The Sauropod family is mainly comprised of quadrupedal (walking on four feet), slow moving, long-necked dinosaurs. Sauropods are known for their calm and generally pacifistic demeanor, and were generally herbivorous. Sauropods species came in a wide range of sizes from the diminutive Ohmdenosaurus, which only grew about 13 feet long to the biggest of the Titanosaurs like the Patagotitan mayorum which grew up to a whopping 121 feet long (that’s longer than a blue whale).
Sauropods were big eaters, requiring literal tons of fresh vegetation per day to survive. Their long necks allowed them to reach leaves from tall trees and low growing shrubbery before swallowing their food without stopping to chew it. Their long necks also helped them keep an eye out for predators. Fossil evidence also suggests that sauropods moved in herds and utilized a somewhat complex social structure arranged by age. A site of Mussaurus patagonicus fossils showed evidence of communal egg-laying grounds as well as proof that juveniles congregated into ‘schools’ while adults grazed near the herd alone or in pairs.
Brittle Stars are echinoderms (related to sea stars, urchins, crinoids, etc.) which use their long, serpent-like arms to crawl across the ocean floor or swim through the water. They can look very similar to sea stars but can be differentiated by their distinct central body disk and thin flexible arms, which are often covered in spines. If attacked, Brittle Stars can defensively drop their arms to make their escape and live to regenerate them another day.
Stromatolites form when carpets of microbial life (usually cyanobacteria) are covered with a layer of sediment. That layer is then repeatedly covered by more cyanobacteria, which is covered by more sediment, and so on and so forth. When this structure fossilizes, we can see the layers formed in stone. Stromatolites can have different colors due to the type of minerals that made up the sediment. Sometimes Stromatolites are cut into slices so that those layers are visible, as pictured here.
Stromatolites have been forming for as long as cyanobacteria have existed, which is a really long time (about 3.5 billion years ago), and continue to do so in certain marine environments today.
Bryozoans are a type of filter-feeding colonial marine animal that has been living in the oceans since near the beginning of life on the planet. An individual Bryozoa is plant-like in appearance, but the colonies often form round, blobby masses that tether to various surfaces.
Bryozoan fossils can also look like tree branches and can be found all over the world, including here in Tennessee!
Nautiloids are an entire group of armored or shelled cephalopods that were prevalent during the Mesozoic Era, but still have some living members today. Many nautiloid species had long, conical shells that protected them from predators. Others resembled their cousins Ammonites with a curled, spiral shell. The only living members of the Nautiloid family are the nine living species of Nautiluses, which sport a spiral shell and live deep in the Pacific Ocean.
Crinoids are marine echinoderms (the group that contains urchins and starfish) that have been a part of Earth’s history for about 500 million years. They first developed during the Cambrian period, and some species still live in the oceans today. Despite appearing plant-like at times, crinoids are animals. Older crinoid species typically had a stem which anchored them to the ocean floor, a calyx or cup on top of that stem which contained its organs, and arms branching out from the calyx to help it filter feed. Crinoids have diversified a lot in the last half eon; some still anchor down in coral reefs, while some have evolved to swim around using their feathery arms for propulsion.
Fossils of crinoids can be found all over the world, even in Tennessee. Sometimes, you’ll hear these fossils called ‘Indian money’, and while Native Americans did not use crinoid fossils for currency, they were sometimes used as beads for jewelry. To find crinoid fossils, keep an eye out for something that looks like a stack of coins or a disk with the middle cut out –– that’s a fossil crinoid stem!
Pterodactylus kochi was a small pterosaur that lived in southern Germany during the Jurassic period. Often depicted as giant avian terror, pterodactyls in reality were a smaller variety of pterosaur, with a wingspan of 1 to 4 feet. The Pterodactylus kochi was particularly small with a 18 inch wingspan.
Pterodactylus kochi lived and hunted amongst the lagoons and archipelagos of ancient Germany. They ate small schooling fish, insects, crustaceans, and any other small animal they could catch. Much of what we know about this species is thanks to the incredibly well- preserved specimen from the Solnhofen Limestone.
The idea that birds are dinosaurs is still relatively fresh in the general zeitgeist, but paleontologists have been investigating this connection since the discovery of the first fossils of Archaeopteryx lithographica were unearthed in 1861. Since then, more fossils have been found which further support the link between birds and theropod dinosaurs of old.
Like some modern birds, they ate small mammals, lizards, amphibians, and insects. Unlike modern birds, the Archaeopteryx had teeth instead of a hard beak. It also had claws at the bend of its wings that scientists think they used to grab onto trees as they glided through the canopy. As for flight, there is still a debate over whether they could truly take flight as easily as modern birds. It is possible that they relied on gliding from tree to tree like a sugar glider or required a running start with little hops to take off flying.
Compsognathus was a genus of small theropod dinosaur that lived in Europe during the Jurassic period. Compsognathus, sometimes nicknamed ‘Compie’, is among the smallest dinosaurs, not accounting for modern birds, growing anywhere between 2 and 3 feet in length and weighing up to 8 lbs. The Solnhofen specimen was even smaller, about 30 inches long from nose to tail and weighing between 1 and 3 lbs, but this specimen was later determined to be a juvenile. It is thought that the Compsognathus would use its speed, agility, and sharp teeth to ambush small prey like lizards, insects, and possibly even small pterosaurs. Unlike their depiction in popular media, it is unlikely that they hunted in socially active groups.
In the waters of old Baravia, Germany, the Tharsis dubius, a small carnivorous ray-finned fish made their home. These tiny fish fed by sucking plankton and other tiny prey items into their mouths. Fossils of the Tharsis have shown that they often choked on their prey and died of suffocation.
The Mecochirus longimanatus is an extinct species of lobster-like crustacean whose fossils can be found in the Solnhofen Limestone of Bavaria, Germany. It is named for its extra long appendages that were likely used for feeding.
Horseshoe crabs have been around for about 450 million years, surviving all five major extinction events. You may notice that this particular species found in the Solnhofen Limestone, Mesolimulus walchi, looks a lot like modern horseshoe crabs. Their body plan has been so successful that they have not had to change very much at all to survive into the modern era. While Mesolimulus walchi may be extinct, its modern relative still thrive in the oceans today.
The Solnhofen Limestone has not only preserved the bodies of the crabs, but also their footprints!
Aeger tipularius was a species of shrimp that lived in the waters of the archipelago of modern Bavaria Germany. These shrimps are very well preserved by the fine grain of the Solnhofen Limestone.
Unlike stalked crinoids, the Saccocoma pectinata was a free-floating species that fed on plankton. It is believed that the Saccocoma pectinata could swim using its feathered arms to propel itself through the water. These crinoids have been excellently preserved in the Solnhofen Limestone with some specimens even retaining their feathery arm structures.
The Solnhofen Limestone is responsible for some of the best-preserved insect fossils from the Mesozoic. The fine grained sediment allowed for immaculate preservation of wing structures, body segments, and even coloration patterns. The preservation of insect species tells us about the type of environment of ancient Germany. For example, the presence of dragonflies and water striders tells us that the area was had laden with lagoons and bodies of freshwater.
(Late Jurassic)
The Brachiosaurus was a large sauropod dinosaur from the late Jurassic famous for its long, upright neck. Brachiosaurus were herbivorous and likely moved in herds which helped keep them safe from predators. They used their high vantage point to keep an eye out for danger and to access vegetation that grew higher up in the trees. They ate hundreds of pounds of leaves, branches, and other plant matter a day to sustain their large size. It is theorized that a Brachiosaurus could live around 100 years due to its size and slow-moving lifestyle.
Pictured here is the centrum of a Brachiosaurus vertebra.
The Lufengosaurus was a relative to the larger sauropods like Brachiosaurs but was smaller with a shorter neck and tail. Despite their smaller size (about 30 feet from nose to tail), they were still able to reach vegetation from the trees by standing up on their hind legs for short periods of time.
Rhamphorhynchus was a small pterosaur that lived in Europe during the Jurassic, most often found in the Solnhofen Limestone of Germany. Rhamphorhynchus is one of the best understood pterosaurs due to the excellent preservation in some of the fossils found, even including the wing membranes, skin, and stomach contents. Rhamphorhynchus had sharp teeth which it used to catch fish and other sea creatures and was an agile flier with an approximately 3-foot wingspan.
The Ichthyosaurus was a marine reptile known for its dolphin-like appearance and large eyes that lived during the early Jurassic through the early Cretaceous period. They were part of the larger Ichthyosaur family but were rather small compared to its relatives (its larger relative, Ichthyotitan could reach lengths up to 80 feet). Unlike most reptiles, the ichthyosaurus did not lay eggs and instead gave birth to live young. Evidence for this can be seen in the fossil record, as the bones of young have been found inside the body cavity.
The Ichthyosaurus was one of the first fossilized marine reptiles to be uncovered, and hundreds of remains have been found in England, Germany, Greenland, and Alberta. The earliest complete fossil was found by Mary Anning in 1811, though remains had been discovered as early as 1699.
The Camarasaurus was a medium to large sauropod genus from North America. The name Camarasaurus references the animal’s unique chambered vertebrae which aided in its respiratory system. The Camarasaurus had a slightly shorter neck and tail relative to other sauropods and had a boxy head and powerful jaw. It is believed that Camarasaurus’ bite force was among the strongest of all the sauropods and was used to break twigs and eat tough conifers.
The Allosaurus was a large (28 to 30 feet) predatory theropod dinosaur that lived in North America, Europe, and possibly even Africa and Australia. These apex predators had sharp teeth with which could bite and tear at soft tissue rather than rely on a strong bite force like some other theropods like T. rex. They also had large claws on its ‘hands’ used to grapple and subdue prey items. Allosaurus possessed two horns or crests on their brow, likely used as visual display or species recognition as opposed to fighting.
Gymnocidaris was a spiny sea urchin that lived during the Jurassic period. They had distinctive club-shaped spines that were used to protect from predators and to help wedge themselves into tight spaces to hide. They fed on microalgae and small, slow moving invertebrates like sponges or bryozoans.
Amongst the fossil bones and teeth of dinosaurs, paleontologists occasionally find fossilized dinosaur egg material. As you might expect, dinosaur eggs are rarely found due to their delicate nature, and it is generally hard to determine what type of dinosaur may have once been inside. However, finding the eggs, or better yet, the nests tell us a lot about dinosaur behavior. Some fossils of Oviraptor dinosaurs have been found on top of their eggs, indicating that they cared for their eggs like modern birds. Other larger species buried their eggs rather than brood as their weight would have done more harm than good.
With modern technology, our understanding of dinosaur eggs has improved further. It is possible to perform a CT scan on dinosaur eggs, which makes it possible for scientists to learn more about dinosaur embryos and their development.
Gar fish are long-bodied freshwater fish who possess armored scales along their bodies. Gars belonging to Lepisosteidae first developed in the early Cretaceous, but ancestors to these Gar first show up in the fossil record during the Jurassic Period. Gars are often called ‘living fossils’ as they have gone virtually unchanged over the last 100 million years. There is plenty of fossil evidence for the Gar in the Hell Creek Formation; their armored scales fossilize very well and appear a bit like shards of obsidian among the dirt.
(Early Devonian – Present)
Lungfish are long, eel-shaped fish that can breathe air. While some species of lungfish possess both lungs and gills, they have an advantage over gill-exclusive fish types because they are able to survive in oxygen poor waters and withstand droughts, which may explain why they have managed to stay relatively unchanged over the last 400 million years. Lungfish are considered a “missing link” in the evolution of mammals, reptiles, amphibians, and birds as they are the closest relative to early tetrapods (or all vertebrate animals with four limbs).
Titanosaurs were a group of large, long-necked dinosaurs in the Sauropod family that contained the largest land animals the world has ever seen. Even the smallest Titanosaurs were huge, growing about 23 feet long and weighing about 11 tons (22,000 lbs.) Amongst the largest Titanosaurs, Patagotitan mayorum could grow to 137 feet and weighed 70-77 tons (about as heavy as 10 to 14 African Elephants). Suffice it to say, these things were big.
Titanosaurs were widespread and their fossils have been found on all continents (even antarctica!), but the largest species lived primarily in modern Patagonia (hence the name Patagotitan) and Argentina.
During the age of the dinosaurs, flying reptiles called Pterosaurs ruled skies. Some mistakenly lump pterosaurs like the famous Pterodactyl in with dinosaurs, but pterosaurs belonged to their own order Pterosauria. Pterosauria and Dinosauria belong to the same clade called Archosauria, whose only two groups still living are birds and crocodilians.
Pterosaurs came in a wide range of sizes. The smallest pterosaur species was Anurognathus ammoni, which was about the size of a songbird, and the largest was the colossal Quetzalcoatlus northropi, who was about as tall as a giraffe (but lot more vicous).
Ancient Shark (Permian – Cretaceous)
Hybodus was a genus of shark that had great success in the ancient oceans. It was about 6 feet long and had small crown of spikes on its head and two more larger spikes by its dorsal fins. These spikes would have protected the shark from bigger predators, which partly contributed to its success. Another trait Hybodus had was two types of teeth for two types of prey. The teeth at the front of its mouth were sharp, used to bite down on prey, while the teeth in the back of its mouth were flat and could crush and break down hard shells and bones—a little like your own molars.
Brachiopods (Cambrian – Present)
Brachiopods are aquatic soft-bodied invertebrates who typically live inside a symmetrical two-halved shell. Though similar to bivalves in design, Brachiopods are deceptively unique, belonging to their own phylum, Brachiopoda. Brachiopods are generally stationary and are typically anchored in one spot, relying on filter feeding.
Bivalves are aquatic soft-bodied invertebrates who typically live inside a vertically symmetrical two-halved shell. They are similar to brachiopods, who are symmetrical both laterally and vertically, but the two are not actually very closely related. Today, bivalves vastly outnumber brachiopods, but during earlier periods, the inverse was true.
Bivalves are more mobile than they look, often burying themselves in sediment with the help of a muscular organ called a ‘foot’, and some can even swim by clapping their shell open and closed. Their shells have historically been used as jewelry, tools, and even money in certain cultures.
Ammonites (Devonian – Cretaceous)
At some point, most everyone has seen the fossil of an ammonite, perhaps thinking it was some kind of fossil snail shell. However, Ammonites were not gastropods, but cephalopods. Essentially a type of shelled squid, Ammonites and their cousins nautiloids populated the ancient seas eating small, slow moving organisms like plankton or jellyfish. Ammonites went extinct during the K-Pg extinction event, the same that killed the non-avian dinosaurs, alongside many other shallow water marine creatures due to chain reactions of the asteroid strike. The Ammonite’s still-living relative, the Nautilus, survived this extinction event thanks to its much deeper ocean habitat which was less effected by the issues on the surface.
Fossilization:
Ammonites are much beloved fossils for collectors, often cut down the middle and displayed in pairs as the empty chambers of the shell can fill with beautiful minerals. Ammonites can be mineralized with pyrite, agate, calcite, and even opal. Opalized Ammonites are nicknamed ‘Ammolites’.
Gastropods (Late Cambrian – Present)
Gastropods are a class of soft-bodied invertebrates and are members of the phylum Mollusca, including things like snails and slugs. Gastropods have been around since almost the beginning of the fossil record, developing all the way back in the oceans of the Cambrian Period (485- 541 million years ago). Gastropod bodies are simple but highly adaptable, and have diversified far past marine living. Today there are species in the oceans, in rivers, on land, and even on hydrothermal vents.
Plesiosaurs were marine reptiles that lived during the age of the dinosaurs. Though not dinosaurs themselves, Plesiosaurs are well-known for their distinctive body shape which inspired the famous cryptid, the Loch Ness Monster. While many believers argue that a Plesiosaur could still be in Loch Ness in Scotland, they all unfortunately went extinct at the same time at the non-avian dinosaurs following the K-Pg Impact. Their diet was comprised of fish and cephalopods. Plesiosaurs came in different shapes and sizes; some where large and long-necked like the Zarafasaura oceanis who had short faces with long necks, while some like the Pliosaurus had short necks and large heads.
The first complete Plesiosaur fossil was found by famous female paleontologist Mary Anning in 1823.
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