An introduction to the study of mammals living and extinctLydekker, Richard
Science
An introduction to the study of mammals living and extinct
Lydekker, Richard
Mammals
The essential characters of a piscivorous dentition are best exemplified
in the Dolphins, and also (as modifications of the carnivorous type) in
the Seals. This type consists of an elongated, rather narrow mouth, wide
gape, with numerous subequal, conical, sharp-pointed, recurved teeth,
adapted simply to rapidly seize, but not to divide or masticate, active,
slippery, but not powerful prey. All animals which feed on fish as a
rule swallow and digest them entire, a process which the structure of
prey of this nature, especially the intimate interblending of delicate,
sharp-pointed bones with the muscles, renders very advantageous, and for
which the above-described type of dentition is best adapted.
The carnivorous type of dentition is shown in its most specialised
development among existing mammals in the _Felidæ_. The function being
here to seize and kill struggling animals, often of large size and great
muscular power, the canines are immensely developed, trenchant, and
piercing, and are situated wide apart, so as to give the firmest hold
when fixed in the victim’s body. The jaws are as short as is consistent
with the free action of the canines, so that no power may be lost. The
incisors are very small, so as not to interfere with the penetrating
action of the canines, and the crowns of the molar series are reduced
to scissor-like blades, with which to pare off the soft tissues from
the large bones, or to divide into small pieces the less dense portions
of the bones for the sake of nutriment afforded by the blood and marrow
they contain. The gradual modification between this and the two following
types will be noticed in their appropriate places.
In the most typical insectivorous animals, as the Hedgehogs and Shrews,
the central incisors are elongated, pointed, and project forwards, those
of the upper and lower jaw meeting like the blades of a pair of forceps,
so as readily to secure small active prey, quick to elude capture, but
powerless to resist when once seized. The crowns of the molars are
covered with numerous sharp edges and points, which, working against each
other, rapidly cut up the hard-cased insects into little pieces fit for
swallowing and digestion.
The omnivorous type, especially that adapted for the consumption of soft
vegetable substances, such as fruits of various kinds, may be exemplified
in the dentition of Man, of most Monkeys, and of the less modified Pigs.
The incisors are moderate, subequal, and cutting. If the canines are
enlarged, it is usually for other purposes than those connected with
food, and only in the male sex. The molars have their crowns broad,
flattened, and elevated into rounded tubercles. The name _Bunodont_, or
hillock-toothed, has been proposed for molars of this type, and will
frequently be found convenient.
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