Discussion: Surface texture on ceratopsians

[Lanthanotus]

I was thinking of ceratopsian horns. The new Safari Triceratops aswell as the older Nasutoceratops have both a completly smooth and featureless surface on their horns, while on most other ceratopsian figures from different companies you find either grooves along the length (for example CollectA dead Trike, Favorite Styracosaurus) or cracks as on old bones or old ivory (Papo Trike). Now, while the horns of ceratopsians have a bony core from where they grow, the actual horn (sheet) is made from keratin, the same material hair, feathers and scales are made from, a very versatile stuff.

Depending which kind of animal a horn develops, the surface texture varies. Rhinoceros for example have no bony core within their horn, just a bulked up bony base from which the horn grows. In their case the horn is made from modified hair which clings together and grows steadily from the base. The general form of this horns can vary greatly as the form depends on how the rhino uses and treats it... while some brush their horns on bushes, other use trees and stones or just the sandy ground. So some horns look rather thin and long while others are broad and blunted. The surface of those horns naturally shows narrow grooves along the length or is rather smooth on where the animal mostly brushes it against things.

Ruminant horns are differnt, because as ceratopsians they have a bony core from which the horn grows. However, the general form and surface texture of ruminant horns varies greatly. While bovines usually boast a very smooth and featureless surface, the horns of goats are somwhat corrugated  and antelopes often show bulges and keels.

However, all these animals are mammals with a general hairy skin (even if rhinos lost most of it).

True horns are scarce amongst recent reptiles. Most reptile "horns" are just enlarged scales with no underlaying bony structure. However, the genus Trioceros (like Jackson's Chameleon) has horns that grow from a bony horn underneath (click). As these horns grow from a scaly skin that frequently sheds, I was thinking if the general surface structure of ceratopsian horns would not rather be depicted as in the linked picture, with a corrugated pattern somewhat like stacked up pancakes.

What do you think?

[amargasaurus cazaui]

All of the horn cores I have ever examined or had were not like the "pancake" effect you pictured.....they are large, broad at the base and taper ....and the surfaces show grooving and vascular channels making them less than smooth. Apparently the keratin covering is what tapered and became sharp as the cores themselves are rather broad and blunt .

[amargasaurus cazaui]

All of the horn cores I have ever examined or had were not like the "pancake" effect you pictured.....they are large, broad at the base and taper ....and the surfaces show grooving and vascular channels making them less than smooth. Apparently the keratin covering is what tapered and became sharp as the cores themselves are rather broad and blunt .

As an aside I had asked and am wondering if anyone else had compared epocippitals, vs horn orientation on the new Safari model or noticed it at all?

[Lanthanotus]

All of the horn cores I have ever examined or had were not like the "pancake" effect you pictured.....they are large, broad at the base and taper ....and the surfaces show grooving and vascular channels making them less than smooth. Apparently the keratin covering is what tapered and became sharp as the cores themselves are rather broad and blunt .

Thanks for your post, amaragasaurus cazaui. To make sure, my point was about the surface texture of the part of the horn as visible on the living animal. The horn core (to my understanding currently the only part of it known from the fossil record as I have not yet heard about the keratin sheet being preserved) that is seen on actual skulls and casts and so the only "horn" the general public knows from ceratopsians is for sure not in any way smooth (and if it should be an artefact of taphonomy) but as you described grooved or cracked.

"Reptile" is a quite ill-defined term in a biological sense if you want to bring all those different animals together as todays reptiles (as you know a quite variable group of organisms that are not very closely related compared to others despite several characteristics that make them appear related) and whole clades as dinosaurs or even birds.

So the above questions persists.... how did the actual horn appear in the living ceratopsian and therefor should appear in models and figures? Did Triceratops grow and develop skin and horns like a reptile, similar to recent reptiles as Jackson's Chameleon? Did they appear as in cows or bovines (as suggested by Safari's new Trike)?

[Patrx]

Great question! I often wonder about this, myself. This recent blog entry by Mark Witton is more about the shape and growth of dinosaur horns, but their surface texture is explored as well. He predicts something similar to bovid horn. Visibly layered, but not striated like rhino horn:

[Neosodon]

Wouldn't the horn sheath just brake as the horn grew and changed shape or is keratin really that flexible?

[Lanthanotus]

Keratin can be both, being hard and kind of brittle aswell as being very bendy and flexible, it's determined how the molecules are fitted together by the organism to form such different structures as hair, feathers, scales, plates or horns. So while a horn may break and crack from some traumatic happening it does not usually break from growth.

[Dinoguy2]

Wouldn't the horn sheath just brake as the horn grew and changed shape or is keratin really that flexible?

If I'm reading right, the horn would not change shape, it would just grow out from the base. Thinking about the bony core only, in juvenile Triceratops it curves backwards. In adults the horns arc forward but the TIPs still curve up a bit. That little upward curve represents the entire baby horn, which is now merely the tip of a much larger adult horn. That's why Witton shows big curving tips in the adult. Presumably the juvenile horn had long back curve keratin extensions and those would still be present in the adults.

Horn growth was additive from the bottom out, not shape changing.

[amargasaurus cazaui]

Wouldn't the horn sheath just brake as the horn grew and changed shape or is keratin really that flexible?

If I'm reading right, the horn would not change shape, it would just grow out from the base. Thinking about the bony core only, in juvenile Triceratops it curves backwards. In adults the horns arc forward but the TIPs still curve up a bit. That little upward curve represents the entire baby horn, which is now merely the tip of a much larger adult horn. That's why Witton shows big curving tips in the adult. Presumably the juvenile horn had long back curve keratin extensions and those would still be present in the adults.

Horn growth was additive from the bottom out, not shape changing.

This is what I was trying to reference before, the shape of  the horn at various stages of ontogeny...now the million dollar question...how did ontogeny affect the epocippitals?