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The zoology of the voyage of H.M.S. Beagle [vol. 1 of 5] cover

The zoology of the voyage of H.M.S. Beagle [vol. 1 of 5]

Chapter 16: NOTICE OF THE REMAINS OF A SPECIES OF EQUUS,
By Richard Owen
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About This Book

The work offers a geological introduction followed by systematic, anatomical descriptions of fossil mammals collected on the voyage, with emphasis on South American extinct forms. It details crania, jaws, teeth, vertebrae, limb bones, and tesselated armour for taxa such as Toxodon, Macrauchenia, Glossotherium, Mylodon, Scelidotherium, Megalonyx, and Megatherium, illustrated by numerous plates. Comparative morphology and measurements underpin taxonomic identifications and interpretations of structural relationships, and a brief discussion addresses the geological contemporaneity of the described extinct mammals.

NOTICE OF THE REMAINS OF A SPECIES OF
EQUUS,

Found associated with the extinct Edentals and Toxodon at Punta Alta, in Bahia Blanca, and with the Mastodon and Toxodon at Santa Fé, in Entre Rios.

The first of these remains is a superior molar tooth of the right side; it was embedded in the quartz shingle, formed of pebbles strongly cemented together with calcareous matter, which adhered as closely to the tooth in question, as the corresponding matrix did to the associated fossil remains. The tooth was as completely fossilized as the remains of the Mylodon, Megatherium, and Scelidothere; and was so far decomposed, that in the attempt to detach the adherent matrix, it became partially resolved into its component curved lamellæ. Every point of comparison that could be established proved it to differ from the tooth of the common Equus Caballus only in a slight inferiority of size.

The second evidence of the co-existence of the horse with the extinct Mammals of the tertiary epoch of South America reposes on a more perfect tooth, likewise of the upper jaw, from the red argillaceous earth of the Pampas at Bajada de Santa Fé, in the Province of Entre Rios.[66]

This tooth is figured at Pl. XXXII. fig. 13 and 14, from which the anatomist can judge of its close correspondence with a middle molar of the left side of the upper jaw.

This tooth agreed so closely in colour and condition with the remains of the Mastodon and Toxodon, from the same locality, that I have no doubt respecting the contemporaneous existence of the individual horse, of which it once formed part.

This evidence of the former existence of a genus, which, as regards South America, had become extinct, and has a second time been introduced into that Continent, is not one of the least interesting fruits of Mr. Darwin’s palæontological discoveries.