646:. As the horns grow taller through evolutionary time, they also become more posteriorly positioned and the height of the occipital plate increases, increasing the leverage for lifting them. By positioning the horns more posteriorly, the output lever is shortened and, because the muscles used to rotate the skull dorsally attach at the top of the occipital plate, the input lever is lengthened. Thus, the dorsal strike with the horns would be more powerful as the ratio of output lever to input lever would be increased. Predation is the dominant cause of mortality in most small mammals, so the benefits provided by a mechanism to reduce predation could offset the substantial evolutionary cost of horns in a fossorial mammal.
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540:. As a result of their posterior position, using the horns to dig would bring the anterior tip of the nasals against the substrate after a very short sweep of the horns, making digging with the horns extremely inefficient. This motion would be even more inefficient than suggested because the anterior surface of a
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are inconsistent with use as a digging tool. In recent mammals that use their heads for excavating, the tips of their snouts are used like a spade to scrape at the substrate. Therefore, the only modification of the nasal bones is a slight thickening of the anterior tips. Although it is theoretically
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The shape of the horn itself is also very poor for a digging tool. The horns are thick and broad with large, flat anterior and posterior surfaces. Dragging such a broad tool through the soil would create immense resistance, proportional to the large surface area presented to the substrate. Finally,
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are well suited to defense. The horns are broad and robust, and their dorsal orientation and relatively posterior position makes them well suited to protecting the vulnerable eyes and neck. By elevating the head dorsally, the horns would be snapped backward, protecting the areas most commonly
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Many of the objections that apply to the horns as a digging implement also apply to the use of the horns in sexual combat. Their orientation and position and the morphology of the rest of the skull make it exceedingly difficult to bring them to bear on an opponent of similar size. The
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The horned gopher had two horns; these were large (in comparison to body size), paired, and originated from the nasal bones. Horned gophers are the smallest known horned mammals and the only known rodents ever to have had horns. They are also one of only two known horned
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horn becomes more posteriorly positioned through time, so that the evolutionary trend is towards a horn which becomes more poorly suited to digging through time, rather than better suited. Thus, the argument that the horns functioned in digging is not supported by the
629:, which itself has very poor vision. The small size of the optic foramen indicates extremely poor visual acuity, meaning the females would be unlikely to be able to visually recognize a winner in any sexual displays or sexual combat by the males.
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is concave, making it essentially impossible to use the horns without the anterior end of the snout interfering. The expectation is that an animal using its horns anteriorly (rather than dorsally) would have the
504:. They were approximately 30 centimetres (0.98 ft) long, and had paddle-like forepaws with powerful claws adapted for digging. They also had small eyes, and probably had poor eyesight, similar to that of a
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Horns are used in defense against predators by almost all horned mammals. Animals will use any weapons at their disposal to fight off predators, and the horns of
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with horns ill-suited to sexual combat still use them for combat or for sexual display. However, a sexually selected use of the horns is unlikely in
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positioned vertically or tilted posteriorly. In this configuration, the effective input lever is maximized when the head is lowered, as in the
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from ancestral, head-digging mylagaulids), decreasing the flexibility and range of motion of the neck and making it even more difficult for
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is subject to much speculation. Several functions have been hypothesized (see below for a more detailed analysis) including digging,
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717:"A new species of Ceratogaulus from Nebraska and the evolution of nasal horns in Mylagaulidae (Mammalia, Rodentia, Aplodontioidea)"
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horns are positioned on the posterior ends of the nasal bones and extend dorsally, perpendicular to the plane of the
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508:. These features, and some formal analyses of their morphology, suggest that they were likely burrowing animals.
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862:"Ecological correlates of the morphology of the auditory bulla in rodents: Application to the fossil record"
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attacked by predators. A similar use of posterodorsal horns has been indicated to decrease predation in
785:"The evolution of fossoriality and the adaptive role of horns in the Mylagaulidae (Mammalia: Rodentia)"
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from
Nebraska and the evolution of nasal horns in Mylagaulidae (Mammalia, Rodentia, Aplodontioidea)".
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possible that some mammal might develop horns as a digging tool, digging horns would differ from the
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are shortened anteroposteriorly in all mylagaulids (a feature inherited by
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The
Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals
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is very small, roughly one-half to two-thirds the size of that of the
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Calede, Jonathan J. M.; Samuels, Joshua X. (2020). "A new species of
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Scarpitti, Erica A.; Calede, Jonathan J. M. (April 2022).
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Calede, Jonathan J. M.; Samuels, Joshua X. (2020-09-01).
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In other respects, the animals most resembled modern
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skeleton, Museum of
Natural History, Washington D.C.
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49:. Unsourced material may be challenged and removed.
497:and multiple analyses support a role in defense.
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420:, and is the smallest known horned mammal.
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839:. London: Marshall Editions. p. 283.
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609:species to wrestle with their horns. Many
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109:Learn how and when to remove this message
921:The Paleobiology Database: Ceratogaulus
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466:. They were native to what is now the
489:displays or combat, and defense from
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416:is the only known rodent genus with
47:adding citations to reliable sources
721:Journal of Systematic Palaeontology
669:Journal of Systematic Palaeontology
789:Proceedings of the Royal Society B
589:1931 restoration of two burrowing
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1097:Pliocene mammals of North America
577:or the evolutionary progression.
1092:Miocene mammals of North America
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783:Hopkins, Samantha S.B. (2005).
34:needs additional citations for
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1112:Fossil taxa described in 1902
741:10.1080/14772019.2020.1765889
689:10.1080/14772019.2020.1765889
530:horns in position and shape.
444:Reconstruction of a pair of
512:Possible roles of the horns
350:Hibbard & Phillis, 1945
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404:, a member of the extinct
334:Calede & Samuels, 2020
1072:Miocene first appearances
581:Mating displays or combat
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220:Scientific classification
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835:Palmer, D., ed. (1999).
16:Extinct genus of rodents
561:Ceratogaulus rhinocerus
801:10.1098/rspb.2005.3171
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462:, an extinct genus of
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1044:Paleobiology Database
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212:Ceratogaulus hatcheri
132:Late Miocene–Pliocene
1087:Pliocene extinctions
493:. The horns are not
424:lived from the late
43:improve this article
795:(1573): 1705–1713.
733:2020JSPal..18.1395C
681:2020JSPal..18.1395C
521:The nasal horns of
926:2012-02-04 at the
866:Journal of Anatomy
599:cervical vertebrae
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1031:Open Tree of Life
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878:10.1111/joa.13579
727:(17): 1395–1414.
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32:This article
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983:Ceratogaulus
953:Ceratogaulus
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468:Great Plains
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446:C. hatcheri.
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422:Ceratogaulus
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414:Ceratogaulus
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410:Mylagaulidae
401:Ceratogaulus
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394:are extinct
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342:Gidley, 1907
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323:C. anecdotus
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304:Ceratogaulus
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41:Please help
36:verification
33:
1107:Hemphillian
977:Wikispecies
591:C. hatcheri
459:Peltephilus
436:Description
339:C. hatcheri
326:Korth, 2000
1066:Categories
650:References
575:morphology
551:rhinoceros
69:newspapers
886:0021-8782
749:1477-2019
697:219902187
617:, as the
611:ungulates
491:predators
474:, mostly
464:armadillo
454:fossorial
406:fossorial
383:Epigaulus
243:Kingdom:
237:Eukaryota
99:July 2014
962:Wikidata
924:Archived
904:34747041
819:16087426
476:Nebraska
432:epochs.
430:Pliocene
375:Synonyms
347:C. minor
315:Species
283:Family:
277:Rodentia
267:Mammalia
257:Chordata
253:Phylum:
247:Animalia
233:Domain:
1036:3610163
1023:1039470
1010:4828116
997:4468740
968:Q139065
895:8930836
810:1559849
729:Bibcode
677:Bibcode
633:Defense
553:skull.
517:Digging
502:marmots
426:Miocene
396:rodents
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263:Class:
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538:palate
487:mating
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418:horns
90:JSTOR
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841:ISBN
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568:the
506:mole
137:PreꞒ
62:news
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