A RODENT AND A PECCARY FROM THE CENOZOIC OF COLOMBIA

by R. A. STIRTON Museum of Paleontology, University of California. A RODENT AND A PECCARY FROM THE CENOZOIC OF COLOMBIA (1)

(LAMINA LXXXIII)

RESUMEN

Se estudian restos de mamíferos del Cenozoico colombiano descubiertos por el Dr. José Royo y Górilez, del Servicio Geoló- gico Nacional. Se trata primeramente de un premolar superior y un incisivo de un roedor histricomorfo de la superfamilia Ca- vioidea y familia Dinomyidae; es una especie nueva, Gyriabrus? royoi Stirton, de edad miocena superior a pliocena inferior pro- cedente del Km. 35 de la carretera de Tolú, Municipio de Sincelejo, Departamento de Bolívar. Se estudia luego la parte posterior de una mandíbula inferior izquierda con el último molar de un pecarí referible a la familia Tayassuidae y a un género y especie nuevos, Selenogonus nariñoensis Stirton, encontrada cerca de la Cocha Verde, carretera de Túquerres, Municipio de Tangua, Departa- mento de Nariño, correspondiente al Plioceno superior o al Pleis- toceno.

My attention was directed to two interesting fossil vertebrate spe- cimens when I was in Bogotá as a Guggénheim fellow in september 1944. These were obtained in the field by Dr. José Royo y Gómez, geologist for the Ministerio de Minas y Petróleos, Servicio Geológico Nacional de Co- lombia. I am indebted to Dr. Alejandro del Río, director of the Servicio Geológico Nacional and to Dr. Royo y Gómez for the privilege of describ- ing these specimens. The locality information was supplied by Dr. Royo y Gómez and the illustrations were made by Owen J. Poe.

DINOMYIDAE Alston

One specimen is represented by an upper premolar and an incisor of a hystricomorph rodent. It belongs to a group of hypodont rodent that has had varied family assignments depending on the author and the date of publication. Agreement on the classification of the suborder Hystri- comorpha has not yet been attained, but until we have a clearer unders- tanding of the group as a whole and the superfamily Cavioidea in parti- cular, I favor including the following genera under the family Dinomyi- dae : Dinomys, Clidomys, Spirodontomys, Speoxenus, Tetrastylomys, Pen- tastylomys, Carlesia, Telicomys, Eumegamys, Isostylomys, Rusconia, Dia- phoromys, Protomegamys, Pseudosigmomys, Tetrastylopsis, Phoberomys, Euphilus, Tetrastylus, Gyriabrus, Protomarchus, Disclomys, Eusigmomys, Simplimus, Telodontomys, Neoepiblema, Dabbenea, Elasmodoutomys, Amblyrhiza, Quemisia, Morenella ánd Heptaxodon.

1.—University of California Studies in Paleontology in cooperation with the "Servicio Geológico de Colombia".—Contribution N9 1. 320 ESTUDIOS GEOLOGICOS

Many of these genera have been included in Kraglievich's families Eumegamyidae, Neoepiblemidae and Potamarchidae by Argentine paleon- tologists (Kraglievich 1926, 1930, 1931, 1932 and 1934; Rusconi 1934 a-b). Earlier Rovereto (1914) placed the genera Megamys (1) and Te- traslylus in the family Vixcaccidae (now called Chinchillidae). Patterson (1942) in describing a new species from Brazil referred Phoberomys to the Heptaxodontidae but he did not discuss family relationships; and Simpson (1945, pp. 95-96, 212) in his admirable classification of mam- mals places Dinomys in monotypic family, the Dinomyidae, and then in- eludes most of the aboye genera in the Heptaxodontidae. Anthony (1916, 1917, 1926) after much thought on the problem followed Miller and Gid- ley (1918) in placing Dinomys, Megamys, Tetrastylus, Amblyrhiza, and Elasmodontomys in the Dinomyidae. Of course his classification, was made prior to the description of thirteen genera and about two dozen spe- cies from the Pliocene (2) of Argentine by Kraglievich and Rusconi. The evidence from these fossil forms, however, strengthens rather than detracts from the idea of including these genera in the Dinomyidae. Kra- glievich (1934, p. 101) has directed a ttention to a very close similarity between Tetrastylus, Telicomys, and Eumegamys, with Dinomys notwith- standing the absense of "paracondilos" in .Dinomys. For this reason he places Dinomys in a separate subfamily of his family Eumegamyidae. It will require more morphologic and stratigraphic information to clarify the relationships of these interesting genera. For definition of the family Dinomyidae see Miller and Gidley (1918, p. 446) and Ellerman (1940, p. 26).

?Gyriabrus royoi Stirton, n. sp.

(Lámina LXXXIII, figs. 1 y 2)

Type: Right upper premolar, P4, little worn, and upper incisor ; Type locality: Light greenish-gray fine grained sandstone ; Kilome- ter 35 carretera de Tolú, Sincelejo, Bolívar, Colombia. Age: Proba)* late Miocene with some possibility of being lower Plio- cene.

Diagnosis and description: P4 hypsodont, height of crown 17.3 mm.; open at base —not rooted; four labial and two lingual lateral grooves— extend from crown to base of tooth ; two anterior transverse inflections connect the lateral grooves on each side of tooth, forming two isolated laminae ; the three posterior dental laminae connected along lingual bor- der; anterior enamel borders of laminae thick, posterior enamel borders thin, not crenulated; second and third laminae of equal transverse length; greatest transverse width of tooth 7.0 mm.; greatest anteroposterior length 7.5 mm. There is a small oppressed area on the upper posterior border indicating a contact surface for M1.

1.—The type of Megamys (a tibia and a patella) is considered as litoptern and the rodent species referred to the genus subsequent to the original description are now assigned to different genera usted aboye (Kraglievich, 1926). 2.—I am following Simpson's (1945) age determinations since I am not familiar with the Argentine faunas. E N U allIAA 1. an. IVI1ST D• 1 11. — /LIMO ‘v7"TT 321 Upper incisor —strongly curved enamel face nearly flattened. Comparison: A high crowned premolar with lateral grooves extend- ing to the base of the rootless crown are the characters which tend to orient this specimen into the family Dinomyidae Alston, though it is much smaller than the genera (1) from the Entre Ríos fossils of the Pa- raná (Mesopotamian) here assigned to the family. The Colombian specimen cannot be accurately compared with the Argentine genera until we have detailed knowledge of the height of crowns and the lenght of the lateral grooves in those specimens. Kraglievich concludes that the number of laminae on the cheek teeth is not to be relied upen in recognizing different genera. His opinion is based on the fact that in the type lower jaw of Eumegamys paranensis Kraglievich there are six laminae on P4, four on M1 an five each on M2 and M,. If such characters are not reliable this group of rodents is in need of critica] review, because some of the genera have been identified on the number of laminae. Gyriabrus and Tetrastylus are nearer to the size of the ?G. royoi than are the other Argentine genera with which it has been compared. The species of Tetrastylus differ in being slightly larger and in possess- ing four instead of five laminae, but no upper dentitions of this gentil have been described. Gyriabrus, and especially G. holmbergi (Ameghino), is close to the Colombian species in its dental pattern of five laminae ex- cept on M1, which has four. Likewise the occlusal surface is about 3 mm longer in G. holmbergi but the width is the same. G. holmbergi differs in that the first and third laminae are about equal in transverse width and the second is the widest, whereas in ?G. royoi the second and the third laminae are of equal width and the widest on the tooth. In his description of Gyriabrus glutinatus Ameghino gives the following dimensions (the type of this genotypic species is a lower molar) "anteroposterior, 8 mi- límetros ; tranverso, 7 milímetros ; longitud en línea recta de la raíz a la corona, 27 milímetros". Though the occlusal dimensions are about the same the crown is nearly twice as high as in the Colombian specimen Gyriabrus and Tetrastylus, though larger than ?G. royoi, are nearer to it in size than the much larger Eumegamys, Isotylomys, Rusconia and related genera some of which approach it closely in their dental patterns. I am, therefore, tentatively referring this species to the genus Gy riabrus Ameghino 1891, at the same time realizing that it could be as do se or even more closely related to such genera as Discolomys or Potamar chus. The smaller size of ?G. royoi may be due to its being older geologi cally than those from Argentine or it could be a small species of about the same age. More information from the Sincelejo locality may reveal its exact age. TAYASSUIDAE The second specimen is peccary. Unfortunately only the posterior portion of a left lower jaw from this peculiar animal is preserved. It was found by some workmen who were -employed in highway construction. Apparently no other vertebrate fossils were seen in that vecinity. This

1.—Recently Simpson (1945) has referred these genera to the Pliocene, 322 ESTUDIOS GEOLOGICOS

mandibular fragment was figured by Dr. Royo y Gómez (1942, p. 126, fig. 29) in his report ora the economic geology of the Nariño y Alto Putu- mayo area.

Selenogonus (1) nariñoensis Stirton, n. gen. and n. sp. (Lámina LXXXIII, fig. 3)

Type: Posterior part of left mandible with hypolophid and hypoco, nulid of 1VIa well preserved.

Type locality: Dark green fine-grained sandstone, Cocha Verde, Ca- rretera de Túquerres-Tangua, Nariño, Colombia. (See Royo y Gómez, 1942, p. 115, muestra 927; p. 118, muestras 930, 931, 933). Age: Upper Pliocene or Pleistocene. Diagnosis and descriptien: Large, evidently about equal in size to Platygonus euquiensis Rusconi; masseteric fossa shallow but sharply out- lined ; internal temporal fossa deep ; depth of horizontal ramus below M3 = 55.0 mm.; ascending ramus relatively and actually higher than in other peccaries ; angle about 27 mm. below lower border of horizontal ramus, sharply hooked anteriorly. M3 hypso-brachyodont; evidently more lophiodont than in Platygo- nus ; hypoconid and entoconid moderately wtrn but were high and pointed cusps in unworn tooth ; valley between hypolophid and protolophid with- out obstruction of central conule or trefoil pattern; hypoconulid high pointed cusp with slight external position and with small basal lingual eusp ; hypoconulid would be lower than unworn hypolophid cusps ; proto- lophid about 2 mm. wider than hypolophid; tooth relatively narrow; total length = 23.0 mm. approx., width of protolophid = 14.8 mm. approx., width of hypolophid = 12.8 mm., height of entoconid = 13.0 mm. approx. Comparison: Acrogonus shows greater similarity to Platygonus than to the other genera of peccaries. This is displayed in its narrow lophiodont tooth and in the depth of the angle in the lower jaw. The M3 differs from Platygonus, however, in its higher crown and opera valleys between the lophids. Though the angle is accentuated in Platygonus (Rusconi 1930) it is not hooked anteriorly as in Acrogonus. A like development my be seen in Hippopotamus amphibius Linnaens the living hippopotamus and in the entelodonts Archaeotherium •waWessi Sinclair, Megachoerus, zygómaticus Troxell and Pelonax raniosus (Cope) from the White River Oligocene of North America. In Merycopotamus dissimilis (Falconer and Cantley), the late Pliocene and Pleistocene anthracotheroid from India, there is some evidence of this structure but it is not hooked anteriorly. Possibly muscle attachment areas of this kj.nd could be correlated with a semiaquatic adaptation but this might be difficult to prove. Berkeley, Cal., January, 1946.

1:—Seleno, crE;191v1 crescent; gonus, y CJVIY angle. EN COLOMBIA—Tomo VII 323

LITERATURE CITED

Anthony, H. E. 1916. Preliminary report of fossils mammals from Porto Rico with descriptions of a new genus of ground sloth and two new ge- nera of hystricomorph rodents. Ann. New York Acad. Sci., vol. 27, pp. 199-203, pls. 13-14. 1917. New fossil rodent from Porto Rico, with additional notes on Elasmodontomys obliquus Anthony and Heteropsomys in- sulans Anthony. Bull. Amer. Mus. Nat. Hist., vol. 37, pp. 183-189, pl. 5, 1920. New Mammals from Jamaica.•—Ibid., vol. 42, pp. 469-475, pl. 33.

Ameghino, F. 1891. Mamíferas y aves fósiles argentinos. Especies nuevas, adi- ciones y correcciones. Revista Argentina Hist. Nat., vol. 1, pt. 4, pp. 246-247.

Ellerman, J. R. 1940. The families and genera of living rodent. British Mus. Lon- don, vol. 1, pp. 170-173.

Kraglievich, L. 1926. Los grandes roedores terciarios de la Argentina y sus rela- ciones con ciertos géneros pleistocenos de las Antillas. An. Mus. Nac. Hist. Nat. Buenos Aires, vol. 34, pp. 121-135, pls. 1-7. 1930. Descripción de un interesante roedor eumegámido descubier- to en. el Uruguay : Gyriabrus Teisseirei n. sp. Rev. Soc. Ami- gos Arqueol., Montevideo, vol. 4, pp. 219-244, one fig. 1931. Tres comunicaciones 'paleontológicas. a) Nuevos géneros de roedores eumegámidos. Physis, vol. 10, pp. 392-394. 1932. Diagnosis de nuevos géneros y especies de roedores cávidos y eumegámidos fósiles de la Argentina. An. Soc. Cien. Argentina, Buenos Aires, vol. 114, pp. 179-181, 211-237, figs. 2-9. 1934, La antigüedad pliocena de las faunas de Monte Hermoso y Cha- padmalal, deducidas de su comparación con las que la prece- dieron y sucedieron. Imprenta. El. Siglo Ilustrado, San José 938, Montevideo, pp. 71-73. Miller, G. S. and Gidley, J. W. 1918. Synopsis 'of the supergeneric groups of rodents. Jour. Wash. Acad. Sci., vol. 8, p. 446. 324 ESTUDIOS GEOLOGICOS

Patterson, B. 1942. Two tertiary mammals from northern South America. Amer. Mus. Novitates, no. 1173, pp. 1-2, fig. 1. Rovereto, C. 1914. Los estratos araucanos y sus fósiles. An. Mus. Nac. Hist. Nat. Buenos Aires, vol. 25, pp. 35-36, 224, figs. 10-12, 92. Royo y Gómez, J. 1942. Compilación de los Estudios Geológicos Oficiales en Colom- bia. Datos para la Geología Económica de Nariño y Alto Pu- tumayo. Ministerio de Minas y Petróleos.—Serv. Geol. Nac. vol. 5, pp. 115, 118, 126, fig. 29. Rusconi, C. 1930. Las especies fósiles argentinas de pecaríes. An. Mus. Nac. Hist. Nat., Buenos Aires, vol. 36, pp. 121-241, figs. 1-32, pls. 1-18. 1934 a. Algunos fósiles terciarios de la gobernación de la Pampa Ar- gentina. Rey. Chilena Hist. Nat., vol. 38, pp. 104-107, fig. 25. 1934 b. Séptima noticia sobre los vertebrados fósiles del Puelchense de Villa Ballester. An. Soc. Cien. Argentina, vol. 117, pp. 179- 180, fig. 1. Simpson, G. G. 1945. The principie of classification and a classification of mam- mals. Bull. Amer. Mus. Nat. Hist., vol. 85, pp. 95-96, 212.

EXPLANATION OF PLATE

(Lámina LXXXIII)

Fig. 1.—?Gyriabrus royoi Stirton, n. sp. Type, right P4 little worn, twice natural size. Sincelejo, Bolívar, Colombia. a. Labial; b. occlusal ; e. lingual views. Fig. 2.—?Gyriabrus royoi Stirton, n. sp. Type, upper incisor twice natu- ral size. a. Labial view ; b. crossection. Fig. 3.—Selenogonus nariñoensis Stirton, n. gen. and n. sp. Type, poste- rior portion of left mandible. Carretera de Túquerres-Tangua, Na- riño, Colombia, a. Occlusal view of posterior half of M3, natural size ; b. lateral view of mandibular fragment, two-thirds natural size.

COMPIL. ESTE]. GECL. OF. EN COLOM3IA, T. VII.—CENOZOICO DE COLOMBIA LAMINA LXXXIII.

c

Fi,g.1

Ftg 3

a

Sect Loa A-13

Un roedor y un pecarí del Cenozoico de Colombia.

BOGOTA-IMP. NAL.-1946