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Hello! I've just swapped for some fossils, from eastern Nebraska, Cuming County. I suspect the shells are inoceramus - What do you think? There is also Petrified Wood - Any idea on age? It is agatized, it seems. These were from a dragline-type operation - Mammal fossils are also found.... I attach a photo of my Mammoth tooth, from the same area. I have searched for data to no avail! So, firstly, what are the shell fossils? I think perhaps inoceramus. But what era? Secondly - The petrified wood - a time period would be helpful if possible. Thirdly - The Mammoth Tooth - Is my ID correct? Mammoth Tooth - Mammuthus columbi 0.00 12/18/2017 Chris Stalp (trade) West Point, Cumings County, Nebraska Late Pleistocene - (About 25 thousand years old) The Columbian mammoth (Mammuthus columbi) is an extinct species of mammoth that inhabited North America as far north as the northern United States and as far south as Costa Rica during the Pleistocene epoch. It was one of the last in a line of mammoth species, beginning with M. subplanifrons in the early Pliocene. The Columbian mammoth evolved from the steppe mammoth, which entered North America from Asia about 1.5 million years ago. The pygmy mammoths of the Channel Islands of California evolved from Columbian mammoths. The closest extant relative of the Columbian and other mammoths is the Asian elephant. Columbian mammoths had four functional molar teeth at a time, two in the upper jaw and two in the lower. About 23 cm (9.1 in) of the crown was within the jaw, and 2.5 cm (1 in) was above. The crown was pushed forward and up as it wore down, comparable to a conveyor belt. The teeth had separated ridges of enamel, which were covered in "prisms" directed towards the chewing surface. Wear-resistant, they were held together with cementum and dentin. A mammoth's molars were replaced five times over the animal's lifetime. The first molars were about the size of those of a human, 1.3 cm (0.51 in); the third were 15 cm (5.9 in) long, and the sixth were about 30 cm (1 ft) long and weighed 1.8 kg (4 lb). With each replacement, the molars grew larger and gained more ridges; the number of plates varied between individuals. Kingdom: Animalia Phylum: Chordata Class: Mammalia Order: Proboscidea Family: Elephantidae Tribe: Elephantini Genus: †Mammuthus Species: †columbi