A Bilateral Division of the Parietal Bone
in a Chimpanzee; with a Special Reference
to the Oblique Sutures in the
Parietal.
By Aleš Hrdlička
AUTHOR'S EDITION, extracted from BULLETIN
OF THE
American Museum of Natural History,
Vol. XIII, Article XXI, pp. 281–295.
New York, Dec. 31, 1900.
The Knickerbocker Press, New York
Article XXI.—A BILATERAL DIVISION OF THE
PARIETAL BONE IN A CHIMPANZEE; WITH
SPECIAL REFERENCE TO THE OBLIQUE SUTURES
IN THE PARIETAL.
By Aleš Hrdlička.
The first to describe a case of division of the parietal bone inapes was Johannes Ranke, in 1899.[1] The skull in question isthat of an adolescent female orang, one of 245 orang crania inthe Selenka collection in the Munich Anthropological Institute.The abnormal suture divides the right parietal into an upperlarger and a lower smaller portion. "The suture runs nearlyparallel with the sagittal suture," but, as the illustration shows(Fig. 1), it descends in its posterior extremity towards the temporo-parietalsuture, and terminates in this a few millimetres infront of the lambdoid suture. The abnormal suture shows butlittle serration, and the articulation of the two divisions of theparietal bone is squamous in character, the lower portion overlappingthe upper. Below the junction of the abnormal with thecoronal suture, the latter takes a pronounced bend forward. Asimilar bend in the coronal suture is present in the same specimenon the left side. This is common among the other orangskulls in the collection. The portions of the coronal suture belowand above the bend differ somewhat in character.
Besides the above-mentioned complete division, Ranke foundamong the 245 orang skulls 13 with incomplete division of theparietal bone. The division consisted invariably of a longer orshorter remnant of a horizontal "parietal suture," ending in thecoronal suture at the top of the bend above referred to. A similaranterior remnant of an abnormal parietal suture was found byRanke in a young chimpanzee skull; but the author questionsthe word "chimpanzee," which evidently means that the identityof the skull is somewhat doubtful.
In consequence of his finds, Ranke believes both completeand incomplete divisions in the parietal bone to be much more [Pg 282]frequent in the orang than in man.[2] He also thinks that thebend usually present in the coronal suture in the orang signifiesthat, "even where there are no traces of a parietal suture, such asuture has actually existed in an earlier stage of development."This implies the development of the adult parietal bone in theorang from two originalsegments, oneabove the other.
Fig. 1. Division of the Right Parietal in an Orang (Ranke, Abh. d. k. bayer. Akad. d. Wiss., II cl., XX Bd., ii Abth.).
The divisions whichI am about to describeoccur, one ineach parietal, in theskull of a nine-year-oldmale chimpanzee,which was captured,when young, in W