Brachiopods (from
Latin
brachium, arm + New Latin
-poda, foot) are a
small
phylum of
benthic invertebrates.
Also known as
lamp shells (or
lampshells), "
brachs" or
Brachiopoda, they are
sessile, two-valved,
marine animals with an
external
morphology
superficially resembling
bivalve to which
they are not closely related. Approximately 99 percent of all
brachiopod species are documented solely from the
fossil record.
Description
(poss overview here)
Name
The scientific name "brachiopod" is formed from the
Ancient Greek words βραχίων ("arm") and πούς
("foot"). They are often known as "lamp shells", since the curved
shells of the
class Rhynchonellida look rather like pottery
oil-lamps.
Distinguishing features
(to be completed)
Shells and their mechanisms
_01.png/100px-Brachiopod_valves_and_pedicle_(articulate)_01.png)
Modern brachiopods range from long,
and most species are about . Each has two valves (shell sections)
which are
biomineralized. The
brachial valve bears on its inner surface the brachia ("arms") from
which the phylum gets its name, and which supports the
lophophore, used for
filtering and
respiration. The other is known as the pedicle
valve, as its inner surface bears the stalk-like pedicle by which
most brachiopods attach themselves to surface. The brachial and
pedicle valves are often call the
dorsal
("upper") and ventral ("lower"), but some
paleontologists regard "dorsal" and "ventral"
as incorrect terms, since they believe that the "ventral" valve was
formed by folding of the upper surface under the body. Irrespective
of this debate, the valves of brachiopods are differently arranged
of those of
bivalve molluscs, which lie on the left and right sides of
the body. In most brachiopod species both valves are convex, the
surfaces often bear growth lines or other ornaments, and the
pedicle valve is larger than the brachial. However, the
linguids, which burrow into the seabed, have valves
that are smoother, flatter and of similar size and shape.
Brachiopod valves have a
hinge, in which the
rearmost end of the brachial valve rocks on an internal projection
of the pedicle valve. The major classification of brachiopods is
determined by the form of the hinges. The internal projections of
articulate ("jointed") brachiopods have teeth which fit into
sockets on the brachial valve, an arrangement that locks the valves
together. Inarticulate brachiopods have no matching teeth and
sockets, and their valves are held together only by muscles.
All brachiopods have adductor muscles, that are set on the inside
of the pedicle valve and close the valves by pulling on the part of
the brachial valve ahead of the hinge. These muscles have both
"quick" fibers that close the valves in emergencies and "catch"
fibers that are slower but can keep the valves closed for long
periods. Articulate brachiopods open the valves by means of
abductor muscles, also known as diductors, which lay further to the
rear and pull on the part of the brachial valve behind the hinge.
Inarticulate brachiopods use a different opening mechanism, in
which muscles reduce the length of the
coelom
(main body cavity) and make it bulge outwards, pushing the valves
apart. Both
classes open the valves
to about 10°. The more complex set of muscles employed by
inarticulate brachiopods can also operate the valves as scissors, a
mechanism that linguids use to burrow.
Each valve consists of three layers, a outer
periostracum made of
organic compounds and two
biomineralized layers. Articulated
brachiopods have a periostracum made of
proteins, a "primary layer" of
calcite (a form of
calcium carbonate under that, and finally
a mixture of proteins and calcite. Inarticulate's shells have a
similar sequence of layers, but their composition is different from
that articulated brachiopods and also varies between the
classes of inarticulate brachiopods.
Linguids and discinids, which have pedicles, have a
matrix of
glycosaminoglycans (long, unbranched
polysaccharides), in which other
material are embedded:
chitin in the
periostracum;
apatite containing
calcium phosphate in the primary
biomineralized layer; and a complex mixture in the innermost layer,
containing
collagen and other proteins,
chitinophosphate and apatite.
Craniids,
which have no pedicle and cement themselves directly hard surfaces,
have a periostracum of
chitin and mineralized
layers of calcite.
Mantle
Like
molluscs, brachiopods have a mantle, an
epithelium that lines the shell and
encloses the internal organs. The brachiopod body occupies only
about one-third of the internal space inside the shell, nearest the
hinge. The rest of the space is lined with the mantle
lobes, extensions that enclose a water-filled
space in which sits the lophophore. The
coelom (main body cavity) extends into each lobe as a
network of canals, which carry nutrients to the edges of the
mantle.
Relatively new cells in a groove on the edges of the mantle secrete
material that extends the periostracum. These cells are gradually
displaced to the upper side of the mantle by more recent cells in
the groove, and switch to secreting the mineralized material of the
shell valves. In other words, on the edge of the valve the
periostracum is extended first, and then reinforced by extension of
the mineralized layers under the periostracum. In most species the
edge of the mantle also bears movable bristles, often called
chaetae or
setae, that
may help defend the animals and may act as
sensors. In some brachiopods groups of chaetae help
to channel the flow of water into and out of the mantle
cavity.
In most brachiopods,
diverticula
(hollow extensions) of the mantle penetrate through the mineralized
layers of the valves into the periostraca. The function of these
diverticula is uncertain and it is suggested that they may be
storage chambers for chemicals such as
glycogen, may
secrete
repellents to deter organisms that stick to the shell or may help
in
respiration. Experiments show that a
brachiopod's
oxygen consumption drops if
petroleum jelly is smeared on the
shell, clogging the diverticula. The body excluding lophophore and
mantle cavity account for about 25% of the internal space among
articulate species with diverticula, which are majority, but about
60% among articulate species that have no diverticula accounts.
This suggests that the lophophore is a severe constraint on the
body mass of brachiopods, and that diverticula provide extra living
space.
Lophophore
Like
bryozoans and
phoronids, brachiopods have a lophophore, a crown
of tentacles whose
cilia (fine hairs) create a
water current that enables them to
filter food particles out of the water.
However a bryozoan or phoronid lophophore is a ring of tentacles
mounted on a single, retracted stalk, while the basic form of the
brachiopod lophophore is U-shaped, forming the brachia ("arms")
from which the phylum gets its name. Brachiopod lophophores are
non-retractable and occupy the frontmost two-thirds of the internal
space, where the valves gape when opened. To provide enough
filtering capacity in this restricted space, lophophores of larger
brachiopods are folded in moderately to very complex shapes –
loops and coils are common, and some species' lophophores resemble
a hand with the fingers splayed. In all species the lophophore is
supported by
cartilage and by a
hydrostatic skeleton (in other words by
the pressure of its internal fluid), and the fluid extends into the
tentacles. Some articulate brachiopods also have a pair of
brachidia, calcareous struts suspended on the inside of the
brachial valve and shaped similarly to the lophophore that it
supports.
The tentacles bear
cilia (fine mobile hairs)
on their edges and along the center. The beating of the outer cilia
drives a water current from the tips of the tentacles to their
bases, where it exits. Food particles that collide with the
tentacles are trapped by
mucus, and the cillia
down the middle drive this mixture to their bases. A brachial
groove runs rounds the bases of the tentacles, and its own cilia
pass food along the groove towards the mouth. The method used by
brachiopod is known as "upstream collecting", as food particles are
captured as they enter the field of cilia that creates the feeding
current. This method is used by the related
phoronids and
bryozoans,
and also by
pterobranchs.
Entoprocts use a similar-looking crown of
tentacles, but theirs are solid and the flow runs from bases to
tips, forming a "downstream collecting" system that catches food
particles as they are about to exit.
Attachment to substrate
Most modern species attach to hard
surfaces by means of a cylindrical pedicle ("stalk"), an extension
of the body wall. This has a chitinous
cuticle (non-cellular "skin") and protrudes through
a opening in the hinge. However, some
genera
such as the inarticulate
Crania and the articulate
Lacazella have no pedicle, and cement the rear of the
"pedicle" valve to a surface so that the front is slightly inclined
up away from the surface. In a few articulate genera such as
Neothyris and
Anakinetica, the pedicles wither as the
adults grow, and they finally lie loosely on the surface. In these
genera the shells are thickened and shaped so that the opening of
the gaping valves is kept free of the sediment.
Pedicles of inarticulate species are extensions of the main coelom,
which houses the internal organs. A layer of longitudinal muscles
lines the
epidermis of the pedicle.
Members of the
order Lingulida have long
pedicles, which they use to burrow into soft surfaces, to raise the
shells to the opening of the burrow to feed,and to retract them
when disturbed. A lingulid moves its body up and down the top
two-thirds of the burrow, while the remaining third is occupied
only by the pedicle, with a bulb on the end that builds a
"concrete" anchor. However, the pedicles of the order Discinida are
short and attach to hard surfaces.
An articulate pedicle has no coelom, is constructed from a
different part of the
larval body, and has a
core composed of
connective
tissue. Muscles at the rear of the body can straighten, bend or
even rotate the pedicle. The far end of the pedicle generally has
rootlike extensions or short papillae ("bumps"), which attach to
hard surfaces. However, articulate brachiopods of genus
Chlidonophora use a branched pedicle to anchor in
sediment. The pedicle emerges from the pedicle
valve, either through a notch in the hinge or, in species where the
pedicle valve is longer than the brachial, from a hole where the
pedicle valve doubles back to touch the brachial valve. Some
species stand with the front end upwards, while others lie
horizontal with the pedicle valve uppermost.
Feeding and excretion
The water flow enters the lophophore from the sides of the open
valves, and exits at the front of the animal. In linguids the
entrance and exit channels are formed by groups of chaetae that
function as funnels. In other brachiopods the entry and exit
channels are organized by the shape of the lophophore. The
lophophore captures food particles, especially
phytoplankton (tiny
photosynthetic organisms), and deliver them
to the mouth via the brachial grooves along the bases of the
tentacles. The cilia of the lophophore can change direction to
eject isolated partciles of indigestible matter. If the animal
encounters larger lumps of undesired matter, the cilia lining the
entry channels pause and the tentacles in contact with the lumps
move apart to form large gaps and then slowly use their cilia to
dump the lumps on to the lining of the mantle. This has its own
cilia, which wash the lumps out through the gape between the
valves. If the lophophore is clogged, the adductors snapped the
valves sharply, which creates a "sneeze" that clears the
obstructions.
The mouth is at the base of the lophophore. Food passes through the
mouth, muscular
pharynx ("throat") and
oesophagus ("gullet"), all of which are
lined with cilia and cells that secrete
mucus
and digestive
enzymes. The
stomach wall has branched
ceca
("pouches") where food is digested, mainly within the cells.
Nutrients are transported throughout the coelom, include the
mantles lobes, by cilia. The wastes produced by
metabolism are broken into
ammonia, which is eliminated by
diffusion through the mantle and lophophore.
Brachiopods have
metanephridia, used
by many
phyla to excrete ammonia and other
dissolved wastes. However, brachiopods have no sign of the
podocytes which perform the first phase of
excretion in this process, and brachiopod metanephridia appear to
be used only to emit
sperm and
ova.
The majority of brachiopods' food is digestible, with very little
solid waste to be removed. Some inarticulate brachiopods have a
U-shaped digestive tract ending with an anus that eliminates solids
from the front of the body wall. Other inarticulate brachiopods and
all articulate brachiopods have a curved gut that ends blindly,
with no anus. These animals bundle solid waste with mucus and
periodically "sneeze" it out, using sharp contractions of the gut
muscles.
Circulation and respiration
The lophophore and mantle are the only surfaces that absorb
oxygen and eliminate
carbon dioxide. Oxygen seems to be
distributed by the fluid of the coelom, which is circulated through
the mantle and driven either by contractions of the lining of the
coelom or by beating of its cilia. In some species oxygen is partly
carried by the
respiratory
pigment hemerythrin, which is
transported in coelomocyte cells.
Brachipods also have colorless
blood,
circulated by a muscular heart which lies in the dorsal part of the
body above the stomach. The blood passes through vessels that
extend to the front and back of the body, and branch to organs
including the lophophore at the front and the gut, muscles, gonads
and nephridia at the rear. The blood circulation seems not to be
completely closed, and the coelomic and blood fluids must mix to a
degree. The main function of the blood may be to deliver
nutrients.
Nervous system and senses
The "brain" of adult articulates consists of two
ganglia, one above and the other below the
oesophagus. Adult inarticulates have only the
lower ganglion. From the ganglia and the
commissures where they join, nerves run to the
lophophore, the mantle lobes and the muscles that operate the
valves. The edge of the mantle has probably the greatest
concentration of sensors. Although not directly connected to
sensory neurons, the mantle's
chaetae probably send
tactile signals to receptors in the
epidermis of the mantle. Many brachiopods close
their valves if shadows appear above them, but the cells
responsible for this are unknown. Some brachiopods have
statocysts which detect changes in the animals'
balance.
Reproduction and lifecycle
Lifespans range from from 3 to over 30 years. Adults of most
species are of one sex throughout their lives. The
gonads are masses of developing
gametes (
ova or
sperm), and most species have four gonads, two in each
valve. Those of articulates lie in the channels of the mantle
lobes, while those of inarticulates lie near the gut. Ripe gametes
float into the main coelom and then exit into the mantle cavity via
the
metanephridia, which open on
either side of the mouth. Most species release both ova and sperm
into the water, but females of some species keep the
embryos in brood chambers until the larvae
hatch.
The
cell division in the embryo is
radial (forms stacks of rings directly above each other),
holoblastic (cells are separate, although adjoining) and regulative
(the type of tissue into which a cell develops is controlled by
interactions between adjacent cells, rather than rigidly within in
each cell). While some animals develop the mouth and
anus by deepening the
blastopore, a "dent" in the surface of the early
embryo, the blastopore of brachiopods closes up, and their mouth
and anus develop from new openings.
The
larvae of inarticulates swim as
plankton for months, and are miniature adults, with
valves, mantle lobes, a pedicle that coils in the mantle cavity,
and a miniature lophophore, which is used for both feeding and
swimming – except that
Craniids have no
pedicle. As the shell becomes heavier, the juvenile sinks to the
bottom and becomes a sessile adult. The larvae of an articulate
species live only on
yolk, and remain only
among the plankton for only a few days. This type of larva has a
ciliated frontmost lobe that becomes the body
and lophophore, a rear lobe that becomes the pedicle, and a mantle
like a skirt, with the hem towards the rear. On
metamorphosing into an adult, the pedicle
attaches to a surface, the front lobe develops the lophophore and
other organs, and the mantle rolls up over the front lobe and
starts to
secrete the shell.
Brachiopods' maximum oxygen consumption is low, and their minimal
is not measurable. In cold seas, brachiopod growth is seasonal and
the animals often lose weight in winter. These variations in growth
often form growth lines in the shells. Members of some
genera have survived for a year in aquaria without
food.
Taxonomy
In addition the "traditional" classification, defined in 1869, two
further approaches were established in the 1990s:
- In the "traditional" classification, the Articulata have
toothed hinges between the valves, while the hinges of the
Inarticulata are held together only by muscles.
- In another approach, based on the materials of which the shells
are based, the Craniida and the traditional
the "articulate" group are united in the Calciata, having calcite
shells, while the Lingulida and Discinida, combined in the Lingulata, have shells made of chitin and calcium
phosphate.
- A three-part scheme places the Craniida in a group separate of
its own, the Craniformea. The Lingulida
and Discinida are grouped as Linguliformea, and the Rhynchonellida and
Terebratulida as Rhynchonelliformea.
Classifications of brachiopods
| "Traditional"
classification |
Inarticulata |
Articulata |
| "Calciata" approach |
Lingulata |
Calciata |
| Three-part approach |
Linguliformea |
Craniformea |
Rhynchonelliformea |
| Orders |
Lingulida |
Discinida |
Craniida |
Terebratulida |
Rhynchonellida |
| Hinge |
No teeth |
Teeth and sockets |
| Anus |
On front of body, at end of U-shaped gut |
None |
| Pedicle |
Contains coelom with muscles
running through |
No pedicle |
No coelom, muscles where joins body |
| Long, burrows |
Short, attached to hard surfaces |
None, cemented to surface |
Short, attached to hard surfaces |
| Periostracum |
Glycosaminoglycans and chitin |
Chitin |
Proteins |
| Primary (middle) mineralized
layer of shell |
Glycosaminoglycans and apatite (calcium phosphate) |
Calcite (a form of calcium carbonate) |
| Inner mineralized layer of shell |
Collagen and other
proteins, chitinophosphate and apatite (calcium phosphate) |
Calcite |
Proteins and calcite |
| Chetae around opening of shells |
Yes |
No |
Yes |
| Coelom fully divided |
Yes |
No |
Yes |
About 330 living species are recognized, grouped into over
100
genera. The great majority of modern
brachiopods are rhynchonelliforms (Articulata excluding
Craniida).
Ecology
Distribution and habitat
Brachiopods live only in the sea. Most species avoid locations with
strong currents or waves, and typical sites include rocky
overhangs, crevices and caves, steep slopes of
continental shelves, and in the bottoms of
deep oceans. However, some articulate species attach to
kelp, and in exceptionally sheltered sites in
intertidal zones. The smallest living
brachiopod,
Gwynia, is only about
long, and lives between gaps in
gravel.
Rhynchonelliforms (Articulata excluding Craniida), whose larvae
live only their yolks and settle quickly, specialize in
specific areas and form dense populations that can
reach thousands per
meter, and young adults
often attach to the shells of more mature ones. One other hand
inarticulate brachipods, whose larva swim for up to a month before
settling, have wide ranges and members of the genus discinoid
Pelagodiscus are found all
over the seas.
Interactions with other organisms
Brachiopods'
metabolisms are 3 to
10 times slower than those of
bivalves.
While brachiopods were abundant in warm, shallow seas during the
Cretaceous period, they have been out-bred by
bivalves, and now live mainly in cold and low-light
conditions.
Brachiopod shells occasionally show evidence that they have
suffered and sometimes repaired damage caused by predators. Fish
and crustaceans seem to find brachiopod flesh distasteful. The
fossil record shows that drilling predators like
gastropods attacked
molluscs and
echinoids 10 to
20 times more often than they do brachiopods, and suggests
that such predators attacked brachiopods by mistake and/or only
when other prey was scarce.
In waters where food is scarce, the snail
Capulus ungaricus steals food from
bivalves, snails, tube worms, and brachiopods.
Among brachiopods only the lingulids have been fished commercially,
on a very small scale.
Evolutionary history
Fossil record
Lingulata
Obolellida
Strophomenida
Orthodida
Pentamerida
Rhynchonellida
Spiriferida
Terebratulida
Over 12,000 fossil species are recognized, grouped into over
5,000
genera. While the largest modern
brachiopods are long, a few fossils measure up to wide. The
earliest confirmed brachiopods have been found the early
Cambrian, with the hingeless, inarticulate forms
appearing first, followed soon after by the hinged, articulate
forms. Three unmineralized species have also been found in the
Cambrian, and apparently represent two distinct groups that evolved
from mineralized ancestors. The inarticulate
Lingula is often called a "
living fossil", as very similar
genera have been all the way back to the Ordovician.
On the other hand, articulate brachiopods have produced major
diversifications, and severe
mass
extinctions – but the articulate Rhynchonellida and
Terebratulida, the most diverse present-day groups, appeared at the
start of the Ordovician and Carboniferous respectively.
At their peak in the
Paleozoic the
brachiopods were among the most abundant filter-feeders and
reef-builders, and occupied other
ecological niches, including swimming in
the jet-propulsion style of
scallops.
However, after the
Permian–Triassic
extinction event, informally known as the "Great Dying",
brachiopods recovered only a third of their former diversity. They
were still quite diverse and adundant in the Jurassic and
Cretaceous, but have slowly declined.
Scientists have found that brachiopod fossils have been useful
indicators of climate changes during the
Paleozoic era. When global temperatures were low,
as in much of the
Ordovician, the large
range of temperatures between equator and the polar created
different collections of fossils at different
latitudes. On the other hand, warmer periods, such
much of the
Silurian, created smaller
ranges of temperatures, and the low to midde latitudes had only a
few brachiopod species that lived in all the warmer seas.
Brachiopods are extremely common fossils throughout the
Paleozoic. The major shift came with the
Permian extinction. Before
this
extinction event, brachiopods
were more numerous and diverse than bivalve mollusks. Afterwards,
in the
Mesozoic, their diversity and
numbers were drastically reduced and they were largely replaced by
bivalve mollusks. Mollusks continue to dominate today, and the
remaining orders of brachiopods survive largely in fringe
environments.
The origin of the brachiopods is unclear; two hypotheses suggest
how a bivalved lifestyle could have emerged.
The most abundant modern brachiopods are the Class
Terebratulida. The perceived resemblance of
terebratulid shells to ancient oil lamps gave the brachiopods their
common name "lamp shell". The phylum most closely related to
Brachiopoda is probably the small phylum
Phoronida (known as "horseshoe worms"). Along with
the
Bryozoa and possibly the
Entoprocta, these phyla constitute the informal
superphylum
Lophophorata.
The brachiopods evolved in the lower Cambrian, and became
particularly numerous in shallow water habitats during the
Ordovician & Silurian, in some cases forming whole banks in
much the same way as bivalves (such as
mussels) do today. In some places, large sections of
limestone strata
and reef deposits are composed largely of their shells.
Throughout their long geological history, the brachiopods have gone
through several major proliferations and diversifications, and have
also suffered from major
extinctions.
It has been suggested that the slow decline of the brachiopods over
the last 100 million years or so is a direct result of (1) the rise
in diversity of filter feeding bivalves, which have ousted the
brachiopods from their former habitats; (2) the increasing
disturbance of sediments by roving deposit feeders (including many
burrowing bivalves); and/or (3) the increased intensity and variety
of shell-crushing predation. However, a famous paper by Stephen Jay
Gould suggested that the rise in bivalves which accompanied the
downfall of the brachiopods was nothing more than coincidence - the
two lineages were like "ships that pass in the night". The greatest
successes for the bivalves have been in habitats that have never
been adopted by the brachiopods, such as burrowing.
The abundance, diversity, and rapid evolution of brachiopods during
the Paleozoic make them useful as
index
fossils when correlating strata across large areas.
Classification
In older classification schemes, Phylum Brachiopoda was divided
into two classes: Articulata and Inarticulata. Since most orders of
brachiopods have been extinct since the end of the Paleozoic Era,
classifications have always relied extensively on the morphology
(that is, the shape) of
fossils. In the last
40 years further analysis of the fossil record and of living
brachiopods, including
genetic study, has
led to changes in
taxonomy.
The taxonomy is still unstable, however, so different authors have
made different groupings. This article follows Williams, Carlson
& Brunton (2000), who subdivide Brachiopoda into three
subphyla, eight classes, and 26 orders. These categories are
believed to be approximately
monophyletic. Brachiopod diversity declined
significantly at the end of the Paleozoic. Only five orders in
three classes include forms that survive today, a total of between
300 and 500 extant species. In their zenith during the mid-Silurian
Period, 16 orders of brachiopods coexisted.
Extant taxa in green, extinct taxa in grey
after Williams, Carlson, and Brunton, 2000
Comparison with bivalves
While brachiopods superficially resemble bivalve molluscs, the
similarities are purely a product of
convergent evolution; brachiopods and
bivalves belong to different phyla and thus differ markedly.
Bivalves usually have a plane of symmetry
between the valves of the shell, which are mirror images of each
other; most brachiopods have a plane of
bilateral symmetry
through the valves and perpendicular to the
hinge. The two brachiopod valves differ in shape and
size from one another. Bivalves use
adductor muscles to hold their two valves
closed, and they open them by means of an external or internal
ligament once the adductor muscles are
relaxed. Brachiopods use internal
diductor
muscles to pull their two valves apart; they close the two with
adductor muscles.
Furthermore, brachiopod shells are made of different minerals.
While bivalves construct their shells from aragonite, Linguliformea
use
apatite, and the Rhynchonelliformea and
Craniiformea produce calcite shells.
Gallery
Image:Onniella.jpg|Brachiopod fossils are often found in dense
assemblages, such as these specimens of the
Ordovician species
Dalmanella
meeki.Image:Brachiopoda-morphology.png|Brachiopod
morphologyImage:Brachiopod Neospirifer.jpg|A
Carboniferous brachiopod
Neospirifer
condor, from Bolivia. The specimen is 7 cm
across.Image:Rhynchotremadentatum.jpg|
Rhynchotrema
dentatum, a rhynchonellid brachiopod from the Cincinnatian
(Upper
Ordovician) of southeastern
Indiana.Image:HederellaOH3.jpg|A
Devonian
spiriferid brachiopod from Ohio that served as a host substrate for
a colony of
hederellids. The specimen is
5 cm wide.
Image:Syringothyris01.JPG|Syringothyris
sp.; a spiriferid brachiopod from the Logan Formation (Lower
Carboniferous) of Wooster, Ohio
(internal
molds).Image:PetrocraniaOrdovician.jpg|
Petrocrania
brachiopods attached to a strophomenid brachiopod; Upper Ordovician
of southeastern Indiana.Image:LingulaanatinaAA.JPG|
Lingula
anatina from Stradbroke Island, Australia.
References
- Part H of
- MLF (Moore, Lalicker and Fischer); Invertebrate Fossils,
McGraw-Hill Book, 1952
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