Post by DinosaurMichael on Aug 14, 2012 8:13:34 GMT -5
Kronosaurus - Kronosaurus queenslandicus
Kronosaurus ( /ˌkrɒnoʊˈsɔrəs/ kron-o-sawr-əs; meaning "lizard of Kronos") is an extinct genus of short-necked pliosaur. It was among the largest pliosaurs, and is named after the leader of the Greek Titans, Cronus. Kronosaurus lived in the Early Cretaceous Period (Aptian-Albian). The holotype specimen of the species K. queenslandicus was described by Longman in 1924, and is currently in the Queensland Museum. Hampe described a second species, K. boyacensis, in 1992 from Colombia. Body-length estimates had previously put the total length of Kronosaurus at 12.8 meters (43 feet). However, a recent study comparing fossil specimens of Kronosaurus to other pliosaurs suggests that the previous estimate was an exaggeration, with the true length probably being only 9–10 meters (30–33 feet). The teeth of Kronosaurus are large in length (exceeding 7 cm - the largest up to 30 cm long with 12 cm crowns). However, they lack carinae (cutting edges) and the distinct trihedral (three facets) of Pliosaurus and Liopleurodon teeth. The combination of large size, conical shape and lack of cutting edges allows for easy identification of Kronosaurus teeth in Cretaceous deposits from Australia. Large, round bite-marks have been found on the skull of an Albian-age Australian elasmosaurid (Eromangasaurus) that could be from a Kronosaurus attack.
Otodus - Otodus obliquus
Otodus obliquus is an extinct mackerel shark which lived during the Paleocene and Eocene epochs, approximately about 60 to 45 million years ago. This shark is known from the fossil teeth and fossilized vertebral centra. Like other elasmobranchs, the skeleton of Otodus was composed of cartilage and not bone, resulting in relatively few preserved skeletal structures appearing within the fossil record. The teeth of this shark are large with triangular crown, smooth cutting edges, and visible cusps on the roots. Some Otodus teeth also show signs of evolving serrations. The fossils of Otodus indicate that it was a very large macro-predatory shark. The largest known teeth measure about 104 millimetres (4.1 in) in height. The vertebral centrum of this shark are over 12.7 cm (5 inch) wide. Scientists suggest that this shark commonly approached 9 meters (30 feet) in total length (TL). Otodus was a widespread species, as its remains have been excavated from Africa, Asia, Europe, and North America. O. obliquus likely preyed upon marine mammals, large bony fish, and other sharks. It was among the top predators of its time. Scientists determined that Otodus evolved into the genus Carcharocles, given substantial fossil evidence in the form of transitional teeth. Some teeth have been excavated from the sediments of the Potomac River in Maryland, USA, Ypres clay in Belgium, and western Kazakhstan, which are morphologically very similar to Otodus teeth but with lightly serrated cusplets and a serrated cutting edge. These transitional fossils suggest a worldwide evolutionary event, and support the theory that Otodus eventually evolved in to Carcharocles aksuaticus and thus initiated the Carcharocles lineage.
Kronosaurus ( /ˌkrɒnoʊˈsɔrəs/ kron-o-sawr-əs; meaning "lizard of Kronos") is an extinct genus of short-necked pliosaur. It was among the largest pliosaurs, and is named after the leader of the Greek Titans, Cronus. Kronosaurus lived in the Early Cretaceous Period (Aptian-Albian). The holotype specimen of the species K. queenslandicus was described by Longman in 1924, and is currently in the Queensland Museum. Hampe described a second species, K. boyacensis, in 1992 from Colombia. Body-length estimates had previously put the total length of Kronosaurus at 12.8 meters (43 feet). However, a recent study comparing fossil specimens of Kronosaurus to other pliosaurs suggests that the previous estimate was an exaggeration, with the true length probably being only 9–10 meters (30–33 feet). The teeth of Kronosaurus are large in length (exceeding 7 cm - the largest up to 30 cm long with 12 cm crowns). However, they lack carinae (cutting edges) and the distinct trihedral (three facets) of Pliosaurus and Liopleurodon teeth. The combination of large size, conical shape and lack of cutting edges allows for easy identification of Kronosaurus teeth in Cretaceous deposits from Australia. Large, round bite-marks have been found on the skull of an Albian-age Australian elasmosaurid (Eromangasaurus) that could be from a Kronosaurus attack.
Otodus - Otodus obliquus
Otodus obliquus is an extinct mackerel shark which lived during the Paleocene and Eocene epochs, approximately about 60 to 45 million years ago. This shark is known from the fossil teeth and fossilized vertebral centra. Like other elasmobranchs, the skeleton of Otodus was composed of cartilage and not bone, resulting in relatively few preserved skeletal structures appearing within the fossil record. The teeth of this shark are large with triangular crown, smooth cutting edges, and visible cusps on the roots. Some Otodus teeth also show signs of evolving serrations. The fossils of Otodus indicate that it was a very large macro-predatory shark. The largest known teeth measure about 104 millimetres (4.1 in) in height. The vertebral centrum of this shark are over 12.7 cm (5 inch) wide. Scientists suggest that this shark commonly approached 9 meters (30 feet) in total length (TL). Otodus was a widespread species, as its remains have been excavated from Africa, Asia, Europe, and North America. O. obliquus likely preyed upon marine mammals, large bony fish, and other sharks. It was among the top predators of its time. Scientists determined that Otodus evolved into the genus Carcharocles, given substantial fossil evidence in the form of transitional teeth. Some teeth have been excavated from the sediments of the Potomac River in Maryland, USA, Ypres clay in Belgium, and western Kazakhstan, which are morphologically very similar to Otodus teeth but with lightly serrated cusplets and a serrated cutting edge. These transitional fossils suggest a worldwide evolutionary event, and support the theory that Otodus eventually evolved in to Carcharocles aksuaticus and thus initiated the Carcharocles lineage.