Saber–toothed cat facts for kids
The saber–toothed cats or sabretooth cats are some of the best known and most popular extinct animals. They are among the most impressive carnivores that ever have lived. These cats had long canines and jaws which opened wider than modern cats. This suggests a different style of killing from modern felines.
The sabre-tooth style of life evolved at least five times amongst carnivorous mammals. This is one of the best-known examples of convergent evolution.
- Creodonts, were the earliest sabre-tooths known. They lived in the Eocene, and are in a different order from the Feliformia. Machaeroides and Apataelurus are examples.
- The Nimravids were a basal group in the Feliformia, lasting from the Eocene to the later Miocene epochs. Hoplophoneus is an example.
- The Barbourofelidae is another family of Feliforms which developed the sabre-tooth lifestyle. They flourished in the Miocene. They are probably more closely related to the felids than the Nimravids.
- Sparassodonts, such as Thylacosmilus, were a metatherian group of mammals. They used to be called "marsupial sabre-tooths", but they belong to a sister-group to the marsupials. Miocene to Pliocene.
- The Machairodontinae: a subfamily of the Felidae, lived from the Miocene to the Pleistocene (23 million years ago to 11,000 years ago). Includes the famous Smilodon.
- Nimravides, which is a member of the Felinae, and not one of the Nimravids.
The saber tooths were ambush predators, and probably lived in open forests. This would explain their widespread occurrence in the Miocene, when much of the land was covered with woodland. Apart from the canine teeth, their adaptations included strength in the forelimbs (more so than present-day large cats). Their robust (heavy, tough) bodies speak of strength rather than speed.
An idea of how they killed is as follows. They hid in wait, and pounced. They hung on round the prey's neck, gripping and slashing the underside of the throat with their canine teeth. This would cause death by blood loss and loss of the air supply.
The fact that their teeth vary is interesting. Some have larger teeth, some had smaller dagger-like teeth, some had smooth thick teeth, others had blade-like teeth, sometimes with serrated edges. Some had flanges on the lower jaw, most did not. Ewer remarks that this must show that there were variations in killing method, and in the type of prey, but we know little about this.
There are none living today: they are extinct. The extinctions followed climate change, as the world cooled and grassland took over from woodland in the Pliocene and Pleistocene.
Contents
Skeleton
Skull
The most studied section of the machairodont group is the skull, and specifically the teeth. With a large range of genera, good fossil representation, comparable modern relatives, diversity within the group, and a good understanding of the ecosystems inhabited, the machairodont subfamily provides one of the best means of research for the analysis of hypercarnivores, specialization, and the relationships between predator and prey.
Machairodonts are divided into two types: dirk-toothed and scimitar-toothed. Dirk-toothed cats had elongated, narrow upper canines and generally had stocky bodies. Scimitar-toothed cats had broader and shorter upper canines and a typically lithe body form with longer legs. The longer-toothed cats often had a bony flange that extended from their lower mandible. However, one genus, Xenosmilus, known only from two fairly complete fossils, broke this mould; possessing both the stout, heavy limbs associated with dirk-toothed cats, and the stout canines of a scimitar-toothed cat.
Carnivores reduced the number of their teeth as they specialized in eating meat instead of grinding plant or insect matter. Cats have the fewest teeth of any carnivore group, and machairodonts reduce the number even further. Most machairodonts retain six incisors, two canines, and six premolars in each jaw, with two molars in the upper jaw only. Some genera, such as Smilodon, bear only eight premolars with one fewer on the mandible, leaving only four large premolars on the mandible along with two stunted canines and six stout incisors. The canines are curved back smoothly, and serrations are present, but are minor and wear away with age, leaving most middle-aged machairodonts (at about four or five) with no serrations. Hints in the bones such as these help paleontologists to estimate the age of an individual for population studies of an animal long extinct.
Longer canines necessitate a larger gape. A lion with a gape of 95° could not bear canines that are nine inches long because they would not be able to have a gap between the lower and upper canines larger than an inch or so, not enough to use for killing. Machairodonts, along with the other groups of animals that acquired similar teeth by convergent evolution, needed a way to change their skulls to accommodate the canines in several ways.
The main inhibitors of a large gape for mammals are the temporalis and masseter muscles at the back of the jaw. These muscles have the capacity to be powerful and undergo a great degree of modification for ranging bite forces, but are not very elastic due to their thickness, placement, and strength. To open the mouth wider, these species needed to make the muscles smaller and change their shape. The first step in this was to reduce the coronoid process. The masseter, and especially the temporalis, muscles insert on this jutting strip of bone, so reduction of this process meant the reduction of the muscles. Less mass for each muscle allowed greater elasticity and less resistance to a wide gape. Changing the shape of the temporalis muscle in this respect created a greater distance between the origin and insertion, so that the muscle became longer and more compact, which is generally a more suitable format for this type of stretching. This reduction led to a weaker bite.
The skulls of machairodonts suggests another change in the shape of the temporalis muscle. The main constraint to opening the jaws is that the temporalis muscle will tear if it is stretched past a critical degree around the glenoid process when the mouth is opened. In modern felids, the occipital bone extends backward, but the temporalis muscles that attach to this surface are strained when opening the jaw wide as the muscle is wrapped around the glenoid process. To reduce the stretch of the temporalis muscle around the immovable process, machairodonts evolved a skull with a more vertical occipital bone. The domestic cat has a gape of 80°, while a lion has a gape of 91°. In Smilodon, the gape is 128°, and the angle between the ramus of the mandible and the occipital bone is 100°. This angle is the major limiting factor of the gape, and reducing the angle of the occipital bone relative to the palate of the mouth, as seen in Smilodon, allowed the gape to increase further. Had the occipital bone not been stretched towards the palate, and closer to perpendicular, the gape would theoretically be less, at roughly 113°.
The skulls of many sabre-tooth predators, including machairodonts, are tall from top to bottom and short from front to back. The zygomatic arches are compressed, and the portion of the skull bearing facial features, such as eyes, is higher, while the muzzle is shorter. These changes help to compensate for an increased gape. Machairodonts also had reduced bottom canines, maintaining the distance between those in the upper and lower jaws.
Derived anatomy and diet
Bite strength
The jaws of machairodonts, especially more derived species with longer canines, such as Smilodon and Megantereon, are unusually weak. Digital reconstructions of the skulls of lions and of Smilodon show that the latter would have fared poorly with the stresses of holding onto struggling prey. The main issue was the stresses suffered by the mandible: a strong force threatened to break the jaw as pressure was placed on its weakest points.
Smilodon would have had one-third the bite force of a lion, had it used only its jaw muscles. However, the neck muscles that connected to the back of the skull were stronger and depressed the head, forcing the skull down. When the jaw was hyper-extended, the jaw muscles could not contract, but the neck muscles pressed the head down, forcing the canines into whatever resisted them. When the mouth was closed far enough, the jaw muscles could raise the mandible by some margin.
Diet
On occasion, the bone of a fossilised predator is preserved well enough to retain recognizable proteins that belong to the species it consumed when alive. Stable isotope analysis of these proteins has shown that Smilodon preyed mainly on bison and horses, and occasionally ground sloths and mammoths, while Homotherium often preyed on young mammoths and other grazers such as pronghorn antelope and bighorn sheep when mammoths were not available.
The face
American paleontologist George Miller set forth a set of features not previously thought of in the soft tissues of machairodonts, specifically Smilodon.
The first change he suggested in the appearance of machairodonts was lower ears, or rather the illusion of lower ears due to the higher sagittal crest. However, the positioning of the ears is always similar in modern felids, even in individuals that have crests comparable in size to those of sabretooth cats. The positioning of the pinnae, or outer ears, along with fur color, are dependent on the individual doing the reconstruction. Large or small, pointed or rounded, high or low, fossils do not record these characteristics, leaving them open to interpretation.
Miller also suggested a pug-like nose. Aside from the pug and similar dogs, no modern carnivore exhibits a pug nose due to it being an unnaturally created trait originating from selective breeding. The relatively low distribution of the pug nose has resulted in it being generally ignored. Miller's rationale is based on the retraction of Smilodon nasal bones. Criticism of Miller's theory compares the nasal bones of lions and tigers. Lions, when compared to tigers, also have strongly retracted nasal bones, but a lion's rhinarium, or external nose, is no more retracted than the tiger's. Thus, the pug nose of Smilodon proposed by Miller has little evidence in the physical structures of comparable animals. According to Antón, García-Perea and Turner (1998), the nostrils of living felids always extend to a similar position, independently of the length of the nasal bones, which in Smilodon falls within the range observed in modern species.
The third idea proposed is the elongation of the lips by 50%. While his other hypotheses have been largely discarded, the last is used significantly in modern depictions. Miller argues that longer lips allows the greater elasticity needed for biting prey with a wider gape. Although this argument has been disputed within the scientific community, it remains supported nevertheless by artists. Scientific criticism points out that the lips of modern cats, especially larger species, display incredible elasticity and the usual lip length would stretch suitably, despite the larger degree of opening, and that in living carnivores the lip line is always anterior to the masseter muscle, which in Smilodon was located just behind the carnassials. Regardless, reconstructions of Smilodon, Machairodus, and other species are shown with long lips, often resembling the jowls of large dogs.
Studies of Homotherium and Smilodon suggest that scimitar-toothed machairodonts like Homotherium itself possessed upper lips and gum tissue that could effectively hide and protect their upper canines; a trait they shared in common with modern cat species, while Smilodon had canines that remained partially exposed and protruded past the lips and chin even while the mouth was closed due to their great length.
Vocalizations
Comparisons of the hyoid bones of Smilodon and lions show that the former, and possibly other machairodonts, could potentially have roared like their modern relatives. A 2023 study suggested that while machairodonts had the same number of hyoid bones as "roaring" cats, their shape was closer to that of "purring" cats.
Images for kids
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Reconstruction of a Smilodon
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1st saber-tooth instance: Gorgonopsidae (Theriodontia, Therapsida, Synapsida) – Lycaenops angusticeps skull
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4th saber-tooth instance: Oxyaenidae (Creodonta) – Machaeroides skull
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5th saber-tooth instance: Nimravidae (Feliformia, Carnivora) – Hoplophoneus primaevus skull and upper cervical vertebrae
See also
In Spanish: Macairodontinos para niños
