Ankylosaurus magniventris, Brown, 1908

Carpenter, Kenneth, 1982, Baby dinosaurs from the Late Cretaceous Lance and Hell Creek formations and a description of a new species of theropod, Contributions to Geology, University of Wyoming 20, pp. 123-134 : 131

Ankylosaurus magniventris

Fig. 11

Material: Teeth: UCMP 120195 (UCMP-V73076)

H 3.3 mm, W 2.9 mm; and UCMP 124399 (UCMP- V 5620) H 3.2 mm, W 2.7 mm.

Discussion: Teeth of Ankylosaurus are diagnostic, being simple, smooth cones with large denticles on the anterior and posterior edges and in having swollen bases. Other ankylosaurids, such as Euoplocephalus (see Coombs, 1971), Pinacosaurus , and Saichania (see Maryanska, 1977, Pl. 21, Fig. 2 a, b and Pl. 29, Fig. 4 a, b), have fluted or corrugated sides.

Only one of the teeth (UCMP 124399) is undamaged and unworn ( Fig. 11 ). It looks much like the tooth figured by Brown (1908), but lacks the wear facet and faint vertical ridges on the lingual side. There are six denticles on each side of the crown, the basal denticle being the smallest.

The other tooth is heavily worn. It is identified as Ankylosaurus because there is a smooth enameled surface and a large medial cone with denticles on the sides. It is not possible to determine if there was a swollen base, as this area is heavily worn. The heavy wear shows, despite the small size of the teeth relative to the skull ( Coombs, 1978), that ankylosaurids, at least the babies, relied upon their teeth to process food and did not crop and swallow food whole.

Figures

Figures 1-11. Fig. 1, Dromaeosauridae, tooth, UCM 39502. Fig. 2a-h, Sauromithoides inequalis: 20,, buccal view of hatchling left dentary, UCM 41666; c, lingual view; e, dorsal view; b, buccal view of left dentary, NMC 8540 (cast); d, lingual view; f, dorsal view; g, lateral view of hatchling basioccipital, UCM 43218; and h, ventral view. Fig. 3a-c, teeth of Pectinodon bakkeri: a, holotype, UCM 38445; b, paratype, UCM 38446; and c, paratype, UCMP 73098. Fig. 4, Pararıychodon lacustris, tooth, UCMP 124990. Fig. 5a, b, Tyrannosauridae: a as lateral view of UCMP 119853; and b, posterior view. Fig. 6, Theropoda, tooth, UCMP 124987. Fig. 7a, b, tooth of Aublysodon mirandus: a! lateral view of UCMP 124406; and b, posterior view. Fig. 8, Thescelosaurus sp., tooth, UCMP 124973. Fig. 9, Hadrosauridae, tooth, UCM 45060. Fig. 10, Ceratopsidae, tooth, UCM 45057. Fig. 11, Ankylosaurus magniventris, tooth, UCMP 124399. Heavy bars to left of specimens = 2 mm.