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Biomedical subjects

O Rieppel

Publications and source records attributed to O Rieppel.

5 recordsLinked to original sources

[Pattern and process: complementarity in biological thinking].

Evolutionary theory is said to explain order in nature by a historical process. An analysis of the writings of E. Geoffroy-Saint-Hilaire shows, however, that pattern and process in nature are not based on simple, i.e. unreflected observation, but rather constitute alternative and incompatible ways of interpretation of observations according to certain methodological rules. It is concluded that pattern and process are complementary views of nature, pattern providing process with a direction, process giving an explanation for pattern.

Animals

A functional interpretation of the varanid dentition (Reptilia, Lacertilia, Varanidae).

A cinéradiographic analysis of the feeding movements in Varanus bengalensis produced the following results. The mouth is opened by raising the head (upper jaw) rather than by lowering the lower jaw. Starting from the resting position, the muzzle unit is elevated around 9 degrees relative to the rest of the skull during jaw opening; the quadrate swings anteriorly around 21 degrees. During jaw closure, the snout is depressed around 15 degrees relative to the rest of the skull, hence 6 degrees beyond the resting position. The quadrate swings backwards around 27 degrees. Amphikinesis is interpreted as allowing a stronger posterior recurvature of the maxillary teeth in Varanus. This increases the holding effect of the teeth without increasing their length, an adaptation of Varanus to capture relatively large prey. The formation of plicidentine (dentine infolding) in the teeth of Varanus increases the surface of attachment of the teeth on the supporting bone. Moreover, the dentine lamellae take up tensile and compressive stresses along their long axes upon axial or vertical loading of the teeth. The slope of pleurodonty is modelled so as to minimalize shear stress on the surface of ankylosis upon axial or vertical loading of the teeth.

Animals

The throat musculature of Sphenodon, with comments on the primitive character states of the throat muscles in lizards.

The throat musculature of Sphenodon is described and figured, and compared with that of lizards. In many features of its throat musculature, Sphenodon may well represent a primitive lepidosaurian pattern, comparable to some extent to the chelonian structure of throat musculature. To infer primitive character states within extant lizards, one cannot simply extrapolate from the condition observed in Sphenodon. In fact, it must be assumed that a rapid change of many features of the throat muscles occurred during the early evolution of lizards in order to provide the basis for further differentiation with extant lacertilian infraorders.

Animals

[The orbitotemporal region in the cranium of Chelydra serpentina Linnaeus (Chelonia) and Lacerta sicula Rafinesque (Lacertilia)].

An analysis of the ontogenesis of the chondrocranium gives the following homologies in the skull of Lacerta and Chelydra: (see article). It is shown that the extracranial position of the cavum epiptericum in Lacerta corresponds to the stage of maximal development of the chondrocranium in Chelydra. But further development brings about a dermal sidewall in the orbitotemporal region, b,ilt up by descending parietal flanges which incorporate the epipterygoid. This not only allows the pila antotica to degenerate but also incorporates the cavum in the cranial cavity.

Anatomy, Comparative