What is Paleontology? Part 1: Invertebrate Paleontology

TBEX Fort Lauderdale: Six Lessons Learned
Society of Vertebrate Paleontology - 2015: Dallas, Dinosaurs, and Desmostylus

1

One of the most common questions I get is “what is paleontology?”

And another question is, “oh, so like Ross on Friends?” 

And yet another is along the lines of, “so you’re like Indiana Jones, right?”

As an educator and a person with training in paleontology, I feel the need to set the record straight – in, you know, a totally approachable and not dickish kind of way. What is paleontology?

Here’s what paleontology isn’t:

  • It doesn’t involve the study of ancient human remains or human cultures. That’s archaeology, a subset of anthropology – the study of human culture, past and present. And while we sometimes work with friends in archaeological fields, paleontological research doesn’t touch on anything having to do with human culture, tumbling boulders, or crystal skulls. Sorry, Indiana Jones.
  • It doesn’t just involve the study of ancient human evolution, although there is some wiggle room here: this is more along the lines of paleoanthropology, or biological (physical) anthropology – the study of ancient human anatomy and behavior, the development and evolution of humans and their closest relatives, and human prehistory. To be clear, paleoanthropology is a subset of paleontology, but not all paleontologists study paleoanthropology.
  • It isn’t just the study of dinosaurs.

Paleontology is the study of ancient life, in the form of fossils – preserved evidence of ancient life. That includes plants (paleobotany), pollen (palynology), tiny fossils (micropaleontology), paleoanthropology, the study of organic decay and fossil formation (taphonomy), the study of fossil tracks and traces (ichnology), and the study of past climates and ecosystems (paleoecology).

Paleontology tells us about the past, both in terms of its ecology and its biota. 

Invertebrate Paleontology versus Vertebrate Paleontology

One of the most common questions I receive is, "What is paleontology?" Any five year old can give you a straight answer, but adults often have conflicting responses. As an educator and a person with training in paleontology, I feel the need to set the record straight.

And a big question we’ve been getting recently has to do with two main subsets of paleontology: invertebrate paleontology, and vertebrate paleontology.

My background as a paleontologist, through my research, consulting work, and teaching, has focused largely on vertebrate paleontology, as well as ichnology (trace fossils such as tracks or droppings).

But to delve into the differences between invertebrate paleontology and vertebrate paleontology, I would be remiss if I didn’t include some of the great examples of the creatures studied within each field.

Seriously, these critters are way cool.

In each section I’ll start with the definition, and we’ll explore some examples of famous creatures and important studies within both major subsets of paleontology.

Keep in mind, these are only two subsets within a very broad range of paleontological disciplines. But since we’ve had so many questions on the topic lately, it’s my aim to help educate and inform our readers on these two sub-fields.

Invertebrate Paleontology

A vertebrate is an animal with vertebrae, the components of a backbone. In contrast, an invertebrate is an animal without a backbone. Spineless, but no less bold!

Invertebrate paleontology, therefore, is the study of ancient animals without a backbone. Vertebrate paleontology, conversely, is the study of animals with a backbone.

There are lots of creatures without backbones, both today and in our ancient past. Modern examples include:

  • insects (we bet you can imagine plenty examples)
  • crabs and lobsters (which are really tasty)
  • arachnids (such as spiders, ticks, mites, and scorpions)
  • mollusks (including snails, slugs, octopus, clams, oysters, and their relatives)
  • corals (yes, corals are tiny and amazing animals!)
  • jellies (or jellyfish, though they aren’t fish)
  • sponges (but probably not the kind in your kitchen sink)
  • annelid worms (think earthworms)
  • sea stars and their relatives (which share lots of features with other deuterostome animals, like vertebrates)
  • nematode worms (think C. elegans and other model genetic organisms)
  • protozoans (Giardia and lots of other single-celled animals)
  • tunicates and cephalochordates (which are closely related to vertebrates)

…as you can see, invertebrates as a group are really diverse. They also aren’t in one closely related group; phylogenetically, the word ‘invertebrate’ doesn’t mean much, other than the animal doesn’t have a backbone. In a big old animal family tree, invertebrates are scattered everywhere, a paraphyletic group to the max. Invertebrates include some ancestors of the common ancestor of invertebrates and vertebrates, but not all of them – vertebrates are left out.

Because vertebrates and invertebrates share a common ancestor, they could all be grouped in one big tree with all of those ancestors, including the ancestor itself. That would make a monophyletic group.

Take a look at this family tree, or phylogenetic tree, of reptiles and birds to help you understand what a paraphyletic group looks like:

Paraphyletic
CC BY-SA 3.0 – A paraphyletic tree that doesn’t include Aves (birds).

So why do we even use the term ‘invertebrate’? Well, it’s simple to understand that it describes an animal without (in-) vertebrae; and as human beings we are just so darn fascinated with the idea of categorizing things. We can instantly conjure a picture in our heads of any number of animals that don’t have a backbone.

Now. If we know a little bit about what invertebrates are, what do invertebrate paleontologists study?

The simple answer is: Any fossil invertebrates, including but not limited to the organisms listed above. One of the absolute coolest things about invertebrate paleontology is that we have a huge bonanza of invertebrate species in the fossil record that are almost nothing like what we see today.

Enter the Ediacaran Fauna and the Cambrian Explosion!

In the Precambrian (Neoproterozoic), from about 600 to 545 million years ago, the first experimental body plans of animal life were just getting revved up. Evolution and biological body plans were conspiring to concoct some weird creatures. A famous assemblage of these early invertebrate animals was found in Ediacara, South Australia. The Ediacaran fauna are sometimes called the “Vendian biota”.

By 530 million years ago, the Cambrian Explosion brought forth most of the animal groups we see today. The Ediacaran fauna and their kin took their time, tens of millions of years, to diversity into this “explosion”, which is best preserved in the fossil record in the famous Burgess Shale in Yoho National Park, British Columbia, Canada.

Ediacaran Fauna: Tribrachidium

Tribrachidium. UCMP
Tribrachidium, UCMP

One of these early experimental body plans from the Ediacaran fauna was a critter known as Tribrachidium.

Um.

The jury is out on precisely what Tribrachidium heraldicum is. It looks like a frisbee, and its strange tri-radial, spiral shape is unlike anything known today. According to the University of California Berkeley Museum of Paleontology, distant relationships to cnidarians and echinoderms have been proposed.

I still think it looks like a frisbee.

Ediacaran Fauna: Eoporpita

eoporpita
Eoporpita, UCMP

Another Ediacaran weirdie is this tentacled creature known as Eoporpita, which could either be a free-floating cnidarian polyp like an anemone, or a colony of polyps all glommed together. This latter description would place Eoporpita in a modern group called the chondrophorines.

Cambrian Explosion: Pikaia

"Pikaia gracilens B" by Apokryltaros - Own work. Licensed under CC BY-SA 4.0 via Commons
“Pikaia gracilens B” by Apokryltaros – Own work. Licensed under CC BY-SA 4.0 via Commons

Does this purple creature look anything like you or me?

Nah, not really.

Pikaia is an unusual invertebrate chordate, a creature that is distinctly different from us and yet has features that unite it, and us, with all other chordate animals. A post-anal tail, a notochord, pharyngeal gill slits, a dorsal hollow nerve tube; we all have these things as embryos, and little Pikaia had them, too. It’s like our great-great-great-wormy-grandmother. Sort of.

Cambrian Explosion: Olenellus

"Olenellus fowleri CRF" by Dwergenpaartje - Own work. Licensed under CC BY-SA 3.0 via Commons
“Olenellus fowleri CRF” by Dwergenpaartje – Own work. Licensed under CC BY-SA 3.0 via Commons

On ode to Olenellus: Oh, Olenellus. Without you, we would never know the top of the Lower Cambrian. Olenellus-zone, we thank you.

Right, I’m not a poet. But this species of trilobite is an important index fossil, used to piece together the ages of certain rock strata just by its presence. If you find Olenellus, you know you’re looking at rock from the Lower (Early) Cambrian.

Besides, trilobites are such a huge part of invertebrate paleontology, I had to include a nod to them here. They were once the most diverse life forms on Earth, spanning the world’s oceans, and all of them became extinct just before the dinosaurs made their first appearance. They are one of the groups of arthropods (relatives of insects, arachnids, and crustaceans) that are no longer around today.

Cambrian Explosion: Opabinia

"Opabinia smithsonian" by Jstuby at English Wikipedia - Transferred from en.wikipedia to Commons by FunkMonk using CommonsHelper.. Licensed under Public Domain via Commons
“Opabinia smithsonian” by Jstuby at English Wikipedia – Transferred from en.wikipedia to Commons by FunkMonk using CommonsHelper.. Licensed under Public Domain via Commons

Opabinia is one hell of a creature. It’s an arthropod, like insects and arachnids and crustaceans. But it’s so damn bizarre. Globular eyes and a long, vacuum-hose-like proboscis with pointed spines at the grasping end.

It seriously looks like a Taxxon from Animorphs.

The idea is that this swimming arthropod cruised through the Cambrian seas, picking up bits of food and using its prehensile hose-nose to grasp prey and maneuver the food to its mouth. The proboscis, or arm, or whatever-it-is was likely not a hollow tube.

 

"Burgess scale Cor" by Dinoguy2 (Corrected Miglewis) - Dinoguy2. Licensed under CC BY-SA 3.0 via Commons
“Burgess scale Cor” by Dinoguy2 (Corrected Miglewis) – Dinoguy2. Licensed under CC BY-SA 3.0 via Commons

Compared to some of its larger Burgess Shale brethren, like this big red Anomalocaris – another really cool aquatic and extinct arthropod – Opabinia was really quite tiny. It’s the green, 10-centimeter-long guy in the picture.

Cambrian Explosion: Hallucigenia

To wrap up, one of my favorite invertebrate fossils: Hallucigenia.

"Hallucigenia smithsonian" by Jstuby at English Wikipedia - Transferred from en.wikipedia to Commons by FunkMonk using CommonsHelper.. Licensed under Public Domain via Commons
“Hallucigenia smithsonian” by Jstuby at English Wikipedia – Transferred from en.wikipedia to Commons by FunkMonk using CommonsHelper.. Licensed under Public Domain via Commons

This creature really defied explanation for a long time, and it was unknown whether the spikes stood up on its back, or whether the spikes were legs…what was this animal, exactly? It is absolutely unlike anything we know of that’s alive today.

Here’s a recent reconstruction based on a cool paper where the head (YouTube) of this animal was finally found!

"Hallucinogenia" by Apokryltaros - Own work. Licensed under CC BY-SA 4.0 via Commons
“Hallucinogenia” by Apokryltaros – Own work. Licensed under CC BY-SA 4.0 via Commons

Aww. Aren’t they…cute?

In conclusion!

There are so many diverse and wonderful invertebrate fossils, I’ve only chosen a few favorites here. Invertebrate paleontology is a very broad field and there are so many cool ways invertebrate fossils can help us better reconstruct and interpret paleoecological environments. I tip my proverbial hat to my invertebrate paleontologist friends. Especially the conodont people. You know who you are.

Coming up next…What is Paleontology – Part 2: Vertebrate Paleontology

In which I wax philosophical about why I love bones, even though invertebrates are usually so much easier to collect in the field…sigh.

Did this clear up the definition of invertebrate paleontology? Do you have any neat (extant or extinct) invertebrate stories you’d like to share with us? Want to know more about really cool invertebrate fossils? Let us know below!

TBEX Fort Lauderdale: Six Lessons Learned
Society of Vertebrate Paleontology - 2015: Dallas, Dinosaurs, and Desmostylus