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Week 10 Power Poll: Semi-Aquatic Tetrapods

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Time to learn

For the past 5 years I have been writing for Off Tackle Empire, I have done a science-themed Power Poll each season, specifically a Power Poll involving the sciences I study— Paleobiology, Biology, and Geology. My past Power Polls were Dinosaurs, Marine Tetrapods, Not Dinosaurs, and Geologic Time Periods. I’m excited to bring you all my 5th scientific Power Poll, Semi-Aquatic Tetrapods! Call it a sequel (or maybe a prequel) to my Marine Tetrapods Power Poll. These types of animals are very near and dear to my research heart.

To orient you with the terms, tetrapods are animals that are descended from the first four-legged vertebrates that made their way onto the land from the sea— those “walking-fish.” Today, tetrapods encompass amphibians, reptiles, birds, and mammals. Even a snake, though it lost its legs, is a tetrapod because snakes (which are lizards) ancestrally have four legs. Semi-aquatic, a fairly self explanatory term, indicates an organism’s lifestyle having ecological affinities for both a terrestrial and an aquatic environment. I think semi-aquatic animals are the coolest animals because they in particular represent evolutionary intermediates between two very different environments. It’s why I study them! They’re great for answering macroevolutionary questions pertaining to major evolutionary transitions. So without further ado, the Week 10 Power Poll.

**Only Nebraska and Purdue changed slots from last week to this week, with Nebraska moving -1 to 11, and Purdue +1 to 10.

1. Ohio State— Elephant Seal

Elephant seals are the biggest seals on the planet. A male elephant seal can reach up to TWENTY feet long and 8800 lbs. A seal. It’s the largest Carnivoran (mammals that include dogs, cats, bears, seals and sea lions, raccoons, otters, weasels, etc.) and they are so named, not for their size, but because of the males’ trunk-like structure on their noses. Don’t be mad, Ohio State fans, this is an impressive semi-aquatic tetrapod. It’s huge, loud, aggressive, has one natural predator (the orca—that it rarely interacts with) and dare I say in some ways is quite lovable.

First Place Votes: 15 out of 15

2. Penn State— Giant River Otter

These are not the cute and cuddly river otters that we’ve all fallen in love with on social media. These are terrifying looking, 6 foot long, vicious, Jaguar harassing, Caiman eating, Anaconda eviscerating Giant River Otters. I am convinced that these are the true rulers of the Amazon. Their semi-aquatic adaptations include exceptionally dense fur, a flattened tail, and webbed feet. They have few consistent natural predators (and are pretty immune to everything when they’re in a large group) and they are highly social, but territorial animals, and incredibly loud and chatty. Oh god it’s literally Penn State in animal form.

3. Minnesota— Spinosaurus

Spinosaurus, a famous, but misunderstood dinosaur, was the largest theropod (two-legged, meat eating) ever, maxing out at 50 feet long. That means only 6 spinosaurs’ placed snout tip to tail of each other would stretch across a football field. It’s an enormous animal, but interestingly enough was probably only a real threat to a fish and it turns out it had short stumpy legs. Not at all the imposing creature it was once thought to be. Also, this is an incredibly problematic and controversial animal because it may not have actually* been truly semi-aquatic... It’s perfect for Minnesota. Are the Golden Gophers actually good? Is Spinosaurus actually semi-aquatic? Who knows!

Shoutout to our Iowa writers for the 5th & 6th place Minnesota votes.

4. Wisconsin—Saltwater Crocodile

Stephen Michael Barnett

Saltwater crocodiles are incredible animals. They can swim massive open water marine distances which other crocodiles cannot. They also have the strongest bite force of any living animal on the planet, including the great white shark. This is a genuinely deadly to humans animal, that can go pretty much anywhere in the Southeast Asian marine tropics, but it is restricted to that range. These crocs have a secret weakness though. The muscles for their powerful jaws are really only strong in the bite direction. In theory a grown man can hold its jaws shut with his bare hands. I’m not saying Wisconsin is weak, but it certainly has a surprisingly bad weakness— that’s been exploited twice this season so far.

5. Michigan— Tanystropheus

Mark Witton

Yes, this animal is real. It’s a 20 foot long Middle Triassic reptile (235 Ma), more closely related to archosaurs (reptiles like dinosaurs, birds, pterosaurs, and crocs) than to reptiles like lizards and snakes. It has the longest neck to body ratio of animal ever. It was definitely semi-aquatic, with fossils found associated only with aquatic environments and it likely swam with large, webbed hind legs. Somehow animals in this family, Tanystropheidae, lived for like 20 million years, so it apparently did something right enough (to stay around), but it’s hard to understand why/how and that perfectly summarizes Michigan Football under Jim Harbaugh.

6. Iowa— Nothosaurus

Nothosaurus is a member of the group Sauropterygia which famously includes the Loch Ness Monster looking Plesiosaurs. Nothosaurs represent sort of an early ancestor to proper plesiosaurs and they definitely still spent time on land, probably similar to seal and sea lion ecology. Nothosaurus specifically was about 13 feet long with webbed feet, but not entirely enclosed paddles like its plesiosaur descendants. Nothosaurus was a really cool animal and clearly had the potential to become bigger and better, and it did, evolutionarily speaking. With four very varying games left, will Iowa do the same? I think so.

7. Indiana— Ambulocetus

For the Latin nerds, you may have recognized the word “Ambulo” which means “to walk,” and the word “cetus” which means whale. So Ambulocetus is quite literally a walking whale and is as cumbersome as it sounds, but it represents a really amazing transition animal (every animal is a transition animal though). It is one of the many early stages of whales, when terrestrial hooved animals related to hippos, pigs, cows, antelope, and deer first evolutonarily ventured into aquatic environments. Wouldn’t you say this is Indiana Football on its way to something great this season or next?

8. Michigan State— Sea Krait

The sea krait is not a true sea snake. Yes, it is a snake that lives in the sea. But sea kraits evolved to be semi-aquatic independently of true sea snakes. Unlike true sea snakes which are fully marine, even giving birth to live young in the water, sea kraits are far more semi-aquatic, requiring land to lay their eggs and digest food. They do have semi-aquatic adaptations including a sideways flattened, oar-like tail. But honestly all snakes are “semi-aquatic,” as all snakes, even the landiest land snake are effortless in the water. Sea Kraits are a solid analog for Michigan State Football, a program that has, in the past, found its own success in the Big Ten (aquatic environment), but in the case of this year, shows that it is just not quite what it’s more aquatically suited relatives (better conference teams) are.

9. Illinois— Platypus

This is a great animal. I mean look at it. The bill of a duck, the tail of a beaver, big flappy feet, and to top it all off, it’s venomous and one of the few mammals that lays eggs (monotremes). You can’t help but root for this weird, almost pathetic-looking thing when you see it. As far as its swimming mechanics goes, the platypus, interestingly enough, doesn’t use that flattened tail to swim, but they actually row through the water with their forelimbs. Being an unexpected and shocking animal in every way defines the platypus, and I think Illinois in 2019 captures that spirit.

10. Purdue— Penguin

Penguins are technically the most aquatically adapted dinosaurs. Birds are dinosaurs and penguins traded flight for swimming about 34.2-47.6 million years ago. They’re very good swimmers, essentially able to “fly” underwater and are really quite pathetic on land. Penguins, unfortunately, have numerous natural predators in their various Southern Hemisphere locations like seals, orcas, sharks, even sea birds. They get beat up on a lot. I couldn’t help but think of Purdue this season when I think about Penguins. Respectable and loved enough, but just really getting smacked around by varying teams this season.

11. Nebraska— Hippopotamus

The hippo is a really cool semi-aquatic animal with genuine semi-aquatic adaptations including webbed hooves, and having its eyes, nostrils and ears at the top of its head which allows these senses to not be underwater when most of the animal is submerged. The reason why I likened the Hippo to Nebraska is because 1) The Hippo is the closest terrestrial relative to a whale, a magnificent animal, thus representing Nebraska’s closeness, but also detachment to greatness, and 2) because hippos are definitely a, “when you try to be, you are incredibly dangerous,” animal. I swear Nebraska has far more potential than they are showing. Right now they’re being the lazy hippo, but they needs to be the below hippo.

12. Maryland— Sea Lion

Smithsonian’s National Zoo

Not gonna lie, I mostly put in this entry to teach the difference between eared seals or Otariids (sea lions and fur seals) and true seals or Phocids (leopard seals, harp seals, elephant seals), but I did my best to fit it to Maryland. So eared seals, have small ear flaps, but also a more terrestrial stance with forward facing hindlimbs, and an aquatic locomotion completely different from their true seal relatives involving forelimb flapping (pectoral oscillation) and they are incredibly adept and maneuverable in the water. They are far more adept on land compared to true seals and can even “run” on land, which is why they are great for animal shows. However, less goofy on land doesn’t mean not goofy. Also, as someone who paddleboards in a Marina full of sea lions, they smell f*****g awful. Total sensory overload. Just like the Maryland flag is to your eyes. Sea lions are Maryland Football in multiple ways.

13. Northwestern— Thalassocnus

This is a giant sloth that lived in the water. Very few people know that even modern sloths are very good swimmers, moving faster in the water than they can on land, and fewer know that a whole group of giant ground sloths evolved to be semi-aquatic grazers. Thalassocnus, a genus encompassing a few species, lived 3-7 million years ago in South America. It’s major semi-aquatic adaptation is extra dense bones, which assisted in keeping it submerged. It’s Northwestern because perhaps Northwestern used some dense aspects of the team this season and kept itself submerged during non-ideal times... like this whole season.

Last place votes: 5 out of 15

14. Rutgers— Marine Iguana

These lizards are one of the more well-known semi-aquatic tetrapods. Some of their limited marine adaptations include the ability to expel salt from specialized salt glands and the ability to hold their breath for 30 minutes, but overall, marine iguanas are probably the least morphologically suited to an aquatic environment of any animal on this list. They evolutionarily diverged from mainland iguanas 8-10 million years ago, probably blown out to the Galapagos Archipeligo on floating debris. Interestingly the extant Galapagos didn’t exist yet, so they probably landed on volcanic islands that are no longer around. Marine iguanas were kind of forcibly thrust into their modern ecology, but you know, they may not “belong,” but they’re not leaving the Galapagos for South America anytime soon, so. Guess they’ll just have to get better at being marine.

Last place votes: 10 out of 15


Well there you have it! Semi-aquatic tetrapods and the Big Ten Conference.