Living Fossils Living Large

Madagascar Hissing Cockroaches

Frances and I were asked if we would set up a living fossils table for the HMNS’s annual Dino Days celebration that took place here last week. Not having had any history or paleontology classes I was a little clueless as to which of our living animals would fit into the category of living fossils, other than our alligator.

We did some research and what we read lead us in several directions for what it means to be a living fossil. Some animals, like the echidna and platypus, are nicknamed living fossils because they exhibit “primitive” characteristics – like oviparity, or egg-laying, in mammals. The overall consensus is that a living fossil is an organism that originally lived during the time of the dinosaurs (or even predates them), has remained unchanged morphologically and appears the same as a species otherwise only known from the fossil record, has no close living relatives and has survived major extinction events.

Chambered Nautilus

There are several examples that fit this description: the crocodilians, horseshoe crabs, turtles, opossums, salamanders, roaches, millipedes, dragonflies, and the nautilus. These are some of the critters we have in our collection and you can also add ferns, ginkgos, gar fish and the coelacanth to the list. There remains a healthy debate over which plants or animals can and should be included. I have included some pictures of our fossils, both living and non-living at the end of this entry.

All in all, we had a great time in sharing our casts, skins, skulls and live animals with everyone who came up to the table during Dino Days. Hope to see you there next November!

Dino Days Baby Gator

Tiger Salamander - too cute

Fossilized crocodilian scute and modern scutes

Volunteers manned the Touch Tank giving visitors a chance to touch these little fellows - Horseshoe Crabs.

Cast of fossil turtle shell

The Apple Doesn’t Fall Too Far from the Tree

Another approach to figuring out what the very oldest hominids were up to (first discussed in an earlier entry involves observing the behavior of living primates and identifying trends or patterns that have a possible counterpart in the fossil record.

Among some living primates like gorillas and orangutans, there is a marked difference in size between males and females. This marked difference in size between males and females is referred to as sexual dimorphism.

Thanks to the dedicated research of primatologists who spend entire careers observing these animals in the field, we have good data sets related to behavior and how this behavior can be correlated to body size.

For example, male orangutans weigh twice as much as females.

They are much stronger and are prone to violence with other males during mating season as well as with females and their offspring whenever they encounter each other. Long- term observations have established that female orangutans prefer to avoid males outside the mating season.

Sexual dimorphism is also seen in the fossil record. The skeletons of male and female Australopithecines display this feature.

Based on patterns observed today in orangutans and the observed size differences among fossil hominids, we can suggest that behavior observed today may have also existed in the past: Australopithecines males may have acted violently among each other during mating season as well as against females and their offspring whenever they met.

The presence of artifacts, from stone tools to pottery and beyond increases our ability to understand and reconstruct past human behavior. Yet even in those cases where only the fossil record is present and artifacts are totally absent it is still possible to make cautious suggestions as to what these earliest ancestors of ours were up to.