Indohyus(Meaning "India's pig" from the Greek wordsIndos,"from India" andhûs,"pig" ) is an extinctgenusofdigitigradeeven-toed ungulatesknown fromEocenefossilsin Asia. This smallchevrotain-like animal found in theHimalayasis one of the earliest known non-cetaceanancestors ofwhales.[1]
| Indohyus Temporal range:Ypresian,
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| Life restoration ofIndohyus major | |
Scientific classification
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Artiodactyla |
| Family: | †Raoellidae |
| Genus: | †Indohyus Rao, 1971 |
| Species | |
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Discovery
editThe fossils were discovered among rocks that had been collected in 1971 inKashmirby the Indian geologist A. Ranga Rao who found a few teeth and parts of a jawbone;[2]when he died, however, many rocks had yet to be broken open. Ranga Rao's widow gave the rocks toHans Thewissen,who was working on them. When his technician accidentally broke one of the skulls they had found, Thewissen recognised the ear structure of theauditory bulla,formed from theectotympanicbone in a shape which is highly distinctive, found only in the skulls of cetaceans both living and extinct, includingPakicetus.[3]
Paleobiology
editAbout the size of araccoonor domesticcat,thisomnivorouspig-like creature shared some of the traits of whales, and showed signs of adaptations to aquatic life. Their bones were similar to the bones of modern creatures such as thehippopotamus,and helped reduce buoyancy so that they could stay underwater.[4]This suggests a survival strategy similar to that of the Africanmousedeerorwater chevrotainwhich, when threatened by a bird of prey, dives into water and hides beneath the surface for up to four minutes.[3][5]
Fromisotopesand the structure of the bones in the fossilsIndohyushad heavy bones. Heavy bones help reduce the buoyancy of living aquatic mammals so that they do not float up to the surface of the water.[6]
Classification
editRaoellidsmay be the "missing link"sister group to whales (Cetacea).[7]All otherArtiodactylaare "cousins" of these two groups.Oxygen-18values andosteoscleroticbones indicate that theraccoon-like orchevrotain-likeIndohyuswas habitually aquatic, but13Cvalues suggest that it rarely fed in the water. The authors suggest this documents an intermediate step in the transition back to water completed by the whales, and suggests a new understanding of theevolution of cetaceans.[8][9]
References
edit- ^Bajpai, S;Thewissen, JG;and Sahni, A (November 2009)."The origin and early evolution of whales: macroevolution documented on the Indian subcontinent".J Biosci.34(5): 673–86.doi:10.1007/s12038-009-0060-0.OCLC565869881.PMID20009264.S2CID28232300.Archived fromthe originalon 2017-05-04.
- ^Ranga, A. Rao (1971). "New mammals from Murree (Kalakot Zone) of the Himalayan foot hills near Kalakot, Jammu and Kashmir state, India".Journal of the Geological Society of India.12(2): 124–134.
- ^abSample, Ian (19 December 2007)."How Bambi evolved into Moby-Dick".The Guardian.Retrieved12 July2024.
- ^Zimmer, Carl(December 19, 2007)."Whales: From So Humble A Beginning..."The Loom,ScienceBlogs.Archived fromthe originalon February 14, 2012.
- ^Myers, PZ(19 December 2007)."Indohyus".Pharyngula.ScienceBlogs.Archived fromthe originalon 20 December 2007.
- ^Zimmer, Carl(2007-12-19)."Whales: From So Humble A Beginning..."National Geographic.Archived fromthe originalon December 2, 2018.RetrievedDecember 1,2018.
- ^Thewissen, J. G. M.;Cooper, Lisa Noelle; Clementz, Mark T.; Bajpai, Sunil & Tiwari, B. N. (2007)."Whales originated from aquatic artiodactyls in the Eocene epoch of India"(PDF).Nature.450(7173): 1190–4.Bibcode:2007Natur.450.1190T.doi:10.1038/nature06343.PMID18097400.S2CID4416444.Archived fromthe original(PDF)on 2016-03-04.
- ^Holmes, Bob."A life spent chasing down how whales evolved".New Scientist.RetrievedDecember 2,2018.
- ^Marx, Felix; Lambert, Oliver; Uhen, Mark (2016).Cetacean Paleobiology (TOPA Topics in Paleobiology)(1st ed.). Wiley-Blackwell.ISBN978-1118561270.
