-
110
extremely large, and the occipital region of the skull is
raised.
These head muscles, the sterno and cleidomastoid, must have
been
powerful and provided the force behind the teeth. The sabres
them
selves form excellert slicing blades, and the whole mechanism is
a
better method of piercing a thick hide than in the "normal"
method
of lion or leopard.
Another view has been put forward by Bohlin (1940, 1947) who
argued that the canincs were too slim and fragile to be used to
kill
at all, and these animals were entirely carrion-eating. He
adds
that in making the killing bite, the head would have to come so
far
back that tne line of vision would be obscured, and the teeth
easily
broken by stabbing on to bone. A number of point3 are against
this
hypothesis. Firstly, it is unlikely that a carnivore of any
great
size can subsist by scavenging alone, as recent, work has
shown
(Schaller 1972), the number of carcasscs they may have come
across could
not have been that many. Usually the primary predator consumes
most
of the meat and what is left is finished off by hyaenas.
Hyaenas,
contrary to popular belief, are not solely carrion-eaters, and
they
are successful pack-hunters (Van Lawick - Goodall 1970).
Secondly,
a hyaena's dentition is adapted to dealing with the tough
remains of
a carcass, such as tendons, cartilage, bone; the pre-molars are
sturdy
and conical and the carnassials are not the narrow slicing
structures
of the ma, haerodont?. The latter, with the reduced pre-molars
and
scissor-l’ke carnassials could only have eaten the choice meat
of
freshly killed prey.
It is peculiar thut even among the earlier forms, the highly
specialized end lines (such as Kusmilus. Hoplophoneus and
Sansano-
smilus) have carnassials much better adapted for a carnivorous
diet
-
Ill
than have the modern cats, which have had an equally long
evolutionary
history in which to achieve the same thing. It is suggested here
that
because of the weak temporalis and masseter muscles, the lower
jaw
of the machaerodonts could not have exerted a strong pressure in
chew
ing. To compensate for this, the molars became more important,
which
resulted in reduction of pre-molars and more blade-like
carnassials.
Little pressure is needed to cut something with sharp scissors
whereas
more pressure is necessary when using blunt scissors. The living
cats
do not have t) s problem as the jaw muscles are powerful. In
fact,
lion, leopard and tiger readily scavenge (Turnbull - Kemp 1972).
In
one survey sixteen per centum of a lion's food was found to
bo
obtained from carrion, and they are even known to drive hyaenas
away
froi the pack's kill (Schaller 1972).
Matthew (1910) believes that the sabre-tooths tors at the
softer belly of the prey so that it bled to death. Churcher
(per. comm,
offers a more satisfactory idea; that they attacked the soft
under
side of the neck after gripping with the forjlimbs and claws.
The
throat is extremely vulnerable, and veins, nerves and trachea
can be
severed with one slash, and there is no bone to risk breaking
the
teeth. Moreover, leaping at the belly, there is the danger of
being
hit on the head by hooves. Lions usually bring the prey down
first by
grabbing with the fore paws, then biting the nape or throat.
(Schaller
1972). This could also be envisaged for Megantereon or Smilodon
whose
forequarters were massive and powerful.
The two types of Pleistocene sabre-tooths, the homotheriines
and the smilodontines were quite differently constructed which
suggests
that they each occupied a different ecological nich. Added to
this is
the fact that the fossils are nearly always found together in
the same
-
Ill
than have the modern cats, which have had an equally long
evolutionary
history in which to achieve the same thing. It is suggested here
that
because of the weak temporalis and masseter muscles, the lower
jaw
of the machaerodonts could not have exerted a strong pressure in
chew
ing. To compensate for this, the molars became more important,
which
resulted in reduction of pre-molars and more blade-like
carnassials.
Little pressure is needed to cut something with sharp scissors
whereas
more pressure is necessary when using blunt scissors. The living
cats
do not have this problem as the jaw muscles are powerful. In
fact,
lion, leopard and tiger readily scavenge (Turnbull - Kemp 1972).
In
one survey sixteen per centum of a lion's food was found to
be
obtained from carrion, and they are even known to drive hyaenas
away
from the pack's kill (Schaller 1972).
Matthew (1910) believes that the sabre-tooths tore at the
softer beily of the prey so that it bled to death. Churcher
(per. comm,
offers a more satisfactory idea; that they attacked the soft
under
side of the neck after gripping with the forelimbs and claws.
The
throat as extremely vulnerable, and veins, nerves and trachea
can be
severed with one slash, and there is no bone to risk breaking
the
teeth. Moreover, leaping at the belly, there is the danger of
being
hit on the head by hooves. Lions usually bring the prey down
first by
grabbing »ith the fore paws, then biting tho nape or throat.
(Schaller
1972). This) could also be envisaged for Megantereon or Smilodon
whose
forequarters were massive and powerful.
The two typeu of Pleistocene sabre-tooths, the homotheriines
and the smilodontineM were quite differently constructed which
suggests
that they each occupied a different ecological nich. Added to
this is
the fact that the fossils are nearly always found together in
the same
-
112
deposit, which means that they were compatible in the same aroa.
The
smiiodontines, with their short, stocky legs, shortened rather
inflex
ible lumbar region and heavier build were probably woodland
dwellers,
as they were obviously poor runnrrs. They probably leapt from
ambush
(Churcher per. comm.). The homotheriines were built more in
proport
ion with the modern lion or leopard, but still showed a tendency
for
strengthening of the forebody and shortening of the legs.
They
probably frequented the plains, were relatively faster runners
and
preyed upon the more light-limbed creatures, such as primitive
gazelles,
pigs and horses. In many cases, the bones of juvenile elephants
are
associated ,-ith Homotherium. suggesting that they preyed upon
these but
not the adults (Kurten 1968). In both types, the tails were
extremely
short, but +here are a variety of reasons for this.
The origin and spread of Dinofolis from the basic feline
stock
illustrates the repeated tendency among fossil cats for
machaerodontine
development. This genus did not, however, get very far
before
environmental conditions exterminated the entire group of
machaero
donts. That it was among the dominant carnivores during
Pleistocene
times in Africa seems to bo becoming more evident, and in fact
it
appears to have been much more widespread than originally
thought. It
is now known from India (a Pel i s cri stats) and America
(«Panthera
palaeonca).
In the Upper Pliocene, the genus Panthera makes its first
appearance. It was obviously better adapted for a cursorial
habit
and with the changing fauna, became the dominant feline
carnivore. It
is represented in the Transvaal caves (Ewer 1956°), in East
Africa
(Leaker 1967, Maglio 1972), and other Pleistocene deposits in
forms
not much different from today's.
With the increasing scarcity of the pachyderms, the
machaerodonts
-
113
became less abundant. The last remnants reach the height of
specialization and increased in size, probably because their
prey
became limited to even larger types.
4.3 The ph\logony of the Machacrodontinao
Most of the more ancient fossil cats are typified by enlarged,
sabre
like upper canines, and it was not until the late Pliocene that
cats
with "normal" canines made their appearance (Matthew 1910).
In
Matthew's opinion, the Tert1 -.ry and Quaternary sabre-too'*.hs
can be
derived from one of the specialized Oligocene sabre-tooths,
Hoplophoneus. The contemporary Dirictis which was less
specialized
led to the modern cats (Felinae) through Nimravus and
Pseudae1urus.
the sabres gradually getting shorter and more conical.
In a more general fashion, Teilhard and Leroy (1945) and
Piveteau (1948) divided the family Felidae into Palaeo-felids
(Oligo
cene) and Neo-felids (post Oligocene) in both of which there
are
machaerodontinoid and felinoid branches. The Palaeo-felids can
be
distinguished from the Neo-felids by possessing an alisphenoid
canal,
and distinctly separa+e carotid, posterior lacerate and
condylar
foramina, on the basicranium. In the younger Felidae, thp
alisphenoid
canal disappears, and the three foramina show an increasing
tendency to
uni te.
Simpsun (1945) agrees with Matthew in placing Pseudaelurus
ancestral to the Felinae, and the Nimravus not far from it. He
however
places all the machaerodontine cats (including the Oligocene
forms)
into tho sub-family Machaerodontinae. He considers Dinofeli s
belongs
to the Felinae.
lue derivation of the "false sabre-tooths" is from the
Chinese
Lower Pliocene Metailurus (Ewer 1955). Mctailurus seems
indistinguishable
-
from t'ie Miocene Pseudaelurus and Matthew (1929) considers
them
generally nseparahle, -but that Metai lurus represents a stage
leading
towards Fell s. Savage (1965), on the Miocene M. afri.canus
agrees with
Matthew. Stock (1934) however, has pointed out -Ve more
primitive
features ol‘ Pseudaelurus, such as the g ater number of
pre-molars and
the possession of an alisphenoid canal; which certainly seems to
warrant
generic separation. The American P. intrepidus has non-serrate
upper
canines (Stock 1934) while the European P. quadridentatus has
finely
serrated upper canines, and al30 lower incis (Ginsburg 1961).
In
both cases the teeth are moderately long and flattened.
The position and affinities of Me tailurus are rather
uncertain,
as in Viret's opinion it is closely related to Dirofeli s (Ewer
1955),
and the canines are also moderately long, although in nearly
all
other aspects the skull is feline in character (Zdansky 1 9 2 4
) . The
upper canines are not serrated and the reduction of the
pre-molars is a
trend shared by both Felinae and early Machaerodontinae. Hemmer
(1956)
agrees that Pi nofeli s can be derived from a nimravid stock but
that an
intermediate species has yet to be discovered.
A more recent contribution to the phlogeny of the Felidae
been suggested by Thenius (1967) in which the difficulties of
taxonomic
division in this family are expressed, due to the many
independent
parallel developments leading to superficial resemblances.
Thenius
recognises five sub-families; the Eocene Proailurinae at the
base of
the stock, the Oligocone Nimravinae and Hoplophonidao, and the
Pliocene/
Pleistocene Machaerodontinae and Felinae. The Nimravinae and
Hoplophoni-
dae are nowhere ancestral to the later cats but branched off
from the
Proailurinao at a very early stage. The Miocene Sansanosmilus
and
Busmi lus are extremely specializ'd end forms while ?Ji mravus
and Dini cti s
are less specialized side branches. The skull of Nimravus looks
very
much like that of a primitive feline, although the canine? are
inequal
114
-
115
in size and slightly serrated (Toohey 1959).
The Felinae and Machaerodontinae both have their origins in
the
Proailurinae with Pseudaelurus as the intermediate stage.
Machaerodus
is derived from an early Pscudae]urns (perhaps related to P.
quadri-
dentatus?) and a later form gave rise tc both the Felinae ana
Metai1-
urus. The latter is considered ancestral to Dinofelis, The
"false
"Rbre-tooths" are thus considered as Felinae and the most
closely re
lated to modern cats.
The separation of Pant hora and Feli s within the Felinae is
first
seen in the Upper Pliocene, with Lynx branching off at an
earlier
stage, and the origin of Acinonvx rather uncertain.
Apparently
Cryptoprocta. the ferret cat from Madagascar is a survivor from
the
Proailurinae.
Within the Machaerodontinoe, Homotherium and
Meganteroon/Smilodon
are bot\ derived frcm Machaerodus. Kurten (1963) separates them
into
tribes Hew theriini and Smi lodon tiri,
T ienius (1967) considers a Eurur i u ’igin for the Felinae,
with
migration into .itri* . Ewer (1^55^ not» . the African
Megantereon
eurynodcn ard Pi nolo V
-
1]6
noted an analogous utuation in the lynx, which is unique among
modern
Felinae in frequently possessing a post-c,-nassial complex
(talonid,
metaconid and M^) in the lower dentition. It apparently has made
a
reappearance in the lynx (Kurten 1963).
The clouded leopard, Neofolis nebulosa has sometimes been
quoted
as a living cat showing slight machaerodontine signs, as it has
exception
ally long canines. However, the lengthening is in both upper
and
lower canines, and there is no great difference in size between
them
(Grey 1867). The >ipper canines show no sign of narrowing
either and
the jaw still operates in the same way as other felines N.
nebulosa
is arboreal with short, stout legs and broad paws, rather
reminiscent
of Smilodon and Megantereon. This might suggest that the latter
were
also arboreal, although N. nebulosa has a long body and an
extremely
long tail (Walker 1964). The shortening of the tail in all the
later
Machaerodontinae could have a variety of reasons, but among
extant
Felidae, only the lynx American bobcat and manx have short
tails. The
African lynx, or caracal, is long-legged and
plains-dwelling.
4.4 The ac. /f the deposit
According to the most recent estimations on the age of
Makapansgat,
it is generally agreed that the deposits accumulated between
three to
four million years ago. /is regardsfossi1 correlation with
the
European Pleistocene, it seem? that the African
"Villafranchian"
occurred at an earlier date than the European Villafranchian,
although
there is no fixed agreement as yet on the definition of the
term
"Villafranchian".
-
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Author Collings G E Name of thesis Some New machaerodonts from
Makapansgat limeworks 1973
PUBLISHER: University of the Witwatersrand, Johannesburg
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