July 29, 1909] 



NATURE 



139 



THE FEEDIXG HABITS OF MCERITHERIUM 

 .LVD PAL.EOilASTODOX. 



T^HROUGH the discoveries in the Oligocene ' of the 

 -^ l-"ayum Mcerithcrium and PaUeomastodon have 

 become famous as two of the earliest, and more or less 

 direct, stages in the ancestry of the elephants. In restora- 

 tions by various authors each of these animals has, been 

 provided with a proboscis of less or greater length, as 

 would befit a more or less remote ancestor of an elephant. 

 As first announced by Dr. C. VV. Andrews, to whom we 

 are chiefly indebted for our present knowledge, Mceri- 

 therium does anticipate the Pala»omastodon type in the 

 enlargement of the second pair of upper and lower incisors 

 and in the general pattern of the grinding teeth. Since 

 the wish is always father to the thought, and nothing is 

 more to be desired than a primitive progenitor of the 

 Proboscidea, it was altogether natural to place Moeri- 

 therium in or near the line of ancestry of the elephant, 

 and in such ancestry, as a member of the Proboscidea, 

 the animal has gone into general literature. 



man under the writer's direction.' Palaiomastodon itself in 

 all probability had not developed a proboscis, although 

 there is no question as to its being in the direct line of 

 proboscidean ancestry. Moerilherium not only had no 

 proboscis, but was totally different from Palasomastodon 

 both in its appearance and habits, and only very remotely 

 related to this animal, if at all. The study shows, further, 

 that Mcerithcrium is closer to the Sirenians and less close 

 to the Proboscidea than has hitherto been supposed. 



A profound difference between those animals is brought 

 out in comparing the top and side views of the skull, 

 when it is seen that, whereas the eyes of Palaeomastodon 

 are in the typical mammalian position above the first 

 permanent grinder, those of Moeritherium are very far 

 forward, well raised in the front part of the head, and 

 of very diminutive size, as shown by the shallowness of 

 the sockets. All these are also characters of the Sirenian 

 head. As indicated by the auditory meatus, the ears are 

 relatively in a more elevated position than in Palseo- 

 mastodon. Both these peculiarities are adaptations to 

 aquatic life to protect the sense organs and bring them 



A first more cautious ^note was sounded by Dr. Andrews I near the surface of the water in swimming, so that they 



in his memoir of iqo6,- p. xvii, in which he observes : — 

 " -As already mentioned, Moeritherium 

 was probably an amphibious, shore, or 

 swamp livin" animal, and it was no 

 doubt owing ro the continuation of the 

 conditions favourable to its mode of 

 life that it persisted into the Upper 

 Eocene period. In the meantime, how- 

 ever, either from this or some closely 

 allied type, there had arisen another 

 animal more adapted to terrestrial life 

 and showing a great advance in the 

 direction of the typical Proboscidea : 

 to this creature the name Palseo- 

 mastodon has been given." Else- 

 where (p. xxi) Dr. .Andrew's notes that 

 Moeritherium favours the view, first put 

 forward by de Blainville, of an original 

 relationship between the Proboscidea 

 and Sirenia. Later on in the same 

 w"ork (p. 119) the same author, in com- 

 menting on the similaritv between the 

 pelvis of Moeritherium and that of the 

 Eocene sirenian Eotherium, observes : — 

 " Then it may fairly be suggested that 

 Moeritherium and Eotherium, both 

 occurring in the same region (one the 

 most primitive Proboscidean, the other 

 occup\ ing the same position with re- 

 gard to the Sirenia), are, in fact, 

 closely related, and had a common 

 ancestor in early Tertiary times, prob- 

 ably in the Lower Eocene." On p. 105 

 we find a comment on the remarkable 

 likeness between the brains of Ma-ritheriu 

 Sirenia. 



Since these suggestive comments were written other 

 materials have been secured, including a nearly perfect 

 skull and jaws of Pal^omastodon by the British Museum 

 and a skull of Pala?omastodon and tw'o partly preserved 

 skulls of Mcerithcrium by the .American Museum. 



The question of habits and of affinity seems so important 

 and interesting that the writer has taken it up afresh with 

 these additional materials. The inquiry was suggested by 

 the general resemblance which the skull of Moeritherium 

 bears to that of a Sirenian as seen from above and in 

 palatal view. The method of comparison adopted is that 

 of making life-size models of the skulls of Mceritherium 

 and Pala'omastodon, then placing the sense organs and 

 the mouth parts in position, guided solely by comparison 

 w'ith existing mammals showing more or less analogous 

 modifications and by the actual condition of the hard 

 parts themselves. This work was done by Mr. E. Christ- 



1 The;e Palaeomasto-lon bed^ were at first regarded as Upper Eocene, 

 but closer compari-on with thnse of Europe has shown that they should be 

 rather considered as Lower Oligocene. 



- " A Descriptive Catalogue of the Tertiary Vertebrata of the Fayum, 

 Egypt." (London, rgof.) 



will emerge first and disappear last. 



Fig. ] 



Side vi2w of the head of Pala;oniastodon modelled by Mr. E. Chrislman under direction of 

 the author. 



and the 



NO. 2074, VOL. 81] 



The cutting teeth and inouth parts of Moeritherium are 

 also opposed in an entirely different manner from those of 

 Palasomastodon, so that it may be said safely that there 

 was not the most remote resemblance either between the 

 mouth parts or the feeding habits of these two animals. 

 In the former the nasal bones do not greatly recede, and 

 there was consequently little or no free retractile power 

 of the upper lip, which is always the rudiinentary con- 

 dition in the evolution of a proboscis, as witnessed in 

 the living tapirs. Comparison with Hyrax, the beaver, 

 and other animals with an enlarged pair of front teeth 

 tends to show that the upper and lower lips were heavy 

 and fleshy, somewhat similar in form and function, that 

 is, in prehensile power, and that the blunt tusks may have 

 been covered when the mouth was closed, somewhat as 

 in the hippopotami. These tusks were feeding rather than 

 fighting weapons, probably because Mceritherium was pro- 

 tected from attack by its aquatic habitat. The conclusion 

 is that Moeritherium was a confirmed and continual river- 

 living animal, feeding mainly under water and on the 

 banks, more specialised for aquatic life than the hippo- 



^ The models have been reproduced and copies pre=enled to the British 

 Museum. The writer is indebted to Mr. W. K. Gregory for many valuable 

 suggestion?. 



