DISCOVERY OF THE TITANOTHERES AND ORIGINAL DESCRIPTIONS 



153 



SECTION 2. ORIGINAL DESCRIPTIONS OF EOCENE 

 TITANOTHERES 



FIVE RULES FOE DETERMINING THE NAMES OF 

 TITANOTHERES 



The systematic revision of the Eocene and Oligo- 

 cene titanotheres was begun in 1900 by the author 

 with the cooperation of W. K. Gregory and has been 

 continued up to the day of the deUvery of the manu- 

 script of this volume to the Geological Survey. The 

 great difficulties and the labor involved in determin- 

 ing the correct prior names for the genera and species 

 have been due to the imperfection of the fossil types, 

 to loose methods of description and comparison, and 

 to the mingling as cotypes of animals belonging to dif- 

 ferent species or even to different genera. 



Experience has shown that the following five rules 

 are absolutely necessary for future vertebrate paleon- 

 tologic work. 



Rule 1. Accept the "law of priority," as defined by the 

 International Committee on Nomenclature. 



In this revision the author has accepted as authori- 

 tative the rules of nomenclature based upon the "law 

 of priority," as defined by the "Code" of the Ameri- 

 can Ornithologists' Union and by the recommenda- 

 tions of the committee on nomenclature of the Twelfth 

 International Congress of Zoology. Special acknowl- 

 egments a,re due to the eminent authority Dr. J. A. 

 Allen for frequent aid in deciding troublesome prob- 

 lems of nomenclature. 



Rule 2. Determine the geologic level and characters of the 

 type, as the starting point of monographic inquiry. 



Experience teaches that the characters of the holo- 

 type specimen and the geologic level on which it was 

 found afford the permanent facts to which all questions 

 of nomenclature must be referred as the basis of mono- 

 graphic investigation. 



Rule 3. Avoid confusion of characters of th& type and cotype 

 or paratype. 



All the early systematic work on the titanotheres 

 was done without regard to precise discrimination 

 between the certain or permanent nomenclatural 

 value of the holotype specimen and the uncertain 

 value of "specific" characters based on cotype, para- 

 type, and neotype specimens. 



For example, take the case of the classic species 

 Palaeosyops paludosus Leidy. Leidy used as types 

 the very fragmentary teeth from the lower levels of 

 Bridger B, which first came into his hands; he later 

 erroneously associated with these fragments, practi- 

 cally as cotypes, other more complete specimens, which 

 are now known to belong to two or three different 

 species from higher geologic levels. Subsequently 

 Leidy himself. Cope, Marsh, Scott, Osborn, and Earle 

 all accepted Leidy's erroneous associations, and P. 

 paludosus came to be known by certain of its falsely 

 associated cotype and paratype characters instead of 

 by its true type characters. 



101959— 29— VOL 1 13 



Thus the entire nomenclature of the subject became 

 a mass of confusion, and the difficulties encountered in 

 clearing it up have been almost insuperable. 



The rule is that specific definitions must be based on 

 holotypes only, unless there is absolutely no possibility 

 of doubt that the associated types are from the same 

 geologic level and belong to the same species. 



Rule 4. Distinguish the different values and kinds of types. 



The use of the terms type (or holotype), cotype, 

 paratype, lectotype, hypotype, neotype has been dis- 

 cussed critically by Oldfield Thomas (1893.1, p. 241), 

 by Schuchert (1905.1, pp. 9-14), and by Osborn 

 (1918.473). The distinctions indicated below should 

 be noted. 



Type, individual, or holotype. — -A holotype is a 

 particular individual specimen "deliberately selected 

 by the author of a species; or it may be the only 

 example of a species known at the time of original 

 publication. A holotype, therefore, is always a single 

 individual but may embrace one or more parts, as the 

 skin, skeleton, or other portions." (Schuchert, op. 

 cit.) The holotype must usually be determined from 

 the original description. 



Cotype, coordinate or equivalent type. — The term co- 

 type is applied to specimens when an author's type 

 description refers to remains of two or more individuals 

 without selecting or distinguishing one as the holotype, 

 so that all appear to be equally identified with the 

 specific name given. 



Lectotype. — "Where the origina' diagnosis is with- 

 out illustrations or is accompanied by figures based on 

 two or more specimens, the first subsequent author is 

 at liberty to select from these cotypes a type for the 

 old species, adhering, so far as can be ascertained, to 

 the intention of the original author. Such a type 

 specimen is to be designated a lectotype ( = a chosen 

 type)." (Schuchert, idem.) The practice of Osborn 

 as to lectotypes in paleontology is either (a) to select 

 the first individual specimen named by the original 

 author, because the second individual specimen may 

 belong to a distinct species, or (&) to select the speci- 

 men to which the specific name obviously refers — 

 for example, Cope's Menodus angustigenis. 



Hypotype and plesiotype. — As shown by Schuchert 

 (idem), the terms hypotype and plesiotype have been 

 used in two different senses to cover "supplementary 

 types." They may well be dropped. 



Neotype. — A neotype is defined by Schuchert (idem) 

 as a [new] "supplementary type selected by an [a sub- 

 sequent] author, on which a species is to rest because 

 of the loss of the original type, or where the original 

 material still extant is so poor or fragmentary that from 

 it the characters of the species can not be determined 

 with certainty." Great care must be taken that the 

 neotype comes from the same geologic level as the 

 type. 



