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Osmatar β How (I think) deinonychosaur eye sockets work
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#deinonychus #dinosaur #dromaeosaur #paleoart #speculative #theropod #velociraptor #maniraptora #paleontography
Published: 2014-10-13 20:34:22 +0000 UTC; Views: 12393; Favourites: 248; Downloads: 40
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I was doing a bit of research for a Velociraptor portrait I had planned, and experienced a moment of revelation I wanted to share. I was looking at pictures of various bird heads and skulls in comparison, trying to figure out what the eye should look like, and really stumbled on something that had been bothering me for a long time: those weird lacrimal protrusions or "horns".The bottom drawing represents the usual way of reconstructing the region of the eye. There's the lacrimal horn and a big gap between it and the postorbital. The sclerotic ring and consequently the eye are located high up in the eye socket. I am now convinced that this is incorrect.
The one on the top is what you would find if Velociraptor was a bird, or a squamate, or really any living diapsid. Instead of a gap, there is continuous tissue from the lacrimal to the postorbital forming a kind of brow that arches above the eye. The sclerotic ring and consequently the eye are slightly lower in the socket.Β
If you're not convinced yet, take a good look at bird and lizard skulls and compare them to the living animals. You'll find lots of the same kind of non-gaps. (There's also a Velociraptor mongoliensis skull that seems to have a longer than average arching bone stretching from the lacrimal, though the photo isn't that great). If you knew this already, well, good on you, because I'm the slowpoke who took decades to figure it out.
I'm not saying that this is fact and that I have conclusive evidence, mind you. I don't even have access to a real Velociraptor skull, just photos and a replica that's far from 100% accurate. This is just speculation based mainly on phylogentic bracketing for the time being, but I think it's more than reasonable.
Edit #1 : cleaned up the image from the original hasty scribblings. Content remains the same, it just looks a bit more presentable.
Edit #2 : My speculation has been confirmed by several sources, and I now have the proper term for the tissues streching from the lacrimal to the postorbital: supraorbital membrane. This structure is found in most sauropsids, but for some reason has been widely ignored in modern dinosaur restorations.
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Comments: 38
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I know that Davide Bonadonna came to a similar conclusion re Kaatedocus. It seems like palpebral elements like this may have been a norm for most dinosaurs with such skeletal anatomy.
i.pinimg.com/originals/90/c8/6β¦
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I think that you are absolutely right, I came to the same conclusions several years ago when looking at the skulls of some modern squamates. The lacrimal process is often simply misinterpreted, and the supraorbital "bridge" above the eye seems to be a universal trait for tetrapods.Β
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The structure does seem to be quite widespread. I've been told that crocodilians might be an exception to the rule, that their superciliary/palpebral bones don't work like they do in avians (and maybe non-avian dinosaurs), but from what I've been able to gather, it seems like it might be a unique and somewhat extreme adaptation to their semi-aquatic lifestyle. I'd love to know more about this, though.
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You are an awesome paleoartist, one of my favorites. You make these animals look very natural, you were one of my key references when making my own dromaeosaurs. Thank you.
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i've always felt that way after looking at birds of prey skull where that bone sticks out over the optics....which creates the skin over the eyes/shades. Most theropods have that bone sticking out, but not as apparent as the prey birds. Love it!
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Yeah, it wasn't as pronouced in deinonychosaurs as with most modern raptorial birds. However such ossified growths that support the supraorbital membrane are really much more common among aves that I had previously been aware of. Even chickens have such supraocular bones.
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i guess it's not as noticed because of how little pronounced they are in other aves, but more with the birds of prey im assuming to allow shade over the eyes when flying above prey to give them a clearer look(other than supporting the membrane). Even though theropods have it, it seems like some are more pronounced than others, especially when they become more airborne.
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here here!Β In general I feel like people have tendency of forgetting theΒ that eyes have shape. That there's an actual eyeBALL in the socketΒ and that all the tissue overlying it wraps around that form.Β Honestly I think this goes back to GSP and hes style. Hes work is very stylistic, very flat. It feels like most of the forms arent really rendered out, rather theyr implied with texture and patterns.Β And because GSP was so influential to so many of us, we learned to draw dinos by copying GSP's work repeating all of the good and the bad of hes works without getting proper understanding of what we were actually doing. What we did was pretty much analogous to what anime/manga peeps do. They draw their favourite charachtersΒ and learn to draw humans that way and that eventually leads them into trouble because they never made the effort to study actual human anatomy.
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Nice, makes sense. Kudos for a nice out-of-the-box.
Remember that old "Carnosaurs" illustration by John Sibbick? This is the best image I can find right now:Β 2.bp.blogspot.com/-uCxVrlE_xO0β¦
You're pointing out something both annoying and understandable: Trending 
It's easy to be annoyed at trending, but I think it's better to be understanding of it - while open to new discovery.
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I might as well add this little bit I found out a while ago. In short, you're right.
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Thank you! I now not only know the proper terminology but also feel a lot more confident about the supraorbital tissue. Maybe I should alter the title and description bit to reflect this.Β
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Since velociraptor lived in deserts, could this new brow be a kind of eye shade as well?
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The supraorbital membrane is by no means unique to Velociraptor, and I don't think it was any more pronounced than that of, e.g. the secretary bird.Β
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"lacrimal horns" in most small theropod dinosaurs have no dorsal extension or texturing to indicate the presence of cornified tissues relating to horns. Never have. Paul's ... work ... on the subject have been to romanticize the craziness of tissue in a fairly All Yesterdays approach to making shit up because it looks cool. He had no science to back it up, and plenty of evidence in living sauropsids (reptiles) to confirm otherwise. Work on ornithischian palpebrals has revealed the complexity of their supraorbital soft-tissues, and the result was that almost all orbits in dinosaurs are laterally bounded by some slight or expansive soft-tissue that under girds the brow. The lateral boundary of this tissue structure attaches from the rear of the lacrimal and arcs to the postorbital, where it attaches to a small process. This is true in most animals without very broad intororbital regions, but even in ornithischians with broad interobital regions as in ankylosaurs, this tissue is present and notable by the presence of overlying osteoderms.
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Thank you for chiming in. Your opinion means a lot to me and, I'm sure, many others here.
This has lacrimal confusion has taught me a lot about the dangers of trusting reconstructions too much, be they drawings, sculptures, 3D models or whatever, because very rarely is it clear what bones may have been embellished or otherwise incorrectly interpreted. Unfortunately even with at photographs of skulls it's not always clear how much is original material and how much has been filled in by human hand.
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It actually makes a lot of sense because lacrimal "horns" in dromaeosaurids don't have much of a dorsal process/cornual process, and they extend almost only laterally; I'm just as much lacking conclusive evidence as you on this, though.
Won't work with the skulls of most other theropod clades, I guess, but I might be wrong here; even those with pronounced lacrimal cornual processes - allosauroids, tyrants outside the Tyrannosaurus-Tarbosaurus clade - feature lacrimals that expand laterally in top view, and there might have been a similar connection to the postorbitals.
Makes one wonder about non-ossified palpebrals...
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Perhaps not most large theropods, but this condition seems fairly common to small-bodied and less derived theropods, such as coelophysids, Herrerasaurus, Eoraptor, basal coelurosaurs and so on. Of course you still see obvious gaps that would have been filled with tissue in theropods that clearly had lacrimal horns, Allosaurus being a prime example.
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Yeah, i think that's the case... Oh, and i'm also wondering if it's actually accurate to draw the lacrimal and postorbital "divided" in big theropods (except allosaurs and other horned ones)... What if, for example with T.rex and other horn-less tyrants, the postorbital and lacrimal rugosities formed, uhm, ridges sort of like in the JP sexy rexy?
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I think even in the horned tyrannosaurids the brow may have been continuous from the postorbital to the lacrimal, it just terminated in a horn-like protrusion.Β
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Glad to hear i'm not the only one to think that
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Going by the thumbnail, I originally thought you were going to comment on the ears. 
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It's the arrows, isn't it? 
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It's both the arrows and the blue lines under the lower ear subtly emphasizing it a bit.Β Not really anything to worry about since thumbnails often deceive anyway.
As for outer ears, I figure you're right about their using bird-like feather structures.Β Even so, a catgirl Deinonychosaur would look pretty odd, methinks.
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I always thought those were a sort of visor to dull excess glare from sunlight. However the top restoration looks more believable.
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Oh wow. I wonder if the same was true for tyrannosaurids?
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Having looked at some Gorgosaurus skulls (in photographs) I have to add that as I replied to Kazuma27, I think they may have had a continuous brow that the lacrimal horn was the tip of. I think a Daspletosaurus skull or two may even show this continuous brow, though it's never completely clear what you are looking at in a photo.
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T. rex definitely looks like it had a continuous brow.
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I've only looked at a couple of tyrannosaurids, and they don't seem to be really comparable. At least Gorgosaurus seems to have had actual lacrimal horns. Don't quote on me this, though!
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I wonder whether this applies to other theropod groups with laricimals? "LOOKING AT YOU ALLOSAUROIDS"
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Allosaurus definitely has an obvious gap between the lacrimals and the postorbitals, but the horns are still real. I suspect this will be most apparent in small coelurosaurs.
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I have a Velociraptor skull replica and several bird skulls, which made a three-dimensional comparison easy. I think you're absolutely right. I stopped drawing my theropods with lacrimal horns a while ago but I never really considered why: I'm amazed (and a little embarrassed) that I never noticed or thought of this before!
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I'm glad that I managed to illuminate the issue!
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