“Atopodentatus unicus” is the freakiest tetrapod I have ever known; a marine reptile with hoof-like claws, a curved upper filled with hundreds of needle-like teeth, and a cleft that splits the upper jaw in two that has teeth inside it like some kind of Lovecraftian, eldritch abomination of evolution.

And I freaking love it.

Check it out.

jummbl asked:

How likely do you think it is that the marine reptiles (mosasaurs, elasmasaurs, etc) had labial scales? Extant lizards have them, but I only see reconstructions with the teeth menacingly showing.

Well, let’s consider the different clades of marine reptiles. Labial lips are a basal condition of reptiles, and thus if a marine reptile does not have labial lips we can assume that they were lost for ecological reasons. First, mosasaurs. They are closely related to the extant varanoids (which include komodo dragons and other monitor lizards), which do have labial scales, and thus it’s safe to assume that mosasaurs had them as well. Sideshow Dinosauria’s model of a Mosasaurus, for example, has labial scales.


Now, the sauropterygians. There’s not really any information about labial scales in this clade, so let’s examine it on a case-by-case perspective. Some of the later plesiosaurs, such as Styxosaurus, had spiky teeth coming out at angles from its jaws, and it’s hard for me to imagine that they had any kind of lips, much less labial scales. Earlier plesiosaurs might have had them, though.


As for pliosaurs, the same goes. There are snaggy-toothed taxa and non-snaggy toothed taxa. Liopleurodon, for example, is a snaggy-toothed taxon, but the more derived Pliosaurus is not. It’s possibly a mixed bag with isolated cases of labial scale and lip loss but also some lipped but scaleless genera with teeth pointing out here and there. Rhomaleosaurids are generally shorter-toothed and so probably had them. 



(here, this one isn’t necessarily right or wrong)

Considering ichthyosaurs were generally short-toothed and had an organized set of teeth, they would definitely have had lips, if not labial scales (aesthetically I prefer them without, but again we don’t know).


Considering placodonts were among the more primitive sauropterygians and generally ate harder prey (as indicated by the shape of their teeth and skull), it’s safe to say that they had a considerable amount of visible scalation on their heads, including labial scales.



As nothosaurs were generally snaggle-toothed, they most certainly wouldn’t have had lips or labial scales.


The thalattosuchians (the metriorhynchids and the teleosaurs) were close relatives of the crocodiles that still live today - they’re commonly referred to as marine crocodiles. Crocodiles are among the reptilian lineages that have lost their lips and thus labial scales secondarily. Although we can’t explicitly tell when this loss happened, it may (I stress, may) be safe to assume that thalattosuchians didn’t have labial scales.



But the conclusion is, we really don’t know, and we can only extrapolate so far. Ultimately it comes down to the artist to decide how they want to depict the marine reptile, with or without labial scales. Of course, there may be something in the literature that I’ve missed; in any case it’s a good idea to also ask Jaime Headden (blog, dA), as he is fairly knowledgeable about lips in extinct animals.


While the era of dinosaurs is now fairly fixed in the popular consciousness, far less attention is given to the reptiles of the same time period that returned to the sea. While not dinosaurs, these reptiles too reached impressive proportions- and gained traits, like live birth and warm-bloodedness, that we now associate with mammals.

Take my hand and I’ll walk you through the world of seafaring reptiles, all the way back to diminutive Mesosaurus 300 million years ago…