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The Pelvis of the Testudinata, with Notes on the Evolution of the Pelvis in General

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The Pelvis of the Testudinata, with Notes on the Evolution of the Pelvis in General THE PELVIS OF THE TESTUDINATA, WITH NOTES ON THE EVOLUTION OF THE PELVIS IN GENERAL. G. BAUR. THATSphenodon is the most generalized living reptile there cannot be any doubt today. Let us take the pelvis of Spheno- don as a type of reptilian pelvis, and see in what relations the pelvis of the Testudinata and other vertebrates stands. The pelvis of Sphenodon consists of three ossified elements on each side, the ilium, pubis, and ischium, which all meet in the acetab- ulum. The ilium is a simple bone ; pubis and ischium are more complicated, each one consisting of two branches. These con- ditions are best seen in the figure. The inner branch of the pubis may be called entopubis; the outer branch, ectopubis (pec- tineal process aut.); the inner branch of the ischium, ento- ischium ;the outer, ectoischium (metischial process or tuberosity of the ischium, Huxleyl). E FIG.I. - Sphenodon punctatum, Gray. E, Epigastroid. M, Mewgastroid. H, Hypogastroid. P, Pubis. I, Ischium. Foramen pubo-ischiadicum. o, Foramen obturatorium. The entopubes do not touch each other, nor do the ento- ischia ; the entopubes are also separated from the entoischia. This separation is produced by a continuous rod of cartilage placed in the middle line. This cartilage may be called the gastrad cartilage, gastraze, or gastroid The part in front of the entopubis I call epigastroid (epipubis, part) ; the middle portion, 1 Huxley, Professor: On tlre Characters of tk Pehis in & Mammalia, and tlre ConcCusions respecting the Origin of Illanrnzals which may be based on tkm. Proc. Roy. SOC.,No. 194, 1879, p. 405. 345 346 6AUR. [VOL. IV. mesogastvoia’; the portion behind the entoischia, the hypogas- hid (hypoischium, 0s cloacz). For the correct understanding of the pelvis of vertebrates it is necessary to introduce these terms. The foramina on each side between pelvis and ischium are called foramina pubo-ischiadica ; the small foramen in the pubis, obturator foramen.’ It is very easy to derive all conditions seen in the pelvis of the Testudinata from the condition of Sphenodon just de- scribed. We start from the Chelydroids as a general type. In the young Macrochelys and Chelydra we have the gastral cartilage complete and well developed. The epigastroid forms a very FIG.2. -Macrochelys Temnrinrkit (Troost. MSS.). E, Epigastroid. M, Mesogastroid. H, Hypogastroid. For. pubo-isch. IT, Entopubis. 6, Ectopubis. c, Entoischium. (I, Ectoischium. massive, long, anterior process ; the hypogastkoid is very slen- der, ending in a point behind. In old specimens the entopubes touch each other in the middle line, separating epigastroid and mesogastroid ; the entoischia also meet, separating mesogastroid and hypogastroid. Ossification may take place from different centres in the epigastroid, mesogastroid, and hypogastroid. En- topubes and entoischia never meet, but are always separated by the mesogastroid. From the Chelydridae we reach the conditions seen in the Cinosternidae through the Dermatemydidae and Staurotypidae.2 1 The obturator foramen may be placed completely in the pubis, or on the border of the pubis, or in the pubo-ischiadic foramen. 2 I am now able - thanks to Professor Riitimeyer - to give additional characters for the Chelydridz, Dermatemydidz, Staurotypidz, based on the shoulder girdle, the pelvis, and the conditions of the ninth and tenth dorsal vertebra. Chelydrida No anterior process on entoscapula near acetabulum ; no posterior process on coracoid near acetabulum; mesogastroid well developed, separating com- pletely entopubes and entoischia; no anterior process on ilium; rib-head of eighth NO. 3.1 PEL VZS OF THE TESTUDZNATA. 347 In the two families mentioned we have about the same arrange- ment as in the Chelydridae. In adult Cinosternidze we find the three gastroids ossified, but very small ; the epigastroid never FIG.3. -Dermatenrys Mawii, Gray. Pelvis from below, from a sketch of Professor Riitimeyer. X,peculiar ossified pro- cess, developed from the gastroid portion between the entoischia, also present in old specimens of Chelydridze and Staurotypidre. reaches the extension seen in the Chelydridae and Stauroty- pidae ; entopubes and entoischia nearly touch each other, being only separated by the small, diamond-shaped mesogastroid. It may be that in very old specimens the mesogastroid becomes absorbed by entopubes and entoischia. pleurale well developed; an entoplastron; generally no rib on tenth dorsal; number of peripherals, I I. Dermatentydida. An anterior process on entoscapula near acetabulum; a pos- terior process on coracoid near acetabulum; mesogastroid well developed, separating completely entopubes and entoischia; no anterior process on ilium; rib-head of eighth pleurale present; a rib on tenth dorsal which is free from the eighth pleurde; num- ber of peripherals, I I ; an entoplastron. Staurolypide (Claudius, Staurotypus). An anterior process on entoscapula near acetabulum; a posterior process on coracoid near acetabulum; mesogastroid well de- veloped, separating completely entopubes and entoischia; an anterior process on ilium; rib-head on eighth pleurale absent; no rib on tenth dorsal; number of peri- pherals, 10; an entoplastron. Cinostcrnide. Like Staurotypidq but mesogastroid reduced, not separating ento- pubes and entoischia; no entoplastron. 348 BA UR. [VOL. IV. In another direction, possibly from the Platysternida, devel- oped the form of pelvis seen in the Emydidae and Testudinidae. Among the more generalized forms of Emydida, like MaZaco- FIG.4. - Cinosternum pennyhatticum, var. E, Epigastroid. H, Hypogastroid. clemmys, we find that entopubes and entoischia just begin to touch each other. In the young animals there is a continuous gastroid cartilage, only in older animals entopubes meet, and so do the entoischia. In this stage we find a cartilaginous epigas- troid, mesogastroid, and hypogastroid. The same condition I have observed in Chrysemyspicta. In the next stage entopubes and entoischia unite, but the cartilaginous mesogastroid is still present (Trachemys, Pseudemys, Terrapene, Clemmys, Gece- myda). In Emys the mesogastroid becomes ossified, and forms a slender element, pointed behind, and placed on the ventral side on the anterior portion of the united entoischia. Cyclemys is very near this stage. The epigastroid is always present in E FIG.5. -MaZacocZemmys gtographica, Les. E, Epigastroid. M, Mesogastroid. H, Hypogastroid. middle-aged specimens. It may calcify or ossify, or may become absorbed by the entopubes. The hypogastroid I never found ossified ; it is either cartilaginous, but very small, or absorbed No. 3.1 PELVIS OF THE TESTUDINATA. 349 by the entoischia. In the Testudinidae, or true land tortoises, I have never seen an ossified gastroid. The whole gastroid cartilage may become absorbed by the pubes and ischia in adult animals, and it may happen that all elements co-ossify. This I have also seen in a very old specimen of CZemmys guttata. E In half-grown Testudinidae the gastroid cartilage is complete, but entopubes and entoischia are already united. FIG.6. FIG.7. - Trachenayselegans,Wied. Testdo eurapcea, L. E, Epigastroid. E, Epigastroid. M, Mesogastroid. H, Hypogastroid. H, Hypogastroid. The pelvis of Platysternum, the only representative of the Platysternidz, seems to be of the pattern of the Chelydridz. I have no specimen at hand. Boulenger says: “The pelvis is intermediate between that of typical Emydoids, in which the pelvis and ischium are in contact on the median line, limiting two obturator foramens, and that of Chelydra, in which the two bones diverge, and are connected by ligament. In Platysternum the symphyseal branches of the pubis and ischium are parallel, but yet connected only by ligament. I must remark here that the former type of pelvis, i.e. with two obturator foramens separated by the union on the median line of the symphysial branches of the pubis and ischium, occurs in all Testudinidae (land and fresh-water) which I have examined, with the single exception of Dermatemys, which belongs in this respect to the Chelydroid type; also in the Cinosternidze, but not in the Staurotypidae, which belong to the latter type.” 1 Boulenger, G. A. : Notes on the Ostrology of the Genus Platysternum. Ann. Mag. Nat. Hist., June, 1S87, pp, 461-463, Pls. XVI, XVII. 350 BAUR. [VOL. IV. From what I have said above, some of these statements have to be modified. I believe also that what is called ligament by Boulenger is really cartilage, and we would have, therefore, in Platysternum, a cartilaginous mesogastroid separating ento- pubes and entoischia. Boulenger does not mention the epigas- troid and hypogastroid, but I conclude that these elements are also present. The condition of the pelvis seen in the Pinnata can also be derived from that in the ChelydridE. In the living Cheloniida ectopubes are far separated from the ectoischia, but are con- nected by the mesogastroid cartilage, which perhaps in very old specimens may become ligamentous. The epigastroid is pres- ent, rounded in front, and may become calcified or ossified in old specimens ; the hypoischium is reduced entirely. Even in L FIG.8. - Chelonia myrias, L. E, Epigastroid. M,Mesogastroid. H, Hypogastroid. pretty large specimens (length of bony coracoid 255 mm.) the gastroid cartilage is still continuous. Between the entopubes it is visible from above, between the entoischia from below, be- ing always placed on the sharp angle in which these elements meet. In some fossil Cheloniida, like Allopleuron, entopubes and entoischia are nearer together. This leads to the condition seen in the Dermochelyidz, in which entopubes and entoischia seem to meet each other. I could not examine a fresh speci- men of Dermochelys, and have to rely on Wagler’s and Hoff- mann’s2 figures, Gervais’ a not being at hand. According to these figures the entopubes seem to touch the entoischia, but there is some uncertainty about it. In Hoffmann’s figure the left entopubis reaches the ischiurn, but the right one does not. Wagler, Joh.: NatiirZickes System der Amphcibien, 1830, PIS. I, Figs. 21, 22. Hoffmann, C : Reptiliierr, in Bronn’s Klassen und Ordnungen, Taf.
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