On Acanthopolis platypus (Seeley), a Pachypod from the Cambridge Upper Greensand / by Harry G. Seeley.

  • Seeley, H. G. (Harry Govier), 1839-1909.
Date:
1871
Catalogue details

Licence: Public Domain Mark

Credit: On Acanthopolis platypus (Seeley), a Pachypod from the Cambridge Upper Greensand / by Harry G. Seeley. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    The form of the hones, considered by itself and in relation to the other known fossil types, as well as the osteology of recent crocodiles and lizards, would have led me to suspect the metapodium to consist of the metacarpal bones ; yet the enor- mous size of the foot-bones and small size of the caudal verte- bras, and the fact, demonstrated by all other fossils, that the fore foot is smaller than the hind foot, make it probable that the inferences from comparison have in this case no import- ance, and that the bones are metatarsal. From the shape of the bones I should infer that the distal ends of the metatarsals did not approximate towards each other closely, and that the three inner bones and two outer bones were fasciculated. Another difficulty in the restoration of the foot will occur to the student of Prof. Owen’s writings, from the way in which the foot of Iguanodon is interpreted in the Palasontographical Monograph for 1857 (Wealden Kept. pt. 4). Here the Professor explains the rudimentary metapodial bone as the first or inner- most toe. This interpretation is so much opposed to the ana- logy of recent crocodiles and lizards and fossil Pachypods, that I venture to suggest that the digit which Prof. Owen has named the fourth is really the first, and. that which is named innermost is really outermost; and consequently the bones, instead of be- longing to the right foot, would belong to the left. And to ac- count for this inversion we must believe that, in extracting the fossil or by some subsequent accident, the phalanges of the first and third digits came to occupy each other’s places, which would be more credible than the interpretation which makes the first Hinosaurian metatarsal a mere rudiment. Moreover the proximal angles of the bones overlap each other, as in the recent Reptilia ; only, if Prof. Owen’s interpretation were ac- cepted, they would overlap in a reverse direction to that seen in Reptiles or Pachypods, the angles being directed inwa,rd, according to the figure. This alone seems to me sufficient evidence of the en'or; and so I would suggest to all possessors of casts of Mr. Beckles’s fossil to retranspose the phalanges of the first and third digits, the present arrangement being as much in defiance of osteological experience as any angel or mermaid. It may not be out of place if I remark that no corroborative evidence has yet been published that the fossil foot referred by Prof. Owen to Iguanodon really belongs to that genus. The passage “ Not far from where the foot-bones were found, the femur, tibia, and fibula of the same Iguanodon were extracted—a circumstance which adds to the probability of their belonging to the same limb ” is obviously meant to beg the question of the detennination, and is not put in as proof. Prof. OAven also speculates that if the claAV of the