Part 57

Chapter 573,482 wordsPublic domain

Some of these _long-tailed ancestors of the fin-tailed otter_ which in their migration had reached the sea-shore, probably by following the course of rivers, began to accustom themselves to eat sea-fish, and ended by feeding on them exclusively. The sea-water became their home, and their resting places and nests were found on the strand, and among sea-weed; they seldom came ashore to sleep or to sun themselves. Besides on sea-fish, they fed on crabs, lobsters, mussels, and some sea-weed. They left off eating poultry, frogs, and rats. The long tail was of great profit, as they used it as a rudder and as propelling organ in swimming with vertical undulations. Of course those individuals which were the best adapted to this new manner of living, survived the less privileged by nature, and so a group gradually arose which had a sharper dentition, and smaller ears; the skin was also changed to the most valuable fur, the toes of the hind-legs had become more webbed, and with such legs the animals could swim more easily; those of the fore-limbs had sharper nails, and with such nails the animals could more easily crawl upon the rocks; the eyes were larger, and with such eyes the owners could see better in great and dark depths, and in the sea-water near the shore, which is commonly troubled; the whiskers were longer and stronger, consequently the upper-lips, in which these whiskers were planted and which contained numerous and thick sensorial nerves, were very thick, and with such whiskers the animals could exceedingly well touch and feel when searching for their food between stones and sea-weed, and in the sandy bottom. The face resembled but little more that of the otters and fin-tailed otters, and the large eyes and shorter ears gave it a slight resemblance to seals. This group may be called _long-tailed ancestors of sea-otters_, for our sea-otters (_Lutra lutris_ L.) are still living descendants of them. But as these animals have accustomed themselves to live more among sea-weed, ice, and rocks than their direct ancestors, the long tail must have been inconvenient, so that individuals with a shorter tail must have survived the others, and finally a species arose with a tolerably short tail: our sea-otter. To make up for this loss of tail, the hind-feet had become more webbed, and were gradually stretched more backwards, and, modified in this way, they were valuable swimming organs. The change was great enough for zoologists to create a new genus for this animal, which is called _Enhydra_ CUV.

Some of the _long-tailed ancestors of sea-otters_ took to a still more aquatic, or better pelagic life, migrated more towards the north, accustomed themselves to the icy regions, to swim greater distances and to remain longer under water. The consequences of this change in the manner of living were that all little adapted to this new life became extinct, and that all which were better privileged survived them, so that at last a group of animals arose of which we may safely admit that they had the following characters: The head and fore-feet resembled still more those of seals, the hind-legs were still more able swimming organs, and less fit for terrestrial locomotion, they were smaller than the fore-legs, because they were not always used in swimming, as the best manner of swimming must have been by means of vertical undulations; the long tail surpassed half of the total length, and served as a rudder and as propelling organ; the ears were still smaller, the dentition was still a normal carnivorous one (i 3/3, c 1/1, m 7/7), especially the molars were sharp and pointed, and on the skull were found peculiar modifications which are so distinctly visible on that of Pinnipeds. The animals must have resembled our common seals, having, however, small external ears, and a tail, surpassing one half of the total length. It is difficult to believe that these animals, which I will call _Propinnipedia_, moved on land; probably they came from time to time aland or on the ice to rest with the fore-part of the body on it, leaving, however, most certainly the long tail in the water. These _Propinnipedia_ gave origin to two groups of animals, which are marked below with A and B.

A.--This group, by their having lived almost constantly far from land, and having come only very seldom near the shore to rest, supporting themselves on the chest or breast, clinging with the nails of the fore-legs to the beach, rock, or ice, changed in such a way, that zoologists can hardly reckon them any longer among Pinnipeds, but generally consider them as a link between Pinnipeds and Whales. Professor D’ARCY W. THOMPSON (_Studies from the Museum of Zoology in University College_, Dundee, Vol. I, N^o. 9, 1890) rejects any affinity of this group to Whales. I should like to go still farther and pretend that it has just as much claim to the title of Pinnipeds, as seals, sea-elephants, sea-bears, sea-lions, and sea-serpents. The skull was somewhat lengthened in front; the brain-case diminished in size; the deciduous dentition probably cut the gum; the permanent dentition was the typical heterodont carnivorous one (i 3/3, c 1/1, m 7/7); the nostrils were placed on the tip of the nose, as in seals, but directed upwards; the fore-limbs were perfectly those of seals, and provided with nails; but the rest of the body must have _resembled_ that of a slender and elongated dolphin, or whale, with an enormous _pointed_ tail. The most successful manner of swimming for these animals was by means of vertical undulations, which, as the forepart of the body (head and trunk) was somewhat bulky, and therefore somewhat inflexible, were strongest in the tail-part of the animal; consequently the hind-legs, used less and less, disappeared, if not quite, at least for the greater part. The animals were still hairy, though the hairs were most probably thinly scattered; the whiskers remained on the lips. The head was relatively large, not with regard to the animal’s total length, but to the trunk, and therefore the neck was very short. Externally the neck must not have been plainly visible. The animals could not move the head as easily as seals and sea-lions do, and therefore it was of great advantage that the nostrils were directed upwards. The vertebrae have the type of those of the Pinnipeds.--Such animals are now extinct, but their fossil remains are found and called _Basilosaurus_ by HARLAN in 1824 (afterwards OWEN gave them the name of _Zeuglodon_, 1839).

B.--This second group is called _Pinnipedia_ by ILLIGER in 1811, and ALLEN gives of it the following characters:

“Limbs pinniform, or modified into swimming organs, and enclosed to or beyond the elbows and knees within the common integument. Digits of the manus decreasing in length and size from the first to the fifth; of those of the pes, the first and fifth largest and longest, the three middle ones shorter and subequal. Pelvis with the iliac portion very short, and the anterior border much everted; ischia barely meeting by a short symphysis (never anchylosed) and in the female usually widely separated. Skull generally greatly compressed interorbitally; facial portion usually short, rather broad, and the brain-case abruptly expanded. Lachrymal bone imperforate and joined to the maxillary, enclosed wholly within the orbit. Palatines usually separated by a vacuity, often of considerable size, from the frontals. Tympanic bones separated also by a vacuity from the exoccipitals. Dentition simple, generally unspecialized, the molars all similar in structure. Deciduous dentition rudimentary, never truly functional, and generally not persistent beyond the foetal stage of the animal. Permanent incisors usually 6/4 or 4/4, sometimes 4/2 (_Cystophora_ and _Macrorhinus_) or even 2/2 (_Odobaenus_); canines 2/2; molars 5/5, 6/5, or 5/3.”

And we may add: Tail either very long: about as long as one half of the animal’s total length, or very short: almost disappearing between the hind-legs.

Already very early the Pinnipeds divided themselves into two different branches, marked below with I and II.

I.--The members of this branch changed their manner of living. They very often crawled on land, ice, and rocks; the long tail was a very unconvenient organ in their new manner of living, consequently all the individuals with a somewhat shorter tail than their congeners’ were better adapted to the new manner of living and survived them, so that at last a group of animals arose of which the tail has become very short, almost disappearing between the hind-legs, and to make up for this loss the hind-legs grew much larger than the fore-legs, were turned hindwards, gradually grew incapable of being turned forwards, and of no use in terrestrial locomotion. This branch is called _Inauriculata_ by PÉRON in 1816 (afterwards called _Phocidae_ by GRAY in 1825, and _Reptigrada_ by ELLIOT COUES, invited thereto by ALLEN in 1880). The characters are described by ALLEN as follows:

“Hind-legs not capable of being turned forward, and not serviceable for terrestrial locomotion. Neck short. Skull with the mastoid processes swollen, but not salient, and without distinct alisphenoid canals. Anterior limbs smaller than the posterior, the first digit little, if any, longer than the next succeeding ones, all armed with strong claws, which are terminal. Hind feet capable of moderate expansion, short; digits (usually) all armed with strong claws, and without terminal cartilaginous flaps. Femur with no trace of the trochanter minor. Without external ears. Postorbital processes wanting, or very small. Incisors variable (6/4, 4/4, or 4/2). Deciduous dentition not persistent beyond foetal life.”

The group includes all true seals and sea-elephants.

II.--This branch is called _Gressigrada_ by ELLIOT COUES in 1880, who was thereto invited by ALLEN, though this skilled zoologist was then unaware of the existence of the sea-serpent, or at least must have doubted its belonging to this branch. I have not a single reason to give another name to it; I purposely keep the name of _Gressigrada_, to avoid the increase of synonyms. The early forms of the _Gressigrada_ must have had hind-legs which were smaller than the fore-legs, and a tail, which was as long as the head, neck and trunk together. They had also small external ears, and a somewhat lengthened neck. Further characters are: “Hind-legs capable of being turned forward and used in terrestrial locomotion. Neck lengthened (especially in section b). Skull with the mastoid processes large and salient (especially in the males), and with distinct alisphenoid canals. Anterior feet either nearly as large as the posterior, or much larger, their digits rapidly decreasing in length from the first to the fifth, with distinct claws, and with a broad cartilaginous border extending beyond the digits.” (They are called flappers.) “Hind-feet susceptible of great expansion, the three middle digits only with claws, and all the digits terminating in long, narrow, cartilaginous flaps, united basally.” (The hind-feet may also safely be called flappers.) “Femur with the trochanter minor well developed”.--Already at a very early date the branch of the _Gressigrada_ divided itself into two sections, which are marked below with a and b.--

a.--The members of this section changed their manner of living. They very often crawled on ice, land, and rocks; the long tail was a very inconvenient organ in their new manner of living, consequently all the individuals with a somewhat shorter tail than their congeners’ were better equipped, and survived the others, so that at last a group of animals arose of which the tail has become very short, scarcely, if at all, visible, being enclosed within the tegument of the body, and to make up for this loss, the hind-flappers grew much larger than the fore-flappers. The further characters for this group are: “Without external ears. Form thick and heavy. Anterior portion of the skull greatly swollen, giving support to the enormously developed canines, which form long, protruding tusks. Incisors of deciduous (foetal) dentition 6/6; of permanent dentition 2/6. No postorbital processes, and the surface of the mastoid processes continuous with the auditory bullae.”--This section is called _Trichecidae_ by GRAY in 1821 (afterwards it was named _Trichechidae_ by GRAY in 1825, _Broca_ by LATREILLE in 1825, _Campodontia_ by BROOKES in 1828, _Trichecina_ by GRAY in 1837, _Trichechoidea_ by GIEBEL in 1847, _Trichechina_ by GRAY in 1850, _Rosmaridae_ by GILL in 1866, _Rosmaroidea_ by GILL in 1872, and _Odobaenidae_ by ALLEN in 1880!!!). The section contains only the walruses.

b.--The early forms of this section must have had hind-flappers which were smaller than the fore-flappers, and a tail which was as long as the head, neck and trunk together. The animals were very slender and elongated in form, the neck being _somewhat more elongated_; external ears, though small, were still present. Further characters are: “Anterior portion of the skull not unusually swollen, and the canines not highly specialized.” They came very seldom aland, and when doing so, they must have only supported themselves on their breast and on their fore-flappers, leaving the long tail always in the water. They swam with vertical undulations, using also sometimes the flappers.--For this section I choose the name of _Tenuia_, or Animals which are slender.--Very early the section of the _Tenuia_ divided itself into two smaller divisions which are marked below with 1 and 2.--

1.--The members of this division changed their manner of living. They very often crawled on ice, land and rocks; the tail was a very inconvenient organ in their new manner of living, consequently all the individuals with a somewhat shorter tail than their congeners’, were better equipped and survived the others, so that at last a group of animals arose of which the tail has become very short, almost disappearing between the hind-legs which on the contrary to make up for this loss of tail, gradually became larger, so as to become even larger than the anterior feet. The further characters of this group are: “With small external ears. Incisors of deciduous dentition 6/4, only the outer on either side cutting the gum; of permanent dentition 6/4, the two central pairs of the upper with a transverse groove. Postorbital processes strongly developed. Surface of the mastoid processes not continuous with the auditory bullae.”--This division was called _Auriculata_ by PÉRON in 1816, (afterwards also called _Otariina_ by GRAY in 1825, _Otariadae_ by BROOKES in 1828, _Arctocephalina_ by GRAY in 1837, and _Otariidae_ by GILL in 1866) containing the sea-bears and sea-lions.

2.--The members of this division did not accustom themselves to live in the midst of ice and rocks, consequently they retained the long tail, and small hind-legs. As the animals retained also their slenderness and extraordinary litheness, a long neck with a relatively small head must have been of great use to them, and consequently those individuals which had a longer neck than the others survived their less privileged congeners, so that at last a group arose with a very long neck and a comparatively small head. It seems that the external ears disappeared. They never came aland or on ice-floes. They even abandoned the cold regions and currents of the ocean, better liking the warmer parts. Their ordinary mode of swimming is with vertical undulations. Seldom do they swim with the body in a straight line, by means of their flappers. This little division for which I propose the name of _Longicaudata_, or Long-tailed Animals, consists only of one genus: _Megophias_ RAF., including only one species _Megophias megophias_ (RAF.) OUD., the sea-serpent.

I purposely have not mentioned the genera _Squalodon_ and _Stenodon_, and the group of _Plagiuri_ (ART., 1735; _Physeteres_, KLEIN, 1741; _Cetacea_, BRISS, 1756; _Cete_, LINN, 1758), as the recent cetologists still differ in opinions as to their relation to _Basilosaurus_ and the _Pinnipedia_.

I think the following phylogenetic table will in a more practical manner show the rank which in my opinion sea-serpents occupy in the System of Nature.

To many of my readers the above sketch of the rank of the sea-serpent in the System of Nature will no doubt seem to be too bold. They will say that the affinity of the sea-serpent to sea-lions and sea-bears (to the _Auriculata_) is expressed here too decisively, that, scientifically spoken, the sea-serpent is not yet known, that at best its existence is only beyond a doubt, and that when a specimen fell into the hands of men, it might be shown that the close affinity to the _Auriculata_ was only apparent, and that in reality the relation is more remote. I confess that there is much to say in favour of this reasoning, but _at all events the sea-serpent is a true Pinniped_. It has four flappers, a hairy skin, and strong whiskers. Its head _resembles_ that of a sea-lion, its long neck _resembles_ that of a sea-lion, its trunk and its foreflappers _resemble_ those of a sea-lion. But these _resemblances_ may be explained as resulting from convergency. When viewed in this way it seems to be more careful to consider the origin of the sea-serpent in the following manner.

The ancestors of _Pinnipedia_ and _Basilosaurus_, which I have called _Propinnipedia_, had most probably hind-legs which were smaller than the fore-legs, and most certainly a tail which was nearly as long as the head, neck and trunk together. They had small external ears. Their most successful manner of swimming must have been by means of vertical undulations. It is difficult to believe that the _Propinnipedia_ moved on land; probably they came only from time to time aland, or on the ice, to rest, leaving, however, most probably the long tail in the water. These _Propinnipedia_ divided themselves into two branches.

All the members of the _first_ branch got a tendency to bulkiness. The head grew longer and larger, consequently the neck grew shorter; the jaws grew longer, consequently the teeth began to stand widely apart; in consequence of the little mobility of the head the nostrils, placed at the top of the nose, became turned upwards, or probably got their seat a little more towards the top of the head; and in proportion as the animal got a thick layer of bacon, the hairs became thinly scattered. Probably it is here better to say: in proportion as the animal lost its hairs, it got a thick layer of bacon. The warm-blooded mammals are possessed of the hair, because hair was to them what feathers are to a bird. The air enclosed between the hairs and the feathers is a worse conductor of temperature than the hairs or feathers themselves. As soon as the manner of living has changed so much that air could no longer come between the hairs, the hairs themselves lost their reason of existence, hence a thick layer of bacon gradually replaced them. Probably this is a better way to explain the presence of bacon and the absence of hair, than to say that the hair disappeared because the animals obtained a layer of bacon, and could therefore dispense with them, or that the layer of bacon checked the development of hairs.--In short we may admit that the animals, of which we treat at present, were thinly scattered with hairs. The whiskers in all probability were still present, and even well developed. This branch has wholly become extinct. The fossil remains were called _Basilosaurus_.

All the members of the _second_ branch did not show a tendency to bulkiness, they retained the relatively small head and well developed neck, the head consequently could very well move on the trunk. These are the _Pinnipedia_.

Already very early they divided themselves into two sections.

All the members of the _first_ section accustomed themselves to crawl more on land, ice, and rocks, and as the long tail must have been an inconvenient organ in this new manner of living, all the individuals which had a smaller number of caudal vertebrae survived their congeners; consequently a form at last originated with a very short tail our well known order of Pinnipeds for which I now propose the name of _Brevicaudata_.

All the members however, of the second section accustomed themselves more to the sea, and therefore all the members which were best adopted for this manner of living successively survived their less privileged congeners, and finally the sea-serpents remained; animals which are so excellently adapted to an aquatic life and rapid movement, that their tendency to become extinct can only be explained by the singular phenomenon that colossal animals bring forth very few young ones, only two, or only one, at a time, and only after very long intervals. For these animals I already proposed above the name of _Longicaudata_. They form with the _Brevicaudata_ the order of _Pinnipedia_.

If this view is better, (and who will tell us this with any certainty?) the phylogenetic table should be altered as follows: