Collections Close-Up: Fur Seal Fossil Focus

partial cranium and frontal skull region of the ancient pinniped Thalassaleon macnallyae

The Central Coast is packed with pinnipeds for all seasons. From regular sightings of harbor seals and seal lions, to special occasions like elephant seal breeding season, which wraps up at the end of this month. An even more special sight would be northern fur seals, who spend more than 300 days a year out at sea. An even rarer sight would be their extinct ancestors, if it weren’t for your neighborhood natural history museum’s fossil display!

Out from its permanent home in our local paleontology exhibit for a closer look this month, this fragmentary fossil is a partial cranium and frontal skull region of the ancient pinniped Thalassaleon macnallyae. Compare this specimen to modern pinnipeds, including their descendant the northern fur seal.  Thalassaleon means sea lion in Greek, and is the name of an extinct genus of the family otariidae. Otariidae, including fur seals and sea lions, are a group of carnivorous semi-aquatic marine mammals with flippers and visible external ears. Together with Phocidae, the earless or true seals like harbor seals, and Odobenidae, whose only living member is the walrus, and the extinct Desmatophocidae family, these families make up the clade of pinnipeds. 

partial cranium and frontal skull region of the ancient pinniped Thalassaleon macnallyae, with the braincase in the back

This fossilized cranium, which belonged to an immature individual, was collected but not identified from near Soquel Point by teenager Gerald Macy in the late 1930s or early ‘40s. Many fossil hunters have cut their teeth collecting along the Opal Cliffs, and Macy was no exception. In 1939 the local paper described the then 17-year old as “the local authority on paleontology, a position attained by more than five years painstaking search of the rich stratas [of the cliffs]”.

Newspaper clipping regarding Gerald Macy, 17-year-old palentologist

While the cliffs of Capitola have exposed countless fossils for science, they are special for this species: Thalassaleon macnallyae has only been found in exposures of the Purisima formation in Central and Northern California. The first of its kind to be formally described was uncovered in Point Reyes by paleontologist Kathleen MacNally Martin in 1965. As a whole, this species has a geochronologic range of 6.9-5.33 Ma.

As the ancestor of the modern northern fur seal, this specimen represents millions years of life in Santa Cruz. Today its descendants spend most of their time on the open ocean where they feed on a variety of fish and squid. They come ashore to reproduce and molt on rocky or sandy beaches of islands in the eastern North Pacific and Bering Sea, including California’s San Miguel Island and South Farallon Island. In the 19th and early 20th centuries, they were hunted for their luxurious pelts: their insulating fur boasts 46,500 fibers per square centimeter. Although they are now protected, they face threats from debris entanglement, fisher interactions, and climate change throughout their range. 

Our ancient fur seal specimen’s story doesn’t stop with its own descendants – it also has a role in putting together the puzzle pieces of pinniped evolution. Its measurements, along with those of a variety of other pinniped fossils, were used by paleontologists Robert Boessenecker and Morgan Churchill in 2015 to identify an older species of fur seal – Eotaria crypta, the oldest discovered otariid specimen. 

Boessenecker was looking through pinniped fossils at the Cooper Center in Orange County in 2012 when he spotted a small fur seal jaw whose identification seemed at odds with the age of the rock formation in which it was found. He suspected that the specimen might represent a missing link between otariids and the ancient ancestor of pinnipeds from which they diverged.

To confirm, the paleontologists analyzed more than 115 morphological features from specimens representing more than 23 taxonomic groups, including the star of this month’s Close Up. By preserving fossils like the remains of Thalassaleon macnallyae as well as others, our collections can further our understanding of the history of life on earth. 

We couldn’t do that without the paleontologists who put in the work to study our collections, and we were thrilled to talk to California native Robert Boessenecker about what that process looks like. 

He says that the decision to study a fossil begins with how interesting it is – whether it helps tell a story,  fill a hole in current knowledge or has unusual features or strange preservation. From there it takes a combination of fieldwork, fossil preparation, museum visits, and data collection to understand a fossil’s significance.  

Boessenecker, who teaches at the College of Charleston and blogs about his research, is no stranger to SCMNH. Bobby, as he is often referred to in our records, has been hunting for fossils in Santa Cruz since he himself was a teenager, and has gifted some of his finds to our museum. This kind of collection, he says, is perhaps unique to the field of paleontology – how easy it is for community scientists (e.g. amateur fossil collectors) to make serious contributions to science.  

Stop by this month to check out one such contribution – our fossil fur seal in focus.

Collections December 2019: Fossils and Field Experiences

Whale ear bone

This December’s Collections Close Up features a familiar face, rather, fossil. We’re highlighting a whale ear bone that lives in our permanent fossil exhibit, currently under wraps for the final month of our Sense of Scale exhibit about earthquakes, Loma Prieta, and seismologist Charles Richter. In doing so we are also able to explore the locale from which this fossil was uncovered through a virtual field experience of the Purisima Formation. 

About the size of an oblong, to the casual observer this specimen might look like a cross between a seashell and a shriveled nut. It is in fact the ear bone of an ancient whale of unknown species. More specifically, it is a tympanic or auditory bulla, a bony capsule enclosing and protecting delicate parts of the middle ear. 

In humans, sound waves are funneled through the fleshy outer ear down the ear canal to the eardrum, where this bony protection is part of the temporal bone of the skull. This system works well in the air, but as anyone who has gone swimming knows, not so well in water. Part of the reason sound comes out garbled is because of the connection of the ear bones – your skull and your eardrums are all vibrating in response to sound waves at the same time, rather than in sequence, making it difficult to pinpoint the garbled sound’s origin. 

For cetaceans, the category of marine mammals that includes dolphins and porpoises, that just couldn’t cut it. These creatures evolved about 50 million years ago from a terrestrial mammal that looked something like a small hippopotamus. When it comes to life in the water, sound is a much more effective sense than light for communication, hunting, and finding your way. They have no external ear openings, and instead of sound waves traveling through an ear canal, they rely on pads of fat in their jaws to amplify vibrations from the water.

For a more in depth discussion of fossil whale ear bones, check out the Virginia Museum of Natural History’s paleontology blog. This article describes just one example of how scientists can learn a ton from this relatively small bone found in large creatures. In addition to shedding light on the ancient ancestors of whales, the study of these bones can illuminate how it came about that toothed whales hear best at high frequency ranges while baleen whales hear best at low frequency ranges, how it may be the case that some whales hear well at both, and more.

Our fossil was found in 1973, embedded in a chunk of Purisima Formation exposed along the Capitola Coast dating between 3 to 7 million years old. In general, museums and paleontologists are careful about how we track and provide access to information on where fossils are found in order to help preserve as much scientific information as possible while also protecting fossil discovery sites for science and the public. At the same time, this caution is balanced with a commitment to educate and share information about these same discoveries. An exciting example of educational outreach featuring the same general area where this ear bone was found is the Eastern Pacific Invertebrate Communities of the Cenozoic partnership’s Virtual Field Experiences initiative.

These virtual field experiences are richly immersive presentations of text, image, and video that serve as online excursions to different classic paleontological sites. So far there are two VFE’s, with more on the way. The first focused on the Kettleman Hills on the western edge of the central valley,  Fortunately for us, the second focuses on two areas on the central coast where the Purisima formation can easily be observed – at Moss Beach in San Mateo County and at Capitola Beach here in Santa Cruz County.

The whole project is a National Science Foundation funded effort involving several institutions, including folks at UC Berkeley and the Paleontological Research Institute, to increase public access to Cenozoic marine invertebrate fossils along the Pacific coast of the Americas. And while that means the focus is more on the fossils of creatures like clams and sea snails than vertebrate specimens like our whale ear bone, the project pages are a rich trove of information on everything from the nature of fossils, to best practices for ethical collecting, to the journey of fossils from field sites to museum collections. 

This last part is particularly exciting for us, as we work on increasing access to our own collections. And while EPICC and their VFE’s are part of an enormous, national, and multi-institutional effort, they still serve as an incredible model of how many different ways digitized collections can reach people. In the meantime, stop by the museum this month to see this ancient ear bone front and center in the Collections Close Up display.

Collections February 2019: A Puzzle from the Pleistocene

Mammoth tooth
Partially fragmented, the long ridges of this mammoth tooth once ground grasses and sedges much like cattle do today.

In January, we looked at rocks from our oldest collection. Today, we explore the Museum’s newest fossil: a fragment of a locally-discovered tooth that belonged to a Columbian mammoth. Not only is this an exciting specimen for the Museum’s Collections, it also brings into the public sphere another piece of what local paleontology expert Frank Perry describes as the “giant jigsaw puzzle” of paleontology.

The tooth is about the size of a half-gallon of milk. On its crown you can see ridges that would, some hundreds of thousands of years ago, grind grasses and sedges much like cattle do today. Mammuthus columbi was primarily a grassland grazer. These grinding teeth grew in sets of four, and were replaced several times throughout the animal’s life, just like in elephants. Its enamel plates are slightly tilted, which helped to keep the teeth sharp as they wore down.

The Columbian mammoth was one of several mammoth species that lived during the Pleistocene, about 2.6 million to 11,700 years ago. It would have appeared in North America about one million years ago, where its range stretched from Canada down to Nicaragua and Honduras. In contrast to the thick coat of its relative the woolly mammoth, the Columbian mammoth probably did not have much hair.

Fossilized mastodon tooth
Notice the more pronounced cusps of this fossilized tooth from a mastodon, a distant cousin of the mammoth. This difference helped mastodons to feed on woodier plan material, like trees and shrubs.

They stood up to 14 feet high at the shoulder and 13 to 15 feet long, with tusks up to 16 feet long. These animals may have weighed between 18,000 and 22,000 pounds, just under the weight of a school bus. Compare a tooth from a mastodon’s skull to this mammoth, and you’d notice higher cusps: an indicator that mastodons ate woodier shrubs and trees.

Our newest tooth was given to the Museum by longtime friend Frank Perry. In a recent email titled “Mammoth Puzzle,” Frank wrote to say he received a piece of tooth that was collected several decades ago at an excavation in Watsonville, and could it be the missing part of a similar tooth from the same area, already in the Museum Collections?

Here he was referring to the 1973 discovery of a Columbian mammoth tusk, a whole tooth (weighing a whopping 10 pounds!), and a smaller tooth fragment. With great excitement, we scheduled an appointment to compare the two partial teeth to see if we indeed had a match.

Fortunately for us, Frank Perry loves to share. He sat down with us to offer some of his personal history studying Santa Cruz County’s fossils, and that includes several mammoth finds over his career. Often these discoveries have been teeth, which are so huge and durable that they often outlast the rest of the animal’s body.

It’s fairly common, Frank says, for these discoveries to happen at construction sites or coastal cliffs, or any place where ancient sediments get exposed. And while our two teeth were not a match, we weren’t wrong to hope: Frank points out that in the history of paleontology, after someone finds a fragment, it sometimes takes “50 or 100 years before a fossil is found that shows what the rest of the animal looked like.” Paleontologist Charles Repenning, for example, found the remaining parts of a fossil pinniped — a relative of modern sea lions — more than half a century after the original fragment was discovered.

Part of the reason these mammoth teeth are so cool is because most fossils found in Santa Cruz are marine. Many people have found seashells, whale fossils and pinniped parts. However, they’re also interesting because they represent the contemporary set of large animals, or megafauna, that lived during the Pleistocene.

Mammoths and mastodons weren’t the only megafauna to stomp the landscape — camels, giant ground sloths and saber-tooth cats also roamed North America. To learn more about the Pleistocene Epoch and its animals, check out the University of California Museum of Paleontology. For those who still wonder how the Museum’s new tooth — and paleontology in general — might matter to their lives, Frank makes an excellent case for the joys of exploring the deep past.

“Everyone is curious about their own genealogy,” he says. “Paleontology is nature’s genealogy.” Whether learning how changing climates have shaped our lands or tracing evolutionary relationships between extinct species, paleontology can tell us more about how we came to be. And one way to fill in the gaps of our past, Frank says, is careful observation.

“In paleontology,” Frank says, “you often hear the statement, ‘the present is the key to the past.’ By looking at modern day plants, animals and geologic processes, we can better understand the past. But observation is also a key to the past. Learning to see these things — that takes practice.”

May 2018: Paleobotany

Spring is coming along nicely at the Museum. We’re super excited about our blooming garden and growing programs related to native plants. For May’s Collection Close-Up, we have arranged a tour of our fossil plant garden. Rather than heading outside, this garden tour will take us into the paleobotany shelves of our paleontology cabinets.

Paleobotany, or fossil plants, is an interdisciplinary field relying on both botanical and geological expertise to investigate questions related to the evolution and natural history of plants. By studying fossil plant material, paleobotanists learn about the ancient organism and also delve into questions such as whether the specimen has close living relatives, how the fossil’s anatomy compares to that of modern plants, what the specimen can tell us about the relationship of different layers of rock and what the specimen can tell us about the the environmental conditions in which it lived.

Not all plant material is resilient enough to be preserved; often it decays or is consumed before it can be buried (and be on its way to fossilization). As a result, plant fossils typically consist of parts of the plant — most commonly, individual leaves or stem pieces. They are also often  preserved as imprints of the original specimen in the rock which holds them instead of preserved material itself. There is still surprisingly a lot of information you can gleam from incomplete fossil plants — from size and shape of the fossil to specific structures, such as veins, thorns and even individual cells under the right magnification.

Here are some of the beautiful specimens from our fossil garden and the stories they tell:

Foissilized Cordia leaf
Cordia leaf

Cordia leaf (Monterey Formation, Miocene epoch). Leaf fossils are the most common macroscopic remains of plants. With its clear leaf shape and veins, this specimen can be identified as a member of the Cordia genus.

Fossilized stem
Stem

Stem (Monterey Formation, Miocene epoch). This impression of a stem was found by a Soquel High student in the 1970s. If you look at it closely, you can see the impressions of the plant’s thorns, which are identified in this image by white arrows.

Fossilized Annularia leaf
Annularia leaf

Annularia leaf (Francis Creek Shale, Pennsylvanian epoch). This distinctive whorl of leaflets along a stem belongs to a member of the extinct Calamites family, a tree-like relative of modern horsetail plants. This specimen is one of several in our collection (like the one below) from the Francis Creek Shale, a famous fossil locality known for its unusual preservation of soft-tissued organisms within rounded nodules of rock.

Fossilized fern leaf
Fern leaf

Fern leaf (Francis Creek Shale, Pennsylvanian epoch). This beautiful impression of a fern is another great example from the Francis Creek Shale. Both fossil ferns and sphenopsids (like Annularia above) are commonly found within the rock formation, as are a wide variety of uniquely preserved land and marine fauna.

For a closer look at these fossils, as well as other exhibits and gardens, stop by the Museum through June to look our Collections Close-Up.