Jack R. Stack's Blog

Imagine you are in a time traveling submersible, and that you have been transported back to the middle Devonian period of Michigan. As you begin your dive you note on your instruments that the water is warm and salty, similar to the modern tropics. The water is turbulent, but soon you move into a more stable zone. You see large masses of corals and animals that appear to be rocks, but you know they are in fact mounds of blue-green algae. As you descend, the stromatolites become scarce and the corals become more prevalent. Among the corals you see thousands of small clam-like shells attached to the seafloor by stalks, creatures you know as brachiopods. You also see other coral like creatures that resemble moss. You recognize them as bryozoans, animals superficially similar to corals. A flash of movement in front of your submersible attracts your attention. You focus on the creature which resembles the modern day nautilus, which you know is modern descendent of the creature in front of you. The nautiloid propels itself backwards and out of your line of sight with the jet propulsion system shared by all cephalopods. As you get deeper you reach a reef bustling with a plethora of life. Corals, brachiopods, and bryozoans make their home below forests of crinoids, whose long feathery arms filter food from the current. You can see many animals moving among the reef, including colorful gastropods attached to the crinoids feeding off of their waste. Trilobites move along the seafloor, searching for food in the mud. Small armored fish called arthrodires and other strange looking fish called ptyctodonts swim amongst the crinoids, snatching up small invertebrates from the sea floor. You watch one fish move among the corals, crushing brachiopods in its powerful jaws. You jump when you see it get snatched by a nightmarish eel-like creature at least 10 feet long that bursts from a hole in the corals using its front fins to propel itself forward. You watch it's tusk-like lower teeth impale the unlucky ptyctodont as it pulls it back into its lair. A large straight shelled orthocone snatches a trilobite from the seafloor with its powerful tentacles. You see a placoderm the size of a man snatch one of the smaller fish, biting it in half. The larger fish then regurgitates the bony plates of the smaller fish and keeps swimming, completely unaware of the large shadow moving quickly behind it. You note that the rest of the fish have swum away, even the large eel-like Onychodus has retreated deep into its lair. The large fish notices the presence stalking it and begins to flee, but it is too late. A blur of movement and a crunching noise signal the end of the fish as it disappears in a cloud of blood. You notice its armored head sink to the bottom, its eyes transfixed in fear. What you see is the most fearsome predator ever to call Michigan its home. You estimate it to be 20 feet long, the size of a large great white shark. Its head and trunk region are heavily armored and its mouth resembles a large bear trap. Its head is thick like a bulldogs and its long body tapers down to a powerful tail that makes it capable of bursts of incredible speed. Its "teeth" are actually a set of self sharpening bony plates that have enough power behind them to bite through the engine block of a car. Its thick armor is covered with large tubercles combined with its powerful jaws give that give it a fearsome appearance. The fish you see is Dinichthys, a smaller cousin of Dunkleosteus, the ruler of the Devonian seas. Its name aptly means "terrible fish". Here in the Michigan Basin it is the unchallenged king, the top predator. It feeds on smaller placoderms, ambushing them with its surprising speed and snapping them in half with its powerful jaws. Its jaws open and close so fast it actually creates a suction that pulls its prey into its mouth to be sliced in two. You know from experiments on the jaw of Dunkleosteus that this fish possesses one of the most powerful bites of any animal to ever exist, over 8,000 pounds per square inch. Its smaller cousin possesses the same jaw design, also making it the most powerful set of jaws ever possessed in Michigan. Then it occurs to you; if its bite is strong enough to cut through the engine block of a car, surely it could also shred the lining of your sub. Just then the fish turns its attention to your submersible, its eery eyes locking with yours, sending a chill down your spine. The breath leaves your body as you realize that you are not welcome in this strange and savage reef, where strength and ferocity alone determine who or what survives. Your sub is large enough to be perceived as a threat, and this fish is a creature without fear of man or his constructs. It will destroy anything that is large enough to challenge it for supremacy. It turns and with a flick of its powerful tail it approaches at an alarming speed. You hear a horrible sound like two metals plates rubbing together, created by its twin shearing tooth-plates rubbing together. You struggle to regain your breath as you reset the dial on your submersible and return to the present. When you return you have a new respect for one of history's most dangerous predators.