Prehistoric Wild: Life in the Mesozoic

Guardian From the Deep (86 MYA)

Niobrara Formation, Nebraska, 86 Million Years Ago

    In western North America lies a vast, shallow sea. Running from the Arctic Ocean to the Gulf of Mexico, it splits the continent in two. To the west is Laramidia while the east has become Appalachia. Between these land masses, the modern states of Texas, Colorado, Wyoming, and the Dakotas lie sunken in this Western Interior Seaway. What we now call Nebraska is almost entirely engulfed by ocean water, an apt condition for a state whose name is Sioux for "broad waters."

    However, a small stretch of land remains on the coast of this widespread inland sea. Here, shallow waters flow through a series of jagged stones. Waves crash against many of the larger sharper rocks, creating explosions of foamy liquid. This disturbs the ancient sea-gull-like birds, Ichthyornis, that roost atop these pointed boulders. Their high-pitched, piercing screeches cut through the sound of the crashing tide.

What little sea water makes it through bounces on the flat, rocky outcrops on the coast's edge. These cliffs act as a border between shallows and the sandy beach above. Colonies of slimy green algae cling to the edges of these coastal rock barriers. This stone stretches across the expansive Appalachian seaboard as far as the eye can see.

    It's along this outcrop that groups of one of the seaway's strangest animals emerge from the water. Dragging themselves onto the wet stone are flocks of Hesperornis. They are an ancient lineage of flightless sea birds native to the North American waters. These 6-foot avians sport large bodies with small, barely visible wings, a short tail, and elongated, web-footed hindlegs. Their necks are slender and curved like that of a heron. The heads supported by these necks are also lengthy, ending in a dagger-like beak lined with small, sharp teeth, a rare sight among birds in our modern day.

    Their bodies are adorned with thick, water-proof plumage. Much of it is glossy, black while the fronts of their necks, breasts, and bellies are completely white. Bright yellow, eyebrow-like feather crests grow out from above their eyes. Faded pink, scaly skin coats their exposed legs in addition to the bright, orange-red of their beaks.

    Like penguins and many other modern birds of a similar niche, Hesperornis spend much of their time out at sea. It's only on rare occasions that these marine fowl drag themselves onto dry land. Unlike the penguins, ducks, or geese that we are familiar with, their feet aren't strong enough to support their weight out of the water. Instead, their terrestrial movement is much more akin to a seal. Their legs push and drag their bodies in multiple short bursts. Such motion tends to be difficult when traversing up the side of the beach stone.

Nonetheless, their efforts successfully bring them to the sands behind all the moist rocks. They're immediately greeted by the expansive, sandy shores at the edge of dry land. The soft light of the mid-morning sun illuminates the white beach sand. Here, rocks are still present, but in fewer numbers and buried by the smooth, tropical grains. Pieces of broken shells are mixed in too, brought in by much higher tides of the past. Bordering the land and the beach is a wall full of ferns and tall plants resembling today's palm trees. Amidst the warm winds, the air here is a sweltering 90 degrees Fahrenheit. Even 50 feet away from the tidal rocks, the crashing of waves can still be heard amidst the oceanic breeze.

The approaching Hesperornis are also welcomed by the honks, trumpets, and squawks of other members of their kind. Hundreds of these aquatic birds lay on bundles of brown, thin sticks across this enormous beach. These are males waiting for the arrival of their returning mates.

Upon reaching the colony, each of the females lets out calls like those of the males. Hesperornis can't identify each other by looks largely due to being identical. Instead, they recognize one another by their unique vocal characteristics. To human ears, these calls are almost indistinguishable. However, these birds can spot even the most minute differences that are unique to each individual. Such recognition among birds has become such a successful evolutionary trait that it's even seen long after the Cretaceous. It's the very thing that helps females like Jane to stand out, even amongst the calls of hundreds of others.