Word Finder - incisors

definition

One of the front teeth of mammals, between the canines.

As he spoke, his incisors grew.

In all cases a more or less full series of teeth is developed, these being differentiated into incisors, canines, premolars and molars, when all are present; but only a single pair of teeth in each jaw has deciduous predecessors.

The teeth are usually differentiated into incisors, canines and molars.

They were even with the teeth around them, as if his incisors had just …grown.

Even in this the forward direction of the lower incisors is noticeable.

As a sub-order, the Paucituberculata are characterized by the presence of four pairs of upper and three of lower incisor teeth; the enlargement and forward inclination of the first pair of lower incisors, and the presence of four or five sharp cusps on the cheek-teeth, coupled with the absence of "syndactylism" in the hind limbs.

How had he not severed an artery or killed her with those four inch incisors?

The tail is rudimentary, the first hind-toe opposable, the first pair of upper incisors very large, but the second and third either absent or small and placed partially behind the larger pair; and only five pairs of cheek-teeth in each jaw.

The lower incisors are partially inclined forwards, compressed and tapering, bevelled at the ends.

The two lower incisors are long, very slender, sharp-pointed and horizontally placed.

They agree, for instance, with that family in the presence of a descending flange at the hinder end of each side of the lower jaw; but their dentition is of a more generalized type, comprising the full series of 44 teeth, among which the incisors and canines are of normal form, but specially enlarged, and developing roots in the usual manner.

On the other hand, the considerably smaller Nototherium, characterized by its sharp and broad skull and smaller incisors, seems to have been much more wombat-like, and may perhaps have possessed similar burrowing habits.

In the lower jaw the incisors and canines are directed straight forwards, and are of small size and nearly similar form; the function of the canine being discharged by the first premolar, which is larger than the other teeth of the same series.

The maximum number of teeth is 36, there being typically two pairs of incisors and three of premolars in each jaw.

The sportive lemurs (Lepidolemur) are smaller than the typical species of Lemur, and the adults generally lose their upper incisors.

Unlike the early horses, the later premolars are as complex as the molars; and although there is a well-marked gap between the canine and the premolars, there is only a very short one between the former and the incisors.

The incisors are chisel-shaped, and the canines tend to become isolated, so as in the more specialized forms to occupy a more or less midway position in a longer or shorter gap between the incisors and premolars.

The incisors are chisel-shaped; and (unlike the early Hippoidea) there is no gap between the first premolar, when present, and the second.

Of the upper incisors the first and second are nearly equal, with short, broad crowns, the third is large and conical, considerably larger than the canine, which is separated from it by an interval.

With the single exception of the Indian sloth-bear, all the species have forty-two teeth, of which the incisors and canines closely resemble those of purely carnivorous mammals; while the molars, and especially the one known as the " sectorial " or " carnassial," have their surfaces tuberculated so as to adapt.

On the other hand, resemblance to that genus is shown by the reduction of the upper incisors to a single pair.

The front surface of the incisors has a broad, shallow groove.

Lower incisors diminishing in size from the first to the third; the canine, which is in contact with the third incisor, large and conical, working against (and behind) the canine-like third upper incisor.

Finally, in the Oligocene Colodon the last three upper premolars are like the molars, and the first pair of lower incisors is lost.

In this group the incisors and canines are very variable in number and form; the lower canine being separated by only a short gap from the outer incisor (when present), but by a long one from the first premolar, which is in contact with the second.

With the exception of the first lower premolar, the dentit i on is complete; the incisors being normal, but the canine rudimentary, and the last upper molar distinctly triangular.

The incisors tend to become latera l, the canines are enlarged, and the last upper molar is sub-quadrangular.

It differs from typical rats of the genus Mus by its broader incisors, and the less distinct cusps on the molars.

The tail is short or rudimentary, the incisors are short, and the outer surface of the lower jaw is marked by a distinct ridge.

Other modifications are the loss of the upper incisors; the development of the canines into projecting tusks; and the loss of the anterior premolars.

As regards classification, the first group is that of the Pecora, or Cotylophora, in which the cheek-teeth are selenodont, but there are no upper incisors or canine-like premolars, Pecora.

The cheek-teeth are selenodont, and one pair of upper incisors is retained, while some of the anterior premolars assume a canine-like shape, and are separated from the rest of the cheekseries.

The cheek-teeth are selenodont, as in the two preceding groups; there are no upper incisors, but there are long, narrow and pointed upper canines, which attain a large size in the males; the lower canines are incisor-like, as in the Pecora, and there are no caniniform premolars in either jaw.

There is at least one pair of upper incisors, while the full series of 44 teeth may be present.

Both incisors and canines are devoid of roots and grow throughout life, the canines, and in the typical species one pair of lower incisors, growing to an immense size.

Rodents may be characterized as terrestrial, or in some cases arboreal or aquatic, placental mammals of small or medium size, with a milk and a permanent series of teeth, plantigrade or partially plantigrade, and generally five-toed, clawed (rarely nailed or semi hoofed) feet, clavicles or collar-bones (occasionally imperfect or rudimentary), no canine teeth, and a single pair of lower incisors, opposed by only one similar and functional pair in the upper jaw.

In all rodents the upper incisors resemble the lower ones in growing uninterruptedly from persistent pulps, and (except in the hare group, Duplicidentata) agree with them in number.

In t he Duplicidentata only is there more than a single pair of incisors, and in these the additional pair is small and placed behind the middle pair.

In this group the enamel extends partially to the back of the incisors, but in all the rest it is restricted to the front surface, so that, by the more rapid wearing-away of the softer structures behind, a chisel-shaped edge is maintained.

The tongue presents little variability in length, being short and compressed, with a blunt tip, which is never protruded beyond the incisors.

The mouth is divided into two cavities communicating by a narrow orifice, the anterior one containing the incisors and the posterior the molars, the hairy skin of the face being continued inwards behind the incisors.

These lead on to the sousliks, Spermophilus (or Citellus), in which the incisors (as in the following genera) differ from those of all the squirrels in not being compressed.

Geomys bursaries, the "red pocket-gopher" of North America, with deeply grooved incisors, inhabits the plains of the Mississippi, living in burrows like the mole.

In the typical jerboas, Jaculus (or Dipus), ranging from North Africa to Persia, Russia and Central Asia, there are only three hind toes, the incisors are grooved, and the premolars are generally wanting.

The other genera have five toes, of which only the middle three are functional, and smooth incisors.

The incisors are very large; and the palate of the skull is narrow.

Golunda, from India and Africa, is like Mus, but with grooved upper incisors.

Here also may be noticed the huge Philippine long-haired rats of the genus Phlaeomys, characterized by their broad incisors, transversely laminated molars and large claws.

They hay e large heads, projecting incisors, no ears, almost functionless eyes and moderately long tails; the skin, with the exception of a few hairs on the body and frinr-es on the feet, being naked.

The remaining and more typical members of the family, one of which is aquatic, are characterized by their short incisors, the strong masseteric ridges on the sides of the lower jaw, the long and curved par-occipitals and the palate contracted in front.