The main difference between soft and hard corals is that hard corals produce and leave behind a rock-like skeleton as they grow, made of calcium carbonate - CaCO3 (the same substance that chalk and Tums is made out of).
It is these calcified skeletons that together make up the primary structure of a coral reef, which can eventually grow to the size of a mountain range. A good example is the Great Barrier Reef, which despite recent mass bleaching is still presently the largest living thing on Earth and is visible from space - photo taken at Foammulah Atoll, Indian Ocean
Mounted reconstruction on display at the Rocky Mountain Dinosaur Resource Center, Woodland Park, Colorado
Reconstruction by Charles Bonner
When: Cretaceous (~ 89 - 83 million years ago)
Where: North America
What:Saurodon is one of the large fish which swam though the Cretaceous Seaway, the marine waters that covered much of North America during the late Mesozoic. This particular species was ‘only’ about 8.5 feet (~2.6 meters) long, with a relatively skinny body and large pointed lower jaw. These features are what gives the family Saurodontidae the nick-name 'sword eels’. The Saurodontidae fall into the later group Ichthyodectidae, a completely extinct clade that contains some of the largest fish on record. Today the living relatives of these gigantic fishes are in the clade Osteoglossomorpha and are some of the largest bony fish that swim though today’s waters.
This was not a very specious group - there are only three described species - but they have been known to science for almost two-hundred years. The first Saurodontidaewas named in 1824 by Richard Harlan (the discover of Harlan’s ground sloth) - but was misidentified as the jaw of an extinct marine reptile. This was corrected only six years later when the first Saurodon specimen was found, and it was clear that the fragmentary specimen which was previously named belonged to a large fish, not a marine reptile. The use of the long lower jaw in Saurodon and its kin is not well understood, but it has been hypothesized that perhaps these predatory fish dug prey out from the deep muds at the bottom of the seaway.
Mounted specimen on display at Harvard Museum of Natural History
Reconstruction by Jaime Chirinos
When: Cretaceous (~ 125 - 99 million years ago)
Where: Australia
What:Kronosaurus is an australian plesiosaur. Yes, it is a plesiosaur even though it lacks the long neck that many people associated with the group. Plesiosauria is roughly divided into two groups; Plesiosauroidea - the long necked forms and Pliosauroidea - the short necked forms. Kronosaurus is an example of the latter clade, and shows many of the defining features of this group - such as an enormous head with massive jaws, a short neck, and a relatively short tail- the opposite in many ways of their cousins the plesiosauroids. This australian sea monster was one of the largest of its clade, with estimates of up to 33 feet long (~10 meters). Its teeth reach almost 5 inches (~12 cm ) long in crown length - the part above the gumline. The total tooth would have been over double in size. The large size of its teeth, combined with distinct shape and the lack of clear cutting surfaces also for their easy identification if they are found as isolated material.
The Kronosaurusspecimen seen above was found in on private property in central Queensland, Australia in the 1920s. A crew from Harvard was shown where the specimen was weathering out, and set about excavating the fossil. After years of work, the specimen was boxed up into over 80 crates, weighing in at over 6 tons and shipped to the states, where it was mounted at the Harvard museum. Decades later the original discoverer of the material finally got the see the results of the preparation and mounting of what he termed ‘his dinosaur’ at the age of 93. In life Kronosaurus was a top predator; there are fossils of Elasmosauridae plesiosaurs that show bite wounds that could have come from Kronosaurus! No fish for this animal, it was after much bigger prey, leading to amazing plesiosaur vs plesiosaur encounters. Or so I like to imagine!
Fossil specimen from the Museum für Naturkunde in Berlin, Germany
Model by Dan Erickson and on display at the American Museum of Natural History
When: Permian to Cretaceous (260 to 80 million years ago)
Where: World Wide
What:Hybodus is a very wide spread, both temporally and geographically, fossil shark. I will be upfront here and say that I may be grossly over representing its temporal range, the literature is rather confusing and there have been a number of species going in and out of Hybodus over the years. So you may want to consider this an article on hybodontiform sharks in general, rather than just the one genus. Shark fossils are fairly rare in the fossil record when compared to other fish because sharks do not ossified their skeleton. However, Hybodus and its kin can be identified from fragmentary remains by their distintive teeth (two kinds in their jaws, both flat and pointy) and their ossified dorsal spines. These spines can be easily seen on both the fossil and the model above, they were most likely involved with stabilization of Hybodus as it swam. The relatively few full body specimens preserved complete the picture, showing us that Hybodus was a streamlined shark with a very heavy ribcage compared to most sharks, and that the males had not only ventral claspers, as seen in modern sharks, but also a series of spines on the side of the head - which are depicted above.
Hybodontiform sharks were the dominate group of sharks in the Jurassic period, and were even very common in the late Cretaceous after modern sharks had originated and diversified. Studies of this archaic shark clade have shown they were most likely over all slow swimmers, but they could enjoy brief bursts of speed if needed. The diverse teeth forms of hybodont sharks imply they did not just eat fish, but also were able to prey on hard shelled invertebrates. In the shark family tree Hybodontiformes is the first group outside of Neoselachii - the clade that contains all living sharks and rays.
Here’s the penultimate Jurassic June entry, Jurassic World’s Mosasaurus.
I wasn’t able to find a lot of complete baby mosasaur remains online to base this one off of, so I made the silhouette a bit closer to a real Mosasaurus, along with incorporating some juvenile crocodile and komodo dragon. Including having a stand-out color scheme. Baby komodo dragons/monitor lizards (a close relative to ol Mosa) are seriously pretty. Enjoy!
This beautiful great hammerhead was one of the stars of my recent trip to Bimini! Despite their enormous size and power, they are incredibly cautious and can even be regarded as shy. Unlike the tiger sharks at Tiger Beach, these sharks are easily spooked by people not being calm, or even the ever-present, far smaller nurse sharks!
Don’t know if i like this or not ^^; but best Aquarium tunnel I’ve managed to draw so far. This is a part of the Aquatics facility at NightSchool, the hallways are a part of the aquarium that you walk through to get to classes ✨ Marine students can also enter the aquarium and swim through it ^.^
![[source]](https://64.media.tumblr.com/4190d83bf4effa85daf4f668e2b9e0ee/tumblr_n4ygadGHBk1siz05no1_640.jpg "[source]")
