Rhinotitan orientalis Yanovskaya, 1957

Mihlbachler, Matthew C., 2008, Species Taxonomy, Phylogeny, and Biogeography of the Brontotheriidae (Mammalia: Perissodactyla), Bulletin of the American Museum of Natural History 311 (1), pp. 1-475 : 351-353

Rhinotitan orientalis Yanovskaya, 1957

HOLOTYPE: The holotype consists of several fragments assigned to PIN 858 that are all from a single individual according to Yanovskaya (1957): 88, part of a left M2; 35, canine fragment; 36, canine fragment; 80–81, left m3 fragment; 82, trigonid of left molar; 78, talonid of right molar; 83, trigonid of left molar; 79, talonid of right molar; 85, fragment of right P3 or P4 and trigonid of right m1; 84, right p3, 86, right p3 trigonid; 39, part of right lower canine; 24, upper incisor; 71, lower incisor; 99, right semilunar bone.

TYPE LOCALITY: Artyom mammal locality, coalmine north of Vladivostok in eastern Russia in strata termed the Uglov Svita (‘‘coal formation’’) ( Russell and Zhai, 1987).

AGE: Middle Eocene (Sharamurunian land mammal ‘‘age’’) (Lucas et al, 2004).

DETERMINATION: Nomen dubium, material is too fragmentary to adequately compare to other species.

REMARKS

Yanovskaya (1957) named Rhinotitan orientalis from isolated teeth and tooth fragments. Some of the more diagnostically useful fragments are seen in fig. 179, including a portion of an upper premolar (fig. 179a), a complete right p3 crown (fig. 179b), a lower incisor (fig. 179c) and an upper incisor (fig. 179d). Lucas et al. (2004) argued that this species is a nomen dubium. The small incisors and the well-developed premolar hypocone contrasts very strongly with true Rhinotitan , The tiny, semiwedge-shaped lower incisor and globular upper incisor suggest a species similar to Parabrontops , Eubrontotherium , or Dianotitan . The p3 lacks a metaconid, a condition consistent with Parabrontops gobiensis and Eubrontotherium clarnoensis . (The p3 is unknown for Dianotitan ). In short, R. orientalis is a dubious species and the brontothere material from the Artyom locality could represent one (or more) of a number of brontotheres of middle or late Eocene age.

‘‘ Eotitanops ?’’ dayi Dehm and Oettingen-Spielberg, 1958

HOLOTYPE: A right partial maxilla with the broken crowns of M2 and M 3 in the Institute für Paläontologie und Historische Geologie, München (see plate 2, fig. 3 in Dehm and Oettingen-Spielberg [1958]).

TYPE LOCALITY: Kuldana Formation, Ganda Kas Area (‘‘locality 25’’), red-purple and greenish marls, Pakistan.

AGE: Middle Eocene.

REFERRED SPECIMENS: (From the same locality as the holotype, all in the München collection. The following figure references refer to Dehm and Oettingen-Spielberg [1958: pl. 2: figs. 4–9]) partial M3 (fig. 4) ; partial left M1–M2 (fig. 5), partial right left M1–M3 (fig. 6); m3 fragment (fig. 7); mandible fragment with partial incisors and canine; (fig. 8); a mandible fragment with canine and anterior premolar roots (fig. 9); (from H-GSP locality 68 from the Kuldana Formation , near the village of Ganda Kas) H-GSP 573, a partial right maxilla with lingual parts of M1 and M2; H-GSP 577, a partial right M1; H-GSP 1592, a partial left M2; (from the Chorlakki locality in the Mami Khel Formation , Kohat District, Northwest Frontier Province of Pakistan) GSP-UM 104, a partial left M3; GSP-UM 155, left P3; GSP-UM 156 upper molar fragment; GSP-UM 1642 partial left P3?; GSP-UM 1526; partial left protocone; GSP-UM 1692, partial right paracone.

DETERMINATION: Problematic taxon, this species seems valid, although it probably does not belong to Eotitanops . The material is too fragmentary to provide a thorough description or adequate diagnosis.

REMARKS

Dehm and Oettingen-Spielberg (1958), West (1980), and Thewissen et al. (1987, 2001) described very fragmentary brontothere specimens that were referred to as ‘‘ Eotitanops ?’’ dayi , consisting mostly of partial upper molars from the Kuldana Formation in the Ganda Kas and Thatta areas and from the Mami Khel Formation near Chorlakki (fig. 180). ‘‘ Eotitanops ?’’ dayi is roughly intermediate in size between North American brontotheres, Eotitanops and Palaeosyops . The molars of the type specimen lack enamel. The other specimens referred to this species, which include partial molars with enamel, are of a consistent size, but given the poor nature of the material there is no way to determine whether they belong to a single species. The better tooth fragments show similarities with North American Eotitanops . For instance, M3 has a rounded lingual side. The M3s of other brontotheres have longer and flatter lingual sides, thus giving the tooth a more square appearance. Another noteworthy similarity with Eotitanops is a lower diastema of about 10 mm between the p1 and p2. However, dayi molars appear to have thinner enamel than North American Eotitanops with taller lingual cusps.

The available material seems to suggest a distinct species of brontothere, but the highly fragmentary material representing this Eotitanops -sized species is not sufficient to appropriately describe or diagnose it. Therefore, I consider this species to be problematic, but not necessarily invalid. Despite some similarities with North American Eotitanops , the material is simply too fragmentary to refer it Eotitanops or any other genus. ‘‘ Eotitanops ?’’ dayi is one of three problematic middle Eocene brontothere species of Pakistan, the others being Pakotitanops latidentatus and Mulkrajanops moghliensis .