Fossils fragments and heterogeneous type specimens

The Code applies to both living and extinct animals, as is explicitly stated in its Article 1. Thus, the principles of the type method as briefly presented earlier with reference to recent species are equally applicable in paleontology. However, many fossils, particularly complex multistructured organisms, such as vertebrates, inherently lead to practical problems. In most fossil vertebrates, only hard structures are fossilized and thus preserved. In the course of diagenetic processes, soft tissues that connected the hard elements in the living animal are usually decayed so that the resulting skeleton falls apart. In the ideal case, the preserved elements remain in their original position after embedding in a fossilization matrix so that the elements can easily associated with each other. In many cases, subsequent physical processes might have altered the relative position of the elements or have destroyed parts of the organism.

Fossil hominids are never completely preserved, not even with respect to bones. Sometimes just a single preserved bone is sufficient to provide evidence for taxonomic identity. If a single bone is the basis of a new taxon, just the bone is referred to as the holotype. An example is the holotype of Homo heidelbergenis Schoetensack, 1908, which consists of a complete, adult mandible. There is no ambiguity about the formal basis on which the new species is based. If more than a single element is available, association to individual can be difficult if the elements are not in the original position relative to each other but are more or less dislocated or destroyed. An example is the composition of the types of Homo habilis Leakey, Tobias, and Napier, 1964. Several fragments assignable to the new species were available such as mandibles, isolated teeth, parietals and hand bones, and cranial fragments. Due to external evidence, such as the position of the fragments as found during excavation, the fragments could be associated with five individuals. The holotype of H. habilis consists of a mandible with dentition and the associated upper molar, parietals and hand bones, originating from a single juvenile individual.

These examples show another principle of the type method. A type is always a zoological object but is not necessarily something that is or is close to a complete organism. A single tooth, an isolated wing, or any other part of an organism is in principle sufficient to serve as the basis for a new species. In a way incompleteness is an inherent attribute of most preserved specimens because many preservation techniques result in the loss of some characters. Pinned, that is, dried insects and stuffed, mounted vertebrates have usually lost all or most of their soft tissue. Thus, even if a specimen has lost almost the entire physical structure except for a single tooth, this incompleteness of a specimen does not prevent potential type status. It is, however, wise to associate isolated fragments such as a molar and a mandible to a single type specimen only if the evidence is unambiguous. If subsequent evidence is found that the fragments actually belong to different individuals, this might cause a lot of unnecessary nomenclatural confusion.

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