Around 5.5 million years ago, a series of gomphotheres, which are extinct relatives of elephants, perished in or near a river in North Florida. Despite the deaths occurring over a span of several hundred years, their bodies ended up in a single location, alongside other animals that met a similar fate.
Presently, the river no longer exists, but the remnants it left behind have provided paleontologists with a comprehensive glimpse into prehistoric life in Florida. In early 2022, scientists and volunteers initiated the excavation of the gomphotheres at the Montbrook Fossil Dig, leading to what is likely to be a groundbreaking discovery.
Jonathan Bloch, the curator of vertebrate paleontology at the Florida Museum of Natural History, expressed his enthusiasm, stating, “This is an extraordinary find that occurs once in a lifetime. It represents the most intact gomphothere skeleton from this era in Florida and one of the finest in North America.”
Initially, Bloch and his team stumbled upon fragments of a gomphothere skeleton during the spring of 2022. Given that isolated gomphothere bones had been previously discovered at Montbrook, there was no indication that this finding was anything extraordinary. However, a few days later, a volunteer digging nearby uncovered the articulated foot of an exceptionally large creature.
Dean Warner, a retired chemistry teacher and Montbrook volunteer, shared his experience, saying, “I started finding toe and ankle bones, one after another, as I continued to dig. Eventually, I unearthed the ulna and radius. It was evident to all of us that something remarkable had been discovered.”
Within a short span, it became apparent that there were not just one, but several complete skeletons, including an adult and at least seven juveniles. The exact size of the specimens cannot be accurately determined until the research team completes the excavation process. However, Bloch estimates that the adult gomphothere stood at eight feet tall at the shoulders, while the skull, with the tusks included, measured over nine feet in length.
Rachel Narducci, the collection manager of vertebrate paleontology at the Florida Museum, suggests that the fossils found at Montbrook were likely deposited or transported to the area in successive events. She explains, “Modern elephants travel in herds and can be very protective of their young, but I don’t think this was a situation in which they all died at once. It seems like members of one or multiple herds got stuck in this one spot at different times.”
Excavations have been taking place at Montbrook since 2015 when Eddie Hodge contacted researchers at the Florida Museum about fossils found on his property. The site’s fine sands and compacted clays have revealed a layer cake of fossils, reaching depths of up to nine feet in certain areas.
Although the fossil beds are now located 30 miles inland from the Gulf of Mexico, during the late Miocene, when the bones were deposited, the area was much closer to the sea. At that time, temperatures and sea levels were higher than they are today. Consequently, the remains of camels, rhinoceroses, llamas, as well as freshwater and saltwater fish, turtles, alligators, and burrowing shrimp, are found together. Additionally, due to the presence of limestone from a previous marine environment, fossils of older marine species like sharks are occasionally discovered.
In the past seven years, paleontologists at Montbrook have made remarkable discoveries, including the oldest deer in North America, the oldest known skull of a smilodontine sabertoothed cat, and a new species of extinct heron. Other well-known prehistoric creatures such as bone-crushing dogs and short-faced bears are also found scattered throughout the fossil bed. However, most of these animal remains are fragmented and dispersed, having been transported by running water. The finding of several complete gomphotheres was entirely unexpected.
“We’ve never encountered anything like this at Montbrook,” remarks Narducci. “Usually, we only find isolated parts of a skeleton at this site. The gomphotheres must have been rapidly buried or trapped in a river bend with reduced flow.”
Proboscideans, which include elephants and their extinct relatives, have historically been present on nearly every major continent. Gomphotheres, specifically, were among the most diverse members of this group. Unlike their more famous counterparts, the woolly mammoths, which emerged and disappeared around the time of the Pleistocene ice ages, gomphotheres have an extensive fossil record spanning over 20 million years.
Gomphotheres originated in Africa during the early Miocene, approximately 23 million years ago. From there, they dispersed into Europe and Asia. Around 16 million years ago, they reached North America by crossing the Bering land bridge. When the Isthmus of Panama emerged from the sea 2.7 million years ago, gomphotheres were present on the shoreline, ready to migrate into South America.
During their evolutionary journey, gomphotheres developed unique characteristics that allowed them to adapt and thrive in the diverse environments they encountered. While mastodons and woolly mammoths are relatively recognizable, gomphotheres present a greater challenge when it comes to classification. They exhibited a range of body sizes, and the shape of their tusks varied significantly between species.
In addition to the typical upper tusks found in proboscideans, some gomphotheres possessed a second set of tusks attached to their lower jaw. These lower tusks evolved into increasingly unusual configurations through natural selection. Many species had small lower tusks that diverged or extended parallel to each other at the tips of elongated jaws. The platybelodon gomphotheres had flattened and fused tusks, resembling a large pair of buck teeth, which they used for stripping bark from trees.
Paleontologists often rely on these tusks as distinguishing features. The gomphotheres found at Montbrook exhibit a distinct spiral band of enamel along the length of each tusk, giving them the appearance of a barber’s pole. This unique banding pattern was only present in one group of gomphotheres during that period. As a result, Bloch and Narducci were able to narrow down the identity of the Montbrook fossils to species within the genus Rhyncotherium, which were once widespread across North and Central America.
Bloch explains, “Another fossil site in southern California is the only place in the United States that has yielded a large sample of Rhyncotherium juveniles and adults. We are already gaining valuable insights into the anatomy and biology of this group that were previously unknown, including new information about the shape of their skulls and tusks.”
Gomphotheres thrived in the open savannahs that were widespread in Africa, Eurasia, and the Americas. However, a global cooling trend that began approximately 14 million years ago led to the expansion of vast grasslands, gradually replacing the savannahs. This shift had a negative impact on gomphothere diversity. While some species managed to adapt their diet from browsing on trees to primarily consuming grasses, gomphotheres faced further challenges at the end of the Miocene when mammoths and elephants emerged.
Mammoths and elephants originated in Africa and migrated north into Eurasia, following the footsteps of the gomphotheres and ultimately displacing them. By the time humans arrived in the Americas, only a few gomphothere species remained, and their survival was short-lived. The last gomphotheres vanished during the ice ages, along with many other large mammal species, due to rapid climate change and overhunting by the newly arrived human populations.
The discovery at Montbrook revitalizes interest in Rhynchotherium gomphotheres and offers scientists an opportunity to gain further insights into the fascinating fauna that once inhabited North America.
One of the highlights of the Montbrook excavation has been the involvement of numerous volunteers from across Florida, as Bloch explains, “Sharing this process of discovery with volunteers from all over the state of Florida has been immensely rewarding. Our aim is to assemble this massive skeleton and put it on display, where it can stand alongside the iconic mammoth and mastodon already showcased at the Florida Museum of Natural History.”