Art. XXXVIII.—On the Dimensions of Dinornis Bones.
[Read before the Otago Institute, 12th October, 1874.]
The large number of Moa bones exhumed last summer from the swamp near Hamilton for the committee of the Otago Museum' having passed into my charge, it became necessary for me to try to determine the different species by measurement in order that I might select a complete series to be retained in the museum and ascertain what duplicates there were for exchange. In doing this I made nearly 2,000 measurements, and although I have not a sufficient knowledge of anatomy to be able to give an opinion as to what anatomical characters are sufficient to determine species, yet as the different species of Dinornis have necessarily been distinguished by Professor Owen chiefly by size, I think that the results of my measurements are of sufficient importance to justify my bringing them before you.
No one I think can examine such a large collection of Moa bones as I have done without being struck by the almost exhaustive nature of the researches of Professor Owen, and the collectors who supplied him with the material to work upon. It would naturally be expected that the examination of the remains of some two or three hundred extinct birds would show several forms not hitherto described. Such, however, is not the case, for with but very few exceptions all the bones can be referred with tolerable precision to some name already established, or to an intermediate form between two names. These excavations have certainly brought to light a variety of D. elephantopus, larger and more exaggerated in its characters than any yet recorded by Professor Owen or by Dr. Haast, and they have also proved that, so far as mere size is concerned, two of Professor Owen's species run gradually into one another. But notwithstanding this the difference in the forms he has described is so great that I am of opinion that the whole of his specific names must be retained, while one or two others may perhaps have to be added to them. *
I have already mentioned that the collection contained the remains of more than 200 birds; many of the bones, however, were not sufficiently well preserved to admit of accurate measurements being made. I therefore selected out the fully adult and best preserved bones for measurement, except where the form was represented by very few individuals, in which cases all adult bones were measured.
In the annexed table (Table A) I have arranged the various bones to the best of my judgment, according to the dimensions given by Professor Owen
[Footnote] * In my paper on the Geographical Relations of the New Zealand Fauna—I said that probably some of Professor Owen's species of Dinornis are but the young of others (Trans. N. Z. Inst., 1872, p. 232). This is a mistake, Professor Owen's species are certainly all founded on adult specimens.
(Trans. Zool. Soc., VIII., p. 371), and I have given under each heading the number of bones measured, the maximum and minimum measurements, and the mean of the whole, and it will be seen that I have arranged them under nine different species and two varieties.
Of these the remains of D. robustus and D. ingens were too few to warrant any certain conclusions, but they appear to be distinct species. D. struthioides, which was much more common than the other two, is very distinct and easily recognisëd from any other. I refer five metatarsi to D. rheides, but I was unable to find in the whole collection a single femur small enough to answer to Professor Owen's dimensions.
The bones that I have arranged under the name D. didiformis belong probably to a new species. The tibia is well marked and quite distinct, but the femur and metatarsus that I have associated with it pass almost into D. casuarinus, but are rather smaller.
D. casuarinus is undoubtedly a good species, easily distinguished by its tibia; but I suspect that some of the metatarsi arranged under D. casuarinus, may belong to it. At any rate it is difficult to separate the metatarsi of these two species. The Otago Museum possesses a specimen of D. casuarinus, got at the old Botanical Gardens, Dunedin (see Hector, Proc. Zool. Soc. 1865, p. 749), which is nearly complete except the skull and right metatarsus, and there is no doubt but that all the bones belonged to the same individual. The dimensions of the leg-bones are as follows:—
|Circumference at middle||4·6||4·2||5·4|
In this case the metatarsus and tibia come under the head of D. casuarinus, but the femur would be referred to D. gravis.
D. gravis also appears to me to be a good species, although the tibia approaches very closely to that of D. casuarinus, but is more robust, the length being only about three and a half times the circumference of the middle of the shaft, while in D. casuarius it is more than four times the circumference. * In the swamp at Hamilton the bones were so confusedly mixed together that in the whole collection I have only two leg-bones that I am absolutely certain belonged to the same bird. They belong, I consider, to D. gravis, although larger than those figured by Professor Owen. Their dimensions are as follows:—
[Footnote] * The measurements, however, given by Dr. Haast (Trans. N. Z. Inst., I., p. 86, No. 13) of bones found in situ in the Glenmark swamp, appear to connect D. gravis with D. crassus. For while the metatarsus would belong to the former, the tibia and femur must be referred to the latter.
|Circumference at middle||6·0||5·25|
Between D. crassus and D. elephantopus, however, no strict line of demarcation can be drawn. It will be noticed in Table A that among the femora that of D. crassus is by far the most abundant, while in the tibiæ what I have called D. crassus var. major takes the lead, and among the metatarsi D. elephantopus occupies that position. This would naturally lead us to suspect that these three bones belong to the same species, and fortunately I am in a position to show that something like this is true. The Otago Museum possesses a skeleton of a Moa found in a limestone cave at Doctor's Creek, Waitaki, by Mr. James Stevenson. This skeleton is nearly complete, wanting only the head, a few cervical and caudal vertebræ, and two small phalanges of the outer right toe. The bones were lying in their proper position, the sesamoid bones of the ankle joints being also in their places. No hind toe nor scapulo-coracoid were found, although Mr. Stevenson looked carefully for the former. There is therefore no possible doubt but that all these bones belong to the same indvidual. The measurements of the leg-bones are as follows:—
|Circumference at middle||6·0||5·6||6·83|
It will be observed that in this case the femur should be referred to D. crassus, and the tibia and metatarsus to D. crassus var. major of Table A. The metatarsus, however, approaches more nearly to the dimensions assigned by Professor Owen to D. elephantopus than to those of D. crassus, and it is under the former name that I feel inclined to class it, as the length of the metatarsus is not quite four times the breadth of the middle of the shaft.
The divisions that I have here drawn between D. crassus var. major and D. elephantopus on the one hand, andD. crassus var. major and D. crassus on the other are, of course, quite arbitrary, and depend in the case of the femur and tibia on the circumference of the middle of the shaft, and in the case of the metatarsus on the breadth of the middle of the shaft. The divisions could have been drawn equally well in other places as the gradations are very minute and regular. I have been quite unable so far to distinguish the “clearly defined” sub-species, and even sexes of sub-species, mentioned by Dr. Haast (Trans. N. Z. Inst., VI., p. 429), and shall look forward with interest
to the publication of the measurements on which these sub-species and sexes have been founded.
In order that others may be able to form an idea of the nature and complicated character of the variations in these bones I have added a table (Table B) showing the dimensions of all the bones of D. casuarinus from the Hamilton Swamp that I measured. I have selected D. casuarinus because we know that the metatarsi and tibiæ belong to the same species, although the femora may be incorrectly associated with them. If I had taken D. crassus or D. elephantopus as an illustration the gradations would have appeared more minute and far more intricate, as my material is so much greater.
Among the metatarsi of D. crassus and D. elephantopus there are certainly two very different forms, in one of which the trochleæ are widely diverging, and in the other more longitudinal; and I tried to arrange them in two series according to the relative breadths of the distal extremity and the middle of the shaft, but the result was only to convince me more than ever of the extraordinary variation in these species of Dinornis, and I abandoned the attempt, as by adhering to it I should have had to depart so widely from the dimensions given by Professor Owen that my principal object in compiling Table A, viz., to show that the species D. crassus and D. elephantopus, as at present characterized, cannot be maintained–would have been lost. I also attempted to separate the tibiæ by their greater or less curvature, but this also led to the same results–a gradual passage from one to the other. Indeed the variation is so great that with over a hundred metatarsi of D. crassus and D. elephantopus lying before me, I have had very great difficulty in selecting a right and left sufficiently alike to make a presentable match.
Still, notwithstanding all that I have said, I am convinced that it will be necessary to retain the names both of crassus and elephantopus to mark both ends of the series as characterized by the proportions of the metatarsus, the length of which in D. crassus is more than four times the breadth of the middle of the shaft, while the length is less than four times the breadth in D. elephantopus and D. gravis. But I think that we must wait patiently for more information before we assign tibiæ and femora to them.
It may be that when these bones from Hamilton are studied by a competent anatomist he may be able to point out constant marked anatomical characters which would enable him to refer them with certainty to Professor Owen's species, and if such should be the case no one would be more pleased than I, for I think no one has been more puzzled with them; but I confess to having great doubts about it, especially as the very highest authority– Professor Owen himself–has said that he is ready and willing to yield up any of his species should intermediate sizes of femur, tibia, and metatarsus, without distinct and well-marked modifications of form or proportions be found (Trans. Zool. Soc., VIII., p. 361).
|—||Dimensions of the Metatarsus|
|Circum. at middle||5·0||4·8||4·75||4·75||3·9||5·45||5·2||5·0||4·4||4·0||5·0||4·75||4·9||4·9||4·0||5·0||4·25||4·25||3·9||3·85||3·95|
|Dimensions of the Tibia.||Dimensions of the Femur.|
|Circum. at middle||4·9||4·5||4·5||4·65||4·65||4·6||4·25||4·2||4·5||4·35||4·75||4·7||4·5||5·25||4·9||5·0||4·75||4·9||4·75||4·6|
|D. robustus||D.ingens,||D. struhioides,||D. rheides.||D. didfornis?.||D. casisarinus,||D. crassis,||D. crassus, var. major.||D. elephasiopus,||D. elephantopus, var. major.||D. gravis,|
|3 specimens.||8 specimens.||10 specimens||2 specimens.||7 specimens.||41 specimens||9 specimens||13 specimens.||8 specimens.||17 specimens.|
|Circumference at middle||8·0||7·5||7·7||7·25||6·7||6·9||5·75||5·6||5·65||4·8||4·7||4·75||5·25||4·6||4·9||7·0||6·2||6·6||7·3||7·1||7·2||8·0||7·5||7·5||8·6||8·4||8·5||6·0||5·6||5·9|
|2 specimens.||2 specimens||9 specimens||1 specimen.||7 specimens.||13 specimens.||8 specimens.||43 specimens.||17 specimens.||3 specimens.||12 specimens.|
|Circumference at middle||6·65||6·65||6·65||5·9||5·7||5·8||4·9||4·45||4·6||4·2||4·1||3·6||3·85||4·9||4·2||4·54||5·0||4·5||4·7||5·9||5·0||5·5||6·5||6·0||6·2||6·8||6·7||6·7||5·4||4·5||4·8|
|2 specimens.||6 specimens.||18 specimens.||5 specimens||6 specimens.||21 specimens.||16 specimens||28 specimens.||48 specimens.||6 specimens.||13 specimens|
|Circumference at middle||6·25||6·2||6·2||5·9||5·45||5·6||5·1||4·0||4·6||5·0||4·8||4·9||4·0||3·75||3·9||5·45||4·0||4·6||5·5||4·5||4·8||6·55||5·25||5·8||7·4||6·1||6·5||7·5||7·25||7·4||6·2||4·25||5·9|
|Thickness at middle||1·5||1·5||1·5||1·5||1·3||1·42||1·25||1·0||1·15||1·2||0·95||1·12||1·0||0·78||0·8||1·12||0·8||0·9||1·2||0·9||1·0||1·5||1·1||1·2||1·4||1·6||1·3||1·4||1·25||1·0||1·1|