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Teacher's Guide

OTHER ANIMALS AT WANNAGAN CREEK

How are the turtles from Wannagan Creek similar to ones alive today?
Wannagan Creek, and most of Western America, was home to a large variety of turtles and tortoises (tortoises are only terrestrial; turtles spend time in the water, as well). One very large turtle found at Wannagan Creek has some features in common with today's snapping turtle, although it is more primitive. Another smaller turtle from Wannagan (Protochelydra) bore a closer resemblance to a modern snapper but had a higher domed shell. Soft-shelled turtles have also been found at Wannagan, with Aspideretes being the most common. Soft-shelled turtles are common today and some species are native to Minnesota. Although they look strange, they don't really have a soft shell; it's just covered with leathery skin. Visitors can see cast copies of these turtles at Turtle World, touch turtle shells at Not So Soft and One That Got Away, and learn about the advantages of having a high-domed shell at the Puncture Proof? component.

How are the fish found at Wannagan Creek similar to ones alive today?
The fossil fish Esox was a primitive fish, probably related to modern pike, muskie, and pickerel. Some other ancient fish from Wannagan Creek, such as bowfin and gar, look very similar to their modern relatives. These fish have experienced slight changes over the last 60 million years, but they are still easily recognizable to anyone familiar with modern fish. These fish can be viewed in the crocodile diorama if visitors look "under water" using the Periscope, and read more about Wannagan Creek fish at Dangerous Waters.

Monitor lizards at Wannagan?
Monitor lizards, which include the very large Komodo dragon, are big, carnivorous lizards. Many kinds of monitor lizards today specialize in eating crocodilian eggs. They are excellent at sniffing out nests. Monitor lizards prey heavily on the eggs of Asiatic crocodiles, and the Nile monitor lizard is the biggest predator of crocodiles in Africa--they can eat up to half of all eggs! It isn't unlikely, therefore, that the monitor lizard found at Wannagan Creek had similar tastes.

What is a champsosaur? Why isn't it a crocodile?
Champsosaurs were aquatic reptiles closely related to snakes, lizards, and the modern tuatara. They look superficially like crocodiles, ate things crocodiles like (such as fish), and lived in the same types of environments favored by crocodiles. But skeletal structures, such as openings in the skull, betray their more lizard-like ancestry. Champsosaurs also lacked the armored skin that crocodilians have. Also, unlike crocodiles, which have nostrils on top of their snout, champsosaur nostrils are at the end of their snout. This may have made its breathing technique analogous to snorkeling. Visitors to the lake section of the diorama area can manipulate a champsosaur head in order to get it to breathe properly at Living Snorkels?. Champsosaurs occasionally crossed paths with the crocodiles at Wannagan Creek, but they probably kept their distance most of the time both to avoid competition and to avoid becoming a meal! Visitors can also observe their behavior through the Periscope in the Diorama. Look for the various champsosaur noses hidden in the Diorama.

What amphibians were at Wannagan?
Remains of fossil salamanders and frogs have been found, and it's likely that other amphibians lived there, too, since it was a warm, moist environment. Amphibians, unlike reptiles, are very dependent on water. Reptiles lay protective eggs with nutrients inside. Amphibians must lay their eggs in the water. And adult amphibian skin must be wet in order for the animal to breathe.

What birds were found? How were they similar to birds today?
Birds don't make it into the fossil record very often because they have very fragile skeletons. And birds in the Paleocene weren't as common as birds are today. Some fossil bird remains were found at Wannagan Creek, however. They mostly represent shore birds and some flightless birds. One particular species of bird, Dakotornis, is related to modern gulls and oystercatchers. Visitors can view cast specimens of bird fossils found at Wannagan Creek and learn about bird evolution at the No Music in the Air component.

Were the plants at Wannagan really like this?
Many fossil plant remains have been found at Wannagan. Some of the plants in the diorama are actually based on fossils found at the site. Others are copies of modern plants that live in environments similar to Wannagan Creek. We may never know exactly what the flora of Wannagan Creek looked like. Oreopanax is included in the diorama and was found at Wannagan Creek as well. It was a rather plain bush with small fruit. Some types of Oreopanax species are still alive today (they are in the family Araliaceae) and require warm weather. They live only in Mexico and Central America. Fossil cypress remains are also represented in the diorama. Cypresses are known to thrive in warm, wet conditions. Other plants to look for in the diorama that are based on real fossil evidence are ficus, water oak, magnolia, gingko, katsura, cherry, sequoia, ferns, and duck weed. Perhaps the most important thing for visitors to notice while looking at the diorama is the absence of grass. Grass didn't evolve until the later Miocene Epoch. At Wannagan Creek, there was none.

What insects were found at Wannagan Creek?
Not many insects or invertebrate fossils were found--just some fossil dragonfly wings and maybe a beetle or two. But that doesn't mean that Wannagan Creek was short on insects. There were probably a wide variety of them, just as there are in any wet, subtropical area today. This idea is supported by the traces they left. At Ancient Apartments, visitors can examine a cast replica of a fallen log. This fossil log is filled with burrows, made by insects or other invertebrates, such as clams. Visitors can try and determine whether the tree stump was alive or dead at the time the tunnels were created.

MAMMALS AT WANNAGAN CREEK

What are mammals and where did mammals come from?
Most people know that mammals have hair or fur, are warm-blooded, provide milk for their young, and give live birth. Unfortunately, these are all characteristics that do not fossilize. Paleontologists have to look at skeletal features when they identify a fossil mammal.

  • Mammals have unique teeth. Unlike reptiles, such as dinosaurs or crocodiles, whose teeth are all essentially the same, mammals have many different kinds of teeth. You are a mammal and you have incisors, canines, premolars, and molars.
  • Mammals and their reptilian relatives have only one hole in their skull for jaw muscle attachment, whereas other reptiles have two, and some, like turtles, have none at all.
  • Earlier reptiles have many bones in their jaw, but mammals have only one.
  • Mammals have a double occipital condyle. That means there are two knobs on the head where the first vertebra of the neck connects (Remember the crocodile occipital condyles that Bruce Erickson looked at? They had only one knob).
  • Mammals tend to walk with their legs under their bodies, unlike many kinds of "sprawling" reptiles (although really large dinosaurs had legs under their bodies, too, in order to support their enormous weight).
  • The lower vertebrae on the backs of mammals have no ribs attached to them.

    These are not all the distinguishing characteristics that define a mammal, but are certainly the most common.

    Why were they all so small?
    When mammals first evolved during the Mesozoic Era, there were already many large dinosaurs to compete with. Being a small insect-eater or scavenger wasn't such a bad life to live. However, once the dinosaurs were gone, there were many ecological niches vacant for the mammals to fill. Most were still small during the Paleocene Epoch, but they began to diversify, and eventually some became very large, specialized animals. Small, warm-blooded mammals have interesting challenges. Staying warm is one of them. Heat loss can be a big problem for a little mammal. Visitors can experiment with the Calorimeter in the diorama area to find out why.

    How can paleontologists tell so much about them from teeth?
    Teeth are very important in the identification of mammals. Usually they are all that remains. But mammal groups have very characteristic teeth. Paleontologists can tell a lot about a mammal from the shapes and numbers of cusps and ridges on its teeth. So even though Paleocene mammals were all small creatures that looked fairly similar, we can tell which ones were related to marsupials, which ones were related to later primates, and so on. Many prehistoric mammals are named for their teeth. For example, the triconodonts have three cones on their teeth. The multituberculates have several small bumps or "tubercles" on theirs. Visitors can see examples of these unique teeth at the What a Mouthful! component. Getting the Big Picture describes how a paleontologist can diagnose an insect-eating animal on the basis of a few teeth.

    Were these mammals like any alive today?

  • Protictis was a primitive carnivore. We can tell this from its sharp canine teeth. It was still fairly small, so its prey probably included creatures like lizards and small fish. It was only distantly related to modern carnivores. It was somewhat like a modern otter.
  • Ptilodus was a type of successful little mammal known as a multituberculate, named for its very strange teeth. It was about the size (and shape) of a squirrel, but its teeth were very different. Although they were once very common, all multituberculates went extinct about 50 million years ago. They are not closely related to any modern mammals.
  • Pantodonts were some of the largest mammals of the Paleocene (about the size of a small bear). They were rather slow moving plant eaters. Pantodonts are extinct and not closely related to modern mammals.
  • Condylarths were also rather large for their time (up to five feet long). They were herbivores. Although some types of condylarths are unspecialized, they are actually ancestral to hoofed animals. Phenacodus was related to horses, tapirs, and rhinos!

    Plesiadapis illustration
  • Plesiadapis was one of the earliest known primates. While it wasn't that different from the insectivores it lived with, it showed primate dentition. It probably resembled a lemur--one of the most primitive primates alive today. By thirty-five million years ago, primates had disappeared from North America. They only came back when early people crossed over from Asia about 15,000 years ago. Visitors use the fiber-optic map at Where Have Primates Live--and When? to compare the distribution of subtropical/tropical environments and primate distribution over time. These maps show how primates tend to stay where it's warm. Visitors also encounter the question: What primates DO live in North America today? Looking in a mirror provides the answer.

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