Critter of the Month: Ichthyosaurus

Meet Flipper.  He’s a happy-go-lucky guy who’s only ambition in life is to cruise the water for a bite of squid.  He loves to greet new friends with a friendly splash.


It’s a dolphin!  It’s a shark!  It’s a…dinosaur?

Flipper isn’t any of those things! So what exactly is he anyway? Flipper is part of a unique-snowflake group of animals called Ichthyosaurs (think Ick!-theosaurs). Basically, a group of reptiles that were so well-adapted for a watery lifestyle that they look similar to other, equally well-adapted sea critters- like sharks, fish, and dolphins. It’s the body style that works best if you live your entire life in water, so they tend to look similar. Let’s take a look at some of those similarities, and what makes them so different!

what is it_ichthyosaur.jpg


So what’s the same?

I think everyone can agree that all three have the smooth, torpedo body style. They have powerful tails to push them forwards, and they all have at least one dorsal fin (the one at the top), and two pectoral fins (the “arm” fins). In short, they all have a body plan that is ideal for a life in water.

They all have sharp teeth and excellent senses for tracking down and chasing other aquatic critters for dinner. It varies depending on what’s more plentiful at the time, but there are definitely no peaceful vegetarians here.

And they all give birth to live young- even some sharks- though it depends on species when it comes to sharks. Ever heard of mermaids’ purses? Those are shark eggs. 😀

Photo copyright to Suzanne Guldimann, check out more lovely beach photos like this on her website at


Ok, so sharks need a quick explanation. Most have eggs, but only a few actually lay those eggs. What does that mean? It means most sharks have eggs, and most of those mamas simply hold onto those eggs until they hatch, and then keep the babies inside just a bit longer until they’re big enough to be born and take on the ocean.

A few sharks don’t have eggs at all, and the embryos develop inside just like mammal infants do. Some of them even have a placenta, which is a very special organ mostly unique to mammals. It’s a bit like a giant yolk sac and liver in one- it feeds the growing baby, filters out toxins, provides oxygen, and a whole host of other subtle things that makes an extended pregnancy run smoothly. 🙂

Which makes me wonder…how did Ichthyosaurs do it? It’s food for some healthy speculation, especially since there is so much variation in how some reptiles have live births too.


What’s different?

  • Skeleton- take a look inside and you’ll see bone for dolphins and Ichthyosaurs, but sharks have mostly cartilage. The same stuff that gives shape to our ears and noses.
  • Sharks have gills, but dolphins and Ichthyosaurs are air breathers.
  • Tails- a dolphin’s tail is horizontal compared to it’s body, but sharks and Ichthyosaurs have the verticle tail flukes. Plus Ichthyosaurs have bones in only the top fluke of their tails.
  • Fins- Dolphin has the least number of fins, one dorsal and two pectoral. Ichthyosaur comes next with one dorsal, two pectoral, and two pelvic fins. A shark has two dorsal fins, two pectoral fins, two pelvic fins, plus the little anal fin.
  • Skin- Dolphins have smooth skin, a bit like wearing a wet suit. Sharks have scales that look smooth but feel a bit like sandpaper. No one really knows what sort of scales or skin Ichthyosaurs might’ve had, but it would’ve appeared smooth like dolphin or shark skin.
  • Blubber! There is some evidence that Ichthyosaurs had blubber like dolphins do. Here’s a link to the paper. 😀
  • Fish vs. Reptile vs. Mammal- Sharks are fish, Dolphins are mammals, Ichthyosaurs were reptiles.

ichthyosaur comparison


So it’s not a shark, fish, or dolphin, but is it a dinosaur?

Ichthyosaurs are not dinosaurs! Take a look over at my “Which One is the Dinosaur?” post for a more in depth explanation as to why, but the short answer?

Crocodiles and birds are closer on the family tree to dinosaurs than Ichthyosaurs were. Birds are basically highly specialized dinosaurs that survived the mass extinction, and crocs are part of a line of critters that were the great gran-daddies to dinosaurs. So not dinos, but close relatives.

Ichthyosaurs are something else entirely. They were reptiles specialized for life in water.


Making Progress…


The clock is ticking! Only two more eggs to go before Babysaurus is here! 😀 I’ve been hard at work trying to get my buffer done so that we can still enjoy a COTM once Baby gets here. 🙂 Since I’m working on other monthly posts as well as the current month’s posts, I may be a lot quieter than usual when it comes to answering comments. I do try my best to answer them when I can though, and I read them all! Thank you for visiting! 🙂

I have officially entered the 3rd trimester! 3 more months to go! 😀


You know Spring is here when chicks are around! I thought I’d share a bit about the domestic dinosaurs I keep around here. 😀 And another reason I’ve been so busy lately.

painterly chicks.jpg
Cute little chickies! I didn’t really paint these. It’s just some pictures and photoshop magic 🙂

My new chicks arrived in the mail just a little over a week ago. 25 Cornish X roosters. They all have the same name- Chicken Nugget, or Chicken Pot Pie, or Chicken Enchiladas…Basically “insert favorite chicken meal here”, because these little guys are destined for a comfortable, but short life.

We don’t usually buy meat for a number of reasons I won’t bore you with here, so that means we normally have a lot of axis deer meat from a lovely hunter friend of ours. This pregnancy I’ve had a pretty fierce craving for chicken, but I don’t like the living conditions the poor birds at the grocery store have to suffer through before butchering day, so I thought we’d try our hand at raising our own. 🙂

They’ll have sunshine, a sheltered space to run, grass and dirt under their feet, bugs to chase…basically as good a life a chicken can have, just like our lovely egg layers. These chicks will have just one bad day, and we’ll have a freezer full of healthy, happy chicken.

Knowing where our food comes from is a valuable lesson here on the homestead, and I like trying to grow a garden too. I just have much better luck when it comes to critters…most of my poor plants don’t make it to harvest time. D:

painterly chickens.jpg

Here are two of my girls. I love how they have that stern gaze, so prehistoric! They are great egg layers, and I love watching them peck at bugs and grass in the yard. The only downside to letting them wander where they please is that they also poop where they please.

Down below is Big Daddy, and he always keeps a close eye on his girls. You think a velociraptor’s claw looks vicious? Well this big guy has a set of spurs that are every bit as nasty if he really has a mind for it. Good thing he has a healthy understanding that I outrank him. 😀

painterly rooster.jpg


Coming Next Week…

This little dino likes to party! 🙂

Share your guess in the comments! He’s one of the critters over on the critter page.🙂

18 thoughts on “Critter of the Month: Ichthyosaurus

  1. Very interesting! I definitely learned a lot about ichthyosaur/shark/dolphin anatomy today, and I really like the little illustrations you did. 😀 It’s funny, when you see them all side by side, they all look so different! I’ll never mix them up with insert-aquatic-animal-name-here again. 😛

    I thought the mermaid’s purse was especially cool–I don’t think I’ve ever seen a picture of a shark egg before (and if I did, I didn’t recognize it as one), but they’re nothing like what I expected! Its amazing how unique different types of eggs are, and thinking of how ichthyosaurs might’ve given birth is definitely food for thought. 🙂

    And your modern pet dinosaurs have finally made their debut! I really like the painterly effect you gave them, it adds a nice touch. Big Daddy looks very regal with The Claw. 😛


    1. Hi Brownie! I’m glad you like my little anatomy illustrations. I just wanted to draw a bunch of marine critters, and you’d think that would be easy! They’re deceptively complex critters to draw, because they’re not simply torpedo shapes. There are all sorts of powerful muscle groups to keep in mind when drawing them. 😀 They’re all fascinating critters, and I’d really like to explore more prehistoric marine critters.

      Alas, they don’t usually inspire very interesting stories no matter how much I try to convince my Muse otherwise. But then she’s usually pretty cooperative with little drawings like this, or more fun little story illustrations. 🙂

      Mermaid’s purses are very cool. This particular one usually belongs to a very specific group of sharks (I forget which) and skates. Others look more like a corkscrew. I haven’t come across it in any sort of paper, but I do wonder if any paleontologists have considered if Ichthyosaurs could carry eggs that then hatch inside for a live birth. Egg cases would be extremely delicate, and not likely to preserve unless the fossil was as pristine as the Burgess Shale (which will be awesome when I finally get to the Cambrian, by the way 😀 )

      Hehe, it’s about time my little raptor wannabees show up here! I quite enjoyed playing with their photos in Photoshop, especially since I’ve never really used that feature before to make a photo look like a painting. 😀

      Thank you for stopping by and chatting a bit! 😀


        1. Hi David! I do recall hearing about cat sharks laying the sort of egg cases we call mermaid’s purses. There are a few other reef shark species too, but most have the corkscrew style cases


  2. Good to see Flipper with the updated background. Anyway, could you please post that on Instagram and DTF?
    The colors remind of the CollectA Excalibosaurus. Could you please hunt that figure?

    I see, that’s why you didn’t reply to previous comments from me. And what name will you give to the Babysaurus?

    Anyway, Tango is next, really hope to see Pearl make her debut in the shop.


    1. Hi Angel! I’m glad you like Flipper. Of course I do plan on posting him on Instagram and and the DTF (and Elmer lol), and I’ll do it as soon as I can.

      As far as figures, I’m really not looking into getting any more for a while. and the only ones on my wish list are the genus featured in the picture book. 🙂 You’ll have to wait and find out for Babysaurus’ name. 😀

      Pearl might show up, you’ll just have to wait and see! 🙂


        1. Paleoteen, you have been increasingly rude throughout your time here on the site. I try my best to answer comments, but cannot answer them all, since I have a very busy family life I speak of often here on the site. Family takes top priority. I respectfully, but firmly advise that comments be polite and and respectful.


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