657:. 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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551:. 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
640:, 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
515:. 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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728:"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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519:. These features, and some formal analyses of their morphology, suggest that they were likely burrowing animals.
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attacked by predators. A similar use of posterodorsal horns has been indicated to decrease predation in
796:"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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60:. Unsourced material may be challenged and removed.
508:and multiple analyses support a role in defense.
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431:, and is the smallest known horned mammal.
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850:. London: Marshall Editions. p. 283.
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120:Learn how and when to remove this message
932:The Paleobiology Database: Ceratogaulus
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477:. They were native to what is now the
500:displays or combat, and defense from
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427:is the only known rodent genus with
58:adding citations to reliable sources
732:Journal of Systematic Palaeontology
680:Journal of Systematic Palaeontology
800:Proceedings of the Royal Society B
600:1931 restoration of two burrowing
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1108:Pliocene mammals of North America
588:or the evolutionary progression.
1103:Miocene mammals of North America
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794:Hopkins, Samantha S.B. (2005).
45:needs additional citations for
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1123:Fossil taxa described in 1902
752:10.1080/14772019.2020.1765889
700:10.1080/14772019.2020.1765889
541:horns in position and shape.
455:Reconstruction of a pair of
523:Possible roles of the horns
361:Hibbard & Phillis, 1945
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415:, a member of the extinct
345:Calede & Samuels, 2020
1083:Miocene first appearances
592:Mating displays or combat
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231:Scientific classification
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846:Palmer, D., ed. (1999).
27:Extinct genus of rodents
572:Ceratogaulus rhinocerus
812:10.1098/rspb.2005.3171
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473:, an extinct genus of
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1055:Paleobiology Database
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223:Ceratogaulus hatcheri
143:Late Miocene–Pliocene
1098:Pliocene extinctions
504:. The horns are not
435:lived from the late
54:improve this article
806:(1573): 1705–1713.
744:2020JSPal..18.1395C
692:2020JSPal..18.1395C
532:The nasal horns of
937:2012-02-04 at the
877:Journal of Anatomy
610:cervical vertebrae
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889:10.1111/joa.13579
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994:Ceratogaulus
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479:Great Plains
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457:C. hatcheri.
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425:Ceratogaulus
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421:Mylagaulidae
412:Ceratogaulus
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405:are extinct
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301:Mylagaulidae
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52:Please help
47:verification
44:
18:Ceratogaulus
1118:Hemphillian
988:Wikispecies
602:C. hatcheri
470:Peltephilus
447:Description
350:C. hatcheri
337:Korth, 2000
1077:Categories
661:References
586:morphology
562:rhinoceros
80:newspapers
897:0021-8782
760:1477-2019
708:219902187
628:, as the
622:ungulates
502:predators
485:, mostly
475:armadillo
465:fossorial
417:fossorial
394:Epigaulus
254:Kingdom:
248:Eukaryota
110:July 2014
973:Wikidata
935:Archived
915:34747041
830:16087426
487:Nebraska
443:epochs.
441:Pliocene
386:Synonyms
358:C. minor
326:Species
294:Family:
288:Rodentia
278:Mammalia
268:Chordata
264:Phylum:
258:Animalia
244:Domain:
1047:3610163
1034:1039470
1021:4828116
1008:4468740
979:Q139065
906:8930836
821:1559849
740:Bibcode
688:Bibcode
644:Defense
564:skull.
528:Digging
513:marmots
437:Miocene
407:rodents
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429:horns
101:JSTOR
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