1
$\begingroup$

For horned animals, there are two common configurations of cranial horns.

  1. One long horn above the nose (Styracosaurus, Rhino).
  2. Two long horns above the eyes or forehead (Triceratops, cattle, African Buffalo).

In many species, the cranial horns are used as a weapon: both for intra-specific combat (e.g. dueling over mate) and defense against predators.

My question is which configuration is more effective and lethal: 1 nose horn or 2 brow horns? I suggest dividing the answer into two categories: Ceratopsid dinosaurs and extant mammals.

$\endgroup$
5
  • $\begingroup$ Why might that be that the vast majority on horned animals are two horned? $\endgroup$ Commented Feb 10, 2023 at 13:59
  • 1
    $\begingroup$ In dinosaurs, single-noseed-horned ceratopsids were abundant as well. $\endgroup$ Commented Feb 10, 2023 at 14:47
  • 1
    $\begingroup$ My question is about the present, not the past. Did you do any research about this yourself? What did you find out? On this site, failure to present some search result is a reason to down vote and close vote, so if you're done any, it would be beneficial to you to quote and link to it. $\endgroup$ Commented Feb 10, 2023 at 14:53
  • 4
    $\begingroup$ Also at play are other components of anatomy: stature, closeness to ground, skull strength, neck muscles, core/limb design/musculature... Not to mention environmental drivers for these adaptations: substrate texture, compaction, slope, etc. In the end, asking which is better isn't really a great biological question. Both evolved in response to ancestral morphological traits adapting to different environments/behaviors. I don't think the question needs to be closed, per se, but I think it's a low quality question as written. I hope the eventual answer includes mention of the issues I raise. $\endgroup$ Commented Feb 10, 2023 at 17:19
  • $\begingroup$ this is pure opinion, what is best is going to depend on the rest of the skull and the rest of the animals anatomy, how it can move and balance. then you have to consider lethal against what? different attacks work differently against different predators. $\endgroup$
    – John
    Commented Feb 18, 2023 at 4:08

1 Answer 1

5
$\begingroup$

Note

Since a lot of people are upvoting this (and some downvoting of course), it's worth noting that it's not directly answering the OP's stated interests of dinosaurs etc. However, I think it's probably a more useful answer in general for people interested in horned animals.

Not intended to be the only answer on this question!

Answer

This doesn't fit neatly into your dinosaur vs mammal dichotomy, given the obvious differences in ecology and biomechanics, but I would suggest looking at horned beetles to think more about the effectiveness of horn weapons in different contexts. In some cases both configurations you describe (among others) are present in the same species and vary widely in the same genus.

horn morph variation in the genus onthophagus

One review paper here suggests that behavioral variation can account for the presence/absence of horns across species:

Thus, tunneling likely set the stage for the evolution of one-on-one fighting in tunneling taxa, such as Onthophagus, and the evolution of weaponry, such as horns, that is useful in one-on-one combat and in the blocking of narrow tunnels to prevent other males from accessing the female.6,26 Consistent with this scenario, horn possession is widespread and elaborate in tunneling scarabs, where it appears to have evolved independently several times, yet is virtually absent in any other group of non-tunneling scarabaeine beetles.31

One paper cited in that review presents phylogenetic comparative evidence for this view, in the following figure:

figure illustrating phylogenetic correlation of tunneling and horns in beetles

These suggest that the horn morph in question (triceratops-style) is useful in intraspecific sexual competition in a physically constrained context yielding single opponents (tunnels). This is somewhat similar to familiar examples in large mammals that do "single combat" mating competition. Direct confirmatory tests of this hypothesis were performed in separate work. There is some evidence in related beetles that this is particularly in response to an environmental stimulus of high beetle population density, and thus intensified sexual competition.

Thus, intraspecific sexual competition appears to be responsible for horn emergence in most cases. One classic study looked for ecological correlates of evolution of various horn configurations in a phylogenetic context, though the results seem ambiguous to me due to the quite small number of taxa. Nonetheless, the study highlighted a possible tradeoff between head horn presence and flying, and the presence of horns on the head in some ecological contexts. So, elaborate or large horns specialize the organism for fighting rather than for other activities.

One likely hypothesis is that mating competition is severe enough to drive an evolutionary arms race, leading to horn innovations that might yield advantages. Agent-based modeling approaches support this general theory, but no one seems to have directly tested this hypothesis with real beetles.

$\endgroup$

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .