One of the fun parts about museum work is seeing what people have found and helping them learn about natural history. I went out just this morning to look at this object that appeared in a farmer’s field in north central Ohio. What is it!? (Not the trowel, the other thing!) This isn’t real hard if you’ve seen one before, but if you haven’t…what is it!?
This unusual looking bone is actually from a very common animal, the domestic cow. It is the metacarpal, or long bone of the forefoot. That’s right, its a foot bone and not a long bone of the leg! And there’s more to the story that that. Its actually two fused metacarpals, from digits 3 and 4. So if you picture the long bones in your hand that connect with your middle finger and the ring finger, then fuse those two together you’ve got a strong, fused metacarpal. The cows other digits are lost through evolution, however a remnant of the 5th digit still remains as a small bone that articulates near the upper end of this metacarpal bone. Its interesting too that in dissection of a fetal or newborn calf, these 3rd and 4th metacarpals are not yet fused can still be separated into their individual bones!
Why does the cow, and other large ungulates like deer, elk, sheep, goats, etc., find it advantageous to fuse their foot bones!? Basically it’s for strength and for speed. The two fused metacarpals are thick-walled and provide a very strong structure to support the weight of the animal. Also lengthening of the lower leg, by virtue of lengthening the foot, provides for greater speed. This is an advantage for prey species. These animals don’t need to manipulate the feet in different directions, they just need to move them in one direction forward. Thus they’ve fused and reduced the foot bones for a fast, strong, and stream-lined structure. The hoofed mammals are called unguligrade meaning that they walk on their toes. You can see this in the picture of the bison skeleton, and you’ll also see that the toes articulate with the rounded distal end of the metacarpal.
Metacarpal and metatarsal of domestic cattle.
These bones, the metacarpal from the forefoot and the metatarsal from the hindfoot, are brought to museums for identification because of their unusual appearance and heavy weight. These bones are so dense that many people think they’ve found a mineralized, fossil bone. Another interesting note, cattle and bison are so similar in the postcranial skeleton that individual bones can often be very hard to identify to species. Bison do tend to be a bit larger and more robust, however there are many breeds of cattle and there can be overlap in size between cattle and bison. Bison have been in Ohio since probably the Late Pleistocene and until about 1800, so if you find one of these bones its probably a cow but just might be an early bison!
This interesting specimen that we were called out to look at is a single tooth, the third molar, of a mastodon (Mammut americanum)! What you see in the photos is the crown of the tooth, the part of the tooth that would be above the gum line. You can easily distinguish a mastodon tooth from a mammoth tooth. The mastodon has conical shaped cusps on the crown while the mammoth has multiple ridges of enamel that form a flat grinding surface. This reflects the diet of each species. The mastodon was a browser and ate leaves and branches of trees and shrubs as well as conifer needles and aquatic plants. The mammoth was more of a grazer, consuming mainly coarse grasses and sedges.
This individual was a young adult. The third molar is the last tooth to erupt in mastodons (and in mammoths and elephants), but this tooth doesn’t show any wear on the cusps. Thus the tooth was fully formed but hadn’t erupted to the point of receiving any wear.
This tooth was discovered by the landowner while digging to improve drainage in a soybean field. Is more of the mastodon still in the ground!? We don’t know yet, but stay tuned to this blog. If and when more of this animal is recovered, you’ll be the first to know.