1911 Encyclopædia Britannica/Glyptodon

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GLYPTODON (Greek for "fluted-tooth"), a name applied by Sir R. Oweu to the typical representative of a group of gigantic, armadillo-like, South American, extinct Edentata, characterized by having the carapace composed of a Solid piece (formed by the union of a multitude of bony dermal plates) without any movable rings. The facial portion of the skull is very short; a long process of the maxillary bone descends from the anterior part of the zygomatic arch; and the ascending ramus of the mandible is remarkably high. The teeth, 88 in the later species, are much alike, having two deep grooves or flutings on each side, so as to divide them into three distinct lobes (fig.).

Two views of the tooth of a Glyptodon; the upper figure showing one side, and the lower the crown.

They are very tall and grew throughout life. The vertebral column is almost entirely welded into a solid tube, but there is a complex joint at the base of the neck, to allow the head being retracted within the carapace. The limbs are very strong, and the feet short and broad, resembling externally those of an elephant or tortoise.

Glyptodonts constitute a family, the Glyptodontidae, whose position is next to the armadillos (Dasypodidae) ; the group being represented by a number of generic, types. The Pleistocene forms, whose remains occur abundantly in the silt of the Buenos Aires pampas, are by far the largest, the skull and tail-sheath in some instances having a length of from 12 to 16 ft. In Glyptodon (with which Schistopleurum is identical) the tail-sheath consists of a series of coronet-like rings, gradually diminishing in diameter from base to tip. Daedicurus, in which the tail-sheath is in the form of a huge solid club, the largest member of the family; in Panochthus and Sclerocalyptus (Hoplophorus) the tail-sheath consists basally of a small number of smooth rings, and terminally of a tube. In some specimens of these genera the horny shields covering the bony scutes of the carapace have been preserved, and since the foramina, which often pierce the latter, stop short of the former, it is evident that these were for the passage of blood-vessels and not receptacles for bristles. In the early Pleistocene epoch, when South America became connected with North America, some of the glyptodorits found their way into the latter continent. Among these northern forms some from Texas and Florida have been referred to Glyptodon. One large species from Texas has, however, been made the type of a separate genus, under the name of Glyptotherium texanum. In some respects it shows affinity with Panochthus, although in the simple structure of the tail-sheath it recalls the undermentioned Propalaeohoplophorus. All the, above are of Pleistocene and perhaps Pliocene age, but in the Santa Cruz beds of Patagonia there occur the two curious genera Propalaeohoplophorus and Peltephilus, the former of which is a primitive and generalized type of glyptodont, while the latter seems to come nearer to the armadillos. Both are represented by species of comparatively small size. In Propalaeohoplophorus the scutes of the carapace, which are less deeply sculptured than in the larger glyptodonts, are arranged in distinct transverse rows, in three of which they partially overlap near the border of the carapace after the fashion of the armadillos. The skull and limb-bones exhibit several features met with in the latter, and the vertebrae of the back are not welded into a continuous tube. There are eight pairs of teeth, the first four of which are simpler than the rest, and may perhaps therefore be regarded as premolars. More remarkable is Peltephilus, on account of the fact that the teeth, which are simple, with a chevron-shaped section, form a continuous series from the front of the jaw backwards, the number of pairs being seven. Accordingly, a modification of the character, even of the true Edentata, as given in the earlier article, is rendered necessary. The head bears a pair of horn-like scutes, and the scutes of the carapace and tail, which are loosely opposed or slightly overlapping, form a number of transverse rows.

Literature. — R. Lydekker, "The Extinct Edentates of Argentina," An. Mus. La Plata — Pal. Argent, vol. iii. p. 2 (1904); H. F. Osborn, " 'Glyptotherium texanum,' a Glyptodont from the Lower Pleistocene of Texas," Bull. Amer. Mus., vol. xvii. p. 491 (1903); W. B. Scott, "Mammalia of the Santa Cruz Beds—Edentata," Rep. Princeton Exped. to Patagonia, vol. v. (1903-1904). (R. L.*)