Natural Wonders: Stories from the Natural History Collection

An Ancient Fern

One of the fascinating specimens in our natural history collection feature is this fern (Pecopteris sp.) concretion. Similar to a fossil, a concretion is the preserved impression of a prehistoric organism formed from sediments before they harden into rocks. The genus Pecopteris’ name is derived from the Greek word pekin, meaning to comb, due to the leaflets of Pecopteris’ fronds resembling the teeth of a comb. All ferns are vascular plants meaning that they don’t have seed or flowers but instead they reproduce using spores. This specimen is from Illinois and is from the Pennsylvanian Period (323.2 – 298.9 million years ago). Ferns first appeared during the Devonian Period (419.2 – 358.9 million years ago); however, ferns in the genus Pecopteris became extinct in the Permian Period (298.9 – 252.2 million years ago) as a result of the Earth’s temperature dropping and the disappearance of swamps.

The movement of plants to land began during the Ordovician Period (485.4 – 443.8  million years ago), but their domination of terrestrial ecosystems didn’t really begin until the Devonian Period (419.2 – 358.9 million years ago). This time of rapid diversification is known as the Devonian Explosion. These plants began to spread out and began to form Earth’s first forests. Those prehistoric forests dramatically impacted many of Earth’s patterns including erosion rates, the carbon cycle, and the climate. There was also an increase in carbon burial during this period, which led to a decrease in the greenhouse effect and to several global cooling events. These cooling events are one of the proposed reasons for the Late Devonian extinction. 

This particular fossil was collected from a coal mine in Illinois. Most of the Earth’s coal and natural gas was created from the carbon burial events that happened during the Age of Ferns (the Carboniferous Period which took place 369-280 million years ago). Therefore, the anthropogenic use of these plant remains– the same plants that caused global cooling and the late Devonian extinction– is a key contributor to global warming today! It is vital that we learn from the Earth’s history and work to find greener sources of energy and fuel. In ensuring that we do not further impact our planet’s climate and weather patterns, we can help sustain life on Earth as we currently know it. 

American Oystercatcher Eggs

Lindsay’s vast natural history collection includes these American Oystercatcher (Haematopus palliatus) eggs. The American Oystercatcher is commonly referred to as the American pie due to its original name “sea pie.” In 1731, naturalist Mark Catesby renamed the bird from “sea pie,” to “American oystercatchers” after observing the bird eating oysters. Its genus name, Haematopus, is Greek for “blood foot,” which refers to the oystercatcher’s pink legs, and its species name Palliatus means “cloaked,” which refers to the black cloak of feathers on its head. 

As its name suggests, these birds commonly eat mollusks by stabbing their flat bill into partially open shells and severing the muscles that hold the shell together which allows the bird to be able to eat the soft inner parts. The bill is also used as a hammer to open a mollusk’s shell  allowing the bird to crack it open. Chicks often have to rely on their parents to feed them  because their beaks are not strong enough for them to pry open bivalves until up to 60 days after hatching. However, they are able to run within 24 hours of hatching!

American Oystercatchers can currently be found on the Atlantic coast of North America  to New England as well as on the Gulf Coast, the Caribbean, and even South in Brazil, Uruguay, and Argentina.  Current threats facing American oystercatchers include coastal development, pollution, disease, and invasive species. Due to this species’ loss of natural habitat as well as an increase in predation on more traditional ocean-front habitats, American oystercatchers have started to nest on spoil islands, marshes, and forest edges. The rise in sea level has also eliminated small islands that these birds used for nesting and roosting. By 1900, the American oystercatcher had been pushed out of areas north of Virginia and their remaining historic range—originally the entire Atlantic coast of the United States and the Labrador Peninsula of Canada—as a result of market hunting, egg collecting, and human disturbance. However, thanks to conservation efforts, in 1997 on Cape Sable Island, Nova Scotia in Canada, the first recent oystercatcher nest was confirmed. We can continue to help protect American oystercatchers by staying at least 50 yards away from nesting sites when visiting the beach and by supporting organizations and legislation that help protect this species’ coastal habitat.


An Ancient Coral Fossil

This striking specimen is a Horn Coral fossil. Horn Corals refer to any coral within the order Rugosa.  Their name is derived from the horn-like and wrinkled appearance of a solitary coral. Although they may not look like it, corals are a part of the kingdom Animalia — they’re animals! 

Horn Corals existed between the Ordovician and Permian periods, a range that began 485.4 million years ago and ended 251.9 million years ago. 

They went extinct during the Permian-Triassic extinction event — the largest extinction event to ever occur. This mass extinction, which occurred about a quarter of a billion years ago, wiped out roughly 95% of marine life along with 70% of terrestrial life.  

When thinking about corals, people commonly imagine coral reef ecosystem. These reefs are characterized by large colonies of individual coral polyps and the skeletal secretions produced by these polyps. The polyps sit inside stony cups, or calyxes, that they build while growing and catching plankton with the tentacles around their mouths. In addition to the plankton, corals receive nutrients from the zooxanthellae that live inside of them. Zooxanthellae are photosynthetic algae that give the corals their color, produce oxygen as well as sugars, and consume the CO2 produced by the corals. This mutualistic relationship is what drives the growth of coral reefs. Unfortunately, this endosymbiotic relationship is sensitive, and when coral gets stressed, the algae is expelled from the polyps. This process is referred to as coral bleaching. Without the zooxanthellae, the coral turns white and although it can continue to live and potentially recover, the coral will begin to starve and is more prone to disease. 

Rising ocean temperatures are one of the largest stress factors causing coral bleaching. Because corals are a keystone species to coral reefs, coral bleaching affects all other species in the ecosystem. Coral reefs provide natural protection to coastlines and provide homes and spawning sites for countless marine species. Without coral reefs, coastline communities along with wildlife would suffer. But there is hope. By working to mitigate climate change and reduce pollutants in the water, coral reefs can begin to thrive once again. 


Tarantula Diorama

One of the many fascinating objects in our collection is a tarantula (Aphonopelma sp.) diorama. The diorama displays a tarantula exiting its underground burrow with a fresh molt just outside the entrance. On the left side of the scene, a different tarantula is caught in a deadly dance with a female tarantula hawk wasp (Pepsis sp.). The tarantula is North America’s largest spider measuring up to 11 inches in height (including legs). Despite its appearance, the tarantula (Aphonopelma sp.) has very small venom glands containing mild venom that is only strong enough to paralyze small insects. To humans, its bite would feel no more painful than a bee sting. 

Tarantulas are nocturnal and spend most of their lives underground in burrows. Like other spiders, tarantulas shed their external exoskeleton periodically in a process called molting. For young tarantulas, molting occurs several times a year as they grow. The frequency will decrease to roughly once a year or less once maturity is reached. The molting process even also allows these spiders to replace lost appendages and internal organs. 

At around 4 to 7 years old, a male tarantula will reach sexual maturity, It will shed its exoskeleton for the last time, develop tibial spurs on its front legs, and will leave its burrow in search of a mate. Locally, mating season takes place from late August through early October, and several males can have been spotted in Mt. Diablo around this time in search of a mate. Once a male has located a female, he will rhythmically tap his pedipalps at the entrance of her burrow similar to knocking on a door. As she approaches, he will then use his newly grown tibial spurs as hooks to clasp the female’s fangs (in order to avoid becoming dinner) and begin mating. Afterwards, the male will scurry off to continue looking for other females to mate with, growing weaker and finally dying as winter approaches. The female, however, will live for around 20 to 30 years. After mating, she will return to her burrow to lay roughly 100 to 150 eggs, of which about two will make it to adulthood.

Tarantulas play a crucial role in their ecosystem acting as biological controls of insect populations, and as a source of food for other creatures such as mammals, lizards, birds and wasps. Tarantulas typically lie motionless by their burrows when hunting, waiting for the opportune moment to grab their prey and deliver a venomous bite. The venom will paralyze their prey, while they secrete a digestive enzyme that liquifies their meal so they can suck their food up through their straw-like mouth opening.

Despite their hunting prowess, tarantulas can also be an easy meal for larger predators. A tarantula’s primary defense mechanism is the barbed hairs on the back of their abdomen. It can shoot these hairs in the eyes and mucous membranes of its tormenter in hopes of scurrying away while the predator is distracted. The most feared predator of a tarantula is the large black and orange female tarantula hawk wasp (Pepsis sp.). This imposing insect seeks out tarantulas during late summer. When she locates a tarantula, the wasp attacks and delivers a paralyzing sting underneath the spider’s leg. The wasp then drags the tarantula to a hole and lays a single egg inside the tarantula before covering it. Once the larva hatches it will begin to feed on the still living tarantula, avoiding vital organs, which keeps its host alive and fresh. 

However, predators like the tarantula hawk wasp are not the only scary threats to tarantulas—humans can be too! Human threats to tarantulas include cars, habitat destruction, and collection. It is illegal in many parks (including Mount Diablo) to collect tarantulas as pets. So, if you see one out and about, feel free to observe it but let it continue to play its important role in the local ecosystem.