Lambeosaurus
Name:
Lambeosaurus
(Lambe’s lizard - after the palaeontologist Lawrence Morris
Lambe).
Phonetic: Lam-be-o-sore-us.
Named By: William Parks - 1923.
Synonyms: Corythosaurus frontalis,
Didanodon, Procheneosaurus praeceps, Tetragonosaurus.
Classification: Chordata, Reptilia, Dinosauria,
Ornithischia, Ornithopoda, Hadrosauridae, Lambeosaurinae,
Lambeosaurini.
Species: L. lambei (type),
L. magnicristatus. Possibly also L.
paucidens, though this species is not accepted by all.
Diet: Herbivore.
Size: Around 9 to 9.5 meters long.
Known locations: Canada - Alberta. USA -
Montana. Possibly also Baja California.
Time period: Campanian of the Cretaceous.
Fossil representation: Multiple specimens including
some juveniles.
Lambeosaurus
the dinosaur
Lambeosaurus
is one of the hadrosaurs
that is frequently depicted in dinosaur books
and toys, and study of this genus is required learning for anyone who
wishes to know more about the hadrosaurs in general.
Lambeosaurus
is best known from Canada and upper Montana USA, although other
attributed fossils in the past have suggested that Lambeosaurus
had a
significantly broader range. The most distinctive feature of
Lambeosaurus is the crest which is often described
as being either
hatchet or axe shaped, the broader forward portion being the blade
while the thin rearward projection is the handle. This rear
projection is solid; however the forward portion is hollow with a
network of passages inside (a signature feature of the lambeosaurine
hadrosaurids).
The
function of the crest is one of the most often talked about areas of
the body. One explanation is that the crest was used as either a
snorkel or an air chamber for trapping a supply of breathable air so
that Lambeosaurus could hold their heads underwater
for extended
periods. This however would require Lambeosaurus
to regularly be
active within bodies of water, and it does not explain the variance
in form of head crests between Lambeosaurus and
other lambeosaurine
genera.
One
exciting theory is that the crests allowed for the storage of salt
glands, special organs that allow excess salt from the environments
to be excreted. However the presence of salt glands is usually
associated with animals that live in marine (saltwater) ecosystems
which have higher levels of salts, thus necessitating the presence of
salt glands. This is not actually that much of a stretch to believe
however since during the late Cretaceous most of central North America
was submerged by a shallow sea called the Western Interior Seaway
that ran North to South from what is now Upper Canada into the Gulf of
Mexico. The areas that Lambeosaurus remains are
known from have been
interpreted as being marshes and swamps that were in close proximity to
the coastline of the Western Interior Sea. Additionally a 1979
paper by palaeontologist Jack R. Horner described what appeared to
be Lambeosaurus jaws (L.
magnicristatus) from marine sediment.
The problems with this theory however is that it is that with this
evidence it is only relevant to Lambeosaurus,
with many other
hadrosaurs being known from different ecosystems. Additionally this
does not explain the difference in crest form between not only
hadrosaur genera, but the two main Lambeosaurus
species.
The
only theory that explains the different crest forms is that of
display. Firstly different species of Lambeosaurus
would be able to
tell each other apart by the different form of head crest, as well as
any hadrosaurid other genera that were active in the same locations as
they were. Additionally the crests of adult Lambeosaurus
were more
developed than juveniles which indicates that they were also a sign of
maturity. Specimens thought to be females also have more rounded
crests than the males.
Another
factor concerning display is that of sound. The forward portion of
the crest is hollow with a network of tubes, and assuming this is not
just a weight saving feature to reduce stress on the head and neck,
this may have formed a resonating chamber for amplifying the calls.
Not only have studies continually revisited this area, but different
crest variations between species should allow for different sounding
calls. Study in one specimen of the related Corythosaurus
also
suggests that lambeosaurine hadrosaurids in particular had very good
hearing, further supporting the auditory hypothesis for the crest.
Size
estimates for Lambeosaurus can vary greatly
depending upon source
because of the large amounts of fossil remains that have been
attributed to the genus. The confirmed Lambeosaurus
remains that are
known from Alberta Canada and Montana, USA point to individuals
around the nine to nine and a half meter mark for total length. Upper
estimates of fifteen meters long still exist in some sources however,
though this estimate is based upon material that is no longer
attributed to the Lambeosaurus genus. This
stems back to the
description of a dubious species of Lambeosaurus
in 1981 called
L. laticaudus from fossils found in Baja
California. The
Lambeosaurus connection however could never be
confirmed since the
crest is missing. In 2012 these remains were re-established as a
new genus called Magnapaulia.
As
with all hadrosaurids, Lambeosaurus seems to have
been primarily
quadrupedal with the ability to balance and possibly walk on just the
rear legs when it had to. Out of the original five digits of the
fore-arm hand, the first digit is missing, lost through selective
evolutionary factors. Digits two, three and four are developed into
weight bearing hooves, and when combined with footprints of other
hadrosaurids, confirms the idea that Lambeosaurus,
and other
hadrosaurids, were mostly bipedal. The fifth digit is free from the
others and may have been to help grip and/or balance when the body
weight was shifted forward.
By
being both quadrupedal and occasionally bipedal, Lambeosaurus
could
browse upon anything from low to moderately high growing vegetation.
The anterior portion of the mouth however is narrower than in many
other hadrosaurids, something that suggests that Lambeosaurus
were
more selective in their browsing habits. Once food was removed from
the main plant, it was then processed by the grinding teeth that were
arranged in batteries at the back of the mouth.
Lambeosaurus
possibly shared its habitat with other genera of hadrosaur such as
Corythosaurus, though this genus is currently
known from slightly
older Campanian deposits, which indicates that Lambeosaurus
may have
actually replaced Corythosaurus. Other dinosaurs
roughly active
around that time and locale include the ceratopsians
Chasmosaurus
and
Centrosaurus,
the nodosaur Edmontonia
as well as the ankylosaur
Euoplocephalus.
However the exact relationships between these
different dinosaurs is still being established since some such as
ankylosaurs seem to have been better adapted to dryer more arid
environments due to the arrangements of their nasal passages.
Predators of Lambeosaurus may have included
Campanian era tyrannosaurs
such as Albertosaurus
and Daspletosaurus.
Classification history of
Lambeosaurus
The
history of Lambeosaurus is one that is steeped in
the misinterpretation
of dinosaur fossils at a time when palaeontology as we know it today
was still in its infancy. The first Lambeosaurus
remains were
described by Lawrence Lambe in 1902, however these fossils were
only of partial post cranial remains, and rather than establish them
as a new genus, Lambe assigned them as a species of Trachodon,
T.
marginatus. The problem here is that Trachodon
has always been a
very dubious genus. Back in 1856 another palaeontologist named
Joseph Leidy created the Trachodon dinosaur genus
based only upon the
description of a collection of teeth. Today we now know this
description to be flawed since the teeth assigned to Trachodon
are
actually a combination of both hadrosaur and ceratopsian teeth, two
distantly related yet very different groups of dinosaurs. Leidy named
many genera of prehistoric animals many from only teeth and some like
Aublysodon
remain very dubious, while others have been cast down as
valid genera. But Leidy did achieve one very big success from only
describing teeth with his naming of Troodon
in 1856.
The
dubious nature of Trachodon seems to have still
been appreciated by
Lambe since when he described two new skulls in 1914 that he
thought belonged to T. marginatus he created the
genus
Stephanosaurus. The problem here is the same as
many extinct animals
that have their initial descriptions based upon very incomplete
remains. The fossils originally described as T. marginatus
were of
the post cranial skeleton with no elements of the skull. The original
concept of the skulls being placed with this material is based around
the fact that the skulls came from roughly the same area as the T.
marginatus fossils. This makes the assumptions that they
belong to
the same genus possible, but one that is impossible to establish
without a set of remains that bridge the gaps between both groups of
fossils (i.e., skull and post cranial fossils of one individual
that can be compared to existing fossils assigned to the genus).
This is why in 1923 William parks removed the skulls from
Stephanosaurus (today regarded as a dubious
genus) and redescribed
them as a new genus, Lambeosaurus, in honour of
Lawrence Lambe who
had died four years earlier in 1919.
For
many years Lambeosaurus (including its earlier
association with
Stephanosaurus) was not known to have very many
fossils. Today
however we now know that that was never the case, further
Lambeosaurus were actually being discovered in the
early years of the
twentieth century. In 1917 a new dinosaur called Cheneosaurus
was
named by Lawrence Lambe, a dinosaur that would become the type genus
of the Cheneosaurinae, a group of dinosaurs that resembled
hadrosaurs, but were much smaller.
Before
this in 1902, Henry Fairfield Osborn named a genus Didanodon
altidens based upon a partial left jaw. Lambe later
re-classed this
specimen as a species of Trachodon, T.
altidens. In 1920
William Diller Matthew took a photograph of the skeletal remains of
one such dinosaur and named it Procheneosaurus;
however this is not
the usual method for establishing a new genus. When William parks
described the genus Tetragonosaurus from other
fossils recovered from
the Dinosaur Park Formation, he also included the fossils of
Procheneosaurus into the type species of Tetragonosaurus,
T.
praeceps (A second species of T. erectofrons
was
established for
smaller specimens). The Tetragonosaurus genus
would grow further
with the addition of T. cranibrevis by Charles
M. Sternberg in
1935.
However,
nearly forty years’ worth of classification was turned on its head
in 1942 when Richard Swann Lull and Nelda Wright released a
detailed study about these and associated dinosaurs. In this study
they declared that the whole Tetragonosaurus genus
should actually be
called Procheneosaurus, as well as possibly Trachodon
altidens too.
The really ground breaking discovery however would come in 1975
when Peter Dodson demonstrated that the cheneosaurs were actually made
up of the juveniles of the larger hadrosaurs. Specifically the type
specimen of what was now Procheneosaurus was seen
to now be a juvenile
Lambeosaurus, while other specimens were probably
juveniles of
Corythosaurus.
The
problem here is that technically Procheneosaurus
was named before
Lambeosaurus, and usually the older name takes
precedence over any
future naming. Despite this Lambeosaurus is still
credited as being
the specific genus for these remains with Procheneosaurus
being treated
as a synonym. Another case of a dinosaur retaining a second name
despite having fossils attributed to an earlier description of another
genus is that of Tyrannosaurus.
Today
Lambeosaurus is best known for being the type genus
of the
Lambeosaurinae, one of the two largest groups of hadrosaurs.
Members of this group, referred to as lambeosaurines, all exhibit
hollow head crests, though the physical form of the crest can vary
greatly between different genera. Other lambeosaurine genera closely
related to Lambeosaurus include Olorotitan,
Corythosaurus and
Hypacrosaurus.
Corythosaurus in particular is very similar in
physical form to Lambeosaurus, so much so that
the only obvious
differences between them is the shape and form of the crest and how it
attaches to the skull.
There
were once seven species of Lambeosaurus, but at
the time of writing
only the type species L. lambei and L.
magnicristatus are
universally considered to be valid. Both of these species are known
from upper North America and can be distinguished on the basis of
different crest form. L. lambei has a rear bony
projection that is
roughly the same length as the forward crest, while L.
magnicristatus has a reduced bony projection and a slightly
enlarged
forward crest. Another species called L. paucidens
is only known
from post cranial remains so it is hard to be certain how or even if it
is related to the other two Lambeosaurus species.
With this in mind,
many palaeontologists consider these remains to instead be a species
of Hadrosaurus
(H. paucidens).
Other past species have since
been established to be different sexes of existing hadrosaur genera,
while others (such as L. laticaudus stated
above) are now
different genera.
Further reading
- Corythosaurus intermedius, a new species of
trachodont dinosaur,
William A. Parks - 1923.
- A new genus and two new species of trachodont dinosaurs from the
Belly River Formation of Alberta, William A. Parks - 1931.
- New species of trachodont dinosaurs from the Cretaceous formations
of Alberta, William A. Parks - 1931.
- Taxonomic implications of relative growth in lambeosaurine
dinosaurs, Peter Dodson - 1975.
- Upper Cretaceous dinosaurs from the Bearpaw Shale (marine) of
south-central Montana with a checklist of Upper Cretaceous dinosaur
remains from marine sediments in North America, Jack R. Horner -
1979.
- A new species of hadrosaurian dinosaur from the Upper Cretaceous of
Baja California: ?Lambeosaurus laticaudus,
William J. Morris -
1981.
- Acoustic analyses of potential vocalization in lambeosaurine
dinosaurs, David B. Weishampel - 1981.
- Anatomy and relationships of Lambeosaurus magnicristatus,
a
crested hadrosaurid dinosaur (Ornithischia) from the Dinosaur Park
Formation, Alberta, David C. Evans & Robert R. Reisz
- 2007.
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