synapsida

Finally, it’s (sort of) done. Very, very simplified synapsid evolution. I started with basic eukaryotic cell, I didn’t even try to imagine what the LUCA was like. Probably some weird, virus-like thingy. I’m not sure I won’t tweak it a bit more, but for now, I consider it finished. I’m happy I managed to get it done now, as tomorrow I’m moving to a new address, and will be busy with cleaning, painting walls, more cleaning, and generally making the place hospitable, and won’t have time to paint or draw, so I’m glad I can at least upload this before disappearing for a while. I’ll also add this to my redbubble at some point.

So, the creatures are:

some generic cells, that weirdo that is Saccorhytus coronarius, a tunicate, Oikopleura dioica, because I was lazy, Pikaia, Haikouella, Haikouichthys, Pteraspis, Entelognathus, Guiyu oneiros, Tungsenia paradoxa, Tiniaru, Panderichthys, Tikataalik roseae, Acanthostega, Ichthyostega, Pederpes, Westlothiana, Echinerpeton, Pantelosaurus, Tetraceratops, Charassognathus, Dvinia, Prozostrodon, Adelobasileus, Hadrocodium, Teinolophos trusleri, Sinodelphys, Juramaia.

Now, Teinolophos (the monotreme) is known, of course, only form a jaw. It’s the oldest monotreme we have in the fossil record and can be a platypus relative, but can also be more basal than that. All we know for certain is: it had teeth as adult and didn’t have a beak. I had no idea how to restore it at first. All living monotremes are specialised weirdos. None have whiskers, for example. But, considering we don’t have anything that could be considered a generic monotreme, that begs the question: are whiskers therian thing, or mammalian thing, and extant monotreme lost them secondarily, because they just had to be wierd? Considering Teinolophos’s teeth, and the fact that it apparently had a rather strong bite (though how we know this is a mystery to me) it’s rather certain that it had a different lifestyle than that of any living monotremes. So, with that in mind, I decided to make it unlike any extant monotreme. And to give it whiskers, because I’m adventurous like that…

Though honestly, anything between Pantelosaurus and Sinodelphys/ Juramaia is known mostly from skulls (or fragments of skulls), so they’re all speculative to some degree. Also, I don’t think I need to say this, but none of them are drawn to scale.

And, while we’re on topic of I don’t think I need to mention it, but I will anyway:

The creatures I chose to paint here aren’t necessarily ancestors of anything that is alive today (and hell, the fish part of this painting definitely shows some non-ancestors (look at me, inventing words…), because we have the Zachełmie tracks that were left by something very much tetrapod-like, with four walking limbs, and tail and body held off the ground, and they predate Tiktaalik for about 12 million years, and Panderichthys by 10 million. I wonder if we’ll ever discover what left those tracks. That would be awesome! If only the fossil record wasn’t so patchy…

anonymous asked:

I asked another paleo blog but they never answered. I was wondering if dinosaurs are still considered reptiles since they are warm blooded and have feathers?

Yes, because reptiles is no longer defined by a set of characteristics - in fact, no group of organisms is anymore. That was the old way. 

Kids, hold onto your butts: we’re talking cladistics. 

Since the development of modern evolutionary theory, all organisms have been classified based on their evolutionary relationships. Meaning, Dinosauria is literally defined as the group of organisms containing the most recent common ancestor (MRCA) of Megalosaurus and Iguanadon and all of that MRCA’s descendants. (This, you’ll note, includes birds.) 

Now, the group that traditionally was reptiles no longer exists - instead it’s called Sauropsida, which doesn’t really have the best definition. My definition? All amniotes (yes, another clade) that aren’t members of Synapsida; or all the descendents of the MRCA of Parareptilia and Eureptilia… and there are some others too. All definitions, however include dinosaurs - so, yes, dinosaurs are still reptiles… if you consider Sauropsida to mean Reptiles… 

Which means birds are reptiles, too 

Science is fun!

Hey, look. It’s that Megaloceros giganteus portrait I started in April 2015… and finally finished.

Commonly known as Irish elk* or giant deer, M. giganteus lived in Eurasia during the Middle Pleisotcene and Early Holocene. It had the biggest antlers of any known cervid: it could reach up to 40kg in weight, and up to 3.64m across. In body size, it was similar to the Alaskan subspecies of moose, reaching on average between 540 - 600kg, with large specimens weighting 700kg or more.

It’s closest living relative is probably fallow deer (Dama dama)

*elk in British English is exactly the same animal as moose in American English. Don’t ask me why. Elk/moose live in Eurasia as well as North America, so it really doesn’t make any sens to me, but there you go.

So, I’ve made an anatomical study of everyone’s favourite giant hornless rhino.

Paraceratherium lived in Eurasia during the Oligocene epoch, and was one of the largest land mammals ever - its skull alone could reach 1.3m in length*. Exact size of Paraceratherium isn’t known due to lack of complete specimens, but it’s been estimated to be up to 7.4m long, 4.8 to 5.25m tall at the shoulder, and weight between 11 and 20 tonnes.

It was a browser, feeding on relatively soft plants.

I used modern rhinos’ and horses’ muscle systems for reference. And I’ve learned that there exist a shrink-wrapped reconstruction of Paraceraherium, with matchstick legs that in no way would be strong enough to carry animal of that size. Honestly, it’s the stuff of nightmares.

* for reference, I’m 1.58m tall. Sure, that’s not much, but it’s still pretty mind-boggling to think about something’s head only 28cm shorter than me.

I’ve been playing with animation lately, and this is the first half-decent one I made. Although I have no idea why the background is sort of glitchy… I also mixed the sound for this (which was pretty fun in its own right).

Basilosaurus doing important, prehistoric whale stuff. At first I wanted the whale to stay in the middle of the screen, and have the illusion of it moving forward created with the background, but… this proved to be far more difficult than I imagined, so I moved the whale instead. Probably shouldn’t have chosen water for my first animation…

I already have an idea for something a bit more complicated, but no clue when I’ll have time to do this.

And as a side note, for some reason the software I’m using doesn’t render video files properly (though it should, and it does for other people), and I have to render every single frame as png and then make them into a movie. Bit annoying.

I don’t have time for anything lately, so here’s a silly drawing of a Thylacosmilus atrox I did about two weeks ago and didn’t have time to upload it until now. Inspired by the jowls cat/chin cat discussion, and also by my dog :P

I’ve decided to combine big jowls with big chin, because the idea of sabers covered entirely by really long, floppy jowls doesn’t strike me as very comfortable for the animal, and sabers covered only by sort of flesh-sheaths on the mandible also don’t seem comfortable, so I went with somewhat floppy jowls covering the top part of the teeth, and partial sheaths on the lower jaw covering the rest.

And also, by looking at today’s predators, I’d guess that Thylacosmilus spent a lot of its time doing what predators do best: being lazy.

Thylacosmilus lived between the Late Miocene to the Late Pliocene in South America, and I’d be very surprised if they didn’t flop on their backs at least from time to time.

Castorocauda lutrasimilis catching breakfast. I’m not sure about the hind leg, but I was too lazy to change it.

Castorocauda was a semi-aquatic docodont that lived about 164 million years ago, during the Jurassic period, in what today is Inner Mongolia. It was a piscivore, that also supplemented its diet with invertebrates.

It was mammaliaform, but not a mammal.

It could reach a little over 40cm in length, and between 500 to 800g in weight.

The name Castorocauda lutrasimilis means beaver-tail similar to otter.

The holotype preserves extensive coat of fur, and also small scales/scutes on the tail. The tail was also covered in sparse hair.

anonymous asked:

Could you maybe clarify all the terms on your cladogram? I mean I know that they're all defined by evolutionary relationship and stuff but maybe both define them AND provide an example animal? I'm just a little confused by some of the names...

Oh yeah, sure! 

Chordata (Brick Red): Tunicata + Craniata + Cephalochordata; their most recent common ancestor, and all its descendants. Typically characterized by having a notochord, a dorsal neural tube, pharyngeal slits, a post-anal tail, and an endostyle at some stage of their lives. Examples include hagfish, sea squirts, sharks, sea bass, lungfish, frogs, humans, birds, and lizards (all vertebrates are chordates). 

Vertebrata (Red): Myllokunmingia + Gnathostomata (+ MRCA and all descendants); typically all chordates that have a backbone. Includes: sharks, sea bass, lungfish, frogs, humans, birds, lizards, and lampreys. 

Gnathostomata (Brown): Chondrichthyes + Placodermi + Teleostomi (MRCA & des.; jawed vertebrates. Includes: Sharks, sea bass, lungfish, frogs, humans, birds, and lizards. 

Placodermi (Beige): All gnathostomes more closely related to Dunkleosteus than to any living “fish”; these are the “armoured fish” that had huge armor plating on their heads. All non-placoderm Gnathostomes are in Eugnathostomata. Includes Dunkleosteus; all are now extinct. 

Chondricthyes (Orange): All Eugnathostomatans more closely related to Carcharodon than to humans; is all cartilaginous fish. Originally it was thought that bony fish evolved from cartilaginous fish, however, it has since been found that both diverged from a common Placoderm ancestor. Includes sharks and rays. 

Teleostomi (Yellow): All Eugnathostomatans more closely related to humans than to Carcharodon; “bony fish”. Includes sea bass, lungfish, frogs, humans, birds, and lizards. It is subdivided into Acanthodii & Euteleostomi. 

Actinopterygii (Olive Green): All Euteleostomis more closely related to sea bass than to humans. “Ray-finned fish”. Includes sea bass, clownfish, tuna, and goldfish. 

Sarcopterygii (Lime Green): All Euteleostomis more closely related to humans than to sea bass. “Lobe-finned fish”. Includes lungfish, coelacanth, frogs, humans, birds, and lizards. 

Tetrapoda (Light Green): Frogs + Humans, MRCA & all its descendants. Essentially, all land vertebrates - there are many forms of lobe-finned fish that were able to crawl onto land that form Tetrapoda’s most recent ancestors, but tetropoda proper is just all the descendants of the MRCA for all modern land animals (amphibians, sauropsids, and mammals). Includes frogs, humans, birds, and lizards.

Lissamphibia (Green): Caecilians + Frogs, MRCA & all its descendants. Essentially amphibians, though it excludes many extinct amphibians (when you use the term amphibian to mean all non-amniote tetrapods). This might not actually be a proper cladistic group, but I included it as it definitely does not contain any amniotes. Includes caecilians, frogs, and salamanders. 

Amniota (Dark Green): Humans + Birds, MRCA & all its descendants. All hard-shelled-egg laying land animals (specifically, they produce an egg with an amnios, allowing the animal to lay the egg on land, rather than water). Even though many mammals (and some reptiles!) have secondarily lost this ability, their ancestors did have it, making them a part of this group. Includes humans, birds, and lizards. 

Synapsida (Seafoam): A group of amniotes that includes mammals and all amniotes more closely related to mammals than other living amniotes. Synapsids are not reptiles; though many non-mammalian synapsids resemble them heavily. They are easily characterized by their skulls: many amniotes have temporal fenestra (a hole behind their eye socket); synapsids only have one of these. Most reptiles have two. Includes Dimetrodon, humans, and whales. 

Mammalia (Teal): Platypus + Humans, MRCA & all its descendants. All mammals, essentially. Mammals are typically characterized by the ability to produce milk from mammary glands. Most don’t lay eggs, but either give birth to their young in a pouch (marsupials) or grow the young inside of a placenta (placentals, aka us). Includes echidnas, humans, whales, and kangaroos. 

Sauropsida (Aqua): All amniotes more closely related to birds than to mammals. Essentially reptiles. Since birds and dinosaurs are included in this group, there aren’t a whole heck of a lot of good unifying characteristics. Many sauropsids are endothermic (warm-blooded); many have feathers in addition to scales; and some even give birth to live young. Includes turtles, plesiosaurs, lizards, tuatara, snakes, mosasaurs, icthyosaurs, crocodiles, pterosaurs, dinosaurs, and because it includes dinosaurs, birds. 

Lepidosauria (Dark Purple): Lizards + Tuatara, MRCA & all its descendants. Characterized by having overlapping scales. A part of the larger group Lepidosauromorpha within Sauropsida. Includes lizards, tuatara, snakes, and mosasaurs. 

Squamata (Purple): Lizards + Snakes; MRCA & all its descendants. Characterized by skins with horny scales and shields, and can move the upper jaw as well as the lower jaw (not something most jawed vertebrates can do). Includes lizards, snakes, and mosasaurs. 

Mosasauridae (Lavender): Mosasaurus + Plioplatecarpus, MRCA & all its descendants. The mosasaurs - large marine reptiles, similar to monitor lizards, but elongated and streamlined for swimming. Extinct now. Includes - you guessed it - Mosasaurus, as well as Tylosaurus and many others. 

Serpentes (Fuchsia): Blind snakes + Vipers, MRCA & all its descendants. Essentially all snakes. They’re distinct from lizards due to lack of eyelids and external ears - there are many legless lizards, but snakes are a specific group of “lizards” (given that squamates on the whole can be called lizards). Includes the garter snake, blind snakes, and cobras.  

Ichthyosauria (Hot Pink): All animals more closely related to Icthyosaurus than to Grippia; essentially, a group of sauropsids not a part of Lepidosauromorpha or Archosauromorpha. They were adapted for completely aquatic life and are now completely extinct; they sort of looked like dolphins. Includes Icthyosaurus, Opthalmasaurus, and Mixosaurus. 

Archosauromorpha (Azure): Birds + Crocodiles + Turtles, MRCA & all its descendants. Essentially all modern sauroposids more closely related to birds than to lizards, though of course it includes many extinct groups as well that are descended from their most recent common ancestor. This is a very diverse group with a wide variety of characteristics. Includes turtles, plesiosaurs, crocodiles, pterosaurs, dinosaurs and therefore birds. 

Pantestudines (Dark Violet): All sauropsids more closely related to turtles than any other animal. A group of archosaurimorphs. Genetic analyses have shown strong evidence that they are more closely related to archosaurs than to lepidosaurs; these genetic analyses that include fossils also reveal that animals such as plesiosaurs and placodonts are in this group. Includes turtles, plesiosaurs, Liopleurodon, and Placodus.   

Plesiosauria (Plum): Plesiosaurus + Peloneustes, MRCA & all its descendants. The plesiosaurs - the long-necked (though many lost this) marine reptiles from the Mesozoic. This group also includes the pliosaurs, which on the whole lost the long necks characterizing the group. Includes Plesiosaurus, Elasmosaurus, Kronosaurus, and Liopleurodon. 

Testudines (Violet): Xinjianchelys + Trionyx, MRCA & all its descendants. Essentially, all modern turtles - characterized by having a shell developed from the ribs that acts as a shield. The classification of turtles has been a struggle, given that they are anapsids - meaning, they have no temporal fenestra. The earliest amniotes were anapsids and it was assumed from fossil evidence that turtles, therefore, were descended directly from them, and were not part of any more derived amniote groups (such as synapsids or archosaurs). Most sauropsids are diapsids - meaning, they have two temporal fenestrae. It has since been theorized, however, that turtle ancestors were diapsids; turtles actually lost their temporal fenestrae during their evolution. This is not a completely ridiculous idea, of course; many traits are secondarily lost in groups, making classification by traits a nightmare and unfeasible. Genetic analyses have revealed that the closest living relatives for turtles are crocodiles and birds, making them a part of Archosauromorpha. Includes Green sea turtles, the African spurred tortoise, and terrapins such as the Red-eared turtle. 

Archosauria (Cerulean): Crocodiles + Birds, MRCA & all its descendants. Characterized by having teeth in sockets, though some archosaurs (such as birds) lost their teeth secondarily. Many members of the group have erect or partially erect gaits, unlike other sauropsids, which have sprawling gaits (such as lizards). Archosaurs were the dominant land vertebrates for the entirety of the Mesozoic Era (though dinosaurs were only really during the Jurassic and Cretaceous; a wide variety of archosaurs were common throughout the Triassic). Given that birds are far more diverse than mammals; it can still be argued that archosaurs continue to be the dominant land vertebrates today. Includes crocodiles, pterosaurs, dinosaurs and therefore birds. 

Pseudosuchia (Aqua): Living crocodilians and all archosaurs more closely related to crocodilians than birds. They have massively built skulls, and many still have the typical reptilian sprawl, though some have an erect gait. They typically also had armored plates. Includes crocodiles, alligators, Deinosuchus, phytosaurs, and aetosaurs. 

Ornithodira (Indigo): A subgroup of Avemetatarsalians, which is all archosaurs more closely related to birds than to crocodiles. Ornithodira is, specifically, Dinosaurs + Pterosaurs, MRCA, and all descendants (Ornithodira was easier to fit into the diagram). This group potentially has protofeathers as a characteristic of the entire clade, though many lost them secondarily (such as hadrosaurs). Includes almost all flying vertebrates. Members include Scleromochlus, all pterosaurs, all dinosaurs and therefore all birds.  

Pterosauria (Blue-Violet): Anurognathus + Preondactylus + Quetzalcoatlus, MRCA & Descendants. The pterosaurs. These are all of the “flying reptiles” that one typically knows about from the Mesozoic Era. They had pycnofibres - small filaments similar to hair, potentially the same as protofeathers; and flew using membraneous wings that stretched across an extended finger. Includes Dimorphodon, Pteranodon, Pterodactylus (”pterodactyl”), and Ornithocheirus. 

Dinosauria (Blue): Megalosaurus + Iguanodon, MRCA & descendants. All dinosaurs. Note that this does not include many of the animals listed above! Dinosaurs are a very specific group of animals that all, typically, were able to walk with the limbs directly beneath the body. Protofeathers were also an ancestral trait for this group, though many dinosaurs secondarily lost them - the same proteins that make protofeathers were turned into scales. Includes Brontosaurus (yes, it’s a thing again, there was a study this year), Stegosaurus, Triceratops, Tyrannosaurus, Allosaurus, Velociraptor, Brachiosaurus, Troodon, Parasaurolophus, Ankylosaurus, Pachycephalosaurus, Archaeopteryx, the Dodo, Bald Eagles, Emus, Cassowaries, Chickens, Ducks, Finches, Parrots, Robins, Crows, Geese, Blue Jays, Penguins, Auks, Seagulls… 

Avialae (Light Blue): All dinosaurs more closely related to modern birds than to Troodon. This is typically the group I mean when I say “birds,” though the clade that includes only modern birds is called Neornithes - all non-Neornithes Avialaens are extinct. Many basal Avialae, furthermore, are almost indistinguishable from their closest dinosaurian relatives, the troodontids. It is uncertain whether the earliest Avialaens (such as Archaeopteryx) could properly fly. Includes Archaeopteryx, Confuciusornis, Hesperornis, the Dodo, Bald eagles Emus, Cassowaries, Chickens, Ducks, Finches, Parrots, Robins, Crows, Geese, Blue Jays, Penguins, Auks, Seagulls… essentially, all birds. 

I hope that was helpful!

I think this guy is finished… I’ll have to check tomorrow, when I’m actually somewhat awake. I have two versions of this, with one minor difference, but I’m just to tired to decide now which one is better (or if I still need to fix something, add some shadows, and so on).

But anyway, 2 pictures done, 10 more to go!

And a little bit about Haptodus: it’s the most basal sphenacodontian, and member of a lineage that eventually led to mammals. It lived during the Late Carboniferous and Early Permian (299 - 296.4 Ma). It was about a medium-size predator, with individual sizes varying between 60cm and 1.5m in length. It fed on arthropods and small vertebrates. I based my reconstruction on H.garnettensis ( or H. baylei, depending on whether baylei is a valid species or not.)

It’s lying on Cordaites leaves.

Next one will be Pantelosaurus or Tetraceratops.

Dimetrodon grandis, a large Sphenacodontid from the Early-Middle Permian. Despite being a reptile, Dimetrodon is actually more closely related to us than to any contemporary reptile group. It used its large sail for thermoregulation, turning to the sun when it needed to warm up. The sail also may have had a role in sexual reproduction, as well as a threat display.

oldoddandowly  asked:

Which would be more closely related to a dimetrodon: a modern mammal like ourselves or a dinosaur? Is there a way to quantify how closely related a species is to another?

Yesssss! Yes there is! It’s called phylogenetics, the study of evolutionary relationships, and its most comprehensively illustrated in phylogenetic trees! Take this one for example: 

This is a pretty simplified tree, meaning there are a lot of other animals missing, but for our purposes key players are included. You can see where tetrapods (Tetrapoda [these are four-legged animals]) split off between amphibians, and those animals that lay their eggs on land. From there, the tree splits again between reptiles and synapsids - meaning we’ve got a common ancestor with animals like reptiles (but NOT reptiles) before diverging into Synapsida and Reptilia.

From there, reptiles divided and branched out, and you can follow the tree down to see the close relationship between dinosaurs, birds, and crocodiles. But check out the other limb - the Synapsid limb. Dimetrodon was a Sphenacodontid. The limb branches and branches and eventually you get the Mammals. While we aren’t direct descendants from Dimetrodon, we fundamentally share common ancestors of those animals. 

So, to answer your question: Dimetrodon is more closely related to ALL modern mammals than it was to any dinosaur. 

For more information, check out Ken Angielczyk’s blog in The New York Times!

sabrielhasablog-blog  asked:

Emily, what IS a dinosaur? We grow up playing with dinosaur toys and watching Juraissic Park and a lot of us think we know all about dinosaurs, but nobody ever talks about why they're dinosaurs and not just big reptiles... What are the traits that makes a paleontologist go, "Yep, that's a dinosaur!"

Great question!

“Dinosauria” is a clade, a grouping that includes a common ancestor and all the descendants (living and extinct) of that ancestor. So, any animal that has been determined to fall within this clade is a dinosaur. In order to be classified as such, however, that animal has to meet certain criteria with genetic characteristics which have been inherited somewhere along that evolutionary line.

For instance, birds are classified as avian dinosaurs (a T. rex would be a non-avian dinosaur) because they evolve from a commonly shared ancestor as other dinosaurs. Because of these genetic relationships, members of a clade have many physiological common traits - like, all dinosaurs have an opening in the socket of their pelvises and carry their legs directly beneath their bodies (alligators’ and those of lizards sprawl out to the side). There can be a lot of variation, too - but morphologies alone cannot determine species relatedness, like the presence of wings and flight ability ‘cuz convergent evolution is a thing.

Dimetrodon is not a dinosaur because it’s in a different clade - Synapsida - which began evolving around 308 million years ago, 77 million years before Dinosauria existed. These two groups broke apart very early on and evolved completely independent of one another. As a result, humans and all mammals are Synapsids, distant relatives of those early, sail-back creatures, and birds evolved within Dinosauria. 

Evolution.

Angielczyk, K. (2009) Dimetrodon is not a dinosaur: Using Tree Thinking to Understand the Ancient Relatives of Mammals and their Evolution

Nesbitt, S. (2011) The Early Evolution of Archosaurs: Relationships and the Origin of Major Clades