#amniotes

Now, keep in mind that these were really primitive creatures in the lineage that eventually led to mammals. If you look at the skeleton of a Diadectes, for example, you'll notice that the spine has lumbar ribs, which suggests that it likely hadn't yet evolved a diaphragm, which helps with breathing when moving at high speeds.

But wait--what is that SKULL?

This is the most cartoonish skull I have ever seen! I mean, the poor guy looks like T. rex's dorky, uncool cousin.

Look, I know Diadectes lived before amniotes began to evolve fenestrae (holes) in their skulls to make great places to anchor tendons and muscles for stronger and wider bites. I still wouldn't want to get bitten by this critter, but the first thing I legitimately thought of when I first saw this photo was...

So from now on whenever I picture a life restoration of Diadectes in my head, this is what I'm going to see in my head:

So far, we've learned about the earliest vertebrates and fishes and how one branch of those fishes grew legs and became the first amphibians but something even more amazing happened during the Carboniferous Period: the amniotic egg.

What is an amniotic egg? It is an egg that is adapted to retain water without needing to be in water. In other words, an egg with a shell (either soft or hard). Of course, just like living on land required more than just legs, amniotes (animals that produce an amnion) needed more than just a protective shell.

Fish and amphibians only have one inner membrane, the embryonic membrane. Amniotes have four: the yolk sac which surround the yolk, the amnion which surrounds and cushions the embryo, the allantois which helps with gas exchange and waste removal (becomes the umbilical cord in mammals) and the chorion which is the outer most membrane and surrounds everything.

Amniotes also lack otic notches because they are fully terrestrial (yes, some are secondarily aquatic but that is for a later discussion). Instead, they have extra holes in their heads for muscle attachments and to lighten the weight as amniotes can grow quite large.

Anapsids are the ancestral condition. These early amniotes lacked the temporal fenestrae that the other two groups have. Turtles are anapsids.

Synapsids have one set of lateral temporal fenestrae. Synapsids include mammals and their ancestors like us and Dimetrodon.

Diapsids have two sets of temporal fenestrae in their skulls. These include reptiles, dinosaurs and birds.

Other traits of amniotes include two pairs of sacral ribs (generally fused to the vertebra and the rest of the sacrum)

a sternum (some amniotes have lost this secondarily)

and an ankle bone called the astragalus.

Now that we know a little bit more about amniotes, tune in tomorrow for some trivia! Fossilize you later!

Skin is hard to find in the fossil record. The outer flesh of ancient organisms is much more prone to being eaten by scavengers or rotted away than sturdy bones are. But sometimes paleontologists get a lucky break. Within the roughly 288-million-year-old recesses of a cave in Richards Spur, Oklahoma, paleontologists have found truly ancient fossil skin impressions that were preserved in a very unusual way. Described Thursday in Current Biology, these tatters of fossil skin and various skin impressions come from some of the earliest amniotes. The lizard-like animals were some of the first creatures to live their entire lives on dry land, away from the water’s edge, and their bodies were covered in pebbly, scaly skin. The newly uncovered fossils are the oldest record of preserved skin yet found, about 130 million years older than the previous record holder, containing not only the exterior texture of the skin but also the internal structure of the epidermis.

Two of the biggest advances in tetrapod evolution was the addition of two very special cervical (neck) vertebrae: the atlas and the axis. These came with a group called amniotes.

You might be wondering why two little verts could be such a big advancement. The atlas and axis are the first two vertebrae in the cervical sequence. The atlas (C1 if you will) holds up the skull just like the titan Atlas holds up the Earth in Greek mythology.

The atlas allows us to nod our heads up and down.

The axis (or C2) is the next in line. This vertebra allows us to turn our heads from side to side.

In other words, these two little vertebrae give us an incredible range of motion that amphibians and fish lack. Take a look at their skull attachments:

Fish and amphibians have to turn their entire body in order to look in a different direction while other vertebrates can simply spin their heads on their very special cervicals. Neat, huh?

🐢 Turtally Amazing #Reptiles #Turtles #Nature

You know, I am always fascinated when I see some little critter (with the exception of snakes or anything venomous) that inhabit the natural areas in our yard. We live in a well-populated area, albeit in the country, yet still the miracles of nature never cease to amaze me. Yesterday morning while making up my bed, I looked outside my window towards my neighbors house and saw something near…

Hmmmmm no pun intended huh............. really?