
cated on the lateral aspect of the sternal bar of the
fourteenth segment (39).
The genus Speleonectes is characterized by the
maxillules with robust apical setae on the endites of
the second (40) and third segments (4 1 ); the maxillae
and maxillipedes are prehensile (42), bear rather
arcuate endites on the third segments (43), have
widely spaced rows of simple setae along the mar-
gins of the distal segments (44), and have terminal
claws that are a semicircular row of comb-like spines
(45).
Speleonectes lucayensis is distinguished from its
sister species largely by a feature that it shares with
Lasionectes, i.e., it possesses a genital flap on the
lateral aspect of the fourteenth sternal bar (39). On
the other hand, 5. ondinae is characterized by the
possession of a genital flap located on the base of
56
Schram, Yager and Emerson
REMIPEDIA
MALACOSTRACA
PHYLLOPODA
MAXILLOPODA
Fig. 38. Cladogram of crustacean classes modified from Schram
(1986). Apomorphic features: 1 —two pair of antennae; 2 — bira-
mous antennules; 3 — two pairs of maxillae; 4 — nauplius larva or
egg-nauplius stage; 5 — broad subquadrangular cephalic shield;
6 — labrum forming large atnum oris; 7 — mandible at least par-
tially enclosed within atnum oris; 8 — mandibular palp lacking;
9 — (?)raptory mouthparts; 10 — postcephalic tagmosis; 11— typ-
ically at most eight thoracic segments; 12 — malacostracan nau-
pliar eye; 13 — polyramous limbs; 14 — stenopodous thoracic en-
dopods; 15 — uropods; 16 — carapace that covers only, or at least
parts of, thorax; 17 — abdomen typically lacks limb; 18 — unira-
mous antennules; 19 — leaf-like (foliaceous) thoracopods; 20 — at
most 1 1 trunk segments; 2 1 —no more than six thoracic segments;
22 — short, bulbous heart; 23 — maxiUopodan naupliar eye.
the fourteenth limb (31), a loss of differentiation in
the form of the sternal bars of the posterior trunk
segments ( — 37), and the apical setae on the max-
illulary endites being subsetulate (46). As mentioned
above in remarks on 5'. ondinae. it remains to be
determined whether the body form of this species,
i.e., the high head to body ratio and relatively low
number of body segments, is due to some paedo-
morphic process in the evolution of the taxon or
merely to our only having subadult specimens at
hand.
Recognition of the class Remipedia has had a
profound effect on understanding the phylogeny of
the Crustacea (Schram 1986). It was thought pre-
viously that the brachypodan cephalocarids repre-
sented something close to an ancestral type, an idea
derived from the mixopodial theory of crustacean
limb evolution developed by Borradaile (1917,
1926). He postulated that polyramous, leaf-like limbs
gave rise to biramous forms (see Schram 1983(3 for
details). This idea stood in contrast to the biramous
theory of Cannon and Manton (1927), which had
the advantage of moving from the simple to the
complex in regard to limb form. However, until the
discovery of the nectiopodans in 1981, the only
known living forms in which adults possessed bira-
mous limbs (various maxillipodan types) were all
considered to be derived in regard to body plan, i.e.,
copepods, ostracodes, barnacles and their allies. The
delineation of a class Remipedia placed a biramous
limb type onto what is generally conceded to be a
primitive Bauplan; i.e., one in which there is a pair
of limbs on every trunk segment and no tagmosis
or regionalization of the trunk.
The concept of a cephalocarid-like ancestor had
a rather inconvenient side effect. Attempts at draw-
ing a phylogenetic tree of crustacean relationships
typically resulted in the production of a "phyloge-
netic grass." That is, with cephalocarids as an ances-
tor, no clear view could be developed as to rela-
tionships of basic crustacean types; indeed, there
was no consensus as to just what were the basic
Baiiplane of the groups. Crustacean taxonomies
usually contained six or more classes, and the dis-
covery of new groups (e.g.. mystacocarids or tan-
tulocarids) usually resulted in their arbitrarily being
installed at a class level. This sort of scheme stood
in stark contrast to the accepted phylogenies within
other arthropodous groups, such as uniramians and
cheliceriforms, in which generally clear concepts of
relationships had developed, and for which a rela-
tively few basic classes were accepted.
Schram ( 1 986) utilized methods of cladistic anal-
ysis to evaluate characters in an attempt to arrive
at a parsimonious tree of relationships for all crus-
taceans. The method was not used slavishly, how-
ever, since it was recognized that any kind of cla-
distic analysis must be tempered with consideration
of functional morphology. Schram (1986) also at-
tempted to evaluate the effectiveness of a remipede
versus a cephalocarid ancestral type. Both groups
have derived features (i.e., autapomorphies) which
preclude their being viewed as direct ancestors of
all other crustaceans. However, cladistic analyses
are based on character matrices. Characters are
scored as primitive or derived based on the outgroup
analysis of the individual features rather than in
which group the features may happen to occur.
Schram ( 1 986) can be consulted for details, but one
conclusion of that study was that cladograms with
remipedes as ancestral types were shorter and more
highly resolved (i.e., more parsimonious) than ones
with cephalocarids as ancestral types.
Indeed, a consequence of developing a remipede
rooted phylogenetic tree (Fig. 38) is to suggest a
Remipedia Systematics
57
Fig. 39. Distribution of fossil and living Remipedia. Atlantic basin shown with mid-ocean ndge and fracture system. • Tesnusocaris
goldichi, lowermost Pennsylvanian of Texas; ▼ various Nectiopoda. West Indies; ■ Speleonecles ondinae, Lanzarote, Canary Islands.
Inset A— see Figure 40 for details; Inset B— location of continents 165 million years ago before opening of Atlantic Ocean.
more logical scenario for crustacean evolution than
had been available previously. An essentially long
bodied, unregionalized, cephalic feeding animal with
mandibular palps was seen to give rise to Remipedia
on one hand as well as other types of crustaceans
on the other. The first step in the evolution of higher
crustaceans was to regionalize the body. This ap-
parently allowed several things to occur. Reproduc-
tive and locomotory functions could be clearly de-
lineated in the somite division of labor. Locomotory
subspecializations could be achieved with some
limbs and regions being specialized for swimming
(e.g., uropods) and others for walking (e.g., steno-
podous endopods). Furthermore, other methods of
food procurement could be developed, with some
lines experimenting with various cephalic strategies
and others incorporating the thorax into feeding be-
haviors. Reduction in total number of body seg-
ments climaxed in fixation on no more than eight
segments in the thorax.
The first offshoot of this initial differentiation re-
sulted in the evolution of the immensely successful
Malacostraca. In this class most variations on the
above options were explored. In connection with
this radiation, a type of multiramous limb— that
with a stenopodous endopod — was evolved.
Subsequently, the main theme of crustacean evo-
lution was directed at further reduction of the trunk,
both in numbers of segments as well as a strong
tendency to lose limbs on the abdomen. Perhaps as
a consequence of this paedomorphosis, most of the
following crustaceans share the possession of uni-
ramous antennules and many lack mandibular palps.
Two main lines developed, each exploiting different
modes of food procurement, and these lineages con-
tain the most highly derived of crustaceans.
The class Phyllopoda (similar to the Thoracopoda
of Hessler and Newman, 1975) developed polyra-
mous leaf-like limbs that function in a unique meth-
od of thoracic filtration. The major groups within
58
Schram, Yager and Emerson
Fig. 40. Islands in West Indies (shaded) currently known to harbor Nectiopoda. See Table 5 for details.
this class are: the Phyllocaiida, a group that still
retains most of the abdominal limbs, and developed
a unique flap-like branch to the antennule; the Ceph-
alocarida, which contains the living brachypodans
and the Devonian lipostracan Lepidocaris; the Sar-
sostraca or Anostraca, which lack not only a cara-
pace but a head shield as well; and the Calmanos-
traca, i.e., the branchiopods with carapaces such as
notostracans and diplostracans.
The class Maxillopoda contains crustaceans that,
with the one major exception of the barnacles, ex-
ploit cephalic feeding modes. However, maxillo-
podans tend to have repeatedly evolved various
methods of parasitism and the class is generally
marked by distinct reductions in the development
of the trunk and limbs. The Cirripedia sensii stricto
evolved yet another special mode of thoracic feed-
ing, the filtratory cirri. The maxillopodan trunk gen-
erally does not exceed 1 1 segments, and the thorax
seems fixed at no more than six somites. The con-
stituent groups of the Maxillopoda are frequently so
highly derived that proposed relationships of the
group are rather unresolved (see e.g., Grygier 1983,
or Schram 1986). The major maxillopodan groups
are: Tantulocarida, Branchiura, Mystacocarida, Os-
tracoda, Copepoda, and Thecostraca. The first three
of these may bear some relationship to each other.
The last of these includes the barnacles and their
relatives. To these should now be added the Skar-
acarida of Miiller and Walossek (1985), but the exact
affinity of these Cambrian beasts within the class is
uncertain at this time.
One final matter requires some comment. Though
the remipedes are a primitive group, apparently a
very ancient one, they are not widely distributed.
Though nectiopodan studies are still few. all forms
discovered to date have been part of a well-estab-
lished western Tethyan distribution. The Canary Is-
lands and British West Indies, where nectiopodans
have been collected (Figs. 39, 40), are part of a region
(the Caribbean, central west Atlantic, west Africa,
and the Mediterranean) which is known to contain
a common fauna of interesting crustaceans. In ad-
dition to nectiopodans, this region is noted for such
Remipedia Systematics
59
Table 5. Nectiopodans collected in known localities for the
group in the West Indies. New species I has been collected from
two caves on different islands (la & lb), and the single specimen
from each may or may not be in the same species.
Locality
Nectiopodan taxa
Lucayan Cavern, Grand
Bahama
Old Freetown Cave, Grand
Bahama
Dan's Cave, Abaco
Long Island
Old Blue Hill Cave,
Providenciales
Airport Cave, Providenciales
Cottage Pond, North Caicos
Speleoneclcs lucayensis
adults and juveniles
Speleonectes juveniles
New species la
GodzilUus juveniles
Speleonectes j\i\em\e%
New species lb
unidentified nectiopod
Lasionecles enlrtchoma
adults and juveniles
Lasionecles juveniles
Lasionectes entrichoma
GodzilUus rohustus
New species II
phylogenetically interesting crustacean forms as
thermosbaenaceans, stygiomysids, procarid euky-
phidans, mictaceans, and certain hypogean amphi-
pods. Interestingly, the only known fossil remipede,
the enantiopodan Tesmisocaris. also occurs adjacent
to this Tethyan realm in western Texas.
This distribution indicates several things. First,
the group's history seems to be closely linked with
the ancient Tethyan Sea and the subsequent for-
mation of the Atlantic Ocean (Fig. 39B). Second,
their restriction to caves in just this area implies
that nectiopodans have rather limited powers of dis-
persion and/or highly specific environmental re-
quirements. Though some cohabitants of their fauna
are found in the open ocean as well as in caves, e.g.,
the mictaceans and some amphipods, it would seem
that the deep-ocean origin postulated for at least
some of this fauna (Hart et al. 1984) may not apply
to the nectiopodans. Third, though one can never
rule out a serendipitous discovery of a nectiopodan
outside this realm (witness Procaris spp. on the
Hawaiian Islands juxtaposed against their occur-
rence on Ascension Island and Bermuda), it appears
that the greatest opportunity to find more nectio-
podans would be to explore caves in the Greater
Antilles, Mediterranean, and other islands in the
archipelagos where they have already been collected.
Another important aspect of nectiopodan distri-
bution also holds great promise for future discov-
eries. Nectiopoda usually do not occur in isolation,
but are more often found sympatrically with other
nectiopodans (Table 5). The ecological explanation
for this is difficult to understand. All nectiopodans
share the same body plan, and differences between
taxa are not that great. With the exception of the
large form, Godzillius rohustus. all the animals are
in the same size range and presumably dine on sim-
ilar prey. How these animals have subdivided cave
niches so that several species can coexist is not
known. To resolve this question will require pro-
longed and repeated observation of nectiopodans,
both in their native habitat as well as in the labo-
ratory. For the time being, however, it is useful to
note that, though they are not typically abundant in
absolute numbers, where one nectiopodan species
occurs, more will probably be found.
ACKNOWLEDGMENTS
We wish to thank the following for the time and
effort they expended in helping us in field collection:
Howard Cosgrove, Mary Ellen EckofT, Sam Harvey,
Paul Hobbs, Tom Iliffe, Wayne Kafcsak, and most
particularly Dennis Williams. We would also like
to thank the following institutions for their assis-
tance: the PRIDE Foundation on Pine Cay, Turks
and Caicos, and the Bahamas National Trust for
access to Lucayan Cavern. SEM pictures were taken
with the assistance of Bryan Burnett and the facil-
ities of the Dept. of Pathology, University of Cali-
fornia, San Diego. Line drawings were executed in
part by Bryan Burnett. The manuscript was re-
viewed by Drs. Thomas Bowman, Richard Brusca,
Bruce Felgenhauer, Raymond Manning, and Wil-
liam Newman. This research was supported by Na-
tional Science Foundation grant BSR 82-12335 to
FRS.
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