Dinosaur-Era and Pre-Dinosaur-Era Sea Creatures

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Turtles, crocodiles and sharks are among the survivors of the dinosaur age that can be found in the ocean today. Some species predate it. Trilobites first appeared about 500 million years, They “were a dominant part of life in the sea for 200 million years, 100 times longer than man has existed.”

Leatherback turtles are the world’s largest and fastest reptile, and the most ancient and fastest-swimming turtle. Their have been around for 100 million years, surviving the asteroid that wiped out the dinosaurs 65 million years ago.

Crocodiles have been around for 240 million years, appearing 25 million years before the first dinosaurs and 100 million years before the first birds and mammals. Crocodiles that lived 230 millions years ago were up to 40 feet long. "Our primate ancestors were ratty little things that went around stealing eggs," Dr. Perran Ross, a crocodile specialist and professor of wildlife ecology and conservation at the University of Florida, told the New York Times. "Ancestral crocodiles had basically the same body plan we see today, apparently because it works."

Websites and Resources: Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; “Introduction to Physical Oceanography” by Robert Stewart , Texas A&M University, 2008 uv.es/hegigui/Kasper ; Fishbase fishbase.se ; Encyclopedia of Life eol.org ; Smithsonian Oceans Portal ocean.si.edu/ocean-life-ecosystems ; Woods Hole Oceanographic Institute whoi.edu ; Cousteau Society cousteau.org ; Monterey Bay Aquarium montereybayaquarium.org ; MarineBio marinebio.org/oceans/creatures

Oldest Forms of Ocean Life Still Found Today

Brachiopods are shelly marine animals with long, fleshy stalks that live in burrows on the seafloor. Alice Clement writes: They act as reef-dwelling organisms, filter-feeding from the water around them. Brachiopods living today, such as Lingula, look more or less the same as their Cambrian counterparts from about 500 million years ago! They are considered the oldest known animal (genus) that still contains living representatives. In The Origin of Species, Darwin noted “some of the most ancient...animals as...Nautilus, Lingula, etc., do not differ much from living species”. It’s these observations that led him to propose the term “living fossil” (See Below). [Source: Alice Clement, Research Associate in the College of Science and Engineering, Flinders University, The Conversation October 10, 2022]

Crinoids are known from at least the Devonian (359-419 million years ago) but may have existed as long ago as the Ordovician (more than 445 million). These marine animals, also known as “sea lilies”, once lived on the seafloor in a symbiotic relationship with corals. Corals grew off the stalks of crinoids to reach higher into the water column for better feeding opportunities. This association was very common until it seemingly stopped appearing in the fossil record about 273 million years ago. However, in 2021 these two marine creatures were rediscovered in Japanese waters, thriving in a blissful aquatic partnership. It remains a mystery why no fossil evidence of this happy marriage had been found for the intervening period.

Sponges are about the simplest animals on the Earth. And they might be the oldest ones too by 70 million years according to a study published in 2010 by Adam Maloof and colleagues in Nature Geoscience. Discover News reported: “ In Australia, Maloof says, the team found remains of ancient sponges dating to about 650 million years ago. The prior oldest known hard-bodied animals were reef-dwelling organisms called Namacalathus, which date to approximately 550 million years ago. Disputed remains for other possible soft-bodied animals date to between 577 and 542 million years ago. [Discovery News, August 2010]

Limestone traces of 3.5 billion year old stromolites have been found at a place in Western Australia ironically called the North Pole. These organisms lived at a time when the earth's atmosphere was composed mostly of carbon dioxide, or in other words an atmosphere more similar to the one on Mars than the one on earth today. Through photosynthesis, stromolites and other plants created the oxygen we now breath today. Stromolites, almost exactly the same as their 3.5 billion year old ancestors, can also still be found in Western Australia.≤

Living Fossils in the Ocean from the Dinosaur Age

The first dinosaurs appears about 230 million years Alice Clement wrote: In his 1859 book “On the Origin of Species”, Charles Darwin coined the term “living fossil” to describe living organisms that appeared unchanged from their extinct fossil relatives. The term has since been used to describe long-enduring lineages, relict populations, groups with low diversity, and groups with DNA that has hardly changed in millions of years. The marine depths seem to be a good place for “living fossils”, with cartilaginous fish such as sharks and rays generally being 2-4 times more evolutionarily distinct than land animals. In other words, while every species is unique, these species are particularly unlike their closest relatives. [Source: Alice Clement, Research Associate in the College of Science and Engineering, Flinders University, The Conversation October 10, 2022]

Striped Panray (Zanobatus schoenleinii) have a median “evolutionary distinctiveness” age of 188 million years. Many cartilaginous fish tend to be highly evolutionarily distinct, but the striped panray takes the top spot. Today, the striped panray lives in tropical waters in the eastern Atlantic (and possibly the Indian) ocean, and feeds on small invertebrates from the ocean floor. It belongs to the order Rhinopristiformes and is ovoviviparous, meaning it gives birth to live young. It is listed as “vulnerable” by the International Union for Conservation of Nature.

Nautilus pompilius
Nautilus are a type of marine cephalopod mollusc, and are therefore related to squid and octopus. However, unlike other cephalopods, they are housed within a distinctive smooth, hard shell. Nautilus live in the open water in and around coral reefs in the Indo-Pacific Ocean. They’re hunted for their beautiful shells to make art and jewellery, but international trade is now regulated to protect them from over-exploitation. Members of the Nautilidae family are known to have existed from the Late Triassic, and appear to have remained relatively unchanged for more than 200 million years. Darwin himself described these creatures as “living fossils”. You’d struggle to tell an ancient Nautilus from a living one.

Mantis Shrimps, also called stomatopods, are distinctive crustaceans found in tropical and subtropical coastal waters around the world. They are fearsome marine carnivores known to deliver a dizzyingly fast and painful blow, with the fastest self-powered strike in the animal kingdom. They also live a colourful life. During mating season they fluoresce (emit light) and have complex eyes to watch these displays. In fact, they have up to 16 colour receptors, whereas humans have just three. The mantis shrimp lineage branched off from other crustaceans in the malacostraca class (such as crabs, lobsters and krill) during the Carboniferous, around 340 million years ago. So these fabulous, feisty critters have been flourishing for a long time. Today there are hundreds of species belonging to the suborder Unipeltata, which appeared some 190 million years ago.

Palauan Primitive Cave Eel (Protanguilla palau) is a pruplish, ribbonlike fish with anatomical features not seen in other eels for 140 million years. Placed in a new family of fish at it was discovered in 2009 in a reef cave in Palau, it has an upper jawbone, characteristic of its Cretaceous period eels. It also only has 190 vertabrae, an even more primitive feature. Other features have raised doubts as to whether it is really an eel but molecular and anatomical analysis indicated it is. [Source: John Briley, National Geographic]

The Palauan primitive cave eel is 4.3 to 18 centimeters (1.7 to 7 inches) long. According to Smithsonian,org: A Japanese research diver, Jiro Sakaue, found the first specimen in February 2009, in a cave of a reef near Palau. After extensive morphological and DNA analysis, Smithsonian ichthyologist David Johnson and colleagues from Palau and Japan determined that the genus and species belongs to a new family of eels called Protoanguillidae. Unlike all other known species of eel, Protanguilla palau has a fully developed set of toothed gill rakers. These bony structures help retain food. The team published its findings online in the Proceedings of the Royal Society B on August 17, 2011. The fish has an evolutionary history that dates back some 200 million years. Because of this and the fact that it has retained some primitive features, scientists are recognizing it as a 'living fossil.'

Living Fossils That Predate the Dinosaur Age


Coelacanths are fish that live deep off the coasts of Africa and Indonesia. Alice Clement writes: They have unusually shaped paired body fins which they move alternatively, almost as if they’re “walking” underwater. Their lineage stretches back to the Devonian Period, at least 410 million years ago. It was once thought coelacanths had gone extinct alongside (non-bird) dinosaurs about 70 million years ago, as they disappear from the fossil record around this time. So imagine the surprise when a living specimen was dredged up from the deep ocean in 1938! This fish became known as “Old Fourlegs” and was thought to be the direct fishy ancestor of all land animals (although we now know this isn’t strictly correct). Today there are two living coelacanth species, known as Latimeria, which have basically remained unchanged over the past 100 million years. [Source: Alice Clement, Research Associate in the College of Science and Engineering, Flinders University, The Conversation October 10, 2022]

Horseshoe Crabs are ancient creatures that first appeared at least 480 million years ago during the Ordovician Period and don’t appear to have changed much since. They are not crabs at all, but “chelicerates” and therefore more closely related to spiders and sea scorpions. There are four species alive today, all within the family Limulidae, found in waters off Asia and North America. They migrate to shallow coastal waters to breed in massive “orgy” events, with females laying many tens of thousands of eggs in the sand. They also have strange blue blood, coloured that way due to a high copper content. Horseshoe crabs are harvested for their blood by the pharmaceutical industry since it has uses in biomedical testing.

“While animals described as “living fossils” usually do continue to evolve, many of these changes are imperceptible to the human eye. To track how animals change over time, we look at molecular changes visible in the genes, or “morphological” changes to the physical form. Internal (or molecular) drivers include genetic drift, which is the random change in the frequency of gene variants in a population over time. External forces include natural selection, in particular sexual selection, which lead to specific traits being inherited in a population over time. The marine animals listed here seem to be undergoing morphological stasis (slowing or stoppage). Some may have molecular stasis too. Their slowing rates of evolution are likely a result of the relatively stable environment underwater, particularly in the deep sea. These distant refuges are some of the least affected by direct human impacts and changes in weather and climate.

World Earliest Sharks

goblin shark
According to the Natural History Museum: The earliest fossil evidence for sharks or their ancestors are a few scales dating to 450 million years ago, during the Late Ordovician Period. Emma Bernard, a curator of fossil fish at the Museum, says, 'Shark-like scales from the Late Ordovician have been found, but no teeth. If these were from sharks it would suggest that the earliest forms could have been toothless. Scientists are still debating if these were true sharks or shark-like animals.'

Goblin Sharks (Mitsukurina owstoni) are bizarre animals with a long, flat snout and toothy jaws that protrude in front of the face to catch unsuspecting prey. Goblin sharks are rarely seen by humans. They are relatively rare deep-water shark living in all major oceans. Described as “grotesque” when first encountered in 1910, the goblin shark is the only living representative of its family, Mitsukurinidae, and is the most evolutionarily distinct shark we know of; its lineage stretches back some 125 million years. [Source: Alice Clement, Research Associate in the College of Science and Engineering, Flinders University, The Conversation October 10, 2022]

Elephant Sharks (Callorhinchus milii) are also known as the Australian ghost shark but their name is a misnomer. They are not sharks. They are related type of cartilaginous fish known as a “chimaera” and belongs to a subclass called Holocephali which diverged from the shark lineage more than 450 million years ago. These “plownose” chimaeras take their name from their bizarrely shaped snout and can be found living off the continental shelves of Australia and New Zealand. Analysis of their genome has shown the species changes at a veritable snail’s pace. In fact, it has the slowest evolving genome of all vertebrates, with its DNA almost imperceptibly altered over hundreds of millions of years. Thus fish is covered in distinct dark markings and is commercially harvested in Australia.

Fossilized Eye Indicates Fish Had Color Vision 300 Million Years Ago

An eye from a primitive fish that lived at least 300 million years, a time when the Earth consisted of a single continent surrounded by sea, has yielded evidence of color vision, AFP reported: Analysing the fossilized remains of a fish from the "spiny shark" family that lived long before the dinosaurs, scientists discovered light-sensing "rod" and "cone" eye cells — the oldest ever found. "This is the first discovery of vertebrate retinal fossils," said Gengo Tanaka from Japan's Kumamoto University, who co-authored the study in the journal Nature Communications. [Source: AFP, December 23, 2014]

leatherback turtles lived 150 million years ago
“It is rare for palaeontologists to find eye remains, as the soft tissue generally decays within 64 days, the authors of the study said. However, the Hamilton Quarry in Kansas is a treasure trove of unusually well-preserved fossils — an entire ecosystem having been rapidly buried under sediment. They included the extinct fish Acanthodes bridgei — among the oldest known vertebrates with jaws. It had a long, streamlined body and fins with spines, is believed to have lived in shallow, brackish water, and died out at the end of the Permian period about 250 million years ago when nearly 90 percent of species disappeared in the largest extinction in Earth's history.

“An A. bridgei specimen found at the quarry retained elements of the original eye colour and shape, and a light-absorbing pigment in the retina. The remains had been preserved under a thin coating of phosphate, Tanaka told AFP. Analysis of the tissue "provides the first record of mineralized rods and cones in a fossil," said the study. These, combined with light-absorbing melanin pigments, suggested the fish was "probably" able to see in low light using highly-sensitive rod cells, and by day using cone cells. In modern animals, cone cells respond individually to light at specific wavelengths, thus allowing observation of different colors. "The presence of cones indicates that A. bridgei likely possessed color vision", the study said — though conclusive evidence is needed.Vision is thought to have existed for at least 520 million years, but this is the first direct evidence of color-sensitive receptors.

Fossil Captures 380-Million-Year-Old Fish Birth

In 2008, scientists in Australia announced they had discovered the oldest mother of any species ever found — a 380-million-year-old fish fossilized while still attached to her offspring by an umbilical cord. AFP reported: Dubbed "mother fish" by the scientists who discovered her in northwestern Australia, "Materpiscis attenboroughi" is not only an entirely new genus and species, but pushes back the first known case of live birth in the animal kingdom by some 200 million years. The tail-first birthing process was probably similar to that of some species of sharks and rays living today, says the study, published in the British journal Nature. "The discovery is certainly one of the most extraordinary fossil finds ever made, and changes our understanding of the evolution of vertebrates," commented lead researcher John Long, head of science at Museum Victoria. [Source: AFP, May 28, 2008]

“Long and his colleagues were particularly astounded to find such a sophisticated reproductive system so far back on the evolutionary clock. "It shows us that live birth was occurring at the same time as egg laying, and that these mechanisms evolved together rather than sequentially," explained co-author Kate Trinajstic, who together with Long found the fossil. The existence of the embryo and umbilical cord within the specimen also provides the first-ever example of "internal fertilisation" — that is, sex with penetration, the study says.About 25 centimeters (10 inches) long, "mother fish" belongs to an extinct group of vertebrates, known as placoderms, that thrived during Middle Palaeozoic Era some 420 to 350 million years ago. Often called the dinosaurs of the seas, they ruled the world's lakes and oceans for almost 70 million years.

“The new find, remarkably preserved in three dimensions, contains a single, intra-uterine embryo connected by a calcified umbilical cord. Partly hidden under a fossilised fin, the cord and embryo would have gone entirely unnoticed but for a last-minute hunch, said Trinajstic, a professor at the University of Western Australia in Crawley. "John and I were just going to write up the fish, describe it anatomically," she recalled in a phone interview. "But we decided to give it one last acid bath to see if we could expose more of the shoulder from the rock." It was a risky move, she said. Too much acid, and "the whole thing crumbles." The went for lunch and came back an hour later. "When we pulled it out of the acid, the embryo was just sitting there — is was so perfectly preserved, so clear, it could not have been anything else."

Because they had already dated the fossil, the two researchers, who have been working together since the mid-1980s, knew immediately that they had a major find on their hands. "I remember thinking, 'Oh wow, we've really scored big this time'," Trinajstic said. They further examined the fossil with high-resolution scanning electron microscopy and computer tomography scanning, which also showed the path of a major blood vessel inside the umbilical cord. The fish and its unborn offspring probably fell victim to rapid depletion of oxygen in the water, settling to the bottom of the sea where they were gently covered in layers of silt-like mud that hardened over time, according to the scientists. Long and his colleagues named their find after pioneering naturalist Sir David Attenborough, who first discovered the Gogo site which during the Devonian Period was a 1400-kilometer coral reef off the Kimberley coast of northwest of Australia.

The Late Devonian was 383 million to 372 million years ago

350-Million-Year-Old Fish Likely Preyed on Humans' Ancestors

Around 350 million years ago, long before the dinosaur age, a gigantic fish with huge fangs hunted in rivers in the southern supercontinent Gondwana in what is now South Africa. The 2.7 meters-(9 foott) -long is the largest bony fish on record from the Late Devonian (383 million to 359 million years ago) and was predatory, prompting researchers to call it Hyneria udlezinye, or the "one who consumes others," in IsiXhosa, a widely spoken Indigenous language in the region of South Africa where the bones were found. "Picture a huge predatory fish, easily topping 2 meters [6.5 feet] in length and looking somewhat like a modern alligator gar but with a shorter face like the front end of a torpedo," study co-author Per Ahlberg, a professor in the Department of Organismal Biology at Uppsala University in Sweden, told Live Science. "The mouth contained rows of small teeth, but also pairs of large fangs which could probably reach 5 centimeters [2 inches] in the largest individuals." [Source: Sascha Pare, Live Science, February 22, 2023]

According to Live Science: Researchers discovered the first clues of the ancient fish's existence in 1995, when they unearthed a series of isolated fossilized scales at an excavation site called Waterloo Farm near Makhanda (formerly known as Grahamstown), in South Africa. In study published in February 2023 in the journal PLOS One, the researchers have finally pieced together a skeleton of the newfound species of giant tristichopterid, a type of ancient bony fish. "It's been a long journey ever since then, assembling the answer to where these scales came from," study co-author Robert Gess, a paleontologist and research associate at the Albany Museum and at Rhodes University in South Africa, told Live Science.

“The skeleton reveals that H. udlezinye was a voracious predator. "The fins are mainly towards the back of the body. This is an ecological characteristic of a lie-in-wait predator; it can put on a sudden spurt. Hyneria would have lurked in the dark shadows and waited for passing things," Gess said. "It's the one that consumed others." The giant fish probably preyed on four-legged creatures known as tetrapods, the ancestral group that led to the human lineage. "The tristichopterids evolved into monsters that, in all likelihood, ate [our ancestors]," Ahlberg said.

“Previous research identified another species of the same genus, H. lindae, at an excavation site in Pennsylvania, which was part of the supercontinent Euramerica during the Late Devonian. The fossils from Waterloo Farm are the first to indicate that Hyneria lived in Gondwana. The new study also reveals that giant tristichopterids lived not just in the tropical regions of Gondwana, but across the continent and even in the polar circle.

“Most tristichopterid fossils found to date have been excavated in Australia, skewing our perception of the distribution of these animals. Other regions which belonged to Gondwana, like Africa and South America, are less well researched. "Because Australia was in the tropics, and because all the well-sampled sites from this period and from Gondwana happen to be in Australia, there was a feeling that these giant tristichopterids originated in what is now Australia — along the tropical coast of Gondwana," Gess said. Now, for the first time, researchers have found the remains of a giant tristichopterid in what would have been a polar region at the time. "We have this guild of ginormous predatory fish and this is the only example we have from the polar regions," Ahlberg said.


Nicholas R. Longrich of the University of Bath wrote in The Conversation: Sixty six million years ago, sea monsters really existed. They were mosasaurs, huge marine lizards that lived at the same time as the last dinosaurs. Growing up to 12 meters long, mosasaurs looked like a Komodo dragon with flippers and a shark-like tail. They were also wildly diverse, evolving dozens of species that filled different niches. Some ate fish and squid, some ate shellfish or ammonites. [Source: Nicholas R. Longrich, Senior Lecturer in Paleontology and Evolutionary Biology, University of Bath, The Conversation, December 30, 2022]

Fossils of Mosasaurs have been found in every continent. They “made up a fraction of all the thousands of species living in the oceans, but the fact that predators were so diverse implies that lower levels of the food chain were diverse too, for the oceans to be able to feed them all. Mosasaurs and other animals — plesiosaurs, giant sea turtles, ammonites, countless species of fish, molluscs, sea urchins, crustaceans — flourished, then died out suddenly when the 10-kilometer wide Chicxulub asteroid slammed into “the Yucatán Peninsula 66 million years ago”, launching dust and soot into the air, and blocking out the sun. Mosasaur extinction wasn’t the predictable result of gradual environmental changes. It was the unpredictable result of a sudden catastrophe. Like a lightning strike from a clear blue sky, their end was swift, final, unpredictable.

“But mosasaur evolution may also have started with a catastrophe. Curiously, the evolution of the giant carnivorous mosasaurs resembles that of another family of predators — the Tyrannosauridae. The giant T. rex evolved on land at about the same time that mosasaurs became top predators in the seas. Is that a coincidence? Maybe not. Both mosasaurs and tyrannosaurs start to diversify and become larger at the same time, around 90 million years ago, in the Turonian stage of the Cretaceous. This followed major extinctions on land and in the sea around 94 million years ago, at the Cenomanian-Turonian boundary.

“These extinctions are associated with extreme global warming — a “supergreenhouse” climate — driven by volcanoes releasing C02 into the atmosphere. In the aftermath, giant predatory plesiosaurs disappeared from the seas and giant allosaurid predators were wiped out on land. With predator niches left vacant, mosasaurs and tyrannosaurs moved into the top predator niche. Although they were wiped out by a mass extinction, mosasaurs and T. rex only evolved in the first place because of a mass extinction.

Top predators are fascinating because they’re big, dangerous animals. But their size and position at the top of the food chain also make them vulnerable. You have fewer animals as you move up the food chain. It takes many small fish to feed a big fish, many big fish to feed a small mosasaur, and many small mosasaurs to feed one giant mosasaur. That means top predators are rare. And apex predators need lots of food, so they’re in trouble if the food supply is disrupted.


Tylosauraus Proriger —a Species of Mosasaur

Tylosauraus proriger was an enormous mosasaur that lived in North America 85 to 73 million years ago. It and was about 14 meters (45 feet) long. and had a huge appetite. Examinations of fossils that contained its stomach contents suggest they at least scavenged sharks and may have hunted them. Teeth from large sharks (Cretoxyrhina mantelli) imbedded in mosasaur vertebrae indicate that sharks have attacked mosasaurs or at least put up a good fight when attcked,

Related to modern day snakes and monitor lizards but not a dinosaur, Tylosaurus proriger lived during the Cretaceous in an ancient body of water called the Western Interior Seaway, which once cut through what is now North America. According to National Geographic: The reptile propelled itself through the water with its powerful, flat tail and steered with its four paddlelike flippers.

“Tylosaurus proriger was one of the deadliest hunters of its time. It had a long snout and hinged jaws, which gave it a fearsome bite. Its mouth was lined with rows of cone-shaped, razor-sharp teeth. And this colossal creature was always ready to chow down. As it glided along the sea, sometimes surfacing above the waves, Tylosaurus proriger snapped up fish, seabirds, and even other marine reptiles such as the over 10-foot-long plesiosaurus. Given that this big beast was about the length of a school bus, it's no wonder it had a monster-size appetite!

Thalassotitan Atrox — A Mosasaur That Ate Other Mosasaurs

The discovery of new species of mosasaur, Thalassotitan atrox, dug up in the Oulad Abdoun Basin of Khouribga Province, an hour outside Casablanca in Morocco, was announced in 2022. Nicholas R. Longrich wrote: At the end of the Cretaceous period, sea levels were high, flooding much of Africa. Ocean currents, driven by the trade winds, pulled nutrient-rich bottom waters to the surface, creating a thriving marine ecosystem. The seas were full of fish, attracting predators — the mosasaurs. They brought their own predators, the giant Thalassotitan. Nine meters long and with a massive, 1.3 meter-long head, it was the deadliest animal in the sea. [Source: Nicholas R. Longrich, Senior Lecturer in Paleontology and Evolutionary Biology, University of Bath, The Conversation, December 30, 2022]

Thalassotitan was just one of a dozen mosasaur species living in the waters off of Morocco. Most mosasaurs had long jaws and small teeth to catch fish. But Thalassotitan was built very differently. It had a short, wide snout and strong jaws, shaped like those of a killer whale. The back of the skull was wide to attach large jaw muscles, giving it a powerful bite. The anatomy tells us this mosasaur was adapted to attack and tear apart large animals. The massive, conical teeth resemble the teeth of orcas. And the tips of those teeth are chipped, broken and ground down. This heavy wear — not found in fish-eating mosasaurs — suggests Thalassotitan damaged its teeth biting into the bones of marine reptiles like plesiosaurs, sea turtles and other mosasaurs.

At the same site we’ve found what look like the fossilised remains of its victims. The rocks producing Thalassotitan skulls and skeletons are full of partially digested bones from mosasaurs and plesiosaurs. The teeth of these animals, including those of half-meter skull from a long-necked plesiosaur, have been partially eaten away by acid. That suggests they were killed, eaten and digested by a large predator, which then spat up the bones. We can’t prove Thalassotitan ate them, but it fits the profile of the killer, and nothing else does, making it the prime suspect.

Giant Sea Predator That Lived 244 Million Years Ago

In 2021, scientists said that one the largest animals that ever lived was a Triassic period predator that was somewhat similar to modern-day whales. Joshua Hawkins wrote in BGR: researchers believe that a 244-million-year-old fossil would have rivaled current cetaceans. The animal — an ichthyosaur — existed 8 million years after the first ichthyosaurs, at the most.“The new study, which was published in Science on December 24, focuses heavily on the discovery of the fossil in Fossil Hill, Nevada. It also focuses on how the creature that left the fossil behind could have grown as large as it did. Based on the discovery, scientists believe that the ichthyosaur that they found had a two-meter-long skull. They also believe that it was a completely new species of Cymbospondylus. [Source: Joshua Hawkins, BGR, January 3, 2022]

“Researchers say that this is the largest known tetrapod of the Triassic period, on land or in the sea. It’s also the first in a series of massive ocean giants that would go on to rule the sea. They also believe that the creature was able to grow to the size it did as quickly as it did by eating ammonoids. These small, yet abundant prey, would have helped the ichthyosaur grow exponentially faster. Because of the time period, scientists feel the end-Permian mass extinction helped provide such an abundant source of ammonoids.

“The discoveries they’ve found have also led scientists to believe that this Triassic period predator evolved much earlier than whales. Scientists currently consider whales to be the largest animals on Earth. “In the study’s abstract and conclusions, the researchers noted that the environment of the time may have supported multiple creatures the same size. Additionally, the abundance of ammonoids could have helped fuel the exponential growth of the ichthyosaur shortly after its origins.

Jurassic-Era Fish Found the U.K.

In 2022 a huge cache of 183-million-year-old fossils was found on a farm on the outskirts of Gloucestershire in the Cotswolds in England that included fish, giant marine reptiles called ichthyosaurs, squids, insects and other ancient animals dating to the early part of the Jurassic period (200 million to 145 million years ago). Jennifer Nalewicki of Live Science wrote: Of the more than 180 fossils logged during the dig, one of the standout specimens was a three-dimensionally preserved fish head that belonged to Pachycormus, an extinct genus of ray-finned fishes. The fossil, which researchers found embedded in a hardened limestone nodule poking out of the clay, was exceptionally well preserved and contained soft tissues, including scales and an eye. The 3D nature of the pose of the specimen's head and body was such that the researchers couldn't compare it to any other previous find. [Source: Jennifer Nalewicki, Live Science, July 29, 2022]

"The closest analogue we could think of was Big Mouth Billy Bass," said Neville Hollingworth, a field geologist with the University of Birmingham who discovered the site with his wife, Sally, a fossil preparator and the dig’s coordinator. "The eyeball and socket were well preserved. Usually, with fossils, they're lying flat. But in this case, it was preserved in more than one dimension, and it looks like the fish is leaping out of the rock," Hollingworth told Live Science. "I've never seen anything like it before," Sally Hollingworth added. "You could see the scales, skin, spine — even its eyeball is still there."

The sight astounded the Hollingworths so much that they contacted ThinkSee3D, a company that creates digital 3D models of fossils, to create an interactive 3D imageof the fish to help bring it to life and to allow researchers to study it more closely. At one time, this region of the United Kingdom was completely submerged by a shallow, tropical sea, and the sediments there likely helped preserve the fossils; Neville Hollingworth described the Jurassic beds as slightly horizontal, with layers of soft clays under a shell of harder limestone beds.

"When the fish died, they sank to the bottom of the seabed," said fossil marine reptile specialist Dean Lomax, a visiting scientist at the University of Manchester in the U.K. and a member of the excavation group. "As with other fossils, the minerals from the surrounding seabed continually replaced the original structure of the bones and teeth. In this case, the site shows that there was very little to no scavenging, so they must've been rapidly buried by the sediment. As soon as they hit the seabed, they were covered over and protected immediately."

A number of diverse specimens dated to the Toarcian age (a stage of the Jurassic that occurred between 183 million and 174 million years ago) and included belemnites (extinct squid-like cephalopods), ammonites (extinct shelled cephalopods), bivalves and snails, in addition to fish and other marine animals.

Dinosaur-Era Sturgeon

Full-body specimens of Acipenser praeparatorum, a newly-described, 66-million-year-old sturgeon species, were discovered in the Hell Creek Formation in North Dakota in the early 2020s. Joanna Thompson of Live Science wrote: The team found the fossils at a site called "Tanis," a section of the famous Hell Creek Formation, which spans parts of Montana, South Dakota, North Dakota and Wyoming, and it was once home to a large, deep river that fed the now-dry Western Interior Seaway that stretched from the Gulf of Mexico to the Arctic Ocean. But one fateful day 66 million years ago, Tanis became a mass grave for thousands of ancient freshwater fish, which were smothered and buried in place in the blink of an eye, possibly in the minutes after the asteroid impact that wiped out the nonavian dinosaurs. "It was really amazing," Lance Grande, a paleontologist at the Field Museum in Chicago and co-author of the study, told Live Science. "I mean, [the fish] were stacked up like cordwood." [Source: Joanna Thompson, Live Science, October 12, 2022]

“Grande and his colleagues quickly realized that four (two of each species) of the specimens were something special. Almost all of the creatures' bony outer coverings, or scutes, were intact and impeccably preserved. And the specimens help fill a gap in North America's fossil record, which lacks many late Cretaceous species. "They have a lot of clear sturgeon similarities, which makes them easy to identify," Grande said. "But they have various unique features that allow us to describe them as something new."

“The researchers dubbed one of the newfound species Acipenser praeparatorum ("acipenser" means "sturgeon" in Latin, and "praeparatorum" translates as "to make ready," in honor of the team that prepared the fossil prior to its investigation); they named the other species Acipenser amnisinferos, or the "sturgeon from Hell's Creek.") Both fish species are extinct today. However, they bear an unexpected resemblance to modern-day sturgeon that are native to East Asia and Europe, rather than North America, study co-author Eric Hilton, an evolutionary biologist at the Virginia Institute of Marine Science, told Live Science.

Sturgeons and their relatives are particularly distinctive in the fossil record. "They have these big, bony plates on the outside," Hilton explained, which protect the fishes' corpses from being torn apart by waves or strong river currents that tend to pulverize the remains of more delicate fishes. And since exposure to lots of oxygen tends to break down body tissues before they can fossilize, sturgeons' preference for low-oxygen environments sets them up for preservation.

For the sturgeons at the Tanis site, however, it wouldn't have mattered how much oxygen was in the water on the day they died; they were the victims of a massive tidal wave that swept thousands of pounds of sediment into the river, burying them almost instantly. Scientists suspect that this wave was triggered by the same dinosaur-killing Chicxulub asteroid that smacked into the Yucatán Peninsula — Tanis is littered with tiny, telltale beads of glass, called tektites, that are chemically identical to those found at the Chicxulub crater. Like the rest of the Hell Creek Formation, Tanis today is a snapshot of the end of the Mesozoic era. In addition to the two newly described sturgeon species, the river was chock-full of paddlefish, bowfish, ammonites, various insects and mosasaurs.

Image Sources: Wikimedia Commons; YouTube, Animal Diversity Web, NOAA

Text Sources: Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; Wikipedia, National Geographic, Live Science, BBC, Smithsonian, New York Times, Washington Post, Los Angeles Times, The New Yorker, Reuters, Associated Press, Lonely Planet Guides and various books and other publications.

Last Updated March 2023

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