A HISTORY OF THE CLASSIFICATION OF THE AMPHIBIA, WITH ESPECIAL REFERENCE TO THE SPECIES FROM THE COAL MEASURES.

It has been necessary, in the course of the present study, to review thoroughly the classifications which have been proposed for the group. A classification of some sort is necessary for the proper grouping of the species which have been recovered from the Coal Measures deposits of this continent, and my reason for publishing this relatively dry material is that the classifications formerly proposed (469), as well as the one here given, may have a proper historical background.

The review of the proposed systems of classification has been much facilitated by the discovery, in the University of Chicago, of some notes by the late Dr. George Baur on the "Stegocephali." The notes were not discovered until after the literature had been pretty thoroughly covered, and it was a source of some gratification, on comparing notes with those of Dr. Baur, to find but few omissions. Whether Dr. Baur had ever contemplated a work on the Stegocephala or not I have been unable to learn, but it is certain that he carefully and laboriously went through the literature on the subject and copied by hand the classifications of each author from 1842 to 1895, together with other notes of interest on the structure, distribution, and phylogeny, including many tracings. The classifications given below are taken, in part, from his notes, although all references have been verified with the original sources.

The first attempt to combine in classification the knowledge of the extinct and recent amphibians was made by Johannes Jacob von Tschudi in 1839 (574). Previous to that time Goldfuss (295) and von Meyer (418) had described various species of salamanders and frogs from the Tertiary deposits of Switzerland, and these Tschudi considered in his following classification:

A. RanÆ.
a. HylÆ.
b. Cystignathi.
c. RanÆ.
d. Ceratophrydes.
e. Bombinatores.
f. Bufones.
g. PipÆ.
B. CoeciliÆ.
a. CoeciliÆ.
C. SalamandrinÆ.
a. Pleurodeles.
b. SalamandrÆ.
c. Tritones.
d. Tritonides.
D. ProtoideÆ.

Although the remains of Mastodonsaurus had been known and widely commented on for several years before Tschudi proposed this scheme, he does not include this genus in his classification of the Amphibia, for the reason that for nearly a quarter of a century after the discovery of the labyrinthodonts they were regarded as reptiles, even so eminent an authority as von Meyer (423) including them in his "System der fossilen Saurier." The view that the labyrinthodonts were reptiles was at times disputed, but no one seemed to pay any attention to the argument of Quenstedt in 1850 that "Die Mastodonsaurier im grÜnen Keupersandstein WÜrtemburgs sind Batrachier" (527), nor to the contention of Vogt (581) in 1854 that "Archegosaurus und alle Labyrinthodonten sind Amphibien, nicht Reptilien."

In 1842 von Meyer (420) proposed to include all the early forms allied to the Mastodonsaurus in the "Labyrinthodontes." His definition of the group follows:

Labyrinthodontes: Saurier deren Zahn-Struktur jener Ähnlich ist, welche in den nach prismatischer Art gebauten SÄugethier-ZÄhnen wahrgenommen wird, u.s.w.

Three years later von Meyer (423) proposed his "System der fossilen Saurier," where the extinct Amphibia are treated as follows:

No other classification was proposed for the extinct Amphibia for 15 years, when Owen (512) in 1859 proposed the new order Ganocephala and retained von Meyer's Labyrinthodontes under Labyrinthodontia. Owen's classification is as follows:

Class Reptilia.
Order I. Ganocephala.
Genera: Archegosaurus, Dendrerpeton, Raniceps.
Order II. Labyrinthodontia.
Genera: Mastodonsaurus, Anisopus, Trematosaurus , Metopias, Capitosaurus,
Zygosaurus, Xestorrhytias.

In his Paleontology published in 1861, Owen gives the same classification, but adds new genera.

Huxley in 1863 (332) did not accept Owen's Ganocephala, but instead proposed the following:

Labyrinthodontia.
A. Archegosauria. Archegosaurus, Pholidogaster.
B. Mastodonsauria. Mastodonsaurus, Labyrinthodon, Capitosaurus, Trematosaurus.

In the same year Dawson proposed (208) the term Microsauria to include the genera Hylonomus, Dendrerpeton, and Hylerpeton, all known from the Carboniferous rocks of Nova Scotia. Two years later Cope proposed the new order Xenorhachia (105) for the reception of the form Amphibamus grandiceps from the Coal Measures of Illinois. He gave as the characters of this order cartilaginous vertebrÆ and the absence of ribs.

In 1866 Owen proposed (516) the most elaborate and comprehensive scheme of classification which had thus far been offered. His classification is as follows:

Subclass Dipnoa.
Order Ganocephala (extinct). Genera: Archegosaurus, Dendrerpeton, etc.
Order Labyrinthodontia. Genera: Labyrinthodon, Rhombopholis , etc.
Order Batrachia.
Suborder Ophiomorpha. Family: CoecilidÆ.
Suborder Ichthyomorpha. Family: ProteidÆ, SalamandridÆ.
Suborder Theriomorpha (Anura).
Family 1. Aglossa.
Family 2. RanidÆ.
Family 3. HylidÆ.
Family 4. BufonidÆ.

Haeckel the same year proposed (312) an entirely different scheme of classification nd in some respects more acceptable than Owen's. Haeckel's classification is as follows:

Class—Amphibia.
Subclass I. Phractamphibia.
Ordnung i. Ganocephala.
Genera: Archegosaurus, Dendrerpeton, Raniceps.
Ordnung 2. Labyrinthodonta.
Genera: Baphetes, Zygosaurus, Mastodonsaurus, Trematosaurus, Capitosaurus.
Ordnung 3. Peromela.
Subclass II. Lissamphibia.
Ordnung i. Socobranchia.
Genera: Siren, Proteus, Menobranchus, etc.
Ordnung 2. Sozura (Caudata).
Genera: Cryptobranchus, Triton, Salamandra.
Ordnung 3. Anura (Ecaudata).
Families: Aglossa, BufonidÆ, RanidÆ.

This classification is further elaborated in the edition of 1895.

Cope in 1868 proposed (110) the scheme of classification which was in use for some time, although it has since suffered some change. His classification follows:

Batrachia.
Order 1. Trachystoma.
Order 2. Proteida.
Order 3. Urodela.
Order 4. Gymnophiona.
Order 5. Stegocephali.
Suborder Xenorhachia.
Amphibamus grandiceps Cope.
Suborder Microsauria.
Genera: Pelion Wyman, Hylonomus Dawson, Pariostegus Cope, Dendrerpeton
Owen, Hylerpeton Owen, Brachydectes Cope, Sauropleura Cope,
Œstocephalus Cope, Molgophis Cope.
Suborder Labyrinthodontia.
Genera: Dictyocephalus Leidy, Centemodon Lea, Baphetes Owen, Eupelor Cope.

Huxley in 1869 proposed (335) the following classification, which does not differ essentially from that proposed in 1863:

Amphibia.
Order 1. Urodela.
Order 2. Batrachia.
Order 3. Gymnophiona.
Order 4. Labyrinthodontia.
Suborder Archegosauria.
Suborder Mastodonsauria.

The next classification of the extinct Amphibia of any importance was that devised by the committee (450) for the British Association in 1874. This committee was formed of Huxley, Harkness, Henry Woodward, Thompson, and Brigg, with Miall as secretary. This classification is, however, too cumbersome and has never come into general use, and indeed none but English authors have paid it a great deal of attention, although the contribution was a valuable one. The group Aistopoda, which was the ninth group proposed by the committee, has generally been accepted as the group represented by the snake-like forms. The committee's classification follows:

Labyrinthodontia.
Section I. Euglypta.
Genera: Mastodonsaurus, Jaeger; Capitosaurus, MÜnst.; Pachygonia, Huxley; Trematosaurus,
Braun; Gonioglyptus, Huxley; Metopias, von Meyer; Labyrinthodon, Owen;
Diadetognathus, Miall; Dasyceps, Huxley; Anthracosaurus, Huxley.
Section II. Brachyopina.
Genera: Brachyops, Owen; Micropholis, Huxley; Rhinosaurus, Waldheim; Bothriceps, Huxley.
Section III. Chauliodonta.
Genera: Loxomma, Huxley; Zygosaurus, Eich.; Melosaurus, Meyer.
Section IV. ArthroÖdonta.
Genera: Batrachiderpeton, Hancock and Atthey; Pteroplax, Hancock and Atthey.
Section V. An uncharacterized group.
Genera: Pholidogaster, Huxley; Ichthyerpeton, Huxley; Pholiderpeton, Huxley.
Section VI. Archegosauria, von Meyer.
Genera: Archegosaurus, Goldfuss.
Section VII. Heleothrepta.
Genera: Lepterpeton, Huxley.
Section VIII. Nectridea.
Genera: Urocordylus, Huxley; Keraterpeton, Huxley.
Section IX. Aistopoda.
Genera: Ophiderpeton, Huxley; Dolichosoma, Huxley.
Section X. Microsauria, Dawson.
Genera: Dendrerpeton, Owen; Hylonomus, Dawson; Hylerpeton, Owen.

The schemes of classification used for the next 10 years did not depart in any appreciable degree from those already given.

In 1875 Cope, in his Check-list of North American Batrachia and Reptilia (120), with a systematic list of the higher groups, published the following classification as being "adopted provisionally by the Smithsonian Institution":

Class Batrachia.
Order Anura. (Anura, DumÉril; Salientia, Merrem, Gray.)
Raniformia. (Raniformia, Cope, Nat. Hist. Rev., V, 114, 1865.)
Families: RanidÆ, ColostheidÆ.
Firmisternia. (Bufonoid Raniformia, Cope, Jour. Acad. Nat. Sci., Philadelphia, n.s., VI,
190, 1867.)
Families: DendrobatidÆ, PhryniscidÆ, EngystomidÆ, BreviceptidÆ.
Gastrechmia. (Gastrechmia, Cope, Jour. Acad. Nat. Sci., Philadelphia, n.s., VI, 198, 1867.)
Family: HemisidÆ.
Bufoniformia. (Bufoniformia, DumÉril et Bibron, partim; Cope, partim.)
Families: RhinophrynidÆ, BufonidÆ, BatrachophrynidÆ.
Aglossa.
Family: PipidÆ.
Odontaglossa.
Family: DactylethridÆ.
Arcifera. (Arcifera, Cope, N. H. Rev., V, 104, 1865.)
Families: CystignathidÆ, HemiphractidÆ, HylidÆ, ScaphiopidÆ, PelodytidÆ, AsterophrydidÆ, DiscoglossidÆ.
Order Stegocephali. (Stegocephali Cope, Proc. Acad. Nat. Sci., Philadelphia, 1868, 209.)
Labyrinthodontia.
Families: BaphetidÆ Cope, AnthracosauridÆ Cope.
Ganocephala.
Family: ColosteidÆ Cope.
Microsauria.
Families: PhlegethontiidÆ Cope, MolgophidÆ Cope, PtyoniidÆ Cope, TuditanidÆ Cope,
PeliontidÆ Cope.
Order Gymnophiona. (Gymnophiona MÜller.)
Family: CoeciliidÆ Gray, 1850.
Order Urodela.
Families: PleurodelidÆ Gray, 1858; SalamandridÆ: Gray, 1858; HynobiidÆ Cope, 1866;
DesmognathidÆ Cope, 1866; ThoriidÆ Cope, 1869; PlethodontidÆ Cope,
1866; AmblystomidÆ Cope, 1866; MenopomidÆ (ProtonopsidÆ Gray,
1850), AmphiumidÆ Cope, 1866; CocytinidÆ Cope.
Order Proteida.
Family: ProteidÆ Gray, 1850.
Order Trachystomata.
Family: SirenidÆ Gray, 1850.

In 1885 Cope proposed 2 new orders, which he arranges with the other orders already known, as follows:

The new order Rachitomi was to include forms like Eryops and the new order Embolomeri was to include forms like Cricotus; the other orders were as they had been given before.

Zittel in 1888 proposed (642) the next classification of any note in his "Handbuch der Paleontologie," where it stands as follows:

Classe Amphibia.
Ordnung 1. Stegocephali.
Unterordnung 1. Lepospondyli.
Familie 1. BranchiosauridÆ Fritsch.
" 2. Microsauria Dawson.
" 3. Aistopoda Miall.
Unterordnung 2. Temnospondyli.
Genera: Archegosaurus, Eryops, etc.
Unterordnung 3. Stereospondyli.
Familie 1. Gastrolepidoti.
" 2. Labyrinthodonta.
Ordnung 2. CoeciliÆ.
Ordnung 3. Urodela.
Unterordnung 1. Ichthyoidea.
Familie 1. Phanerobranchia.
" 2. Cryptobranchia.
Unterordnung 2. Salamandrina.
Ordnung 4. Anura.
Unterordnung 1. Phaneroglossa.
Familie 1. RanidÆ.
" 2. BufonidÆ.
" 3. CystignathidÆ Cope.
" 4. PelobatidÆ Boul.
" 5. DiscoglossidÆ Cope.
" 6. PalÆobatrachidÆ Cope.

Lydekker (393) in the next year proposed a system of classification which did not depart widely from that proposed (450) by the committee of the British Association for 1874. Lydekker's classification is as follows:

Class Amphibia.
Order I. Labyrinthodontia.
Suborder 1. Branchiosauria.
Family ProtritonidÆ.
" ApateonidÆ.
Suborder 2. Aistopoda.
Family DolichosomatidÆ.
Suborder 3. Microsauria.
Family UrocordylidÆ.
" LimnerpetidÆ.
" HyloplesionidÆ.
" MicrobrachidÆ.
Suborder 4. Labyrinthodontia vera.
Family ArchegosauridÆ.
" DiplospondylidÆ.
" NyraniidÆ.
" DendrerpetidÆ.
" AnthracosauridÆ.
" MastodonsauridÆ.
Uncertain family, Eosaurus.
Order II. Apoda.
Order III. Caudata.
Family HylÆobatrachidÆ.
" SirenidÆ.
" ProteidÆ.
" AmphiumidÆ.
" SalamandridÆ.
Order IV. Ecaudata.
Family DiscoglossidÆ.
" PelobatidÆ.
" PalÆobatrachidÆ.
" CystignathidÆ.
" RanidÆ.

In 1890 DÖederlein proposed a scheme of classification which is notable on account of the peculiar relations which it expresses between the groups relations which, in reality, do not exist. His classification is as follows:

Class Amphibia.
Ordnung I. Stegocephali.
A. Microsauria.
Unterordnung 1. Branchiosauri.
Genera: Branchiosaurus, Dawsonia, Melanerpeton, Pelosaurus.
Unterordnung 2. Sauromorphi.
Familie 1. HylonomidÆ.
" 2. NectridÆ.
" 3. AistopodidÆ.
B. Ganocephala.
Unterordnung 1. Rhachitomi.
" 2. Embolomeri.
" 3. Labyrinthodontia.
Ordnung II. Urodela.
Ordnung III. Gymnophiona.
Ordnung IV. Anura.

In 1890 Lydekker used the same classification, with minor changes, which he had used in his Paleontology. Credner, who wrote at about the same time (193), followed Zittel's classification. Zittel in 1895 merely repeated his former classification. In 1898 appeared Smith Woodward's Paleontology, where the following scheme is adopted:

Class Batrachia.
Order I. Stegocephalia. Order II. Gymnophiona.
Suborder 1. Branchiosauria. Order III. Caudata.
" 2. Aistopoda. Order IV. Ecaudata.
" 3. Microsauria.
" 4. Labyrinthodontia.

Hay's Catalogue of Fossil Vertebrata of North America contains the next scheme for the classification of the Amphibia which pays especial attention to the extinct forms. His classification is as follows:

Class Batrachia Macartney, 1802.
Order Stegocephali Cope, 1868.
Suborder Microsauria Dawson, 1863.
Family ProtritonidÆ Lydekker, 1889.
Genera: Amphibamus Cope, Pelion Wym.
Family MolgophidÆ Cope, 1875.
Genera: Phlegethontia Cope, Molgophis Cope.
Family HylonomidÆ Fritsch, 1883.
Genera: Hylonomus Dawson, Smilerpeton Dawson, Hylerpeton Owen, Fritschia
Dawson; Brachydectes Cope.
Family PtyoniidÆ Cope, 1875.
Genera: Keraterpeton Huxley, Œstocephalus Cope, Ptyonius Cope,
Ctenerpeton Cope.
Family TuditanidÆ Cope, 1875.
Genera: Tuditanus Cope, Cocytinus Cope.
Family DiplocaulidÆ Cope, 1881.
Genus: Diplocaulus Cope.
Lepospondylous Genera of uncertain position: Amblyodon Dawson, Hyphasma
Cope, Eurythorax Cope, Thyrsidium Cope, Pleuroptyx Cope,
Cercariomorphus Cope.
Suborder Apoecospondyli Hay, 1902.
Family DendrerpetontidÆ Fritsch, 1889.
Genera: Dendrerpeton Owen, Baphetes Owen, Platystegos Dawson.
Family SauropleuridÆ Hay, 1902.
Genera: Sauropleura Cope, Leptophractus Cope.
Family ArchegosauridÆ.
Genera: Trimerorhachis Cope, Dissorophus Cope.
Family CricotidÆ Cope, 1884.
Genera: Cricotus Cope.
Family AnthracosauridÆ.
Genus: Eosaurus Marsh.
Family EryopidÆ Cope, 1882.
Genera: Eryops Cope, Ichthycanthus Cope, Zatrachys Cope, Anisodexis Cope,
Acheloma Cope.
Family MastodonsauridÆ Huxley, 1863.
Genera: Mastodonsaurus Jaeger, Eupelor Cope, Pariostegus Cope, Dictyocephalus
Leidy.
Order Urodela.
Genera: Scapherpeton Cope, Hemitrypus Cope.
Order Salientia Laurenti, 1768.
Family RanidÆ.
Genera: Rana LinnÉ, Eobatrachus Marsh.

This classification given by Hay is only for the forms which occur in North America.