Marria, A Neglected Fossil from the Burgess Shale

 Larry Solomon, 2006

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The Middle Cambrian (c.530 mya) fossils found by Charles D. Walcott in 1909 in the Burgess Pass of British Columbia have received considerable attention in the last two decades. Even in the popular press, books have been published, such as The Burgess Shale by Harry B. Whittington (1985),  Wonderful Life by Stephen Jay Gould (1989) and The Fossils of the Burgess Shale by Briggs, Erwin, and Collier (1994). It is unusual for the popular imagination to be captured by invertebrate fossil life -- usually such interest is restricted to dinosaurs and humans.

There are several reasons that the fossils of the Burgess shale are so unusual and important. Firstly, their age is significant, because the Cambrian was for a long time believed to be the age when life first appeared on Earth. That is no longer so, but the Cambrian era is still considered seminal for the development of complex life forms, especially the metazoans, and it is still considered the period in which life "exploded" into a myriad of complex  new forms. This "explosion" is often called the "The Cambrian Explosion" (CE).  Nowadays, CE doesn't seem to receive the debate that it once did and still warrants. It seems that science has tacitly accepted it as though it is fact. However, I believe that CE is an illusion. The sudden occurrence of fossils of great variety during this era are almost exclusively fossils of the hard parts of marine animals -- shells mostly. Even in the earliest Cambrian, trilobites with a complex eye and other complex body structures are common. These could not have appeared without previous evolutionary forms, yet undiscovered. Hard shells probably evolved during the Cambrian, thereby making their fossilzation possible. Earlier life forms probably didn't have these hard shells -- just soft parts, making fossilzation much more improbable. Earlier fossils have been discovered recently, but they seem to have no links to much of the Burgess shale fauna. Some are just as bizarre, e.g., the Vendian faunas, and the earliest are invariably very much simpler, e.g., cyanobacteria. It is rare, but not impossible, for soft parts to be preserved in the fossil record. That is one of the reasons that the Burgess shale fossils are so important and unusual. Cyanobacteria are mostly preserved in the form of stromatolites, hard skeletons that bacteria built and lived in. For a long time stromatolites were not considered life forms at all. Many experts considered them to be rock forms that resembled life, but not really life. Then living stromatolites were found off the west coast of Australia, and elsewhere. They made exactly the same forms as the fossils. So stromatolites are among the oldest and longest continuously living life forms on the planet.

Another factor that makes the Burgess fossils important is their extraordinary preservation. Very fine details, soft parts, and even internal organs of  these ancient animals are captured in the rock matrices. Such detailed preservation is very rare. They are also interesting because many of their forms are bizarre, or at least very unusual, and in some cases, have defied classification into any of the standard categories of life. We still don't know what some of them are, where they fall in the line of evolution, or how they fit into known  biological categories. Some of the forms do not occur in the surrounding ages of evolutionary history; i.e., they are unique and don't seem to have any links to life before or after them. No one knows where they came from or where they led. Not all of these forms are unusual or bizarre, however. Some, however, do fall nicely into known families, like those of trilobites and sponges.

In 1931 Rudolf Ruedemann described a new Crustacean from the Burgess shale that he named Marria Walcotti. Plate 5 showed Ruedemann's reconstruction of this bizarre animal.

marria
Plate 5 from the article by Ruedemann, which follows.

Plate 4, from the article that is reproduced below, shows an unretouched photograph of the actual fossil. The holotype and paratype, which are in the USNM as No. 83485, may be the only specimens of this strange creature. The locality from which it was collected is on Mount Strephen, rather than from the Burgess pass. What I find as strange is the absence of any mention of this specimen in subsequent publications about the Burgess shale fossils.

From the article text reproduced below, Ruedemann wrote "There is no fossil crustacean that can be directly compared with Marria walcotti. The only fossil form that to our knowledge in a general way resembles it is the grotesque Bostrichopus antiuus Goldfuss of the lower Carboniferous (Culm) of Nassau, Germany." (see reproduction below, Figure 1.)

Later, he states:
 "The great age of the form and the fact that a similar development of the antennae (at least of the second pair) takes place in at least two orders of the Branchiopoda, namely, the Phyllopoda and the Cladocera, as well as in the next order, the Copepoda, make it probable a priori that the species represents a generalized type, not directly referable to any of the recent orders of crustaceans. Positive determination of its relationship is prevented by the fact that
 the mandibles and maxillae remain unknown and that the subdivisions of the body can not be definitely made out."

Perhaps someone can shed some light on the apparent enigmatic disappearance of this fossil from the records. For those who are curious, I would like to offer a few pictures of recent animals that seem to me to bear some resemblance. These are all Copepods from Ernst Haeckel's Kunstformen der Natur (1904)..

Haekel

  1. Calanus pavo (Dana)
  2. Clytemnestra scutellata (Dana)
  3. Oncaea venusta (Philippi)
  4. Cryptopontius thorelli (Giesbrecht)
  5. Acontiophorus scutatus (Brady)
  6. Corycaeus cenustus (Dana)
  7. Sapphirina darwinii (Haeckel)
  8. Augaptilus filigerus (Giesbrecht)
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The following article is reproduced from  From the Proceedings of the United States Museum, Vol 79, Art 27
Smithsonian Institution, United States National Museum, Washington, D.C., 1931

SOME NEW MIDDLE CAMBRIAN FOSSILS FROM BRITISH COLUMBIA
                                     By RUDOLF RUEDEMANN
                         New York State Museum, Albany, N. Y. 1931

  The Middle Cambrian faunas of British Columbia, particularly
the marvelous assemblage of organisms from the Burgess Pass, dis-
covered by Dr. Charles D. Walcott in 1910 and studied by him
throughout the remainder of his life, continue to afford most inter-
esting subjects for research. A small group of these fossils from
the Burgess shale and the Stephen formation was sent me some time
ago by the authorities of the United States National Museum for
further study. In their general appearance they suggest graptolites,
and as such had been laid aside for future study by Doctor Walcott.
Upon close study, however, they have proved to be an unusually
interesting and at the same time difficult assemblage of fossils, none
of which belong to true graptolites. It is with the full realization
of the tentative nature of the determinations that the following
results of my studies are published.

marria
Plate 4


        PROCEEDINGS OF THE NATIONAL MUSEUM        VOL. 79
                                  CRUSTACEA
                  MARRIA WALCOTTI, new genus and species
                                   PLATES 4-5

   Two specimens (from the famous fossil bed on Mount Stephen,
 Loc. 14s), when seen with the naked eye are amazingly suggestive
 of a graptolite such as Nemagraptus gracilis. They were laid aside
 by Doctor Walcott with the other supposedly Cambrian graptolites.
 After the study of these two specimens on which the following
 description and discussion are based, further search yielded five
 more incomplete ones, most of which had been regarded as frag-
 ments of the sponge Pirania muricata Walcott.1
   When the specimen selected as the holotype was studied under
 the microscope it lost its graptolitic aspect and revealed itself as
 the segmented body of a crustacean with large regularly jointed
 arms, each joint of which gives rise to a side branch. In other
 words, it is a bizarre crustacean, its immense swimming feet serving
 to distinguish it from all other Cambrian crustacean genera.
     Inasmuch as Marrella may become a synonym, if my subsequent
 contentions are sustained, and thus nullify the compliment that
 Doctor Walcott wished to pay his friend Prof. John E. Marr, of
 St. Johns College, Cambridge University, I am calling this new
 crustacean Marria in order to perpetuate the compliment.
      Description.—Body small (7.5 mm. long and 3.5 mm. wide in com-
 pressed condition), elliptical in outline, with truncated front. Cara-
 pace of head (or cephalothorax ?) of subquadrangular outline (about
  3.25 mm. long and 3.5 mm. wide) occupying half of the body.
  Postcephalic portion (either thorax + abdomen or abdomen only)
  consisting of seven (or possibly eight) simple segments, the first of
  which is 0.7 mm. long, the others decreasing slightly in length as
  well as regularly in width. There is no trace of a telson or of caudal
  styles. The frontal portion of the supposed head possesses a sub-
  triangular depression, the base of which is in front. Near the apex
  is a small tubercle with a central depression, strongly suggesting the
  presence of an eye. Since the surfaces of the head and segments show
  no sculpture, they were apparently smooth. On the head, to the left
  and right and behind the eye, are several irregular nodes, which may
  be incidental to the preservation. There is also a pair of black spots
  or minute tubercles on either side of the eye. A distinct tubular de-
  pression, suggesting the alimentary canal, begins behind the eye,
  where it is somewhat wider, and extends backward to the first
  segment.
       The most important feature of this organism is the presence of
 the two pairs of immense swimming appendages, both of which
 proceed from the anterolateral corners of the head. Both are funda-
 mentally biramous, dividing into two principal branches, which in
 turn send out a series of secondary, filamentous branches bearing
 setae on one side. The first pair, which is the shorter, is directed
 forward, the second sideways. Only one of the first pair (on the
 right side) of swimming appendages is preserved. The protopodite
 is short and stocky. One of the branches (exopodite) has only the
 base preserved; the other branch (endopodite) bears four or five
  (one displaced) long, flexuous, secondary branches and shows the
 base of a fifth or sixth. The series of secondary branches on the
 exopodite from the four bases shown on the stump in front of the
 head, as drawn in the restoration (pl. 5), are conjectural. We can
 not determine whether this first pair of appendages represents the
 first pair of antennae or the second; if the latter, the first pair of
  antennae may have been small or very tenuous.
      The second pair of swimming appendages is by far the larger
  of the two and may either represent the second pair of antennae or
  may correspond to the mandibular foot of the nauplius. (See under
  -Relationships.) The protopodite is again short and powerful and
  appears to consist of two joints. The forward division of the foot,
  which we take to be the exopodite, is extended horizontally and
  reaches a length of 20 mm.; the number of its joints can not be defi-
  nitely established. On one side it bears 7 to 11 thin flexuous sub-
  branches (exites) and on the other about 6, which branch off nearer
  the base. The posterior division of the swimming foot, according to
  our view the endopodite, curves backward nearly parallel to the
  body, giving off about 10 slender, thin endites, about 14 mm. long,
  on the outer side of the branch, and terminates in a similar but
  shorter (9.5 mm.) endite.
      All the exites and endites are provided with short setae on one
  side. These, however, may be only the bases of longer bristles, since
  there is one fragment that retains long stiff setae on the portion of
  the swimming appendage preserved.
      On the left side are three simple legs, two of which undoubtedly
  proceed from the underside of the head, and the third (not drawn on
  restoration) appears to do so. On the right side are the bases
  of what appear to have been abdominal feet, the stumpy second,
  however, being doubtful. There is no evidence of a biramous struc-
  ture or of gills, the exopodites apparently alone protruding beyond
  the body.
      Occurrence.—Middle Cambrian, Stephen formation (Loc. 14s),
  Mount Stephen, British Columbia.
    Holotype and paratypes.—U.S.N.M. No. 83485.
    Relationships of Marria.—There is no fossil crustacean that can be
  directly compared with Marria walcotti. The only fossil form that

to our knowledge in a general way resembles it is the grotesque
Bostrichopus antiquus Goldfuss of the lower Carboniferous (Culm.)
of Nassau, Germany. (See fig. 1.) The one specimen known to
have been found is preserved in the Bonn collection. Good figures
are given in part 1 of Roemer's Lethaea geognostica (1876), pi. 38,
figs. l0a-b, and recently (1929) Steinmann has redescribed it, giving
a restoration. According to Goldfuss's figure this minute crustacean
is surrounded by a corona of 60 extremely thin, flexuous, filamen-
tous appendages, radiating from three (or four?) short basic ap-
pendages, located behind the head. Steinmann reconstructs the
form as having the filamentous feet distributed evenly in pairs on
the segments of the body and concludes that the species belongs to
an entirely extinct class of crustaceans. Even though the swimming
feet have a similar structure, our species is still different in the form
 of the body, especially of the head, which bears two large eyes in
 Bostrichopus.

bostrichopus         
       
     The outstanding characters of Marria are the very simple body
 and the enormous development of the antennae (see postea), which
 indicates an extreme adaptation of an otherwise primitive form.
      The great age of the form and the fact that a similar development
 of the antennae (at least of the second pair) takes place in at least
 two, orders of the Branchiopoda, namely, the Phyllopoda and the
 Cladocera, as well as in the next order, the Copepoda, make it proba-
 ble a priori that the species represents a generalized type, not
 directly referable to any of the recent orders of crustaceans. Posi-
 tive determination of its relationship is prevented by the fact that
 the mandibles and maxillae remain unknown and that the subdivi-
 sions of the body can not be definitely made out. How uncertain are
 the determinations of Cambrian crustaceans from incomplete re-
 mains is clearly evidenced by the fact that Walcott's determinations
 of the Burgess shale crustaceans were challenged by Fedotov (1925)
 and Fedotov's in turn by Henricksen (1928).
  Other important characters of Marria are the immense develop-
ment of two swimming arms (first and second pair of antennae, see
postea), the large unsegmented head with carapace (possibly cephalo-
thorax) bearing a single eye, five pairs (or less) of legs, a simple
abdomen, consisting of about seven segments, and the absence of a
telson.
    It is customary to refer the earlier Paleozoic crustaceans to the
suborder Phyllopoda of the order Branchiopoda, because these are
the oldest and most primitive crustaceans. [The recent genus Apus,
or Lepidurus, has been traced to the Permian (Ruedemann, 1922).]
There is indeed a close resemblance to the family Limnadiidae of the
Phyllopoda—particularly to Limnetis in the biramous, strongly
developed second antennae, the single (not bivalved) carapace, the
fused compound eyes in the middle of the head, and the small num-
ber of thoracic feet. Although a telson is present in Limnetis, in
L. brachyura it is so small that this species appears but little differ-
ent from our specimens in this respect. The body of the Limnadi-
idae is, however, laterally compressed and the carapace covers most
of it.
  According to common consensus of opinion the Limnadiidae lean
toward the second suborder of the Branchiopoda, the Cladocera.
 Marria also has important characters in common with Cladocera,
namely, the strong development of the biramous second antennae
into principal organs of locomotion, the fused compound eyes, and
the short body with a small number of thoracic limbs. Though the
Cladocera have a telson, it is variable in size and in some species
 much reduced. The carapace is likewise variable, for while it is
 most frequently a bivalve shell inclosing the whole postcephalic
 region of the body, it may be reduced to a mere brood pouch, as in
 Leptodora. The segmentation of the body is little pronounced, if
 not obscure, the thorax bearing as many pairs of limbs as there are
 segments; the abdomen having but three segments, bearing no limbs,
but with a telson. The head in the Cladocera, however, is always
 bent downward so that the first pair of antennae and the median eye
 are on the ventral side.
      It will be seen that our form, though not directly referable to the
 Cladocera, agrees well with that order in the development of the
 second antennae, the carapace (aside from its common bivalve form
 in the Cladocera), the fused eyes, the small number of segments, and
 thoracic limbs. It would seem to differ in not possessing the down-
 ward bend of the head or a telson.
     Our species also invites comparison with the second order of
 crustaceans, the Copepoda, in regard to the possible retention of the
 single nauplius eye, the strongly developed biramous second pair of
 antennae, and the possible absence of a carapace. The Copepoda
differ from Marria in having five pairs of biramous feet, the first of
which is attached to the cephalothorax and the others to the thoracic
somites. On the other hand, the strong development of plumed
hairs in the pelagic forms may well be duplicated in Mama. Some
of the members of the family Peltiidae of the suborder Podoplea
have even flattened bodies, somewhat like isopods and probably
Marria.
     Finally, the close resemblance of our form to the nauplius of
many crustaceans, among them even the Cirripedia and Malaco-
     
naupilus 

straca, is undoubtedly most striking. These bear not only a single
eye but also two pairs of large biramous swimming legs, formed by
the second pair of antennae and the mandibles. These biramous
limbs, as, for example, in the nauplius of Lepas (see fig. 2), bear a
large number of long spines, which in turn are set with stiff setae,
the whole producing an organ strangely resembling that of Marria
in which the spines are further developed into jointed secondary
branches (endites and exites). As we can not be certain that thft
two pairs of swimming limbs of Marria represent the first and
second pairs of antennae, it is possible to assume that they may be
the second antennae and mandibles and that we see in the nauplius,
and still more so in the following protozoaean larva of the Eucarida,
a recapitulation of an ancestral Marria. We can visualize our species
making its way through the water in a jerky or saltatory and more
or less irregular manner, like most of the crustaceans that have large
biramous swimming legs and short bodies.
   As none of the crustaceans here used for comparison, except the
nauplius and protozoaean stages of later crustaceans, possesses a
like development of the two large biramous swimming limbs, it
appears necessary to consider Marria not only as a member of a
new family, the Marriocaridae, but even of a distinct suborder of
the Entomostraca, the Marriocarida.

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