More than 100 million years ago, the boundary between land and sea may have been a little less distinct than it looks on a map.
uncertain
it → look → map
Along the ancient coastlines of North America, storms regularly swept marine material onto beaches, creating an unexpected source of food for animals living on land.
asserted
storms → sweep → land
A new research suggests that some dinosaurs and the animals they fed on may have taken advantage of this coastal buffet, incorporating nutrients that ultimately came from the ocean into their bodies.
uncertain
that → suggest → bodies
The finding offers evidence that marine and terrestrial food webs were connected during the Cretaceous, much as they are in some coastal ecosystems today, states a news report by Phys Org.
asserted
report → offer → Org
Following the carbon trail
The study, published in Frontiers in Ecology and Evolution, examined the chemical signatures preserved in fossil teeth.
asserted
study → follow → teeth
Researchers focused on carbon isotopes, particularly the ratio between carbon-12 and carbon-13, which can provide clues about an animal's food sources.
asserted
which → focus → sources
As per the study, pants growing on land generally have lower carbon-13 values than many marine plants.
asserted
pants → grow → plants
When animals consume them, those chemical signatures are carried through the food chain and can become locked into tissues such as tooth enamel.
asserted
signatures → consume → enamel
Dinosaur teeth, however, have long presented something of a puzzle.
asserted
teeth → present → puzzle
Their carbon isotope values are often higher than expected for animals relying entirely on land-based vegetation.
asserted
values → expect → vegetation
That raised the possibility that some dinosaurs, directly or indirectly, were consuming food that originated in the sea.
asserted
that → raise → sea
A prehistoric version of marine subsidization
The study provides the first evidence identified by the researchers for marine subsidization in prehistoric ecosystems.
asserted
study → provide → ecosystems
It also adds another layer to understanding how animals survived in the greenhouse climates of the Cretaceous.
asserted
animals → add → Cretaceous
The researchers examined fossils from ancient coastal environments associated with the Western Interior Seaway, a vast inland sea that divided North America during the Cretaceous.
asserted
that → examine → Cretaceous
They also studied material from the ancient Gulf of Mexico coastline and compared it with fossils from inland environments.
asserted
They → study → environments
The samples came from formations dating to two periods: roughly 113–107 million years ago and 100–96 million years ago.
asserted
samples → come → periods
Fossils included dinosaurs as well as fish and crocodiles, allowing the researchers to look for similar dietary patterns across different parts of the food web.
asserted
researchers → include → web
The results revealed a striking geographic pattern.
asserted
results → reveal → pattern
Fossils from coastal environments consistently showed higher carbon-13 values than those from landlocked sites.
asserted
Fossils → show → sites
The pattern appeared across different coastal locations and persisted across the periods represented in the samples.
asserted
pattern → appear → samples
That consistency suggests the signal was not simply the result of geological changes affecting fossils after burial.
uncertain
signal → suggest → burial
Instead, it points towards what the animals were eating.
asserted
animals → point → what
Seaweed emerges as the likely link
asserted
Seaweed → emerge → link
The researchers looked for a food source that could explain the chemical signature across animals occupying both marine and terrestrial ecosystems.
uncertain
that → look → ecosystems
The candidate needed to live along coastlines, remain available over long periods and sit low enough in the food chain for its carbon signature to reach both predators and large herbivores.
asserted
signature → need → predators
Marine algae and other aquatic plants fit those conditions.
asserted
algae → fit → conditions
Storms and tides can carry seaweed and other organic material from the ocean onto shorelines, where terrestrial animals can encounter it.
asserted
animals → carry → it
Herbivorous dinosaurs may have eaten the material directly, while other animals could have consumed prey that had already fed on marine resources.
uncertain
that → eat → resources
This would create a form of marine subsidization: nutrients produced in one ecosystem being transported into another and supporting animals there.
asserted
nutrients → create → another
Not every dinosaur joined the coastal menu
The evidence does not suggest that all dinosaurs regularly ate marine food.
asserted
dinosaurs → join → food
One notable exception was Tenontosaurus tilletti, a large herbivore whose carbon isotope values resembled those expected from animals feeding exclusively on terrestrial vegetation.
asserted
values → resemble → vegetation
That distinction is important because it indicates that the elevated carbon signatures were probably linked to dietary habits rather than a universal chemical alteration of dinosaur teeth.
asserted
signatures → indicate → teeth
In other words, some dinosaurs appear to have exploited the coastline, while others remained reliant on food produced on land.
asserted
others → appear → land
The study provides the first evidence identified by the researchers for marine subsidization in prehistoric ecosystems.
asserted
study → provide → ecosystems
It also adds another layer to understanding how animals survived in the greenhouse climates of the Cretaceous.
asserted
animals → add → Cretaceous
The findings are particularly significant because coastal ecosystems today continue to depend on exchanges between land and sea.
asserted
ecosystems → continue → land
Washed-up marine plants can provide food for insects, birds, mammals and other terrestrial organisms, especially when food on land becomes scarce.
asserted
food → wash → land
The fossil record suggests that this ecological relationship is far older than previously demonstrated.
uncertain
relationship → suggest → ?
More research is needed to establish whether the pattern extended to equatorial and polar regions, as well as to other periods such as the Jurassic and early Cenozoic.
asserted
pattern → need → Jurassic
For now, the fossil teeth offer a glimpse of an ancient coastline where the sea did more than shape the landscape.
asserted
sea → offer → landscape
…and 1 more, not listed.
The Aporia
