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.  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. 

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]”.

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.

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.